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| United States Patent | 3,862,697 |
| Gill , et al. | January 28, 1975 |
FRONT LOADING HYDRAULIC EXCAVATOR
Abstract
There is disclosed a hydraulic excavator having linkage providing for a front loading arrangement whereby the bucket opens away from the vehicle. The linkage is arranged to maintain a substantially fixed preselected attitude of the bucket with respect to the boom upon movement of the stick about its pivotal connection to the boom. Further control means are provided to maintain a preselected attitude of the bucket with respect to a fixed plane upon movement of the boom.
| Inventors: | Gill; Stephen H. (Aurora, IL), Knell; Harvey A. (Joliet, IL), Tucker, III; Joseph M. (Aurora, IL) |
| Assignee: |
Caterpillar Tractor Company
(Peoria,
IL)
|
| Appl. No.: | 05/283,621 |
| Filed: | August 24, 1972 |
| Current U.S. Class: | 414/700 ; 414/694; 414/917 |
| Current International Class: | E02F 3/43 (20060101); E02F 3/42 (20060101); E02f 003/86 () |
| Field of Search: | 214/138,763,770,DIG.10 |
| 3028026 | April 1962 | Palmberg |
| 3220581 | November 1965 | Pederson |
| 3487968 | January 1970 | Long |
| 3521781 | July 1970 | Holsinger |
| 3536216 | October 1970 | Brownell |
Assistant Examiner: Mannix; J.
Attorney, Agent or Firm:
What is claimed is:
1. A hydraulic excavator, comprising:
a vehicle having a mobile carriage and a rotary platform supported on said carriage;
a boom pivotally supported at one end on said rotary platform for movement about a horizontal axis;
a stick pivotally connected at one end to the outer end of said boom;
a bucket pivotally connected to the other end of said stick;
a hydraulic jack pivotally connected at one end to said boom inboard of said stick and at the other end to operate said bucket, said jack and said stick together with said boom and said bucket forming a four bar linkage;
means including a master cylinder operatively connected to be operated by said boom, and
means operatively communicating pressurized fluid from said master cylinder to said bucket jack in response to pivotal movement of said boom to maintain said bucket in a substantially constant preselected attitude.
2. The excavator of claim 1 wherein the head end of said master cylinder communicates with the head end of said bucket jack; and,
the rod end of said master cylinder communicates with the rod end of said bucket jack.
3. The excavator of claim 2 wherein said bucket opens away from said vehicle.
4. A bucket linkage and control system for an excavator vehicle having ground engaging translation means, comprising:
a boom for pivotal connection at one end to a vehicle;
a stick of approximately the same length as the boom pivotally connected at one end to the outer end of said boom;
said boom and stick each having a length exceeding the distance of the boom pivotal connection above the ground engaging portion of said translation means;
a bucket pivotally connected to the other end of said stick;
a hydraulic jack for pivotal operation of each of said boom, stick, and bucket, said hydraulic jack for operation of said bucket, together with said stick, forming opposite sides of a four bar linkage and defining substantially a parallelogram when operated for level crowd;
means responsive to movement of said boom comprising a master cylinder operatively connected to be operated by movement of said boom; and
means operatively communicating pressurized fluid from said master cylinder to said bucket jack to operate same in response to pivotal movement of said boom to maintain said bucket in a substantially constant preselected attitude.
5. The invention of claim 4 wherein the connection of said bucket operating jack to said boom is spaced inboard from the connection of the stick to the end thereof.
6. The invention of claim 5 wherein said master cylinder and said bucket operating jack are in head to head communication.
7. The invention of claim 6 wherein said bucket opens away from said vehicle.
BACKGROUND OF THE INVENTION
Hydraulic excavators have come into widespread use for application in the construction industry because of their versatility. In many of these applications it is desirable that the bucket retain a preselected angle with respect to the ground when it is taking a cut and when it is being lifted for loading purposes.
This is especially so when the excavator is being operated as a loader with a front opening or front loading bucket.
The excavator applies power to the bucket for cutting and the like solely through the manipulation of linkages, with the vehicle normally kept or maintained in a stationary position. This is in contrast to the usual loader machine wherein force or power is applied to the bucket for loading purposes by translation of the vehicle itself along the ground. In other words, power is applied to the excavator bucket by means of hydraulically operated linkages, whereas power is applied to the loader type bucket by means of the driving wheels of the vehicle. Thus, the movement of the bucket in an excavator is controlled during its operation through the manipulation of the linkage system.
