GB2396489A

GB2396489A - Switched electric socket

Info

Publication number: GB2396489A
Application number: GB0326234A
Authority: GB
Inventors: Neville Robinson
Original assignee: Individual
Current assignee: Individual
Priority date: 2002-11-14
Filing date: 2003-11-11
Publication date: 2004-06-23
Also published as: GB0326234D0; GB0226552D0; IE20030847A1

Abstract

A plug socket comprising one or more pin sockets for receiving a respective pin of a plug and a switch operatable between an on state and an off state. A shutter 22 is biased to adopt a blocking state, in which the shutter wholly or partially occludes at least one of said pin sockets. A blocking member 24 is biased to adopt a blocking state in which the blocking member prevents the switch 18 being operated from the off state to the on state. Upon insertion of a plug into the socket, at least one of the pins engages with the shutter thereby actuating the shutter and the blocking member out of the respective blocking states. Hence, the switch cannot be turned on until a plug is inserted into the socket. In a preferred embodiment, if the switch is left on when the plug is removed, the blocking member engages with the switch as it returns to the blocking state thereby turning the switch off.

Description

ELECTRIC PLUG SOCKET

The present invention relates to electric plug sockets.

5 Conventional electrical sockets for multi-pin plugs comprise a respective pin socket for receiving respective pins of a plug. Such plug sockets are commonly provided with a switch which is operable between an on state and an off state, so as to permit 10 or prevent the flow of current to the pin sockets. If a plug is withdrawn from the socket while the switch is in the on state, the pin sockets remain live. This is a potentially hazardous situation which may result in the electrocution of anyone tampering with the live 15 socket.

It is known to provide plug sockets with a shutter located between a face plate of the socket, and the pin sockets themselves. The shutter is usually spring 20 biased to adopt a blocking state in which it occludes the pin sockets, and is moveable to a non-blocking state in which access to the pin sockets is permitted, said movement being effected by the insertion of the pins of the plug into the pin sockets. This may be 25 achieved by providing a wedge- or ramp-shaped portion of the shutter in register with one of the pin sockets so that when a pin is pushed into its socket, it engages with the shutter portion and actuates the shutter into the non-blocking state. However, despite 30 the provision of the shutter, the pin sockets still remain live upon removal of a plug from the plug socket

if the switch is not switched off. Moreover, the shutter can quite easily be bypassed, thereby providing access to live pin sockets.

5 Accordingly, the invention provides a plug socket comprising one or more pin sockets for receiving a respective pin of a plugs a switch operatable between an on state, in which the pin sockets are electrically connected to a power supply, and an off state in which 10 the pin sockets are electrically isolated from the power supply; a shutter biased to adopt a blocking state, in which the shutter wholly or partially occludes at least one of said pin sockets; and a blocking member associated with the shutter and biased 15 to adopt a blocking state in which the blocking member prevents the switch being operated from the off state to the on state, wherein, upon insertion of a plug into the socket, at least one of the pins engages with the shutter thereby actuating the shutter, and by 20 association the blocking member, out of the respective blocking states.

Hence, the switch cannot be switched from off to on until a plug is inserted into the socket.

In one embodiment, the blocking member is integrally formed with the shutter. In an alternative embodiment, the blocking member is separately formed from the shutter, the arrangement being such that the shutter, 30 upon movement out of the blocking state, engages with

the blocking member thereby actuating the blocking member out of the blocking state.

When the plug is removed from the socket, the shutter 5 returns to the blocking state under bias. The blocking member is also urged under bias to return to the blocking state but may be prevented from doing so if the switch has been left in the on state. Accordingly, in preferred embodiments, the blocking member is shaped 10 so that, should the switch be in the on state as the blocking member moves to the blocking state, the blocking member engages with the switch thereby actuating the switch into the off state.

15 Conveniently, this may be achieved by providing the blocking member with a bevelled, wedge-like, ramp-like or similarly shaped portion for engagement with the switch. 20 The shutter may be mounted between guides which cause the shutter to undergo substantially linear movement into and out of the blocking state. Alternatively, the shutter may be pivotably mounted on the plug socket.

25 The blocking member may be mounted between guides which cause the blocking member to undergo substantially linear movement into and out of the blocking state.

