GB2183939A - Electrical contact-making device - Google Patents

Abstract

An insulating moulding 1 carries a number of conductive inserts 2 each with a threaded bore 4 for the reception of the threaded shank 5 of a terminal formed with an enlarged head 6. Each insert is in the form of a bushing having an axial projection 3 at its lower end which passes through a mounting board 8 where it is held in position by a spring clip 9 to secure the whole assembly. A conductor plate 10 extends over the top of the moulding 1, down the left hand side and through the board 8 to form an output terminal 12. This plate has openings 14 in register with corresponding openings 15 in the moulding 1 and also with the threaded bores 4. The terminal 5 can be inserted in any of the openings and initially makes contact only with the respective insert 2. When screwed down to the position illustrated, the head 6 engages the plate 10 and establishes an electrical circuit between that plate and the respective insert, i.e. between the selected input terminal 3 and the output terminal 4. <IMAGE>

Description

SPECIFICATION Electrical contact-making device This invention relates to electrical contactmaking devices or switches, and is concerned with a simple construction capable of carrying relatively high currents and suitable for use on passive loudspeaker cross-over, for example.

According to the invention, such a device, which will be referred to as a switch for convenience, comprises an insulating body having an opening giving access to a threaded bore formed in a conductive insert in the body, a conductive member surrounding the opening and a terminal with an enlarged head and a threaded shank fitting the threaded bore in the insert.

When the terminal is removed, the insert and the conductive member are separated by the insulating material of the body of the switch and there is no circuit between them.

When the terminal is screwed into position, however, it first makes contact with the insert and when it is screwed fully home, its enlarged head comes into contact with the conductive member and thus establishes an electric circuit between them. The circuit is broken again either by complete removal of the terminal or by unscrewing it sufficiently for its head to break the contact with the conductive member. The conductive member is conveniently in the form of a contact plate fitted to the surface of the insulating body and having a tag for connection in an electric circuit and the insert may have a similar connection tag.

The same principle can be used for a multipole selector switch which, in accordance with the invention, comprises an insulating body having a number of openings each giving access to a respective threaded bore formed in a respective conductive insert in the insulating body, a conductive plate secured to the outside of the insulating body and formed with openings corresponding to those in the body and a terminal with an enlarged head capable of being screwed into the threaded bore in any one of the inserts to establish a connection between that insert and the conductive plate.

A number of separate inputs may be connected to the various inserts and the output may be selected by screwing the terminal into the bore in the insert connected to the required input.

The or each insert may be in the form of a bushing having an axial projection of reduced diameter at the end remote from the bore which passes through and is secured in an insulating mounting board so as to constitute an input terminal. This holds the device firmly in position on the board and one or more connections can be made to the projections from the bushings while the output connection is made to the plate or other conductive member surrounding the or each opening.

An example of multi-pole selector switch in accordance with the invention is illustrated in the accompanying drawings, in which: Figure 1 is a sectional elevation; and Figure 2 is a diagrammatic electrical representation.

As shown in Fig. 1, an insulating body 1 in the form of a plastics moulding includes a number of conductive inserts 2 (five in the example illustrated). Each of the inserts is in the form of a bushing having an axial projection 3 at the lower end which forms a connection tag to which components can be soldered. Each insert 2 has a threaded bore 4 for the reception of the threaded shank of a terminal 5 formed with an enlarged head 6.

The projections 3 pass through an insulating mounting board 8 to which they are secured by spring ciips 9 so as to hold the whole assembly firmly in position on the board 8.

A metal contact plate 10 extends along the top of the body 1 and down the ends, passing through the mounting board 8 to form connection tags 12 for an output circuit. The plate 10 is formed with openings 14 in register with each threaded bore 4, these openings being somewhat larger than the shank of the terminal 5, and each forming a continuation of a similar opening 1 5 in the body 1.

When the terminal 5 is initially inserted in position, it makes contact only with the respective insert 2 and not with the plate 10 which is insulated from the insert by the thickness of the insulating body 1 between these two components. When, however, the terminal 5 is screwed fully into position, its enlarged head engages the plate 10 and thereby establishes an electrical circuit between the respective insert 2 and the plate 10, that is to say between the respective input terminal 3 and the output terminal 12.

As mentioned above, the drawing illustrates the inclusion of five inserts 2, but if only a single insert is used, the device functions as a single-pole on-off switch for making and breaking contact between an input terminal 3 and an output terminal 12. However, when a number of inserts is included as illustrated, the device functions as a multi-pole selector switch enabling any one of the inputs connected to the terminals 3 to be connected to the output 12, merely by inserting the terminal 5 in the appropriate opening and screwing it home into the position shown. This is illustrated in the diagrammatic view of Fig. 2, which illustrates the electrical equivalent with the input terminals 3 arranged in an arc of a circle and the terminal 5 illustrated as a wiper which can be moved into contact with any required input 3 to provide that same input at the output 12.

In order to comply with the requirements of a passive loudspeaker cross-over, the co-operating contact areas may be gold plated, i.e.

the interior of the bores 4 and the threaded shank 5, also the upper surface of the plate 10 and the underside of the enlarged head.

Claims (4)

1. An electrical contact-making device comprising an insulating body having an opening giving access to a threaded bore formed in a conductive insert in the body, a conductive member surrounding the opening and a terminal with an enlarged head and a threaded shank fitting the threaded bore in the insert.

2. A multi-pole selector switch comprising an insulating body having a number of openings each giving access to a respective threaded bore formed in a respective conductive insert in the insulating body, a conductive plate secured to the outside of the insulating body and formed with openings corresponding to those in the body and a terminal with an enlarged head capable of being screwed into the threaded bore in any one of the inserts to establish a connection between that insert and the conductive plate.

3. A contact-making device or switch according to claim 1 or claim 2, in which the or each insert is in the form of a bushing having an axial projection at the end remote from the bore which passes through and is secured in an insulating mounting board and constitutes an input terminal.

4. A multi-pole selector switch substantially as described and as illustrated with reference to the accompanying drawing.