Keyboard Pushbutton Switch

Abstract

A desktop keyboard for data encoders, calculators and the like comprises an electrically insulative board having a plurality of contact members and mounting clusters of key switches to provide electrical engagement between pairs of contact members. An electrically conductive bridge member is captured within a key switch housing and slides and pivots in continuous engagement with one contact member of a pair and moves into and out of engagement with the second contact member of a pair upon predetermined movement of the respective key. A single spring member provides both pretravel and overtravel of each key as well as providing the contact force. A plurality of multiposition point switches are also mounted on the board and comprise a contact element slidably movable to any one of a plurality of contact members to provide a selected mode of operation.

Description

This application contains subject matter similar to that disclosed and claimed in coassigned, copending application Ser. No. 376,654 entitled "Key Switch Apparatus" filed July 5, 1973 and coassigned, copending application Ser. No. 376,638 entitled "Key Switch Apparatus" filed July 5, 1973.

This invention relates to keyboards and more particularly to keyboard switches especially useful for desktop apparatus.

It has been a practice for many years wherever keyboard switches are employed in desktop type apparatus, that is where miniaturization of the switches is not required as in hand held calculators and the like, to provide keys similar to typewriter keys which have significant travel during actuation of the switch and even overtravel after actuation. By depression of a key through most of its stroke, actuation is thus assured. This feature has long since become a required characteristic of such keyboards since operators have become accustomed to it. Such apparatus includes data entry devices, calculators and the like.

It is an object of this invention to provide keyboard apparatus particularly useful with desktop type apparatus in which the keys have substantial travel or stroke. Another object is the provision of such apparatus which is extremely long-lived since it will be subjected to many thousands of cycles. Yet another object is the provision of keyboard switches which are reliable yet relatively inexpensive to produce and are conducive to mass manufacturing techniques; that is the labor content in manufacturing be kept to a minimum. Yet another object is the provision of keyboard apparatus in which contact bounce is minimal.

Still further objects and advantages of the invention will be apparent from the following detailed description and claims and from the accompanying drawings illustrative of the invention wherein:

FIG. 1 is a perspective view of a keyboard device including a plurality of key switch clusters and a plurality of multiposition point switches which are mounted on a printed circuit board;

FIG. 2 is a cross sectional view taken on lines 2--2 of FIG. 1 showing a key switch in its normally open or contacts disengaged position;

FIG. 3 is a cross sectional view similar to FIG. 2 but showing the key switch in its closed or contacts engaged position;

FIG. 4 is a perspective view of a movable bridge member used in the key switches of FIGS. 1-3;

FIG. 5 is a cross section taken through a portion of the printed circuit board showing a contact member;

FIG. 6 is a cross sectional plan view taken on lines 6--6 of FIG. 1 through multiposition point switch 6; and

FIG. 7 is a perspective view of the contact arrangement of the multiposition switch of FIG. 6.

In the detailed description, corresponding reference characters indicate corresponding elements throughout the several views of the drawings.

Briefly, in accordance with the invention an electrically insulative board has a printed circuit disposed on one surface and a plurality of staple like U-shaped members inserted through apertures from the opposed surface with the free ends of the staple legs terminating in electrical contact with selected portions of the printed circuit. A plurality of key clusters are disposed on the printed circuit board each comprising a plurality of key switches, each switch adapted upon depression to electrically engage a pair of staples. Each key switch comprises an elongated keybody mounted for sliding movement in a guideway of a housing toward and away from stationary contacts or staples mounted on the circuit board. An electrically conductive bridge member is captured in the housing and is biased toward bridging electrical engagement between the pair of staples by a coil spring extending from the keybody to the bridge member. The bridge member is provided with a leg having a distal end disposed within an opening formed by a U-shaped portion extending from the keybody. In the preferred embodiment the key switch is normally open since the spring biases the keybody upwardly lifting the distal end of the bridge member and the bridge member out of engagement with one of the staples of the pair, the bridge member sliding slightly and pivoting on the second staple of the pair. Depression of the switch allows the leg to move down and the bridge member into engagement with the one staple of the pair.

