GB2336722A

GB2336722A - Rotary switch assembly

Info

Publication number: GB2336722A
Application number: GB9821992A
Authority: GB
Inventors: John Harris
Original assignee: Arcolectric Switches PLC
Current assignee: Arcolectric Switches PLC
Priority date: 1998-04-20
Filing date: 1998-10-08
Publication date: 1999-10-27
Anticipated expiration: 2018-10-08
Also published as: GB9821992D0; GB2336722B; GB9808313D0

Abstract

A rotary switch assembly comprises a rotatable actuator 12 which has at least one profile section 16, 18 rotatable with the actuator and at least one leaf spring 40 cooperable with the profiled section 16, 18. The leaf spring 40 may include a portion 48 in the shape of a cam follower which follows a mechanical cam surface of the profiled section 18 for providing the mechanical action of the actuator 12. Furthermore, a second spring element 46 may bias a electrical contact 24 onto the other cam surface 16 for opening and closing of the contact 28. Such a leaf spring 40 reduces the number of components required and simplifies assembly.

Description

2336722 SWITCH ASSEMBL The present invention relates to a switch assembly

for a rotary switch and to a guiding spring therefor.

Rotary switches generally include a rotatable actuator having a profiled section providing various electrical cam surfaces which cooperate with electrical contacts of the switch to set the switch into its various operating positions. The profiled section can also include switch action cam surfaces for providing the various mechanical switch positions for keeping the actuator in a predetermined position. 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.

The present invention seeks to provide an improved rotary switch assembly.

According to an aspect of the present invention, there is provided a rotary switch assembly including a housing, a rotatable switch actuator, at least one profiled section rotatable with the switch actuator and at least one leaf spring cooperable with the profiled section.

The use of at least one leaf spring significantly reduces complexity of the switch assembly, leading to increased reliability and increased ease of manufacture.

Preferably, the leaf spring includes at least one portion in the shape of a cam follower. Thus, no further components may be necessary.

2 The leaf spring may be held in cantilever form, although in the preferred embodiment is held at both ends.

The spring may include a plurality of leaf spring elements for providing different biasing actions. For example, the spring may include a first spring element operable to follow a mechanical cam surface of the profiled section for providing the mechanical action of the actuator and a second spring element operable to bias an electrical contact onto an electrical cam surface of the profiled section.

In the preferred embodiment, the spring includes a pair of electrical spring elements cooperable with respective ones of a pair of electrical contacts. The electrical spring elements are advantageously provided on opposing sides of the mechanical spring section.

In another embodiment, there may be provided one or more coil springs cooperable with one or more profiled sections.

The various spring sections may be of different resilience, depending upon the particular application. Different resiliences can be provided by the sections being of different dimensions, such as different widths or different thickness (such as with a milled strip). It is also envisaged that different materials may be used.

3 According to another aspect of the present invention, there is provided a spring for a rotary switch including at least one spring element having a profile which provides a cam follower.

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 front elevational view in partial cross-section 10 of an embodiment of switch assembly; Figure 2 is a plan view in partial cross-section of the assembly of figure 1; Figure 3 is a perspective view of a preferred embodiment of spring of the assembly of Figure 1; Figure 4 is a front elevational view of the spring of Figure 3; Figure 5 is a side elevational view of the spring of Figure 3; Figures 6a and 6b are, respectively, side elevational and plan views of another embodiment of spring; and Figure 7 is an exploded view in perspective of another embodiment of spring assembly including the spring of Figures 6a and 6b.

Referring to Figures 1 to 5, the embodiment of switch assembly 30 shown includes a housing 10, usually of plastics material, 4 within which a switch actuator 12 is rotatably located. The actuator 12 is accessible from outside the housing 10 so it can be operated, typically by having an actuator shaft (not shown) extending beyond the housing 10 or a bore (not shown) for receiving a shaft from a driving component.

The actuator 12 includes in this embodiment a profiled section 14 providing both electrical and mechanical cam profiles. The electrical cam profile 16 includes first and second cam surfaces which provide electrical on/off functions, described more fully below. The mechanical cam profile 18 of the profiled section provides mechanical cam surfaces for setting the actuator into one of a plurality of positions.

In this example, the profiled section 14 includes two electrical cam profiles 16, located on the opposite sides of the mechanical cam profile 18. The electrical cam profiles 16 may be offset relative to one another to provide different electrical switching times and modes, as is known in the art.

The switch shown in the drawings includes electrical terminals 20,22 at both ends of the switch. For this purpose, the switch is provided with two sets of electrical contacts 24. Each electrical contact 24 includes a hinged end 26 which is pivotable on hinged terminal 20 and a contact end 28 movable onto and away from end terminal 22.

At an intermediate position along each electrical contact 24, the contact is profiled to give a cam follower section 30 for following the electrical cam profile 16 of the profiled section 14 of the actuator 12 and by thus doing to move the contact end 28 onto or away from the end terminal 22.

