US 3506795 A
Description (OCR text may contain errors)
April 14; 1970 RfFfscHMm-r 3,506,795
\ ELECTRICAL SWITCH DEVICE Filed 001;. 24, 1.96? 2 Sheets-Sheet 1 INVENTOR.
RAYMOND F. SCHMIDT y? WEE-E: \O
o ffllfllif Apr l 1970 R. F. SCHMIDT ELECTRICAL SWITCH DEVICE 2 Sheets-Sheet 2 Filed 001;..24, 1967 FIGJO INVENIOR. RAYMOND F. SCHMIDT BY wwwflww F/Ci.
United States Patent 01 ice Patented Apr. 14, 1970 ABSTRACT OF THE DISCLOSURE An electrical switching assembly for transmitting electrical codes including a printed circuit board with conducting strips, portions of which serve as fixed switch contacts, one manner of accomplishing this is to have the strips include printed circuit contact pads. Keybuttons mounted above the board each have movable spring contacts attached to their bottom end and in various embodiments such spring contacts engage the pads to close or to open the circuit through the conducting strips upon depression of the buttons. At least one of the spring contacts may be used to bias the button to its normal raised position. Various coding arrangements are obtainable by varying either or both of the number and the position of the spring contacts and the coding stations on the printed board. Also, the spring contacts move into engagement with the printed pads in a direction which is non-parallel relative to the board and are shaped to provide a Wiping action against the pads during button operation.
BACKGROUND OF THE INVENTION Field of invention This invention relates generally to keyboard switching apparatus for use in electrical code data transmitting equipment and in related communications systems and more particularly refers to a combination pushbutton and printed circuit board switch arrangement employed in such keyboards.
Description of prior art Conventional keyboards of modular keybutton form or overall single purpose design have various disadvantages. Generally, they are designed so that each mechanical element serves only a single purpose and many are constructed with a number of key-actuated individual modular switches interconnected to provide the appropriate electrical code output. In the latter type of modular switches, to convert a single output system to a multiple output system, additional independent modular switches are often attached to the same keybutton. This approach increases complexity of the mechanical structure of a keyboard assembly and creates undesirable problems such as the keyboard and keybutton sizes, the spacing of the keys, overall Weight of the keyboard, and increased cost. Previously known electrical switchboards, or key switchboards, have been proposed for use in transmission systems wherein by manipulation of selected keybuttons any one of a plurality of high frequencies may be quickly connected to a plurality of output circuits.
Examples of typical prior art switching devices are shown in Patents 3,188,435 and 3,190,975. In Patent No. 3,188,435 a single flexible contact is mounted on a printed circuit board and is moved by an associated separate and independent keybutton, biased upwardly by an associated spring, to make and break contact between conductors on the board. In Patent No. 3,190,975, a plunger carrying a radial group of contact wires is mounted adjacent specially provided contact pins on a printed circuit board. The plunger is urged upwardly from the board by an independent spring. and is actuated by 'a separate keybutton which strikes the plunger to move it downwardly into engagement with the fixed elements.
Devices such as these are not versatile, are limited in their application and, because of the number of independent mechanical elements necessary to accomplish the switching actions, are costly, cumbersome, and subject to operational difficulties and inaccuracies.
SUMMARY OF THE INVENTION A primary object of this invention is to provide a novel electrical switching arrangement which is simple in construction, highly versatile and capable of transmitting a plurality of different combinations of code signals.
Another object is to provide a novel electrical switching device wherein the individual elements perform more than a single function.
A further object is to provide a novel keybutton switching device which is small in size, light in weight, flexible, and readily adaptable to different coding arrangements.
A still further object is to provide a novel keyboard switching device which permits multiple contact arrangements resulting in coding flexibility and versatility.
Still another object resides in the provision of a novel keyboard switching device wherein movable contacts mounted directly on a keybutton are adapted to directly engage portions of printed circuits on a printed circuit board to complete desired code circuits and wherein the contacts provide a spring bias maintaining the keybutton in its normally raised position. In conjunction with this object a further object of providing a plurality of closely juxtapositioned keybuttons, each with different code switching circuitry, is enabled by such keybutton switches.
The invention overcomes the disadvantages of the prior art and accomplishes the above objects by providing an electrical switching device in which a printed circuit board is mounted on a frame, the board having conducting strips which terminate in integral printed circuit pads serving as fixed electrical contacts. A key carrier plate mounted in the frame above the printed board has apertures through which one or more keybuttons are slidingly disposed in a guided alignment relationship with the fixed printed contact pads. Directly attached to the bottom of each keybutton are spring contacts which may engage the printed circuit pads to complete the electrical circuit through the conducting strips and which also function to urge the keybutton to a normal upward position. The spring contact arrangement can be constructed to provide either normally opened or normally closed switching operation, can be single and multi-poled and can be disposed to provide a time sequential operation which enables adaptation to use with strobing pulses or circuits.
