GB2082851A - Electric plugs - Google Patents

Abstract

An electric plug which may be non-rewirable is provided with a fuse holder 2 to hold a fuse 1 within the plug body, the holder and fuse being withdrawable through an aperture in the outside wall of the body to allow replacement of the fuse, the fuse holder being permanently attached to the body. The fuse holder may be attached by (a) a strip of flexible material 8, (b) a cut-out wall portion forming a hinge (Fig. 3), (c) an inner flange which is wider than the aperture (Figs. 6-10), or (d) prongs having flanges engaging the inside wall surface (Figs. 11 and 12). <IMAGE>

Description

SPECIFICATION Electric plugs This invention relates to electric plugs, particularly but not exclusively to plugs of the nonrewirable type.

Non-rewirable plugs generally cannot be opened to gain access to the wiring inside and when the plug contains a fuse it is therefore necessary to provide means for removing the fuse accessible from the outside of the plug. This may be achieved by mounting the fuse in a fuse holder which fits removably in an opening in the body of the plug. The outside surface of the fuse holder is normally flush with the plug surface when the fuse holder is inserted in the opening.

Different designs of plugs may have fuse holders which seem identical at first glance but in fact have slightly different dimensions. The insertion in a plug of a fuse holder of slightly the wrong size can produce a poor electric contact between the fuse and the components in the plug which it engages, giving a risk of overheating and electric failure of the plug.

According to the present invention there is provided an electric plug provided with a fuse holder to hold a fuse within the body of the plug, the holder together with a fuse held thereby being withdrawable through an aperture in an outside wall of the body to allow replacement of the fuse in the holder, the fuse holder being permanently attached to the body.

As the plug body and fuse holders are permanently attached there is no risk of an incorrect holder being inserted in the aperture and also no risk of the fuse holder being lost after withdrawal. The plug may be of the rewirable type (in which the plug may be dismantled to allow access to the wiring inside) or it may be nonrewirable (i.e. the plug body is permanently sealed).

The fuse holder may be attached to the body by a strip of flexible material which occupies a groove in the outer surface of the wall when the fuse holder is positioned within the body and the strip may fit into the groove in such a manner that a substantially flat wall surface is thereby produced.

One end of the strip may be attached to the fuse holder and the other attached to a cross-piece irremovably secured to the body.

In another arrangement the fuse holder is attached to the body by a cut-out wall portion forming a hinge which may be at an edge of the wall. In another arrangement the fuse holder has an inner flange of greater width than the aperture, preferably in two orthogonal directions, to abut the inside surface of the wall when the fuse holder is withdrawn, thus preventing complete removal.

In yet another arrangement the fuse holder comprises prongs extending into the body of the plug through the aperture, the prongs having outwardly extending flanges to abut the inside surface of the wall adjacent the aperture when the fuse holder is withdrawn. The prongs may be of resilient material so that the fuse holder may be fitted to the plug body by bending the prongs inwardly and passing them through the aperture.

Embodiments of the invention will be described by way of example with reference to the accompanying drawings in which: Figure 1 is a perspective view of a plug with a fuse holder according to one embodiment, Figure 2 is a plan view of the plug of Figure 1 with the fuse holder inserted, Figure 3 is a perspective view of a plug with a fuse holder according to another embodiment, Figure 4 is a perspective view of a plug with fuse holder according to another embodiment, Figure 5 is a plan view of the plug of Figure 4 with the fuse holder inserted, Figure 6 is a section of a plug with fuse holder according to another embodiment, Figure 7 is a perspective view of the fuse holder of the plug of Figure 6, Figures 8 to 10 show schematically a manner of assembling the plug with the fuse holder of Figure 6, Figures 11 and 12 show a fuse holder with a plug according to another embodiment.

Referring to Figure 1, a non-rewirable plug of the square-pin 13-amp type is provided with a fuse 1 removably held in a fuse holder 2 made of nylon or other plastics material. The fuse holder fits into an opening 3 in the base of the plug body as shown in Figure 2 whereupon the metal-coated ends 4 of the fuse are clamped between the generally U-shaped clips 5 within the plug. The clips are connected within the plug to one of the power-carrying pins and lead attached to the plug in known manner so that the fuse completes the power circuit. The prongs of the clips 5 are shaped so that a positive force has to be exerted on the fuse holder to free the fuse from the clips. When the fuse holder is inserted in the opening 3 its outside surface is substantially flush with the base 6 of the plug body.

