GB2148599A

GB2148599A - Electric switches

Info

Publication number: GB2148599A
Application number: GB08328314A
Authority: GB
Inventors: S J H Fletcher; I V Pickering
Original assignee: Crabtree Electrical Industries Ltd
Current assignee: Crabtree Electrical Industries Ltd
Priority date: 1983-10-22
Filing date: 1983-10-22
Publication date: 1985-05-30
Also published as: GB8328314D0; ZA848155B

Abstract

An electric switch comprises a base (6) adapted to be secured by screws to a horizontal or vertical surface, and a body (8) secured to the base, the base and body affording a housing for the switch mechanism. The switch mechanism comprises a contact mechanism (10), comprising a pair of fixed contacts (16,18), a moving contact (28), and compression springs (34,36), engaging the contact member (28). The switch mechanism also comprises an operating mechanism (12) mounted in a central aperture (38), which may be rotated about its longitudinal axis by a pull cord (42), and returned to a rest position by a spring (46). The operating mechanism (12) carries an actuator mechanism (14), comprising a spindle (52), and at least one actuator member (54) which may be mounted on the spindle (52) in one of two orientations. By pulling of the cord (42) the actuator member (54) is rotated to actuate the moving contact (28). The actuator mechanism (14) may be rotatable with the operating mechanism (12) in one direction but not the other to constitute a pull pull switch or may be secured to the operating mechanism (14) to constitute a retractive switch. <IMAGE>

Description

SPECIFICATION Improvements relating to electric switches This invention is concerned with improvements relating to electric switches, particularly of the kind (hereinafter referred to as being of the kind specified) comprising a housing adapted to be secured to a surface, at least one contact assembly in the housing and comprising a pair of terminals, and a contact member movable between the terminals between "make" and "break" positions, and operating mechanism actuated by a pull cord to move the contact member between said positions.

Switches of the kind specified are conventionally complicated and/or cumbersome in their construction.

According to a first aspect of this invention, there is provided a switch of the kind specified, wherein the operating mechanism comprises an operating member mounted in the housing for rotation, the pull cord being connected to the operating member in a manner such that pulling of the cord effects rotation of the operating member in a first direction, return means being provided to urge the operating member in a second, opposite direction, an actuator member carried by or connected to the operating member in a manner such that on movement of the operating member in one of said directions, the actuator member moves to move the operating member, or to permit the operating member to move, between its "make" and "break" positions.

Advantageously, the operating member is mounted in the housing for rotation about a longitudinal axis, and conveniently the pull cord is secured to the operating member and extends around a pulley means of the operating member. Preferably the return means is afforded by an extensible element which is also secured to the operating member and which extends around a pulley means on the operating member, conveniently being secured at its opposite end to the switch housing.

The actuator member may be secured directly to the operating member, but advantageously is afforded by an actuator mechanism mounted for rotation about said longitudinal axis, conveniently for such rotation both with, and relative to, the operating member.

Thus advantageously the actuator mechanism is in the form of a spindle mounted coaxially through the operating member in a manner such as to enable relative rotation to take place, advantageously drive means being provided selectively to cause the actuator member to rotate with the operating member in one direction of movement thereof, and to permit the actuator member to remain stationary relative to the operating member in the other direction of movement thereof.

Preferably the actuator member is in the form of a cam member mounted on the spindle, and preferably the switch comprises two contact mechanisms and the actuator mechanism comprises two actuator members mounted on the spindle. Preferably the orientation in which the actuator members are mounted on the spindle can be selected whereby movement of the contact members in response to operation of the switch may be selected.

Difficulty is also encountered in switches of the kind specified in the provision of simple and reliable contact mechanisms.

According to a second aspect of this invention, there is provided, in or for a switch of the kind specified, a contact mechanism comprising a pair of fixed contacts, a contact member comprising movable contacts, first spring means operative at one end portion of the contact member to urge a first of the moving contacts into engagement with one of the fixed contacts, and second spring means operative at a position intermediate the moving contacts to urge the contact member towards its "make" position.

