GB2106323A - Electric switch dolly having a variable cam configuration - Google Patents

Abstract

A dolly (10a, 10b) for opening or closing the electrical contacts in a cord operated pull/pull switch comprises two parts each having a contact engaging camming surface (20a, 20b) thereon. One part is removable from the other and reversible so that the position of its camming surface may be altered relative to that of the camming surface on the other dolly part. Two contact pairs (5a, 6 and 5d, 6, Fig. 3 not shown) may thereby be cammed closed either together or alternately. <IMAGE>

Description

SPECIFICATION An improved electrical switch and actuating member therefor This invention relates to electrical switches having an operating dolly which is rockable to actuate the electrical contacts of the switch, and more particularly but not exclusively to electrical switches of the pull/pull type in which the cord attached to the operating mechanism is pulled to operate the switch and pulled again, in the same direction, to switch it off. The invention also relates to an operating dolly for fitting to such switches.

Pull/pull switches are known wherein a hook member to which an actuating cord is connected is alternately engageable with an operating dolly rockable between two different positions so that cam lobes thereon open or close the electrical contacts of the switch. The operating dolly of such switches is normally formed as a one-piece moulding which means that a particular dolly has to be designed for each switch function. For instance, if the switch assembly is to work as a two way single pole switch, one form of dolly will be required whereas another differently shaped dolly will be needed if the switch is to work as a double pole switch.

Having to make individual dollies for the various switch types increases manufacturing costs so it is an object of the invention to provide a more versatile dolly which can be readily adapted to operate more than one type of switch.

According to one aspect of the invention there is provided a switch dolly for actuating the electrical contacts of a switch wherein the dolly is pivotable about an axis and formed in two parts, each part having a camming surface thereon adapted to open or close the switch contacts, one dolly part being removable from the other and being reversible so that when it is refitted on said one dolly part, the positions of the camming surfaces relative to each other are altered thereby enabling the operating characteristics of the switch dolly to be readily changed.

Preferably the pivot axis is located centrally of the dolly and transverse thereto.

Conveniently, one dolly part is provided with an upstanding projection shaped to cooperate with biassing means on the switch, when fitted thereto, to bias the dolly into a pivotted position on one side or the other of the pivot axis.

In a preferred embodiment, one dolly part is formed with a cavity therein which is closed when the other dolly part is fitted thereon, said one dolly part also having an aperture therein to provide access to said cavity when the two dolly parts have been assembled together.

Desirably, the pivot axis protrudes into the cavity and the upstanding projection is formed with a recess on either side of a central apex.

Preferably each camming surface has an apex, the two apices being aligned across the width of the dolly when the two dolly parts are fitted together in a first assembled condition but being out of alignment when the removable dolly part is reversed and the dolly reassembled, the apex of each camming surface being offset with respect to the pivot axis of the dolly to provide it with an over-centre action.

According to another aspect of the invention, there is provided a pull/pull switch assembly, preferably cord operated, comprising a housing, a dolly pivotally mounted in the housing and provided with camming surfaces operable to open or close electrical contacts in the switch on pivotal movement of the dolly, means in the switch biassing the dolly into a pivoted rest position on one side or the other of its pivot axis, and a biassed movable actuating member operably associated with the dolly and arranged so that each movement of said member results in the dolly rocking from one position to another to open or close the switch contacts, the dolly formed in two parts, each part having one of said camming surfaces thereon, and one dolly part being removable from the other and being reversible so that when it is refitted on said one dolly part, the positions of the camming surfaces relative to each other are altered.

Conveniently, the dolly biassing means in the switch comprises a spring loaded button which cooperates with an upstanding projection on the dolly which is formed with a recess on either side of a central apex.

In a preferred arrangement, one dolly part is formed with a cavity therein which is closed when the pther dolly part is fitted thereon, said one dolly part also having an aperture therein to provide access to said cavity when the two dolly parts are assembled together.

