GB2138219A - Electric plugs - Google Patents

Abstract

An electric plug comprises a base member (6) and a cover member (8) adapted to be secured together by at least one screw, and which each comprise a recess-defining part (28) which, together define an aperture through which a cable may extend into the interior of the plug. The base member is provided with apertures (36,38,40) through which the pins of the plug extend from the interior thereof, the pins being provided in side faces thereof of smaller dimension, with apertures (17,19,21) and protrusions (37,39,41) are provided which deform to allow insertion of the pins and then extend into said apertures to retain the pins in position relative to the base. A terminal member (45-47 Fig. 6) e.g for a fuse, may be friction-fitted into an aperture in the base by means such as serrated tags (47). <IMAGE>

Description

SPECIFICATION Improvements relating to electric plugs A difficulty encount red in the use of a conventional electric plug is that the pins are normally held in position in the plug base by the plug cover, and when the cover has been removed, for example for rewiring, refusing or the like, there is a tendency for the pins to fall out from the base.

According to this invention there is provided an electric plug comprising a base member and a cover member which when the plug is assembled are secured together, the base member comprising apertures through which pins of the plug extend from the interior thereof, wherein the pins are provided in side faces thereof with at least one aperture into which a protrusion on the base member extends, the construction and arrangement being such that the protrusion may be readily deformed to permit movement of the pin into a desired position in the aperture, but which restrains subsequent movement of the plug pin from said desired position in at least one direction.

In this manner, on initial assembly of the plug, the pins may be inserted in the base member relatively easily, and are unlikely to fall from the base member on subsequent removal of the cover member from the base member, such as for example when the plug is being wired or rewired.

If desired, the construction and arrangement may be such that, assembly of the cover member and base member is effective to restrain or to further restrain deformation of the protrusion, in a manner which renders it less liable to removal from the aperture in the side face of the pin.

Thus, a face of the protrusion may be inclined, such as that face which, when the pin is being inserted through the aperture into its desired position, is engaged by the pin. In this manner, engagement of the protrusion by the pin, and deformation of the protrusion, is rendered more easy. However, forces on the pin when in its desired position, in the opposite direction (that is, tending to push the pin towards the interior of the plug) may be taken on planor, abutting faces of the protrusion and pin.

A further difficulty encountered in a conventional plug is the securing of a fuse terminal to the plug base. In particular, wheras the pins are inserted in the plug pin apertures, and one fuse terminal is carried by the live pin, the other fuse terminal (which is connected to wire-connecting means) is in general merely located in a recess, to be clamped in position by the cover when it is secured to the base. This renders said other fuse terminal particularly liable to separation from the plug base, and particularly when heavy duty wiring is connected to the connecting means, may be difficult to relocate and hold in said recess, whilst the cover is being manipulated into position relative to the base.

Thus preferably, the plug defined in the last preceding paragraph but four comprises a terminal member which is adapted to be inserted in an aperture or recess, part of or secured to the terminal member frictionally engaging the wall of the plug bounding said aperture or recess.

Thus, insertion of said part into the aperture or recess may involve deformation of either said part or recess, or of the wall bounding said aperture or recess. Said part may be resiliently deformable (for example be made of relatively soft plastics material), being compressed upon the insertion of the terminal member or said part into the aperture or recess.

Preferably however said part is provided by a fixing member of relatively rigid material secured to or extending from an underside of the terminal member, and which resiliently deforms the wall bounding the aperture or recess. Preferably, said fixing member is of metal, and comprises serrations.

Where the terminal member is a fuse terminal, conveniently it comprises a base plate, and two terminal tags extending therefrom at opposite ends, each of which is adapted to be inserted into an associated aperture or recess, to provide fixing members for the fuse terminal at opposite ends of the base member.

Such a construction allows the fuse terminal to be located in a desired position on the base plate of an electric plug relatively easily, resisting undesired movement of the fuse terminal from its desired position, yet allowing removal of the fuse terminal from the base member, should this become desired.

There will now be given detailed descriptions, to be read with reference to the accompanying drawings, of an electric plug which is a preferred embodiment of this invention, and which has been selected to illustrate the invention by way of example.

in the accompanying drawings: Figure 1 is an underneath plan view of the plug which is the preferred embodiment of this invention; Figure 2 is a sectional view, taken on the lines 2-2 of Figure 1; Figure 3 is a plan view of the base member of the plug, the coverthereof having been removed; Figure 4 is a sectional view, taken on the lines 4-4 of Figure 1; Figures 5 and 6 are views illustrating the securing of a fuse contact to the plug; and Figure 7 is a view illustrating a modified construction of the preferred embodiment.

