GB2181899A - Electronic switches - Google Patents

Abstract

An electronic switch unit comprising a triac (2) with a terminal connected to a connector pin (5), is connected in series with a mechanical switch (8) so that when the mechanical switch is off no current can pass but when the mechanical switch is on, the electronic switch controls the passage of current. The connector pin (5) enters a conventional screw terminal socket (9) of the mechanical switch. For use with a row of mechanical switches several electronic switches with their associated connector pins are mounted on a common board (1), each connector pin entering a terminal socket of an associaed one of the mechanical switches. <IMAGE>

Description

SPECIFICATION Electronic switches This invention relates to electronic switches, that is to switches of the kind that operate without moving parts and that can be incorporated in an electric circuit and can control the flow of electricity in that circuit.

It is sometimes desirable for an electronic switch to be connected in series with a mechanical switch, that is an electrical switch operated by the relative movement of mechanical components, so that a user is free to complete or to break a circuit by actuating the mechanical switch only when the electronic switch is on. When the electronic switch is off the circuit cannot be completed merely by actuating the mechanical switch. It is proposed, for example, that such an arrangement could be employed in licensed premises to enable certain lamps in a bar to be switched on with the aid of manually-operable mechanical switches only during predetermined on periods, electronic switches in series with those mechanical switches being switched on only for the duration of those on periods. The electronic switches could be controlled by a timer.

An aim of the present invention is to provide an electronic switch unit capable of being readily and conveniently connected to other electrical equipment.

From a first aspect the present invention consists in an electronic switch unit comprising an electronic switch capable of controlling the flow of electricity between principal terminals of the switch, and a connector pin connected to one of those terminals and so shaped and disposed that it can be inserted into a terminal socket in a mechanical switch.

The switch unit preferably includes a board or other rigid mounting, the electronic switch being mounted on one side thereof and the connector pin projecting from the other side thereof.

From a second aspect the present invention consists in a switch assembly comprising in combination an electronic switch unit in accordance with the first aspect of the present invention and a mechanical switch having a terminal socket into which is inserted, or into which can be inserted, the connector pin on the unit.

The terminal socket of the mechanical switch may well be of a kind primarily intended to receive a bared end portion of an insulated wire, and is preferably of the conventional kind comprising an open-ended cylindrical metal tube provided with a transverse clamping screw. Although the clamping screw may have been provided by the manufacturer with the intention that it would be used to clamp a bared end portion of an insulated wire, the clamping screw may in fact be used for securing the connector pin in position in the terminal socket.

The switch may be provided with two or more terminal sockets, as is conventional in the case of a switch intended for connetion to two or more wires, so that in addition to the socket that receives the connector pin (and that will hereinafter be referred to as the primary socket) there is at least one additional socket. Where that is so the arrangement is preferably such that in a switch assembly in accordance with the present invention the presence of the electronic switch unit does not prevent access being obtained to the additional terminal socket or sockets.

Where an electronic switch unit in accordance with the present invention is attached to a mechanical switch in an existing installation, and where in the existing installation the primary terminal socket of that switch houses a bared end of an insulated wire, it is normally a simple matter to remove that bared end from the socket and replace it with the connector pin of the electronic switch unit.

The electronic switch unit may itself be provided with a supply terminal, this preferably comprising a socket such that the bared end of a wire formerly inserted into a terminal socket of a mechanical switch, and now occupied by the connector pin of the electronic switch unit, can be connected to the terminal socket of the electronic switch.

The electronic switch unit may comprise a plurality of electronic switches each having an associated connector pin connected to one of its principal terminals For convenience such switch units will hereinafter be referred to as multiple switch units, while switch units of the kind comprising a single electric switch and an associated connector pin will hereinafter be referred to as individual switch units. In use each connector pin of a multiple switch unit is inserted into a terminal socket of an associated mechanical switch. When an installation comprises a plurality of mechanical switches, and particularly when the switches are disposed in a regular pattern, such as a row or rectangular array, it is normally preferable to use one or more multiple switch units rather than a plurality of individual switch units.The use of multiple switch units simplifies both the manufacture and the installation of the unit or units. Many types of mechanical switches are of modular construction so that when they are mounted together in a row or array, corresponding parts of the switches are spaced apart at predetermined intervals. A multiple switch unit embodying the present invention can therefore be provided with a rigid body and with connector pins which are mutually parallel, spaced apart at the same uniform intervals, and projecting in the same direction.