In a preferred embodiment, the plug socket includes a 30 face plate which carries the switch and which is shaped to define a respective aperture for each pin socket,

each aperture being in register with a respective pin socket so that a respective pin may be inserted through a respective aperture into a respective socket, and wherein the shutter is located between the face plate 5 and the socket pins. The shutter may conveniently be mounted on the face plate. The blocking member may conveniently be mounted on the face plate.

Further advantageous features of the invention will 10 become apparent to those ordinarily skilled in the art upon review of the following description of specific

embodiments and with reference to the accompanying drawings. 15 Figure 1 presents a perspective view of a plug and socket embodying the invention; Figure 2 presents a rear view of a face plate of the plug socket of Figure 1; Figure 3 presents a rear view of an alternative embodiment of a face plate of the plug socket of Figure 1; and 25 Figure 4 presents a rear view of a further alternative embodiment of a face plate of the plug socket of Figure 1. Referring now to Figure 1, there is shown a plug 30 socket, generally indicated as 10, and a corresponding plug 12 for insertion therein. The plug socket 10

includes a face plate 14 having three apertures 16 formed therein, behind which are located respective pin sockets (not shown). Each aperture 16 is substantially in register with a respective pin socket so that, in 5 use, a respective pin 20 of the plug 12 may be inserted through a respective aperture 16 into a respective pin socket. By way of illustration, the plug 12 is shown as having three pins 20 and the socket 10 has three corresponding pin sockets 16. It will be understood 10 that the invention may be used with plugs/sockets having any number of pins/pin sockets.

The plug socket 10 includes a switch 18 which is carried by the face plate 14 and is operable between an 15 off state, in which the pin sockets are electrically isolated from the electrical power supply (not shown), and an on state in which the pin sockets are electrically connected to the electrical power supply.

20 Referring now to Figure 2, there is shown a rear view of the face plate 14 (a front view of the face plate 14 being presented in Figure 1). A shutter 22, which is preferably formed from an electrical insulating material, is located adjacent the reverse face of the 25 face plate 14 and is movable between a blocking state (shown in solid outlined in Figure 2), in which it occludes the apertures 16, and a non-blocking state (shown in broken outline in Figure 2) in which the apertures 16 are unobscured by the shutter 22. When in 30 the blocking state, the shutter 22 is located between the apertures 16 and the respective pin sockets and so,

as well as occluding the apertures 16, the shutter also occludes the respective pin sockets. Hence, the shutter 22 prevents access to the pin sockets through the apertures 16. With the shutter 22 in the non 5 blocking state, the pin sockets can be accessed through the respective apertures 16.

Conveniently, the shutter 22 is slidable with respect to the face plate 14 in a plane substantially parallel 10 with the face plate 14. Preferably, the shutter 22 is slidably mounted to the face plate 14 between spaced-

apart opposed guides 26 which guide the (substantially linear) movement of the shutter 22 between the blocking and non-blocking states. The shutter 22 is resiliently 15 biased to adopt the blocking state by a spring (not shown) or other suitable biasing means.

A portion 28 of the shutter 22 which faces and is register with, or obscures, one (or more) of the 20 apertures 16 when the shutter 22 is in the blocking state, is bevelled, wedge-shaped or ramp-shaped so that, upon insertion of a pin 20 into the aperture 16, the pin 20 engages with the shutter portion 28 and the inward movement of the pin 20 forces the shutter 22 25 into the non-blocking state. In the illustrated embodiment, the shutter portion 28 is associated with the, in use, top aperture 16 as shown in Figure 2, although this need not necessarily be the case.

30 A blocking member is provided in the form of an arm 24 which, in the present embodiment, is integrally formed

with the shutter 22. The arm 24 is biased to adopt a blocking state (shown in solid outline in Figure 2) in which it is located behind the switch 18 so as to prevent the switch from being operated from the off 5 state to the on state. When the shutter 22 is in the blocking state, and the switch 18 is in the off state, the arm 24 adopts its blocking state. Because the shutter 22 and arm 24 are integrally formed, the biasing means, e.g. spring, which acts on the shutter 10 to urge it into the blocking state also acts on the arm 24 to urge it into its blocking state. When the plug 12 is inserted into the plug socket 10, thereby effecting displacement of the shutter 12 into its non-

blocking state, the arm 24 is also displaced into a 15 non-blocking state in which it does not interfere with the operation of the switch 18. Hence, the switch 18 cannot be switched from off to on until a plug 12 is inserted into the plug socket 12.

