GB2234402A

GB2234402A - Safety plugs

Info

Publication number: GB2234402A
Application number: GB8916760A
Authority: GB
Inventors: Geoffrey William Fletcher
Original assignee: Hillman Newby Ltd
Current assignee: Hillman Newby Ltd
Priority date: 1989-07-21
Filing date: 1989-07-21
Publication date: 1991-01-30
Also published as: GB8916760D0

Abstract

A masking device (10) in the form of a dummy plug for covering an electrical socket (1) of the kind having a spring biased sliding shutter, has at least one pin (12) provided with a rearwardly facing latching face (15) which latches behind the shutter to hold the device in the socket. A separate key must be inserted into a bore (17) to displace the shutter in order to remove the device. A working plug with the same latching feature is also disclosed and can be useful when equipment, such as a computer, is not to be accidently unplugged. <IMAGE>

Description

SAFETY PLUGS This invention relates to safety plugs and masking devices designed to prevent the introduction of foreign objects into electrical sockets. In a second aspect the invention also relates to an electrical plug which is releasably locked in position in a socket.

Electrical sockets in homes and elsewhere can be dangerous to small children who may try to push their fingers or small objects into the sockets. It is known to blank off a standard three-pin socket when it is not in use by means of a plastics masking plate having three pins complementary to the socket. The pins of the masking plate are pushed into the holes of the socket in the manner of a plug and are frictionally held there. The plate has only a small surface area which can be gripped manually to remove the plate from the socket. The combination of a high frictional grip of the pins of the plate in the socket and a small surface area for the user to grip ensures that only a relatively strong user can remove the masking plate from the socket. A child is not strong enough.

However, such masking devices which are difficult to pull out of sockets have the disadvantages that adults too may have difficulty in finding adequate strength or purchase to pull them out of a socket, and a child may be able to lever them out of a socket using a tool.

According to a first aspect the invention consists in a masking device having at least one pin adapted to be inserted into a pin-receiving hole of an electrical socket, the pin when inserted into the pin-receiving hole of the socket latching behind a component of the socket so as to resist removal of the device from the socket.

Thus the device is positively held to the socket and cannot be prized away from it.

Preferably the pin has a rearwardly facing latching face which in use latches ' behind said component of the socket.

The device may comprise a masking member adapted to extend over the live and neutral holes of an electrical socket, and a dummy earth pin extending away from the masking member. The dummy earth pin may be provided with the latching face.

Preferably the dummy earth pin comprises a forward portion defining the latching face and a recessed portion rearward of the latching face, a recess being formed in the recessed portion adjacent the latching face. The arrangement of the device is preferably such that, when used in conjunction with a socket having a resiliently biased sliding shutter adapted to obscure the holes of the socket, the forward portion of the dummy earth pin deflects the shutter away from the holes as the pin is inserted into the earth hole and the recess allows the shutter to move upwards once the forward portion of the pin has moved beyond the shutter, the latching face co-operating with the shutter to retain the device to the socket.

The device preferably has three dummy pins. The dummy live or neutral pins, or both, may also be provided with recesses for latching engagement with the shutter. The arrangement may be such that whilst the dummy earth pin allows upward movement of the shutter, actual latching is effected by another pin: the earth pin need not do the latching.

Preferably the device has associated release means adapted to release the latching engagement to allow withdrawal of the device. The release means is preferably in the form of a release key provided as a separate element to the device. When the release means is employed little strength is needed to remove the device from the socket.

When the device has a masking member that member may have a through-bore to allow the introduction of a release key into the socket through the masking member. The release key preferably deflects the shutter of the socket out of the way of the latching face to allow the masking device and key to be removed from the socket together.

According to a second aspect the invention consists in a plug which is adapted to be releasably locked in position in a socket.

Preferably the plug has a pin which has a rearwardly facing latching face adapted to engage in use behind a spring biased shutter of the socket to retain the plug in the socket. Release means may be provided to release the plug. The release means is preferably a separate release key.

