GB2202991A

GB2202991A - Improved membrane keyboard

Info

Publication number: GB2202991A
Application number: GB08726423A
Authority: GB
Inventors: Jan Waszczuk; Tibor Boskovitz
Original assignee: Amalgamated Wireless Australasia Ltd
Current assignee: Amalgamated Wireless Australasia Ltd
Priority date: 1986-11-17
Filing date: 1987-11-11
Publication date: 1988-10-05
Also published as: CN87107901A; AU8118587A; DE3738817A1; NL8702729A; JPS63141222A; GB8726423D0

Description

1 1 IMPROVED MEMBRANE KEYBOARD C; C, 1) 9 0 0 Z 4 U Z a 01 The invention

relates to membrane pushbuttons and keypads comprising an array of such pushbuttons.

One problem with the use of the membrane keypad is the lack of tactile feedback, so that an operator cannot 5 tell when the button has been actuated.

According to one aspect, the present invention provides a pushbutton including a first contact member comprising a first flexible layer having one or more conductive tracks thereon, a second resilient contact member, a rigid substrate having a depression, the second resilient contact member having a first region projecting a first distance from the wall of the depression and a second region extending from the first region to the base of the depression and a third region which contacts the base of the depression at least on the edge of said third region, the third region containing one or more conductive zones or tracks adapted to co-operate with corresponding conductive track or tracks on the first flexible layer, the first region having a greater stiffness than the second region, whereby when the p:ushbutton is operated the first flexible layer is forced onto the first region which pivots or cantilevers about the wall of the depression and the second and/or third regions are forced into a collapse action by being compressed against the base of'the depression, whereby the conductive zones or tracks on the third region are forced up to contact the corresponding conductive track or tracks on the first flexible layer.

In one embodiment the third region may be cone shaped so that only its rim contacts the base. As an alternative the third region may be flat. In a further embodiment the second region may be tapered towards the middle of the base of the depression.

The depression preferably has a rectangular perimeter but may be circular or may be an open-ended rectangle delineated by a pair of parallel walls. This latter configuration may facilitate leading out conductive tracks from the flexible members.

The electrical contact may be implemented by having a pair of tracks on the upper layer and a bridging contact on the lower layer. The bridging contact may be formed of conductive rubber. An embodiment of invention will now be described, by way of example only, with reference to the accompanying drawings in which: 20 Fig. 1 shows a cross-section of an array of pushbuttons; Fig. 2 shows a partial plan view of the array. In figure 1 there is shown a cross-section through an array comprising several of the buttons embodying the invention. Each button is delineated by an- overlying template 1 of rectangular recesses. Beneath this may be a button designation card 2 on top of the first flexible i - 3 member 3 housing a pair of conductive tracks 4 for each button. Substrate 5 has walls 6 corresponding with the area defined by template 1. Projecting from the top of walls 6 is the first region 8 of second resilient member 7. Region 8 includes a thickened section 9 slightly spaced from wall 6. The thickened section 9 adds a degree of rigidity, and is connected to the wall by a reduced section 10.

The second region 11 is less rigid than the first region 8 and extends to the base of the depression 14. In this embodiment the third region 12 lies flat on the base and carries conductive bridging contact 13.

When the button is depressed the first flexible member 3 is forced down and presses on the edges of first region 8 causing it to bend mainly in its attachment region 10. Thus the second region 11 and third region 12 are pressed against the base and one or both of these collapse to push the conductive zone 13 up to meet the descending member 3 and bridge its conductive tracks 4. Further depression of the button increases contact pressure and may produce a second collapse of the second and/or third regions, emphasizing the tactile feedback reaction of the button.

1 1

Claims

CLAIMS 1. A pushbutton for a keypad including a first contact member

comprising a first flexible layer having one or more conductive tracks thereon, a second resilient contact member, a rigid substrate having a depression, the second resilient contact member having a first region projecting a first distance from the wall of the depression and a second region extending from the first region to the base of the depression and a third region which contacts the base of the depression at least on the edge of said third region, the third region containing one or more conductive zones or tracks adapted to co-operate with corresponding conductive track or tracks on the first flexible layer, the first region having a greater stiffness than the second region, whereby when the pushbutton is operated the first flexible layer is forced onto the first region which pivots or cantilevers about the wall of the depression and the second and/or third regions are forced into a collapse action by being compressed against the base of the depression, whereby the conductive zones or tracks on the third region are forced up to contact the corresponding conductive track or tracks on the first flexible layer.

j 1 1
2. A pushbutton according to claim 1 wherein said third region is cone- shaped so that only its rim contacts said base.
3. A pushbutton according to claim 1 wherein said 5 third region is substantially flat.
4. A pushbutton according to claim 1 wherein said second region is tapered towards the middle of the base of said depression.
5. A pushbutton according to anyone of claims 1 to 4 wherein said depression has a circular or rectangular perimeter.
6. A pushbutton according to anyone of claims 1 to 4 wherein said depression comprises a recess defined by at least two substantially parallel walls.
7. A pushbutton according to claim 1 wherein said first contact member includes a pair of conductive tracks and said second contact member includes a bridging contact adapted to bridge said pair of conductive tracks.
8. A pushbutton according to claim 6 wherein said bridging contact is formed of conductive rubber.
9. A pushbutton substantially as hereinbefore described with reference to the accompanying drawings.

Published 1988 at The Patent Office, State House, 66171 High Holborn, London WC1R 4TP. er copies may be obtained from The Patent Offtoe, Sales Branch, St Mary Cray, Orpington, Kent BR5 3RD. Printed by Multiplex techniques ltd, St Mary Cray, Kent. Con. 1187.