Conveniently, the biassed dolly actuating member is arrow shaped with opposed hooks at its head, said member being mounted for sliding movement in a guide towards and away from the dolly against the action of the biassing force, the end of said member opposite the arrow shaped head being adapted to be connected to an operating cord, the arrow shaped head being located within said cavity, the dolly part containing the cavity being formed with oppdsed ledges on either side of its access opening for engagement by said hooks.

Preferably the arrow shaped actuating member is a loose fit in its guide so that it can pivot from side to side therein to engage, in use, with one or other of said opposed ledges in the cavity in the dolly.

For ease of operation, the arrow shaped member is preferably also provided with camming surfaces on either side thereof, each of which is adapted to engage and cooperate with one of said ledges whereby on movement of said member to actuate the switch, it is deflected from engagement with one ledge to engagement with the other.

Whilst the invention is primarily concerned with a two part dolly for fitting to a switch of the pull/pull type, and switches including such a dolly, it will be appreciated that the two part dolly can be readily used in any form of switch whose contacts are opened and/or closed by a rocking movement of its operating dolly, for instance a push/push or a single or double pole switch whose dolly is manually rocked by the user.

A preferred pull/pull switch assembly of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is an end view in cross section of a switch taken along the line I-I in Figure 3; Figure 2 is a side view in cross section of the switch of Figure 1 along the line Il-Il in Figure 3; Figure 3 is an undemeath plan view of part of the switch of Figures 1 and 2 but with the cover and certain other parts omitted for ease of illustration; and Figure 4 is a scrap view of the operating dolly of the switch of Figures 1 to 3.

Referring to the drawings, there is shown a pull/pull switch comprising a switch housing 1 attached by means of screws 2 to a cover 3. The illustrated switch housing receives and locates four terminal posts 4 by means of which wires from the appliance to be switched can be releasably secured. Each post has a projection therefrom which contacts an electrically conductive rocker bar 6, the projections 5a, Sb of the two posts on the lefthand side engaging with one rocker bar and those of the two posts 5c, 5d on the righthand side doing likewise with an identical rocker bar alongside. Each rocker bar 6 pivots about a coil spring 7 which it will be noted is offset with respect to the centre of the bar.This ensures that end 9 of each bar is always kept in contact with its terminal post projection 5 and allows end 8 to be depressed out of contact with its terminal posts 5 by dolly 10 to break the circuit in a manner to be described.

The dolly 10 is pivotally mounted for rocking movement about axle 11 (see Figure 3) whose ends are located in appropriately shaped recesses 12 in the housing 1 on either side of the dolly. The dolly is biassed into one or other of its positions by means of spring loaded button 13 which cooperates with one or other of recesses 14, 1 5 on either side of apex 1 6. Pivotal movement of the dolly 10 is restricted in either direction by engagement of its faces 17, 18 with the housing 1.

As can be more clearly seen from Figure 4, the dolly is also provided on either side of its central part 1 9 with a pair of cam surfaces 20a, 20b each of which cooperates with its own respective bar 6 to operate the switch in a manner which will be described shortly.

The switch assembly also includes an actuating mechanism to move the dolly 10 between its two positions and this comprises hook 21 having an arrow shaped head 22. The hook is slidingly mounted for vertical movement against spring 24 in a guide 23 which forms part of the cover 3. The hook has a hole 25 through one end thereof to receive cord 26, a cross bar 27 being located in a channel 36 (see Figure 1) in the guide 23 to guide the hook during its movement. The bottom of the hook 23 has a pair of oppositely inclined surfaces 28 for reasons to be explained.

The construction of the dolly 10 is more clearly illustrated in Figures 3 and 4 from which it can be seen that it is formed with an internal cavity 29 having a shoulder 30 on either side of an entrance 31 thereto. The dolly is formed in two parts 1 Oa, 1 or, the part 1 Ob having one of the cam surfaces 20 thereon and holes 33 in it which locate on pins 32 projecting from the other dolly part 1 Oa, preferably making a good fit therewith. Each dolly part 1 0a, 1 Oh also includes a hole 34 to receive the axle 11 about which it rocks.

