EP0303872A2

EP0303872A2 - Electric switches

Info

Publication number: EP0303872A2
Application number: EP88112316A
Authority: EP
Inventors: Eric Albert Somerfield; Joseph Thomas Morris
Original assignee: Crabtree Electrical Industries Ltd
Current assignee: Crabtree Electrical Industries Ltd
Priority date: 1987-08-19
Filing date: 1988-07-29
Publication date: 1989-02-22
Also published as: GB2209434B; EP0303872A3; GB2209434A; ZA885964B; MY103907A; GB8719610D0

Abstract

An electric switch comprises a housing (6) of plastics material, provided with an open-topped recess (8). Slots (10) extends through side walls (8a, 8b) of the housing and open into the recess (8), within each of which slots a contact (12) is located, so that the two contacts extend generally towards the centre of the recess (8), with a degree of separation. Located in the housing is a bridging device (16), afforded by a single length of wire coiled to form a resilient part (20), in the form of a helical spring, and a bridging part (18) afforded by a diametrically enlarged end section of the spring. The resilient part (20) has a diameter which is less than the separation between the contacts (12), whilst the bridging part (18) has a diameter greater than said separation.

The resilient part (20) urges the bridging part (18) away from the contacts, and into engagement with an actuator afforded by a cover member (22), the cover member being guided by the housing for linear movement between rest and operative positions. By depressions of the cover member (22) the bridging part (18) will be moved against the action of the resilient part (20) into engagement with the contacts (12), to close the circuit in which the contacts are connected.

Description

This invention is concerned with improvements relating to switches.
It is one of the various objects of this invention to provide an electric switch which is simple in its construction and relatively inexpensive to manufacture.
According to this invention there is also provided an electric switch comprising a housing, contacts in the housing which may be connected to form part of an electric circuit, a bridging device comprising a bridging part which is electrically conductive and which is movable (preferably linearly) between a first position in which it is spaced from at least one of the contacts and a second position in which it bridges the contacts to close the circuit, and a reslient part which urges the bridging part to its first position.
Preferably the switch comprises an operating member, preferably affording a cover for the bridging part and the contacts, which is mounted for movement.
Preferably the operating member is mounted on the housing, means being provided to guide the operating member for linear movement between its rest and advanced positions.
Preferably the bridging part is resiliently urged against the operating member by the resilient part, so that movement of the bridging part into its first position causes movement of the operating member into its rest position, and movement of the operating member from its rest position causes movement of the bridging part towards its second position against the action of the resilient part.
The bridging and resilient parts may be separate elements, the bridging part for example being of metal and lying generally in a plane extending parallel to a plane passing through the contacts, and the resilient part being located generally between the contacts and being (e.g.) of elastomeric material and to which the bridging part is secured.
Alternatively the resilient part may be in the form of a compression spring to which the bridging part is secured.
Preferably however the bridging and resilient parts are integral, and are advantageously formed from a single length of wire coiled to provide a helical spring having an diametrically enlarged section at one end, the enlarged section affording the bridging part and the remainder affording the resilient means.
Thus preferably the helical spring engages the underside of an operating member which provides a cover for the bridging part and the contacts, and which is guided for linear movement between rest and advanced positions, depression of the operating member on the side thereof opposite to that engaged by the spring causing the spring to be compressed and the bridging part thereof to be moved into bridging engagement with the contacts.
There will now be given a detailed description, to be read with reference to the accompanying drawings, of a switch which is a preferred embodiment of this invention, having been selected for the purposes of illustrating the invention by way of example.
In the accompanying drawings:

FIGURE 1 is a perspective view of the preferred embodiment;
FIGURE 2 is an exploded perspective view of the preferred embodiment;
FIGURE 3 is a sectional view of the preferred embodiment, taken on the lines III-III of Figure 1, and
FIGURE 4 is a plan view of a bridging device of the preferred embodiment.

