GB2118778A

GB2118778A - Keypad button

Info

Publication number: GB2118778A
Application number: GB08210731A
Authority: GB
Inventors: Peter Bruce Carr
Original assignee: Standard Telephone and Cables PLC
Current assignee: STC PLC
Priority date: 1982-04-13
Filing date: 1982-04-13
Publication date: 1983-11-02
Also published as: NZ203761A; GB2118778B

Abstract

The push-button keypad described in Specification No. 2084801, is modified in that each push button supporting arm has a first portion (14) diverging from the pushbutton (10-11) and a second portion (15) extending parallel to the sides of the frame, and in that each arm, at the point at which it meets the frame has a controlled arcuate thinning to improve its lever action. Each push-button (10-11) has a bleed hole (18) to allow air which might otherwise be trapped under the member to escape, and has one or more stops on its lower surface to limit the downward travel of the pushbutton on depression to prevent damage to the contact dimple. Except for the top row of push-buttons, each of the arms (14-15) straddle a button in the adjacent row. <IMAGE>

Description

SPECIFICATION Keypad button This invention relates to push-button operated electrical switches, and especially but not exclusively to such switches for use in telephone subscriber's instruments. As will be seen later the invention is directed to the switch operating arrangements rather than to the switches as such.

The arrangement described herein is an improvement on the arrangements described in our British Patent Specification No. 2084801 (P.B. Carr 6), in which the switches used are of the so-called dimple pad type. Such a dimple pad is usually a sheet of rubber (or a synthetic rubberlike material) with a dimple for each push-button position. However, a metal dimple pad can also be used. Each such dimple is a dome on the sheet surface which has on its concave surface a region of a conductive material, e.g. metal or a conductive plastics material. Alternatively the whole sheet may be of an electrically conductive plastics material. The dimple pad is located over and electrically insulated from a sheet of an electrically insulating material having electrically conductive regions on it.When a push-button is depressed, its dimple (dome) is collapsed so that its conductive region contacts the conductive region on the lower sheet to complete one or more connections. On release of the push-button it restores to rest assisted by the resilience of the dimple. In the case of a telephone keypad, we use a 4x3 dimple pad, with a corresponding matrix of conductive tracks on the lower sheet.

In the above-mentioned Patent Specification we have described a push-button switch arrangement, which includes a frame-like structure of an electrically insulating material having a cut-out portion within which the actuating member of the push-button is located, said actuating member having an upstanding portion which is depressibie by a user to operate the arrangement, two supporting arms each of which extends from one of a pair of generally parallel sides of the actuating member to the frame-like structure, and contact means located below the actuating member so as to be controllable thereby, in which the two arms extend generally in the same direction but diverging from the actuating member, each said arm being longer than the major dimension of the actuating member, and in which the arms are each integral with the actuating member and the frame-like structure and are resilient, so that resetting of a depressed push-button when the latter is released is aided by the resilience of the arms.

An object of the invention is to provide a pushbutton switch arrangement which is a substantial improvement from the operational viewpoint of that of the above-mentioned Patent Specification.

According to the invention, there is provided a push-button switch arrangement, which includes a frame-like structure of an electrically insulating material having a cut-out portion within which the actuating member of the push-button is located, said actuating member having an upstanding portion which is depressible by a user to operate the arrangement, two supporting arms each of which extends from one of a pair of generally parallel sides of the actuating member to the frame-like structure, and contact means located below the actuating member so as to be controllable thereby, in which the two arms extend generally in the same direction from the actuating member, each said arm being longer than the major dimension of the actuating member, in which each said arm has first and second portions with the first portion diverging from the sides of the actuating member to the second portions which extend substantially parallel to the sides of the frame-like structure, in which the arms are each integral with the actuating member and the frame-like structure and are resilient, and in which each said arm at the point at which it meets a portion of the framelike structure has its thickness reduced in a shallow arcuate manner, so as to enhance the resilience of the arms, the arrangement being such, due to said resilience that resetting of a depressed push-button when the latter is released is aided by the resilience of the arms.

