GB2105534A

GB2105534A - Electrical plugs

Info

Publication number: GB2105534A
Application number: GB08221829A
Authority: GB
Inventors: Johann Storm; Stanley Oshry
Original assignee: Individual
Current assignee: Individual
Priority date: 1981-07-29
Filing date: 1982-07-28
Publication date: 1983-03-23
Also published as: AU8644382A; GB2105534B

Abstract

An electrical plug is provided of the type having pins (3, 16) projecting from a base (6) and adapted for co-operation with a complementary socket, and a cover (5) releasably attached to the base to cover the electrical terminals and pins which would otherwise be exposed in use. The cover slides onto the base using grooves (9) and is retained by an arrangement which includes a catch (14, 15) which is releasable only by a specific movement of a pin (16) relative to the base. Preferably the pin is movable axially to effect such release and is spring biased or otherwise locked such as by a cam and guide arrangement (22, 23, 24) to a position in which the catch holds the base and cover in association with each other. <IMAGE>

Description

SPECIFICATION Electrical plugs This invention relates to electrical plugs and, more particularly, relates to means for securing the cover to the base of a plug.

Electrical plugs such as those used for connecting electric wires from an appliance to a wall socket often comprise a base having connector pins extending therethrough and a releasable cover for the base and which electrically insulates the operatively outer ends of the pins. It is necessary to gain access to said ends of the pins in order to connect or disconnect wires therefrom, and it is thus desirable that the cover be easily and quickly releasable from the base. Prior art plugs have proposed a variety of devices for securing the cover to the base such devices including clips, screw-threaded arrangements and the like. One of the problems associated with most prior art plugs is that a tool such as, for example, a screwdriver, is required to effect disengagement of the cover from the base even in the case where a clip is employed to secure the cover over the base.

In accordance with this invention there is provided an electrical plug comprising a body having an electrically insulating base and cover assembly, and at least two electrically conductive pins extending through the base, at least one of the pins having means associated therewith for acting as a catch to maintain the cover operatively on the body, said pin being movable between two positions, one in which it acts as said catch to maintain the cover in position relative to the base and one in which the base and cover are separable.

The plug may be constructed so that it may be easily and quickly dismantled at least to some extent without the aid of a tool.

Further there is preferably provided for the cover to slidably engage the base along groove formations orientated substantially at right angles to the longitudinal axis of the pins and for the movable pin to releasably act as a catch to prevent relative sliding movement of the cover and base when in an assembled position.

Still further there is preferably provided for at least one pin to be movable in the direction of its longitudinal axis and for the plug to include means for biasing or urging the said pin towards the lid so that a part associated with the pin engages a co-operating formation on the lid.

Yet further there is preferably provided for at least one pin to be rotatable about its longitudinal axis and to include formations which engage cooperable formations in the lid in a catch-like manner when the pin is in a certain angular position of rotation and thereby releasably secure the lid to the base.

Further preferable features of the invention provide for the biasing means to be a compression spring, for the movable pin to be an earth pin, and for the plug base and cover assembly to be moulded from a plastics material.

There is also preferably provided for the plug to comprise a cover and a base and biasing means between the cover and the base, the cover and base including co-operating formations whereby removal of the cover from the base can only be effected by movement against the biasing means.

Embodiments of the present invention will now be described by way of example with reference to the accompanying drawings in which: Fig. 1 is a sectional side elevation of a first embodiment of the invention; Fig. 2 is a partly sectioned exploded isometric view of the plug illustrated in Fig. 1 but illustrating also a variation of the means for urging the earth pin to a locked position; Fig. 3 is a sectional side elevation of a second embodiment of the invention; Fig. 4 is a sectional exploded oblique projection of a third embodiment of the invention; and, Fig. 5 is an isometric view illustrating the accomodation of rectangular cross-sectioned conductive pins.

Referring firstly to Figs. 1 and 2 an electrical plug 1 is shown comprising a body 2 made of electrically insulating material, conveniently injection moulded plastics material, having electrically conducting pins 3 for insertion into a standard wall socket. The body comprises two sections namely, a cover 5 and a base 6. The cover is separable from the base 6 to provide access to terminals associated with the pins and the plug is shown in Fig. 2 in a disassembled condition. The pins 3 extend through the base and electrical wires 7 are attached, in use, to terminals formed at the operatively outer ends of the pins in known manner.

The cover and base are, in this case, rectangular and have co-operating tongue 8 and groove 9 formations for releasably securing them together. In this embodiment the groove formations 8 are located in the lower inside surfaces of sidewalls 10 of the cover and the tongues 8 are defined by the free longitudinal edges of the base which is substantially planar apart from one endwall 11 made integral therewith. The endwall has an entrance recess for an electrical cable in use and also, the base has integral cable engaging retaining members 12 inclined towards each other to grip the outer surface of a cable in use.