As illustrated in Figure 4, apices 35a, 356 of the cam surfaces 20a, 20b are aligned with each other across the width of the dolly. However, if desired, the dolly part 1 Ob may be removed from the dolly part 1 Oa, reversed and replaced on the pine 32 whereby the cam surface 20b is offset with respect to the cam surface 20a. It should also be noted that the apices 35a, 356 are offset with respect to the pivot axis 11 of the dolly to provide them with an overcentre action.

The operation of the switch assembly is as follows: The switch assembly illustrated in Figure 2 is shown with the hook 21 in its intermediate position namely that which it adopts while there is tension on the pull cord 26. In this position, one of the hooks of arrow head 22 engages with one of the shoulders 30 at the mouth 31 of the dolly so the latter is pivotted ciockwise to its position shown in the drawing until surface 1 7 abuts the housing 1. This movement causes one or both of the cam surfaces 20a, 20h (depending on the way in which dolly part 1 Ob is positioned on the dolly) to depress one or both of the switch contact bars 6 out of contact with the terminal post contact projections 5a, 5d.

When in this position, the tip of the arrow head of the hook 21 is slightly to the right of the axle 11. However, when the tension on the cord 26 is released, the spring 24 urges the hook 21 upwardly and as the shoulder 30 slides along inclined portion 40 at the base of the hook, the tip 22 is deflected to the left. During this movement, the dolly is kept in its illustrated position by the action of the spring loaded button 1 3 cooperating with the recess 14. Once the arrow head reaches the axle 11 under the action of spring 24, because it is to one side thereof, it is deflected thereby to the other side of the dolly ready to engage with the other shoulder 30 when tension is applied to the pull cord again and the dolly 10 is pivotted anticlockwise until surface 1 8 abuts the housing 1 and the cycle can be repeated. This movement of the dolly causes the cam surfaces 20a, 20h to release their pressure on the contact bars 6 so they return under the action of springs 7 to their normally closed positions in contact with the terminal projections Sb, Sc.

As already explained, with the apices 35a, 35h of the dolly aligned with each other, both contact bars 6 will be moved simultaneously on actuation of the switch. If however, the illustrated switch is to operate as a two way single pole switch, terminal projections 5a and 5d can be connected together by means of an electrically conductive strap and the dolly part lOb is reversed on the dolly part 1 Oa so that the cam apices 35a and 35b are no longer aligned. Thus, movement of the dolly in one direction will cause cam 20a to depress one of the contact bars 6 out of contact with its terminal post projection while leaving the other bar 6 in contact with its terminal post projection.

Pivotting of the dolly in the other direction, reverses this and allows the previously closed contact to be opened and the previously open contact to be closed.

From the foregoing, it will be seen that by means of the simple expedient of forming the dolly 10 in two parts and making one part reversible, a switch assembly can be readily adapted during manufacture to operate either as a two way single pole switch (cams 20a,20b not aligned) or as a double pole switch (cams 20a, 20b aligned). In certain circumstances, the removable dolly part lOb may be omitted during assembly of the switch thereby enabling it to operate as a one pole one-way switch.

Claims (21)

1. A switch dolly for actuating the electrical contacts of a switch wherein the dolly is pivotable about an axis and formed in two parts, each part having a camming surface thereon adapted to open or close the switch contacts, one dolly part being removable from the other and being reversible so that when it is refitted on said one dolly part, the positions of the camming surfaces relative to each other are altered thereby enabling the operating characteristics of the switch dolly to be readily changed.

2. A switch dolly as claimed in claim 1 wherein the pivot axis is located centrally of the dolly and transverse thereto.

3. A switch dolly as claimed in claim 1 or claim 2, wherein one dolly part is provided with an upstanding projection shaped to cooperate with biassing means on the switch, when fitted thereto, to bias the dolly into a pivotted position on one side or the other of the pivot axis.