The plug which is the preferred embodiment of this invention comprises a base 6 and a cover 8 adapted to be secured together by two screws 10, inserted through apertures 12 in the base and threadedly received in bores of the cover. The base and cover are moulded from plastics material, and the plug is provided with conventional live, neutral and earth terminals 16, 18 and 20 respectively.

At an end portion adjacent to the earth terminal, the base is provided with an exterior shoulder 22, and the cover is provided with an in-turned lip 24, adapted to engage behind the shoulder 22. On the other sides, the side wall of the cover extends around the side wall of the base.

Atthe end portion of the plug opposite to the earth terminal, the plug is provided with an aperture 26, through which electric cable conected to the plug pins extends. The aperture 26 is defined by recessdefining parts of the base and cover, specifically an interior wall portion 28 of the base 6, and a tongue 30 of the cover 8.

In the use of the plug which is the preferred embodiment of this invention, with the cover separated from the base, the conductive elements of the cable are connected to the three terminals in conventional manner, as shown in Figure 3.

The lip 24 of the cover is then engaged behind the shoulder 22, and the screws 10 inserted into the threaded bores of the cover, drawing the cover towards the base, and the tongue 30 into engagement with a cable located in the aperture 26, firmly gripping the cable, and in particular (by virtue of serrations 29 and 31 on the wall portion 28 and tongue 30, respectively) preventing withdrawal movement of the cable from the plug, and thereby removing strain from the connection of the conductive elements with the plug pins.

The distance of separation between the wall portion 28 and the tongue 30, as shown in full lines in Figure 2, represents the smallest diameter cable with which the plug is likely to be used: conversely, the position adopted by the front face of the cover, and the tongue 30, as shown in dotted lines in Figure 2, illustrates the largest diameter with which the plug may be used.

In the preferred embodiment above described, the size of the aperture 26 is decreased to grip the cable by tightening of the screws 10, which effects a pivotal or hinging movement between the base and cover about a.pivot axis defined generally by the line of contact between the lip 24 and the shoulder 22. In use, the screws 10 will be tightened to a degree which causes an adequate gripping being aided by resilient deformation ofthe cable.

Whereas the base and cover 6,8 are shown in Figure 1 as being moulded in two parts, if desired the base and cover may be produced as a single moulding, as is illustrated in Figure 7, the base and cover in such a construction being connected together by a web 55 of resilient plastics material.

Thus, from the position shown in Figure 7, the cover 8 may be hinged generally abouttheweb 55 into a position corresponding to that shown in Figure 2, with the lip 24 engaging beneath the shoulder 22.

Whereas as above described, the aperture 26 is closed by arcuate movement of the cover 8 relative to the base 6, if desired the cover may be mounted for rectilinear movement relative to the base, for example by the use of three screws arranged generally in the form of a triangle, or by a single centrally positioned screw.

As is shown in Figures 2 and 4, the three terminals 16, 18, and 20 each extend through a respective pin aperture 36, 38 and 40, having been inserted therein to the desired position, as shown, from the interior of the base.

Each of the pins is provided, extending into the pin through the face thereof the smallest dimension, with two apertures 17, 19 and 21, respectively: extending into each of the apertures 36, 38 and 40 are pairs of respective protrusions 37, 39 and 41.

Inner faces of these protrusions are angled, and by the pressing of the appropriate pin into the aperture, the wall portions bounding the aperture may be outwardly deformed, permitting passage of the pin through the aperture, until the protrusions 37, 39 or 41 enter the associated aperture 17, 19or21.

When in this position, forces acting on the pins, tending to move the pins towards the interior of the plug, are taken by abutting planar faces of the protrusion and pin, effectively preventing such movement. Forces acting on the pin, tending to move the pin further outwardly, are taken by abutment of an enlarged head of the pin with planar surfaces of the plug face, bounding the aperture.