According to the invention there is further provided a push-button switch frame formed by an electrically insulating material which is generally rectangular in shape and has side members and one or more internal members parallel to the side members, a number of pushbutton actuating members each located in a cut out between a side member and a said internal member or between two of said internal members, in which each said actuating member has an upstanding portion which is depressible by a user to operate an associated switch when the frame is in use, in which each said actuating member is coupled to the said frame by two supporting arms each of which extends from one of a pair of generally parallel sides of the actuating member to the frame, in which for each said actuating member its two arms extend generally in the same direction from the actuating member, each said arm being longer than the major dimension of the actuating member, in which each said arm has first and second portions with the first portion diverging from the sides of the actuating member to the second portion which extends substantially parallel to the sides of the frame-like structure, in which for each row of the actuating members except the first, the two arms of an actuating member straddle the actuating member in the adjacent row so as to give a good lever action, in which the arms are each integral with the actuating member and with the frame-like structure and are resilient, and in which each said arm at the point at which it meets a portion of the frame has its thickness reduced in a shallow arcuate manner so as to enhance the arm's resilience, the arrangement being such, due to said resilience, that when the frame is in use the release of a depressed button when the latter is released is aided by the resilience of the arms.

An embodiment of the invention will now be described with reference to the accompanying drawings, in which Fig. 1 is a view from above of the top end portion of a one-piece frame for use in a keypad which uses a number of switches embodying the invention.

Fig. 2 is a cross-section, partly sectioned, along the line lI-Il of Fig. 1, looking in the direction of the arrows.

Fig. 3 is an enlarged underside view of one of the push-buttons with parts of its arms.

Fig. 4 is an enlarged underside view of the region of frame ringed by the dashed circle IV, Fig.

2.

Fig. 5 is a side view of a locating peg, such as on the lower edge (not shown) of the frame.

The novel features of the frame described herein as compared with the frame of the abovementioned Patent Specification are all apparently small, but each of them provides a substantial and extremely valuable improvement in the operating characteristics of the arrangement. The significance of these features will become apparent in the course of the succeeding description.

Fig. 1 shows the uppermost row, and part of the second row, the push-button actuating members for a 4x3 matrix such as used in a telephone subscriber's instrument. The frame is a one piece structure having 12 push-button actuating members, each of which has a generally rectangular portion 10 and an upstanding portion 1 which is rectangular with rounded ends.

When the frame is in use in a telephone set, each of the upstanding portion such as 11 pokes through a similarly-shaped hole in the set's cover.

Each portion such a 11 either has its significance, i.e. its numerical value or other significance printed on it, or carries a cap of a plastics material bearing the appropriate digit.

Each actuating member is in a generally rectangular recess such as 1 3 defined by the frame, and is coupled to that frame by two arms each extending from one side of the actuating member. Each such arm has a divergent portion such as 14 and a portion such as 1 5 which is generally parallel to the side of the frame. As will be seen from the portions of the second row of actuating members, each such member in a row other than the first has its arms straddling an actuating member in the next row. Thus these arms are relatively long, and as can be seen, similarly long arms are used for the actuating member of the uppermost row. By using such relatively long arms we get a long lever effect, which increases the radius of operation. This reduces the angular change of the actuating member and its push-button during travel.

We now refer to Fig. 2, where we see an actuating member 1 0-11 and the part 1 5 of one of its arms. As already mentioned each such arm is integral with the actuating member and with the frame, and at a point near to the frame the arm has its thickness reduced, as indicated at 1 6.

This thinning of the arms gives an improved pivotting action, which reduces the tendency of the arm to go into an arc-shape, and thus reduces the angle through which the button moves.

Each actuating member, as can be best seen from Fig. 3, has on its undersurface four stop pads 17, one at each corner, which together straddle the corresponding dimple when in use so as to limit the travel of the push-button on these pads engage the dimple pad sheet. This prevents a dimple from being crushed when its actuating member is depressed, and enables a reasonable life for the dimple pad to be achieved.

Another important feature of the actuating member is that its flat portion 10 has in it a bleed hole 18. This allows air, which could otherwise be trapped between the actuating member and the dimple pad to escape. Such trapped air can lead to excessive pressures, which would interfere with the correct action of the dimple pad. The underside of the frame has a number of snap-fit lugs such as 20, which fit into holes in the surface below the frame, and which also secure the frame to the lower surface. The accurate location of the frame when thus secured is facilitated by the thickened portion 22, which bears on the lower surface. In addition to these lugs there are studs such as 21, each of which is received in a small hole or recess in that lower surface. At the lowe edge of the frame there are shouldered pegs such as that shown (inverted) in Fig. 5.The end of each such peg rests on the lower surface to define the distance between the frame and the lower surface plus dimple pad. The accurate definition of the spacing thus provided ensures the correct degree of compression of the dimples on the dimple pad. On the upper surface of the frame there are location holes such as 24, Fig. 1, which incorporate crush ribs. These holes co-operate with buttons extending downwards from the underface of a telephone's top case when the frame is in use.

Fig. 4 shows on an enlarged scale the underside of the region of the frame which includes a snap fit lug such as 20.

