US3591748A

US3591748A - Electric switch

Info

Publication number: US3591748A
Application number: US806453A
Authority: US
Inventors: Brian Astbury Holden
Original assignee: Burgess Micro Switch Co Ltd
Current assignee: Johnson Electric International UK Ltd
Priority date: 1968-03-28
Filing date: 1969-03-12
Publication date: 1971-07-06
Anticipated expiration: 1988-07-06
Also published as: GB1253039A

Abstract

A switch is constructed with inner and outer members that support the contact elements of the switch and that sandwich between them a rubber gasket having apertures that form totally enclosed spaces in which the contact elements are brought into engagement when an operating force is applied to compress the gasket, beyond an initial prestressed state, by a Bowden cable on which the switch is mounted.

Description

United States Patent inventor Brian Astbury Holden [56] References Cited Washington, England UNITED STATES PATENTS f i' 22 1969 2,337,809 12/1943 Gaynor ..20o 1s3.22 ux gf 1: 3,315,050 4/1967 Miller.... 200/86 X Assignee Burgess Micro switch p y Limited 3,435,165 3/1969 Lombard 200/ 161 X Gateshead, Durham County, England Primary ExaminerRobert K. Schaefer Priority Mar. 28, 1968 Assistant ExaminerH. J. Hohauser Great Britain Attorney-Jacobs & Jacobs 15,023/68 figgT gi F ABSTRACT: A switch is constructed with inner and outer rawmg members that support the contact elements of the switch and U.S. Cl 200/161, that sandwich between them a rubber gasket having apertures 200/153, 200/86 that form totally enclosed spaces in which the contact ele- Int. Cl 1101b 17/08 ments are brought into engagement when an operating force is Field of Search 200/86, applied to compress the gasket, beyond an initial prestressed 161, 153.14, 61.19, 151 state, by a Bowden cable on which the switch is mounted.

1 I l [Z 5; fiV/WA/M II) I 76 4Z 56 j j x 55 ELECTRIC SWITCH This invention relates to an electric switch. In one form of the switch that is the subject of the invention the operation of the switch is actuable by means of a Bowden cable and may be employed in a brake light circuit for the type of brake which is itself operated by the cable, though the invention is by no means limited to this particular application.

An object of the invention is to provide a robust switch construction that is able to offer a greater resistance to corrosion and wear that commonly employed metal coil or leaf spring constructions.

A switch according to the invention comprises two switch members each bearing at least one contact element or surface and mounted to move from an off position (where the contact elements or surfaces supported on the two switch members are separated) to an on position (where the said elements or surfaces are in contact), resilient means of rubbery material being compressed between the two switch member to act as a return spring biasing the members to the off position, the said resilient means being shaped in a way which allows the contact elements or surfaces on the switch members to make contact when the switch is moved to its on position against the bias of the resilient means.

In a particularly advantageous arrangement of a switch according to the invention, the resilient means is in the form of a gasket that surrounds and protects the area between the contact elements or surfaces from damp penetration. In this way the biasing member is able also to perform a secondary function that adds further to corrosion and wear-resistance when the switch is to be employed in relatively exposed situations, such as the brake mechanism of a motorcycle. In a preferred arrangement, where one of the members of the switch carries a plurality of contact elements, these may be located in discrete holes so that each such element is separately surrounded by the gasket material.

The resilient rubbery material of the gasket may by any suitable natural or synthetic rubber, but is is obviously neces-' sary to relate its thickness and physical characteristics so that it fulfills the dual function of biasing the switch members outwardly and enabling these to be brought into contacting position.

One form of switch according to the present invention'will now be described with reference to the accompanying drawing wherein:

FIGS. 1 and 2 are axial sections through the switch in mutually perpendicular planes; and

FIG. 3 is a perspective view of the rubber gasket of the switch of FIGS. 1 and 2.

In the specific form of the invention shown in the drawing the switch comprises an outer member of substantially cylindrical cross section, a concentric cylindrical inner member 12, and an intermediate gasket l4. The inner and outer members are molded in plastics material and the intermediate gasket is of rubber.

