GB2390760A

GB2390760A - Protective lid for an electrical back box

Info

Publication number: GB2390760A
Application number: GB0311741A
Authority: GB
Inventors: Graham Ian Ash
Original assignee: Individual
Current assignee: Individual
Priority date: 2002-05-21
Filing date: 2003-05-21
Publication date: 2004-01-14
Also published as: GB0211577D0; GB0311741D0

Abstract

A lid for fitting into the open top of an electrical back box, whilst the wall to which the back box is fixed is plastered, comprises a generally flat, square or rectangular member arranged to engage the screw fixing lugs of the back box. The lid may be formed at one end with a socket (provided by fingers 14) to receive one screw fixing lug, and/or with projections 16 for engaging into the corners of the back box as an interference fit. A spacer plate for a lid is also disclosed.

Description

Protective Lid for Electrical Back Box The present invention relates to a

protective lid for an electrical back box.

During the construction of many buildings, the major part of the electrical installation work is carried out before 5 the interior walls of the building are plastered. Thus metal back boxes for switches, sockets etc. are fixed in position on the walls, and the electrical cables are run to these back boxes, the ends of the cables being left coiled within the boxes for the switch and socket units to be fitted after the 10 plastering. Commonly, however, the plastering process leads to deposits of plaster entering the back boxes: this causes the electrician difficulties when subsequently fitting the electrical switch and socket units. Particular difficulties arise where the screw holes in the fixing lugs of the back 15 boxes become covered or filled with plaster, often leading to permanent damage to the screw threads when removing the plaster from them.

I have now devised a lid for fitting to an electrical back box for temporary protection whilst the plastering work 20 is being carried out.

In accordance with the present invention, there is provided a lid for an electrical back box, the lid comprising a generally flat, square or rectangular member for fitting within the open top of the back box, and arranged to be 25 retained in position by engagement with the screw fixing lugs of the back box.

Preferably the underside of the lid is arranged to rest on the upper sides of the screw fixing lugs of the back box.

Preferably one end of the lid is formed, on its 30 underside, to engage under the corresponding screw fixing lug of the back box. Preferably this end of the lid is formed with a socket to receive the respective lug of the back box. This socket may be formed by a pair of fingers of L-shape, which project outwardly from the underside of the lid, then inwardly

towards each other.

Preferably the opposite end of the lid is provided, on its underside, with one or more projections which engage the side and/or end walls of the back box as an interference fit.

5 Preferably two such projections are provided, arranged to engage into the corners between the side walls and end wall of the back box: preferably these projections have convex-curved outer edges or surfaces for engagement into the respective corners of the back box.

10 Preferably the lid is rectangular in shape and arranged for fitting into a rectangular (double) back box. Preferably the lid is arranged to be divided into two parts, one of which is arranged so that it can then be fitted into a square (single) back box in the same manner as the full lid fits into 15 the double back box.

Preferably the underside of the lid is chamfered around its edges, to ensure clearance for cables entering through any of the available ports in the side or end walls of the back box. 20 Also in accordance with the present invention, there is provided a lid for an electrical back box, the lid comprising a generally flat, square or rectangular member for fitting within the open top of the back box and arranged to rest on the screw fixing lugs provided at opposite ends of the back box, 25 the lid having at least one projection on its underside for urging against the side and/or end walls of the back box to retain, or help to retain, the lid in position.

Preferably the projection or projections are provided at one end only of the lid (but may be provided at both ends) 30 and are preferably positioned at the corners of the lid, between its side and end edges.

In use, and after the back boxes have been fixed in position on a wall and the electrical cables run to them, a lid in accordance with the present invention is fitted into 35 each box. Then the plastering work is carried out: during this

process, it will be appreciated that the lid provides an effective barrier against plaster entering the box and, in particular, effective protection for the screw fixing lugs of the box. After the wall or walls have been plastered, it is 5 a simple r.iatter for the electrician to remove the lid from each box and wire up the intended electrical switch or socket unit and fix into the back box.

In some cases, it is necessary for a relatively thick layer of plaster to be applied, with the result that the 10 finished surface of the plaster is substantially above the front level of the electrical back box. In accordance with the present invention, preferably the lid is arranged for one or more spacer plates to be fitted over it, effectively to build up its front surface to approximately the same level as the 15 eventual finished surface of the plaster. Preferably each spacer plate comprises a rectangular member slightly larger in length and width than the lid, so as to correspond approximately with the external length and width of the back box. Preferably the spacer plate engages over the lid by means 20 of one or more projections on the underside of the spacer plate engaging into corresponding apertures or recesses in the front of the lid. Preferably the front of the spacer plate is formed with corresponding recesses, so that a number of the spacer plates can be fitted one-over- another, in a stack, to build up 25 the required thickness.

Preferably the spacer plate is formed with a peripheral margin for seating on the front of the lid, and a raised portion which forms the front of the spacer plate. Preferably an upstanding rim is formed around the outer edge of the 30 peripheral margin, to overlie the top edges of the side and end walls of the back box. Preferably one or more well formations are provided in the spacer plate, the bottoms of these well formations fitting into the apertures in the underlying lid, or into the tops of the well formations of an underlying spacer 35 plate.

Also in accordance with the present invention, there is provided a spacer plate for fitting over a lid fitted into an electrical back box, the spacer plate having a peripheral margin for seating on the front surface of the lid, and a 5 raised portion which forms the front of said spacer plate. -

Preferably the spacer plate is rectangular in shape and -

arranged for use on a lid fitted to a double back box.

Preferably the spacer plate is arranged to be divided into two parts, one of which is arranged so that it can be used on a lid -

10 fitted to a single back box.

