GB2150767A

GB2150767A - Locking plugs in sockets

Info

Publication number: GB2150767A
Application number: GB08331995A
Authority: GB
Inventors: Thomas Jago
Original assignee: Individual
Current assignee: Individual
Priority date: 1983-11-30
Filing date: 1983-11-30
Publication date: 1985-07-03
Also published as: GB8331995D0; GB2150767B

Abstract

A plug 10 is locked in a socket (not shown) by means of the end 14 of pin 13 being turned via a spindle 21 with a slotted head 22. <IMAGE>

Description

SPECIFICATION Electrical plug connector This invention relates to electrical plug connectors of the type having protruding conductor pins for insertion into correspondingly-positioned sockets of a socket outlet.

The invention is particularly although not exclusively applicable to the well-known three-pin fused plug connector having two live pins of elongate rectangular cross-section and a slightly longer earthing pin also of elongate rectangular section. Such a plug is used in connection with a socket outlet having a movable shutter which closes its live sockets when not in use but which is moved aside by the entry of the longer earthing pin when a plug is inserted into the socket.

An object of the invention is to provide a means for preventing the unintentional withdrawal of such a plug connector from its socket outlet whether by inadvertence or accident, such as accidental jerking of the flexible cable connected to the plug. Such unintentional interruption of the electrical supply can have serious consequences in the case of certain electrical apparatus such as a freezer, or a computer or data storage apparatus where stored information might be lost by a power interruption, or in the case of a clock or a timer controlling other apparatus.

According to the present invention, an electrical plug connector is provided with means for positively locking it against withdrawal from a socket outlet into which it has been fully inserted, which means is capable of being operated to lock and/or to release the plug whilst it is in its fullyinserted position.

In one form of the invention, an electrical plug connector has one of its pins provided with a locking member which is movable into a retracted position, in which it permits the insertion and withdrawal of the plug into and from a socket outlet, and into a locking position in which it projects beyond the cross-sectional periphery of the said pin so as to engage behind an abutment afforded by some part of a socket outlet into which the plug connector is inserted, and thereby prevents withdrawal of the plug connector from the outlet. The locking member may be capable of being moved to its retracted position from its locking position by means accessible from outside the plug connector with the latter inserted into the socket outlet.The same means may be usable to move the locking member from its retracted position into its locking position when the plug connector has been inserted into a socket outlet, although it is possible for either movement to be effected by some other means or in some other way, e.g. by spring-loading the locking member.

Thus in a preferred construction of the invention, an electrical plug connector has one of its pins, preferably an earthing pin, formed by a fixed body of elongate, e.g. rectangular, cross-section and a separate tip member of corresponding profile rotatably mounted at the outer end of the body of the pin by means of a spindle extending through a longitudinal bore in the pin, the spindle being rotatable from outside the plug with the latter inserted in a socket outlet so as to rotate the tip member between a retracted position in which it lies flush with the body of the pin to permit the insertion and withdrawal of the plug connector into and from the outlet, and a locking position in which it extends transversely to the body of the pin and projects therefrom so as to act as a locking member preventing the withdrawal of the plug-connector from the socket outlet.

The spindle may for example be joined at its rear end, remote from the tip member, to a rotatable head journalled in the body or cover of the plug and accessible at the rear face of the plug, where it may for instance be formed with a fingerpiece or with a screwdriver slot for manual rotation.

From another aspect the invention comprises the combination of an electrical plug connector with a movable locking member, in any of the forms described above, and a socket outlet formed to provide an abutment behind which the locking member of the plug connector can engage when moved into its locking position after insertion of the plug connector into the socket outlet.

The invention may be carried into practice in various ways, but one specific embodiment thereof will now be described by way of example only and with reference to the accompanying drawings, in which: Figure 1 is an isometric view of a three-pin plug connector fitted with a locking tip on its earth pin, Figure 2 is a rear view in elevation of the plug connector of Figure 1, and Figure 3 is a cross-section of the plug connector of Figures 1 and 2 on the line Ill-Ill in Figure 2.

In the illustrated embodiment of the invention, the plug connector 10 is of the well-known 3-pin 13-amp fused type, with fixed line and neutral conductor pins 11 and 12 of elongate rectangular cross-section and a metal earthing pin 13 also of elongate rectangular cross-section and slightly greater in length than pins 11 and 12. The line and neutral pins 11 and 12 have bevelled tips to facilitate their entry into the holes of a socket outlet, and the earthing pin 13 has a separate, rotatably mounted tip member, referred to as the locking member 14, which is similarly bevelled.The plug connector 10 is of the usual moulded insulating plastics construction, with a body 15from which the three pins 11,12,13 protrude and a detachable cover 16 secured by a screw 17, and contains the usual line, neutral and earth terminals 18 (one of which can be seen in Figure 3) for connecting a three-core flex to the three pins 11, 12, 13, a fuse holder and fuse, and a cord grip whose tightening screws are shown at 19 in Figure 1.