The modularity, flexibility, simplicity, and reliability of the invention are accomplished by using each mechanical element for more than a single purpose, i.e., the conducting strips on the printed circuit board also serve as the fixed contacts of the switch; the keybutton, in addition to operating the switch, carries and supports the movable contacts which make and break the electrical circuit; the keyplate functions both to physically position and maintain the keybutton in assembly and to guide and align the keybutton with its attached spring contacts relative to the printed circuit board fixed contacts; and the movable contacts additionally provide the bias force to urge the keybutton to its upward normal position.
BRIEF DESCRIPTION OF THE DRAWINGS FIGURE 1 is a partially broken away perspective view of a keyboard of the invention showing a plurality of switches and associated keybuttons mounted on the keyboard.
FIGURE 2 is a sectional elevational view through line 22 of FIGURE 1;
FIGURE 3 is a sectional view along line 33 of FIG URE 2 illustrating the multiple contact arrangement on a single keybutton;
FIGURE 4 is a plan view of a part of an exemplary printed circuit board and shows the various arrangements of printed pads for the fixed contacts;
FIGURES 5, 6 and 7 are sectional views illustrating in time sequence the contact wiping action which occurs as a keybutton is depressed;
FIGURES 8 and 9 illustrate another embodiment of the invention wherein the keybutton carries two groups of plural contacts, the groups being oppositely affected by the movement of keybutton;
FIGURES l and 11 are sectional views illustrating still another embodiment wherein normally closed contacts are opened upon depression of a keybutton; and
FIGURE 12 is a perspective view of a square cross section button with a modified contact finger plate atfixed to its bottom end.
DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIGURES 1 and 2 of the drawings, the keyboard switching assembly includes a frame 12 having a central recess 14 on the bottom of which rests a printed circuit board 16. The board has conducting strips 18 terminating in integral printed circuit pads 20 made from the same material as the conducting strips and which serve as fixed contacts for the switches. A key plate 22 with a plurality of apertures 24 (nine shown) is mounted within the frame recess 14, is spaced above board 16 by a plurality of spacers 26, and is secured by screws.
Each keybutton 27 projects up through an associated aperture 24 and secured on its lower end is a first stamped metal contact plate 28 with one or more rearwardly disposed spring contact fingers 30 and a second metal plate 29 having a forwardly disposed spring contact finger 31 for engagement with selected fixed contact pads 20 on the printed circuit board 16. The metal to metal engagement of both plates being tightly secured against each other and to the button assure common electrical continuity between all fingers on that button.
Both sets of the fingers 30 and 31 initially extend rearwardly from respective plates 28 and 29 to positions where they are reversely bent upon themselves and terminate in curved contact ends 32. The spring fingers cause the contact ends to perform a wiping action on pads 20 upon depression of the keybutton, as evident from FIG- URES 5, 6 and 7 showing progressive stages of button depression wherein a line 34 through contact end 32 indicates a portion of the finger contact end which initially contacts pad 20 (FIGURE 5). As depression of the button continues, contact end 32 slides in coniunction with a pivotal motion of the contact finger 30 resulting in a combined rocking action on pad 20 in which the marked portion 34 moves through an arcuate path (FIG- URE 6) out of contact with the pad (FIGURE 7). This action during each key operation wipes the pad clean and assures maintaining a good electrical contact through the finger ends and associated pads.
. The described arrangement of the movable contacts 30 and 31 with respect to the printed circuit pads 20 has the advantage that completion of the circuit is accomplished by moving the movable contacts in a direction non-parallel to the printed circuit board pattern, thus pro viding substantially instantaneous closure of the switch and reduces wear on the movable contacts which occurs in prior art printed contact sliding switches due to sliding friction forces.
FIGURES 5, 6 and 7 illustrate an idealistic operation which can be accomplished by the switch construction. As the key is depressed, the contact opening and closing region is in the mid range of travel of the keybutton 27 to provide a range of flexing of the spring finger contacts before and after conductive contact is made. A very narrow hysteresis band between opening and closing contacts results over the wide range of motion. Thus it is virtually impossible to jiggle the switch manually in this region to cause multiple contact jitter.
