GB2121619A

GB2121619A - Switch

Info

Publication number: GB2121619A
Application number: GB08311886A
Authority: GB
Inventors: Philip Vernon Little
Original assignee: Lucas Industries Ltd
Current assignee: ZF International UK Ltd
Priority date: 1982-04-30
Filing date: 1983-04-29
Publication date: 1983-12-21
Also published as: GB8311886D0

Abstract

A switch of the kind comprising a housing having fixed contact means and a movable operating member which carries movable contact means has the fixed contact means formed by at least one fixed contact 18 made of resilient electrically conductive material which is bent to form a generally closed configuration in which the two ends of the strip overlap each other, one of said ends 16 a being formed with a slot or slit 17 so as to divide said end into contact portions 18 and 19 which can be used respectively in association with the adjacent end of the strip to grip and electrically connect conductors 25 and 26 of the same or different diameter. <IMAGE>

Description

SPECIFICATION Switch This invention relates to a switch which may be of the kind commonly known as a "slider" switch. Such a switch may be used for example to control the operation of electrically actuated tools such as drills, saws, hedge trimmers and other tools and one example of a "slider" switch is described in our copending application No. 82.12599 although the invention described in that application does not form any part of the invention which is the subject of the present application. The present invention does however relate to a switch which comprises a housing having fixed contact means and a movable switch operating member which carries movable contact means arranged in use to co-act with said fixed contact means.The latter are connected in use to electrical leads and hitherto difficulties have sometimes arisen in making a simple but effective electrical connection between a fixed contact and an electrical lead in cases where the latter incorporates two or more wires which each have to be connected to the contact but which are of different diameter.

The object of this invention therefore is to provide a switch in which a connection can be made in simple and efficient manner to a fixed contact in the circumstances outlined above.

In accordance with the invention there is provided a switch which comprises a housing having fixed contact means and a movable switch operating member which carries movable contact means wherein said fixed contact means includes at least one fixed contact formed from a strip of resilient electrically conductive material which is bent to form a generally closed configuration in which one end of the strip overlaps or lies closely adjacent to the other end of the strip, at least one of said ends being divided by one or more slots or slits which extend in directions generally parallel to the length of the strip and partway along the length thereof to form a plurality of contact portions, the arrangement being that one lead can be connected to the fixed contact by inserting its end between one of said contact portions formed at one end of said strip and the adjacent part of the other end of the strip so as to be frictionally retained therebetween, whereas another lead of the same or different diameter from the firstmentioned lead can be connected to the fixed contact by inserting its end between another of said contact portions formed at one end of said strip and the adjacent part of the other end of the strip so as to be frictionally retained therebetween.

There may for example be two of said contact portions which are formed by dividing one end of the resilient electrically conductive strip into two parts forming said portions by means of one slit or slot. The adjacent end of said strip may be formed with a centrally disposed longitudinally projecting tongue which overlies at least part of said slit or slot and which can be used to separate (in this case) the two leads which in use will be connected to the fixed contact.

The operating member of the switch comprises a slider which is longitudinally slidable in a slide-way formed in the housing of the switch and the movable contacts carried by said slider may comprise one or more electrically conductive rollers. Conveniently, the or each roller is located in an open-sided recess formed in the slider so that the periphery of the roller will project from the open sides of said recess and thus be adapted to engage the fixed contact means provided in the housing as the slider is moved in the housing. The or each roller may be retained in its co-acting recess by means of a capping strip which extends across the outer end of the roller and which is located and retained in position by means of inter-engaging projections and recesses formed in the slider and capping strip.

The capping strip also acts as a protective medium which prevents the or each roller from being eroded by sliding along the housing and depositing copper dust from the contacts, thus causing tracking and ultimately failure.

The invention will now be more particularly described with reference to the accompanying drawing wherein Figure 1 is a plan view of part of a switch housing (which includes a plurality of fixed contacts) and a switch operating member in the form of a slider (which includes a plurality of movable contacts) of a switch constructed in accordance with the invention, Figure 2 is an end view looking in the direction of arrow 'A' of one of the fixed contacts seen in Fig. 1, and Figure 3 is a sectional side view of the slider seen in Fig. 1.

Referring now to the drawings there is shown therein part of a switch housing which is indicated by reference numeral 10 and which is conveniently formed as a moulding in a synthetic resin material. The housing would be completed by another part (not shown) which would be placed on top of the housing part 10 shown in Fig. 1. The switch also includes a switch operating member in the form of a slider 11 which is adapted for longitudinal movement in a slide-way 1 2 formed in said housing part 10.