4. A switch dolly as claimed in any of claims 1 to 3, wherein one dolly part is formed with a cavity therein which is closed when the other dolly part is fitted thereon, said one dolly part also having an aperture therein to provide access to said cavity when the two dolly parts have been assembled together.

5. A switch dolly as claimed in any preceding claim wherein one dolly part is formed with locating holes adapted to cooperate with and fit on to corresponding pins protruding from the other dolly part.

6. A switch dolly as claimed in any of claims 4 to 6, wherein the pivot axis protrudes into the cavity.

7. A switch dolly as claimed in any of claims 3 to 6, wherein the upstanding projection is formed with a recess on either side of a central apex.

8. A switch dolly as claimed in any of the preceding claims, wherein each camming surface has an apex, the two apices being aligned across the width of the dolly when the two dolly parts are fitted together in a first assembled condition but being out of alignment when the removable dolly part is reversed and the dolly reassembled.

9. A switch dolly as claimed in claim 8, wherein the apex of each camming surface is offset with respect to the pivot axis of the dolly to provide it with an over-centre action.

10. A pull/pull switch comprising a housing, a dolly pivotally mounted in the housing and provided with camming surfaces operable to open or close electrical contacts in the switch on pivotal movement of the dolly, means in the switch biassing the dolly into a pivotted rest position on one side or the other of its pivot axis, and a biassed movable actuating member operably associated with the dolly and arranged so that each movement of said member results in the dolly rocking from one position to another to open or close the switch contacts, the dolly being formed in two parts, each part having one of said camming surfaces thereon, and one dolly part being removable from the other and being reversible so that when it is refitted on said one dolly part, the position of the camming surfaces relative to each other are altered.

11. A pull/pull switch as claimed in claim 10, wherein the dolly biassing means in the switch comprises a spring loaded button which cooperates with an upstanding projection on the dolly.

12. A pull/pull switch as claimed in claim 11, wherein the upstanding projection is formed with a recess on either side of a central apex.

13. A pull/pull switch as claimed in any of claims 10 to 12, wherein one dolly part is formed with a cavity therein which is closed when the other dolly part is fitted thereon, said one dolly part also having an aperture therein to provide access to said cavity when the two dolly parts are assembled together.

14. A pull/pull switch as claimed in any of claims 10 to 13 wherein one dolly part is formed with locating holes adapted to cooperate with and fit on to corresponding pins protruding from the other dolly part.

1 5. A pull/pull switch as claimed in claim 13 or claim 14, wherein the dolly is pivotable about an axle which protrudes into the cavity in the dolly.

16. A pull/pull switch as claimed in claim 15, wherein the biassed dolly actuating member is arrow shaped with opposed hooks at its head, said member being mounted for sliding movement in a guide towards and away from the dolly against the action of the biassing force, the end of said member opposite the arrow shaped head being adapted to be connected to an operating cord.

17. A pull/pull switch as claimed in any of claims 1 3 to 16, wherein the arrow shaped head of the actuating member is located within said cavity, the dolly part containing the cavity being formed with opposed ledges on either side of its access opening for engagement by said hooks.

18. A pull/pull switch as claimed in claim 17, wherein the arrow shaped actuating member is a loose fit in its guide so that it can pivot from side to side therein to engage, in use, with one or other of said opposed ledges in the cavity in the dolly.

19. A pull/pull switch as claimed in claim 18, wherein the arrow shaped member is also provided with camming surfaces on either side thereof, each of which is adapted to engage and cooperate with one of said ledges whereby on movement of said member to actuate the switch, it is deflected from engagement with one ledge to engagement with the other.

20. A pull/pull switch substantially as herein described with reference to Figures 1 to 3 of the accompanying drawings.

21. A switch dolly substantially as herein described with reference to Figure 4 of the accompanying drawings.