GB2168850A

GB2168850A - Key switch

Info

Publication number: GB2168850A
Application number: GB08528434A
Authority: GB
Inventors: Klaus W Quirder; Vitor M Leitao Ribeiro
Original assignee: Schoeller and Co Elektrotecnische Fabrik GmbH and Co
Current assignee: Schoeller and Co Elektrotecnische Fabrik GmbH and Co
Priority date: 1984-12-19
Filing date: 1985-11-19
Publication date: 1986-06-25
Also published as: FI854877A; GB2168850B; IT1186191B; IT8522772A0; GB8528434D0; SE8505989L; DK485985A; SE455355B; SE8505989D0; DE8437099U1; FI854877A0; DK485985D0

Abstract

In a key switch comprising a key foot 3 and a key head 4, a light-emitting diode is disposed in the key foot 3. To simplify assembly without detracting from the visibility of the diode, the key foot 3 comprises a cutout 18, which accommodates a housing 15 of the light-emitting diode. The housing 16 is soldered onto a conductor foil 11, which lies between a support 1 and the key foot 3. A light-conductive element 21 is inserted into an aperture 20 of the key head 4. <IMAGE>

Description

SPECIFICATION Key switch This invention relates to a key switch and concerns a key switch comprising a key foot fixed to a support of a foil switch and a key head, a light-emitting diode being disposed in the key foot and an aperture being provided in the key head above the light-emitting diode.

Such key switches are used, for example, in keyboards having multiple function keys. If the relevant key is actuated, then the light-emitting diode lights up, causing the user to receive an indication of the switched-on function. In known key switches, the diode is mounted in the key foot and must be separately contacted. Such mounting and contacting is complicated, especially if a keyboard comprises a plurality of such key switches.

The visibility of the luminous diode can be improved if it is disposed in the head of the key. This is disadvantageous, however, because then the electrical connection to the diode must be movable.

An object of the present invention is to provide a key switch in which installation of the light-emitting device such as a light-emitting diode is simplified without its visibility being adversely affected.

According to the invention there is provided a key switch in which the key foot possesses a cutout, which accommodates the housing of the light-emitting device or diode, the housing is contacted with a conducting foil which lies between the support and the key foot, and a photoconductor piece is inserted into the aperture.

For installation, it is only necessary for the conducting foil with the contacted light-emitting device or diode in the housing to be placed on the support or foil switch before installation of the key foot. The housing is not fixed to the key foot itself.

The equipping of the conducting foil with lightemitting devices or diodes in housings can be easily arranged for the particular requirements for a greater or lesser number of luminous key switches for a keyboard.

By the use of the photoconductor piece the light at the deep-seated light-emitting diode is conducted to the surface of the key head.

In a preferred embodiment of the invention, the conducting foil possesses, in the region of the foil switch, a cutout. The invention will now be described by way of example with reference to the accompanying drawing in which the Figure shows one embodiment of a key switch according to the invention schematically in section, and to enlarged scale.

On a rigid support 1 of a keyboard, a plurality of key switches 2 are disposed, of which one is shown in the Figure. The key switch 2 possesses a key foot 3 and a key head 4, displaceable relative to it. The key foot 3 is equipped with lugs 5, by which it is secured to the support 1. Beneath the key foot 3 a foil switch 6 is disposed on the support 1. This foil switch comprises, centrally in each key foot 3, a contact bulge 7. A plunger 8 of the key head 4 stands on this contact bulge. When the key head 4 is pressed, an electrically conducting connection is made in the contact bulge 7. Restoring of the position of the key head 4 is effected by the elasticity of the contact bulge 7. To prevent the key head 4 from jumping out of the key foot 3, a stop nose 9 and a stop 10 are provided.

On the foil switch 6, a flexible conducting foil 11 is placed. This foil comprises, in the region of the contact bulge 7, a stamped out aperture 12. On conductor strips 13 and 14 of the conducting foil 11, a housing 15, designed for the SMD technique (surface mounting technique) and comprising terminal surfaces 16 and 17 is soldered. In the housing 15 a light-emitting diode is accommodated, which is connected with the terminal surfaces 16 and 17. The housing 15 possesses, for example, dimensions of approximately 1 mm x 1 mm x 2 mm.

The key foot 3 is provided, in the region of the housing 15, with a cutout 18. The housing 15 is thus situated inside an outer wall 19 of the key foot 3.

Above the housing 15 of the light-emitting diode, an aperture 20 is provided in the key head 4, a photoconductor 21 being inserted into this aperture. Between this photoconductor and the housing 15 there is a distance A, which is slightly larger than the switching travel H of the key head 4.

In assembling the device described, the foil switch 6 is first laid on the support 1. The conductor foil 11 with soldered-on housings 15 is laid on the foil switch. The key feet 3 are then fitted. Finally, the key heads 4 are snapped into the key feet 3 with their photoconductors 21 above the housings 15.

If the key switch 2 is actuated, the relevant function is switched and the light-emitting diode lights up, controlled via an electronic circuit, not show in more detail, until the key switch 2 is again actuated. The photoconductor 21 absorbs the light emitted by the light-emitting diode housed in the housing 15 and conducts it to the surface of the key head 4. The outer wall 19 largely prevents scattered light from emerging laterally alongside the key switch 2, which could constitute a nuisance.

For the photoconductor 21, a plastics material possessing light-orientating properties is suitable.

Internally reflecting small tubes may, however, also be used as photoconductors.

The housing 15 lies protected in the key foot 3. It is therefore almost impossible to damage it by an intervention between two adjacent key switches and it is unlikely to become dirty.

In another embodiment of the foil switch 6, the housing 15 may be soldered directly onto a circuit board containing the conductor paths to be switched. The housing can be arranged to contact the conductor paths by methods other than soldering, for example by gluing or pressing.