In an alternative form of multiple switch unit, the connector pins are mounted on a flexible and/or extensible body so that variations in the spacing or angular disposition of the terminal sockets which they are to enter can be accommodated by flexure and/or extension of the body. In one particularly preferred arrangement each connector pin is mounted on an individual rigid support, and the rigid supports are interconnected by flexible and extensible link means, the body comprising the combined assembly of rigid supports and link means. In such a construction each electronic switch is preferably mounted on the same support as an associated connector pin.

In a multiple switch unit those principal terminals of the constituent electronic switches that are not connected to the connector pins are preferably connected to a common supply terminal on the unit, though in other constructions they are connected to individual supply terminals.

In any construction of multiple switch unit the flexible and/or extensible link means may incorporate one or more flexible electric conductors.

It will be appreciated that in addition to its principal terminals each electronic switch has at least one control terminal, the arrangement being such that in use the application of a control signal to the control terminal or control terminals causes the state of the switch to vary. In a multiple switch unit, control terminals of the constituent electronic switches are preferably connected to a multiple contact connector which can be engaged by a complementary connector. That arrangement can simplify the wiring of the switch unit during its installation.

Where the switch unit comprises a plurality of electronic switches and associated connector pins, each such switch with its associated connector pin is preferably mounted on an associated part of a common body. The arrangement may be such that during manufacture of the unit the body may be severed to permit the manufacture of a unit containing any desired number of electronic switches and associated connector pins.

A multiple switch unit preferably comprises no more than three electronic switches and associated connector pins, three being a particularly preferred number. In the relatively rare event of one of the electronic switches ceasing to function correctly it is likely to be the most economical course to discard the whole unit of which it forms a part and replace it with a fresh unit. Such procedure is likely to become uneconomic if the unit comprises more than three electronic switches.

Electronic switches such as triacs that are incorporated in switch units in accordance with the present invention often generate significant amounts of heat when in use. In a preferred form of unit the constituent electronic switch or each such electronic switch is preferably of the kind having a heat conductive portion which is electrically insulated from the operative part of the switch. The heat conductive portion can in use be brought into thermal contact with a heat sink, preferably a metallic heat sink, and that heat sink, though itself electrically conductive can- without ill effect be brought into contact with the heat conductive portions of two or more electronic switches.Where switch assemblies incorporating electronic switches of that kind form part of an installation having a common switch housing, the heat sink may be connected to a metallic part of the housing, which may be electrically earthed.

An embodiment of the present invention will now be described in more detail, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a side view of a multiple switch unit embodying the present invention, Figure 2 is a rear view of the switch unit shown in Figure 1, and Figure 3 is a rear view of a row of mechanical switches for use with a switch unit of the kind shown in Figures 1 to 3.

The switch unit shown in Figures 1 and 2 comprises a rectangular circuit board 1 on the rear face of which are mounted a plurality of electronic components including three electronic switches in the form of triacs 2. The components are embedded in a block 3 of potting compound of a conventional nature in order to protect them. Each triac 2 has a plurality of terminals which are somewhat diagrammaticaily indicated at 4. Of these terminals two are principal terminals and one is a control terminal. The arrangement is such that in use the triac can be used to control the flow of electricity between the principal terminals in response to the application of control signals to the control terminal.One of the principal terminals is connected to an associated connector pin 5 and the other is connected to a common supply terminal 6, the connection in each instance being either a direct connection or a connection by way of one or more other electronic components (not shown) in the block 3. Each of the three connector pins 5 projects from the other side of the board from that on which the triacs are mounted and have their axes normal to the board. The supply terminal 6 projects from the rear face of the block 3 and is in the form of a socket comprising a brass tube with a transverse clamping screw. Each triac 2 also has a control terminal. The control terminals of the three triacs are connected, directly or indirectly, to a multiple-contact blade connector 7 which projects from one end of the circuit board 1.

The circuit board 1 is preferably so designed and made that if desired it can be severed transversely so as to form the mounting for only two triacs or only one triac. This arrangement therefore simplifies the manufacture of a range of electronic switch units each of which units contains a different number of triacs. It would of course be possible to make units containing four or even more electronic switches, but as explained above such units may well be less economical in use than are those containing fewer electronic switches.

The electronic switch unit shown in Figures 1 and 2 is intended for use with a row of three mechanical switches 8, the backs of which are shown in Figure 3. Each of the switches is of conventional construction and has on its front face (not shown) a manuallyoperable rocker which can be manipulated by a user to make or break an electrical path between terminals 9 and 10 at the back of the switch. Each of the terminals is in the form of a socket comprising a metal tube with a transverse clamping screw. Hitherto it has been usual to insert the bared ends of insulated wires into such terminals. In accordance with the present invention, however, the three connector pins 5 are inserted into the three terminals 9 and secured in place by the transverse clamping screws of those terminals.It will be appreciated that the electronic switch unit, when attached to the switches, covers only an upper portion of the backs of the mechanical switches 8 so that ready access can still be obtained to the terminals 10.