FIG. 1 shows a Keyboard 1 particularly useful in desktop calculator models. As seen in the Figure there are a plurality of key clusters 2-5 and a plurality of multiposition point switches 6-8 all of which are mounted on a circuit board 16. Although any conventional circuit board including two sided boards may be employed it is preferred to use a board having desired circuitry printed on one side, the bottom side as viewed in FIG. 1, with the required contacts in the form of staple like members disposed on the opposite side of the board with the legs of the staples extending through apertures in the board and terminating in electrical connection with selected portions of the printed circuitry. It will be realized of course that various other contact members could be employed.

The several key clusters are identical in construction, the only difference being the number of keys and the size of the particular buttons in each cluster. Thus a detailed discussion of one switch will suffice for the others. Key cluster 3 comprises a housing 14 of a conventional electrically insulative material such as polycarbonate mounted on board 16 in any convenient manner as by use of conventional screw fasteners (not shown). A plurality of key units 12 are formed in housing 14, each unit having a guideway 26 shown in FIGS. 2 and 3. For each key unit 12 a pair of U-shaped electrically conductive contact members in the form of staples 18, 20 are received in apertures provided in electrically insulative board 16 extending from a first surface 22 to a second opposed surface 24. An elongated keybody 28, also of electrically insulative material is slidingly received in guideway 26 and is adapted for movement toward and away from staples 18, 20. Keybody 28 is formed with an axially extending slot 30 in communication with a spring receiving bore 32 at the force transmitting end 34 of keybody 28.

An electrically conductive movable bridge member 36, a relatively stiff, inflexible member is disposed in a switch chamber 56 within key unit 14. As best seen in FIG. 4, member 36 has two contact sections 38 and 40 with a leg 42 extending from contact section 40 and terminating at a first distal end 44. A second leg 46 extends from contact section 38 and has a second distal end 48. Intermediate contact sections 38 and 40 is an upwardly bent portion 50.

Movable bridge member 36 is disposed in a switch chamber with contact section 38 in engagement with bight 52 of staple 20. A helical coil spring member 58 is also disposed in switch chamber 56 and extends from a spring seat 60 formed by the intersection of slot 30 and bore 32 in keybody 28 to the movable bridge member 36 with the second leg 46 and upwardly bent portion 50 extending into the space defined by spring 58 forming a seat for the spring.

Leg 46 cooperates with portion 50 to maintain spring 58 in the desired location. Distal end 48 of leg 46 is provided with a hook portion to facilitate assembly of the device. That is, spring 58 can be placed on movable contact member 36 with distal end 48 hooked over the top of the spring maintaining the spring slightly compressed and holding it in position so that it can be easily handled. Once mounted in the switch distal end 48 is no longer functional since seat 60 of keybody 28 further compresses spring 58 and maintains it away from end 48.

Keybody 28 is formed with a laterally projecting U-shaped portion 62 formed by legs 64 (only one being shown) integrally attached to keybody 28 and joined by a bight portion 66. A beveled surface 68 is formed in bight portion 66 which is adapted to engage distal end 44 of leg 42 of movable contact member 36 which is trained through the opening in U-shaped portion 62.

As seen in FIG. 2 in which the switch is at the at rest contacts disengaged position, spring 58 reacts against bight 52 and the wall of housing 14 through the extreme end portion 70 of contact section 38 and biases keybody 28 upwardly with bight portion 66 camming leg 42 upwardly lifting contact section 40 out of engagement with bight 54 of staple 18. As the keybody 28 is depressed by a force transmitted through the force transmitting end 72 of the keybody the cam 66 is moved downwardly allowing leg 42 and contact section 40 to move downwardly until contact section 40 comes into engagement with bight 54 of staple 18. Use of the single spring 58 as shown provides both pretravel and overtravel of the keybody. It will also be noted that all of the spring force is directly utilized as contact force.

