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United States Patent 3,684,842
Boulanger August 15, 1972

PUSHBUTTON KEYBOARD SWITCH ASSEMBLY WITH IMPROVED OVER CENTER DIAPHRAGM CONTACT

Abstract

A selectively energizable keyboard system is disclosed including a plurality of selectively actuatable pushbutton members having exposed surfaces adapted to be symbolized in accordance with electronic functions generated by actuation of the pushbutton members, and having opposed surfaces adapted to transmit force in response to actuation. A plurality of conductive elements are supported in registration with the opposed surfaces of the pushbutton members, each having a dished surface of curvature when in an unactuated condition and adapted to be deflected into an over-center position in response to application of force by a pushbutton member. A conductive member having a plurality of contact areas in electrical contact with the conductive elements is arranged adjacent the set of conductive elements. In addition, a plurality of conductive paths are arranged at a surface of a support member facing the conductive member. Each of the conductive paths is adapted to be electrically connected to the conductive member through one of the conductive elements, when the conductive element is deflected into its over-center position.


Inventors: Boulanger; Henry J. (Cumberland, RI)
Assignee: Texas Instruments Incorporated (Dallas, TX)
Appl. No.: 05/051,464
Filed: July 1, 1970


Current U.S. Class: 200/5R ; 200/5A; 200/516; 341/34; 968/450
Current International Class: H01H 13/70 (20060101); G04C 3/00 (20060101); H04M 1/23 (20060101); H01h 013/26 ()
Field of Search: 200/5R,5A,46,86R,159B 340/166R

References Cited

U.S. Patent Documents
3600528 August 1971 Leposavic
2262777 November 1941 Roper
3541515 November 1970 Walter et al.
3472974 October 1969 McGough
3308253 March 1967 Krakinowski
3551616 December 1970 Juliusburger et al.
3290439 December 1966 Willcox
Foreign Patent Documents
1,806,241 Aug., 1969 DT

Other References

IBM Technical Disclosure Bulletin, R. H. Harris et al., "Switch," Dec. 1969, Vol. 12, No. 7, p. 1130.

Primary Examiner: Scott; J. R.

Claims



I claim:

1. A selectively energizable keyboard system comprising

a set of selectively operable pushbutton members each movable in one direction from a retracted to an activating position, each of said pushbutton members having an exposed surface adapted to receive the application of a preselected mechanical force to effect movement into said activating position and having an opposed surface adapted to transmit said force,

a set of conductive elements in registration with respective opposed surface of said pushbutton members, each of said elements having a dished surface of curvature when in an unactuated condition, said surface being in abutment with said opposed surface of one of said pushbutton members and adapted to be deflected into an over-center position in response to the application of said preselected force transmitted by actuation of said pushbutton member,

a generally planar conductive member disposed adjacent said set of conductive elements, said conductive member including a plurality of contact sections arranged in electrical contact with said conductive elements, and

a support member having a plurality of conductive paths arranged at a surface thereof in spaced facing relationship with said plurality of sections of said conductive member, selected ones of said conductive paths being electrically connected to said conductive member through a bridging electrical connection established between said conductive member and one of said conductive elements only when said conductive element is in an over-center position.

2. A system in accordance with claim 1 wherein means are provided for supportingly carrying and restraining said set of conductive elements against lateral movement relative to said opposed surfaces of said pushbutton members and relative to said conductive paths to assure positive electrical contact between said conductive elements and said selected conductive paths through said conductive elements in response to actuation of preselected pushbutton members.

3. A system in accordance with claim 1 wherein said conductive elements preclude electrical contact between said conductive paths and said conductive member until respective conductive elements are subjected to said preselected force required for deflection into its over-center position in response to actuation by an associated pushbutton member, said preselected force being at least partially stored to effect an abrupt snap-action deflection of said conductive element into its over-center position, thereby effecting a positive instantaneous electrical contact between said conductive member and said selected conductive path through said conductive element.

4. A system in accordance with claim 3 wherein said pushbutton members are adapted to be individually manually actuatable and said conductive elements are adapted to produce a tactile stimulation transmittable through said associated pushbutton member in response to the snap-action deflection into the over-center position.

5. A system in accordance with claim 3 wherein each of said conductive elements is of a generally circular configuration having a preselected diameter, said conductive member includes a plurality of generally circular apertures, said apertures being in axial registration with said conductive elements and having a diameter less than said preselected diameter but sufficient to accommodate deflection of the central portion of said conductive elements therethrough, and at least a portion of each of said conductive paths is arranged in registration with said apertures to permit the making of a bridging electrical connection between each of said paths and the conductive member through the conductive element in response to deflection thereof.

6. A system in accordance with claim 5 wherein each of said apertures in said conductive member is defined by an annular contact area circumscribing said aperture, said annular contact area being in electrical contact with an associated one of said conductive elements to effect selective electrical contact between the conductive path in registration with said aperture and said annular contact area through said conductive element.

7. A system in accordance with claim 6 wherein each of said conductive elements is provided with a generally centrally located protuberance facing one of said conductive paths through said apertures in said conductive elements to enhance electrical engagement between said conductive element, said conductive member, and said conductive path.