Thus it will be seen that when a push-button is operated by pressure on the actuating member upstanding portion, that member pivots about the point at which arms are formed integral with the frame. Due to the resilience of the material, aided by the thinning of the arms near to such points, the key depression is smooth and comfortable to the user. This resilience provides some assistance to the resetting action which takes place when the user removes his finger from the depressed button. The resilience of the dimple (not shown) also plays a part in this resetting.

As already mentioned, when the arrangement is used in a telephone keypad, the dimple pad, which has a 4x3 array of dimples is located over and electrically insulated from a lower sheet carrying electrical contacts to be connected when a dimple is "squashed down". This lower sheet may be a printed circuit board with conductive tracks each with contact forming region.

Above the dimple pad there is a one-piece structure formed by a frame as described above with an actuating member per dimple.

Claims

1. A push-button switch arrangement, which includes a frame-like structure of an electrically insulating material having a cutout portion within which the actuating member of the push-button is located, said actuating member having an upstanding portion which is depressible by a user to operate the arrangement, two supporting arms each of which extends from one of a pair of generally parallel sides of the actuating member to the frame-like structure, and contact means located below the actuating member so as to be controllable thereby, in which the two arms extend generally in the same direction from the actuating member, each said arm being longer than the major dimension of the actuating member, in which each said arm has first and second portions with the first portion diverging from the sides of the actuating member to the second portions which extend substantially parallel to the sides of the frame-like structure, in which the arms are each integral with the actuating member and the frame-like structure and are resilient, and in which each said arm at the point at which it meets a portion of the frame-like structure has its thickness reduced in a shallow arcuate manner, so as to enhance the resilience of the arms, the arrangement being such, due to said resilience that resetting of a depressed pushbutton when the latter is released is aided by the resilience of the arms.

2. An arrangement as claimed in claim 1, and in which the actuating member has one or more stops on its lower surface, which stops limit the downward travel of the actuating member when the latter is depressed.

3. A push-button switch matrix which includes an mxn array of switch arrangements each as claimed in claim 1 or 2, the actuating member and the arms of all of the buttons and a single said frame-like structure being formed as a single integral unit.

4. A matrix as claimed in claim 3, and in which the contact means of the switch arrangement are provided by a single layer of insulating material formed with a collapsible dimple per push-button, each said dimple carrying a contact which is brought into engagement with stationary contact means when its button is depressed.

5. A matrix as claimed in claim 4, and in which each said actuating member is generally rectangular in form with its said upstanding portion on one side and a contact-operating portion on the other side.

6. A matrix as claimed in claim 5, and in which each said actuating member has a bleed hole extending between its upper and its lower surfaces, to allow the escape of air which would otherwise be entrapped below that member.

7. A matrix as claimed in claim 4, 5 or 6, and in which for each row of actuating members except the first, the two arms of an actuating member straddle the actuating member in the adjacent row so as to give good lever action.

8. A push-button switch frame formed by an electrically insulating material which is generally rectangular in shape and has side members and one or more internal members parallel to the side members, a number of push-button actuating members each located in a cut out between a side member and a said internal member or between two of said internal members, in which each said actuating member has an upstanding portion which is depressible by a user to operate an associated switch when the frame is in use, in which each said actuating member is coupled to the said frame by two supporting arms each of which extends from one of a pair of generally parallel sides of the actuating member to the frame, in which for each said actuating member its two arms extend generally in the same direction from the actuating member, each said arm being longer than the major dimension of the actuating member in which each said arm has first and second portions with the first portion diverging from the sides of the actuating member to the second portion which extends substantially parallel to the sides of the frame-like structure, in which for each row of the actuating members except the first, the two arms of an actuating member straddle the actuating member in the adjacent row so as to give a good lever action, in which the arms are each integral with the actuating member and with the frame-like structure and are resilient, and in which each said arm at the point at which it meets a portion of the frame has its thickness reduced in a shallow arcuate manner so as to enhance the arm's resilience, the arrangement being such due to said resilience, that when the frame is in use the release of a depressed button when the latter is released is aided by the resilience of the arms.

9. A frame as claimed in claim 8, and in which each said actuating member has a bleed hole so as to release air which could otherwise be trapped on depression of the member when in use.

10. A frame as claimed in claim 8 or 9, and in which each said actuating member has one or more stops on its lower surface, which stops limit the downward travel of the actuating member when the latter is depressed.

11. A push-button switch frame substantially as described with reference to the accompanying drawings.

12. A push-button switch arrangement substantially as described with reference to the accompanying drawings.