The button 27 may be guided through its associated button plate aperture 24 by any of several arrangements to insure desired and requisite alignment between contact fingers 30 and 31 and their associated printed circuit pads 20. One arrangement best shown in FIGURE 3 includes a guide pin 36, attached to the bottom of the button and offset from the center axis of the button 27 and slidable through an aligned guide hole 38 through the printed board 16 as well as the frame 12, if necessary. An alternative keybutton guide mechanism illustrated in FIGURE 1 may comprise a pin 42, such as shown attached to the side of the keybutton G and disposed to slide in a slot 44 provided at least partially along the side wall of associated aperture 24. Also, the keybutton 27 and aperture 24 may be made with cross-section shapes other than circular, for example the square cross-section button 28 seen in FIGURE 12, to prevent relative rotation between them and maintain alignment between the movable and fixed contacts without the assistance of additional alignment devices, such as the pins and keyways or pins and holes as have been described.
It is also possible to use several arrangements for returning a keybutton from a depressed position to its normal raised position.
As shown by button H in FIGURE 2, a keybutton may be returned to and retained in its normal elevated position without the use of any separate spring elements by having one or more of the spring contact fingers 30 and 31 set at a different height from the others so that it always remains in contact with its associated pad and urges the button upwardly by its own spring force. This is advantageous and preferred because it eliminates the number of mechanical elements in the system and reduces cost and simplifies the coding operation.
Alternatively, as shown by button B in FIGURE 2, a return Spring 40 encircling guide pin 36 may be provided to urge the button upwardly to its raised position in which either all the contact fingers 30 and 31 are separated from pads 20 or as on button E in FIGURE 2, only certain contact fingers are separated while others remain in contact with the pads. FIGURE 2 also illustrates how the keyboard button height can be varied to provide a slanted aspect or slope to the keyboard.
Versatility in the number of coding operations obtainable with the invention may be accomplished in several ways. As shown in FIGURE 3 a plurality of rows 46, 47, 48 of contact fingers may be provided on a simple standard keybutton. Three rows are illustrated, although more or less are possible. Thus depression of the button with all the fingers positioned for operation makes it possible to transmit three coding signals simultaneously through a standard printed circuit having a standard coding station with three sets of pads. Using the same standard printed circuit, it is possible to transmit less than three signals merely by bending or removing an appropriate finger 30 or 31 so that no contact is made with the associated printed circuit pads.
Another way of gaining coding flexibility is by varying the printed circuit layout to be used with a standard keybutton having three rows of contacts. FIGURE 4 illustrates such a circuit wherein a coding station 50 has independent circuit pads 20a, 20b, 20c, and associated common connection pads 20x, 20y and 202, representing a standard arrangement having three pads to be contacted by the three fingers 30 to transmit three signals. As a variation, coding station 52 includes only the independent circuit end pads 20d and 20e with the center pad omitted, thus the center finger contacts on the associated keybutton have no circuit to complete. Similarly, coding station 54 has omitted one end pad of the three pads, thus eliminating a circuit for one of the keybutton end fingers.
A third method of gaining versatility as to combine the two above, i.e., vary the printed circuit layout while simultaneously adjusting or removing contact fingers to permit or prevent transmission of a coding signal.
The printed circuit board 16 includes a plurality of plug terminal strips 72 which enable circuit connections from the various contact pads to external components. The board may be standardized by having six contact pads at all switch stations (for example 50v in FIGURE 4) and all buttons could have the same number of contact fingers. The code signal could be derived by external circuit connections, only to desired ones of the printed terminal strips 72, e.g., by removing undesired strips 72. More than six contact pads and an equivalent number of button carried contact fingers, e.g., eight can be provided as desired to accommodate a code signal having a greater number of bits.
It is also possible to transmit a plurality of code signals with one or more bits being in a time sequence to enable transmission of a strobe bit or of all bits sequentially. With reference to FIGURE 3, merely by adjusting the movable contacts of the rows 46, 47 and 48 to different heights with respect to pads 20 so. that contact will be made by each of the rows at different times upon downward movement of button 27, sequential making of the various circuits will result.
Another embodiment of the switch is shown in FIG- URES 8 and 9. The printed circuit board 16' has conducting strips 60 with printed circuit pads 62 on its bottom in addition to the top pads 20'. A mounting plate 64 is carried by guide pin 36' and has spring contact fingers 66 which complete circuits through pads 62. As is seen in FIGURE 9, in the normal raised position of keybutton 27', urged by spring 40, the lower fingers 66 are in contact with pads 62. Upon depression of the button (FIGURE8) the fingers 30' contact pads 20 while fingers 66 break contact with pads 62 as a result of the downwardly movement of plate 64. This embodiment greatly multiplies the number of possible coding operations with very little increase in the complexity of the switching device.
