GB2064223A

GB2064223A - An electrical switch

Info

Publication number: GB2064223A
Application number: GB8036805A
Authority: GB
Original assignee: Lucas Industries Ltd
Current assignee: ZF International UK Ltd
Priority date: 1979-11-22
Filing date: 1980-11-17
Publication date: 1981-06-10
Also published as: GB2064223B

Abstract

An electrical switch includes a housing 11 and an operating key 14 pivotally connected to the housing 11 for movement between rest and operating positions. A movable contact (19) is pivotally mounted in the housing 11 for movement by the key 14 from a first position, in which it engages a fixed contact (20), to a second position, in which it engages a fixed contact (21). A spring (22) attached between the housing 11 and the movable contact (19) urges the contact (19) towards its first position and serves to return the key 14 to its first position. The pivotal connection between the housing 11 and the key 14 includes a pair of pivot posts 12 formed integrally on housing 11 and pair of bores 13 in the key 14. Each bore 13 communicates with a respective slot 16 in a respective bifurcated portion 15 such that the portion 15 must be flexed to allow passage of the associated post 12 along the slot 16 to engage or disengage the post 12 from the bore 13. <IMAGE>

Description

SPECIFICATION An electrical switch This invention relates to an electrical switch of the kind including a housing, an operating key pivotally connected at one end thereof to the housing for angular movement relative to the housing between a rest position in the housing, a movable contact pivotally mounted in the housing for movement by the operating key from a first position, in which the movable contact is spaced from the fixed contact, and second position, in which the movable contact engages the fixed contact, and a spring urging the movable contract towards its first position and serving to return the operating key to its first position after operation of the key.

One known switch of the kind specified is disclosed in British Patent No. 1490800, in which the operating key is pivotally mounted on a separate pin which is attached to one end of the spring, while the other end of the spring is attached to the movable contact. However, this arrangement suffers from a number of assembly problems in that the steel pin must be accurately located in order to allow the operating key to engage the pin for the required pivotal movement relative to the housing. Moreover, it is difficult to assembly the steel pivot pin since the pin must be threaded through said one end of the spring while the spring is in tension and at the same time must be engaged with the switch housing.A further disadvantage of the switch disclosed in British Patent No. 1,490,800 is that the operating key is readily accidentally dislodged from the housing since the only retention of the key relative to the housing is provided by the pin being urged by the spring into a slot in the key. An object of the present invention is therefore to provide an improved switch of the kind specified.

Accordingly, the invention resides in an electrical switch of the kind specified, wherein one component of the two components defined by the housing and the operating key is formed integrally with a pair of coaxial pivot posts, and the other component is formed with a pair of bores in which said pivot posts are received to provide the pivotal connection between the housing and the operating key, each bore communicating with a respective slot defined in a respective bifurcated portion of said other component and the dimensions of each slot being such that each bifurcated portion must be flexed to allow passage of the associated pivot post along the slot to engage or disengage the pivot post from the bore, and wherein said spring is attached at one end to the housing and at its other end to said movable contact.

In the switch described in the preceding paragraph, assembly is simplified since the pivot posts are integral with either the housing or the operating key and hence require no separate alignment. In addition, assembly of the spring merely requires its attachment to the movable contact and the housing and hence is effected separately from the pivotal connection of the operating key to the housing. Moreover, sirrce the bifurcated portion of said other component must be flexed to allow disengagement of the pivot posts from their associated bores, the possibility of accidental removal of the operating key from the housing is reduced.

Preferably, the pivot posts are provided on the housing and the operating key defines said bores and said bifurcated portions.

Preferably, the slot defined by each bifurcated portion extends generally perpendicular to the axis of the pivot posts and the longitudinal axis of the operating key.

Preferably, each slot tapers outwardly at its open end to define a lead-in portion to facilitate engagement of the associated pivot post in the slot.

Preferably, the operating key includes a projection which engages and stresses the spring when the key is moved from its first position to its second position, the resultant stress in the spring providing the sole force to return the key back to its first position.

In the accompanying drawing, Figure 1 is a sectional view of an electrical switch according to one example of the invention, and Figure 2 is a side view of the switch shown in Figure 1.

Referrina to the drawings, the switch includes a generally rectangular two-part housing 11 which is moulded in a synthetic resin material, such as glass filled nylon. Projecting outwardly from opposite side walls respectively of the housing 11 are a pair of co-axial pivot posts 12 (only one shown) which are formed integrally with the housing 11 and which are received by respective bores 13 formed in an operating key 14 to mount the operating key for pivotal movement relative to the housing.

