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United States Patent 3,847,233
Glover ,   et al. November 12, 1974

TRIGGER MECHANISM FOR HAND-OPERATED POWER DEVICE PROVIDING AUTOMATIC LOCK-OFF AND MANUAL LOCK-ON OPERATION

Abstract

A trigger mechanism for a hand-operated power tool includes a trigger and a manually operable locking device which provides an automatic lock-off feature to normally lock the trigger in its inoperative position, a manual unlock feature to permit the trigger to be unlocked for movement between its inoperative and operative positions, and a manual lock-on feature to permit the trigger to be locked in its operative position. The locking device is capable of two (2) distinct modes of movement, a first mode which permits the trigger to be unlocked for movement between its inoperative and operative positions for manual control, for example, on-off operation of the power tool and a second mode which permits the trigger to be locked in its operative position for continuous operation of the tool. A positive intentional action by an operator is required to shift the locking device from its first mode of movement to its second mode of movement to prevent inadvertent movement of the locking device to its lock-on position. Furthermore, the locking device can be shifted to its second mode of movement only after the trigger is in its operative position.


Inventors: Glover; Richard Warmath (Joppa, MD), Musch; Gordon Frederick (Fork, MD), Summa; John A. (Anaheim, CA)
Assignee: The Black and Decker Manufacturing Company (Towson, MD)
Appl. No.: 05/375,160
Filed: June 29, 1973


Current U.S. Class: 173/170 ; 200/318.2; 200/43.17; 200/522
Current International Class: A01G 3/00 (20060101); A01G 3/053 (20060101); B23B 45/00 (20060101); B23B 45/02 (20060101); H01H 3/20 (20060101); H01H 3/02 (20060101); B23b 045/00 ()
Field of Search: 173/169,170 251/116 200/159R

References Cited

U.S. Patent Documents
1361431 December 1920 Wilson
1929662 October 1933 Wappat
2346778 April 1944 Mitchell
3383943 May 1968 Piber
3510099 May 1970 Crump
3564186 February 1971 Mittelstadt et al.
Primary Examiner: Leppink; James A.
Attorney, Agent or Firm: Slotnik; Joseph R. Bloom; Leonard Murphy; Edward D.

Claims



What is claimed is:

1. A trigger mechanism for a hand-operated power tool including an electric motor and an on-off switch operatively associated with the motor and normally biased off, comprising:

a trigger manually movable from a first position to a second position to actuate the switch and turn on the motor, said trigger being normally biased toward its first position; and

manually operable locking means movable in two distinct modes of movement, said locking means being normally biased toward a first position, cooperatively engageable with said trigger to prevent movement of said trigger from its first position to its second position, and movable in its first mode toward a second position wherein said trigger is manually movable to its second position to actuate the switch, said locking means being cooperatively engageable with said trigger when each is in its second position to permit said locking means to be released without movement to its first position until said trigger is allowed to return to its first position, said locking means being movable in its second mode to a third position cooperatively engageable with said trigger to lock said trigger in its second position to continuously actuate the switch and operate the motor; and

means biasing said locking means out of said third position to permit automatic disengagement of said locking means from said trigger.

2. A trigger mechanism for a hand-operated power device including a motor and a handle which supports a control operatively associated with the motor, comprising:

a trigger mounted on the handle and manually movable from a first position to a second position to actuate the control and operate the motor, said trigger being normally biased toward its first position; and

a manually operable locking device slidably mounted on the handle and movable in two distinct orientations relative to the handle, said locking device being normally biased toward a first position, cooperatively engageable with said trigger to prevent movement of said trigger from its first psition to its second position, and movable in its first orientation relative to the handle toward a second position wherein said trigger is manually movable to its second position to actuate the control, said locking device being cooperatively engageable with said trigger when each is in its second position to permit said locking device to be released without movement back to its first position until said trigger is allowed to return to its first position, said locking device being further movable in its second orientation relative to the handle to a third position cooperatively engageable with said trigger to lock said trigger in its second position to continuously actuate the control and operate the motor; and

means biasing said locking means out of said third position to permit automatic disengagement of said locking means from said trigger.

3. In a portable, hand-operated power tool including an electric motor and a handle which supports an on-off switch operatively associated with the motor and normally biased off, a trigger mechanism for operating the on-off switch, comprising:

a manually operable trigger mounted on the handle and movable from an inoperative position to an operative position to actuate the switch and turn on the motor;

integral spring means on said trigger for normally biasing said trigger toward its inoperative position;

a manually operable locking device slidably mounted on the handle for movement in first and second distinct orientations relative to the handle, said locking device being movable between a lock-off position and an unlock position in its first orientation and between its unlock position and a lock-on position in its second orientation, said locking device including first and second arms for engaging said trigger, said first arm being cooperatively engageable with said trigger when said locking device is in its lock-off position to prevent movement of said trigger from its inoperative position to its operative position, said trigger being manually movable from its inoperative position to its operative position when said locking device is moved to its unlock position to actuate the switch to control on-off operation of the motor, said second arm being cooperatively engageable with said trigger when said locking device is moved to its lock-on position to lock said trigger in its operative position to continuously actuate the switch and operate the motor; and

means for normally biasing said locking device toward its lock-off position, said first arm of said locking device being cooperatively engageable with said trigger when said trigger is moved to its operative position and said locking device is moved to its unlock position to permit said locking device to be released without movement back to its lock-off position until said trigger is allowed to return to its inoperative position.

4. In a portable, hand-operated power tool including an electric motor and a hollow handle which supports a switch operatively associated with the motor, a trigger mechanism for operating the switch, comprising:

a manually operable trigger mounted within the handle and including a finger engageable body extending through a first opening provided in the handle, said trigger being movable from an inoperative position to an operative position to actuate the switch and operate the motor, said finger engageable body including a lock-off surface and a lock-on member, said trigger being normally biased toward its inoperative position; and

a manually operable locking device slidably mounted within the handle for movement in first and second distinct orientations relative to the handle, said locking device including first and second arms extending toward said finger engageable body of said trigger, said locking device being normally biased into a lock-off position wherein said trigger first arm is in registration with said lock-off surface of said finger engageable body to prevent movement of said trigger from its inoperative position to its operative position, said locking device being movable in its first orientation from its lock-off position to an unlock position wherein said first arm is out of registration with said lock-off surface and said trigger is manually movable to its operative position to actuate the switch and operate the motor, said locking device being further movable in its second orientation between its unlock position and a lock-on position therein said second arm is cooperatively engageable with said lock-on member of said finger engageable body to lock said trigger in its inoperative position to continuously actuate the switch and operate the motor.

5. In a portable, hand-operated power tool including an electric motor and a hollow, elongated handle which supports a switch operatively associated with the motor, a trigger mechanism for operating the switch, comprising:

a manually operable trigger mounted within the handle and including a finger engageable body extending downward through a first opening provided in the handle, said finger engageable body including a lock-off surface and a lock-on member, said trigger being normally biased downward toward an inoperative position and movable upward to an operative position to actuate the switch and operate the motor; and

a manually operable locking device slidably mounted within the handle above said trigger for longitudinal and lateral movement relative to the handle, said locking device including first and second arms extending downward toward said finger engageable body of said trigger, said locking device being normally biased toward a lock-off position wherein said first arm is in registration with said lock-off surface of said finger engageable body to prevent upward movement of said trigger from its inoperative position to its operative position, said locking device being longitudinally movable in a first orientation relative to the handle from its lock-off position to an unlock position wherein said first arm is out of registration with said lock-off surface and said trigger is manually movable to its operative position to actuate the switch and operate the motor, said locking device including a rib cooperatively engageable with said lock-off surface of said finger engageable body when said locking device is in its first orientation to limit upward movement of said trigger and locate its lockon member in the path of movement of said second arm to limit longitudinal movement of said locking device in its first orientation, said locking device being shiftable laterally into a second orientation relative to the handle to move said rib out of registration with said lock-off surface of said finger engageable body to permit further upward movement of said trigger, said lock-on member being located out of the path of movement of said second arm upon further upward movement of said trigger to permit further longitudinal movement of said locking device, said locking device being movable in its second orientation to a lock-on position wherein said second arm is cooperatively engageable with said lock-on member to lock said trigger in its operative position to continuously actuate the switch and operate the motor.

6. In a portable, hand-operated power tool including an electric motor and a hollow, elongated handle which enables an operator to grip the power tool, a trigger mechanism for controlling operation of the motor, comprising:

a switch mounted within the hollow handle and operatively associated with the motor, said switch including an actuator for controlling its on-off operation;

a manually operable trigger mounted within the handle and including a portion projecting through a first opening provided in the handle to be engaged by the operator, said trigger being movable from an inoperative position to an operative position and engageable with said switch actuator upon movement to its operative position to actuate said switch and operate the motor;

integral spring means on said trigger for normally biasing said trigger toward its inoperative position;

a manually operable locking device slidably mounted for longitudinal movement relative to the handle, said locking device being shiftable laterally between first and second distinct orientations relative to the handle, said locking device being movable from a lock-off position to an unlock position in its first orientation and from its unlock position to a lock-on position in its second orientation, said locking device including a manually engageable portion extending through a second opening provided in the handle to be engaged by the operator and first and second arms for engaging said trigger, said first arm being cooperatively engageable with said trigger when said locking device is in its lock-off position to prevent movement of said trigger from its inoperative position to its operative position, said trigger being manually movable from its inoperative position to its operative position when said locking device is moved to its unlock position to operate said switch actuator to control on-off operation of the motor, said second arm being cooperatively engageable with said trigger when said locking device is moved to its lock-on position to lock said trigger in its operative position to continuously actuate said switch and operate the motor; and

means for normally biasing said locking device toward its lock-off position, said first arm of said locking device being cooperatively engageable with said trigger when said trigger is moved to its operative position and said locking device is moved to its unlock position to permit said locking device to be released without movement back to its lock-off position until said trigger is allowed to retun to its inoperative position.