Preferably the first of the moving contacts and the corresponding fixed contact are designed so as to facilitate pivotal movement of the contact member between its "make" and "break" positions. Thus said first moving contact may be in the form of a knife edge urged into engagement with the fixed contact by said first spring means, or alternatively the fixed contact may provide a knife edge against which the first moving contact is urged.

Preferably said contact mechanism is mounted in a switch in a location such that an actuator member is adapted to engage the contact member at a location also intermediate the moving contacts thereof, preferably adjacent to the line of action of the second spring means. advantageously slightly closer to the second moving contact. In this manner, normal operation of the switch will consist of movement of the contact member about its pivot point, retaining the first moving and corresponding fixed contacts in engagement, but on (for example) welding of the second moving and corresponding fixed contacts, movement of the contact member by the actuator member will produce separation of the first moving and corresponding fixed contacts.

Difficulty is also encountered in switches of the kind specified by the number of functions such a switch may be required to perform. For example, a switch of the kind specified may be required to perform. For example, a switch of the kind specified may be required which is one-way, double or single pole, two-way or two-way retractive. Heretofore switches have not readily been capable of fulfilling several of these requirements without undue complexity and/or expense in construction.

According to a third aspect of this invention, there is provided a kit of parts for a switch of the kind specified comprising an actuating mechanism comprising a support member mounted for rotation about a longitudinal axis, and two actuator members adapted for mounting on the support member, location means being provided which enables each actuator member to be mounted on the support member in one of at least two orientations.

Preferably the switch comprises two pairs of contact mechanisms for actuation by respective actuating members.

In this manner. the phase relationship between the two actuator members may be selected in accordance with the type of switch desired. Where it is desired that the switch be one-way, one of the actuator member may be omitted, or one pair of contact mechanisms may be unwired, or the contact mechanisms may be wired in parallel.

There will now be given a detailed description, to be read with reference to the accompanying drawings, of an electric switch which is a preferred embodiment of this invention and which has been selected for the purposes of illustration by way of example.

In the accompanying drawings: Figure 1 is a front elevation of the switch which is the preferred embodiment of this invention a pull cord and cover thereof having been removed; Figure 2 is a rear elevation of said switch; Figure 3 is a sectional view taken on the line A-A of Fig. 1; Figure 4 is a sectional view taken on the line C-C of Fig. 1; Figure 5 is a sectional view taken on the line D-D of Fig. 1; Figure 6 is a sectional view taken on the line E-E of Fig. 1; Figure 7 is a sectional view taken on the line B-B of Fig. 1; Figure 8 is an enlarged perspective view of a sub-assembly of the switch comprising operating mechanism and actuator mechanism thereof; Figures 9a and 9b illustrate schematically the wiring of the switch in a single pole application; Figures 10a and 10b illustrate schematically the wiring of the switch in a two-way application;; Figures 1 lea and 1 ib illustrate schematically an alternative wiring of the switch in a two-way application; Figures 12a and 12b illustrate schematically the wiring of the switch in a double pole application; and Figure 13 and 14 are views corresponding to Figs. 3 and 6 showing the use of the invention in a two-way retractive application.

The switch which is the preferred embodiment of this invention comprises a base 6, adapted to be secured by screws to a surface (which may be a wall or other vertical surface of a horizontal surface such as a ceiling) and a body 8 secured to the base, the base and body affording a housing for the switch mechanism. The base is provided with apertures 7a and 7b through which wiring may extend into the interior of the switch.

Mounted over the body 8 is a cover 9, the cover comprising a central aperture through which a pull cord may extend.

The switch mechanism comprises contact mechanism 10 (Fig. 6), an operating mechanism 12 (Fig. 8) and an actuator mechanism 14 (also Fig. 8).

