GB2266015A - Switched electrical socket outlet - Google Patents

Abstract

A switched electrical socket outlet (1) is operable between OFF, ON and TRIPPED states; resetting can be carried out merely by removing and reinserting the plug. The socket includes a conventional shutter (4, 13) operable by the earth pin (10). A carrier (20) supports a movable switch contact (60) and moves either with or relative to the shutter via a pair of rollers (34, 35) supported by trip mechanism (30). The shutter and carrier are biassed to their OFF positions, while the trip (30) is biassed to either untripped or tripped position. In the latter case, an electrical signal is provided on plug insertion, to withdraw the trip to the figure 4A position. A solenoid (50) or bimetal trips mechanism (30). Uses: portable residual current device. <IMAGE>

Description

ELECTRICAL SOCKET OUTLET The present invention relates to an electrical socket outlet which is designed to receive a plug.

It is frequently necessary or desirable to provide a reset function on particular socket outlets such as those provided for portable residual current devices (RCDs).

Portable RCDs incorporate a switch mechanism designed to operate to interrupt the electrical supply sufficiently quickly to prevent injury when there is an electrical fault. A portable RCD may be plugged into a mains socket outlet and a plug then plugged into the RCD so that it interposes between the mains and plug. Should the RCD operate it is clearly desirable to ensure that the fault has been cleared before reconnecting the circuit. Many such devices have been arranged so that the user has to remove the plug before resetting. This is achieved by locating a reset button so that the plug covers the button or by interlocking the reset button with a socket shutter so that the user is prevented from operating the reset button until the plug has been removed.

Manual resetting is not limited to RCD but is applicable to a thermal overload protection device. Such a device operates by using the heating effect of current to heat a bi-metallic strip which above a certain temperature causes electrical contacts to open and interrupt the electrical supply. A latch is provided to retain the contacts in the open condition until the device is reset by pressing a reset button.

An object of the present invention is to provide a suitable mechanism for an electrical socket outlet which is operable by insertion or withdrawal of a plug without the need to touch the socket.

Accordingly an electrical socket outlet according to the present invention comprises a switch mechanism operable between a first and second state by the insertion or withdrawal of a corresponding plug, the mechanism including an electrical switch characterised by operating means to cause the mechanism to operate from the second to a third state.

Preferably the switch mechanism is operable to return from the third to the first state on withdrawal of the plug.

The mechanism may further include a member movable by the plug on withdrawal of the plug to move between the third to the first state, the member being preferably a shutter so that the mechanism in the first state is in a shuttered condition and in the second and third states the mechanism is in an unshuttered condition, the switch being 'off' in the first and third states. The operating means can be caused to operate to trip either by a change of electrical supply to the outlet or by an external signal, that is the mechanism may be reset after tripping by removing the plug.

This disconnects the appliance connected to the plug and encourages the user to check the appliance for a fault.

When the user rectifies the problem the socket outlet will provide a normal supply to the plug and appliance by merely plugging in the plug into the socket.

The switch mechanism can be operated by a solenoid operated by a residual current device or other fault detecting means or remote signalling means. A simple switch mechanism can be provided in which a shutter and an operating part slide relative to each other when tripped and which is compact so as to be usable in the confined space of the socket. In this embodiment the operating means causes movement of a pair of mutually engaging rollers between a recess in the part and a recess in the shutter so that the part can shift relative the shutter. A spring between the shutter and part causes the recesses to move relatively apart in the plane of relative movement so that the shutter and part are disengaged due to disengagement of the rollers.

An embodiment of the invention will now be described with reference to the accompanying drawings in which: Figure 1 shows a part cross-sectional elevation of a plug plugged into an electrical socket according to the invention with the mechanism in a second state; Figure 2 is a plan view of the mechanism of Figure 1 seen from Y-Y in Figure 3; Figure 3 is a side view of the mechanism of Figure 2 seen from Z in Figure 2; Figures 4A, B and C are cross-sections of the mechanism of Figure 2 in a first, second and third state respectively; Figures 5A, B and C are side views taken from the same direction and in the same respective states as Figures 4A, B and C, and Figures 6A, B and C are enlarged cross-sectional views of Figures 4A and 4C with an intermediate view not quite corresponding with Figure 4B.

In Figure 1 can be seen a socket outlet at 1 with a three pin plug 2 shown in broken lines. The outlet has a switch mechanism generally shown at 3 comprising a shutter 4 to cover the line and neutral pin holes 6 and 7 respectively of the socket and to be opened by an earth pin 10 which enters the socket outlet through pin hole 11 to contact the slanted edge 13 of the shutter. The shutter is arranged to slide in the normal way away from the earth pin hole in guides (not shown) against the pressure of a coil spring 15. Insertion or removal of the plug causes the shutter to move away or toward the earth pin hole 11.

Slidably mounted so as to be movable in the same direction as the shutter is a part 20 and movable in a direction D perpendicular to the slidable movement of the shutter 4 and part 20 is an operating member 30 forming part of an operating means which carries a pair of mutually contacting rollers 32 and 33 which have axles 34 and 35 slidable in the slidable direction of the shutter in a pair of slots 36. The shutter has a recess 18 and part 20 an opposed recess 22 both of which can contain rollers 32 and 33 at the same time.

A switch is formed from a moving contact 60 mounted on part 20 and a fixed contact 62 which contacts line pin 9. An operating means 50 is provided which may be a solenoid operated by a residual current device or other means caused to operate by a change of electrical supply to the outlet or by an external signal of a remote signalling means.