7. In a portable, hand-operated power tool including an electric motor and a hollow, elongated handle which enables an operator to grip the power tool, a trigger mechanism for controlling the operation of the motor, comprising:

an on-off switch mounted within the hollow handle and operatively associated with the motor, said switch including an actuator normally biased to an off position and movable to an on position to operate the motor;

a manually operable trigger mounted within the handle and including a portion projecting through a first opening provided in the handle to be engaged by the operator, said trigger being movable from an inoperative position to an operative position and engageable with said switch upon movement to its operative position to move said switch actuator to its on position and operate the motor;

integral spring means on said trigger engaging the handle to normally bias said trigger toward its inoperative position;

a manually operable locking device slidably mounted in a track provided within the handle for longitudinal movement relative to the handle, said locking device being shiftable laterally between first and second distinct orientations relative to the handle, said locking device being movable from a lock-off position to an unlock position in its first orientation and to a lock-on position in its second orientation, said locking device including a manually engageable portion extending through a second opening provided in the handle to be engaged by the operator and first and second arms for engaging said trigger, said first arm being cooperatively engageable with said trigger when said locking device is in its lock-off position to prevent movement of said trigger from its inoperative position to its operative position, said trigger being manually movable from its inoperative position to its operative position when said locking device is moved to its unlock position to operate said switch actuator to control on-off operation of the motor, said second arm being cooperatively engageable with said trigger when said locking device is moved to its lock-on position to lock said trigger in its operative position to continuously hold said switch in its on position and operate the motor;

means for normally biasing said locking device toward its lock-off position, said first arm of said locking device being cooperatively engageable with said trigger when said trigger is moved to its operative position and said locking device is moved to its unlock position to permit said locking device to be released without movement back to its lock-off position until said trigger is allowed to return to its inoperative position;

an obstruction projecting laterally from the interior of the handle into the path of movement of said locking device for engaging one of its arms upon movement of said locking device to its unlock position to prevent further longitudinal movement of said locking device in its first orientation, said arm being released from said obstruction upon lateral movement of said locking device from its unlock position into its second orientation to permit said locking device to be moved to its lock-on position; and

a cam surface projecting laterally from the interior of the handle on the opposite side of said locking device from said obstruction for engaging said locking device upon release of said trigger to drive said locking device laterally from its second orientation to its first orientation during return movement of said locking device from its unlock position to its lock-off position.

8. In a portable, hand-operated power tool including an electric motor and a hollow, elongated handle which enables an operator to grip the power tool, a trigger mechanism for controlling the operation of the motor, comprising:

an on-off switch mounted within the hollow handle and operatively associated with the motor, said switch including an actuator normally biased to an off position and movable to an on position to operate the motor;

a manually operable trigger mounted within the handle and including a finger engageable portion projecting through a first opening provided in the handle to be engaged by the operator, said trigger including a pair of spaced, parallel arms extending backward from said finger engageable portion on opposite sides of said switch and pivotally connected to the interior of the handle, said finger engageable portion of said trigger being movable from an inoperative position to an operative position and engageable with said switch actuator upon movement to its operative position to move said switch actuator ot its on position and operate the motor, said trigger including an integral leaf spring projecting backward from said arms for engaging the interior of the handle to normally bias said finger engageable portion toward its inoperative position;

a manually operable locking device slidably mounted in a track provided within the handle for longitudinal movement relative to the handle, said locking device being shiftable laterally between first and second distinct orientations relative to the handle, said locking device being movable from a lock-off position to an unlock position in its first orientation and to a lock-on position in its second orientation, said locking device including a manually engageable portion extending through a second opening provided in the handle to be engaged by the operator and first and second arms for engaging said trigger, said first arm being cooperatively engageable with said trigger when said locking device is in its lock-off position to prevent movement of said trigger from its inoperative position to its operative position, said trigger being manually movable from its inoperative position to its operative position when said locking device is moved to its unlock position to operate said switch actuator to control operation of the motor, said second arm being cooperatively engageable with said trigger when said locking device is moved to its lock-on position to lock said trigger in its operative position to continuously hold said switch actuator in its on position and operate the motor;

means for normally biasing said locking device toward its lock-off position, said first arm of said locking device being cooperatively engageable with said trigger when said trigger is moved to its operative position and said locking device is moved to its unlock position to permit said locking device to be released without movement back to its lock-off position until said trigger is allowed to return to its inoperative position;

an obstruction projecting laterally from the interior of the handle into the path of movement of said locking device for engaging one of its arms upon movement of said locking device to its unlock position to prevent further longitudinal movement of said locking device in its first orientation, said arm being released from said obstruction upon lateral movement of said locking device from its unlock position into its second orientation to permit said locking device to be moved to its lock-on position; and

a cam surface projecting laterally from the interior of the handle oon the opposite side of said locking device from said obstruction for engaging said locking device upon release of said trigger to drive said locking device laterally from its second orientation to its first orientation during return movement of said locking device from its unlock position to its lock-off position.

9. A trigger mechanism for a hand-operated power device including a motor and a handle which supports a control operatively associated with the motor, comprising:

a trigger mounted on the handle and manually movable from a first position to a second position to actuate the control and operate the motor, said trigger being normally biased toward its first position; and

a pivotal locking device mounted on the handle and normally biased toward a lock-off position cooperatively engageable with said trigger to prevent movement of said trigger from its first position to its second position, said locking device being pivotable in a first direction from its lock-off position to an unlock position wherein said trigger is manually movable to its second position to actuate the control, said locking device being pivotable in a second direction to a lock-on position cooperatively engageable with said trigger to lock said trigger in its second position to continuously actuate the control and operate the motor, said second direction extending at an angle to said first direction.

10. A trigger mechanism for a hand-operated power tool including an electric motor and a handle which supports a switch operatively associated with the motor, comprising:

a manually operable trigger mounted on the handle and movable from an inoperative position to an operatqve position to actuate the switch to turn on the motor;

means for normally biasing said trigger toward its inoperative position;

a pivotal locking member on the handle including first and second arms for engaging said trigger, said locking member being pivotable in a first direction from a lock-off position, wherein said first arm is cooperatively engageable with said trigger to prevent movement of said trigger from its inoperative position to its operative position, to an unlock position wherein said trigger is manually movable to its operative position to actuate the switch, said locking member being pivotable in a second direction to a lock-on position wherein said second arm is cooperatively engageable with said trigger to lock said trigger in its operative position to continuously actuate the switch and operate the motor; and

means for normally biasing said locking member toward its lock-off position.

11. In a portable, hand-operated power tool including an electric motor and a handle which supports a switch operatively associated wth the motor, a trigger mechanism for operating the switch, comprising:

a manually operable trigger mounted on the handle and movable from an inoperative position to an operative position to actuate the switch to turn on the motor;

means for normally biasing said trigger toward its inoperative position;

a pivotal locking member on the handle including an arm for engaging said trigger, said locking member being pivotable in a first direction from a lock-off position, wherein said arm is cooperatively engageable with said trigger to prevent movement of said trigger from its inoperative position to its operative position, to an unlock position wherein said arm is out of the path of movement of said trigger and said trigger is manually movable to its operative position to actuate the switch, said locking member being pivotable in a second direction to a lock-on position wherein said arm is cooperatively engageable with said trigger to lock said trigger in its operative position to continuously actuate the switch and operate the motor, said second direction extending at an angle to said first direction; and

means for normally biasing said locking member toward its lock-off position.

12. In a portable, hand-operated power tool including an electric motor and a hollow handle which supports a switch operatively associated with the motor, a trigger mechanism for operating the switch, comprising:

a manually operable trigger mounted within the hollow handle and including a finger engageable body extending through a first opening provided in the handle, said trigger being movable from an inoperative position to an operative position to actuate the switch to turn on the motor, said finger engageable body including a lock-off surface and a lock-on member, said trigger further including integral spring means engaging the handle to normally bias said trigger into its inoperative position; and

a manually operable locking lever pivotally mounted within the handle adjacent to said finger engageable body of said trigger, said locking lever including a finger engageable portion extending through a second opening provided in the handle and first and second arms extending toward said finger engageable body of said trigger, said locking lever further including integral spring means engaging the handle to normally bias said lever into a lock-off position wherein said first arm is in registration with said lock-off surface of said finger engageable body to prevent movement of said trigger from its inoperative position to its operative position, said locking lever being pivotable in a first direction from its lock-off position to an unlock position wherein said first arm is out of registration with said lock-off surface and said trigger is manually movable to its operative position to actuate the switch, said locking lever being pivotable in a second direction with said trigger in its operative position to a lock-on position wherein said second arm is cooperatively engageable with said lock-on member of said trigger to lock said trigger in its operative position to continuously actuate the switch and operate the motor.

13. In a portable, hand-operated power tool including an electric motor and a hollow handle which supports a switch operatively associated with the motor, a trigger mechanism for operating the switch, comprising:

a manually operable trigger mounted within the hollow handle and including a finger engageable body extending through a first opening provided in the handle, said trigger being movable from an inoperative position to an operative position to actuate the switch to turn on the motor, said finger engageable body including a lock-off surface and a lock-on member, said trigger further including integral spring means engaging said handle to normally bias said trigger into its inoperative position; and

a manually operable locking lever pivotally mounted within the handle adjacent to said finger engageable body of said trigger, said locking lever including a finger engageable portion extending through a second opening provided in the handle and an arm extending toward said finger engageable body of said trigger, said arm including a laterally projecting finger, said locking lever furthe including first, integral spring means engaging the handle to normally bias said lever into a lock-off position wherein its finger is in registration with said lock-off surface of said finger engageable body to prevent movement of said trigger from its inoperative position to its operative position, said locking lever being pivotable in a first direction from its lock-off position to an unlock position wherein said finger is out of registration with said lock-off surface and said trigger is manually movable to its operative position to actuate the switch, said locking lever including second, integral spring means com comprising an integral leaf spring extending generally parallel to its arm and normally located in contact with said finger, said locking lever being pivotable in a second direction with said trigger in its operative position to a lock-on position wherein said finger is in registration with said lock-on member of said trigger and said second spring means is biased away from said finger to lock said trigger in its operative position to continuously actuate the switch and operate the motor, said second spring means exerting a bias force on said locking lever to pivot said locking lever in the first direction upon disengagement of said finger and said lock-on member.