For use in effectively gripping small diameter flex or ripcord upstanding retainer members 13 are provided which diverge from a space between them on the inside of the earth pin. These retainer members terminate short of shield members on each side of the earth pin terminal and can be omitted entirely if the inner edges of the cable retaining members are sufficiently close together.

Individual insulated conductors can be passed around the retainer members 13 and to their terminals to render them effective. In the modification shown in Fig. 2 such retainer members 1 3 have been omitted.

In addition to the tongue and groove formations referred to above, the cover has a ramp formation 1 4 which co-operates with the earth pin assembly to define a catch in use. This ramp formation 14 extends in the same direction as the grooves 8 and is located centrally between the grooves in the top of the cover. The ramp is inclined from the end of the cover corresponding to commencement of sliding of the cover into its closed position and has a recess 1 5 shaped to receive the earth pin thumb screw connector in the fully closed position of the cover.

The earth pin 1 6 is movable in the direction of its longitudinal axis, and has in the variation illustrated in Fig. 1, associated therewith, a compression 17 which biases the earth pin 1 6 in a direction towards the cover 5 in the assembled condition.

Thumb screws 1 8 are provided for securing conductor wires to the terminal ends of each pin, these thumb screws conveniently being of insulating material.

In use, electrical wires 7 are attached to the outer or terminal ends of the pins by means of the thumb screws and the cover will thereafter be positioned on the base by sliding it into position along the grooves 8. As the lid moves relative to the base, the ramp formation 14 causes the earth pin 13, in the case of the variation illustrated in Fig. 1, to move against the bias of the compression spring 14 by engaging the earth pin thumb screw. The earth pin thumb screw thus rides over the end of the ramp as the cover slides into the final assembled condition and snaps into the recess 1 5 formed near the end of the ramp.

The cover will thus be locked in position and will be fixed relative to the base unless the earth pin thumb screw is withdrawn from the recess 1 5 which is achieved by pulling the earth pin axially against its biasing.

It will be appreciated that the cover will easily and quickly be removed from the base by simply manually pulling the earth pin against the compression spring. This will effectively remove the end of the earth pin thumb screw from the recess 1 5 and the lid can thereafter be slid off the base. It will, however, be impossible to remove the lid from the base in the direction of the longitudinal axis of the pins as the groove formation 8 restrain movement in this direction.

Pins other than the earth pin could equally well be used as the securing member.

It would equally well be possible to restrict the movement of the pin to a rotational one about the longitudinal axis of the pin with or without a biasing action and with or without axial movement of the pin as well.

One such variation is illustrated in Fig. 2 of the drawings which shows, an exploded view of the earth pin arrangement of the variation. In this case the operatively outer or terminal end 19 of the earth pin is provided with a knurled outer surface and integral externally screw-threaded spigot 20 for co-operating with an internally screw-threaded thumb screw 21. The knurled surface of the end portion 1 9 of the earth pin has, in the operative position, press-fitted thereto a cam follower member 22. The cam follower member has two cam followers 23 adapted to cooperate with a cam surface 24 formed integral with the base.

Once the cam follower member has been press-fitted to the earth pin the latter can only move axially, in a direction to disengage the thumb screw from the recess 1 5, when the cam follower formations 23 are aligned with deep recesses 25 in the basically tubular formation having the cam surface formed in its free edge.

The above arrangement is such that the earth pin can be rotated to a position in which the cam follower formations snap into shallow recesses 26 formed in the cam surface in which position the thumb screw 21 is engaged in the recess 15 in the cover.

Rotation of the earth pin to cause the cam follower formations to align themselves with the deep recesses 25 is the first step in removing a cover whereupon the earth pin can be pulled axially away from the base which causes the thumb screw 21 to disengage the recess and the lid can be slid from the base in the manner described above.

As in the previous case the thumb screw has, in addition to a knurled outer periphery, a pair of crossed slots in its upper surface to enable a screw driver to be empioyed if this be necessary.

Again the thumb screws are preferably made of electrically insulating material and have electrically conductive parts moulded therein for effecting electrical connection to the respective pins.

Referring now to the second embodiment which is illustrated in Fig. 3 a plug 27 is shown comprising a body 28 and electrically conducting pins 29. The body, as in the previous embodiment, comprises a cover 30 and a base 31. In this embodiment, movement of the cover relative to the base in a direction parallel to the longitudinal axis of the pins is prevented, not by a tongue and groove arrangement as in the previous embodiment, but by overlapping portions of both the cover and the base relative to each other. These overlapping portions are indicated by numeral 32 and are located at the top of the endwall 33 which accomodates the cable in use and at the lower front end (adjacent the earth pin).