8. A system in accordance with claim 7 wherein a layer of insulating material is disposed intermediate said conductive member and the surface of said member at which said plurality of conductive paths are arranged, said layer of insulating material having a plurality of apertures of a preselected size in axial registration with said apertures in said conductive members and with said conductive elements, said apertures in said layer of insulation material each being of a size sufficient to permit passage therethrough of said protuberance on said conductive element into electrical contact with one of said conductive paths to effect the establishment of a bridging electrical contact between said conductive member and said conductive path when said conductive element is deflected into its over-center position.

9. A system in accordance with claim 6 wherein a generally cylindrical protrusion is provided defining said opposed surface of each of said pushbutton members for selectively engaging said conductive elements in response to actuation of said pushbutton member, said protrusion being in axial alignment with an associated conductive element and having a surface of engagement with said conductive element of a diameter having an area equal to approximately one-third of the surface area of the conductive element in order to cause snap-action deflection of said conductive element thereby effecting positive establishment of the bridging electrical contact in response to actuation of said pushbutton member.

10. A system in accordance with claim 9 wherein said pushbutton members are fabricated, at least in part, of a resilient material adapted to store energy in response to mechanical actuation, said stored energy being transmitted to an associated conductive element upon engagement with said opposed surface of said pushbutton member to produce a positive snap-action deflection of said conductive element into electrical contact with said conductive member and one of said selected conductive paths.

11. A system in accordance with claim 3 wherein each of said pushbutton members is symbolized in a manner indicative of the electronic function established by the conductive path electrically contacted by said conductive member in response to actuation of said pushbutton member.

12. A system in accordance with claim 11 wherein terminals pads are provided at preselected locations on said support member in electrical contact with said conductive paths and in registration with said conductive elements and at least one semiconductor device is provided having a plurality of circuit elements at a surface thereof adapted to be electrically coupled to selected terminal pads, said circuit elements being adapted to generate selected electrical functions in response to the electrical contact established between said conductive layer and a conductive path upon actuation of a pushbutton member.

13. A system in accordance with claim 12 wherein said conductive layer is adopted to be connected to a source of electrical power so as to effect electrical energization of selected circuit elements of said semiconductor device in response to actuation of a pushbutton member.

14. A system in accordance with claim 13 wherein means are provided for generating an indication of the electrical function represented by actuation of a pushbutton member.

15. A system in accordance with claim 13 wherein said support member for said conductive paths comprises a relatively rigid layer of insulation material, and said terminal pads include enlarged contact portions defined by integral extensions of said conductive path, said semiconductor device is supported on said rigid layer of insulation material adjacent said terminal pads, and said means for generating an electrical function are supported on said rigid layer of insulation material.

16. A pushbutton keyboard system adapted to generate electrical information in response to actuation thereof comprising

a support member having a generally planar surface at which a plurality of conductive paths are arranged in a preselected pattern and adapted to transmit electrical information in response to energization thereof,

a generally planar sheet of conductive material disposed in spaced, facing relationship with said pattern of conductive paths, said sheet of conductive material including a plurality of contact areas adapted to be selectively electrically coupled to portions of said conductive paths for effecting energization thereof,

a plurality of selectively actuatable conductive elements disposed in electrical contact with said contact areas and in selective disengagement with said portions of said conductive paths, said conductive elements being adapted to be individually deflected into a position of engagement with said portions of said conductive paths in response to the application of a preselected deflecting force thereto, thereby effecting an instantaneous bridging electrical contact between said conductive sheet and one of said conductive paths, and

means for applying the preselected deflecting force to said conductive elements including a plurality of pushbutton members adapted to be manually actuated to apply the preselected deflecting force to said conductive elements to effect deflection thereof into said position of engagement with said conductive paths, each of said pushbutton members including a force applying surface adjacent an associated conductive element and an exposed surface adapted to be symbolized in a manner indicative of the electrical information to be transmitted by the establishment of electrical contact between said conductive layer and said portion of said conductive path.

17. A system in accordance with claim 16 wherein said conductive elements are each of a generally circular configuration having a convex surface of curvature in facing engagement with the force applying surface of said pushbutton member, said convex surface being adapted to be deflected into a concave configuration in response to the application of the preselected force by said force applying surface, thereby establishing the bridging electrical contact between said conductive layer and one of said conductive paths.

18. A system in accordance with claim 16 wherein said conductive element is adapted to be deflected a maximum distance in response to the application of minimum preselected deflecting force.

19. A system in accordance with claim 17 wherein means are provided for supportingly carrying said conductive elements in a manner permitting snap-action deflection of said convex surface into a concave surface while precluding lateral movement of said conductive elements to maintain alignment between said conductive elements and said portions of said conductive paths.

20. A system in accordance with claim 19 wherein said means for supportingly carrying said conductive elements comprises a sheet of insulation material having a plurality of apertures for accommodating said conductive elements and the rims of said conductive elements are maintained in generally sealed relationship with the walls of said apertures to permit deflection of said conductive elements through said apertures in response to actuation by said pushbutton members.