The operating means presses on the contact carrier part 20 in direction D (Figure 5B) to trip the mechanism as will be described.

The shutter 4 provides location and guidance for the contact carrier part 20, location of the rollers 32 and 33 which when engaged with the contact carrier part drive the contact carrier part and therefore close contacts 60 and 62. The shutter also provides the normal function of a linear shutter.

The contact carrier part 20 provides an interface between the shutter and the moving contact 60.

The rollers 32 and 33 are locatable in the shutter recess 18 and when in the opposed recess 22 provide the link which enables both the shutter and contact carrier part 20 to move together.

The roller carrier or operating member 30 captivates the rollers and provides the means to move the rollers in and out of the recess in the contact carrier part 20.

Shutter spring 15 returns the shutter to its rest position as shown in Figure 4A.

A contact carrier spring 24 moves the carrier part 20 into the 'off' position when the mechanism is tripped.

Operation When the mechanism is in the latched position as shown in Figure 3 the shutter and carrier part 20 are linked together by the rollers which are positively located in the recess 22 in the carrier part by a spring force acting on the roller carrier operating member 30 in direction A (see Figure 5A). When the rollers are in this position they are trapped between the driving faces of the recesses in both the shutter and carrier part. In this position (see Figure 6A) the shutter and carrier part will act as one.

To switch the mechanism 'ON' a plug 2 has to be inserted into the socket. As the plug is inserted the mechanism is driven in the direction of arrow B (see Figure 5A) by earth pin 10. When the plug has been fully inserted the contacts 60, 62 close which applies a force in the direction C (see Figure 5B). The mechanism is now in the 'ON' position of Figures 4B and 5B.

To switch the mechanism OFF the plug has to be removed from the socket. This enables the shutter to return to the rest position under the force of the shutter spring 15.

When the mechanism is in the 'ON' position and a fault is detected the mechanism is tripped (delatched). This is achieved by a force applied to the roller carrier 20 in the direction of 'arrow D' (Figure 5B). A preferred method of applying this force would be via solenoid 50 but other operating means can be provided as have been described.

As the roller carrier moves in the direction of 'arrow D' (Figure 5B) the rollers start to roll out of the recess 22 in the contact carrier 20. When the rollers have moved the distance 'X' (Figure 6A) the contact carrier starts to move in the direction of 'arrow E' (Figure 4B) due to the force in the direction of 'arrow C' (Figure 5B). As the contact carrier continues in the direction of 'arrow E' it forces the rollers completely out of the recess in the contact carrier and into the position in the shutter 4 shown in Figure 6C. As the contact force diminishes the momentum of the contact carrier continues due to the spring force supplied by the contact carrier spring 24. The contact carrier continues until it reaches the tripped position (Figure 4C).

To reset the mechanism the plug has to be removed from the socket. As the plug is removed the shutter returns to the 'OFF' position due to the shutter spring. When the shutter reaches the 'OFF' position the rollers relocate in the recess in the contact carrier under the force in the direction of 'arrow A' (Figure 5A) and this resets (relatches) the mechanism.

The switch mechanism can be operated by a solenoid operated by a residual current device, or other fault detecting means, or remote signalling means. The switch mechanism could also be operated by any device which is capable of exerting the small force and deflection necessary to operate the mechanism. It is also possible to configure the mechanism such that the mechanism is normally held by spring force in the third state and requires an electrical signal to retract the tripping device, and allow the mechanism to operate between the first and second states.

A bi-metal device may replace the solenoid 50 to provide the operating force of the operating means. This operating force could equally well be provided by a piezoelectric device.

In an alternative mode of operation where the tripping arrangement instead of being at rest in the untripped state as already described, this arrangement could be at rest in the tripped state. This would be valuable since it would provide a fail safe mechanism for safety critical devices such as Residual Current Devices. Whatever the actual operating means was it would be sprung to the tripped state and would rely on an electrical signal to ensure that when the plug was inserted the mechanism operated from the first state to the second state. If for instance there was a power cut then there would not be any electrical signal to operate the trip mechanism, and when the plug was inserted the mechanism would remain in the third state, and the electrical contacts would not close.

Claims (9)

1. An electrical socket outlet comprising a switch mechanism operable between a first and second state by the insertion or withdrawal of a plug the mechanism including an electrical switch characterised by operating means to cause the mechanism to operate from the second to a third state.

2. An outlet as claimed in claim 1 wherein the switch mechanism is operable to return from the third to the first state of withdrawal of the plug.

3. An outlet as claimed in claims 1 or 2 wherein the mechanism includes a member movable by the plug on insertion.

4. An outlet as claimed in claim 3 wherein the mechanism includes a shutter movable by at least one pin on plug insertion.

5. An outlet as claimed in any one of claims 1 to 4 wherein the mechanism includes a part which is arranged to be tripped by the operating means when the mechanism is in the second state.

6. An outlet as claimed in any one of claims 1 to 5 wherein the operating means is caused to operate by a change of electrical supply to the outlet.

7. An outlet as claimed in any one of claims 1 to 5 wherein the operating means is caused to operate by an external signal.

8. An outlet, as claimed in any one of claims 1 to 5, wherein the operating means is normally energised by an electrical signal to permit the insertion and withdrawal of a plug to operate the mechanism between the first and the second state, and where removal of the electrical signal to the operating means is arranged to cause the mechanism to operate from the second state or the first state to the third state and remain in that state until the electrical signal is restored to the operating means.

9. An electrical socket outlet substantially as described with reference to the accompanying drawings.