GB2142186A - Improvements in or relating to switches - Google Patents

Abstract

A key-operated switch for connecting electrical contacts in selected pairs comprises a cam member 8 turnable about an axis. One or more first contact pins 14 carry contact springs 16 engageable with the cam member and cooperating with one or more second contact pins 15. The cam member 8 is so shaped and the second contact pins 15 are so disposed that upon turning the cam member the or a contact spring 16 is moved from a first position in which it is spaced from an associated second contact pin 15 into a second position in which it engages the associated second contact pin 15 thereby establishing an electrical connection between such first and second contact pins. <IMAGE>

Description

SPECIFICATION Improvements in or relating to switches This invention relates to switches and is concerned with switches in which electrical contacts can be connected in selected pairs. The invention is particularly concerned with sub-miniature switches which are controlled by a key-operated lock mechanism and which can be turned from 'off' to 'on' or to a variety of 'on' positions only by operation of the lock mechanism with the key. Such switches are of value for computers, data bases and security systems to which access is granted only to selected individuals by means of a key.

Broadly the present invention provides a switch comprising a cam member, means for rotating the cam member about an axis, at least one first contact pin spaced from the cam member, a contact spring attached to the or each first contact pin, each spring having at least one arm bent to engage against the cam member, and at least one second contact pin, the or each second contact pin being disposed and arranged such that the cam member can be rotated by said means from a first position in which the or a spring arm is spaced from its associated second contact pin to a second position in which the spring arm engages its associated second contact pin to establish an electrical connection between the first and second contact pins.

Preferably, the means for rotating the cam member is a key-operated lock acting on an index wheel to which the cam member is affixed. Preferably, the switch has several operating positions, and for a five position switch (one position being the 'off' position) two first contact pins would be provided each carrying a two-armed contact spring, the spring arms being selectively engageable under the action of the cam member with appropriate ones of four second contact pins.

In order to enable the invention to be more readily understood, reference will now be made to the accompanying drawings, which illustrate diagrammatically and by way of example an embodiment thereof, and in which: Figure 1 is a plan view, partly in section of a key-operated position switch, and Figure2 is a section along the line ll-ll in Figure 1.

Referring now to the drawings, there is shown, to an enlarged scale, a key-operated position switch.

The switch comprises a tubular outer body 1 of substantially square cross-section formed at one end with a flange 2 by which the switch may be engaged against, for example, a control panel with the body 1 disposed in a hole in the control panel. The body 1 is closed at one end by an end plate 3, the body 1 and end plate 3 being made of plastics material. A five-pin tumbler barrel lock is housed within the body 1 The lock has a face plate 4 and an index wheel 5 which is rotatable to selected positions by a key 6 (only part of which is shown). Such locks are known and the lock will thus not be described in further detail.

The index wheel 5 terminates in a square-section projection 7 on which a cylindrical cam member 8 is mounted. The cam member has a first cam recess 9 formed in its periphery at one end and extending exially for about half the axial length of the cam member. A second cam recess 10 is formed in the periphery of the cam at the other end and also extends axially for about half the axial length of the cam member. The cam recesses 9 and 10 are angularly spaced from one another by 90 .

The end plate 3 has a central boss 11 on which the cam member 8 is centred and mounts six contact pins, there being two first or main contact pins 14 and four second or subsidiary contact pins 15. A metallic contact spring 16 is affixed to each main contact pin 14, and each contact spring has two mirror-symmetrical arms. Each arm has a substantially straight portion 17, a portion 18 bent to extend substantially at right angles to the portion 17 and a terminal U-shaped portion 19 for engaging against the cam member 8 under the spring action of the contact spring. As shown in Figure 1,the contat springs 16 lie in different planes spaced apart along and normal to the axial length of the cam member so that one of the contact springs is associated with the cam recess 9 and the other with the cam recess 10.