Figures 1 and 2 schematically show a conventional three-pin electrical socket having a spring-loaded sliding shutter; Figure 3 shows a masking device in accordance with the invention; Figure 4 shows the masking device of Figure 3 in its position of use in the socket of Figures 1 and 2; Figure 5 shows a key for use in the removal of the masking device from the socket of Figure 4; Figure 6 shows another masking device; and Figure 7 shows a self-locking plug in accordance with the second aspect of the invention.

A standard electrical socket 1 is shown in Figures 1 and 2 and comprises three pin-receiving holes 2, 3 and 4, a spring-biased sliding shutter 5, and an on/off switch. The shutter 5 obstructs the holes 3 and 4 until the introduction of the earth pin of a plug into hole 2. The leading end of the earth pin contacts a ramp 6 on the shutter as the plug is pushed into the socket, deflecting the shutter 5 downwards to allow the pins'of the plug to enter their respective holes 2, 3, or 4.

A masking device 10 is shown in Figures 3 and 4 and comprises a generally triangular, rectangular or other suitable plug-shaped masking plate 11 from one face of which extends a dummy earth pin 12, and two dummy live and neutral pegs 13. The dummy earth pin 12 is of the same general length and size as a real earth pin of a plug. The dummy pegs 12' are not as long as real live and neutral pins of a plug, being of just smaller length than the depth of their receiving holes 3 and 4 in socket 1.

The pin 12 has a forward portion 13 having a chamfered leading face to assist its introduction into hole 2, and a rearwardly facing latching face 15 which part defines a recess 16 in a recessed portion 14 of the pin. A rectangular section bore 17 extends completely through the plate 11 and is aligned with the recess 16 in a manner which will be described later.

The operation of the masking device will be described with reference to Figure 4. As the dummy earth pin 12 is inserted into hole 2 it contacts the ramp 6 and deflects the shutter 5 downwards as a conventional earth pin would do. The forward portion 13 enters the hole 2 and moves past the shutter 5 which bears against the underside of the forward portion. When the pin 12 is pushed fully into the hole 2, so that the plate 11 closely overlies the socket 1 and the pegs 13 are received in the holes 3 and 4, the latching face 15 has travelled beyond the rear face of the shutter. This allows the shutter to move upwards, behind the forward portion 13 and the latching face 15, and into the recess 16 to abut the underside of the recessed portion 14. Withdrawal of the pin 12, and hence removal of the device 3, is prevented by engagement of latching face 15 with ttlr shutter 5, latching the forward portion 13 behind the shutter 5.

The device is removed from the socket by inserting a key 20, shown in Figure 5, into the bore 17 and thence into recess 16. A forward portion 21 of the key has a cross section complementary to that of the bore 17 and deflects the ramp 6 downwards out of the way of the latching face 15 as the key is inserted into the device. In the preferred embodiment shown the forward portion 21 of the key is dimensioned so as to complement the recess 16. In its fully inserted position the key engages the latching face 15 and fills the recess 16, effectively completing the dummy earth pin 12 to give it the same overall shape as a conventional earth pin. The dummy earth pin 12 and the forward portion 21 of the key can then be withdrawn from the hole 2 together.

When the key 20 is used relatively little strength is needed to remove the device from the socket. This makes the device suitable for use by weaker people such as the aged.

A child cannot lever the device away from the socket since it is positively latched in the socket.

The masking device can be easily and cheaply moulded in plastics material such as nylon. The key may be made of plastics material or of metal.

Another masking device is shown in Figure 6 and comprises what is in effect a dummy conventional three-pin plug with modifications. The dummy earth pin, referenced as number 30, has a forward portion 31, recessed portion 32, and latching face 33 similar to those of the embodiment of Figures 3 and 4. A bore 34 is again provided complementary to the recess defined by the face 33 and recessed portion 32 and extending completely through the dummy plug. A key 35 is provided to release the dummy plug from a socket.