If desired, the pin apertures may be constructed n a manner such that, the ability of the protrusions thereof for deformation is easier whilst the cover 8 is separated from the base, and an additional effect of the cover, when secured to the base, is to restrain or make more difficult such deformation of the protrusions as would be necessary for relative movement to take place between the plug pins and the base.

As can be seen in Figure 3, the live lead of the cable is connected to a terminal member 42 of a fuse terminal 43, the opposite fuse terminal 44 being connected to the live pin 16.

The fuse terminal 43 is formed from sheet metal as a pressing, and as can be seen from Figures 5 and 6 comprises a base plate 45, and two fuse-gripping arms 46 extending upwardly therefrom.

At each end of the base plate, there is provided a down-turned tag 47, each of which is provided on its outer side faces with serrations. By location of the two tags 47 in corresponding slots 48 of the base member, the fuse terminal 43 may be pressed into a desired position, and restrained against movement therefrom, by virtue of the frictional engagement between the tags 47 and the walls of the base bounding the slots 48.

By the use of this invention, a plug may be moulded of plastics material, such as nylon, having hardness characteristics appropriate to the provision of the abutments 37,39 and 41 to locate and secure the plug pins 16, 18 and 20, and appropriate to the deformation of a part at least of the plug base or the plug cover, securely to clamp or grip an electric cable, which has been connected to the plug pins.

Attention is drawn to our co-pending Application No.8100261 (2067365A).

Claims (1)

1. An electric plug comprising a base member and a cover member which when the plug is assembled are secured together, the base member comprising apertures through which pins of the plug extend from the interior thereof, wherein the pins are provided in side faces thereof with at least one aperture into which a protrusion on the base member extends, the construction and arrangement being such that the protrusion may readily be deformed to permit movement of the pin into a desired position in the aperture, but which restrains subsequent movement of the plug pin from said desired position in at least one direction.

2. An electric plug according to Claim 1 wherein the construction and arrangement is such that, assembly of the cover member and base member is effective to restrain or to further restrain deformation of the protrusion, in a manner which renders it less liable to removal from the aperture in the side face of the pin.

3. An electric plug according to Claim 2 wherein a face of the protrusion is inclined, said face being that which, when the pin is being inserted through the aperture into its desired position, is engaged by the pin, in a manner whereby engagement of the protrusion by the pin, and deformation of the protrusion, is rendered relatively easy.

4. An electric plug according to any one of the preceding claims in which a terminal member thereof is adapted to be inserted into an aperture or recess, part of or secured to the terminal member frictionally engaging the wall of the plug bounding said aperture or recess.

5. An electric plug according to Claim 4 wherein insertion of said part into the aperture or recess involves deformation of either said part or said aperture or recess, or of the wall bounding said aperture or recess.

6. An electric plug according to Claim 5 wherein said part is resiliently deformable, being compressed upon the insertion of the terminal member or said part into the aperture or recess.

7. An electric plug according to Claim 4 wherein said part is provided by a fixing member of relatively rigid material secured to or extending from an underside of the terminal member, and which resiliently deforms the wall bounding the aperture or recess.

8. An electric plug according to Claim 7 wherein said fixing member is of metal, and is provided with serrations.

9. An electric plug according to Claim 4 wherein the terminal member is a fuse terminal, comprising a base plate, and two terminal tags extending therefrom at opposite ends thereof, each of which is adapted to be inserted into an associated aperture or recess, to provide fixing members for the fuse terminal at opposite ends of the base member.

Amendments to the claims have been filed, and have the following effect: *(a) Claims 1,2 above have been deleted or textually amended.

*(b) New or textually amended claims have been filed as follows: New claim 1 filed *(c) Claims 3 to 9 above have been re-numbered as 2 to 8 and their appendancies corrected.

1. An electric plug comprising a base member and a cover member adapted to be secured together by at least one screw, the base and cover members each comprising a part which, when the base and cover members are secured together, define an aperture through which a cable may extend into the interior of the plug, the construction and arrangement being such that the size of the aperture may be varied to accommodate cable of differing sizes, by the tightening of the screw or screws, the base member comprising apertures into which pins of the plug may be inserted from the interior thereof, wherein the pins are provided in side faces thereof with at least one recess into which a protrusion on the base member extends, the construction and arrangement being such that the protrusion may readily be deformed to permit movement of the pin into a desired position in the aperture, but which restrains subsequent movement of the plug pin from said desired position in at least one direction.