GB2186746A

GB2186746A - Dummy plugs

Info

Publication number: GB2186746A
Application number: GB08602850A
Authority: GB
Inventors: Timothy Shorrock
Original assignee: Individual
Current assignee: Individual
Priority date: 1986-02-05
Filing date: 1986-02-05
Publication date: 1987-08-19
Anticipated expiration: 2006-02-05
Also published as: GB2186746B; GB8602850D0

Abstract

Known dummy plugs are made of an electrically insulating material and merely plug into an electrical socket to cover the terminal holes. However such safety plugs can be pulled out of the socket and thus do not prevent unauthorized use. The present invention provides a dummy plug (1) having at least two elongate pins (7, 9), at least one of which pins (7, 9) is movable to thus secure the plug (1) in the socket. In one example, the pins (7, 9) are pivotal from a parallel ready-for-use position towards each other, by means of a cam arrangement (19, 25). Thus by moving the cam arrangement (19, 25) using a suitable key (33), the pins (7, 9) can be angled relative to each other locking the plug (1) in the socket. In a second example, one of the pins 41 has a free end region of larger cross-section than the majority of the length of the pin. After insertion of the plug in a socket the pin is rotated about its longitudinal axis to prevent removal of the plug. <IMAGE>

Description

SPECIFICATION Improvements Relating to Safety Plugs The present invention relates to a safety plug for use with an electrical socket.

Electrical sockets for use in connecting an appliance to a mains supply of electricity have at least two terminal holes into which the pins of an electrical plug connected to the appliance, can be inserted. Some electrical sockets include a third terminal hole for an earth connection. When not in use the terminal holes in an electrical socket are exposed, and the socket can thus be used by any unauthorised person, or can be a potential danger to inquisitive children.

It is already known to provide a safety plug which has a number of suitably arranged pins, the safety plug merely being a suitably shaped piece of electrically insulating plastics material. Such a plug is merely inserted in the terminal holes of a socket to blank off the socket. However, whilst such a plug may deter an inquisitive child who is not strong enough to puli out the plug, it does not prevent unauthorised adult use.

The aim of the present invention is to provide a safety plug which can be locked in a socket to prevent unauthorised usage of the socket and to reduce the risk to inquisitive children.

According to the present invention there is provided a safety plug for use with an electrical socket, said plug having at least two elongate pins, at least one of which pins is movable to thus secure the plug in the socket.

By inserting the safety plug of the present invention into an electrical socket and moving the or each movable pin, the plug can be locked in the socket, preventing unauthorised usage and removing any potential danger to children.

In one embodiment of the present invention the safety plug has three normally parallel pins, mounted on a body, two of the pins being pivotal towards each other by means of a cam arrangement operable by a key. Thus, by inserting the safety plug in a socket with the pins parallel to each other, the cam arrangement can then be moved by the key so that the said two pins pivot, preventing removal of the safety plug from the socket. By then removing the key, the socket cannot be used by any unauthorised personnel.

In another embodiment of the present invention, the safety plug has three parallel pins mounted on a main body. Two of the pins are generally rectangular in transverse cross-section, so as to be substantially complementary with their respective rectangular terminal holes in the socket. However, whilst the free end region of the third pin is also of a complementary rectangular transverse crosssection, the remainder of this third pin has reduced dimensions. This third pin is also rotatable about its longitudinal axis by suitable key means provided in the main body. Thus, by rotating this third pin when the plug has been inserted in a socket, the larger free end region of the said third pin, which is then located within the inner cavity of the socket, prevents the plug from being removed from the socket. Said key means can be subsequently operated to allow the safety plug to be removed.

The present invention thus provides a simple means for blanking off an electrical socket.

The present invention will now be further described, by way of exampie, with reference to the accompanying drawings, in which: Fig. 1 is a perspective view of one embodiment of the present invention; Fig. 2 is a perspective view of part of the embodiment of Fig. 1, in the unlocked position; Fig. 3 is a perspective view of the part of Fig. 2, in the locked position; and Fig. 4 is a perspective view of another embodiment of the present invention.

The embodiment of the present invention illustrated in Figs. 1 to 3 of the accompanying drawings comprises a main body 1 having a planar face 3 from which three rectangular pins 5,7 and 9, project.

As viewed in Figs. 1 and 2, the three pins 5,7, 9 are normally parallel to each other so that they can be easily inserted in the respective earth, live and neutral terminal holes in an electrical socket (not shown). However, whilst the earth pin 5 is fixed in position, projecting normally from the planar face 3 of the main body 1,the othertwo pins 7,9 are pivotally mounted in apertures 11 in the main body 1. Each of these other two pins 7,9 is mounted on an axle 13 which extends across an aperture 11, and each pin 7, 9 has an axial projection 15 which can be engaged by a cam arrangement 17.