The switch which is the preferred embodiment of this invention is specifically a simple press switch, whereby a circuit into which the switch is connected may be momentarily closed by a press button-type movement, and opened by release movement, and is particularly suitable in low current applications.
The switch comprises a housing 6, conveniently of plastics material, provided with a generally rectangular, open-topped recess 8. Slots 10 extend through side walls 8a, 8 b of the housing and open into the recess 8, within each of which slots a contact 12 is located, so that the two contacts extend generally towards the centre of the recess 8, with a degree of separation. One of the contacts 12 is shown in full in dotted lines in Figure 2.
Located in the housing is a bridging device 16, afforded by a single length of wire coiled to form a resilient part 20, in the form of a helical spring, and a bridging part 18 afforded by a diametrically enlarged end section of the spring. The resilient part 20 has a diameter which is less than the separation between the contacts 12, whilst the bridging part 18 has a diameter greater than said separation.
The resilient part rests on a bottom wall 8c of the housing 6, urging the bridging part 18 into engagement with an actuator afforded by a cover member 22, the cover member 22 comprising side arms 24 terminating in flanged portions 26, which are slidable engagable within channels 14 provided in side walls 8a, 8b of the housing 6.
As will be seen from Figure 3, by depression of the cover member 22, the bridging part 18 may be moved against the action of the resilient part 20 towards and into engagement with the contacts 12, to close the circuit in which the contacts are connected, such movements being guided by engagement of the flanged portions 26 within the channels 14. On release of pressure, the cover member 22 moves under the action of the helical spring to its rest position, determined by engagement of the terminal portions 26 with a shoulder defining the termination of the channels 14, with the circuit open.
Preferably the resilient part 20 of the bridging device is in the form of a tapered helical spring, to provide additional stability, whilst the bridging part 18 is afforded by a plurality of generally coplanar turns, to ensure positive engagement with the contacts 12.
If desired to provide for additional stability, the bridging device 16 may be located in engagement with locating formations, such as may be afforded by shallow recesses, in the base wall 9 and the underside of the cover member 22.
The features disclosed in the foregoing description, or the following claims, or the accompanying drawings, expressed in their specific forms or in terms of a means for performing the disclosed function, or a method or process for attaining the disclosed result, or a class or group of substances or compositions, as appropriate, may, separately or in any combination of such features, be utilised for realising the invention in diverse forms thereof.

Claims

1. An electric switch comprising a housing (6), contacts (12) in the housing and which may be connected to form part of an electric circuit, a bridging device (16) comprising a bridging part (18) which is electrically conductive and which is movable between a first position in which it is spaced from at least one of the contacts (12) and a second position in which it bridges the contacts to close the circuit, and a resilient part (20) which urges the bridging part (18) to its first position.

2. An electric switch according to Claim 1 comprising an operating member (22) which is mounted for movement between a rest position and an advanced position.

3. An electric switch according to Claim 2 wherein the operating member affords a cover for the bridging part (18) and for the contacts (12).

4. An electric switch according to one of Claims 2 and 3 wherein the operating member (22) is mounted on the housing (6), means (14, 24, 26) being provided to guide the operating member for linear movement between its rest and advanced positions.

5. An electric switch according to any one of Claims 2, 3 and 4 wherein the bridging part (18) is resiliently urged against the operating member (22) by the resilient part (20), so that movement of the bridging part (18) into its first position causes movement of the operating member (22) into its rest position, movement of the operating member (22) from its rest position causing movement of the bridging part (18) towards its second position against the action of the resilient part (20).

6. An electric switch according to any one of the preceding claims wherein the bridging and resilient parts comprise separate elements, the bridging part (18) being of metal and lying generally in a plane extending parallel to a plane passing through the contacts (12).

7. An electric switch according to any one of the preceding claims wherein the resilient part is located generally between the contacts and is provided by a member to which the bridging part is secured.

8. An electric switch according to any one of the preceding claims wherein the resilient part is in the form of a compression spring, or of a member of elastomeric material.

9. An electric switch according to any one of Claims 1 to 5 wherein the bridging and resilient parts are formed from a single length of wire coiled to provide a helical spring having an diametrically enlarged section (18) at one end, the enlarged section affording the bridging part and the remainder affording the resilient part.

10. An electric switch according to Claim 9 wherein the helical spring engages the underside of an operating member (22) which is guided for linear movement between rest and advanced positions, depression of the operating member against the action of the spring causing the bridging part (18) thereof to be moved into bridging engagement with the contacts (12).