The outer member 10 has a tapering frustoconical end 24 in which is molded a cylindrical recess 26. The other end of the outer member 10 has a larger recess or socket 28 of circular cross section. The

recesses

26 and 28 are joined by an axial bore 34 which is of a size to allow the inner wire of a Bowden cable to pass freely therethrough, whilst the recess 26 is large enough to take the sheath of the Bowden cable. A shoulder 27 is defined by the bore 34 and the recess 26. Two diametrically opposed rectangular channels 36 form apertures joining the outer surface of the member 10 and the recess 26 and ter- .minate with shoulders 37.

The inner member 12 is an easy sliding fit within the cylindrical recess 28, and has at its outer end a circular recess 40, this being of the same diameter as the recess 26 and passing part way through the member 12. From the bottom of the recess 40 a circular bore 42 of the same diameter as the bore 34 continues through the member 12, leaving a shoulder 44 between the bore 42 and the recess 40. Molded integrally with the member 12 on diametrically opposite sides thereof are ears 46 which define wedge-shaped projection beyond the main cylindrical face of the member. Secured to the member 12 when it is molded are two metal terminal bars 50 which have narrower inner portions 51 with bent down ends that splay away slightly from a rectangular section projection 49, at the inner end of the member and wider terminal tabs 53 that project from the outer end of the member 12.

The rubber sealing gasket or washer 14, which is made of rubber having a Shore hardness of about 30, fits into the bottom end of the recess 28. The gasket 14 is provided with sector-shaped holes 54 located so as to bev opposite the turned over ends 52 of the terminal bars 50 when the inner member 12 is in position, a recess 55 in which can seat the projection 49 of the member l2 and a central aperture 41 slightly larger than the

bores

34, 42. The unstressed thickness of the gasket is some 7.5 mm., of which some 4 mm. is occupied by the recess this being of the same axial length as the projection 49. Lugs 57 project from opposite concave regions 59 at the periphery of the gasket.

In order to assemble the switch, a flat metal ring 32 is first inserted into the outer member 10 to be followed by the gasket, the lugs 57 of which are received in the channels 36, and the inner member 12 is then forced into the recess 28 in a position in which the ears 46 are aligned with the channels 36 of the outer member 10. Resilient deformation of the members occurs until the ears reach the channels 36 where they spring out and are engaged by the shoulders 37 thus preventing the removal of the inner member from the outer one. During this action of forcing the member 12 into the member 10, the far end of the inner member 12 deforms the rubber gasket thus pressing it between the parts 10 and l2 and the ears 46 are thereby urged against the shoulders 37.

The Figures show the switch in position in a Bowden cable. It can be seen that sheath 60 of the cable has been separated to leave a length of bare wire 56 running centrally through the switch, the ends of the sheath thereafter having been pushed together to make contact with the shoulders 27 and 44 respectively.

If the Bowden cable is one which is used for the brake of a .motor cycle, application of the brake causes a compressive force along the sheath of the cable which is transmitted to the

parts

10 and 12 through the shoulders 27 and 44. This forces the two parts together against the resilience of the gasket 14 and allows the turned over ends 52 of the contact terminals 50 to make contact with the metal ring 32 through the holes 54 in the rubber gasket, thus providing electrical contact between the two terminals 50. It can readily be seen that, if the terminals 50 are connected into the electrical wiring system of a brake light, then the brake light will go on every time the brake lever is operated.

It is thought that the dimensions will normally be such as to give a preload figure of approximately 8 lbs., that is to say, this will be the outward pressure exerted by. the rubber washer against the

parts

10 and 12. This allows the sheath of the Bowden cable to be fitted with a compressive force of at least this figure without any fear of operation of the brake light. The normal braking tension in the cable 56, and the opposed compression in the sheath 54, which will increase the gasket load to 20 lbs., say, is quite sufficient to operate the switch The gasket 14, as perhaps best seen in FIG. 3, surrounds the area of the metal contact surfaces, i.e. the ring 32 and the ends 52 of the terminals and protects these from damp, since it is always under compression.