21. A system in accordance with claim 20 wherein said conductive sheet is disposed between said sheet of insulation material carrying said conductive elements and said generally planar surface of said support member, said conductive sheet having a plurality of apertures in axial registration with said apertures in said sheet of insulation material, said apertures in said conductive sheet being of a smaller diameter than said apertures in said sheet of insulation material to define annular contact areas circumscribing said apertures in said sheet of conductive material, said annular contact areas being in engagement with said conductive elements and adapted to permit deflection of the central portion of the conductive elements through said apertures while restraining peripheral movement of said conductive elements.

22. A system in accordance with claim 21 wherein a spacer sheet of insulation material is provided intermediate said conductive sheet and said pattern of conductive paths at said generally planar surface of said support member, said spacer sheet having a plurality of apertures in axial registration with said apertures in said sheet of conductive material and exposing said portions of said conductive paths, said apertures in said spacer sheet being of a diameter equal to or less than the diameter of said apertures in said conductive sheet to maintain said conductive layer electrically insulated from said conductive paths until deflection of said conductive elements is effected to establish the bridging electrical contact between said annular contact areas of said conductive layer and said exposed conductive paths through said apertures in said spacer sheet.

23. A system in accordance with claim 22 wherein said generally conductive elements each include a dimpled protrusion extending toward said conductive paths, said protrusions being of a size less than the size of said apertures in said spacer sheet and being adapted to pass through said apertures in response to deflection of said conductive elements so as to facilitate the establishment of electrical contact with said conductive paths.

24. A system in accordance with claim 23 wherein said support member comprises a sheet of epoxy bonded glass cloth, said conductive paths comprise gold-plated copper, said spacer sheet comprises polyethylene terephthalate resin, said conductive sheet comprises gold-plated brass, said conductive elements comprise gold-plated type 302 stainless steel, said sheet of insulation for carrying said conductive elements comprises epoxy bonded glass cloth and said pushbutton key members comprise an elastomer.

25. A system in accordance with claim 24 wherein said gold-plated copper conductive paths have a thickness of approximately 0.003 inches, said spacer sheet has a thickness of approximately 0.0045 inches, said gold-plated brass conductive sheet has a thickness of approximately 0.002 inches, said conductive elements have a thickness of approximately 0.004 inches, said sheet of epoxy bonded glass cloth has a thickness of approximately 0.015 inches, and said dimpled protrusion extends approximately 0.004 inches from the surface of said conductive element.

26. A system in accordance with claim 22 wherein a plurality of terminal members are provided at preselected locations adjacent one end of said support layer in electrical contact with said conductive paths, at least one semiconductor device is disposed adjacent said one end of said support layer having a plurality of circuit elements at a surface thereof electrically coupled to selected terminal members, said circuit elements being adapted to perform electrical functions in response to the establishment of electrical contact between said conductive sheet and one of said conductive paths upon deflection of a conductive element, thereby generating the electrical information.

27. A system in accordance with claim 26 wherein said conductive sheet is adapted to be electrically connected to a source of electrical power so as to selectively supply electrical power to said circuit elements upon the establishment of contact between said conductive sheet and said conductive paths through said conductive elements.

28. A system in accordance with claim 27 wherein means are provided supported by said support member electrically coupled to said semiconductor device for generating an indication of the electrical information generated by actuation of one of said pushbutton members.

29. In an electronic calculator;

a pushbutton keyboard system adapted to enter electrical information in response to actuation, said keyboard system including a support member having a generally planar surface at which a plurality of conductive paths are arranged in a preselected pattern and adapted to transmit electrical information in response to energization thereof, a generally planar sheet of conductive material disposed in spaced, facing relationship with said pattern of conductive paths, said sheet of conductive material including a plurality of contact areas adapted to be selectively electrically coupled to portions of said conductive paths for effecting energization thereof, a plurality of selectively actuatable conductive elements disposed in electrical contact with said contact areas and in selective disengagement with said portions of said conductive paths, said conductive elements being adapted to be individually deflected into a position of engagement with said portions of said conductive paths in response to the application of a preselected deflecting force thereto, thereby effecting an instantaneous bridging electrical contact between said conductive sheet and one of said conductive paths, and means for applying the preselected deflecting force to said conductive elements including a plurality of pushbutton members adapted to be manually actuated to apply the preselected deflecting force to said conductive elements to effect deflection thereof into said position of engagement with said conductive paths, each of said pushbutton members including a force applying surface adjacent an associated conductive element and an exposed surface adapted to be symbolized in a manner indicative of the electrical information to be transmitted by the establishment of electrical contact between said conductive layer and said portion of said conductive path;

at least one semiconductor device supported on said support member, said semiconductor device having a plurality of circuit elements at a surface thereof, electrically coupled to said conductive paths, said circuit elements being adapted to generate electrical signals in response to electrical information applied thereto from said conductive paths upon the establishment of electrical contact between said conductive sheet and said conductive paths; and

indicating means supported by said support member in communication with said semiconductor device for providing an indication of the electrical signals generated in response to information applied to said circuit elements.