14. In a portable, hand-operated power tool including an electric motor and a hollow handle which supports a switch operatively associated with the motor, a trigger mechanism for operating the switch, comprising:

a manually operable trigger mounted within the hollow handle and including a finger engageable body extending through a first opening provided in the handle, said trigger being movable from an inoperative position to an operative position to actuate the switch to turn on the motor, said trigger including a lock-off surface and a lock-on member on its finger engageable body, said trigger further including integral spring means engaging said handle to normally bias said trigger into its inoperative position;

a manually operable locking lever pivotally mounted within the handle adjacent to said finger engageable body of said trigger, said locking lever including a finger engageable portion extending through a second opening provided in the handle and an arm extending toward said finger engageable portion of said trigger;

primary spring means on said trigger engaging said locking lever to normally bias said lever into a lock-off position wherein its arm is in registration with said lock-off surface of said trigger to prevent movement of said trigger from its inoperative position to its operative position, said locking lever being pivotable in a first direction from its lock-off position to an unlock position wherein its arm is out of registration with said lock-off surface and said trigger is manually movable to its operative position to actuate the switch, said locking lever being pivotable in a second direction to a lock-on position wherein its arm is cooperatively engageable with said lock-on member of said trigger to lock said trigger in its operative position to continuously actuate the switch and operate the motor; and

secondary spring means on said trigger engaging said locking lever and rendered operative upon movement of said trigger to its operative position to bias said locking lever in the first direction and pivot said locking lever in the first direction upon disengagement of said arm and said lock-on member to permit said trigger to return to its inoperative position.

15. In a portable, hand-operated power tool including an electric motor and a hollow handle which supports a switch operatively associated with the motor, a trigger mechanism for operating the switch, comprising:

a manually operable trigger mounted within the hollow handle and including a finger engageable body extending through a first opening provided in the handle, said trigger being movable from an inoperative position to an operative position to actuate the switch to turn on the motor, said finger engageable body of said trigger including an arm extending from its front surface, said arm including a lock-off surface, an opening adjacent to said lock-off surface, and a lock-on member adjacent to said opening, said trigger including integral spring means engaging said handle to normally bias said trigger into its inoperative position; and

a manually operable locking lever pivotally mounted within the handle adjacent to said finger engageable portion of said trigger, said locking lever including a finger engageable portion extending through a second opening provided in the handle and primary and secondary leaf springs extending toward said arm of said trigger, said primary spring including a hook end for engaging said lock-on member of said arm and said secondary leaf spring including a lock-off member for engaging said lock-off surface of said arm,

said locking lever being normally biased to a lock-off position wherein its lock-off member is in registration withsaid lock-off surface to prevent movement of said trigger from its inoperative position to its operative position, said locking lever being pivotable in a first direction from its lock-off position to an unlock position wherein its locking member is in registration with said opening in said arm and said trigger is manually movable to its operative position to actuate the switch, said locking member being received in said opening upon movement of said trigger to its operative position, said locking member being pivotable in a second direction with said trigger in its operative position to move said hook end of said primary leaf spring into engagement with said lock-on member of said arm to lock said trigger in its operative position to continuously actuate the switch and operate the motor, said secondary leaf spring being rendered operative upon movement of said locking lever to its lock-on position to bias said locking lever in the first direction and pivot said locking lever in the first direction upon disengagement of said hook end of said primary spring and said lock-on member of said trigger to permit said trigger to return to its inoperative position.
Description



The present invention relates to a trigger mechanism for a hand-operated power device and, more particularly, to a trigger mechanism for a portable, hand-operated power tool driven by an electric motor which is automatically locked off when the trigger mechanism is inoperative and which permits the tool to be temporarily locked on for continuous operation of the tool.

In the prior art, portable, hand-operated power tools, e.g., electrically powered hedge or shrub trimmers, grass shears and power saws, have included trigger mechanisms incorporating automatic lock-off and manual lock-on features. These features have been provided by a locking device movable between lock-off and lock-on positions to control the operation of a trigger. The automatic lock-off feature has protected an operator against accidental operation of the power tool, and the lock-on feature has enabled the operator to continuously operate the power tool without the necessity of exerting continuous manual pressure on the trigger.

The prior art trigger mechanisms have been capable of operation by a simple activity to operate the power tool between its lock-off and lock-on states. For example, it has been possible for an operator, by continuous movement of the locking device in a single direction, to unlock the trigger mechanism from its lock-off state and to operate the trigger mechanism to its lock-on state. Since only a simple activity has been required to operate the prior art trigger mechanisms from lock-off to lock-on states, the possibility of accidental lock-on operation of the power tool has been enhanced along with the attendant risk of injury to the operator.

To avoid the disadvantages of the prior art, it is desirable to provide a trigger mechanism having automatic lock-off and manual lock-on features for a portable, hand-operated power tool which requires positive, intentional action, distinct from the activity required to unlock the trigger mechanism, to operate the trigger mechanism into its lock-on state. The requirement of a positive, intentional action minimizes the possibility of inadvertent lock-on operation of the tool.

It is an object of the present invention to provide a trigger mechanism for a hand-operated power tool which provides automatic lock-off and manual lock-on operation and requires an operator to consciously perform a complex activity to operate the trigger mechanism from its lock-off state to its lock-on state to minimize the possibility of inadvertent operation of the tool.

It is an additional object of the present invention to provide a trigger mechanism for a hand-operated power tool incorporating a locking device, normally located in a lock-off position, which is movable in two (2) distinct modes of movement, a first mode including an unlock position and a second mode including a lock-on position, which requires a positive, intentional action by an operator to shift the locking device from its first mode of movement to its second mode of movement, and which can only be shifted to its second mode after the trigger mechanism is actuated "on".

It is a further object of the present invention to provide a trigger mechanism for a hand-operated power tool incorporating a locking device which is automatically returned to its lock-off position upon termination of the operator of the trigger mechanism.

In accordance with the invention, a trigger mechanism for a hand-operated power device including a motor and a control operatively associated with the motor includes a trigger manually movable from an inoperative position to an operative position to actuate the control and operate the mtoor, and locking means cooperatively engageable with the trigger for normally locking the trigger in its first position, the locking means being movable in first and second distinct modes of movement, with the first mode including a normal, lock-off position wherein the locking means is cooperatively engageable with the trigger to prevent movement of the trigger from its inoperative position to its operative position and an unlock position wherein the trigger is movable to its operative position to actuate the control and the second mode including a lock-on position wherein the locking means is cooperatively engageable with the trigger to lock the trigger in its operative position to continuously actuate the control and operate the motor. Preferably, the trigger is normally biased toward its inoperative position and the locking means is normally biased toward its lock-off position. A positive, intentional action is required by an operator to shift the locking means from its first mode of movement to its second mode of movement to reduce the likelihood of inadvertent operation of the power device to its lock-on state and thus minimize the risk of injury to the operator.

In a preferred embodiment of the trigger mechanism, for use in a hand-operated power tool including an electric motor and a handle which supports a switch operatively associated with the motor, the locking means comprises a manually operable locking device slidably mounted on the handle and movable in two (2) distinct orientations relative to the handle. The slidable locking device is movable longitudinally relative to the handle, in its first orientation, from a lock-off position, cooperatively engageable with the trigger to prevent movement of the trigger from its inoperative position to its operative position, toward an unlock position wherein the trigger is manually movable to its operative position to actuate the switch.

Upon movement to its unlock position, the locking device is shiftable laterally relative to the handle, into its second orientation, and subsequently movable longitudinally relative to the handle to a lock-on position cooperatively engageable with the trigger to lock the trigger in its operative position to continuously actuate the switch and operate the motor. A positive, intentional action, i.e., a lateral shifting of the locking device from its first orientation to its second orientation, is required to operate the trigger mechanism to its lock-on state. Furthermore, the locking device is movable to its second orientation only when the trigger is in its operative position.

The slidable locking device is normally biased toward its lock-off position with the locking device in its unlock position and the trigger in its operative position, the locking device is cooperatively engageable with the trigger to permit the operator to release the locking device without movement back to its lock-off position until the trigger is returned to its inoperative position. If, with the locking device in its unlock position, the trigger is completely released, the locking device is automatically returned to its lock-off position to lock the trigger in its inoperative position. Similarly, if, with the locking device in its lock-on position, the trigger is disengaged from the locking device and completely released, the locking device is automatically returned to its lock-off position to lock the trigger in its inoperative position.

In an alternative embodiment of the trigger mechanism, the locking means comprises a pivotal locking device mounted on the handle and pivotable in a first direction from a lock-off position, cooperatively engageable with the trigger to prevent movement of the trigger from its inoperative position to its operative position, toward an unlock position wherein the trigger is manually movable to its operative position to actuate the switch. With the trigger in its operative position, the locking device is pivotable in a second direction to a lock-on position cooperatively engageable with the trigger to lock the trigger in its operative position to continuously actuate the switch and operate the motor. A positive, intentional action, i.e., a reversal of the direction of pivotal movement of the locking device, is required to operate the trigger mechanism to its lock-on state.

