GB2208039A

GB2208039A - Manufacture of switch pad arrays

Info

Publication number: GB2208039A
Application number: GB08818618A
Authority: GB
Inventors: James Briggs
Original assignee: HARBORO RUBBER Co Ltd
Current assignee: HARBORO RUBBER Co Ltd
Priority date: 1987-08-15
Filing date: 1988-08-05
Publication date: 1989-02-15
Also published as: GB8818618D0; GB8719369D0

Abstract

A method of producing an array of switch pads, for use in push-button switches for a keyboard, comprises the formation by a moulding technique of a sheet of rubber or flexible synthetic material including a plurality of spaced apart and hollow cup-shaped protuberances 14 of a desired configuration. After moulding, each protuberance 14 is separated from each immediately adjacent one by parting the sheet between the protuberances 14. A panel of plastics or other sheet material 26 is produced having apertures 28 therein in a pattern corresponding to the keyboard in which the switches are intended for use. The separate protuberances 14 are individually inserted in the panel 26, each as a close fit in a respective one of the apertures 28. In the resultant switch pad array the protuberances 14 project at one side of the panel 26 and each of them may have an electrically conductive portion included therewithin. <IMAGE>

Description

Title: Manufacture of contact pad arrays for button switches The invention is concerned with improvements in or relating to the manufacture of contact pad arrays for push-button switches.

In a keyboard for a computer terminal, telephone or other similar equipment, a plurality of push-button switches are arranged in a desired layout. Each switch may comprise a button head or cap which may have an identifying symbol. A contact pad may be provided which comprises a member which may be electrically conductive and is received in a cup-shaped flexible hollow protuberance projecting from a moulded rubber sheet or panel. As the switch is depressed, the cup-shaped protuberance is deflected so that the member moves downwardly into contact with a circuit board or other arrangement such as a membrane system, immediately below the rubber panel. The protuberance is shaped so that there is a snap-action of the walls thereof to force the conductive member into said contact and to return it to its original configuration when the finger pressure is released.

The moulding techniques involved in the production of the rubber panel with an array of protuberances are exacting and expensive. It is an object of the invention to provide a method of manufacture of contact pad arrays which is relatively inexpensive and offers increased efficiency.

The invention therefore provides a method of producing an array of contact pads for use in push-button switches for keyboards comprising the formation by a moulding technique of a sheet of rubber or flexible synthetic material including a plurality of hollow cup-shaped protuberances of a desired configuration, said protuberances being arranged in columns and/or rows each protuberance being at a first distance from adjacent protuberances, separating said protuberance from adjacent ones by parting the rubber material at a region between said protuberances, producing a panel of plastics or other sheet material having apertures therein corresponding to the positions of switches on a push-button switch keyboard and inserting individual separate protuberances in a close fit in said apertures so that each protuberance is arranged at a second distance from adjacent protuberances.

Advantageously, said second distance is sufficient to permit ease of operation by users' fingers, whereas said first distance may be too short to avoid the risk of two switches being operated simultaneously.

The invention further provides a contact pad array produced by the method described above and comprising a panel of plastics or other sheet material having a plurality of apertures from each of which projects an inserted flexible hollow cup-shaped protuberance.

There will now be described with reference to the drawings, examples of a method of manufacturing contact pads by a conventional technique and the method according to the invention. It will be understood that the description of the method according to the invention is given by way of example only and not by way of limitation.

In the drawings: Figure 1 is a fragmentary plan view of a contact pad array made according to the prior art; Figure 2 is a section on line II-II of Figure 1; Figure 3 is a fragmentary plan view of a sheet of components for use in the present invention; Figures 4-7 are top plan, underneath plan, side and sectional views of a separated cup-shaped protuberance of the sheet of Figure 6; and Figure 8 shows an assembled contact pad array.

Figure 1 shows a portion of a rubber sheet 2 having an array of flexible cup-shaped protuberances 4. The position of these protuberances varies according to the keyboard (not shown) for which it is intended. It will be understood that it is therefore necessary to have a different moulding tool made for each keyboard layout. In the present example the protuberances 4 include a portion of flexible electrically conductive material 6 which, when finger pressure is applied to a key cap (not shown), is deflected downwardly, as viewed in Figure 2, against a circuit board 8 to provide contact with circuit portions 10.In other examples, tfle protruberances do not have portions of flexible electrically conducted material 6, these being replaced by a sheet of plastics material lying between the sheet 2 and circuit board 8, the material having electrically conductive portions which are urged against the circuit portions 10 by the protruberances 4 when finger pressure is applied.

There are several disadvantages arising from the above described method of construction. Besides the expense of a different tool for each design of keyboard there are also practical difficulties in moulding the sheet especially where the keyboard is a large one. One difficulty is in controlling the tolerances in the sheet thickness from one region to another of the sheet. Too great a variation in thickness will result in some protuberances having thicker walls than others and giving different tactile response to the keyboard user. Faulty moulding in only one pad protuberance will lead to the whole sheet being rejected.

Moreover, the flexible material used in moulding the sheet is selected for its elasticity, memory retention and durability. Over a large area of the sheet these characteristics remain unused since it is only the walls of the protuberances themselves which are required to be flexible in use.