The base 6 is provided with a groove 7 and the fuse holder 2 is connected to the plug by a thin flexible strip of plastics material 8 one end of which is connected to a cross-piece 9 also of plastics material. The cross-piece 9 is irremovably secured in the body of the base 6 at an end of the groove 7 so that the fuse holder 2 is permanently attached to the plug body.

The strip 8 is of a thickness and length such that when the fuse holder is inserted in the opening 3 as shown in Figure 2 the strip is contained in the groove 7 so that the base 6 has an effectively flat surface and the plug can be applied to a socket in the normal way.

As shown in Figure 2 the flat "outside" surface of the fuse holder 2 is provided with a square hole 14 into which a screwdriver or like implement can be inserted to remove the fuse holder from the opening 3 by leverage. This hole may pass completely through the flat portion of the fuse holder so that part of the fuse 1 is visible from the outside of the plug when the fuse holder is in place. The colour code or other marking indicating the rating of the fuse can thus be read without removing the fuse holder from the opening 3.

The plug shown in Figure 3 is identical to that shown in Figures 1 and 2 except that a different means is used for attaching the fuse holder to the body of the plug. In this instance the fuse holder 2 is attached to the body 10 of the plug by a cut-out portion 11 of the wall of the plug body of plastics material which is thin enough to be bent in the manner shown in Figure 3 without fracture.

Portion 11 forms a hinge about which the fuse holder may pivot between the position shown to its operating position within the opening 3. The flat part of the fuse holder has a shoulder 12 which engages a corresponding shoulder 13 within the plug body so that when the fuse holder is in place within the opening 3 it cannot be displaced sideways from the opening.

Figures 4 and 5 show a square-pin plug of known type of a different internal design from that of Figures 1 to 3. In this case the fuse is mounted in the plug in a different position but it is contained in an opening 3 engaging clips 5 in the same manner as in the embodiment of Figure The fuse holder 2 is hinged to the body of the plug by portion 11 in the same manner as in the plug of Figure 3 and cooperating shoulders 1 2 and 13 again prevent sideways movement of the fuse holder when it is positioned in the opening 3. In addition, as shown in Figure 5 the fuse holder has a sideways projecting shoulder 1 5 which fits into a corresponding recess in the base of the plug to prevent sliding movement of the holder.

In the embodiment of Figures 6 and 7 the fuse carrier 2 comprises a U-shaped portion 1 6 to hold the fuse 1, attached to a flat outer portion 1 7 which is flush with the plug base when the fuse is within the plug and a flat inner portion 18 of greater size than the U-shaped portion so that a flange 1 9 overhangs the U-shaped portion around three sides and the width of the inner portion 1 8 in two perpendicular directions is greater than the width of the opening in the plug which receives the fuse holder. The fuse holder can therefore slide in and out of the opening so that the fuse can be removed but abutment of the flange 19 with the inner surface of the plug base prevents the fuse cover being removed completely.

Figures 8 to 10 show how a plug of this type may be assembled. The body of the plug 20 receives a slide cover 21 provided with a projecting shoulder 22 intended to abut the flange 1 9 of the portion 1 8 of the fuse holder. The body 20 has shoulders 23 arranged to engage corners 24 of portion 1 8 (Figure 7). Before the slide cover is fitted the fuse holder is inserted in the opening at an angle as indicated in Figure 8 so that shoulders 23 engage corners 24. The fuse holder is then tilted to the position shown in Figure 9 and the slide cover 21 is applied so that its shoulder 22 engages the flange 1 9 preventing the fuse holder from being removed from the plug.

However the fuse holder can be slid between the open position shown in Figure 9 at which a fuse may be inserted or removed from between the prongs of U-shaped portion 1 6 and a closed position shown in Figure 10 in which an inserted fuse is within the plug. The plug is provided with clips, as in the preceding embodiments, to engage the fuse and provide electric contact with it.