The pivotal locking device is normally biased toward its lock-off position and the trigger is normally biased toward its inoperative position. With the locking device in its unlock position and the trigger in its operative position, the locking device is cooperatively engageable with the trigger to permit the locking device to be released without movement back to its first position until the trigger is allowed to return to its inoperative position. If, with the locking device in its unlock position, the trigger is completely released, the locking device is automatically returned to its lock-off position to lock the trigger in its inoperative position. Similarly, if, with the locking device in its lock-on position, the trigger is disengaged from the locking device and completely released, the locking device is automatically returned to its lock-off position to lock the trigger in its inoperative position.

The automatic lock-off and manual lock-on features of the trigger mechanism of the present invention preclude inadvertent operation of the power tool. The automatic lock-off feature requires an operator to perform an unlock activity prior to actuation of the trigger to operate the tool. In addition, the manual lock-on feature requires the operator to perform a positive, intentional action, which is distinct from the unlock activity, to achieve lock-on operation of the power tool. These safety features of the trigger mechanism prevent an inexperienced operator from accidentally turning on the power tool and locking the tool on for continuous operation .

The accompanying drawings illustrate preferred embodiments of the invention and, together with the description, serve to explain the principles of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side elevation, partially cutaway, of a portable hand-operated power tool, e.g., a shrub or hedge trimmer, including a handle which supports a trigger mechanism constructed in accordance with the principles of the present invention, a motor, and a cutting blade assembly;

FIG. 2 is a plan view of the portable power tool of FIG. 1 illustrating the construction of the handle in two sections;

FIG. 3 is an enlarged side view, taken along line 3--3 of FIG. 2, of the handle of the portable power tool, with one handle section removed, illustrating a manually movable trigger and a slidable locking device of the trigger mechanism with the locking device in its lock-off position and the trigger in its inoperative position;

Fig. 4 is an enlarged side view of the same power tool handle of FIG. 1 illustrating the locking device moved to its unlock position to permit the trigger to be manually moved to its operative position;

FIG. 5 is an enlarged side view of the same power tool handle of FIG. 1 illustrating the locking device moved to its lock-on position to lock the trigger in its operative position;

FIG. 6 is an enlarged side view of the opposite section of the power tool handle of FIG. 3 illustrating the locking device moved to its lock-on position to lock the trigger in its operative position;

FIG. 7 is an enlarged perspective view of a portion of the handle section and locking device of FIG. 3;

FIG. 8A is a plan view, partially cutaway, of a portion of the power tool handle illustrating the locking device in its lock-off position;

FIG. 8B is a plan view of the same portion of the handle illustrating the locking device moved in a first orientation relative to the power tool handle to its unlock position;

FIG. 8C is a plan view of the same portion of the handle illustrating the locking device shifted laterally from its unlock position into a second orientation relative to the power tool handle;

FIG. 8D is a plan view of the same portion of the handle illustrating the locking device moved in its second orientation to its lock-on position;

FIG. 9 is a side view, partially in section, of a portion of a power tool handle which includes an alternative embodiment of the trigger mechanism of this invention incorporating a slidable locking device;

FIG. 10 is a side view, partially in section, of a portion of a power tool handle including an alternative embodiment of the trigger mechanism of this invention which incorporates a pivotal locking device having a pair of locking arms which are cooperatively engageable with a trigger to provide for automatic lock-off and manual lock-on operation of the trigger;

FIG. 11 is a side view, partially in section, of a portion of a power tool handle including an alternative embodiment of the trigger mechanism of this invention incorporating a pivotal locking device having a single locking arm which is cooperatively engageable with a trigger to provide for automatic lock-off and manual lock-on operation of the trigger;

FIG. 12 is a side view, paritally in section, of a portion of a power tool handle including an alternative embodiment of the trigger mechanism of this invention which incorporates a trigger having first and second integral leaf springs to provide bias forces for a pivotal locking device having a single locking arm cooperatively engageable with the trigger to provide for automatic lock-off and manual lock-on operation of the trigger;

FIG. 13 is a side view, partially in section, of a portion of a power tool handle which incorporates an alternative embodiment of the trigger mechanism of this invention including a pivotal locking device having a pair of spring arms which are cooperatively engageable with the trigger to produce desired bias forces on the locking device and to provide for automatic lock-off and manual lock-on operation of the trigger;

FIG. 14 is a side view, partially in section, of a portion of a power tool handle including an alternative embodiment of the trigger mechanism of this invention which incorporates a pivotal locking device including an integral leaf spring and a single locking arm which is cooperatively engageable with a trigger to provide for automatic lock-off and manual lock-on operation of the trigger;

FIG. 15 illustrates the trigger mechanism of FIG. 14 with the locking device moved to its unlock position;

FIG. 16 illustrates the trigger mechanism of FIG. 14 with the trigger moved to its operative position; and

FIG. 17 illustrates the trigger mechanism of FIG. 14 with the locking device moved to its lock-on position to lock the trigger in its operative position.

Trigger mechanisms including slidable locking devices

fig. 1 illustrates a portable, hand-operated power tool, e.g., a shrub or hedge trimmer, which incorporates a trigger mechanism constructed according to the principles of this invention. The power tool includes an elongated, hollow handle, generally 30, consisting of two (2) half-sections 32 and 34 (FIG. 2). The half-sections of handle 30 are held together by a plurality of screws or bolts 36, 38, 40 and 42 (FIG. 1).

Referring to FIGS. 1 and 2, handle 30 includes a rearward portion which is relatively narrow and elongated to provide a convenient shape to be gripped by one hand of an operator. As shown in FIG. 2, the handle includes a forward portion which is greater in width than the rearward portion to provide support for a motor 44 which drives the power tool. A cutting blade assembly, generally 46, extends forward from the front end of handle 30. The cutting blade assembly is standard in construction and, thus, only a portion of the assembly is shown in FIGS. 1 and 2.

Cutting blade assembly 46 includes a lower, stationry blade 48 and an upper, reciprocating blade 50. The blade assembly also includes an elongated support member 52 which extends forward from the front end of the handle above reciprocating blade 50. Lower, stationary cutting blade 48 is secured to support member 52 by a plurality of nuts and bolts 54 (one shown in FIG. 1) spaced along the cutting blade assembly. Upper, reciprocating blade 50 includes a plurality of elongated slots 56 extending longitudinally along the blade for receiving bolts 54 to permit blade 50 to be reciprocated relative to stationary blade 48 and support member 52. A drive mechanism (not shown) is provided to convert rotary output of motor 44 to reciprocating motion of blade 50. Alternatively, the blades 48, 50 can reciprocate in opposite directions through a suitable transmission.

A generally cylindrical cover 58 (FIG. 1) is supported by the wide, forward portion of the handle 30 to protect the motor and drive mechanism. A hand grip 60 is secured at the top of cover 58 to allow the operator to grip the tool with both hands.

In the present embodiment, the rear end of handle 30 is provided with a power cord receptacle 62 for receiving a detachable power cord to connect the tool to an electrical power source. The power cord receptacle receives a specially shaped power cord connector (not shown) of a detachable power cord to enable the tool to be connected to the power source. It is understood that the detachable power cord and receptacle do not constitute any part of the present invention and that other power cord arrangements, e.g., a permanently attached power cord, can be used to supply electric power to the tool.

Referring to FIG. 3, the tool includes a plug 64 located within the interior of handle 30 with a pair of plug blades 66 (one shown in FIG. 3) extending rearwardly into power cord receptacle 62. A generally rectangular support 68 extends inwardly from the interior of handle section 32 for supporting plug 64 in a fixed position relative to the handle. The connector of the detachable power cord (not shown) received in power cord receptacle 62 is adapted to make electrical contact with plug blades 66 to connect the tool to a source of electrical power. Support 68 includes a first cylindrical projection 70 extending inwardly from the interior of handle section 32 including a central opening for receiving screw 36 in the assembly of the handle.

As shown in FIG. 3 the power tool handle supports a control in the form of a switch 72 operatively associated with motor 44. Switch 72 includes an actuator 74, normally biased downward to an off position and movable upward to an on position to operate the motor. A pair of conductors 76 (only one shown) connects plug 64 to switch 72. A second pair of conductors 78 (only one shown) connects switch 72 to motor 44. Conductor 78 extends between a flange 80 and a second cylindrical projection 82 extending inwardly from the interior of handle section 32. Cylindrical projection 82 includes a central opening for receiving screw 38 (FIG. 1) in the assembly of the handle. Similar cylindrical projections (not shown) are provided on the interior of handle section 32 for receiving screws 40 and 42 (FIG. 1).

As shown in FIG. 3, the body of switch 72 is substantially rectangular in shape and is received in a generally rectangular area in the handle defined by a rearward stop 84 projecting inwardly from the interior of handle section 32, a first pair of ribs 86 projecting downwardly from the top of handle section 32, a second pair of ribs 88 extending upwardly from the bottom of handle section 32, and a forward wall 90 projecting downward from the top of the handle section.

The power tool handle supports a trigger mechanism for actuating switch 72 to control on-off operation of motor 44. The trigger mechanism provides automatic lock-off, manual unlock and manual lock-on operations for control of the motor. The lock-on operation requires a positive, intentional action by the operator to achieve continuous operation of the motor.

In accordance with the invention, the trigger mechanism includes a trigger manually movable from a first, inoperative position to a second, operative position to actuate the control and operate the motor. In a preferred embodiment of the trigger mechanism, means is provided for normally biasing the trigger toward its first, inoperative position. The preferred embodiment of the trigger mechanism shown in FIG. 3 includes a trigger, generally 100, mounted within the interior of handle 30 and having a finger engageable portion or body 102 protruding downwardly through a trigger opening 103 defined by adjacent slots provided in the bottom of handle sections 32 and 34. Trigger 100, which may be constructed of a suitable elastomeric and essentially nonconductive material, also includes a pair of spaced, parallel arms 104 extending rearwardly from its finger engageable portion 102.