30. A multiple switching system comprising in combination:

a plurality of spaced actuating members selectively movable from a first to a second position;

a plurality of contact elements respectively contiguous with said actuating members, each of said elements having a double curved outer surface with a selected area thereof being contiguous to a selected portion of said actuating members, said elements being selectively movable from a first to a second position in response to selective movement of said actuating members;

a support member adjacent to but spaced from said elements and having a plurality of spaced contacts formed thereon respectively positioned adjacent to but spaced from said elements;

an array of conductive areas respectively arranged intermediate said elements and said contacts; and

means for holding said actuating members, said elements, said support member, and said conductive areas in relative position;

whereby when said actuating members are selectively moved from their first to their second position, said respective element is moved from its first to its second position into contact with its respective spaced contact and electrically connects its respective conductive area to its respective spaced contact and when said actuating members are selectively moved from their second to their first position, said respective element automatically moves from its second to its first position out of contact with its respective spaced contact and electrically disconnects its respective conductive area from its respective spaced contact.

31. The multiple switching system of claim 30 wherein each of said contact elements have an over-center second position when a selected portion thereof is subjected to an axial force, said elements automatically returning to their first position when said axial force is removed.

32. The multiple switching system of claim 31 wherein each of said contact elements are segments of an oblique spheroid.
Description



The present invention relates generally to keyboard systems and more particularly is directed to an improved pushbutton keyboard system for establishing positive electrical contacts in response to actuation.

Various types of keyboard systems have been developed in recent years utilizing pushbutton members which are appropriately symbolized in a manner indicative of a numeric of mathematical function which is generated by depression of the pushbutton member to establish electrical contact with various circuit elements in order to achieve the function desired. Typically, such pushbutton members are spring biased in a retracted position and are adapted to be manually depressed to establish the desired electrical contact. However, various problems have arisen in connection with such arrangements. For example, the spring biasing arrangement may cause operator fatigue in certain instances. Alternatively, the bias may be too weak to provide sufficient sensitivity to produce tactile feedback to the operator indicative of the establishment of the requisite electrical contact. Similarly, such arrangements may not produce the abrupt positive electrical contact desirable to achieve the desired electrical operation, and may be susceptible to problems of contact bounce, particularly when the keyboard system is utilized for operating devices, such as electronic calculators, in which rapid actuation of the pushbutton members is contemplated and in which the establishment of erroneous electrical contacts causes inaccurate results.

Various devices have been proposed in order to alleviate such difficulties and achieve abrupt positive electrical contact in response to actuation of a pushbutton member, including devices which produce an audible indication in response to actuation, devices utilizing various types of sliding arrangements so as to effect wiping contact, etc. However, certain problems have still arisen. For example, the provision of audible indication of operation may result in an intolerable noise level, when a large number of such devices are being utilized in a relatively enclosed environment, or alternatively may make the device unsuitable for use in a relatively noisy environment, in which the audible indication could not be sensed. In addition, the provision of sliding type arrangements to effect wiping contact, may be subject to durability problems in view of eventual mechanical wear of the contacts, the presence of contaminants which may interfere with electrical contact, etc.

Moreover, an increasing need has developed in recent years for fabricating devices of this nature in which a high degree of miniaturization is achieved, as technological advances have permitted the fabrication of extremely small electronic systems. Such a need has become particularly critical in view of the current availability of semiconductor devices including an enormous number of circuit functions on material which may occupy less space than one of the pushbutton members itself. Since the associated electronic circuitry required for electrical operation occupies a relatively insignificant amount of space, it becomes imperative also to achieve an analogous reduction in size of the keyboard.

It is an object of the present invention to provide an improved keyboard system adapted for selectively establishing electrical contacts in response to mechanical actuation thereof.

It is another object of the present invention to provide an improved pushbutton keyboard system in which actuation of individual pushbutton members establishes a positive electrical contact while providing a tactile feedback as an indication of the establishment of contact.

It is still another object of the present invention to provide an improved pushbutton keyboard system in which a bridging electrical contact is established between conductive portions of the system by the establishment of a maximum deflection of a bridging contact element in response to the application of a minimum amount of force.

It is a further object of the present invention to provide an improved miniaturized pushbutton keyboard system which is extremely rugged and durable, is capable of effecting the generation of electrical information in response to actuation thereof, and is adapted for incorporation in an electronic calculator.

Various additional objects and advantages of the present invention will become readily apparent from the following detailed description and accompanying drawings wherein:

FIG. 1 is a plan view of one embodiment of a selectively energizable keyboard system in accordance with the present invention;

FIG. 2 is a vertical sectional view taken along lines 2--2 of FIG. 1;

FIG. 3 is a partial sectional view taken along lines 3--3 of FIG. 2;

FIG. 4 is a sectional view taken along lines 4--4 of FIG. 2;

FIG. 5 is a graph of force vs. deflection illustrating the mechanical energy produced by actuation of a pushbutton member;

FIG. 6 is a partially broken away perspective view illustrating an electronic calculator incorporating the keyboard system; and

FIG. 7 is an exploded perspective view illustrating an alternative embodiment of a keyboard system similar to that illustrated in FIGS. 1-4.