The contact mechanism comprises a pair of fixed contacts 1 6 and 1 8 mounted in recesses 20, 22 resepctively in the body. each contact comprising a terminal 24. 26 respectively to which external wiring may be secured, see Figs. 1 and 4. Also provided on the body is an earth terminal 27, to which earth wiring may be connected.

The contact mechanism also comprises a moving contact member 28 (Fig. 6) mounted in a recess of the base, the contact member 28 being elongate and having contacts 30 and 32 at end portions thereof. the contact 30 being in the form of a knife edge. The contact mechanism also comprises first and second spring means, afforded by compression springs 34 and 36 respectively, the first of which engages the contact member adjacent to the contact 30 to urge the contact 30 against the contact 16, and the second of which urges the contact member at a point intermediate its end portions to urge the second contact 32 against the contact 1 8.

The base and body define a central aperture 38 of generally circular cross-section in which a generally cylindrical operating member 40 of the operating mechanism is mounted. A pull cord 42 of the switch extends in a circular groove 44 (affording pulley means) of the member 40, being anchored thereto at one end (Fig. 4) whereby on pulling of the cord, the member 40 is rotated about its longitudinal axis in a clockwise direction. A tension spring 46 extends in an adjacent circumferential groove 48, affording further pulley means, one end of the spring being anchored to a lug 50 of the member 40, and being secured at its opposite end to the body 8 by a pin 51.

The spring 46 urges an arcuate formation 41 of the operating member into engagement with a first abutment surface (Fig. 7), whilst movement by the pull cord 42 rotates the operating member into engagement with a second abutment surface, such angular movement being limited to a little over 90 .

The actuator mechanism 14 comprises a support member in the form of a spindle 52 extending axially through the operating member 40, being capable of rotary movement relative thereto. Opposite end portions of the spindle are non-circular, specifically generally rectangular in cross-section, being provided with location recesses 53 on adjacent sides thereof, said recesses being off-set by a subtended angle of 90 . Mounted on one end of the spindle 52, being that which extends adjacent to the contact mechanism, is an actuator member 54. The actuator member 54 is generally rectangular in outline having one side larger than the other, and is provided with a central aperture complementary to the end portions of the spindle.The actuator member is also provided with a location protrusion 56 extending into said aperture, which enables the member 54 to be mounted on the spindle in one of two orientations mutually off-set by 90 , with the protrusion 56 extending into one of the location recesses 53.

A circumferential portion of the spindle adjacent to a side face 58 of the operating member 40 is afforded with four teeth 60, and mounted in said side face 58 is a leaf spring 62. The leaf spring bears against the circumferential surface of the spindle and permits movement of the operating member relative to the spindle in an anti-clockwise direction (Fig. 7) but on movement of the operating member in a clockwise direction, abutment of the leaf spring with a radial face of one of the teeth drives the spindle around with the operating member.

In the mounting of the switch, wiring is passed through the apertures in the base, and the base is secured to the surface, the wiring being connected to the terminals 24 and 26.

The body is mounted on the base, and the cover is secured to the body. Assuming the switch initially to be in the condition shown in Fig. 6, with the contact member in its "make" position, on pulling of the cord 42 the operating member is rotated through slightly more than 90 , the drive means afforded by the leaf spring 52 together with the teeth 60 causing the actuating member 54 to rotate through a similar angle, lifting the contact member 28 and moving the contact 32 from engagement with the contact 18. The latter part of the movement of the actuator member 54 will involve a small amount of movement of the contact member 28 back towards its "make" position.

On release of the pull cord, the spring 46 returns the operating member to its original position. However the restraint to return movement of the support spindle 52, which is afforded by the requirement to move the contact member against the action of the spring 36, is sufficient to allow the operating member to rotate relative to the spindle, causing compression of the leaf spring 62 as the teeth 60 of the spindle move thereacross.

Thus on return of the operating member to its original position, the actuating member is retained in a position off-set by 90' from the position shown in Fig. 6, in which it retains the contact member in its "break" position.

