GB2155240A - Electrical switches - Google Patents

Abstract

An electrical switch comprises a flexible carrier member (15) having two movable contacts (16, 17) carried thereby, the movable contacts being mounted on the carrier member to permit of movement relative thereto. The movable contacts (16, 17) each contact fixed contacts (11, 12) when the carrier member (15) is in one stable position. First biasing means (18) biases the carrier member into the one stable position and further biasing means 27 acts on the first and second movable contacts to control movement of the contacts relative to the carrier. The arrangement assists in a swift make and break of the switch. <IMAGE>

Description

SPECIFICATION Electrical switch and method of switching circuits One aspect of the present invention relates to a switch of the kind, hereinafter called the kind specified, having a body, fixed contacts mounted on the body, a contact carrier which is movable relative to the body and movable contacts on the carrier for co-operation with the fixed contacts, wherein the carrier is flexible and there is connected between spaced portions of the carrier biasing means for urging said portions towards each other. In a switch of the kind specified, the carrier is biased away from a configuration in which the spacing between said portions has a maximum vaiue towards either one of two alternative configurations (called herein stable configurations) in which the spacing has a lower value or respective lower values.

In a stable configuration of the carrier, certain of the fixed and movable contacts are held in contact with each other under pressure derived from the biasing means. When the carrier is in one of its stable configurations, the position of the movable contacts relative to the fixed contacts is firmiy controlled. However, in known switches of the kind specified, there is inadequate control of the position of the movable contacts relative to the fixed contacts when the configuration of the carrier is such that the biasing means is ineffective to urge the carrier strongly into either one of the stable configurations.

The carrier must assume such an intermediate configuration on each occasion when the configuration is changed between the two stable configurations and, accordingly, there is temporarily inadequate control of the position of the movable contacts during each operation of the switch.

According to a first aspect of the invention, there is provided a switch of the kind specified wherein at least one of said movable contacts is mounted on the contact carrier for limited movement relative thereto and there is provided further biasing means connected with said one contact for controlling movement of the contact relative to the carrier.

In a switch in accordance with the invention, the position of the one movable contact is subject to control by both the contact carrier and the further biasing means. When control exercised by the contact carrier is inadequate, adequate control is exercised by the further biasing means.

According to a further aspect of the invention, there is provided a method of changing the condition of each of two electrical circuits, each of which circuits comprises a pair of fixed switch contacts, wherein a flexible contact carrier carrying respective movable contacts for bridging said contacts of each pair of fixed contacts is flexed from a first configuration in which it holds the movable contacts in respective first positions, through an intermediate configuration to a second configuration in which it holds the movable contacts in respective second positions, wherein, during flexing of the carrier from the first configuration to the intermediate configuration, the movable contacts remain substantially stationary relative to the fixed contacts and the carrier undergoes limited movement relative to the movable contacts, and wherein continued flexing of the carrier beyond the intermediate configuration moves the movable contacts relative to the fixed contacts to change the condition of each said circuit.

An example of a switch embodying the first aspect of the invention which is used in a method in accordance with the second aspect of the invention, will now be described, with reference to the accompanying drawings, wherein: Figure I shows a perspective view of the switch; and Figure 2 shows a perspective view of certain parts of the switch isolated from the remainder of the switch.

The switch shown in the drawings comprises a body 10 which is formed of an electrically insulating material and which may be provided with a housing (not shown). Four pairs of fixed contacts are mounted on the body 10. As viewed in Figure 1, these comprise a lower left-hand pair of contacts 11, a lower right-hand pair of contacts 12, an upper left-hand pair of contacts 13 and an upper right-hand pair of contacts 14.