The aforesaid switch housing part 10 serves to locate fixed contact means in the form of four fixed contacts 13, 14, 1 5 and 16, contacts 1 3 and 1 4 being disposed on one side of said slide-way 1 2 and contacts 1 5 and 1 6 being disposed on the other side of said slideway. The contacts 1 5 and 1 6 are used for the connection of external leads and an end view of one of these fixed contacts namely contact 1 6 is shown in Fig. 2.Thus this contact (and also the similar contact 15) is formed from a resilient electrically conductive strip which is bent into a generally closed configuration, one part of such configuration bounding the slideway 1 2. Furthermore the two ends of the strip overlap or lie closely adjacent to each other as will be seen from Fig. 1. In addition at least one end of the strip is divided by one or more slots or slits which extend in directions parallel to the length of the strip and part-way along the length thereof to form a plurality of contact portions.In the example shown in the drawings one end, indicated by reference numeral 1 6a is so formed and this end has a slot 1 7 which is centrally disposed across the width of the strip and which extends in a direction parallel to the length of the strip, thus dividing said end of the strip into two contact portions 18 and 19.It is of course to be understood that instead of having a relatively wide slot 1 7 there may be formed a slit which will again have the effect of separating the end of the strip into the two portions 1 8 and 1 9. The other end of the strip which, as shown, lies closely adjacent to the slotted end of the strip is formed with a centrally arranged longitudinally projecting tongue 20 which overlies the outer end of said slot 1 7 and the remainder of said tongued end of the strip provides a pair of edges 21 and 22.From an examination of Fig. 2 it will be seen that, looking in the direction of Fig. 2, there is a gap between the edge 21 and the adjacent edge 23 of the contact portion 1 9 whilst there is a similar gap between the edge 22 and the adjacent edge 24 of the contact portion 18.

Each of these gaps is adapted to receive the bared end of a lead 25 or 26 which form part of a cable 27 entering the housing part 10 through an aperture 28 formed therein. The aforesaid tongue 20 will thus separate the two leads 25 and 26 and the resilient nature of the strip forming the contact 16 enables each of said leads to be firmly gripped and frictionally retained by the edges 22 and 24 on the one hand and by the edges 21 and 23 on the other hand. It will also be understood that because said contact portions 1 8 and 1 9 can flex relative to each other because of the presence of the slot 1 7 then leads of different diameters can be connected as above described with a firm grip being established on each lead.Hitherto without the individual contact portions as above described it has proved very difficult to connect satisfactorily two or more leads of different diameters because the smaller or smallest diameter leads may not be gripped sufficiently tightly.

For co-operating with the aforesaid fixed contacts 13, 14, 15 and 16 the slider 11 is provided with one or more movable contacts and in the example now described there are two such contacts which are each in the form of an electrically conductive roller 29 or 30 Each roller is located in a corresponding recess 31 or 32 formed in the slider and the two rollers are retained in position by means of a capping strip 33 which is conveniently formed from a synthetic resin material as is the slider 11. Said retaining strip 33 is formed with a pair of projections 34 and 35 which can be pressed into corresponding recesses 36 and 37 to retain said strip in position on the slider. The strip is also formed with further projections 38 and 39 which assist in locating the rollers 29 and 30. Thus after the rollers have been dropped into their recesses 31 and 32 the retaining strip 33 is clipped into position and the rollers will thus be prevented from becoming detached from the slider 11. Said recesses 31 and 32 are open sided so that the rollers 29 and 30 project from the open sides of said recesses and thus project also into said slide-way 12 so as to be adapted to engage the fixed contacts 13, 14, 15 and 16 as the slider is moved relative to the housing part 10.

Claims

1. A switch comprising a housing having fixed contact means and a movable switch operating member which carries movable contact means wherein said fixed contact means includes at least one fixed contact formed from a strip of resilient electrically conductive material which is bent to form a generally closed configuration in which one end of the strip overlaps or lies closely adjacent to the other end of the strip, at least one of said ends being divided by one or more slots or slits which extend in directions generally parallel to the length of the strip and part-way along the length thereof to form a plurality of contact portions, the arrangement being that one lead can be connected to the fixed contact by inserting its end between one of said contact portions formed at one end of said strip and the adjacent part of the other end of the strip so as to be frictionally retained therebetween, whereas another lead of the same or different diameter from the firstmentioned lead can be connected to the fixed contact by inserting its end between another of said contact portions formed at one end of said strip and the adjacent part of the other end of the strip so as to be frictionally retained therebetween.

2. A switch as claimed in Claim 1 wherein said one end of the resilient electrically conductive strip is divided into two contact portions by means of one slit or slot and wherein the adjacent end of said strip is formed with a centrally disposed longitudinally projecting tongue which overlies at least part of said slit or slot.

3. A switch as claimed in either of the preceding claims wherein the operating mem ber of the switch comprises a slider which is longitudinally slidable in a slide-way formed in the housing of the switch, the movable contact means carried by said slider comprising one or more electrically conductive rollers.

4. A switch as claimed in Claim 3 wherein the or each roller is located in an open-sided recess formed in the slider so that the periphery of the roller projects from the open sides of its co-acting recess so as to be adapted to engage the fixed contact means provided in the housing as the slider is moved in the housing.

5. A switch as claimed in Claim 4 wherein the or each roller is retained in its co-acting recess by means of a capping strip which extends across the outer end of the roller.

6. A switch as claimed in Claim 5 wherein said capping strip is retained in position by means of inter-engaging projections and recesses formed in the slider and capping strip.

7. A switch substantially as hereinbefore described with reference to and as shown in the accompanying drawings.