GB2372151A - Switch assembly - Google Patents

Abstract

A rotary switch includes a rotatable actuator having a shaft 14 with a profiled section 16 . The switch has a stable moulded inner housing 26 which functions as a detent mechanism. The actuator of the switch has electrical contacts 22 which are recessed. This reduces the amount of moving parts, simplifies assembly and improves switch performance and reliability.

Description

SWITCH ASSEMBLY The present invention relates to a switch assembly for a rotary switch.

Some types of rotary switches generally include a rotatable actuator having a profiled section providing various electrical terminals which co-operate with electrical contacts of the switch to provide the various switching positions. The profiled section can also include switch action cam surfaces for providing the various mechanical switch positions for locating and keeping the actuator in predetermined positions. The electrical and mechanical contacts are biased to the profiled section of the actuator by spring and cam follower assemblies, the springs typically being coil springs.

These known switch assemblies comprise many components, with the result that manufacture and assembly are more costly. Moreover, they can suffer from inaccurate functioning due to wear.

The present invention seeks to provide an improved switch assembly.

According to an aspect of the present invention, there is provided a switch assembly including a housing, a rotatable actuator, at least one electrical contact on the actuator, wherein the or each electrical contact is recessed within the actuator.

Such recessing of the electrical contacts adds to the correct positioning of the actuator as the cam surfaces typically provided on the electrical terminals or to bias the electrical terminals will generally fall into the recesses and require positive force to be moved out.

According to another aspect of the present invention, there is provided a switch assembly including a housing, a rotatable actuator and at least one profiled section rotatable with the actuator, wherein the housing provides a detent mechanism co-operable with the profiled section of the actuator.

The detent mechanism is preferably provided in an inner housing element of the housing. Advantageously, the detent mechanism provides a portion of the housing or housing element which is elastically deformable by the profiled section of the actuator. Thus, no additional components are required to provide controlled positioning of the actuator, in particular no coil springs and separate profile (cam) followers.

In the preferred embodiment, the actuator includes a plurality of electrical contacts co-operable with electrical terminals provided in the housing, the electrical contacts of the actuator being recessed within the actuator.

An embodiment of the present invention is described below, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a plan view in partial cross-section of an embodiment of switch assembly with a cover of the housing thereof removed; Figure 2 is a plan view in partial cross-section of the assembly of Figure 1; Figure 3 is a cross-sectional view of a preferred embodiment of spindle stop feature of the assembly of Figure 1; Figure 4 is a side elevational view of the switch of Figure 1, with cover provided; and Figure 5 is a plan view in partial cross-section of the switch of Figure 1.

Referring to Figures 1 to 5, the embodiment of switch assembly shown includes a housing 10, usually of plastics material, within which a switch actuator 12 is rotatably located.

The actuator 12 is typically a moulded plastics component and includes a shaft 14 which extends out of the housing 10 for attachment to a knob or the like. In an alternative

embodiment, there may be provided a bore instead of a shaft 14, for accommodating a knob which is provided with its own shaft, for example.

The actuator 12 is provided with a profiled portion 16 which is square in plan view. A lower portion 18 of the actuator 12 is substantially circular in plan view and includes a plurality of recesses 20 within which electrical contacts 22 are located. Typically, the electrical contacts 22 are connected together, in practice formed from the same metal part.

The electrical contacts 22 may be offset radially relative to one another to provide different electrical switching times and modes, as is known in the art.

Figures 2 and 3 show a pin 25 which acts as an actuator stop. In practice, the housing 10 includes a shoulder against which the stop 25 abuts to prevent further rotation of the actuator in the same direction. Such a feature is common in most rotary switches so in not shown in detail.

The housing 10 of the switch assembly is substantially square in plan view and includes an inner housing element 24 (shown in Figures 1 and 4) which is substantially square in plan view and is slightly smaller than the inner dimensions of the housing 10 so as to fit therein.