Referring generally to the drawings wherein corresponding elements in the various views are indicated by common reference numerals, and in particular, to FIGS. 1-4, a keyboard system 8 in accordance with the present invention generally includes a non-conductive support member 10 having a plurality of conductive paths 12 arranged in a preselected pattern at a surface thereof, each of the conductive paths including an enlarged contact portion or pad 14 at one end and a terminal member 16 adjacent an opposite end thereof. Each of the conductive paths 12 is adapted to transmit electrical signals or information upon the establishment of an electrical contact with the contact pad 14, as will be subsequently explained in detail. A sheet or layer 18 of conductive material is disposed in overlying relationship with the surface of the support member 10 on which the conductive paths 12 are arranged, and is separated and electrically insulated therefrom by a relatively thin sheet of insulation material 20, having a plurality of apertures 21, which expose the contact pads 14. Electrical engagement is selectively established between the pads 14 and the conductive layer 18 in response to deflection of a plurality of conductive elements 22, which are arranged in electrical contact with the conductive layer 18 and adapted to be deflected in response to the application of a mechanical force to provide a bridging electrical contact between the conductive layer 18 and one of the contact pads 14. Actuation of the conductive elements 22 to effect deflection is accomplished by the application of mechanical force to one of a plurality of pushbutton members 26, one of such pushbutton members being associated with each of said conductive elements 22. The pushbutton members 26 are preferably maintained in abutment with the conductive elements 22 and are adapted to be moved from a retracted to an activating position which effects the establishment of the bridging electrical contact between the conductive layer 18 and one of the conductive pads 14.

More particularly, the support layer 10 is fabricated of a relatively rigid, non-conductive material and is adapted to support the keyboard system, as well as associated electronic circuitry, power supplies, display means, etc., when the keyboard is to be incorporated in an electronic calculator unit. The sheet 18 of conductive material is of a generally planar configuration and is disposed in spaced facing relationship with the pattern of conductive paths. The sheet 18 includes a plurality of annular contact areas 28 on its surface, the annular contact areas circumscribing a plurality of apertures 30 provided in the sheet 18. The contact areas 28 are maintained in contact with each of the conductive elements 22 and are adapted to be electrically coupled to the conductive pads 14 upon actuation of a key member 26 which causes deflection of its associated conductive element 22 to form a bridging electrical contact between the contact area 28 of the conductive layer 18 and one of the conductive pads. In this regard, the apertures 30 in the conductive sheet 18 preferably have a generally circular configuration of a preselected diameter less than the size of the conductive elements 22 so as to accommodate passage therethrough of the central portion of the conductive elements 22 upon deflection, while the contact area 28 aids in restraining peripheral movement of the conductive element. Each of the conductive elements 22 is supported in axial registry with one of the apertures in the conductive layer 18 in order to effect the establishment of a bridging electrical contact between the contact area 28 and hence, with the conductive layer 18, and as associated conductive pad 14 in registration with the aperture 30 in the conductive layer. In addition, the apertures 21 in the layer of insulation material 20, which is disposed intermediate the conductive layer 18 and the conductive paths 12, preferably have a generally circular configuration and are each in axial registry with one of the apertures 30 and an associated portion of one of the conductive pads 14. The apertures 21 each have a preselected diameter which is less than or equal to the diameter of the apertures 30, and of a sufficient size to accommodate passage therethrough of the central portion of the conductive element 22 upon deflection thereof, such that electrical contact is established between the contact area 28 of the conductive layer 18 and one of the conductive pads 14 through the conductive element 22, only upon deflection thereof.

Each of the conductive elements 22 is maintained in its respective position in axial registry with one of the conductive pads 14 and with one of the pushbutton members 26, such that peripheral movement of the conductive element 22 is restrained by the contact area 28, and is also arranged such that lateral movement is restrained in order to permit the establishment of the aforementioned bridging electrical contact. In this regard, the conductive elements 22 are supportingly carried within a generally planar sheet of insulation material 34, which is disposed in overlying relationship with the conductive sheet 18 and preferably secured thereto to maintain the electrical contact between the conductive elements and the conductive sheet. More particularly, the sheet 34 includes a plurality of apertures 36 preferably of a circular configuration having a preselected diameter approximately equal to that of each of the conductive elements 22, which preferably are of a generally circular or disc-shaped configuration, so as to be accommodated within the apertures 36. Accordingly, the conductive elements are supported in close-fitting relationship within the aperture 36. In this regard, the rim of each of the conductive elements 22 preferably is sealingly received within the wall defined by an associated one of the apertures 36 and is thus restrained against lateral motion while deflection in response to an actuating force is permitted and contact with the annular contact area 28 of the underlying conductive sheet 18 is maintained. Each of the apertures 36 in the sheet 34 of insulation is in axial registry with a corresponding one of the apertures 30 in the conductive layer 18, but is of a slightly larger diameter than the aperture 30 so as to expose the contact area 28 and permit essentially continuous electrical contact to be maintained between each of the conductive elements 22 and the conductive sheet 18. Thus, upon deflection of one of the conductive elements 22 in response to the application of an actuating force by its associated pushbutton member 26, which is maintained generally in abutment with the surface thereof, the conductive element establishes a bridging electrical contact between the conductive layer 18 and the associated conductive pad 14 which is exposed through the axially aligned apertures in the various sheets of material separating the conductive sheet from the conductive pads.