As shown in FIG. 3, switch 72 is positioned in the space between arms 104 of the trigger. The arms terminate in a collar 106 which is pivotally mounted on a pin 108 projecting inwardly from the interior of handle section 34 to pivotally support trigger 100. In addition, the trigger includes an integral flexible finger or leaf spring 110 which extends backward from collar 106 and engages the bottom of handle sections 32 and 34 to normally bias finger engageable portion 102 of the trigger in a downward, inoperative position (FIG. 3). Finger engageable portion 102 of the trigger is movable upward to an operative position (FIGS. 4 and 5), in which case the finger 110 deflects as shown. The finger engageable portion 102 of trigger 100 includes a surface 105 located between arms 104 for engaging actuator 74 of the switch upon movement of the trigger to its operative position.

As shown in FIG. 3, an arm 112 extends vertically upward from the front edge of finger engageable portion 102 of trigger 100. A finger 114 projects horizontally forward from arm 112. The upper end of arm 112 terminates in a flat, lock-off surface 115. A first flange 116 is provided on the upper surface of finger 114, and a second flange or lock-on member 118 is provided on the lower surface of the finger.

In accordance with the invention, the trigger mechanism also includes locking means cooperatively engageable with the trigger for normally locking the trigger in its first or inoperative position. The locking means is movable in first and second distinct modes of movement with the first mode including a normal, lock-off position wherein the locking means is cooperatively engageable with the trigger to prevent movement of the trigger from its first, inoperative position to its second, operative position, and an unlock position wherein the trigger is movable to its second position to actuate the control, and the second mode including a lock-on position wherein the locking means is cooperatively engageable with the trigger to lock the trigger in its second or operative position to continuously actuate the control and operate the motor. The locking means requires a positive, intentional action by an operator to shift the locking means from its first mode of movement to its second mode of movement. The requirement of a positive, intentional action minimizes the possibility of inadvertent movement of the locking means to its lock-on position and reduces the risk of injury to the operator.

Referring to FIG. 3, in the preferred embodiment of the trigger mechanism, the locking means is embodied as a manually operable locking devide 120 slidably mounted for longitudinal movement relative to handle 30. The locking device comprises a platform 122, generally trapezoidal in shape, having first and second spaced arms 124 and 126, respectively, projecting downward from the platform.

Arm 126 is located at the front of platform 122 and includes a finger 128 projecting laterally backward from the arm and a raised lip 130 projecting upward from the rear edge of the finger. As shown in FIg. 7, lip 130 extends diagonally across finger 128 at a predetermined angle. First arm 124 is inclined in a forward direction and terminates in a lower, lock-off surface 132.

Referring to FIG. 3, a finger engageable button 134 is mounted on a stem 136 which projects upwardly from the top surface of platform 122. The upper surface of button 134 is shaped to facilitate manual movement of the locking device. Stem 136 projects upward through an opening in the handle provided by corresponding slots formed at adjacent locations in the top of handle sections 32 and 34 (FIG. 2).

A pin 140 (FIG. 3) projects rearwardly from the rear edge of platform 122 and is received in the front end of a coil spring 142. The opposite end of coil spring 142 engages vertical wall 90. The coil spring is received in a channel defined by the top of the handle section 32 and a horizontal rib 144 extending inwardly from the interior of the handle section. The rear end of coil spring 142 is confined laterally between surfaces 146 and 148 (FIG. 8A) provided on handle sections 32 and 34, respectively. The coil spring normally biases the front edge of locking device 120 into engagement with a vertical wall 149 provided by the two (2) handle sections.

Referring to FIG. 8A, the front edge of platform 122 of locking device 120 is narrower in width than its rear edge. The platform is provided with a pair of rounded flanges 150 and 152 projecting laterally from its front edge. A flange 154 projects laterally from the rear edge of platform 122 on the same side of the platform as flange 152. The rear edge of the platform also includes a rounded corner 156 opposite flange 154.

Referring to FIG. 3, handle section 32 includes an elongated rib 158 projecting inwardly from its interior which, with the top of the handle section, provides an elongated track for receiving rounded flange 150 and corner 156 of platform 122. As shown in FIG. 8A, corner 156 of the platform engages an elongated, straight guide surface 160 formed on the interior of handle section 32. Guide surface 160 includes an inwardly tapered cam surface 162 located adjacent to vertical wall 149. In addition, rib 158 is provided with a similar inwardly tapered cam surface 164.

Referring to FIG. 6, handle section 34 includes a rib 166 projecting inwardly from its interior. Rib 166 is cutaway at a predetermined distance from front wall 149 to establish a ledge or obstruction 168 in the path of movement of second arm 126 of the locking device. In addition, an elongated, straight guide surface 170 is provided on the interior of handle section 34. As shown in FIG. 8A, pin 140 of platform 122 is offset laterally from the center line of the platform. As a result, coil spring 142 exerts a biasing force on platform 120 which produces a moment about the point of contact between rounded flange 154 of the platform and guide surface 170 of handle section 34 to normally urge rounded flange 152 of the platform into engagement with guide surface 170.

Guide surfaces 160 and 170 of the handle sections permit locking device 120 to be moved longitudinally in two (2) distinct orientations relative to the handle. A first orientation, shown in FIGS. 8A and 8B, exists when rounded flanges 152 and 154 of platform 122 are in contact with guide surface 170 of handle section 34. Longitudinal movement of locking device 120 in its first orientation constitutes a first mode of movement relative to the handle. A second orientation, shown in FIGS. 8C and 8D, exists when rounded flange 150 and rounded corner 156 of the platform are in contact with guide surface 160 of handle section 32. Similarly, longitudinal movement of locking device 120 in its second orientation constitutes a second mode of movement relative to the handle.

As shown in FIG. 3, handle section 32 includes a horizontal rib 171 projecting inwardly from its interior and extending parallel to rib 158. Similarly, handle section 34 (FIG. 6) includes a corresponding horizontal rib 172 projecting inwardly from its interior. The lower end of first arm 124 of locking device 120 is located between ribs 171 and 172 to further guide the locking device in its longitudinal movement relative to the handle.

In the operation of the trigger mechanism of the preferred embodiment, trigger 100 is normally biased toward its inoperative position (FIGS. 3 and 8A) by its flexible finger 110. In addition, locking devide 120 is normally biased forward into a lock-off position by coil spring 142. As shown in FIG. 3, when locking device 120 is in its forward, lock-off position, lock-off surface 132 on the lower end of first arm 124 is located in registration with top surface 115 of trigger finger 114 to prevent upward movement of the trigger 100 from its inoperative position.

When it is desired to unlock the trigger mechanism, the operator manually engages button 134 and slides locking device 120 longitudinally backward to its unlock position (FIGS. 4 and 8B). As shown in FIG. 8B, with locking device 120 in its first orientation, i.e., with rounded flanges 152 and 154 of platform 122 in contact with guide surface 170 of handle section 34, the locking device is limited in the extent of its longitudinal movement relative to the handle by ledge 168. When locking device 120 is moved longitudinally backward from its unlock position in its first orientation, it can only be moved backward until its second arm 126 moves into engagement with ledge 168. The initial backward movement of locking device 120 from its lock-off position to its unlock position, with the locking device oriented parallel to the longitudinal axis of the handle, constitutes its first mode of movement. At this point, locking device 120 is not, however, capable of any further backward movement in its first orientation.

Referring to FIG. 4, with locking device 120 located in its unlock position, the operator can move the trigger 100 upward to its operative position by manually applying pressure to finger engageable portion 102. Upon upward movement of trigger 100 to its operative position, arm 112 and finger 114 of the trigger move upward between arms 124 and 126 of locking device 120. At the same time, actuating surface 105 of the trigger moves actuator 74 of switch 72 upward to actuate the switch and operate motor 44.

With trigger 100 moved upward to its operative position and locking device 120 moved to its unlock position, the trigger and locking device are cooperatively engageable to permit the locking device to be released without movement back to its lock-off position until the trigger is allowed to return to its inoperative position. If the operator disengages button 134 to permit locking device 120 to be urged forward by coil spring 142, the locking device moves forward by a slight distance until its first arm 124 engages arm 112 of the trigger. Thus, with trigger 100 raised to its operative position (FIG. 4), its arm 112 prevents locking device 120 from returning to its lock-off position until the trigger is returned to its downward, inoperative position (FIG. 3). If, however, the trigger is completely released by the operator, locking device 120 is automatically returned to its lock-off position (FIGS. 3 and 8A) by coil spring 142.

As described above, ledge 168 which projects laterally inward from handle section 34 into the path of movement of locking device 120, limits the locking device to longitudinal movement by a predetermined distance in its first orientation. After locking device 120 is moved backward to its unlock position, i.e., with its arm 126 in contact with ledge 168 (FIG. 8B), it is necessary to shift the locking device laterally into its second orientation relative to the handle to permit further longitudinal movement of the locking device. Referring to FIG. 8C, locking device 120 can be shifted laterally relative to the handle into its second orientation by pivotal movement of the locking device in a counterclockwise direction about its rounded corner 156. The lateral shifting motion of locking device 120 is terminated when its rounded flange 150 moves into engagement with guide surface 160 of handle section 32. This lateral movement of locking device 120 is sufficient to disengage second arm 126 of the locking device from ledge 168. Thus, with locking device 120 in its second, diagonal orientation relative to the longitudinal axis of the handle, i.e., with its rounded flange 150 and corner 156 in contact with guide surface 160, the locking device can be moved longitudinally backward relative to the handle to its lock-on position (FIGS. 5 and 8D). The further backward movement of locking device 120, which becomes capable with the locking device oriented diagonally relative to the longitudinal axis of the handle, consitutes its second mode of movement and can be achieved only when trigger 100 is moved upwardly to its operative position so that finger 114 is clear of lip 130. As shown in FIGS. 8C and 8D, with locking device 120 in its second, diagonal orientation relative to the handle, ridge 130 on second arm 126 of the locking device is moved to a central position and oriented perpendicularly relative to the longitudinal axis of the handle.