The switch further comprises a flexible contact carrier 15 formed of resilient material and having an elongated form. The carrier may be formed of metal, for example a berilium-copper alloy. A left-hand pair of movable contacts 16 is mounted on the carrier adjacent to one end thereof, these contacts being connected electrically with each other by a conductor and being arranged to bridge either the contacts 11 or the contacts 13, depending on the configuration of the carrier 15. A similar pair of right-hand movable contacts 17 is provided on the carrier for bridging the contacts 12 or the contacts 14, also depending upon the configuration of the carrier.

Biasing means in the form of a pair of coiled tension springs 18 is provided for biasing the carrier into either one of two stable configurations, in one of which the contacts 11 and 12 are bridged, and in the other of which the contacts 13 and 14 are bridged.

For changing the configuration of the carrier, there is provided a spring-loaded plunger 20 guided in the body 10 for reciprocation along a path parallel to the general direction of movement of the contacts 16 and 17 and engaged with a mid-portion of the carrier 15.

Opposite end portions 21 and 22 of the carrier 15 have a width somewhat greater than that of the mid-portion of the carrier and the springs 18 are engaged with these end portions to urge the end portions towards each other. Certain examples of known switches of the kind specified each have contacts, a contact carrier and biasing springs arranged generally in the manner hereinbefore described. Thus, the general arrangement and form of some components of the switch shown in the accompanying drawing may be similar to those of known switches and the same materials may be used for corresponding components.

The switch illustrates in the accompanying drawing differs from known switches of the kind specified primarily in two respects, namely the manner in which the movable contacts are connected with the carrier 15 and in the provision of additional biasing means.

In known switches of the kind specified, the movable contacts are normally rigidly connected with the contact carrier. This facilitates control the position of the movable contacts by the contact carrier. Control over the movable contacts is impor tant in the achievement of satisfactory operation of the switch and of a satisfactory service life. In the switch illustrated in the accompanying drawings, the movable contacts 16 and 17 are not rigidly con nected with the carrier 15 but are so connected with the carrier that limited movement of each pair of movable contacts relative to the carrier can occur.

The arrangment is preferably such that universal movement, by which we mean movement about three mutually perpendicular axes, can occur. In some cases, more restricted freedom for relative movement will be satisfactory.

The movable contacts 16 are rigidly secured to an end member 23 defining a slot in which the end portion 21 of the carrier is received with some clearance. The end portion is retained in the slot by means of a pin 24 which extends through aligned apertures in the end member 23 and end portion 21.

Limited relative pivoting of the end member and end portion about the axis of the pin 24 can occur. The pin is captive in one of the end portion 21 and end member 23 and is a loose fit in the other, so that there is freedom for relative movement which is limited by engagement of the end portion 21 with boundaries of the slot in the end member 23. A corresponding end member 25 is provided for the contacts 17 and is connected with the end portion 22 in a corresponding manner.

The further biasing means comprises two coiled springs 27 and 28, each of which is connected between the end member 23 and the end member 25 and is normally stressed in tension. The springs 27 and 28 lie adjacent to respective ones of the springs 18, with the latter springs and the mid-portion of the carrier 15 lying between the springs 27 and 28. Each of the end members 23 and 25 is provided with a pair of limbs 29 to 32, each limb extending from the vicinity of an associated one of the movable contacts in a direction towards the other end member. The springs 27 and 28 are engaged with free end portions of the limbs 29 to 32 at positions which are somewhat nearer together than are the end portions 21 and 22 of the carrier. The limbs 29 to 32 are flexible, relative to the remainder of the end mem bers 23 and 25.

The mid-portion of the carrier 15 is urged upward ly by the spring 33 associated with the plunger 20 so that the carrier normally assumes a configuration in which it is arched upwardly, as viewed in Figure 1, and the movable contacts 16 and 17 are held on the lower contacts 11 and 12 respectively. This is one stable configuration of the carrier and departure of the carrier from this configuration is necessarily accompanied by further stressing of the springs 18.

Thus, when the carrier is in this first stable configura tion, the springs 18 urge the movable contacts against the contacts 11 and 12 under substantial pressure. Respective circuits (not shown) connected with the contacts 11 and 12 are closed when the carrier is in its first stable configuration, whilst respective circuits connected with the contacts 13 and 14 are open.