Figures 11 and 12 show another type of fuse holder which is slidable in and out of the plug without being detachable. The holder is of resilient plastics material, generally U-shaped and the ends of the prongs 25 of the U have outwardly projecting flanges 26 to engage the inside surface 27 of the base 6. The cross-piece of the U has outwardly projecting flanges 28 dimensioned to engage shoulders 29 on the outward surface of the base.

The fuse holder may be assembled with the plug by pressing the prongs together and inserting them in the opening. After insertion the prongs can spring apart so that flanges 26 can abut surface 27 and prevent removal of the fuse holder.

The fuse holder can however slide between the positions shown in Figures 11 and 12 so that the fuse may be replaced. Flanges 28 abutting shoulders 29 determine the maximum extent of insertion of the fuse holder. The interior of the plug is again provided with clips to engage the fuse.

In all these embodiments the fuse holder may contain a hole 14 to allow inspection of the fuse and facilitate removal of the fuse holder from the plug interior. The base may also be provided with a notch such as notch 30 shown in Figures 8 to 12 to receive a screwdriver blade or the like so that the fuse holder may be levered out of the opening.

In all the plugs described above the opening for the fuse in on the same side of the plug as the pins so that the fuse cannot be removed while the plug is inserted in a socket.

Claims (14)

1. An electric plug provided with a fuse holder to hold a fuse within the body of the plug, the holder together with a fuse held thereby being withdrawable through an aperture in an outside wall of the body to allow replacement of the fuse in the holder, the fuse holder being permanently attached to the body.

2. A plug according to Claim 1, in which the fuse holder has an outer surface substantially flush with the outer surface of said wall when positioned within the body of the plug.

3. A plug according to Claim 1 or 2. in which the fuse holder is attached to the body by a strip of flexible material which occupies a groove in the outer surface of said wall when the fuse holder is positioned within the body of the plug.

4. A plug according to Claim 3, in which the strip and groove are such that the strip within the groove forms a surface substantially flush with the.

outer surface of said wali.

5. A plug according to Claim 3 or 4, in which one end of the strip is attached to the fuse holder and the other end is attached to a cross-piece irremovably secured to the body of the plug.

6. A plug according to Claim 1 or 2, in which the fuse holder is attached to the body of the plug by a cut-out portion of said wall of the body forming a hinge.

7. A plug according to Claim 6, in which said hinge is located at an edge of said wall.

8. A plug according to any preceding claim, in which the fuse holder has a shoulder arranged to abut a corresponding shoulder in the aperture to prevent movement of the fuse holder in a direction parallel to said wall.

9. A plug according to Claim 1 or 2, in which the fuse holder comprises an inner flange of greater width than the aperture to abut the inside surface of the wall adjacent the aperture when the fuse holder is withdrawn through the aperture.

10. A plug according to Claim 9, in which the inner flange is of greater width than the aperture in two orthogonal dimensions.

11. A plug according to Claim 9, in which the fuse holder comprises prongs extending into the body of the plug, the prongs having flanges extending outwardly of the fuse holder to abut the inside surface of the wall adjacent the aperture when the fuse holder is withdrawn through the aperture.

12. A plug according to Claim 11, in which the prongs are of resilient material so that the fuse holder may be fitted to the plug body by bending the prongs inwardly and passing them through the aperture.

13. A plug according to any preceding claim, in which the fuse holder is provided with a hole to render the fuse visible when the fuse is within the body of the plug.

14. A plug according to any preceding claim, provided with a notch in the body or the fuse holder to allow withdrawal of the fuse holder by leverage.

1 5. A plug according to any preceding claim, provided with a pair of spring clips to engage respective ends of the fuse and provide electrical contact therewith when the fuse is held by the fuse holder within the body.

1 6. A plug according to any preceding claim, which is non-rewirable.

1 7. An electric plug, substantially as hereinbefore described with reference to Figures 1 and 2, Figure 3, Figures 4 and 5, Figures 6 to 10, or Figures 11 and 12 of the accompanying drawings.