GB2247995A - A lockable electric plug - Google Patents

Abstract

An electrical plug, incorporating a switch 40 and a locking bolt 39 both operated by a lock 7, is connected to the cable of an electrical appliance as an alternative to the standard, unswitched plug. This ensures that only authorised users of the appliance, possessing the appropriate key, can operate the appliance, disable the appliance or disassemble the plug. A visual indication 25 of this may be provided as an option. An electric plug incorporates a switch (40) operated by a key (33). The key operates a lock (7) to move a bolt (39) that cams a microswitch (40) operator and engages a restriction of a locking screw at (2) holding the three-part plug casing (4) together. The latter prevents disassembly of the plug when the switch is disabled. A visual indicator (25) shows the state of the switch. <IMAGE>

Description

A LOCKABLE ELECTRICAL PLUG This invention relates to an electrical plug which may be electrically disabled by means of a lockable security switch.

An electrical appliance is generally conneciecl to the electricity supply via a flexll,le cable on the end of whict.

is a plug which is inserted into an outlet. The electricity supply may be switched on or off in various ways e.g. at tht outlet, by a switch in the flexible cable or at the appliance itself. For security reasons, some industrial equipment computers and other appliances have a security device incorporated into them to restrict their use to holders of a key to a lockable electrical switch. However. most electrical equipment available does not have this facility.

One embodiment of the present invention will permit any electrical appliance to be switched on or off by keyholders only. with no modification to the actual appliance itself.

It comprises an appropriate electrical plug (to mate with the electrical outlet available) incorporating a lockable electric switch in the electricity supply, located in a electrical sense, between the plug and the appliance. This switch may only be operated, either on or off. b means of the insertion of a key into a keyhole in the plug and hence the plug and connected appliance may be enabled or disabled as required. An electrical switch operated b a lockable mechanism is refered to as a keyswitch. A sliding bolt mechanism is included in the plug to prevent both its unauthorised removal from the cable plus incorrect changing of the fuse rating (if fitted), when the plug is disabled.

The plug is hence useless, when locked,parted from its key.

There are many kinds of electrical plug, the type being dependant on use ; for example, consumer plugs to BSl3(33. or three phase, or round pin, or bayonet etc, The kind of plug and its intended use will dictate which of the connections t the appliance will need to have the keyswitch(s) incorporated, e.g. single pole; or double pole, etc.

A specific embodiment of the invention will now be described by way of example. This illustrates the invention applied to a consumer plug to BS 1363. detailed in the accompany drawings, in which FIGURE 1 shows the electrical circuit diagram.

FIGURES 2 and 3 show exploded side and top views respectively and give some internal details.

FIGURES 4 and 5 show to views of the plug cover.

FIGURES 6 and 7 show to views of the switch body.

FIGURES 8 and 9 show to views of the pin bod.

FIGURE 10 shows details of the sliding bolt mechanism GLOSSARY OF TERMS RELATING TO FIGURES 1 TO 10 1. BYPASS CONNECTOR 2.CLEARANCE HOLE IN SWITCH BODY 3.CAVITY FOR EARTH PIN AND WIRE 4.SWITCH BODY 5.CAVITY FOR NEUTRAL PIN SCREW AND WIRE 6.SPRUNG NEUTRAL CONNECTION FOR INDICATOR 7. LOCK 8. INDICATOR WINDOW 9.SCREW 10.EARTH PIN 11.NEUTRAL PIN 12.LIVE PIN 13.CABLE GRIP 14.LIVE PIN SOCKET 15.LIVE WIRE CONNECTION SOCKET 16.CLEARANCE HOLE IN PIN BODY 17.EARTH WIRE CONNECTION 18.PIN BODY 19.NEUTRAL WIRE CONNECTION 20.CABLE 21.COVER 22.THREADED HOLE 23.FUSE 24.FUSE HOLDER 25.OPTO ELECTRIC INDICATOR 26.CABLE GRIP SCREWS 27.BYPASS CONNECTOR WIRE PIN 28.LIVE BYPASS CONNECTOR PIN 2.9.INTERNAL WIRE CONNECTIONS 30.LIVE WIRE TO APPLIANCE 31.NEUTRAL WIRE TO APPLIANCE 32.EARTH WIRE TO APPLIANCE 33.SECURITY KEY 34.PIN BODE LOCATION POLES 35.SWITCH BODY LOCATION LUGS 36. SWITCH BODY LOCATION HOLES 37.COVER LOCATION LUGS 38.CAVITY FOR BYPASS CONNECTOR 39.SLIDING BOLT 40.MICROSWITCH Figure 1 shows symbolically one embodiment of this invention i.e. the incorporation. functionally, of a keyswitch (lock 7 and microswitch 40) operated by a key 33 between the LIVE pin 12 of the plug and the connection 15 of the LIVE wire 30 of the appliance. The fuse 23 is located. in an electrical sense, between the LIVE pin 12 and the microswitch 40 The opto-electric indicator 25 is shown between the appliance end of the microswitch 40 and the NEUTRAL connection which will give a visual indication of the electrical state of the keyswitch. Two plug connections 28 and 27 make contact with two sockets 14 and 15 to permit ease of assembly and the possibility of creating a layout which can plug directly onto a contact pin and cable grip assembly of an existing manufacturer.