Referring to FIG. 4, to permit locking device 120 to be moved backward from its unlock position to its lock-on position, it is necessary to move finger engageable portion 102 of trigger 100 upward by a sufficient distance to raise its finger 114 and flange 118 above finger 128 and ridge 130 of the locking device. The operator can then move locking device 120 backward to its lock-on position (FIGS. 5 and 8D). As shown in FIG. 5, upon release of trigger 100, its flange 118 engages ridge 130 of locking device 120 to lock the trigger in its operative position and to prevent forward movement of the locking device by coil spring 142. At this time, the operator can disengage trigger 100 and button 134 without terminating operation of motor 44.

When it is desired to terminate lock-on operation of the trigger mechanism, the operator manually engages trigger 100 and moves its finger engageable portion 102 upward to disengage flange 118 of the trigger from ridge 130 of the locking device. Coil spring 142 immediately moves locking device 120 forward until its first arm 124 engages arm 112 of the trigger. The locking device is thus held in its unlock position (FIG. 4) until trigger 100 is completely released.

When the operator disengages trigger 100 to allow it to return to its inoperative position, locking device 120 is moved forward to its lock-off position by coil spring 142. During forward movement of the locking device from its unlock position to its lock-off position, rounded flange 150 and second arm 126 of the locking device move along cam surfaces 162 and 164 (FIG. 8C), respectively, to shift the locking device laterally back to its first orientation by pivotal movement of the locking device in a clockwise direction. The locking device is thus automatically returned to its lock-off position (FIGS. 3 and 8A).

FIG. 9 illustrates a first alternative embodiment of the trigger mechanism which, like the embodiment of FIGS. 3-8, incorporates a locking device slidably mounted on the power tool handle. The trigger mechanism of FIG. 9 includes a trigger, generally 174, having a finger engageable portion 176 which extends downwardly through an opening provided in the bottom of the power tool handle. A pair of spaced, parallel arms 178 (one shown) extend rearwardly from the finger engageable portion. A switch 180 is mounted in the space between arms 178 and includes an actuator 182 normally biased downward to an off position and movable upward to an on position to operate the power tool motor. Trigger 174 includes an actuating surface 184 located between its arms 178 for engaging switch actuator 182. The remaining rearward structure of the trigger is not illustrated, but it can be substantially the same as the structure of trigger 100 of FIGS. 3-6.

Finger engageable portion 176 (FIG. 9) is hollow and includes a thick front wall provided with an upwardly extending arm 186. The upper end of arm 186 terminates in a flat, lock-off surface 187. A finger 188 projects forwardly from arm 186 and is provided with a downwardly projecting lock-on member or lip 189.

The trigger mechanism of FIG. 9 also includes a slidable locking device, generally 190, mounted for longitudinal and lateral movement relative to the handle. The locking device includes a platform 191 slidably received in an elongated track 192 provided in the handle. A coil spring 193 engages the rear end of platform 191 to normally bias locking device 190 in a forward direction. A manually engageable button 194 extends upwardly from platform 191 through an opening provided in the top of the handle to enable an operator to move the locking device relative to the handle.

Locking device 190 includes first and second arms 195 and 196, respectively, extending downwardly from platform 191. A rib 197 projects forwardly from first arm 195 toward second arm 196. Second arm 196 includes a rearwardly projecting finger 198 provided with an upwardly extending ridge 199 at its rear end.

In the operation of the trigger mechanism of FIG. 9, trigger 174 is normally biased downward to its inoperative position by resilient means such as flexible finger 110 of the first embodiment. In addition, locking device 190 is normally biased forward into a lock-off position by coil spring 193. With locking device 190 in its forward, lock-off position, the lower end of its first arm 195 is located in registration with the top, lock-off surface of arm 186 of trigger 174 to prevent upward movement of the trigger from its inoperative position.

When it is desired to unlock the trigger mechanism, the operator manually engages button 194 and slides locking devide 190 longitudinally backward to an unlock position. The longitudinal movement of locking device 190 backward from its lock-off position to its unlock position constitutes its first mode of movement. With locking device 190 located in its unlock position, the operator can move trigger 174 upward to its operative position by manually applying pressure to its finger engageable portion 176. Upon upward movement of trigger 174 to its operative position, arm 186 of the trigger moves upward between arms 195 and 196 of locking device 190 until its upper surface 187 moves into contact with rib 197 of the locking device. At the same time, actuating surface 184 of the Trigger moves switch actuator 182 upward to actuate switch 180. to actuate switch 180.

With locking device 190 in its unlock position, its rib 197 limits the extent of upward movement of trigger 174. Thus, with trigger 174 in its operative position, if the operator attempts to move locking device 190 longitudinally backward relative to the handle, finger 198 of its second arm 196 engages finger 188 of the trigger to prevent further longitudinal movement of the locking device relative to the handle.

Further, with trigger 174 in its operative position and locking device 190 in its unlock position, the trigger and locking device are cooperatively engageable to permit the locking device to be released without movement back to its lock-off position until the trigger is allowed to return to its inoperative position. If the operator disengages button 194 to permit locking device 190 to be urged forward by coil spring 193, the locking device moves forward by a slight distance until its first arm 195 engages arm 186 of the trigger. Thus, with trigger 174 raised to its operative position, its arm 186 prevents locking device 190 from returning to its lock-off position until the trigger is returned to its downward, inoperative position.

If it is desired to lock trigger 174 in its operative position to containuously actuate switch 180, the operator manually engages button 194 and moves locking device 190 laterally relative to the handle to move rib 197 laterally out of the vertical path of movement of arm 186 of the trigger. With locking device 190 and its rib 197 shifted laterally relative to the handle, trigger 174 can be raised upward by a further distance to move its finger 188 out of the longitudinal path of movement of finger 198 of the locking device. The operator can then move locking device 190 longitudinally backward to a lock-on position (indicated in phantom lines). The longitudinal movement of locking device 190, after it is shifted laterally relative to the handle, constitutes its second mode of movement. Upon release of trigger 174 by the operator, its lock-on member or lip 189 engages ridge 199 of locking device 190 to lock the trigger in its operative position and to prevent forward movement of locking device by coil spring 193. At this time, the operator can disengage trigger 174 and button 194 without terminating operation of the power tool motor.

When it is desired to terminate lock-on operation of the trigger mechanism, the operator manually engages trigger 174 and moves its finger engageable portion 176 upward to disengage locking member or lip 189 of the trigger from ridge 198 of the locking device. Coil spring 193 immediately moves locking device forward until its first arm 195 engages arm 186 of the trigger. The locking device is held in its unlock position until trigger 174 is completely released.

When the operator disengages trigger 174 to allow it to return to its inoperative position, locking device 190 is automatically returned to its lock-off position by coil spring 193. The handle can be provided with cam surfaces (not shown), similar to cam surfaces 162 and 164 of the preferred embodiment (FIGS. 5 and 8B) to return locking device 190 laterally to its first mode of movement during forward movement of the locking device from its unlock position to its lock-off position.

The embodiments of FIGS. 3-9 provide trigger mechanisms having automatic lock-off and manual lock-on features. Each trigger mechanism provides two (2) distinct modes of movement for its locking device and requires a positive, intentional action, i.e., lateral movement of the locking device relative to the handle, to shift the locking device between its first mode of movement and second mode of movement. This requirement of a positive, intentional action precludes inadvertent operation of the trigger mechanism to its lock-on state.

Trigger mechanisms including pivotal locking devices

figs. 10, 11, 12, 13 and 14 illustrate further alternative embodiments of the trigger mechanism of the present invention for use in connection with hand-operated power tools. Each of the embodiments includes a pivotal locking device pivotable in a first direction from a first position, cooperatively engageable with the trigger to prevent movement of the trigger from its inoperative to its operative position, toward a second position wherein the trigger is manually movable to its operative position to actuate the switch. In addition, the locking device is pivotable in a second direction to a third position cooperatively engageable with the trigger to lock the trigger in its operative position to continuously actuate the switch and operate the motor. Pivotal movement of the locking device in its first direction constitutes a first mode of movement, and pivotal movement in its second direction, a second mode of movement.

Referring to FIG. 10, a second alternative embodiment of the trigger mechanism includes a trigger, generally 200, including a finger engageable portion 202 which extends downwardly through an opening provided in the bottom of the power tool handle. A pair of spaced, parallel arms 204 (one shown) extends rearwardly from the finger engageable portion. A switch 206 is mounted in the space between arms 204. The switch includes an actuator 208 normally biased downward to an off position and movable upward to an on position to operate the power tool motor. Trigger 200 includes an actuating surface 210 located between its arms 204 for engaging switch actuator 208. The rearward ends of arms 204 terminate in a collar 212 pivotally mounted on a pin 214 projecting inwardly from the interior of the power tool handle. Like the previous embodiments, trigger 200 may be constructed from plastic or suitable elastomeric and essentially nonconductive material and may have an integral flexible finger or leaf spring 215 extending backward from collar 212 and engaging the interior of the handle to normally bias finger engageable portion 202 of the trigger to its downward, inoperative position. Finger engageable portion 202 is hollow and includes an arm 216 projecting upward from its base. The upper end of arm 216 includes a flat ledge or lock-off surface 218 and a stop 220. In addition, the front edge of finger engageable portion 202 of the trigger is provided with a sharp, downwardly projecting lock-on member or lip 222.