On a further pulling of the pull cord, the actuator member is again rotated through 90 initially lifting the contact member further outwardly and then allowing it to return to the position shown in Fig. 6. Again, the force required to lift the contact member for rotation of the actuator member to occur is sufficient to cause the drive means to permit relative rotation to take place between the operating and actuating members on return of the former to its rest position.

Should in the operation of the switch the contacts 1 8 and 32 become welded together, operation of the switch will similarly cause opening of the circuit by separation of the contacts 1 6 and 30.

The above description is of the preferred embodiment as a single pole switch, in which live and neutral wires are fed through the aperture 7a in the base and connected to the terminals 24 and 26, the earth wire being connected to the earth terminal 27, as is shown in Figs. 9a and 9b.

The switch may however be used as a double pole switch. A second contact mechanism, 1 Ob, similar to the contact mechanism 10. is utilised as is shown in Fig. 13, comprising fixed contacts 1 6b and 1 8b mounted in the body 8, and moving contact member 28b mounted on the base 6. A second actuator member 54b, similar to the actuator 54 is mounted on an end portion of the support spindle 52 in phase with the actuator member 54, whereby on pulling of the cord. both of the moving contact members are moved simultaneously between their "make" and "break" positions. In such circumstances, the live and neutral wires of the supply are connected to the terminal 24 and corresponding terminal 24b of the fixed contact 1 6b, and the wires of the delivery circuit are connected to the terminals 26 and 26b, as is shown in Figs. 1 2a and 1 2b.

Alternatively, by rotation of the second actuator member 54b through 90 relative to the actuator member 54 (by the utilisation of the alternative location recess for the location protrusion) the switch may be used as a twoway switch, as is shown in Figs. 1 0a and 1 0b. In this application, the live supply wire may be connected to the terminal 24b. which is bridges with the terminal 26b (or the live supply wire may be connected to both said terminals) and the two output wires are connected each to one of the terminals 24 and 26. Operation of the switch thus causes one of the contact members to move to its "make" position whilst the other moves to its "break" position, and vice-versa. If desired.

the output wires may be connected to the terminals 24 and 26 of a second similar switch remote from the first switch, to enable the condition of the appliance to be altered by operation of either switch.

Figs. 11 a and 11 b show an alternative wiring system for this two-way application.

Further. the switch may be used for period energisation, such as is required in what are known generically as "bell pull" applications.

Thus, two actuator members 54c and 54d are secured to the support spindle in a 90 phase relationship, and the actuator mechanism is made integral with. or otherwise rigid with, the operating mechanism. Thus. on operation of the pull cord, the actuator mechanism is moved through 90= to the position shown in Fig. 13 and 14, allowing the moving contact member 28a to move from its "break" to its "make" position, and causing the member 28b to be moved from its "make" to its "break" position. On release of the pull cord, the tension in the spring 46 will return the contact members to their original positions.

Such a switch is known as a "two-way retractive" switch.

In the application illustrated in Figs. 1 3 and 14, desirably actuator members are utilised which are in for form of "snail" cams. Since the contact member 28a is normally open, and the contact member 28b is normally closed, it is necessary to profile the cams in a manner such as to ensure that the member 28a opens before the memdber 28b closes.

Additionally, the profiling of the cam 54d shown in Fig. 1 3 assists the spring in moving the switch mechanism to its rest condition.

It will be appreciated that in the embodiments above described, the switch housing, comprising base 6 and body 8 secured thereto, may be placed close to the surface to which it is to be mounted, with the cable or cables extending through one or more both apertures 7, enabling the switch housing to be secured to the surface, and surplus wire pulled therethrough. Insulating material may be cut from the cable to bare the conductor of the cable, and the conductor may be connected to the terminal means with the switch housing secured firmly in position, the cover 9 being mounted over the switch body when said wiring operation has been completed.

