GB2266186A

GB2266186A - A keyboard.

Info

Publication number: GB2266186A
Application number: GB9208234A
Authority: GB
Inventors: Hans-Jurgen Schmidt; Theo L Eversloh
Original assignee: Motorola GmbH
Current assignee: Motorola Solutions Germany GmbH
Priority date: 1992-04-14
Filing date: 1992-04-14
Publication date: 1993-10-20
Anticipated expiration: 2012-04-14
Also published as: GB9208234D0; GB2266186B

Abstract

A keyboard (10) comprises a plurality of keys (11), an electrical circuit (15) responsive to operation of the keys (11), a membrane (16) and at least one electrical component (13). The membrane (16) extends across the keyboard (10) and provides a water resistant barrier between the electrical circuit (15) and the keys (11). The electrical component (13) is coupled to the electrical circuit (15) and has portion (17) which passes through the membrane (16) which forms a first water resistant seal (18) about the portion (17) of the component (13). <IMAGE>

Description

A Keyboard.

Background to the Invention.

This invention relates, in general, to keyboards and is particularly, but not exclusively, applicable to keyboards which contain potentiometers or rotary switches and which are sealed in order to prevent moisture and/or dust accumulating therebeneath.

Summarv of the Prior Art.

A keyboard allows a user to either enter information into, or select functions from, equipment. Referring to Fig. 1, and in particular to the elements shown to the left of the line A-A, a typical keyboard is shown comprising a plurality of keys 11, arranged into a keypad 12 . In the case of electrical equipment, such a cellular radio telephone, which is likely to be subjected to a hostile operational environment caused by the presence of dust or moisture, the keyboard is sealed so as to protect any electrical components, such as the conductive element of the key 14 and the PCB 15, contained therebeneath. The keypad 12, as illustrated to the left of the line A-A, is manufactured in an integral form wherein a membrane 16, typically manufactured from an elastomeric material, extends across the area of the keypad 12 and terminates at the line A-A.At present, a potentiometer or rotary switch 13 is provided adjacent to the keypad 12 and extending through a gap in the equipment housing. The gap is sealed by the application of an '0' ring seal or grommet (not shown) secured around the shaft 17 and held within the gap. Unfortunately, the '0' ring seal or grommet may, through use, work loose from the gap and consequentially expose the electrical components beneath to a hostile operational environment. Furthermore, the application of an '0' ring seal or grommet to a gap, typically -2mm in diameter, is an intricate operation.

It can be appreciated that there is a requirement within the art to provide a keyboard which maintains an effective seal against hostile environments whilst offering a simplified method of sealing a potentiometer or rotary switch which is both cheap and effective.

Summarv of the Invention.

This invention addresses at least some of the deficiencies which arise in the prior art described above. In accordance with the present invention there is provided a keyboard comprising a plurality of keys, an electrical circuit responsive to operation of said keys, a membrane and at least one electrical component. The membrane extends across the keyboard and provides a water resistant barrier between the electrical circuit and the keys. The at least one electrical component is coupled to said electrical circuit and has an operating portion which passes through said membrane. The membrane forms a first water resistant seal about said operating portion of the component.

In the preferred embodiment, the membrane is manufactured from an elastomer. Furthermore, the membrane circumscribes the operating portion of the component and produces a water resistant seal thereabout. In a further embodiment, a sleeve extends along a length of the operating portion in a substantially parallel orientation.

and a housing circumscribes said membrane and said operating portion. In yet another embodiment, an angular abutment, coupled to said sleeve and juxtaposed against said housing, forms a second water resistant seal therebetween.

An exemplary embodiment of the invention will now be described with reference to the accompanying drawings.

Brief Descrintion of the Drawings.

Figure 1 is a cross-sectional view of a prior art keyboard incorporating a preferred embodiment of a seal for a potentiometer in accordance with the present invention Detailed Description of the Preferred Embodiment.

With reference to Fig. 1, a preferred embodiment of a seal for a potentiometer or rotary switch 18 is illustrated. A potentiometer or rotary switch 13 is correctly positioned and coupled to a PCB 15.

An elastomeric membrane 16 of a keypad 12 is extended beyond the dimensions of the keypad 12 and around the potentiometer or rotary switch 13. The elastomeric membrane 16 is moulded so as to accommodate the shape and configuration of the potentiometer or rotary switch 13. Furthermore, an opening is provided within the elastomeric membrane 16 so as to allow the shaft 17 of the potentiometer or rotary switch 13 to extend therethrough.

Moreover, the opening has a sleeve 19 which extends substantially perpendicular to the plan of the PCB 15 and which circumscribes the shaft 17 along a proportion of its length; therein forming a moisture-proof and dust-proof seal. The sleeve 19 extends along the shaft 17 for a distance of between lmm and 10mum. An angular abutment 22, circumscribing the opening, is coupled to the sleeve 19 by a diaphragm 23. A rigid housing 20 circumscribes the shaft 17 and the sleeve 19. The angular abutment 22 is juxtaposed to the rigid housing 20 therein forming a second seal about the shaft 17 which prevents water from seeping onto the PCB 15 from around an outer edge of the membrane 16. In the preferred embodiment, the configuration of the abutment 22, diaphragm 23, sleeve 19 and the housing 20 form a well.A knob 21, for potentiometer or rotary switch control, is attached to the shaft 17 in accordance with practices known to one skilled in the art.

It can be appreciated that an invention so designed and described produces the novel advantage of a keyboard which comprises a plurality of keys and potentiometers and/or rotary switches 13 and which has an inexpensive and easily manufactured protective membrane located between its outer surface and electrical components located therebeneath. Furthermore, the preferred embodiment produces the additional benefits of a reduction in the number of separately manufactured parts required for the implementation of a sealed keyboard, a reduction in the intricacy of manufacture and an associated reduction in production costs.

It will of course be understood that the above description has been given by way of example only and that modifications in detail, such as the substitution of the potentiometer and shaft for a light emitting diode (LED), may be made within the scope of the invention.

Claims

Claims.

1. A keyboard (10) comprising: a) a plurality of keys (11); b) an electrical circuit (15) responsive to operation of said keys (11); c) a membrane (16) extending across the keyboard (10) and providing a water resistant barrier between the electrical circuit (15) and the keys (11); and d) at least one electrical component (13), coupled to said electrical circuit (15), having an operating portion (17) which passes through said membrane; the membrane (16) being formed as a first water resistant seal (18) about said operating portion of the component.

2. A keyboard in accordance with claim 1, wherein the membrane (16) is formed into a sleeve (19) which extends along a length of said operating portion (17) in a substantially parallel orientation.

3. A keyboard in accordance with claim 2, wherein the length of said operating portion (17) along which the sleeve (19) extends in a substantially parallel orientation is within the range of lmm and 10mum.

4. A keyboard in accordance with claim 2 or 3, wherein the keyboard further comprises: e) a housing (20) which circumscribes said membrane (16) and said operating portion (17); and the membrane further comprises: e) an angular abutment (22) coupled to said sleeve (19) and juxtaposed against said housing (20), therein forming a second water resistant seal therebetween.

5. A keyboard (10) in accordance with any preceding claim, wherein the electrical component (13) is a potentiometer.

6. A keyboard (10) in accordance with any one of claims 1 to 4, wherein the electrical component (13) is a rotary switch.

7. A keyboard (10) in accordance with any one of claims 1 to 4, wherein the electrical component (13) is a light emitting diode.

8 A keyboard (10) in accordance with any preceding claim, wherein the membrane is manufactured from an elastomer.

9. A keyboard (10) substantially as described herein and with reference to the accompanying drawing.