The condition of the circuits can be changed by pressing the plunger 20 inwardly of the body 10 to reduce thë upward arching of the carrier 15. In this way, the carrier can be caused to adopt an intermediate configuration in which it is neither arched predominently upwards, nor arched predominently downwards. As the configuration of the carrier is changed from the first stable configuration to the intermediate configuration, the movable contacts 16 and 17 remain firmly engaged with the lower contacts 11 and 12 and limited movementofthe carrier relative to the end members 23 and 25 occurs.

Thus, although, when the carrier has its intermediate configuration, it is not strongly urged by the springs 18 towards either one of its stable configurations, the circuits connected with the lower contacts 11 and 12 remain closed and the circuits connected with the upper contacts 13 and 14 remain open.

If depression of the plunger is continued, to change the configuration of the carrier 15 from the intermediate configuration towards a second stable configuration in which the carrier is arched downwardly, the springs 18 urge the carrier strongly towards its second stable configuraton, which is adopted abruptly, and the movable contacts 16 and 17 are withdrawn abruptly from the lower contacts 11 and 12 and moved into firm engagement with the upper contacts 13 and 14.

The arrangement maintains pressure between the movable contacts 16,17 and the lower contacts 11, 12 until these contacts are separated. Separation from the contacts 11 and from the contacts 12 occurs simultaneously.

The springs 18 are selected to apply to the end portions 21 and 22 of the carrier forces which are considerably greater than the forces applied to the end members 23 and 25 by the springs 27 and 28, in any given condition of the switch. Accordingly, once the springs 18 strongly urge the carrier towards one of its stable configurations, the springs 27 and 28 do not interfere significantly with change in configuration of the carrier.

Small variations in the positions of the fixed contacts do not affect operation of the switch, because the pressure between fixed and moving contacts is not dependant solely on the spring 18.

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, as apropriate, may, separately or any cornbination of such features, be utilised for realising the invention in diverse forms thereof.

Claims (6)

1. A switch of the kind specified wherein at least one of said movable contacts is mounted on the carrier for limited movement relative thereto and there is provided further biasing means connected with said one contact for controlling movement of the contact relative to the carrier.

2. A switch according to Claim 1 wherein said one movable contact is arranged for limited universal movement relative to the carrier.

3. A switch according to Claim 1 or Claim 2 wherein the contacts of the switch include a first pair of fixed contacts adjacent to one of said portions of the carrier, a second pair of fixed contacts adjacent to the other of said portions of the carrier, a first movable contact or pair of movable contacts which bridge the first pair of fixed contacts when the carrier is in one stable configuration, a second movable contact or pair of moable contacts which bridge the second pair of fixed contacts when the carrier is in the one stable configuration and wherein both the first and second movable contacts or pairs of movable contacts are mounted on the carrier for limited movement relative thereto and wherein the further biasing means acts between the first and second movable contacts or pairs of movable contacts

4.A method of changing the condition of each of two electrical circuits, each of which circuits comprises a pair of fixed switch contacts, wherein a flexible contact carrier carrying respective movable contacts for bridging said contacts of each pair of fixed contacts is flexed from a first configuration in which it holds the movable contacts in respective first positions, through an intermediate configuration to a second configuration in which it holds the movable contacts in respective second positions, wherein, during flexing of the carrier from the first configuration to the intermediate configuration, the movable contacts remain substantially stationary relative to the fixed contacts and the carrier undergoes limited movement relative to the movable contacts, and wherein continued flexing of the carrier beyond the intermediate configuration moves the movable contacts relative to the fixed contacts to change the condition of each said circuit.

5. A switch substantially as herein described with reference to and as shown in the accompanying drawings.

6. Any novel feature or novel combination of features disclosed herein and/or shown in the accompanying drawings.