The application of power to the bucket by means of the linkage system requires careful and precise control of the linkage itself in order to achieve proper manipulation of the bucket. An excavator normally employs a scissors-like linkage arrangement having a boom pivoted at one end of the excavator vehicle, and a stick pivoted at one of its ends to the outer end of the boom, and a bucket pivoted to the outer end of the stick. Hydraulic rams or motors are operatively connected for operation of each of the boom, stick and bucket, and are each provided with a separate control valve manipulated by the operator to control the respective motor. To achieve operations requiring the taking of a substantially level cut, all three of the valves must be manipulated simultaneously by the operator. This requires diligence, experience and concentration by the operator. Such diligence and concentration hasten the fatigue of the operator, resulting in his inefficient handling of this operation.
Another problem with such excavators is that due to the geometry of the linkage, the attitude or angle of the bucket relative to the ground increases as the boom is raised. In order to prevent the load from being spilled over the back of the bucket, the operator must continually manually control the bucket attitude throughout the full range of this movement. This adds to the operator's work and necessary concentration, further increasing his fatigue and decreasing his efficiency. The prior art approach to bucket level control during crowding movement of the stick is exemplified by U.S. Pat. No. 3,166,205, issued Jan. 19, 1965 to W. D. Symmank; U.S. Pat. No. 3,251,490, issued May 17, 1966 to G. Guinot; and, U.S. Pat. No. 3,327,880, issued June 27, 1967 to E. C. Brown. A similar arrangement is shown in British Specification No. 1,200,133.
The prior art approach to bucket attitude control in conventional loader systems is exemplified by U.S. Pat. No. 2,820,555, issued Jan. 21, 1958 to H. F. Lessman; U.S. Pat. No. 3,028,026, issued Apr. 3, 1962 to J. A. Palmberg; and, U.S. Pat. No. 3,220,581, issued Nov. 30, 1965 to C. O. Pedersen, et al. Australian Patent No. 242310, accepted 24th Dec. 1962 illustrates another approach to this problem.
While the disclosed systems generally provide an acceptable solution to bucket attitude control during movement of one or the other of the boom or the stick, they fail to provide attitude control during combined movement of the boom and the stick. These prior art arrangements also fail to provide a single system having attitude control operative with movement of either one of the stick or the boom.
SUMMARY AND OBJECTS OF THE INVENTION
It is a primary object of the present invention to provide a hydraulic excavator linkage system that is operative to maintain bucket attitude control automatically during crowding movement of the excavator stick.
Another object of the present invention is to provide linkage and control means for an excavator that is operative to automatically maintain attitude control during movement of the boom structure.
A further object of the present invention is to provide an excavator linkage and control system having means operative to automatically maintain the attitude of the bucket during movement of either one or both of the boom and stick.
In accordance with the present invention, there is provided hydraulic excavator linkage especially suitable for front loading buckets having linkage means operative to maintain bucket attitude during crowding movement of the stick. Control means responsive to movement of the boom is provided to maintain the bucket in a preselected attitude during this movement.
BRIEF DESCRIPTION OF THE DRAWINGS
The above and other objects and advantages of the present invention will become apparent from the following specification when read with reference to the accompanying drawings, wherein:
FIG. 1 is a side elevational view of an excavator embodying the linkage and control means of the present invention with the linkage shown in the fully retracted position;
FIG. 2 is a view like FIG. 1 showing the linkage in the fully extended position;
FIG. 3 is a view, taken generally along lines III--III of FIG. 2; and,
FIG. 4 is a schematic of a hydraulic control system of the present invention.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
Referring now to the drawings, and particularly to FIGS. 1 and 2, there is illustrated a bucket actuating linkage generally designated by the numeral 10, operatively supported on a suitable vehicle 12 to form a hydraulic excavator which further comprises an upper frame or platform 14 rotatably mounted on a track undercarriage 16 by suitable bearing means 18.
The bucket actuating linkage comprises a boom 20 having one end pivotally connected to the frame at 22, with a pair of hydraulic hoist or lift jacks 24 operatively connected between the frame and the boom for controlling the pivotal movement of the boom 20 about pivot 22. The jacks are individually disposed on and connected to opposite sides of the boom (FIG. 3). The term "hydraulic jack" is used herein in the usual sense to refer generally to the well known linear acting hydraulic motor, also commonly known as a hydraulic cylinder.
The bucket linkage includes a stick 26 having one end pivotally connected at 28 to the outer end of the boom 20 and movable about pivot 28 by a hydraulic crowd jack 30, pivotally connected to the boom at 32 and to the stick at 34. The crowd jack 30 is disposed below the boom and offset to one side of the center line of the boom (FIG. 3) to provide room for a master cylinder, as discussed later.