FIGURES 10 and 11 show an embodiment where depression of keybutton 27" functions to open the switch rather than close it. The normal raised position of the button is shown in FIGURE 11 with the spring fingers 30" and 31" contacting pads 20" andurging the button upwardly. Upon depression of the button (FIGURE 10), finger 31" engages a fixed abutment such as a knife-edge 70 formed on a rivet head about which the finger'pivots and moves its contact end out of engagement with its associated pad 20" to open the circuit.
FIGURE 12 illustrates a spring finger contact plate 80 secured to the bottom end of button 28. In this modification the single plate carries six contact fingers and the securing means are guide pins 82 which can be molded in or driven into the plastic of button. 28. A flange 84 on each pin serves to clamp the contact plate 80 against the bottom surface of button 28. The plate 80 can be made from Phosphor bronze flat spring contact stock or other suitable conductive material and as shown has six fingers 85, 86, 87, 88, 89, 90. By initially bending and setting certain ones of the fingers different arrangements of code contacts can be realized and desired sequencing of making contact with desired printed circuit contact pads can be accomplished. The illustrated arrangement shows fingers 86, 88 and 90 bent downwardly to initially engage the printed circuit board, and such fingers can provide an initial spring bias force against which the button can be depressed to cause upwardly bent fingers 85, 87 and 89 to engage respective contact pads and make appropriate circuits.
The embodiments of FIGURESS and 9 and FIGURES 10 and 11 may be applied to any of the switching arrangements previously discussed to further increase their flexibility and versatility.
Consider the simplified construction features of: (A) simple keyblock, (B) its associated molded, machined, or punched guide frame, and (C) stamped metal brushes that contact to (D) a circuit board having the dual purpose of providing the interwiring and the mating contact.
The key blocks may be nylon, Teflon, or coated Lucite and move in a chrome guide frame without lubrication, having almost unlimited life at the slow manual speed of operation encountered in such a switch.
The switch construction provided by this invention has ideal bounceless operation which may be used directly into transistor logic circuits without filters or buffers. The wiping action produces clean low resistance contact and very long life.
The invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiments are therefore to be considered in all respects as illustrative and. not restrictive.
What is claimed and desired to be secured by United States Letters Patent is:
1. An electrical switch having a plurality of fixed contacts and a plurality of movable contacts, said movable contacts being in electrical continuity with one another, said fixed contacts representing printed circuit portions, a dielectric member upon which said portions are secured and, with said portions, constituting a printed circuit board; a switch operator; fastening means securing said movable contacts in a predetermined orientation relative to said switch operator; means mounting said board and said operator in adjacent assembly and providnig guided movement of said operator toward and away from said portions so that in one position of said operator, said movable contacts bridge and complete a circuit between at least two of said portions and in another position of said operator said movable contacts break a circuit between said two portions; and spring means in engagement with said board and associated movable contacts biasing said contacts and said operator toward one of said positions.
2. An electrical switch as defined in claim 1, wherein said movable contacts are each an individually projected leaf, are made from spring metal and a plurality of said movable contacts constitute an integral component. I
3. An electrical switch as defined in claim 2 wherein said operator is a push button and said integral component is secured on one end thereof.
4. An electrical switch as defined in claim 3 wherein each of said contacts is a spring leaf with a curved end adapted to engage an associated portion of said printed circuit and each said spring leaf extends laterally of the direction of movement of said push button and towardsaid printed circuit portion.
5. An electrical switch as defined in claim 4 wherein at least one said spring leaf has an angular disposition different from another spring leaf to enable a time sequential engagement of at least two said movable contacts with their associated printed circuit portions.
6. An electrical switch as defined in claim 4 wherein each spring leaf is reversely bent to enable disposition of its contact end substantially in alignment with a projection of the body of said pushbutton in its direction of movement.
7. A switch assembly for use in electrical code data transmitting equipment comprising: a circuit board means having conducting leads terminating in contact pads which serve as fixed switch contacts; at least one keybutton; means mounting said board means and said keybutton in assembly with and shiftably mounted adjacent said board means for movement between two positions toward and away from said board means and said keybutton having movable switch contacts orientated therewith and fastened thereto and disposed so that upon movement of said keybutton from a first to a second position the operative relationship between said movable contacts and said fixed contacts is afiected to change the electrical state of said conducting leads, said movable contacts having effectively pivoted lever arms with curved contact ends, said arms being operative to provide a wiping action by said curved ends against said pads whenever said ends move into and out of contact with said pads.