Referring particularly to FIG. 2, one of the pushbutton members designated by the numeral 26a is illustrated in an actuated or depressed condition such that the conductive element, designated by the reference numeral 22a, associated therewith is in a deflected condition establishing the aforementioned bridging electrical contact between one of the contact pads and the conductive sheet 18. The individual pushbutton members 26 may be symbolized as shown, in accordance with the electrical function accomplished by establishing electrical contact between the conductive sheet 18 and one of the conductive pads so that electrical information may be transmitted along the conductive path associated with the pad to a circuit element or the like, to generate the electrical function. In FIG. 1, it may be seen that the various pushbutton members are symbolized with the digits 1-9, as well as with symbols indicative of various arithmetic operations, since the particular keyboard system illustrated is particularly adapted for use in an electronic calculator as will be explained hereinafter. Each of the pushbutton members 26, is normally in a non-operative or retracted position, and is adapted to be actuated into a contact establishing position in response to the application of a predetermined mechanical force thereto as indicated by the position of the pushbutton member 26a, as previously explained. More particularly, each of the pushbutton members 26 includes a force applying surface 38 opposite to the exposed symbolized surface, the surface 38 being arranged in abutment with a corresponding conductive element 22. In this connection, each pushbutton member preferably includes a generally cylindrical protrusion 39, integrally depending from the exposed surface for transmitting applied actuating force to the conductive element. Accordingly, upon operation of a pushbutton member 26 by the application of an actuating force, such as in response to manual depression by an operator, the pushbutton member 26 transmits the applied force through the cylindrical protrusion 39 and the surface 38 to the conductive element 22 to effect deflection thereof as shown by the position of the pushbutton member 26a to cause the conductive element to be deflected into the position which it establishes bridging electrical contact between the conductive sheet 18 and one of the conductive pads 14.

The pushbutton members are preferably fabricated of a relatively resilient material such as elastomers in order to permit the storage of a preselected amount of force within the material comprising the pushbutton member during actuation so as to achieve an abrupt and positive deflection of the conductive element. In the illustrated embodiment, the pushbutton members 26 are formed of a unitary body of material to facilitate fabrication, although other configurations may be suitable as indicated hereinafter in connection with FIG. 7. In those instances, in which the keyboard system is adapted to be manually actuated by an operator, a certain amount of force may be also stored in the flesh of the contacting finger tips of the operator so as to increase the storage of force in order to further enhance the positive deflection of the conductive element. In this regard, reference may be made briefly to the force-deflection curve of FIG. 5 in which applied force in ounces is shown plotted against deflection in thousandths of inches in connection illustrative of the deflection operation of one of the conductive elements 22. As may be seen, force and deflection initially increase in an almost linear relationship, as indicated by the portion 40 of the curve, and reach a peak at a portion 42 at which point the curve exhibits a negative slope region 44 during which deflection increases with a decreasing force eventually approaching a minimum point or valley 46 at which the relationship reverses and deflection once again increases in response to the increasing force, as shown by the portion 48 of the curve. In accordance with an important feature of the present invention, the pushbutton members are preferably arranged, as previously explained, such that a preselected amount of force is stored within the mechanism itself in order to effect deflection of the conductive element along the negative slope portion 44 of the curve illustrated in FIG. 5, and preferably at a point which approaches or is at the minimal point 46 at which maximum deflection is achieved in response to a minimum level of applied force. Such an effect is obtained as a result of the arrangement of the various elements comprising the keyboard system 8, which permits energy storage within the pushbutton member itself due to its resiliency as well as in the resilient flesh of the operator, thereby achieving deflection operation along the negative slop portion 44 at a point near or at the valley 46 of the curve.