A bucket 36 is pivotally mounted at 38 to the lower end of the stick 26 and controlled in its pivotal movement about pivot mount 38 by a pair of spaced hydraulic bucket control jacks 40 pivotally connected to the boom at a pivot 42. The pivot 42 is spaced from the outer end of boom 20, and disposed intermediate pivots 22 and 28. The rods of the bucket control jacks 40 are operatively connected at 44 to a wrist linkage 46, which includes links 48 and 50 pivotally connected respectively to the bucket at 52 and stick at 54.
The bucket jacks and stick form opposite sides of a substantially parallelogram configuration. The wrist linkage 46 forms a third side of the parallelogram, and the portion of the boom between pivots 28 and 42 forms the fourth side. This linkage is not a true parallelogram at all times, since the link defined by jacks 40 varies in length. The link 50 may also be longer than the distance between pivots 28 and 42, in order to maintain an adequate lever arm on the bucket.
This arrangement, with the bucket control jacks mounted to the boom, gives the crowd cylinder linkage approximately 30% more force capability than the usual stick mounted cylinder arrangements. This will be apparent from a comparison of the force diagram for the two linkage arrangements.
A hydraulic jack 56, hereinafter referred to as a master cylinder, is connected between the frame and the boom at pivots 58 and 60, respectively. The master cylinder is disposed below the boom and offset from the crowd jack 30 (see FIG. 3).
Although the term "master cylinder" may not be truly accurate, it is believed that the term better distinguishes the function or operation of this element in the system. The master cylinder 56 may be considered to function as a pump with the fluid therein being forced from alternate sides of the piston therein to alternate sides of the pistons of the bucket jacks 40. This action takes place in response to movement of the boom 20 with force transmitted from the boom to the cylinder.
As shown in the schematic of FIG. 4, the rod end of master cylinder 56 communicates with the rod ends of bucket control jacks 40, and the head end communicates with the head end of the jacks 40. Primary operation of the bucket jacks is controlled by a selector valve 62 which is selectively operable to direct pressurized fluid from a pump 64 to either side of jacks 40 via lines 66 and 68, and from either side thereof to sump 70. The master cylinder 56 and the jacks 40 must be selected to have the appropriate volume for the desired relative movement.
OPERATION
At the start of the dig operation, the bucket actuating linkage 10 and bucket 36 are positioned as shown by solid lines on FIG. 1. The crowd jack 30 is then extended, causing the stick to pivot at 28 and the bucket to move forwardly to the broken line position on FIG. 1. The bucket control jacks 40 act substantially as solid links during this phase, and cause the bucket to rotate clockwise about pivot 38 such that the bucket remains substantially level.
To maintain a level cut, the hoist jacks 24, under operator control, are extended slightly during the initial portion of the cut, and then retracted to lower the boom during the remaining portion of the cut. Since the master cylinder 56 is also retracted when the boom is lowered, the fluid from the head end of the master cylinder is communicated to the head ends of the bucket control jacks, causing them to extend slightly. (The control valve 62 shown on FIG. 4 is in the closed condition shown.) However, the geometry of the substantially parallelogram type linkage formed by the bucket jacks 40, stick 26, wrist linkage 46, and the boom portion between pivots 28 and 42 compensates for such extension, to maintain the bucket in the level position.
At the end of the crowd stroke, the bucket control jacks are then extended to curl the bucket counterclockwise about pivot 38 to the carry position shown by solid lines on FIG. 2. The hoist jacks 24 are then extended, pivoting the boom 20 about pivot 22, and raising the bucket to the elevated position shown by broken lines on FIG. 2. Raising the boom causes the master cylinder to extend, and the fluid from the rod end of the cylinder to be communicated to the rod end of the bucket control jacks 40. This causes jacks 40 to retract, pivoting the bucket clockwise about pivot 38, with the result that the attitude of the bucket remains substantially constant relative to the ground as the bucket is raised.
The bucket is dumped by retraction of the bucket control jacks, and the bucket, stick and boom are returned to the start dig position to repeat the loading cycle.
Thus, it is readily apparent from the above description that there is disclosed a novel combination of bucket control linkage and control means for an excavator that is operative to maintain a preselected bucket attitude during both crowding and lifting of the bucket. While a single embodiment has been disclosed, it is to be understood that this invention is limited only by the scope of the appended claims.
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