Contact Assembly For Sliding Switches

Abstract

A contact assembly for a sliding switch having a contact bridge made in one piece and disposed in a chamber in a slide for cooperation with relatively fixed contacts spaced one from another in the direction of sliding movement of the contact bridge. The contact bridge having a substantially rectangular frame with the short sides formed integrally with inwardly directed convex contact arms and the long sides provided midway with recesses engaged by projections of the chamber walls. The middle regions of the long sides rest on ledges provided in and at opposite sides of the chamber.

Description

DESCRIPTION

This invention relates to contact assemblies for sliding switches, such as are used, for example, in radio and television sets.

An object of the present invention is to devise contact assembly having a contact bridge which, in manufacture, need be subjected only to a comparatively slight deformation by bending in the operative spring regions.

Another object is to devise a contact assembly having a contact bridge which has a very small spacing of the contact points for the two countercontacts, and relatively long spring regions.

According to the invention, there is provided a contact assembly for a sliding switch having a contact bridge made in one piece and disposed in a chamber in a slide for cooperation with relatively fixed contacts spaced one from another in the direction of sliding movement of the contact bridge, in which said contact bridge comprises a substantially rectangular frame having shorter sides formed integrally with inwardly directed convex contact arms arranged to cooperate with the relatively fixed contacts, in which said frame has long sides being provided midway with recesses engaged by projections of the chamber walls, and in which middle regions of the frame's long sides rest on ledges provided in and at opposite sides of the chamber.

With this configuration of the contact bridge, the effective spring path always extends from the point of support over one-half of the long side of the frame, in this operative position there occurring not only bending stress but also torsional stress over half the transverse side to the arched contact arm, the latter also contributing to the creation of contact pressure by elastic bending deformation. In this, the contact arms only being one-sidedly arched, while the essential spring regions, the long sides, undergo no deformation or very little deformation only during the manufacturing of the bridge, so that the original spring properties of the semimanufactured product remain unchanged.

Due to the completely closed frame, the contact bridge represents a compact, robust spring element which is easily mountable, even in very small executions.

The supporting points of the countercontacts lie very closely adjacent each other on the inwardly directed contact arms, so that the countercontacts may also be moved towards each other to the necessary minimum spacing required by voltage safety. By this, it is not only possible to achieve a short stroke, but also even in switches having several changeover contacts, a small overall depth.

Since the frame's longitudinal sides are only supported in the middle, this contact bridge has the properties of a rocker, by which also the contact pressures are balanced even in the event of nonuniform position of the counter contact.

In the assembled condition of the slide, the contact bridge is held in the chamber by bearing resiliently on the counter contacts. So as the to prevent the contact bridges also when the slide is fitted with the contact bridges from falling out of the chamber, it is proposed in a further development of the contact assembly to deform plastically on their end faces the projections engaging the recesses in the longitudinal sides of the frame. This deformation takes, however, only place to such an extent that a certain rocking movement of the contact bridge on its supporting ledges or banks is retained.

For obtaining the lowest and most constant contact resistance possible, the contact bridge may be made, as known per se, of spring band with a noble metal coating, preferably a silver coating.

So as to accommodate the largest possible number of switchover contacts in a switch of small overall lengths, two contact systems may be accommodated in mirror-image fashion on opposite sides of the slide, whereby there is obtained at the same time a two-sided, mutually balancing resilient guide of the slide in the stationary part of the switch.

For a better understanding of the invention reference will now be had, by way of example, to the accompanying drawings, which represent, on an enlarged scale, one embodiment of the invention and in which:

FIG. 1 shows part of a switching slide for a slide switch, the switch having one fitted and one unfitted chamber;

FIG. 2 represents a section through the slide along the central plane of a chamber;

FIGS. 3 and 4 show a plan view and a side elevation respectively, of the contact bridge, and

FIG. 5 shows diagrammatically the contact assembly in part of a slide switch.

Referring to the drawings, the slide 1, part of which is shown in FIG. 1, is made of a plastics material and is provided on both sides of its longitudinal axis with shallow chambers 2. Both the longitudinal sidewalls of the chambers have in the middle thereof semicylindrical supporting banks or ledges 3, 3', above which there are provided likewise semicylindrical projections 4, 4' of somewhat smaller diameter.