In an exemplary switch made in accordance with the invention the keybody has approximately 0.150 inches overall travel. Contact engagement occurs after approximately 0.075 inches followed by 0.075 inches overtravel with surface 66 moving away from distal end 44 and spring 58 being further compressed. While bridge member 36 is pivoting on bight portion 52 of staple 20 there is a slight contact wiping occurring at that section since end 70 forces bridge member 36 to slide slightly to the left as seen in FIGS. 2 and 3, upon contact engagement. However, once contact section 40 comes into engagement with bight 54 there is no further sliding movement and hence no electrical noise after contact engagement.

Multiposition point switches, 6, 7 and 8 shown in FIG. 1 are of identical structure and hence only one will be discussed in detail. In FIG. 6 multiposition point switch 6 is illustrated. The switch is shown having six positions, however the particular number of positions is a matter of choice. Housing 80 mounts a slide member 82 thereon and is formed with opposed lips 84 to confine slide 82 to linear sliding movement (right and left as seen in FIG. 6). Integrally formed with slide member 82 is a knob 86 extending from a raised platform 88 on which a series of serrations 90 is preferably provided to facilitate handling. A series of detents 92 are formed in the bottom surface of slide 82 each being adapted to receive therein a spherical member 94 received in bore 96 formed in housing 80 and biased toward the slide member by a coil spring 98 disposed in bore 96 intermediate member 94 and a bottom wall of the bore forming a spring seat 100.

Grooves 102, 104 are formed on opposite sides of housing 80 on the end of the housing received on printed circuit board 16 and receive therein respective opposite L-shaped tab ends 106, 108 of an electrically conductive retainer plate 110. A bore 112 is formed in slide member 82 and lockingly receives the shank 114 of leg 116 depending from slide member 82. Leg 116 extends through a longitudinally extending slot 118 formed in plate 110 and is received in a slot 120 of a resilient electrically conductive member 122. Resilient member 122 is generally wave shaped having an undulated convex and concave top and bottom surface. A row of contact members such as staples 126 between outer contact members such as staples 128 and 130 are disposed beneath retainer plate 110 and are arranged so that their bight portions are generally parallel to one another. The legs of staple 126 extend through apertures in board 16 in the same manner as shown in FIG. 5 with at least one leg of staples 126 in electrical connection with a selected portion of the printed circuit. The outer staples 128 and 130 of the row are electrically connected to ends 106, 108 respectively of the retainer plate, however only staple 128 is in electrical connection with the printed circuit. Thus a circuit path can be traced from the printed circuit through staple 128, plate 110, spring contact member 122 to one of staples 126 depending on the position of slide member 82. The indents 92 are so located relative to the position of staples 126 that when spherical member 94 is received in any one of detents 92 spring contact 122 is biased into electrical contact with one of staples 126.

Housing 82 may be mounted on board 16 in any convenient manner such as by use of screws 132. A duplicate set of detents 134, extend from the center of slide 82 to the right as seen in FIG. 6 so that spherical member 94 and spring 98 can be located either as shown or in bore 136 if so desired.

The design of the keyboard described above is particularly suitable for mass manufacturing techniques. The printed circuit is plated on a surface thereof, the electrical contacts in the form of staples are inserted through apertures provided in the board, the connections are soldered by flow soldering and then the entire board is scrubbed clean with appropriate detergents. The board acts as a support for the several key clusters and multiposition switches which are locked into place, as mentioned supra, as by use of screw fasteners. No jumpers or other connectors are required so that hand work on the keyboard is kept to an absolute minimum. Once the keyboard is assembled with its switches thereon it is placed in a receiving bezel of a desk top calculator and the circuit board is electrically connected to the other component parts of the apparatus such as for instance, a read only memory (ROM), program counter (PC), instruction register (IR), control decoders and other desired components.