The switch assembly thus formed may be used, for example, in controlling the supply of electricity to lamps in a bar in licensed premises. One line of a single-phase supply is connected to the supply terminal 6, while lines leading to the individual lamps are connected to the terminals 10. A timer (not shown) has an output connected to a flex having. a multiple contact connector complementary to connector 7 and engaged with connector 7. The timer operates in such a manner as to cause the triacs 2 to be conductive only during predetermined on periods. During those on periods a user can switch the lamps on and off at will with the aid of the switches 8 but during off periods the lamps cannot be switched on.

If the mechanical switches 8 form part of an existing installation it may well be possible for the multiple switch unit to be mounted in place behind the switches without significant alteration being made to the installation. In view of the relatively large amount of wiring usually present behind a row of array of mechanical switches there is often adequate space for one or more electronic switch units to be added without alteration being made. It may, however, be necessary or desirable to modify the installation for the mechanical switches so as to increase the space available for the electronic switch or switches.For example, where there is a switch housing comprising a frame in which the mechanical switches are mounted and a shallow box to which the frame is attached, the box being secured to a wall or other support, a spacer may be introduced between the frame and the box so as to increase the depth of the housing and thus to bring the mechanical switches a little further away from the wall or other support than before. For example the depth of the housing may be increased by about 25 mm.

In a modified construction (not illustrated) the triacs 2 are replaced by triacs of the kind having electrically insulated heat-sink tabs, which are arranged to project from the rear of the switch unit. The tabs are clamped to a metal bar which extends across the back of the unit and has end portions that extend beyond the unit and are bent rearwards, the end portions abutting a peripheral, metal part of the switch housing which is electrically earthed. In use, heat from the triacs is dispersed by way of the bar and the housing.

It will be understood that while the timer may generate control signals which are transmitted directly to the connector 7, the control signals may be transmitted indirectly.

In particular, signals from a remote timer may be transmitted through the mains supply lines and may be picked up and, if necessary, interpreted by a local receiver which generates appropriate control signals for the electronic switch unit or switch units. The receiver may be housed in the same housing as the switch assemblies.

The electronic switches in the switch units described above comprise triacs operative to switch a current on and off. In an alternative arrangement however an electronic switch may be such as to vary the value of the current and may, for example, serve as a dimmer.

Claims (12)

1. An electronic switch unit comprising an electronic switch capable of controlling the flow of electricity between principal terminals of the switch, and a connector pin connected to one of those terminals and so shaped and disposed that it can be inserted into a terminal socket in a mechanical switch.

2. An electronic switch according to claim 1 which includes a board or other rigid mounting, the electronic switch being mounted on one side thereof and the connector pin projecting from the other side thereof.

3. A switch assembly comprising in combination an electronic switch unit in accordance with either of claims 1 and 2 and a mechanical switch having a terminal socket into which is inserted, or into which can be inserted, the connector pin on the unit.

4. A switch assembly according to claim 3 in which the terminal socket of the mechanical switch comprises an open-ended cylindrical metal tube provided with a transverse clamping screw.

5. A switch assembly according to either of claims 3 and 4 in which the electronic switch is provided with a supply terminal constituted by a socket comprising an open-ended cylindrical metal tube provided with a transverse clamping screw.

6. A multiple switch unit comprising a plurality of electronic switch units, each in accordance with either of claims 1 and 2 and each having an associated connector pin connected to one of its principal terminals.

7. A multiple switch unit according to claim 6, which is provided with a rigid body and with connector pins which are mutually parallel, spaced apart at the same uniform intervals, and projecting in the same direction.

8. A multiple switch unit according to claim 6 in which the connector pins are mounted on a flexible and/or extensible body so that variations in the spacing or angular disposition of the terminal sockets which they are to enter can be accommodated by flexure and/or extension of the body.

9. A multiple switch unit according to any one of claims 6 to 8 in which each electronic switch has at least one control terminal, the arrangement being such that in use the application of a control signal to the control terminal or control terminals causes the state of the switch to vary, and the control terminals are connected to a multiple contact connector which can be engaged by a complementary connector.

10. A multiple switch unit according to any one of claims 6 to 9 comprising three (and no more than three) electronic switches and connector means.

11. A multiple switch unit substantially as hereinbefore described with reference to Figures 1 and 2 of the accompanying drawings.

12. A switch assembly comprising in combination a multiple switch unit in accordance with any one of claims 6 to 11 and a plurality of mechanical switches, each having a terminal socket into which is inserted, or into which can be inserted, an associated connector pin on the unit.