GB2287842A

GB2287842A - Electrical socket

Info

Publication number: GB2287842A
Application number: GB9505423A
Authority: GB
Inventors: Graham Johns Spencer
Original assignee: TENBY IND Ltd
Current assignee: TENBY IND Ltd
Priority date: 1994-03-26
Filing date: 1995-03-17
Publication date: 1995-09-27
Anticipated expiration: 2015-03-17
Also published as: GB9406048D0; GB9505423D0; GB2287842B

Abstract

A socket outlet for a three pin plug has a face plate (10) behind which is located a shutter (15). The shutter is biased to the locked position by a spring (17) and is moved to an unlocked position by the action of the earth pin (26) of a plug. During this movement the shutter tilts about a pivot edge (22). The shutter has a pair of side limbs which lie behind the apertures of the live and neutral pins and these limbs have inclined faces (21) which are engaged by the pins to move the shutter against the action of the spring from the operative position in which the side limbs prevent access to the live and neutral contacts, to an inoperative position. <IMAGE>

Description

ELECTRICAL SOCKET This invention relates to socket outlets of the three pin type and comprising a face plate, a contact housing secured to the face plate, line neutral and earth contacts mounted in the housing, respective apertures formed in the face plate and through which in-use the respective pins of a three pin plug can pass to make electrical connections with the respective contacts and a shutter which in the operative position prevents access to at least the line contact, such shutter being moved to the inoperative position upon insertion of the pins of a plug.

Such socket outlets are well known and it is cdnventional for the earth pin of the plug to be slightly longer than the line and neutral pins. In one known system the action of inserting the earth pin moves the shutter to the inoperative position thereby to allow the line and neutral pins to move into engagement with the respective contacts. In another known system the shutter is operable by the line and neutral pins which upon insertion into the respective apertures first unlock the shutter and then with continued movement, move the shutter to the inoperative position.

The object of the present invention is to provide a socket outlet of the type specified in a simple and convenient form.

According to the invention in a socket outlet of the kind specified the shutter includes a part engagable by the earth pin of a plug and operable with inward movement of the earth pin, to unlock the shutter, and further parts engagable by the line and neutral pins to move the shutter from its operative to its inoperative position.

An example of a switch socket in accordance with the invention will now be described with reference to the accompanying drawings in which: Figure 1 is a part sectional side elevation on the line B-B of Figure 2, Figure 2 is front view looking in the direction of the arrow A of Figure 1, and Figure 3 is a part sectional side elevation on the line C-C of Figure 2.

Referring to the drawings the socket comprises a face plate 10 in which is formed three through apertures appropriate for'a 13 amp three pin plug having flat pins. The aperture for the earth pin is indicated at 11 and those for the line and neutral pins at 12 and 13 respectively.

Secured to the back face of the face plate 10 is a contact housing (not shown) which supports respective line, neutral and earth contacts. The housing and face plate may also carry a switch mechanism.

The rear face of the face plate is formed with a recess 14 which houses a shutter 15 of generally inverted "T" configuration. In Figures 1 and 3 the shutter as shown in solid outline, is in a so called operative position with the side limbs 16 lying behind the line and neutral apertures 12, 13 to prevent access to the respective contacts. As seen in Figure 3 the faces of the side limbs 16 which are presented to the apertures 12, 13 are inclined downwardly towards the face place and as seen in Figure 1, the shutter is biased upwardly by the action of resilient means conveniently in the form of a coiled compression spring 17.

The central limb of the shutter 15 defines a flat face 18 which in the locked and operative position of the shutter as shown in solid outline in Figure 1, lies in contact with the base wall of the recess 14. The face 18 is interrupted by a recess 19 in which locates a projection 20 formed on the face plate and the upper face of the projection and the adjacent face of the recess 19 cooperate to prevent downward movement of the shutter by for example the engagement of a screw driver with the inclined faces of the side limbs 16 of the shutter. The central portion of the shutter defines a further flat face 21 which in the locked position of the shutter inclines downwardly and away from the base wall of the recess 14. The faces 18 and 21 define between them a pivot edge 22 which extends transversely of the shutter and with the base wall of the recess defines a pivot axis The shutter is biased about the pivot edge by the action of the spring 17. The spring 17 is interposed between the lower side wall 23 of the recess and an abutment face 24 defined on the shutter. Conveniently the face 24 inclines upwardly and away from the face plate and forms the end face of an open ended recess formed in the shutter.