A feature of the particular form of gasket shown in the drawings is that it is able to offer different resistance rates to compression, depending upon the degree of deformation that has already taken place. Thus, initially the material surrounding the recess 55 and concave regions 59, where the transverse cross-sectional area of material is relatively small compresses readily under a relatively small axial load. After this stage, an increase in axial force will give a smaller degree of compression as the resistance to deformation is effectively that offered by the larger cross-sectional area of material below the recess and concave regions. The gasket therefore operates as if there were two separate resilient members present having different spring rates.

It will be appreciated that the switch may be made inmany different designs and if the outer part is of conductive metal there may, in some applications, he no necessity for a metal conductor such as the ring 32.

The invention is by no means confined to use in connection with Bowden wire, Its value is not only that it can be used in applications where a preloading of the two members is called for, but in many other cases as well, the rubber gasket which is under compression forming a moistureproof seal between the electrical contact surfaces within the switch as well as acting as a return spring for the separation of these contacts when the pressure is removed. Thus, to take a further example of the application of the invention, it can readily be applied to a footoperated switch with useful applications especially in exposed conditions.

I claim:

1. A switch comprising, in combination, two switch mem bers, a plurality of contact elements thereon, at least one contact element supported on one switch member and a plurality of contact elements supported on the other said member, the said switch members relatively displaceable between an off position where the contact elements or surface of the respective members are separated and an on position where the said elements or surfaces are in contact, a gasket of rubbery material disposed between the two switch members to surround and protect the area between the contact elements from damp penetration, said gasket compressed between the switch members to act as a return spring biassing the members to the off position, holes in the gasket to receive said contact elements so that each element is separately sealed by the gasket material, the shape of the gasket conformed to allow the con tact elements of the respective switch members to make contact when the switch is moved to its on position against the spring bias of the gasket.

2. A switch according to claim 1 which includes a bridging contact element which is supported on said one switch member to bear against one face of the gasket and wherein said plurality of contact elements project through said holesto engage said bridging contact element when the switch is in the on position.

3. A switch comprising, in combination, two switch members disposed one within the other, an outer switch member comprising a recessed socket and an inner switch member which is slidable therein, contact elements located on each switch member whereby the two switch members are relatively displaceable between an off position where the contact elements of the two respective switch members are separated and an on position where the said elements are in contact, resilient gasket means of rubbery material disposed at the inner end of the recessed socket between the two switch members, assembly elements provided on the inner and outer switch members, said elements registrable with each other to engage when the members are assembled so as to hold the inner switch member in the socket and wherein the resilient means is compressed to act as a return spring biassing the members to the off position, said resilient means shaped to allow the contact elements of the respective switch members to make contact when the switch is moved to its on position against the bias of the resilient means.

4. A switch, comprising in combination, two switch members disposed one within the other, an outer switch member comprising a recessed socket and an inner switch member which is slidable therein, a plurality of contact elements on the switches and wherein at least one contact element is supported on each switch member, the said members relatively displaceable between an off position where the contact elements of the switches are separated and an on position where the said elements are in contact, resilient means of a rubbery material disposed at the inner end of the socket between the two switch members and said resilient means compressed thereby to act as a return spring biassing the members to the off position, apertures in the two switch members extending axially of the recess and being mutually aligned, a Bowden cable engaged with the said switch members at said apertures whereby the application of an operating force to the cable causes said relative movement of the members to compress the rubbery resilient means against its bias and to bring the two switch members to the on position.

5. A switch according to claim 4 wherein the resilient means is a gasket that surrounds and protects the area between the switch contact elements from damp penetration.

6. A switch according to claim 3 wherein the resilient means is a gasket that surrounds and protects the switch contact elements from damp penetration.