The operating key 14 is also moulded in a synthetic resin material, such as glass filled nylon, and at one end is formed integrally with a pair of laterally spaced, depending arms 1 5 (only one shown). The bores 13 are formed in the arms 1 5 respectively and at its free end each arm is bifurcated to define a slot 1 6 communicating with its associated bore 1 3. Each slot 1 6 extends generally perpendicular to the axis of the pivot posts 1 2 and the longitudinal axis of the operating key 14 and the width of each slot 1 6 along the majority of its length is arranged to be less than the diameter of each pivot post 12.Thus, the bifurcated ends of the arms 1 5 must be flexed to allow the pivot posts 12 to be moved along the slots 1 6 respectively to engage or disengage the pivot posts from the bores 1 3. In this way, it is possible to minimise the possibility of the operating key 1 4 being accidentally removed from the housing 1 Typically the switch is arranged so that a force of 1-2.5 Kg is required to flex the bifurcated ends sufficiently to allow the key 1 4 to be engaged with or disengaged from the pivot posts 1 5.

In order to facilitate assembly of the operating key onto the housing 11, the open end of each slot 1 6 preferably tapers outwardly to define a lead-in portion 17 for its associated pivot post 12.

Located in the housing 11 is a first fixed contact 18 which defines a pivotal mounting for a movable contact 19 so that the contact 1 9 is movable angularly relative to upper and lower second fixed contacts 20, 21 respectively.

Attached at one end to the movable contact 1 9 is a helical tension spring 22 which at its other end is attached to a pillar 23 integral with the housing 11. The spring 22 urges the movable contact 19 towards a stable first position in which it bridges the contacts 18, 20. Engaging the spring 22 is a spigot 24 which depends from the lower surface of the operating key 14 and which acts with the spring 22 to couple the key 14 to the movable contact 19. Thus the contact 1 9 is movable from its stable rest position into bridging engagement with the contacts 18,21 by imparting angular movement to the key 14 from said stable first position shown in the drawings to an unstable second position in which the lower surface of the key engages an inclined surface 25 of the housing 11.During this movement, the spring 22 is stressed by the spigot 24 and the resultant stress in the spring 22 provides the sole force for returning the key 14 back to its stable first position when the key is released.

By adopting the construction of the above example, assembly of the switch is facilitated since attachment of the spring can be effected separately from engagement of the operating key 14 with the housing 11 , while the latter merely involves pressing the bifurcated ends of the arms 1 5 over the pivot posts 1 2. Moreover, the use of the pivotal arrangement described allows the operating key 14 to be engaged with the housing 11 without the key 14 being accurately located so that its longitudinal axis is parallel with the longitudinal axis of the housing 14, an angle of up to 80 between said axes being acceptable.

The switch of the above example is particularly intended for use in audio equipment and, by virtue of its ease of assembly, the switch can conveniently be supplied to an equipment manufacturer with the operating key 14 separate from the remainder of the switch. Then, by providing the manufacturer with a number of operating key designs, the manufacturer is free to complete assembly of the switch with the most attractive key design for the particular item of equipment concerned.

Claims

1. An electrical switch including a housing, an operating key pivotally connected at one end thereof to the housing for angular movement relative to the housing between a rest position and an operating position, a fixed contact mounted in the housing, a movable contact pivotally mounted in the housing for movement by the operating key from a first position, in which the movable contact is spaced from the fixed contact, and a second position, in which the movable contact engages the fixed contact, and a spring urging the movable contact towards its first position and serving to return the operating key to its first position after operation of the key, wherein the pivotal connection between the housing and the operating key includes a pair of pivot posts formed integrally on one of the two components defined by the housing and the operating key and a pair of bores in the other component pivotally receiving the respective pivot posts, each bore communicating with a respective slot defined in a respective bifurcated portion of said other component and the dimensions of each slot being such that each bifurcated portion must be flexed to allow passage of the associated pivot post along the slot to engage or disengage the pivot post from the bore, and wherein said spring is attached at one end to the housing and at its other end to said movable contact.

2. An electrical switch as claimed in Claim 1, wherein the pivot posts are provided on the housing and the operating key defines said bores and said bifurcated portions.

3. An electrical switch as claimed in Claim 1, wherein the slot defined by each bifurcated portion extends generally perpendicular to the axis of the pivot posts and the longitudinal axis of the operating key.

4. An electrical switch as claimed in Claim 1 or Claim 3, wherein each slot tapers outwardly at its open end to define a iead-in portion to facilitate engagement of the associated pivot post in the slot.

5. An electrical switch as claimed in Claim 1, wherein the operating key includes a projection which engages and stresses the spring when the key is moved from its first position to its second position, the resultant stress in the spring providing the sole force to return the key back to its first position.