Claims

CLAIMS:

1. A switch of the kind specified, wherein the operating mechanism comprises an operating member mounted in the housing for rotation, the pull cord being connected to the operating member in a manner such that pulling of the cord effects rotation of the operating member in a first direction, return means being provided to urge the operating member in a second opposite direction, an actuator member carried by or connected to the operating member in a manner such that on movement of the operating member in one said directions, the actuator member moves to move the operating member, or to permit the operating member to move, between its "make" and "break" positions.

2. A switch according to Claim 1 wherein the operating member is mounted in the housing for rotation about a longitudinal axis.

3. A switch according to one of Claims 1 and 2 wherein the pull cord is secured to the operating member and extends around a pulley means of the operating member.

4. A switch according to any one of the preceding claims wherein the return means is afforded by an extensible element which is secured to the operating member and which extends around a pulley means on the operating member.

5. A switch according to Claim 4 wherein the return means is secured as its opposite end to the switch housing.

6. A switch according to any one of the preceding claims wherein the actuator member is secured directly to the operating member.

7. A switch according to any one of Claims 1 to 5 wherein the actuator member is afforded by an actuator mechanism mounted for rotation about a longitudinal axis for rotation both with, and relative to, the operating member.

8. A switch according to Claim 7 wherein the actuator mechanism is in the form of a spindle mounted coaxially through the operating member in a manner such as to enable relative rotation to take place.

9. A switch according to Claim 8 wherein drive means is provided selectively to cause the actuator member to rotate with the operating member in one direction of movement thereof, and to permit the actuator member to remain stationary relative to the operating member in the other direction of movement thereof.

10. A switch according to one of Claim 8 to 9 wherein the actuator member is in the form of a cam member mounted on the spindle.

11. A switch according to any one of the preceding claims comprising two contact mechanisms, and the actuator mechanism comprises two actuator members.

1 2. A switch according to Claim 11 wherein the orientation in which the actuator members are mounted may be selected whereby movement of the contact members in response to operation of the switch may be selected.

1 3. In or for a switch of the kind specified, a contact mechanism comprising a pair of fixed contacts, a contact member compris ing movable contacts, first spring means oper ative at one end portion of the contact mem ber to urge a first of the moving contacts into engagement with one of the fixed contacts, and second spring means operative at a position intermediate the moving contacts to urge the contact member towards its "make" posi tion.

14. A contact mechanism according to Claim 1 3 wherein the first of the moving contacts and the corresponding fixed contact are designed so as to facilitate pivotal movement of the contact member between its "make" and "break" positions.

1 5. A contact mechanism according to Claim 1 4 wherein the first moving contact is in the form of a knife edge urged into engagement with the fixed contact by said first spring means.

1 6. A contact mechanism according to Claim 1 4 wherein the fixed contact is provided by a knife edge against which the first moving contact is urged.

1 7. A switch comprising a contact mechanism according to any one of Claims 1 3 to 16, said contact mechanism being mounted in a location such that an actuator member of the switch is adapted to engage the contact member at a location also intermediate the moving contacts thereof.

1 8. A switch according to Claim 1 7 wherein the actuator member is adapted to engage the contact member at a location adjacent to the line of action of the second spring means.

19. A switch according to Claim 18 wherein the location is slightly closer to the second moving contact.

20. A kit of parts for a switch of the kind specified, comprising an actuating mechanism comprising a support member mounted for rotation about a longitudinal axis, and two actuator members adapted for mounting on the support member, location means being provided which enables each actuator member to be mounted on the support member in one of at least two orientations.

21. A kit of parts according to Claim 20 comprising two pairs of contact mechanisms adapted for actuation by respective actuating members.

22. A switch of the kind specified, constructed and arranged substantially as hereinbefore described with reference to the accompanying drawings.

23. In or for a switch of the kind specified, a contact mechanism constructed and arranged substantially as hereinbefore described with reference to the accompanying drawings.

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