7. A switch according to claim 3 wherein a plurality of contact elements are supported on at least one of the two switch members and which includes discrete holes in the gasket to receive respective ones of the said plurality of contact elements so that each contact element is completely surrounded by gasket material.

8. A switch according to claim 3 including a bridging contact element supported on one of the switch members to bear against one face of the gasket, spaced apertures located in the gasket through which apertures correspondingly spaced contact elements supported on the other of the switch members projects to engage the bridging element when the switch is in the on position.

9. A switch according to claim 1 wherein the switch members are disposed one within the other, the switch comprising an outer member comprising a socket recess and an inner member, the inner member slidable within the outer member and a resilient gasket means disposed at the inner end of the socket recess in the outer member.

10. A switch according to claim 1 which includes assembly elements provided on the inner and outer'switch members and said elements are registerable with each other to engage when the members are assembled so as to hold the inner member in the socket recess of the outer member with the resilient means compressed.

11. A switch according to claim 1 which includes apertures in the switch members, which apertures extend axially of the socket recess and are mutually aligned, a Bowden cable engaged with the switch members at said apertures whereby the application of an operating force to the cable causes relative movement of the switch members to compress the resilient means against its bias.

112. A switch according to claim 4 which includes annular shoulders located around each of the apertures directed away from each other, the outer sheath of the Bowden cable is interrupted to form spaced end faces bearing on said annular shoulders, the inner wire of the cable passing through the apertures to extend continuously between the switch members.

113. A switch according to claim I wherein the switch members are disposed one within the other, the outer switch member comprising a socket recess within which the inner switch member is slidable, a gasket disposed at the inner end of the socket recess and which includes respective apertures in the switch members extending axially of the socket recess and mutually aligned, a Bowden cable engaged with the switch members at said apertures whereby the application of an operating force to the cable causes relative movement of the switch members to compress the gasket against its bias, and a further discrete aperture provided in the gasket for the passage of the Bowden cable.

14. A switch according to claim 1 wherein the cross-sectional form of the resilient gasket means varies in the direction of compression whereby the said means offers an increased resistance to unit displacement against its bias after an initial deformation has been imposed upon it.

Claims

1. A switch comprising, in combination, two switch members, a plurality of contact elements thereon, at least one contact element supported on one switch member and a plurality of contact elements supported on the other said member, the said switch members relatively displaceable between an off position where the contact elements or surface of the respective members are separated and an on position where the said elements or surfaces are in contact, a gasket of rubbery material disposed between the two switch members to surround and protect the area between the contact elements from damp penetration, said gasket compressed between the switch members to act as a return spring biassing the members to the off position, holes in the gasket to receive said contact elements so that each element is separately sealed by the gasket material, the shape of the gasket conformed to allow the contact elements of the respective switch members to make contact when the switch is moved to its on position against the spring bias of the gasket.

2. A switch according to claim 1 which includes a bridging contact element which is supported on said one switch member to bear against one face of the gasket and wherein said plurality of contact elements project through said holes to engage said bridging contact element when the switch is in the on position.

10. A switch according to claim 1 which includes assembly elements provided on the inner and outer switch members and said elements are registerable with each other to engage when the members are assembled so as to hold the inner member in the socket recess of the outer member with the resilient means compressed.

12. A switch according to claim 4 which includes annular shoulders located around each of the apertures directed away from each other, the outer sheath of the Bowden cable is interrupted to form spaced end faces bearing on said annular shoulders, the inner wire of the cable passing through the apertures to extend continuously between the switch members.

13. A switch according to claim 1 wherein the switch members are disposed one within the other, the outer switch member comprising a socket recess within which the inner switch member is slidable, a gasket disposed at the inner end of the socket recess and which includes respective apertures in the switch members extending axially of the socket recess and mutually aligned, a Bowden cable engaged with the switch members at said apertures whereby the application of an operating force to the cable causes relative movement of the switch members to compress the gasket against its bias, and a further discrete aperture provided in the gasket for the passage of the Bowden cable.