At its upper end the central limb of the shutter is provided with a projection 25 which lies in the path of the earth pin 26 of a plug. In operation, as a plug is inserted into the socket the earth pin 26 engages the projection 25 and the shutter is moved angularly about the pivot edge 22. The pivotal movement of the shutter continues until the face 21 on the shutter moves into engagement with the base wall of the recess and this movement is sufficient to effectively remove the projection 20 from the recess 19. During this angular movement the shutter may move downwardly a limited extent to permit the projection 25 to ride on the side face of the earth pin. The downward movement is facilitated by rounding the upper corner of the projection 20. The unlocked position of the shutter is illustrated in dotted outline in Figure 1. It will be appreciated however that the shutter is still in the operative position vvith the limbs 16 of the shutter being disposed behind the apertures 12.

As the line and neutral pins pass through the respective apertures they will engage the inclined surfaces on the side limbs 16 and the reaction force produced will move the shutter downwardly against the action of the spring 1 7 to the inoperative position to permit the line and neutral pins to engage the respective contacts. Figure 3 illustrates in solid outline the limb 16 with the shutter in the operative position, the immediately adjacent dotted outline indicating the position of the limb in the unlocked position and the lower dotted outline indicating the position of the limb in the inoperative position of the shutter. As the plug is withdrawn from the socket the shutter moves in the reverse direction to that described firstly to the operative position, and then as the earth pin is disengaged from the projection 25, the shutter pivots about the pivot edge 22 to assume the locked position. It will be noted that as the shutter tilts as it moves from the locked to the unlocked position the angle of inclination of the inclined surfaces of the side limbs 16 is reduced slightly and this facilitates the movement of the shutter under the action of the line and neutral pins of the plug.

In order to prevent displacement of the shutter to the inoperative position by a tool inserted through one only of the apertures 12 once the shutter has been unlocked, it is arranged that the shutter is displaced angularly if force is applied to one only of the inclined faces of the limbs 16. This will have the effect of moving the limb 16 opposite to that against which force is applied, closer to the base wall of the recess 4. As seen in Figure 3, projections 27 are provided on the base wall of the recess at the opposite sides thereof. In normal operation the limbs 16 slide over the projections but when the shutter is displaced angularly as described one of the limbs will engage with the respective projection to prevent displacement of the shutter to its inoperative position. As described the rear face 28 of the centre limbs of the shutter is flat and in the unlocked position of the shutter lies adjacent a flat surface of the contact housing.

In order to facilitate angular displacement of the shutter the rear face 28 may be of "V" form with the aforesaid flat surface of the contact housing being provided with a V groove of larger angle than that of the shutter.

Claims

1. A socket outlet of the kind specified in which the shutter includes a part engageable by the earth pin of the plug and operable with inward movement of the earth pin to unlock the shutter and further parts engageable by the live and neutral pins of the plug to move the shutter from its operative to its inoperative position.

2. A socket outlet according to Claim 1, in which said shutter is spring biased to the locked position, the shutter and face plate defining interengageable locking means which release as said part of the shutter is moved by the earth pin against the action of the spring.

3. A socket outlet according to Claim 2, in which the shutter during its movement between the locked and unlocked positions pivots about an axis transverse of the shutter the axis being defined by a pivot edge formed at the junction of two adjacent faces of the shutter and a surface of the face plate.

4. A socket outlet according to Claim 3, in which the shutter is inverted "T" configuration, the centre limb of the shutter defining said part for engagement by the earth pin and also a recess which forms part of said locking means, the other part of the locking means being defined by a projection on the face plate and which in the locked position of the shutter lies within said recess to prevent movement of the shutter towards the inoperative position.

5. A socket outlet according to Claim 4, in which the side limbs of the shutter have inclined faces for engagement by the live and neutral pins of the plug whereby when the shutter has been moved to the unlocked position by the earth pin, the engagement of the live and neutral pins and further movement of the plug will cause movement of the shutter from the operative to the inoperative position.

6. A socket outlet according to Claim 4, in which engagement of one of said inclined surfaces by a screw driver or the like when the shutter is in its unlocked position, will impart a twisting movement of the shutter, such that the limb defining the other of said surfaces is moved to a position to engage a stop to prevent movement of the shutter to the inoperative position.