The inner housing element 24 can be thought of as a frame with two resiliently deformable struts 26 extending substantially parallel to one another and between opposing sides of the element 24. The spacing between these struts is about the same as the width of the square profile section 16 of the actuator 12. Functionally, this spacing is less than the diameter of the profile section 16. As the struts 26 are resiliently deformable, the profiled portion 16 and hence the actuator 12 cannot rotate unless the force of rotation imparted to the actuator 12 is sufficient to deform the struts 26.

It will be apparent, particularly with reference to Figure 4, that the lower portion of the actuator 12 which includes the electrical contacts 22 is in effect located and held rotatably in a cavity formed by the housing 10 and element 24.

Figure 4 also shows a cover 28 of the housing 10 which includes a central aperture 30 through which the shaft 14 passes. A plurality of location nuts 32 may be provided for assisting in fitting the switch to electrical equipment.

The electrical terminals for the switch are situated in the base of the housing 10 and ca be seen in particular in Figures 3,4 and 5. Each electrical terminal includes a cam follower 40 located within the housing and a terminal end 42 (see Figure 4) which extends through an appropriate slot in the housing 10 to as to provide the external connections of the switch.

The slots in the housing 10 include fixings 44 which protrude from the base of the housing 10 and which fix one end of their respective terminal 40 such that the cam follower 40 of each terminal can only move by resilient deformation of the terminal. The free end of each cam follower portion 40 is rounded, presenting to the electrical contacts its convex surface.

In Figures 2 and 5 it will be seen that the housing has provision for four electrical terminals 40. In practice only two or three terminals will typically be provided in the switch and their locations within the four positions possible can be selected for the particular application. Of course, some applications may require four electrical terminals.

It will be apparent that in order to rotate the actuator 12, a sufficient rotational force will have to be applied to overcome the return force provided by the struts 26. Moreover, the recessed contacts 22 on the actuator ensure correct contact with the electrical terminals 40 even should the biasing force of the struts 26 diminish, for example due to wear.

Rotation of the actuator 12 will cause different ones of the electrical terminals 40 to be coupled electrically to one another and hence a switching action.

The use of the moulded inner housing as the detent mechanism for the rotary switch significantly reduces complexity of the switch assembly, leading to increased reliability and increased ease of manufacture.

The cam follower portions 40 of the electrical terminals may be held in cantilever form, although could be fixed at both ends to increase rigidity if desired.

In alternative embodiments, there may be any other number of spring elements and their positions relative to one another may be different. For example, there may be provided a single leaf spring element and a plurality of coil springs.

The moulded inner housing may be of a different shape and may be separated into more than one compartment. The base of the moulded inner housing may not have a spherical cavity, it may be of a different shape or alternative the moulded inner housing may not have a base at all.

Of course, the housing could be a frame or any structure which can accommodate the switch mechanisms.

Claims (9)

1. A switch assembly including a housing, a rotatable actuator, at least one electrical contact on the actuator, wherein the or each electrical contact is recessed within the actuator.

2. A switch assembly according to claim 1, wherein the rotatable actuator includes at least one profiled section rotatable with the actuator.

3. A switch assembly according to claim 2, wherein the housing provides a detent mechanism co-operable with the profiled section of the actuator.

4. A switch assembly according to claim 3, wherein the detent mechanism is provided in an inner housing element of the housing.

5. A switch assembly according to claim 3 or 4, wherein the detent mechanism provides a portion of the housing or housing element which is elastically deformable by the profiled section of the actuator.

6. A switch assembly including a housing, a rotatable actuator and at least one profiled section rotatable with the actuator, wherein the housing provides a detent mechanism co-operable with the profiled section of the actuator.

7. A switch assembly according to claim 6, wherein the detent mechanism is provided in an inner housing element of the housing.

8. A switch assembly according to claim 6 or 7, wherein the detent mechanism is in the form of a portion of the housing or housing element which is elastically deformable by the profiled section of the actuator.

9. A switch assembly substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.