Although the invention has been described with respect to specific preferred embodiments thereof, many variations and modifications will immediately become apparent to those skilled in the art. It is therefore the intention that the appended claims be interpreted as broadly as possible in view of the prior art to include all such variations and modifications.

Claims

I claim:

1. A keyboard switch comprising:

an electrically insulative base having opposed first and second surfaces, and having a plurality of apertures extending from the first to the second surfaces;

a pair of electrically conductive U-shaped members, each member having two legs joined by a bight portion, each of the legs received in a respective aperture in the base with the bight portion disposed on the first surface;

a keybody having a force receiving end and a force transmitting end;

a housing disposed over the pair of U-shaped members, the housing having guide means aligned with the U-shaped members, the keybody received in the guide means and movable toward and away from the U-shaped members;

means normally biasing the keybody away from the U-shaped member;

a movable electrically conductive bridge member in continuous pivotal contact with the bight portion of one U-shaped member and pivotably movable into and out of engagement with the bight portion of the other U-shaped member; and

means operatively connecting the keybody and the conductive bridge member so that the bridge member moves into engagement with the bight portion of the other U-shaped member when the keybody moves toward the U-shaped member and moves out of engagement with the bight portion of the other U-shaped member when the keybody moves away from the U-shaped member.

2. A keyboard switch according to claim 1 in which the conductive bridge member has a first free distal end, the keybody has a portion extending laterally therefrom, the keybody portion formed with a surface adapted to contact the distal end of the conductive bridge member to force the conductive bridge member out of engagement with the bight portion of the other U-shaped member when the keybody is moved away from the U-shaped members.

3. A keyboard switch according to claim 2 in which the conductive member has an upwardly extending intermediate portion and the means biasing the keybody includes a helical spring which extends from the keybody to the conductive bridge member with the intermediate portion extending into the space defined by the spring.

4. A keyboard switch according to claim 2 in which the portion of the keybody extending laterally therefrom is generally U-shaped having two legs integral with the keybody and a bight portion forming the surface adapted to contact the first distal end of the conductive bridge member, an opening being defined between the U-shaped portion and the remainder of the keybody, the first distal end received in the opening and disposed in engagement with the bight surface.

5. A keyboard switch according to claim 4 in which the bight surface of the keybody is beveled.

6. A keybody switch comprising:

an electrically insulative base;

a pair of spaced stationary electrical contact members supported on the base;

a keybody having a force receiving end and a force transmitting end;

a housing disposed over the pair of contact members, the housing having guide means aligned with the contact members, the keybody received in the guide means and movable therein toward and away from the contact members;

means normally biasing the keybody away from the contact members;

a movable relatively stiff inflexible electrically conductive bridge member in continuous pivotal contact with one stationary contact member of the pair and pivotably movable into and out of engagement with the other stationary contact member of the pair; and

means operatively connecting the keybody and the conductive bridge member so that the bridge member moves into engagement with the other contact member when the keybody moves toward the contact members and moves out of engagement with the other contact member when the keybody moves away from the contact members.

7. A keyboard switch according to claim 6 in which the movable conductive bridge member has a first free distal end, the keybody has a portion extending laterally therefrom, the keybody portion is formed with a surface adapted to contact the distal end of the movable conductive bridge member to force the movable conductive bridge member out of engagement with the other stationary contact member of the pair when the keybody is moved away from the stationary contact members.

8. A keyboard switch according to claim 7 in which the movable conductive bridge member has an upwardly extending intermediate portion and the means biasing the keybody includes a helical spring hich extends from the keybody to the movable conductive bridge member with the intermediate portion extending into the space defined by the spring.

9. A keyboard switch according to claim 7 in which the portion of the keybody extending laterally therefrom is generally U-shaped having two legs integral with the keybody and a bight portion forming the surface adapted to contact the first distal end of the movable conductive bridge member, and opening being defined between the U-shaped portion and the remainder of the keybody, the first distal end received in the opening and disposed in engagement with the bight surface.

10. A keyboard switch according to claim 9 in which the bight surface of the keybody is beveled.