20 Commonly, the switch 18 is left in the on state whenever the plug 12 is removed from the socket 10.

Not only is this potentially hazardous, but it may also prevent the arm 24, and therefore the shutter 22, from reaching the blocking state. Accordingly, it is 25 preferred that the portion 30 of the arm 24 which, in the blocking state, obstructs the switch 18, is shaped so that, as the arm 24 moves from the non-blocking state into the blocking state and in so doing engages with the switch 18 when in its on state, the 30 interaction of the moving arm portion 30 with the switch 18 causes the switch to be actuated into its off

state. By way of example, the arm portion may be bevelled, ramp-shaped, wedge-shaped or similarly shaped for this purpose. The portion of the switch 18 which engages with the portion 30 of the arm 24 may 5 advantageously be shaped to facilitate this actuation.

Hence, when the plug 12 is removed from the socket 10, the shutter 22 adopts its blocking state under bias thereby blocking the apertures 16 as described above.

10 If the switch 18 is left on, the arm 24 actuates the switch into off state and adopts its blocking state in which the switch 18 may not be actuated to its on state. As a result, when there is no plug 12 in the plug socket 10, the switch 18 is ensured to be off and, 15 moreover, cannot be switched on until a plug is inserted into the socket. This means that when there is no plug 12 in the plug socket 10, the pin sockets are isolated from the electrical power supply.

20 Referring now to Figure 3, there is illustrated an alternative embodiment of the invention in which the face plate is generally indicated as 114. In this embodiment, like components have been accorded like reference numerals and, unless otherwise stated, 25 perform a like function to those described in relation to the embodiment of Figure 1. The shutter 122 and arm 124 are formed separately from one another, each being spring biased by a respective spring 132, 134 or other biasing means, to adopt their respective blocking 30 states.

The shutter 122 includes a lug 136 and the arm 124 includes a shoulder 138, the lug 136 and shoulder 138 being shaped and positioned for engagement with one and other. The arrangement is such that, as the shutter 5 122 is actuated from its blocking state to its non-

blocking state (e.g. when the plug 12 is inserted into the socket 10), the lug 136 engages with the shoulder 138 thereby causing the arm 124 to be actuated into the non-blocking state (shown in dashed outline in Figure 10 3). Hence, when the plug 12 is inserted into the plug socket 10, the arm 124 does not prevent the switch 118 from being actuated into the on state. When the plug 12 is removed from the plug socket 10 the shutter 122 returns to its blocking state under the bias of spring 15 132. The arm 124 is also urged to its blocking state under the action of spring 134. In embodiments where the arm 124 includes a ramp-shaped or similarly shaped portion 130, the arm 124 adopts its blocking state while simultaneously actuating the switch 118 into its 20 off state as described above (assuming that the user has not already turned the switch off). However, in alternative embodiments, the arm 124 may not include a ramp-shaped or similarly shaped portion 130 and is therefore unable to actuate the switch 118 from the on 25 state to the off state. In such embodiments, the arm 124 is prevented from adopting its blocking state if the switch 118 is left on after the plug 12 has been removed from the socket 10. The arm 124 can only adopt its blocking state whenever the switch 118 is turned 30 off.

Referring now to Figure 4, there is illustrated a further embodiment in which the face plate is generally indicated as 214. Again, in this embodiment, like components have been accorded like reference numerals 5 and, unless otherwise stated, perform a like function to those described in relation to the embodiments of Figure 1 and 2. In this embodiment, the shutter 222 is pivotable with respect to the face plate 214 about a pivot point 40. The shutter 222 may be pivoted between 10 a blocking state (shown in solid outline) in which it occludes or blocks at least one of the apertures 216 and a non-blocking state in which it does not obscure the apertures 216. In the illustrated embodiment, the shutter 222 blocks the two, in use, lower apertures 15 216. The shutter 222 includes a ramp portion 228, or similarly shaped portion, which, when the shutter 222 is in its blocking state, is in register with one or both of the lower apertures 216. The arrangement is such that when a plug 12 is inserted into the socket 20 10, one or more pins of the plug 12 engages with the ramp portion 228 thereby effecting pivoting displacement of the shutter 222 into its non-blocking state (shown in dashed outline in Figure 4). The shutter 222 is preferably biased to adopt the blocking 25 state by, for example, a coil spring (not shown) coupled between the pivot point 40 and the shutter 222.