FIGS. 3 and 4 show, on a greatly enlarged scale, a contact bridge for the sliding switch, this contact bridge being made of silver-plated bronze strip or band. It comprises a rectangular frame with outer rounded-off corners, the longitudinal sides 5, 5' of which being formed at the middle with semicircular recesses 6, 6'. Contact arms 8, 8', directed inwardly towards the middle of the frame and arched towards the same side, are cut into the transverse sides 7, 7' of the frame. The contact bridge is so dimensioned that its outer contour fits with a certain clearance into the rectangular chamber 2 of slide 1. The contact bridge is inserted into the chamber so that the middle regions of the longitudinal sides 5, 5' rest on the ledges or banks 3, 3' of chamber 2 and that the projections 4, 4' engage the recesses 6, 6' with a tight fit. Upon insertion of the bridge, the end faces of the projections 4, 4' are slightly thermoplastically deformed so as to prevent the bridge from falling off the supporting ledges 3, 3' by its own weight, while retaining such mobility that it can perform a certain tilting or rocking movement on the said banks.

The mode of operation of this contact assembly is recognizable from the diagrammatic representation of FIG. 5. This figure shows part of a slide switch having a slide according to FIG. 1 fitted with contact bridges inserted into a chamberlike switch casing, the latter having its walls provided with stationary counter contacts 10a, 10b, 10e, 10'a, 10'b, 10'c. Upon insertion of the slide, the prearched contact arms 8, 8', initially projecting beyond the profile of the slide, are pressed back in resiliently deforming the contact bridge, so that the contact arms to rest with pretension on the counter contacts. Through resilient deformation of the contact bridge, there occurs both bending and torsion of the longitudinal sides 5, 5' and bending of the contact arms 8, 8'. The contact pressure between arms 8, 8' is substantially balanced or equalized by the rockerlike mounting of the bridge on the supporting banks, even in the case of deviating position of the counter contacts.

When the slide is moved in the direction of the arrow by one contact distance (switch stroke), the connections between contacts 10a and 10b, and 10'a and 10'b are opened and connection is established between contacts 10b and 10c and 10'b, and 10'c, so that the function of a double-pole changeover switch is provided. On account of the construction in accordance with the invention, the spacing of the fixed contacts and the switch stroke may be kept very small, which in an actually constructed assembly amounts to but 2.5 mm.

For the construction of range-change switches for radio and television sets, the individual slide switches may conventionally be provided with several contact assemblies arranged one after the other, and several such switches may be combined by known means to form a switch unit for mutual release of the individual slides.

While one particular embodiment of the invention has been shown and e described, it will, of course, be understood that various modifications may be made without departing from the principles of the invention. The appended claims are, therefore, intended to cover any such modifications within the true spirit and scope of the invention.

Claims

I claim:

1. In a contact assembly for a slide switch: a casing, a slide slidingly arranged in said casing, said slide providing a chamber; fixed contacts spaced from one another in the direction of sliding movement of said slide and attached to said casing; a contact bridge located in said chamber and adapted to cooperate with said fixed contacts; said contact bridge comprising a substantially rectangular frame; longitudinal sides and shorter sides on said frame; said shorter sides formed integrally with inwardly directed arched contact arms adapted to cooperate with said fixed contacts; said longitudinal sides of said frame provided midway along their length with recesses engaged by projections of said chamber walls; midregions of said longitudinal sides resting on ledges formed on opposite sides of said chamber.

2. In a contact assembly according to claim 1, comprising end faces of the projections, said projections engaging said recesses of the longitudinal sides being plastically deformed upon insertion of said contact bridge.

3. In a contact assembly according to claim 1 characterized in that said contact bridge is provided on one side with a noble metal coating.

4. In a contact assembly according to claim 1 characterized in that said contact bridge is provided on one side with a coating of silver.

5. In a contact assembly according to claim 1, comprising a plurality of contact bridges which are arranged in mirror-image fashion on opposite sides of said slide.