The trigger mechanism of FIG. 10 also includes a pivotal locking device, generally 230, comprising a cylindrical body 232 mounted on a pivot pin 234 projecting inwardly from the interior of the handle section. A stem 236 extends upwardly from cylindrical body 232 through an opening provided in the top of the handle. A button 238 is provided at the top of stem 236 to enable the operator to manually pivot locking device 230 about its pivot pin 234.

Locking device 230 also includes an integral leaf spring 240 extending backward from cylindrical body 232. The spring is received in a notch 242 provided in the handle. In addition, locking device 230 includes a first arm 244 projecting radially from cylindrical body 232 and normally in registration with ledge 218 of trigger 200 to prevent movement of the trigger from its inoperative position. A second arm 246 also projects radially from cylindrical body 232 and includes a hook end 248.

In the operation of the trigger mechanism of FIG. 10, leaf spring 240 normally maintains locking device 230 in a lock-off position wherein arm 244 of the locking device is in registration with ledge 218 of trigger 200 to prevent movement of the trigger from its inoperative position. With the locking device in its lock-off position, stop 220 prevents pivotal movement of the locking device in a clockwise direction. When it is desired to operate the trigger mechanism, an operator manually engages and moves button 238 in the direction indicated by arrow 252 against the action of leaf spring 240 to pivot locking device 230 in a counterclockwise direction to an unlock position. Arm 244 is thus moved out of registration with ledge 218 of trigger 200 to permit the operator to raise finger engageable portion 202 of the trigger to its operative position to move actuator 208 upward to actuate switch 206 and operate the motor.

If, after unlocking the trigger mechanism, it is desired to lock the trigger in its operative position (indicated by phantom lines), the operator must intentionally move button 238 in the opposite direction indicated by arrow 254 also against the action of leaf spring 240 to pivot locking device 230 in a clockwise direction to move its hook end 248 into engagement with lip 222 of the trigger. The operator can then release both trigger 200 and button 238 without terminating the operation of the motor.

When it is desired to terminate the lock-on operation of the trigger mechanism, the operator raises trigger 200 to disengage its lip 222 from hook end 248 of locking device 230. Upon disengagement of the lip and hook end, locking device 230 is moved toward its intermediate lock-off position by integral leaf spring 240. When trigger 200 is allowed to return to its inoperative position, locking device 230 is automatically returned to its lock-off position and its arm 244 is in registration with ledge 218 of the trigger to lock the trigger in its inoperative position.

Referring to FIG. 11, a third alternative embodiment of the trigger mechanism includes a trigger, generally 300, including a finger engageable portion 302 which extends downwardly through an opening provided in the bottom of the power tool handle. An arm 304 extends rearwardly from the finger engageable portion. Arm 304 terminates in a collar 306 pivotally mounted on a pin 308 extending inwardly from the interior of the power tool handle. An integral leaf spring 310 extends rearwardly from collar 306 and engages the handle to bias trigger 300 in a normally downward, inoperative position. Finger engageable portion 302 is hollow and includes a thick front wall 312 having a flat top surface 314 for engaging an actuator 316 of a switch 318. Switch actuator 316 is normally biased downward to an off position and is movable upward to an on position to operate the power tool motor. In addition, an arm 320 projects forwardly from the front edge of trigger 300 and includes an upper, lock-off surface 322 and downwardly projecting lock-on member or lip 324.

The trigger mechanism of FIG. 11 also includes a pivotable locking device, generally 330, comprising cylindrical body 332 mounted on a pivot pin 334 projecting inwardly from the interior of the handle. A stem 336 extends upwardly from cylindrical body 332 through an opening provided in the top of the handle. A button 338 is provided at the top of stem 336 to permit an operator to pivot locking device 330 about its pivot pin 334.

A primary, integral leaf spring 340 projects downward from stem 336 and is received in a notch 342 provided in the lower surface of the handle. An arm 344 projects downward from cylindrical body 332 and terminates in a finger 346 having an upwardly extending ridge 348. A second, integral leaf spring 350 projects downward from cylindrical body 332 and includes a bent end 352 which normally engages the inner edge of ridge 348.

In the operation of the trigger mechanism of FIG. 11, primary spring 340 normally biases locking device 330 into a lock-off position wherein finger 346 of the locking device is located above arm 320 in registration with lock-off surface 322 to prevent movement of the trigger from its downward, inoperative position to its upward, operative position. When it is desired to unlock the trigger mechanism, the operator engages and moves button 338 backward as indicated by arrow 354 to pivot locking device 330 in a counterclockwise direction to an unlock position to move finger 346 of the locking device out of the path of movement of arm 320 of the trigger. The operator can then raise trigger 300 to its operative position (indicated by phantom lines) to move actuator 316 upward to actuate switch 318 and operate the motor. If, after movement of locking device 330 to its unlock position, the operator releases button 338, the locking device is urged toward its initial position by return bias action of primary spring 340 until secondary spring 350 engages the front edge of arm 320 of the trigger. Secondary spring 350 is of sufficient strength to resist bending under the return bias action of primary spring 340. Thus, upon release of button 338, locking device 330 pivots in a clockwise direction toward its initial position, but it cannot completely return to its initial position because of the engagement between finger 320 of the trigger and secondary spring 350 of the locking device.

If it is desired to lock trigger 300 in its operative position, the operator engages and moves button 338 forward as indicated by arrow 356 to pivot locking device 330 in a clockwise direction to its lock-on position. The operator, by applying sufficient pressure on button 338, can overcome the resistance of secondary spring 350. Thus, upon movement of locking device 330 to its lock-on secondary spring 350 is moved toward arm 344 of the locking device to permit ridge 348 to move beneath lip 324 of trigger 300. The viasing force exerted by integral leaf spring 310 of the trigger maintains lip 322 in engagement with ridge 348 to lock the trigger in its operative position.

When it is desired to terminate the lock-on operation of the trigger mechanism, the operator raises trigger 300 slightly to disengage its lip 324 from ridge 348 of locking device 330. Upon disengagement of lip 322 and ridge 348, secondary spring 350 exerts a sufficient return bias on locking device 330 to pivot the locking device in a counterclockwise direction to move finger 346 out of the path of movement of the trigger. Thus, upon release of trigger 300 by the operator, the trigger is free to return to its downward, inoperative position. Locking device 330 is thereafter automatically returned to its initial, lock-off position by primary spring 340.

Referring to FIG. 12, a fourth alternative embodiment of the trigger mechanism includes a trigger, generally 400, comprising a finger engageable portion 402 which extends downwardly through an opening provided in the bottom of the power tool handle. An arm 404 projects forwardly from the finger engageable portion. Arm 404 terminates in a collar 406 pivotally mounted on a pin 408 projecting inwardly from the interior of the power tool handle. A primary leaf spring 410 and a secondary leaf spring 412 project upwardly from collar 408. In addition, a finger 414 projects upwardly from arm 404 and is provided with a flat, lock-off surface 416 and a sharp, downwardly projecting lock-on member or lip 418. An integral leaf spring 420 extends rearwardly from finger engageable portion 402 of the trigger and is received in a notch 422 provided on the handle.

A switch 424 including an actuator 426 is mounted on the handle above finger engageable portion 402 of the trigger. Switch actuator 426 is normally biased downward to an off position and is movable upward to an on position to actuate the switch and operate the power tool motor.

The trigger mechanism of FIG. 12 also includes a pivotal locking device, generally 430, including a cylindrical body 432 mounted on a pivot pin 434 projecting inwardly from the interior of the power tool handle. A stem 436 extends upwardly from cylindrical body 432 through an opening provided in the top of the handle. A button 438 is provided at the top of stem 436 to enable an operator to pivot the locking device 430 about its pivot pin 434. The locking device also includes a first, elongated arm 439 projecting downwardly from cylindrical body 432 and including a laterally projecting finger 440. In addition, a second, relatively short arm 442 projects from cylindrical body 432 and is located between primary spring 410 and secondary spring 412 of the trigger.

In the operation of the trigger mechanism of FIG. 12, primary spring 410 and secondary spring 412 normally bias locking device 430 into a lock-off position. With locking device 430 in its lock-off position, finger 440 of the locking device is located in the path of movement of finger 414 above its lock-off surface 416 to prevent upward movement of the trigger to its operative position. When it is desired to unlock the trigger for movement to its operative position, the operator engages and moves button 438 rearward, as indicated by arrow 444, to pivot locking device 430 in a counterclockwise direction to move the locking device to its unlock position (indicated in phantom lines) against the biasing action of primary spring 410. With locking device 430 in its unlock position, the operator can raise finger engageable portion 402 of trigger 400 to its operative position to pivot the trigger about pin 408 and move actuator 426 upward to actuate switch 424 and operate the motor. With trigger 400 in its operative position, both primary and secondary springs 410 and 412 are shifted to the positions shown in phantom lines. Thus, the biasing action of spring 410 on arm 442 is relaxed and locking device 430 cannot return to its original, lock-off position until the trigger is released.

If it is desired to lock trigger 400 in its operative position, the operator engages and moves button 438 forward to pviot locking device 430 in a clockwise direction against the biasing action of secondary spring 412 to a lock-on position with finger 440 of the locking device located underneath lip 418 of the trigger. The operator can then release trigger 400 which, under the action of integral leaf spring 420, is biased downward to maintain engagement between lip 418 and finger 440. When it is desired to terminate lock-on operation of the trigger memechanism, the operator raises trigger 400 slightly to disengage lip 418 and finger 440. Upon disengagement of lip 418 and finger 440, secondary spring 412 automatically pivots locking device 430 in the counterclockwise direction to move finger 440 out of the path of movement of finger 414 and lip 418 of the trigger. Upon release of trigger 400 by the operator, integral leaf spring 420 returns the trigger to its downward, inoperative position and primary spring 410 automatically returns locking device 430 to its lock-off position wherein arm 439 is positioned above finger 414 in registration with lock-off surface 416 to lock the trigger in its inoperative position.