The arm 224 is formed separately from the shutter 222 and is actuatable between a blocking state (shown in 30 solid outline) and a non-blocking state (shown in dashed outline). When in the blocking state, a portion

230 of the arm 224 is located behind the switch 218 and prevents it from being switched on. In the non-

blocking state, the portion 230 is clear of the switch 218 and allows it to be switched on. The arm 224 is 5 resiliently, or spring, biased to adopt the blocking state by a spring (not shown) or other biasing means.

When there is no plug 12 inserted in the socket 10, the arm 222 adopts the blocking state under spring bias and 10 the shutter 222 adopts its blocking state. Upon insertion of a plug 12, the shutter 222 rotates about pivot point 40. The arrangement is such that, as the shutter 222 rotates into its non-blocking state, it engages with the arm 224 thereby actuating the arm 224 15 into its non-blocking state. To this end, the shutter 222 conveniently includes a lug 236 shaped and positioned for engagement with a shoulder 238 provided on the arm 224. In this embodiment, it will be seen that rotational movement of the shutter 222 is 20 translated into a linear displacement of the arm 224.

When the plug 12 is removed from the socket, the shutter 222 reverts to its blocking state under bias.

As a result, the shutter 222 no longer holds the arm 25 224 in the nonblocking state. If the switch 218 is in the off position, then the arm 224 is free to adopt its blocking state under bias. If the switch 218 has been left in the on state, then the switch 218 may prevent the arm 222 from adopting the blocking state. However, 30 in preferred embodiments, the portion 230 of the arm 224 is bevelled, ramp-shaped, wedge-shaped or similarly

shaped, so that, upon engagement with the switch 218 when in the on state, the portion 230 causes the switch 218 to be actuated into the off state under the force exerted by its bias. Hence, the arm 224 is able to 5 adopt the blocking state.

The present invention is not limited to the embodiments described herein, which may be amended or modified without departing from the scope of the present 10 invention.

Claims

Claims:

1. A plug socket comprising one or more pin sockets for receiving a respective pin of a plugs a switch 5 operatable between an on state, in which the pin sockets are electrically connected to a power supply, and an off state in which the pin sockets are electrically isolated from the power supply; a shutter biased to adopt a blocking state, in which the shutter 10 wholly or partially occludes at least one of said pin sockets; and a blocking member associated with the shutter and biased to adopt a blocking state in which the blocking member prevents the switch being operated from the off state to the on state, wherein, upon 15 insertion of a plug into the socket, at least one of the pins engages with the shutter thereby actuating the shutter, and by association the blocking member, out of the respective blocking states.

20

2. A plug socket as claimed in Claim 1, wherein the blocking member is integrally formed with the shutter.

3. A plug socket as claimed in Claim 1, wherein the blocking member is separately formed from the shutter, 25 the arrangement being such that the shutter, upon movement out of the blocking state, engages with the blocking member thereby actuating the blocking member out of the blocking state.

30

4. A plug socket as claimed in any of Claims 1 to 3, wherein the blocking member is shaped so that, should

the switch be in the on state as the blocking member moves to the blocking state, the blocking member engages with the switch thereby actuating the switch into the off state.

5. A plug socket as claimed in Claim 4, wherein the blocking member includes a bevelled portion for engagement with the switch.

10

6. A plug socket as claimed in any preceding claim, wherein the shutter is mounted between guides which cause the shutter to undergo substantially linear movement into and out of the blocking state.

15

7. A plug socket as claimed in any of claims 1 to 5, wherein the shutter is pivotably mounted on the plug socket.

8. A plug socket as claimed in any preceding claim, 20 wherein the blocking member is mounted between guides which cause the blocking member to undergo substantially linear movement into and out of the blocking state.

25

9. A plug socket as claimed in any preceding claim, further including a face plate which carries the switch and which is shaped to define a respective aperture for each pin socket, each aperture being in register with a respective pin socket so that a respective pin may be 30 inserted through a respective aperture into a

respective socket, wherein the shutter is located between the face plate and the socket pins.

10. A plug socket as claimed in Claim 9, wherein said 5 shutter is mounted on the face plate.

11. A plug socket as claimed in Claim 9 or Claim 10, wherein said blocking member is mounted on the face plate.

12. A plug socket substantially as hereinbefore described with reference to Figure 2 of the drawings.

13. A plug socket substantially as hereinbefore 15 described with reference to Figure 3 of the drawings.

14. A plug socket substantially as hereinbefore described with reference to Figure 4 of the drawings.