Figure 2 gives an exploded side view showing .for clarit.

only some of the internal features. The plug may be considered as being composed of three structures i.e. the pin body 18! the switch bod 4, and the cover 21. These are held together by a screw 9 passing through clearance holes 2 and 16 in the pin body 18 and switch body 4 respectively. which screws into a threaded hole 22 in the cover 21.

The switch bod has an internal dividing wall such that. for safety considerations. only those metal parts requireu to mate up with the electrical connections in the pin body Ib are exposed.

Figures 3 gives the exploded top view showing the keyhole of the keyswitch 7 and the transparent tinted window 8 in the cover 21.

Figures 4 and 5 give two views of the cover 21 showing the threaded hole 22 and the transparent window 8. This cover 21 has two location lugs 37 which locate into corresponding holes 36 in the switch body 4, to ensure correct alignment when assembled.

Figures 6 and 7 give two views of the switch bod 4. View A shows the bypass connector 1 which has two electrical contacts 27 and 28 which plug into the corresponding sockets in the pin body 18 namely the LIVE wire connection socket 15 and the LIVE pin socket 14 respectively. A spring contact G is positioned above the position of the NEUTRAL pin 19 in the pin body 18 and is connected to one terminal of the opto-electric indicator 25. The other terminal is connected.

in an electrical sense to the appliance side of the microswitch. Internal insulating walls form areas 3, 5 and 38 to prevent stray pieces of wire causing short circuits.

The two lugs 35 locate into corresponding holes 34 in the pin body 18 to ensure correct alignment. View B shows the eyswitch (lock 7 and microswitch 40 - in the "on" position).

indicator 25, the fuseholder 24 and the fuse 23 and the five corresponding interconnecting conductors 29. The keyswitch comprises a lock with a central section which rotates when the key is turned. This has an offset peg on the end which engages in a slot on the sliding bolt 39 hich can then slid across the switch body 4 in the direction of the arrows along a groove, to guide its movement. When this sliding bolt 39 is moved to the left in figure 7 a protrubrance on it engages with the spring arm of the microswitch 40 and depresses the button, hence turning the plug ON. Reversing the key moves the bolt to the right which releases the microswitch button and turns the plug OFF. The forked part of the bolt now engages in the narrow part of the screw 9, preventing its removal.

It can be seen that the bypass connector wire pin 27. the LIVE bypass connector pin 28 and the sprung NEUTRAL connection for the indicator 25 all pass through the dividing wall of the switch body 4. The fuss is the same as would normally be found in a conventional BS1363 plug (ie to BS1362), and an be replaced try unscrewing the screw 9 ant removing the cover 21.

Figures 8 and 9 give two views of the pin body 18. It is similar in layout to a standard 13amp consumer plug except that the sockets 14 and 15 which would normally hold a fuse to BS1362 are captive in the pin body 18 and their position accurately maintained to ensure that connector 1 in the switch bod 4 makes an adequate electrical connection. The top of the ECTL pin 19 is of a sufficient size and in the correct position for the sprung NEUTRAL connection of the indicator to make contact. This connection carries negligible current and can be a maintained with slight pressure. The connector 1 and the sockets 15 anc 14 must be rated at 13amp - the materials and dimensions of the standard BS1362 fuse connection are suitable for this use, The cable is secured by means of the cable grip 13 which is tightened b means of the screws 26.

Figure 10 shows the sliding bolt 39 in its ON and OFF positions and shows a side view of the screw 9.

Claims (7)

1. An electrical plug which permits an electrical appliance connected to it to be disabled and enabled by means of a security key operated electrical switch incorporated within the plug.

2. An electrical plug as claimed in claim 1 with a mechanism within it to prevent removal of the fixings holding the plug together when it is in the disabled state.

3. An electrical plug as claimed in claim 1 and claim 2 incorporating an opto-electric visual indicator to indicate whether the appliance is disabled or enabled.

4. An electrical plug as claimed in claim 1 and claim 2 incorporating a non-electrical visual indicator to indicate whether the appliance is disabled or enabled.

5. An electrical plug as claimed in claim 1 and claim 2 but having an external cable separating the pin body (including fuse if relevent) from the switch body.

6. An electrical plug as claimed in claim 5 and claim 3; the visual indication being adjacent to the keyswitch.

7. An electrical plug as claimed in claim 5 and claim 4; the visual indication being adjacent to the keyswitch.