The cam arrangement 17 comprises a circular disc 19 which is rotatably mounted in a recess 21 in the main body 1, the disc having peripheral cutaway regions 23, the circumferential end edges 25, 27 of which can be brought into engagement with the said axial projections 15 on the pins 7, 9. The peripheral cutaway regions 23 are so designed that when the disc 19 is rotated in one direction to bring one end edge 25 of a peripheral cutaway region 23 into engagement with an angled surface 29 on an axial projection 15 of one of the pins 7, 9, the equivalent end edge 25 of the other cutaway region 23 simultaneously engages an angled surface 29 on the other of said pins 7, 9. Continued rotational pressure on the disc 19 in said one direction merely holds the pins 7,9 in the parallel plug-unlocked position, illustrated in Fig. 2.However, with rotation of the disc 19 in the opposite rotational direction the base of each peripheral cutaway region 23 cams the axial projection of one of the pins 7, 9 across an aperture 11, thus causing the pins 7,9 to pivot on axles 13 so as to converge towards a plug-locked position-see Fig. 3. Thus by moving the pins 7, 9 to the converged position of Fig. 3 after the plug has been inserted in an electrical socket, the plug is locked in the socket and cannot be removed until the disc 19 has been rotated to move the pins 7,9 back to the plug unlocked position of Fig. 2.

To rotate the disc 19 a key 33 is provided which has two spaced apart pins 35 which can engage in complementary bores 37 on the disc 19. Any other form of key and engaging means can of course be substituted. Further, the cam arrangement 17 may be sealed by a facing plate (not shown).

In another embodiment of the present invention illustrated in Fig. 4 of the accompanying drawings, the plug has a main body 39 with three parallel pins 41,43,45 projecting from a planar face 47 thereof.

Two pins 43,45 are rigidly fixed to the main body 39 and the third pin 41 is rotatably mounted on the main body 39. Whilst the two pins 43,45 each have a uniform rectangular transverse cross-section along their length, this rectangular cross-section being complementary to the cross-section of the terminal holes in the socket into which the plug is to be fitted, the third pin 41 has solely an end region 47 of like rectangular cross-section, the remainder 49 of this third pin 41 being of reduced transverse dimensions. Thus, by inserting the plug into a suitable electrical socket with the third pin 41 in the rotational position illustrated in Fig. 4, the third pin 41 can be rotated, the end region 47 being within the large internal cavity of the socket. The plug cannot then be extracted from the socket until the third pin 41 is returned to the position illustrated in Fig. 4. To rotate this third pin 41 a screwdriver slot 51 is provided. However, any other suitable detachable key and socket means may be substituted.

In both of the above described embodiments of the present invention, the whole plug is made of an electrically insulating plastics material.

Alternatively, only parts of the plug can be made of such electrically insulating material.

The present invention thus provides a simple safety plug which can be locked in an electrical socket preventing unauthorised use and reducing the danger two inquisitive children.

Claims

1. A safety plug for use with an electrical socket, said plug having at least two elongate pins, at least one of which pins is movable to thus, in use, secure the plug in the socket.

2. A safety plug as claimed in claim 1, in which one pin is pivotally mounted and is pivotal towards another pin, by means of a cam arrangement.

3. A safety plug as claimed in claim 2, in which two pins are pivotally mounted on parallel axes so as to be pivotal by the cam arrangementfrom a parallel ready-for-use position to a relatively angled position.

4. A safety plug as claimed in claim 3, in which the pins are pivotal towards each other from the parallel ready-for-use position.

5. A safety plug as claimed in any one of claims 2 to 4, in which the cam arrangement is formed by a planar disc rotatably mounted in the plug, the disc having camming surfaces which engage an axial extension of each said pivotal pin.

6. A safety plug as claimed in claim 5, in which the camming surfaces are formed in the peripheral edge of the disc, a suitable camming surface being provided for each pin.

7. A safety plug as claimed in any one of claims 2 to 6, in which the cam arrangement is operable by a releasable key.

8. A safety plug as claimed in claim 1, in which the or each movable pin is rotatable about its longitudinal axis and is rectangular in transverse cross-section with a reduced cross-section for the majority of its length, the free end region of the or each movable pin being of standard transverse cross-section.

9. A safety plug as claimed in claim 8, in which the movable pin is rotatable by a suitable extraneous tool.

10. A safety plug as claimed in any one of the preceding claims, in which the plug is constructed at least in part of an electrically insulating material.

11. A safety plug for use with an electrical socket, constructed substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.