Each dummy live or neutral pin 36 is of the same general size and shape as a conventional live or neutral pin, but has an undercut recess 37 provided in it. In use the upper portions of the lower arms of the T-shaped shutter shown in Figure 1 engage in the recesses 37, in addition to the engagement of the upper end of the shutter in the recess in pin 30. Thus the dummy plug of Figure 6 is latched to the socket at three places. The plug may be integrally moulded in plastics material.

A self-locking plug 40 and associated removable key 41 is shown in Figure 7. The shape of the plug 40 is similar to that of the dummy plug masking device of Figure 6. However, the plug 40 is a real plug which actually makes electrical contacts with a socket 1.

Instead of an undercut recess 37, live and neutral pins 42 of plug 40 have a channel 43 extending around their circumference.

Channel 43 (or recess 37) may be formed by stripping off a layer of insulating material 44 which is provided in some conventional plugs extending up to a shoulder 45 of the live and neutral pins.

The plug 40 may be used in situations where it is desired not to unplug a particular plug, for example if a computer or facsimile machine has to be plugged in continuously. It can prevent absent minded staff from unplugging the machine by mistake, for example in order to vacuum clean the room. A further advantage of the plug is that children cannot remove it during play.

Claims

1. A masking device having at least one pin adapted to be inserted into a pin-receiving hole of an electrical socket, the pin when inserted into the pin-receiving hole of the socket latching behind a component of the socket so as to resist removal of the device from the socket.

2. A device according to claim 1 in which the pin has a rearwardly facing latching face which in use latches behind said component of the socket.

3. A device according to claim 1 or claim 2 which comprises a masking member adapted to extend in use over the live and neutral holes of an electrical socket, and a dummy earth pin extending away from the masking member, the dummy earth pin having a forward portion defining a rearwardly facing latching face and a recessed portion rearward of the latching face, a recess being formed in the recessed portion adjacent the latching face, the arrangement being such that, when used in conjunction with a socket having a resiliently biased sliding shutter adapted to obscure the holes of the socket, the forward portion deflects the shutter away from the holes as the dummy earth pin is inserted into the earth hole and the recess allows the shutter to return towards its obscuring position once the forward portion has moved beyond the shutter, the latching face co-operating with the shutter to retain the device to the socket.

4. A device according to any preceding claim in which release means is provided to release latching engagement of the device in the socket.

5. A device according to claim 4 as it depends from claim 3, in which the device has a through-bore extending through the masking member and aligned with the recess in the earth pin, and a release key is provided as a separate element associated with the device, the release key being adapted to deflect the shutter to allow the device and key to be removed together from the socket.

6. A plug adapted to be releasably locked in position in a socket.

7. A plug according to claim 6 which has a rearwardly facing latching face provided on a pin, the latching face being adapted to engage in use behind a resiliently biased shutter of a socket to retain the plug in the socket.

8. A plug according to claim 7 in which a release key is provided as a separate element, removal of the plug from the socket being possible when the release key is inserted in the plug.

9. A masking device substantially as described herein with reference to Figures 3 to 5 of the accompanying drawings.

10. A masking device substantially as described herein with reference to Figure 6 of the accompanying drawings.

11. A plug substantially as described herein with reference to Figure 7 of the accompanying drawings.

Amendments to the claims have been filed as follows 1. A masking device having at least one pin adapted to be inserted into a pin-receiving hole of an electrical socket, the pin when inserted into the pin-receiving hole of the socket latching behind a component of the socket so as to resist removal of the device from the socket.

6. A plug adapted to be releasably locked in position in a socket.

12. A masking device adapted for use with an electrical socket having a resiliently biased sliding shutter, the masking device having a pin which has a rearwardly facing latching face adapted to engage in use behind the resiliently biased shutter of the socket to retain the masking device in the socket.