The rotatable locking member 14 is of elongate rectangular profile corresponding to the crosssectional profile of the fixed body 20 of the earthing pin 13, and is mounted on the end of the body 20 by means of a metal spindle 21 extending within a longitudinal bore formed in the body 20 of the earthing pin, the spindle 21 being rotatable about its longitudinal axis in the body 20. The locking member 13 is fixed to one end of the spindle 21 whose other end is embedded in and keyed to a moulded plastics head 22 of circular section which is rotatable in a circular aperture 23 formed in the wall of the plug cover 16, the head 22 having a circumferential flange 24 which rides in a stepped annular recess 25 in the internal circumference of the aperture 23 to retain the head.The head 22 is formed with a diametral slot 27 in its outer face 28 which is exposed at the back of the plug connector 10, to receive the tip of a screwdriver for rotating the head 22, and with it the spindle 21 and the locking member 14.

In use, prior to insertion of the plug connector 10 into a socket outlet, the locking member 14 lies or is turned into its retracted position (not shown) in which it lies flush with the body 20 of the earthing pin 13, i.e. with its major axis lying parallel to the major axis of the cross-section of the body 20. With the locking member 14 in this retracted position the plug connector 10 can be inserted into a corresponding socket outlet, the entry of its earthing pin opening the shutter of the live socket holes in the usual manner two permit the live and neutral pins 11 and 12 to enter the socket outlet.With the plug connector 10 fully inserted, the head 22 is rotated through 90 degrees, by means of a screwdriver applied to the slot 27, to turn the locking member 14 carried by the spindle 21 into its locking position as illustrated, in which the member 14 projects beyond the two opposite external sides of the body 20 and will engage behind a suitable abutment provided in the interior of the socket outlet, to positively prevent the withdrawal of the plug connector from the outlet. This abutment may for example be formed by the end of the usual rectangular-section metal terminal sleeve embedded in the plastics body of the socket outlet and connected to the earth wire of the associated electrical spur or circuit.Usually the earthing pin of the plug connector extends through and beyond the open remote end of the socket earthing terminal sleeve when the plug connector is fully inserted, enabling the locking member 14 at its tip to be turned into its protruding locking position and to engage behind the end of the metal terminal sleeve, so that the sleeve end and possibly also the insulating plastics backing wall surrounding the sleeve provide the necessary locking abutment.

Otherwise, recesses or slots may be formed in the wall of the metal terminal sleeve and if necessary also in its plastics backing material to accommodate the protruding ends of the locking member and form the cooperating abutment.

So long as the locking member 14 remains in its locking position as described, the inserted plug cannot be withdrawn from the socket outlet. Thus the invention provides a valuable additional safety measure, particularly for domestic use where children are present, as well as guarding against the inadvertent interruption of the power supply to any apparatus being supplied from that outlet, with possible undesirable consequences.

When it is desired to withdraw the plug connector 10, the head 22 is simply rotated by means of a screwdriver through a right angle to turn the locking member 14 back to its flush retracted position, enabling the plug connector to be pulled out of the socket in the usual manner.

Claims

1. An electrical plug connector having protruding conductor pins and/or an earthing pin for insertion into correspondingly-positioned sockets of a socket outlet thereby to achieve an 'inserted position' of the plug connector with respect to the socket outlet, and having locking means for positively locking the plug connector in its 'inserted position', the locking means being operable to lockand/orto release the plug connector whilst it is in its said 'inserted position'.

2. An electrical plug connector as claimed in claim 1 in which one of its protruding conductor pins is provided with a locking member which is movable into a retracted position, in which it permits the insertion and removal of the plug connector into and from the socket outlet, and into a locking position in which it projects beyond the crosssectional periphery of the pin so as to be capable of engaging behind orwith an abutment afforded by some part of the socket outlet into which the plug connector is inserted, and thereby prevents withdrawal of the plug connector from its 'inserted position'.

3. An electrical plug connector as claimed in claim 2 in which the locking member is capable of being moved to its retracted position from its locking position by operating means accessible from outside the plug connector with the latter in its 'inserted position'.

4. An electrical plug connector as claimed in claim 3 in which the same operating means is usable to move the locking member from its retracted position into its locking position when the plug connector is in its 'inserted position'.

5. An electrical plug connector having protruding conductor pins and/or an earthing pin for insertion into correspondingly-positioned sockets of a socket outlet, one of said pins being formed by a fixed body of elongate, e.g. rectangular, cross-section, and locking means formed by a separate locking member of corresponding profile which is rotatably mounted with respect to the one pin by means of a spindle extending through a longitudinal bore in the one pin, the spindle being rotatable from outside the plug connector, with the latter inserted into a socket outlet, so as to rotate the locking member between a retracted position in which it lies flush with the body of the pin to permit the insertion and withdrawal of the plug connector respectively into and from the socket outlet, and a locking position in which it projects from the body of the pin to prevent withdrawal of the plug connector from the socket outlet.

6. An electrical plug connector as claimed in claim 5 in which the spindle is joined to a rotatable head journalled in the body, or a cover, of the plug and accessible from the face of the plug connector which is exposed when in its inserted position in the socket outlet.

7. An electrical plug connector as claimed in claim 6 in which the rotatable head is provided with a fingerpiece or with a screwdriver slot or socket for manual rotation.

8. The combination of an electrical plug connector, as claimed in any one of the preceding claims, with a socket outlet which has an abutment with which the locking means can engage when moved into its locking position after insertion of the plug connector into the socket outlet.

9. An electrical plug connector substantially as described herein with reference to the accompanying drawings.