Biasing of the electrical contacts 24 onto the electrical cam profiles 16 is provided by means of spring 40. This spring 40 also provides a cam follower cooperable with the mechanical cam profile 18, as described below.

Referring to Figures 3 to 5, the spring 40 includes a substantially flat base 42 which in this example is provided with a plurality of cut-out sections for fixing purposes. In some applications, it is envisaged that the base may be substantially rectangular.

Extending from the base 42 are three spring elements 44,46, which in this example are formed by cutting and bending a sheet of material to form the base and spring elements.

The two spring elements 46 are located on opposing sides of and are shorter than spring element 44. These elements 46 abut the electrical contacts 24 to bias the contacts 24 onto the electrical cam profiles 16 of the switch actuator 12.

Central spring element 44 extends higher than spring elements 46 when viewed in side elevational view and includes a humped section which provides a cam follower portion 48. This design results from the relative dimensions and positions of the cam profiles 16,18 of this particular example of switch.

1 6 The free end 50 of the central spring element 44 is generally straight.

Figures 3 to 5 show the spring elements 46 as being wider than the central spring element 48, which would make them stiffer. The relative stiffnesses of the three spring elements depends upon the particular switch configuration and it is envisaged, for example, that in some applications it would be advantageous for the central element 44 to be stiffer than the two side elements 46. Similarly, the differences in spring stiffnesses can be achieved by different thicknesses, which can readily be provided, for example, by a milled strip or the like. Alternatively, different materials could be used for the different spring elements.

Referring again to Figures 1 and 2, there are provided in this example two identical springs 40, each at a respective side of the switch. The base 42 of each spring 40 is fixed to the housing 10 by suitable fixings (not shown). The side spring elements 46 abut respective electrical contacts 24 adjacent their hinged ends 26.

The cam follower 48 of the central spring element 44 engages the mechanical cam profile 18. In order to provide relatively strong mechanical stop positions of the actuator 12, the free end 50 of the central spring 44 is preferably held in a fixed position relative to the housing 10. This will considerably increase the stiffness of the central spring element 44, which is considered an advantage in this particular application.

7 operation of the switch will be apparent as a result of the above description so will not be set out in detail. It will also be apparent that the design of the spring elements is such that they can operate independently of one another.

Another embodiment of spring 401 is shown in Figures 6a and 6b. This embodiment includes two side spring elements 461 equivalent to the spring elements 46 of the embodiment of Figures 3 to 5 but no central spring element equivalent to the element 44 of that embodiment.

Referring to Figure 7, the spring 40' fits within a switch housing 101 in an analogous fashion to the spring of the firstdescribed embodiment, with the two side spring elements similarly engaging cam profiles 16 of an actuator (not shown in Figure 7).

A coil spring 52 is located between the two side spring elements 461 and couples to a plunger or cam follower 54, of conventional form. The plunger 54 engages and moves with the mechanical cam profile 18, in similar fashion to the spring element 44 of the spring 40 of Figures 3 to 5.

Although the embodiment of Figures 6 and 7 uses one coil spring, it still benefits from a reduced number of components and simplification of assembly compared to prior art assemblies.

These examples of spring element can also provide for more jO reliable operation.

8 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.

9

Claims

1. A rotary switch assembly including a housing, a rotatable switch actuator, at least one profiled section rotatable with the switch actuator and at least one leaf spring cooperable with the profiled section.

2. An assembly according to claim 1, wherein the leaf spring includes at least one portion in the shape of a cam follower.

3. An assembly according to claim 1 or 2, wherein the leaf spring is held in cantilever form.

4. An assembly according to claim 1 or 2, wherein the leaf 15 spring is held at both ends.

5. An assembly according to any preceding claim, wherein the spring includes a pair of electrical spring elements cooperabl with respective ones of a pair of electrical contacts. The

6. An assembly according to claim 5, wherein electrical spring elements are provided on opposing sides of the or a mechanical spring section.

7. An assembly according to any preceding claim, including one or more coil springs cooperable with one or more profiled sections.

'Is- '

8. An assembly according to any preceding claim, wherein the spring includes a plurality of leaf spring elements for providing different biasing actions.

9. An assembly according to claim 8, wherein the spring includes a first spring element operable to follow a mechanical cam surface of the profiled section for providing the mechanical action of the actuator and a second spring element operable to bias an electrical contact onto an electrical cam 10 surface of the profiled section.

10. An assembly according to any ones of claims 5 to 9, wherein the various spring sections are of different resilience.

11. A spring for a rotary switch including at least one spring element having a profile which provides a cam follower.

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

13. A spring for a rotary switch substantially as hereinbefore described with reference to and as illustrated in Figures 1 to 5 or 6a to 7 of the accompanying drawings.