8. An electrical switching assembly for transmitting electrical codes including: a printed circuit board with conducting strips, portions of which serve as fixed switch contacts; keybuttons mounted above said board, each having movable spring contact means associated with its bottom end, such spring contact means being adapted to engage associated fixed printed contacts to change a circuit through said conducting strips upon depression of the button, at least a portion of said spring contact means biasing said keybutton to a normal position; electrical circuit coding arrangements being enabled by varying combinations of the number, the position of the spring contacts and the conducting strip stations on the printed board, and said spring contacts being constructed and disposed for movement into engagement with the fixed contacts in a direction which is non-parallel relative to the printed circuit board and to provide a wiping action against the fixed contacts during switch operation.
9. A switch assembly for use in electrical data transmitting equipment comprising: printed circuit board means having printed circuit conducting strips, portions of which serve as fixed switch contacts; at least one keybutton; means mounting said board means and said keybutton in assembly with saidkeybutton shiftably mounted adjacent said board means for movement between two positions toward and away from said board means and said keybutton having movable switch contact means associated therewith for movement thereby and disposed so that upon movement of said keybutton from a first to a second position the operative relationship between said movable contact means, and said fixed contacts is affected to change the electrical state of said conducting strips; and spring means engaging said board means and associated with said movable contact means to bias said movable contact means and said button to said first position.
10. The switch assembly of claim 9, wherein guide means cooperate between said movable contact means and said printed circuit board means and orient the movement of said movable contact means and a structurally separate keybutton actuator is provided to move said movable contacts between said two positions.
11. The switch assembly of claim 9, wherein at least a portion of said movable contact means is constructed to function as at least a portion of said spring means.
12. The switch assembly of claim 9, comprising a plurality of movable contact means associated with said keybutton each movable contact means having an elongate shape and as a group cooperating with a plurality of printed circuit portions, the ends of said movable contact means being set at diiferent distances from said keybutton so that upon movement of said keybutton said movable contacts engage said portions at different times to enable a sequential coding operation.
13. The switch assembly of claim 9, wherein at least a portion of said spring means is separate from said movable contact means.
14. The switch assembly of claim 9, wherein said movable contact means has effectively pivoted lever arms with curved contact ends, said lever arms being operative to provide a wiping action by said curved ends against said portions whenever said ends move into and out of contact with said portions.
15. The switch assembly of claim 9, wherein said keybutton is mounted opposite said board means so that movement of said movable contacts is in a direction non-parallel to said printed circuit contact portions during keybutton operation.
16. The switch assembly of claim 9, comprising a plurality of keybuttons each having a plurality of mova-ble contacts, different ones of said keybuttons having different numbers of movable contacts adapted to engage associated said printed circuit portions to enable a permutation switching code condition.
' 17. The switch assembly of claim 9, wherein said printed circuit contact portions are made as enlarged parts of said conducting strips constituting printed circuit pads.
18. The switch assembly of claim 9, wherein said movable contacts are structurally orientated with respect to the associated keybuttons for alignment with said printed circuit contacts, and further comprising: guide means guiding said movement of said keybutton to ensure proper operational alignment of said movable contact means and said fixed contacts.
19. The switch assembly of claim 18, wherein said keybutton is cylindrical, and said guide means includes a guide aperture in said board means and guide pin connected to said keybutton centrally offset from the keybutton cylindrical axis and projecting into said guide aperture in said board means for sliding movement thereing during keybutton operation.
20. The switch assembly of claim 18, wherein said mounting means comprises a carrier plate adjacent said board means slidably supporting said keybutton, andsaid guide means includes a pin laterally extending from said keybutton and a slot in said plate slidably embracing said pin.
21. The switch assembly of claim 18, wherein said mounting means comprises a carrier plate adjacent said board means having at least one aperture within which said keybutton is slidably maintained, said aperture and keybutton being of non-circular cross-section.
22. The switch assembly of claim 19, wherein said printed circuit conducting strips are on one side of said board means, said board means includes additional conducting strips, portions of which serve as fixed switch contacts on the other side thereof, said guide pin extends through said board means, a second set of movable switch contact means is secured on the end of said guide pin in operative association with said portions on said other side so that when said. keybutton is in one of its positions, said second movable contact means and associated printed circuit portions are in engagement and when said keybutton is in one of its positions, said other movable contact means and their associated printed portions are in engagement.
References Cited UNITED STATES PATENTS 3,190,975 6/1965 King 200-1 3,210,484- 10/1965 Dorsey 200-5 3,290,439 12/1966 Willcox et a1.
ROBERT K. SCHAEFER, Primary Examiner J. R. SCOTT, Assistant Examiner US. Cl. X.R. 200-16, 159, 166