Referring to FIG. 13, a fifth alternative embodiment of the trigger mechanism includes a trigger, generally 500, having a finger engageable portion 502 which extends downwardly through an opening provided in the bottom of the power tool handle. An arm extends rearwardly from the finger engageable portion. The remaining rearward structure of the trigger is not illustrated, but it can be substantially the same as the structure of trigger 300 of FIG. 11. Finger engageable portion 502 is hollow and includes a thick front wall 506 having a flat upper surface 508 for movement into engagement with an actuator 510 of a switch 512. Actuator 510 is normally biased downward to an off position and is movable upward to an on position to actuate the switch and operate the power tool motor. An arm 514 projects forwardly from the front edge of trigger 500. An opening 516 is provided in arm 514 and a sharp, downwardly facing locking member or lip 518 is formed at the outer edge of the arm.

The trigger mechanism of FIG. 13 also includes a pivotal locking device, generally 530, including a cylindrical body 532 mounted on a pivot pin 534 extending inwardly from the interior of the power tool handle. A manually operable button 536 is formed integrally with cylindrical body 532 and projects upward through an opening provided in the top of the handle to enable an operator to pivot locking device 530 about its pivot pin 534. Locking device 530 also includes first and second arms or leaf springs 538 and 540, respectively, extending downwardly from cylindrical body 532. First arm 538 supports an L-shaped locking member 542 at its lower end having upper and lower surfaces 544 and 546, respectively. The power tool handle includes a vertical rib 548 projecting inwardly from the interior of the handle with a flange 550 extending perpendicularly from the rib and located above upper surface 544 of locking member 542. Second arm 540 is provided with a lower hook end 552.

In the operation of the trigger mechanism of FIG. 13, trigger 500 is normally biased toward its downward, inoperative position by its integral leaf spring (not shown), and locking member 530 is normally located in a lock-off position. With locking device 530 in its lock-off position, locking member 542 is located between the upper, lock-off surface of arm 514 of the trigger and flange 550 of the power tool handle. If the operator attempts to move finger engageable portion 502 of the trigger upward, its arm 514 moves into engagement with lower surface 546 of locking member 542 to urge upper surface 544 of the locking member into contact with flange 550 and prevent upward movement of the trigger to its operative position. When it is desired to unlock the trigger mechanism, the operator engages and moves button 536 backward, as indicated by arrow 554, to pivot locking device 530 in a counterclockwise direction to an unlock position with locking member 542 out of the path of movement of arm 514 of trigger 500 and in registration with opening 516. The operator can then raise finger engageable portion 502 of the trigger to its operative position (indicated in phantom lines) to move actuator 510 upward to actuate switch 512. Upon upward movement of trigger 500 to its operative position, the lower end of locking member 542 moves into opening 516 formed in arm 514 of the trigger. With the lower end of locking member 542 received in opening 516, locking device 530 cannot return to its initial, lock-off position until trigger 500 returns to its downward, inoperative position.

If it is desired to lock trigger 500 in its operative position, the operator engages and moves button 536 forward, as indicated by arrow 556, to pivot locking device 530 in a clockwise direction to a lock-on position. Since locking member 542 is located within opening 516, the extent of its clockwise movement is limited by the inner edge of the opening. Thus, as locking member 530 is rotated in a clockwise direction, primary leaf spring 538 produces a return bias force urging the locking member in the opposite direction. The operator pivots locking member 530 clockwise until hook end 552 of secondary leaf spring 540 engages lip 518 of the trigger. At this time, the operator can release both trigger 500 and button 536 of the locking device without movement of the trigger back to its inoperative position. The downward bias force exerted on trigger 500 by its integral leaf spring (not shown) maintains engagement between lip 518 of the trigger and hook end 552 of the locking device.

When it is desired to terminate lock-on operation of the trigger mechanism, the operator moves finger engageable portion 502 of the trigger slightly upward to disengage lip 518 of the trigger and hook end 552 of the locking device. Upon disengagement of lip 518 and hook end 552, the return bias force produced by primary leaf spring 538 pivots locking device 530 in a counterclockwise direction to move hook end 552 from beneath lip 518 of the trigger. If the operator then releases trigger 500, its leaf spring (not shown) returns the trigger to its downward, inoperative position. As the trigger moves downward, locking member 542 is moved out of opening 516, and locking device 530 is biased to its initial, lock-off position to move locking member 542 to its initial position between arm 514 of the trigger and flange 550 of the power tool handle.

Referring to FIG. 14, a sixth alternative embodiment of the trigger mechanism includes a trigger, generally 600, comprising a finger engageable portion 602 which extends downwardly through an opening provided in the bottom of the power tool handle. An arm 604 extends rearwardly from the finger engageable portion. Arm 604 terminates in a collar 606 which is pivotally mounted on a pin 608 extending inwardly from the interior of the handle. An elongated, integral leaf spring 610 extends forwardly from collar 606. A plurality of pins 612, 613 and 614 is provided on the interior of the handle. The free end of leaf spring 610 is located between pins 612 and 613. The leaf spring is slightly bent to exert a bias force on trigger 600 to urge its finger engageable portion 602 into a normally downward, inoperative position. Finger engageable portion 602 is hollow and includes a first ledge 616 formed at its front edge for engaging an actuator 618 of a switch 620. Switch actuator 618 is normally biased downward to an off position and is movable upward to an on position to actuate the switch and operate the power tool motor. A second ledge or lock-off surface 622 is provided at the rear edge of finger engageable portion 602, and a lock-on member or finger 624 projects downward from ledge 622.

The trigger mechanism also includes a locking device, generally 630, including a cylindrical body 632 mounted on a pivot pin 634 projecting inwardly from the interior of the handle. A stem 636 extends upwardly from cylindrical body 632 through an opening provided in the top of the handle. A manually engageable button 638 is provided at the top of stem 636 to enable the operator to pivot locking device 630 about pivot pin 634. A locking arm 640 extends downwardly from cylindrical body 632 and terminates in a hook end 642 having a flat, bottom surface 644. In addition, an integral leaf spring 646 projects from cylindrical body 632 and is received between pins 613 and 614.

In the operation of the trigger mechanism of FIG. 14, integral leaf spring 646 normally maintains locking member 630 in a lock-off position with locking arm 640 in registration with lock-off surface 622 of trigger 600. If the operator attempts to raise finger engageable portion 602 of the trigger from its inoperative position, bottom surface 644 of locking arm 640 engages lock-off surface 622 and prevents movement of the trigger to its operative position. When it is desired to unlock the trigger mechanism, the operator engages and moves button 638 rearwardly, as indicated by arrow 648 (FIG. 15), to rotate locking device 630 in a clockwise direction to move the locking device to an unlock position wherein locking arm 640 is moved out of the path of movement of lock-off surface 622 of the trigger. The operator can then raise finger engageable portion 602 of the trigger upward to its operative position to move actuator 618 upward to actuate switch 620. As shown in FIG. 16, the operator can then release button 638 to allow integral leaf spring 646 to bias locking device 630 toward its initial, lock-off position. With trigger 600 in its operative position, however, hook end 642 of locking arm 640 is urged into engagement with the front edge of finger 624 to prevent locking device 630 from completely returning to its lock-off position.

If it is desired to lock trigger 600 in its operative position, the operator raises finger engageable portion 602 slightly from the position shown in FIG. 16 to move finger 624 of the trigger above hook end 642 of the locking device. At the same time, the operator engages and moves button 638 forward, as indicated by arrow 650 (FIG. 17), to pivot locking device 630 in a clockwise direction to a lock-on position with hook end 642 of arm 640 located below lock-on finger 624 of trigger 600. The operator then allows the trigger to move slightly downward to move projection 624 into engagement with hook end 642. With the trigger mechanism in its lock-on position (FIG. 17), the operator can release both finger engageable portion 602 of the trigger and button 638 of the locking device without terminating operation of the motor.

When it is desired to terminate the lock-on operation of the trigger mechanism, the operator aises the finger engageable portion 602 of the trigger slightly to disengage its finger 624 from hook end 642 of locking arm 640. Upon disengagement of projection 624 and hook end 642, integral leaf spring 646 moves locking device 630 in a counterclockwise direction to move locking arm 640 out of the path of movement of finger 624 of the trigger. The operator then releases finger engageable portion 602 of the trigger to allow integral leaf spring 610 to return the trigger to its downward, inoperative position. When the trigger returns to its inoperative position, integral leaf spring 646 returns locking device 630 to its lock-off position (FIG. 14) to locate locking arm 640 in registration with locking surface 622 of trigger 600 to prevent upward movement of the trigger to its operative position. The trigger is thus automatically locked in its inoperative position to prevent inadvertent operation of the power tool.

The embodiments of FIGS. 10-14 provide trigger mechanisms having automatic lock-off and manual lock-on features. Each trigger mechanism provides two (2) distinct modes of movement for its locking device and requires a positive, intentional action, i.e., a reversal in the direction of pivotal movement of the locking device, to operate the locking device from its first mode of movement to its second mode of movement to achieve lock-on operation of the trigger mechanism. The requirement of a positive, intentional action precludes inadvertent operation of the trigger mechanism to its lock-on state.

The invention, in its broader aspects, is not limited to the specific details shown and described, and modifications may be made in the details of the trigger mechanism without departing from the principles of the present invention.

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