According to the present invention and as illustrated in Figure 3, a sheet of rubber 12 is moulded within an array of protuberances 14 as before but with the difference that in Figure 3 they are formed in regular columns and rows and are much closer together than in Figure 1. In the present example the distance between centres of adjacent protuberances is 10mm compared with 19mm in Figure 1.

As before, each protuberance 14 comprises a flexible wall 16 and a top portion (as viewed in Figures 6 and 7) from the inner side of which projects a pad of electrically conductive material 20. Again, as described earlier, in some applications the pads of electrically conducted material 20 are omitted, these being replaced in the assembled keyboard by a flexible sheet of plastics material having electrically conductive portions formed thereon,- as is well known in the art.Each protuberance has a peripheral ridge 22, for reasons which will be explained Prior to use, each protuberance is parted from those adjacent thereto by a cutting tool operating along chaindot lines 24 so that each cup-shaped protuberance is provided with a flange formed from a portion of the sheet 12 In the assembly of a desired array, a panel 26 of sheet plastics material, in the present example stiffly flexible in the manner of thin card, is provided with apertures 28 in a pattern crrsnding to the keyboard in which the switches are intended for use These apertures are circular having a diameter equal to that of the protuberance 14 at a level between the ridge 22 and the flange 12.

Thus the separated protuberances 14 are readily inserted into the apertures 28 and are a close enough fit therein, due to the sealing effect of the flange 22, to provide the same dust and moisture harrier as is conventionally provided by a sheet of rubber shown in Figure 1. In this manner, any number of switches may be provided in any desired layout to suit the requirements of the keyboard for which it is required. There is no need for special moulding tools, one tool being able to provide for any layout. All that is needed is a supply of plastics panels 26 having the required layout of apertures.

Moreover the protuberances 14 are of high quality and constant tactile characteristics.

Various modifications may be made within the scope of the invention.

Claims

CLAIMS:

1. A method of producing an array of contact pads for use in push-button switches for a keyboard, comprising the formation by a moulding technique of a sheet of rubber or flexible synthetic material including a plurality of spaced apart and hollow cup-shaped protuberances of a desired configuration, separating each protuberance from each immediately adjacent one thereof by parting the sheet between the protuberances, producing a panel of plastics or other sheet material having apertures therein corresponding to the positions of switches on the push-button switch keyboard and individually inserting separate protuberances each as a close fit in a respective one of said apertures.

2. A method of producing an array of contact pads according to claim 1, wherein said protuberances in the moulded sheet are arranged in columns and/or rows and are separated by parting the sheet linearly between the columns and/or rows.

3. A method of producing an array of contact pads according to claim 1 or claim 2, wherein each of said protuberances is moulded at a first distance from immediately adjacent protuberances and when inserted in the corresponding panel aperture is arranged at a second distance from immediately adjacent protuberances, said second distance being materially greater than said first distance.

4. A method of producing an array of contact pads according to any one of the preceding claims, wherein each protuberance as moulded is of annular shape and the panel apertures are circular and of a corresponding diameter.

5. A method of producing an array of contact pads according to any one of the preceding claims, wherein the moulded sheet is parted so that each protuberance is left with an integral peripheral flange formed of the sheet material moulded in the region between the protuberances and is inserted into the corresponding panel aperture so that the flange locates against one side of the panel.

6. A method of producing an array of contact pads according to claim 5, wherein the protuberances project at the other side of the panel.

7. A method of producing an array of contact pads according to claim 5 or claim 6, wherein each protuberance is moulded with a peripheral ridge and locates in the corresponding panel aperture with the panel closely engaged between the peripheral flange and the peripheral ridge of the protuberance.

8. A contact pad array produced by a method in accordance with any one of the preceding claims and comprising a panel of plastics or other sheet material having a plurality of apertures from each of which projects an inserted flexible hollow cup-shaped protuberance.

9. A contact pad array comprising a panel of plastics or other sheet material having a plurality of apertures, a plurality of hollow cup-shaped protuberances which project at one side of the panel and which are respectively located as a close fit in the panel apertures, each protuberance being a flexible moulding.

10. A contact pad array according to claim 8 or 9 wherein each protruberance has an electrically conductive portion included therewithin.

11. A contact pad array according to claim 8, 9 or 10, wherein each protuberance projects at an upper side of the panel and has a flexible annular side wall which is continuous with a top portion.

12. A contact pad array according to claim 11 when appendant to claim 10 wherein a pad of electrically conductive material secured to the top portion on the inner side thereof provides said included electrically conductive portion.

13. A contact pad array according to any one of claims 8 to 12, wherein each protuberance locates within the corresponding panel aperture with the panel engaged between a peripheral side ridge of the moulded protuberance and an integral end flange thereof.

14. A push-button switch keyboard comprising a contact pad array according to any one of claims 8 to 13.

15. A push-butcon switch keyboard according to claim 14, comprising said contact pad array and a circuit board, the contact pad and the circuit board being juxtaposed in face-to-face relationship and, for each protuberance, the circuit board having circuit portions which on depression of the protuberance are electrically contacted by the electrically conductive portion of the protuberance.

16. A method of producing an array of contact pads, substantially as herein particularly described with reference to Figure 3 to 8 of the accompanying drawings.

17. A contact pad array, or a push-button switch keyboard, constructed and arranged substantially as herein particularly described with reference to Figure 3 to 8 of the accompanying drawings.