The lid is thus slidably connected to the base over the short length of overlap. As in the previous embodiment, movement of the cover relative to the base in a direction at right angles to the longitudinal axis of the pin i.e. in the plane of sliding, is prevented by a movable earth pin assembly 34 biased, or urged, in the direction of the cover is described above. All that is necessary to locate the cover relative to the base is to align the two parts with the portions which are to overlap in registration with each other and slide them home until the earth pin snaps into position, or can be moved into its operative position, as the case may be.

In the third embodiment of the invention shown in Fig. 4 formations on the cover 35 and base 36 co-operate in a different way to facilitate the securing of the lid to the base. The cover in this embodiment comprises a top wall 37 and four side walls 38. The cover is substantially square in plan view and includes, in two opposite sides thereof, formations for co-operation with the base 36. One of said opposite sides includes a groove formation 39 wherein is housed a sinuous leaf spring 40. The second of the opposite sides has a small ridge 41 extending along the length thereof.

During assembly the co-operating leading edge 42 of the base 36 is located within the grbdve formation 39. The leading edge is then urged against the leaf spring to compress it, and in that condition, the trailing edge 43 is then pushed up into the inside of the cover and, as the trailing edge passes the ridge 41, the leaf spring urges the trailing edge flush against the side of the cover on which the ridge is located.

Movement of the cover relative to the base in a direction parallel to the longitudinal axis of the pins is thus prevented. A pin 44 biased in the direction of the cover, as in the previous two embodiments, is used to prevent involuntary removal of the cover from the base by moving the base in a direction tending to compress the leaf spring.

It will be appreciated that there may be many variations to the above described embodiments without departing from the scope of the invention.

In particular, as previously mentioned, the movement of the pin could be effected in various different ways and may be about an axis transverse to the axis of the pin itself. Movement is thus not restricted to the direction of the longitudinal axis of the pins. It will also be evident that the shapes and configurations of the formations on the lid and base can be many and various. The material from which the body of the plug is made is preferably a moulded plastics material. The types of springs which could be used to bias the pins are also many and varied.

Envisaged within the scope of the invention is a spring integrally formed from the plastics material from which the plug body is manufactured.

It is important to note that the invention is not confined in application to pins of circular crosssection and can be applied to pins of any other cross-section. Simply to illustrate this point a pin 45 of rectangular cross-section is shown in Fig. 5 as applied to the variation of the embodiment illustrated in Fig. 2. In this case the cam follower member 46 is simply adapted to be press-fitted onto an end portion 47 of the rectangular crosssectioned pin. Alternatively a "conversion"fitting can be attached to the one end of such a pin with the "conversion" fitting having an external circular shape, and an internal rectangular shape.

Claims

1. An electrical plug comprising a body having an electrically insulating base and cover assembly, and at least two electrically conductive pins extending through the base, at least one of the pins having means associated therewith for acting as a catch to maintain the cover operatively on the body, said pin being movable between two positions, one in which said catch is operative to maintain the cover in position relative to the base and one in which the base and cover are separable.

2. An electrical plug as claimed in claim tin which the cover slidably engages the base along groove formations extending at substantially right angles to the longitudinal axis of the pins.

3. An electrical plug as claimed in claim 2 in which the movable pin assembly defines a releasable catch to prevent relative sliding movement of the cover relative to the base in the position in which it acts to maintain the cover in position relative to the base.

4. An electrical plug as claimed in claim 3 in which the pin is movable axially to release said catch.

5. An electrical plug as claimed in claim 4 in which the pin is spring biased to a position in which it operates as a catch and a co-operating ramp is provided on the cover to urge the pin against its biasing during closing of the plug but to snap into co-operation with a complementary recess or formation in the fully closed position.

6. An electrical plug as claimed in any one of claims 1 to 4 in which the pin is spring biased to a position in which it operates to maintain the cover in position relative to the base.

7. An electrical plug as claimed in any one of claims 1 to 4 in which a cam surface and cam follower are associated with the movable pin to releasably lock the pin in a position in which the cover and base are interengaged.

8. An electrical plug as claimed in claim 7 in which the pin is axially movable and the cam and cam follower are co-operable by limited rotation of the pin relative to the base.

9. An electrical plug as claimed in any one of the preceding claims in which the plug is substantially rectangular in plan view shape.

10. An electrical plug as claimed in any one of the preceding claims in which the inner ends of the pins are provided with terminals having thumb screws whereby conductors can be attached thereto.

1 An electrical plug as claimed in claim 10 in which the thumb screw of a terminal acts as the catch member thereof.

12. An electrical plug as claimed in claim 11 in which the thumb screws are of electrically insulating material and are colour coded for each specific terminal type.

13. An electrical plug as claimed in any one of claims 10 to 12 in which the cover has a thumb screw engaging formation formed thereon for tightening the thumb screws in use.

14. An electrical plug substantially as hereinbefore described with reference to and as illustrated in either of Figs. 1 and 2, or Fig. 3 or Fig. 4 of the accompanying drawings.