Referring in detail to the conductive elements 22, it may be seen that each of these elements preferably is formed of a segment of a hollow body having a double curved outer surface such as a segment of an oblique spheroid and is illustrated including a generally convex surface of curvature 50, when in an unactuated or rest state. In this regard, a fundamental criteria in selecting the shape of the conductive element is that the surface has an over-center position, when its central position is subjected to an axial force, and the surface automatically returns to its original position upon removal of the force, to wit, the element has memory. It is contemplated that segments of other hollow bodies having double curved surfaces may be utilized in forming the conductive elements, such as hyperboloids, paraboloids, etc., providing the above fundamental criteria are met. The force applying surface 38 of the pushbutton member 26 is preferably arranged such that it is contiguous or in abutment with the central portion of this surface 50 and in a preferred embodiment of the present invention, the surface 38 of the pushbutton member 26 contacts approximately one-third of the surface area of the surface 50 of the element 22 during the application of force to the conductive element so as to maximize the force being applied thereto. In addition, the element 22 may be provided with a generally dimpled protuberance 52 which depends from the opposite surface thereof and is arranged in axial registry with the aperture 21 in the insulating sheet 20 and is also arranged in registry with one of the conductive pads 14 such that upon deflection of the element 22, the protuberance 52 makes a positive electrical contact with the conductive pad 14 so as to effectively establish the bridging electrical contact between the conductive pad and the conductive sheet 18 through the conductive element 22. The conductive element is arranged as shown ad described so that it may undergo a snap-action deflection into an over-center position as shown by the position of element 22a, as previously mentioned, the amount of deflection accompanying such a snap-action motion into the over-center position being sufficient to permit the bridging electrical contact to be established between the underlying conductive pad and the conductive sheet. As a result of this snap-action deflection into the over-center position, an abrupt, instantaneous and positive electrical contact is made in which contact bounce is precluded so as to avoid the possibility of inadvertent multiple electrical inputs. Furthermore, as a result of this snap-action deflection, a tactile feedback is provided which may be sensed in the fingertips of the operator actuating a particular pushbutton. Moreover, an audible acknowledgement of deflection also accompanying the snap-action deflection may be sensed by an operator to provide a further indication that a pushbutton member has been actuated to supply a desired electrical input.

Thus, it may be seen that in operation, upon actuation of a selected pushbutton member 26 by the application of a sufficient mechanical force thereto, snap-action deflection of an associated conductive element 22 is produced to cause the conductive element to be deflected into an over-center position in which its surface of curvature 50 is transformed from a convex configuration to a concave configuration, as indicated by the position of element 22a, thereby establishing a positive instantaneous bridging electrical contact between the conductive sheet 18 and an associated conductive pad so as to permit an electrical signal to be transmitted along one of the conductive paths to a terminal member 16. In this connection, it should be noted that the conductive sheet 18 may be connected, if desired, to a source of electrical energy to supply signals to a conductive pad for transmission along a conductive path to a terminal member upon the establishment of electrical contact due to deflection of a conductive element 22, the sheet 18 may be connected to a source of input information, such as a computer, etc., depending upon the use to which the system is to be put.

The support member 10 may be formed of a suitable insulating material having the conductive pattern arranged at the surface thereof, in a configuration slightly raised from the surface thereof, as shown, so as to permit the establishment of a positive electrical contact between the conductive sheet 18 and a selected conductive pad upon deflection of a conductive element 22. In this regard, the support member 10 may comprise a conventional printed circuit board formed of a relatively rigid insulating material with the conductive pattern laid down utilizing conventional techniques, such as masking, etching, engraving, etc. The insulating layer 20 may be formed of a suitable, non-reactive insulation material, such as polyethylene terephthalate, commonly sold under the trademark Mylar, and is preferably disposed in sealed relationship intermediate the conductive sheet 18 and the surface of the support board 10 at which the conductive paths are arranged. This may be accomplished by providing an adhesive backing or the like on sheet 20. The conductive sheet 18, which is disposed intermediate the insulating layer 34 and the insulating sheet 20 may be suitably bonded to the insulating layer 20 by utilizing a suitable adhesive on the underside of the conductive sheet 18 and similarly may be bonded to the insulating layer 34 utilizing a suitable adhesive arranged on the underside of the insulating layer 34. The integral sheet comprising the pushbutton members may be secured in position by an adhesive which bonds the edges thereof to the support member 10.

In one example of a device such as that shown in FIGS. 1-4 which has been fabricated, the supporting board 10 is formed of a preselected insulating material such as epoxy bonded glass cloth generally sold under the trade description G-10 by the Formica Company. This material has a thickness of approximately one-sixteenth inch while its lateral dimensions are approximately 21/4 inches .times. 3 inches. The conductive paths are laid down in a preselected pattern on the surface of the support 10, using conventional deposition techniques and are preferably formed of gold-plated copper having a thickness of approximately 0.003 inch. The insulating layer 20 disposed intermediate the surface of the support board 10 and the conductive layer 18 is fabricated of a material such as polyethylene terephthalate commonly sold under the trade namer Mylar, and has a thickness of approximately 0.0045 inch. The conductive layer 18 is formed of gold-plated brass having a thickness of approximately 0.002 inch. The insulating layer 34 which supportingly carries the conductive elements 22 is also fabricated of epoxy bonded glass cloth such as that commonly sold under the trade designation G-10 by the Formica Company. The conductive elements 22 which are restrained within the apertures 36 in the non-conductive layer 34 comprise discs of gold-plated type 302 stainless steel having a thickness of approximately 0.004 inch while the thickness of the protuberance 52 is also approximately 0.004 inch and the diameter of the disc is approximately 0.375 inch. The key members 22 are preferably fabricated of an integrally molded unit of a resilient elastomer which permits separate individual movement of each of the key members without affecting the position of other pushbutton members in view of the resiliency of the material.