1. A key switch having a key foot secured to a

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Key switch This invention relates to a key switch and concerns a key switch comprising a key foot fixed to a support of a foil switch and a key head, a light-emitting diode being disposed in the key foot and an aperture being provided in the key head above the light-emitting diode. Such key switches are used, for example, in keyboards having multiple function keys. If the relevant key is actuated, then the light-emitting diode lights up, causing the user to receive an indication of the switched-on function. In known key switches, the diode is mounted in the key foot and must be separately contacted. Such mounting and contacting is complicated, especially if a keyboard comprises a plurality of such key switches. The visibility of the luminous diode can be improved if it is disposed in the head of the key. This is disadvantageous, however, because then the electrical connection to the diode must be movable. An object of the present invention is to provide a key switch in which installation of the light-emitting device such as a light-emitting diode is simplified without its visibility being adversely affected. According to the invention there is provided a key switch in which the key foot possesses a cutout, which accommodates the housing of the light-emitting device or diode, the housing is contacted with a conducting foil which lies between the support and the key foot, and a photoconductor piece is inserted into the aperture. For installation, it is only necessary for the conducting foil with the contacted light-emitting device or diode in the housing to be placed on the support or foil switch before installation of the key foot. The housing is not fixed to the key foot itself. The equipping of the conducting foil with lightemitting devices or diodes in housings can be easily arranged for the particular requirements for a greater or lesser number of luminous key switches for a keyboard. By the use of the photoconductor piece the light at the deep-seated light-emitting diode is conducted to the surface of the key head. In a preferred embodiment of the invention, the conducting foil possesses, in the region of the foil switch, a cutout. The invention will now be described by way of example with reference to the accompanying drawing in which the Figure shows one embodiment of a key switch according to the invention schematically in section, and to enlarged scale. On a rigid support 1 of a keyboard, a plurality of key switches 2 are disposed, of which one is shown in the Figure. The key switch 2 possesses a key foot 3 and a key head 4, displaceable relative to it. The key foot 3 is equipped with lugs 5, by which it is secured to the support 1. Beneath the key foot 3 a foil switch 6 is disposed on the support 1. This foil switch comprises, centrally in each key foot 3, a contact bulge 7. A plunger 8 of the key head 4 stands on this contact bulge. When the key head 4 is pressed, an electrically conducting connection is made in the contact bulge 7. Restoring of the position of the key head 4 is effected by the elasticity of the contact bulge 7. To prevent the key head 4 from jumping out of the key foot 3, a stop nose 9 and a stop 10 are provided. On the foil switch 6, a flexible conducting foil 11 is placed. This foil comprises, in the region of the contact bulge 7, a stamped out aperture 12. On conductor strips 13 and 14 of the conducting foil 11, a housing 15, designed for the SMD technique (surface mounting technique) and comprising terminal surfaces 16 and 17 is soldered. In the housing 15 a light-emitting diode is accommodated, which is connected with the terminal surfaces 16 and 17. The housing 15 possesses, for example, dimensions of approximately 1 mm x 1 mm x 2 mm. The key foot 3 is provided, in the region of the housing 15, with a cutout 18. The housing 15 is thus situated inside an outer wall 19 of the key foot 3. Above the housing 15 of the light-emitting diode, an aperture 20 is provided in the key head 4, a photoconductor 21 being inserted into this aperture. Between this photoconductor and the housing 15 there is a distance A, which is slightly larger than the switching travel H of the key head 4. In assembling the device described, the foil switch 6 is first laid on the support 1. The conductor foil 11 with soldered-on housings 15 is laid on the foil switch. The key feet 3 are then fitted. Finally, the key heads 4 are snapped into the key feet 3 with their photoconductors 21 above the housings 15. If the key switch 2 is actuated, the relevant function is switched and the light-emitting diode lights up, controlled via an electronic circuit, not show in more detail, until the key switch 2 is again actuated. The photoconductor 21 absorbs the light emitted by the light-emitting diode housed in the housing 15 and conducts it to the surface of the key head 4. The outer wall 19 largely prevents scattered light from emerging laterally alongside the key switch 2, which could constitute a nuisance. For the photoconductor 21, a plastics material possessing light-orientating properties is suitable. Internally reflecting small tubes may, however, also be used as photoconductors. The housing 15 lies protected in the key foot 3. It is therefore almost impossible to damage it by an intervention between two adjacent key switches and it is unlikely to become dirty. In another embodiment of the foil switch 6, the housing 15 may be soldered directly onto a circuit board containing the conductor paths to be switched. The housing can be arranged to contact the conductor paths by methods other than soldering, for example by gluing or pressing. CLAIMS

1. A key switch having a key foot secured to a support for a foil switch and a key head, a light emitting device such as a light-emitting diode disposed in the key foot and an aperture provided in the key head above the light-emitting device, the key foot comprising a cutout which accommodates a housing for the light-emitting device, the housing being connected with a conductor foil which lies between the support and the key foot, and a photoconductor in the aperture.

2. A key switch according to claim 1, in which the conductor foil lies between the foil switch and the key foot.

3. A key switch according to claim 1 or 2, in which the conductor foil is provided with an aper ture in the region of the foil switch.

4. A key switch according to any one of the preceding claims, in which the housings of the light-emitting devices of a keyboard are soldered on the conductor foil.

5. A key switch according to any one of the preceding claims, in which the housing is of rectangular form and comprises terminal surfaces.

6. A key switch according to any one of the preceding claims, in which the key foot shields the housing from the environment.

7. A key switch according to any one of the preceding claims, in which the distance (A) between the photoconductor and the housing is slightly larger than the travel (H) of the key head.

8. A key switch substantially as hereinbefore described with reference to and as illustrated in the accompanying drawing.