In an 'off' position of the switch, all the U-shaped portions 19 of the contact springs engage against the outer periphery of the cam member 8 so that all the contact arms are spaced from their associated second contact pins 15. If now the key 6 is inserted and turned to a first 'on' position, the index wheel 5 is turned and turns the cam member 8 to a position in which one of the U-shaped portions 19 becomes associated with one of the cam recesses 9 and 10 whereupon the respective contact arm is free to move and is spring-urged into contact with an appropriate second contact pin 15 as shown in the bottom right-hand corner of Figure 2. Thereby a connection is established between the second contact pin 15 and the respective first contact pin 14 to complete an electric circuit external to the switch.

Continued indexing of the key will connect each of the pins 15 in turn to a contact pin 14to complete appropriate electric circuits.

It will be seen from Figure 2 that the squaresection projection 7 in offset relation to the outer body 1 by an angle which is conveniently 221/2 .

Because of this, the cam member 8 can be placed with one or other end face adjacent the index wheel 5 so as to provide two different switching programmes.

It will be appreciated that many modifications of the switch just described may be made. In particular, instead of the 5-pin tumbler barrel lock described, other locks may be used including disc tumbler locks, multi-pin locks and rotary pin tumbler locks.

Each lock is arranged to rotate an associated index wheel which may be chosen in dependence upon the lock. In one embodiment of the present switch, the four way index wheel 5 is replaced by an eight-way index wheel, which together with the feature of offsetting the square-section projection 7 by 221/2", provides a switch with increased versatility and a wide range of use.

Furthermore, the number and arrangement of the cam recesses may be selected in accordance with a desired switching programme. Thus, for example, the cam member may be extended in its axial direction and may be formed with a plurality of axially adjacent but angularly displaced cam recesses, and there may be a contact spring 16 associated with each such recess. The contact spring 16 is shown as being made of circular section spring wire but it will be appreciated that it may be made of strip material if the switch is to be designed for a higher rating.

In the switch shown in the drawings, each pin 15 is disposed in a space bounded by the spring portions 17 and 18 and the periphery of the cam member 8 so that when the portion 19 is urged into a cam recess the portion 17 will contact the pin 15. However, it will be appreciated that the cam member 8 could be formed with a cam projection and in this case it would be necessary to dispose the pins 15 on the other side of the contact arm so that as the portion 19 was urged outwardly by the cam projection, the contact arm would also move outwardly to engage the pin 15.

Claims (7)

1. A switch, comprising a cam member, means for turning the cam member about an axis, at least one first contact pin spaced from the cam member, a contact spring attached to the or each first contact pin, the or each spring having at least one arm bent to engage against the cam member, and at least one second contact pin, the cam member being so shaped and the or each second contact pin being disposed and arranged such that, upon turning the cam member, the or a spring arm is moved from a first position in which it is spaced from an associated second contact pin into a second position in which it engages said associated second contact pin, thereby to establish an electrical connection between said first and second contact pins.

2. A switch as claimed in claim 1, wherein the meansforturning the cam member is a keyoperated lock arranged to turn an index wheel to which the cam member is fixed.

3. A switch as claimed in claim 1 or 2, wherein the switch has two first contact pins each carrying a two-armed contact spring, and wherein each first contact pin is associated with two second contact pins, the arrangement being such that each arm of each contact spring is selectively engageable with an appropriate associated second contact pin.

4. A switch as claimed in claim 3, wherein the cam member is a cylindrical member with a plurality of axially adjacent but angularly displaced cam portions, and wherein a contact spring is associated with each cam portion.

5. A switch as claimed in claim 4, wherein the cam portions are cam recesses.

6. A switch as claimed in any one of claims 2 to 5, wherein the switch comprises a tubular outer body of substantially square cross-section and the index wheel terminates in a square-section projection on which the cam member is mounted and wherein the square-section projection is angularly offset in relation to the outer body, whereby the cam member can be placed with one or other end face against the index wheel so as to provide different switching programmes.

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