Referring to FIG. 6, a keyboard system 8, such as that shown in FIGS. 1-4, is illustrated incorporated within an integral self-contained electronic calculator unit 53. More particularly, the embodiment illustrated is shown partially broken away to depict the provision of a plurality of semiconductor devices 54, such as integrated circuits. In the illustrated embodiment, the semiconductor devices 54 are supported on the same surface of the support member 10, on which the pattern of conductive paths are arranged. Each of the semiconductor devices 54 includes a plurality of circuit elements 56 at a surface thereof with selected ones of the circuit elements being electrically connected to selected terminal members 16 by the provision of suitable whisker wire leads 58. In addition, a suitable energy source (not shown) may be also supported by the board and coupled to the semiconductor devices. Suitable indicating means, including a display window 60, may be coupled to the semiconductor device 54 and arranged to provide visual indication of a particular electronic function generated in response to actuation of one of the pushbutton members 26 of the calculator unit. Similarly, if desired, other types of indicating systems could be provided such as heat sensitive paper adapted to be imprinted with information in response to actuation of a pushbutton member, a tape punching apparatus, etc. It may be noted that for the sake of simplicity, only several circuit elements 56 and whisker wire lead connections have been illustrated, but it is contemplated that semiconductor devices utilizing enormous numbers of circuit elements may be employed in order to provide a complete electronics system for a self-contained calculator unit. Thus, in operation of the electronic calculator 53 illustrated in FIG. 6, upon actuation of one of the pushbutton members 26 by depression thereof, a bridging electrical contact is established between the conductive sheet which may be coupled to a source of energy, or source of electrical information, etc., and one of the conductive pads through one of the conductive elements 22. Electrical information is then transmitted along the associated conductive path to one of the terminal members 16 and thence, to a selected one of the circuit elements 56, while appropriate output information is visually indicated in the display window 60. Additional specific details regarding the general mode of operation of electronic calculators actuated in response to the application of an electrical signal and the provision of a visual or other indication of operation are provided in various sources and accordingly, a detailed description of such operation is not set forth herein.

Referring now to FIG. 7, an alternative embodiment of keyboard system similar to that illustrated in FIGS. 1-4 is shown. This keyboard system is essentially identical to that illustrated in FIGS. 1-4, except for the provision of a different type of pushbutton member and supporting carriage therefore. More particularly, the support member 10 including the conductive pads 14, the conductive paths 12 and the terminal members arranged in a preselected pattern at the surface thereof, is generally similar to that shown in FIGS. 1-4 as is the overlying insulating layer 20, including the apertures 21 therein, exposing the conductive pads. Similarly, the conductive sheet 18, having apertures 30 therein is provided overlying the insulating layer 20 to accommodate deflection of the conductive elements 22, when the bridging electrical engagement is established between the conductive sheet 18 and one of the conductive pads 14. The insulating layer 34 having the plurality of apertures 36 therein for sealingly receiving the conductive elements 22, is also provided, although only one of the conductive elements 22 is shown for the sake of simplicity. However, rather than including a plurality of generally circular shaped pushbutton members integrally formed of a molded elastomer material such as illustrated in connection with FIGS. 1-4, a plurality of separate individual pushbutton members 64 are provided, each of which is appropriately symbolized at an exposed surface and which includes an opposed protruding surface 66, depending from the main body portion thereof and maintained in abutment with the central region of the conductive element 22 for effecting deflection in response to actuation of the pushbutton member 64. Each of the key members is supportingly carried within a support casing 68 having a generally planar surface from which the exposed surfaces of the pushbutton member 64 project. The support casing 68 may be fabricated of a relatively rigid non-conductive material or the like. In this regard, each of the pushbutton members 64 includes a flanged portion 70, which in the illustrated embodiment, is arranged integrally extending from opposed lower edge surfaces thereof, these flanged portions being adapted to be received within appropriate receiving channels or slots 72 in the casing 68 to preclude lateral motion while permitting movement normal to the planar surface of the casing 68 upon actuation. More particularly, the flanged portions 70 are appropriately restrained within the slots 72 to prevent lateral movement of the pushbutton members 64, while permitting movement of the pushbutton members from a retracted to an actuating position in response to the application of a mechanical force to the exposed surfaces thereof, similarly to the previous embodiment. Operation of the system illustrated in FIG. 7 is essentially identical to the embodiment illustrated and described in connection with FIGS. 1-4. Accordingly, upon actuation of a selected pushbutton member, the conductive element 22 is similarly caused to execute a snap-action deflection into its over-center position in which it establishes bridging electrical contact between the conductive sheet 18 and an associated conductive pad which is exposed through the aligned apertures in the various layers comprising the keyboard system, in the manner previously explained.

Thus, a unique keyboard system has been described in detail in which a particularly advantageous snap-action bridging electrical contact is provided, as well as the incorporation of such a keyboard system in an electronic calculator.

Various changes and modifications in the above-described invention will be readily apparent to those skilled in the art and any of such changes or modifications are deemed to be within the spirit and scope of the present invention, as set forth in the appended claims.

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