Embodiments of the present invention will now be described by way of examples only and with reference to the accompanying drawings, in which: FIGURE 1 is a longitudinal section through an 15 electrical back box fitted with a lid in accordance with the present invention, and also showing a spacer plate fitted to the front of the lid; FIGURE 2 is a similar section to Figure 1, but showing a second spacer plate fitted to the front of the first; 20 FIGURE 3 is a cross-secticn through the electrical back box, lid and spacer plates shown in Figure 2;: FIGURE 4 is an isometric view of the lid from its front; FIGURE 5 is a side view of the lid; 25 FIGURE 6 is an isometric view of the lid from its underside; and FIGURE 7 is an underside view of the lid.: Referring initially to Figures 1 and 2 of the drawings, there is shown an electrical back box B of conventional 30 construction, formed from a blank of sheet steel and having -

a bottom (not shown), upstanding side walls S and end walls E, -

and an open top. A number of circular press-out pieces (not shown) are formed in the side, end and bottom walls of the box B. arranged for any one or more of these press-out pieces to 35 be removed to provide ports for the entry of electrical cables

into the interior space of the box. Lugs L1, L2 are provided on the opposite end walls E of the box, projecting inwardly adjacent the top of the box and formed with threaded holes to receive the fixing screws of electrical switch or socket units 5 to be fitted into the box. Typically, one of the lugs L1, L2 is pressed out from its end wall of the box, whilst the other lug comprises a separate piece adjustably mounted to the opposite end wall of the box.

Figures 1 and 2 show a lid 1O, in accordance with the 10 present invention, fitted across the open top of the back box B. As more clearly shown in Figures 4 to 7, the lid 10 comprises a generally flat or planar and rectangular member of plastics material, which is received within the box B so that its outer or front surface is more or less flush with the top 15 edges of the side and end walls of the box: further, the length and width of the lid 10 are only slightly smaller than the internal length and width of the box B. so that the lid substantially fully closes the top of the box.

The underside of the lid 10 is chamfered around all 20 four edges, as shown at 11, in order to ensure clearance for cables entering through any of the ports available in the side or end walls of the back box B. The underside of the lid 10 is also formed, at its opposite ends C, D and centrally between its opposite edges, with seats 12, 13 for resting on the tops 25 of the lugs L1, L2 of the box B. At one end C, the underside of the lid 10 is formed with a pair of L-shaped fingers 14 which project downwardly and then inwardly towards each other across the width of the lid, thus providing a formation which defines a slot to receive the respective lug, e.g. lug L1, of 30 the box B. At the opposite end D of the lid, tangs 16 project from its underside, at its corners: each tang 16 is generally planar and set at 45 to the end and side edges of the lid, and its outer edge is convex-curved and projects beyond the corner of the main, planar portion of the lid itself.

35 In use, the lid 10 is inserted into the back box B with

its end C first and at an inclined angle, to engage its fingers 14 around and under the respective lug L1: the lug L1 is thus received in the slot defined by the fingers 14 and respective seat 12 on the underside of the lid 10. Then the opposite end 5 D of the lid is pushed into the box B until the respective seat 13 engages or rests on the lug L2: at the same time, the tangs 16 engage into the corners between the side walls and respective end wall of the box, so providing a bias fit to ensure that the lid remains in position.

10 It will be noted that the lid 10 is formed with a line of weakness 17 extending across its underside, mid-way between its opposite ends C, D: the underside of the lid is chamfered either side of this line 17, as shown at lla, lib. The lid 10 can accordingly be broken into two parts 10a, 10b so that the 15 part 10a can then be fitted into a square (or single) back box whilst part 10b is discarded. It will be noted that a seat 12a and fingers 14a are provided on the underside of the part 10a, at the line 17 and corresponding to the seat 12 and fingers 14 described above.

20 The lid 10 is formed with a pair of apertures 18, for the user to insert his fingers when fitting it into or removing it from the back box B. Once fitted, the lid provides effective protection against the entry of any plaster into the box, during the 25 plastering process: it also provides effective protection for the screw fixing lugs L1, L2 of the box B. After the plastering, the electrician removes the lid to form the box B and wires up the required electrical switch or power socket and fixes it into the box B. 30 Figure 1 shows a single spacer plate 20 fitted to the front of the lid 10, where the layer of plaster to be applied is relatively thick, and so the front of the spacer plate 20 is more or less flush with the finished surface of the plaster.

Figures 2 and 3 show two spacer plates 20 fitted one-over-the 35 other, where the layer of plaster to be applied is even

thicker: in general, any desired number of spacer plates may be stacked in the same manner over the lid 10.

Each spacer plate 20 is preferably formed of plastics material by a vacuum forming. Along its side and end edges, 5 the spacer plate 20 is formed with an inwardly-directed skirt 21, then an outwardly-directed margin 22 which seats on the front surface of the lid 10. An inverted V- section rim 23 extends from the outer edge of the margin 22, to overlie the top edges of the side and end walls of the back box B. The 10 spacer plate 20 is also formed with a pair of walls 24, 25 which have tapering peripheral walls and flat bottoms, and correspond in cross-sectional shape and size to the apertures 18 in the lid 10: the wells 24, 25 project beyond the underside of the peripheral margin 22 of the spacer plate, in 15 order to engage, as an interference fit, into the apertures 18 of the lid lO; it will be noted that the apertures 18 of the lid are formed with peripheral rims of complementarily tapered form. It will also be noted, from Figures 2 and 3, that the second spacer plate fits onto the first by means of the bottoms 20 of its well-formations 24, 25 engaging into the tops of the corresponding well-forations of the first spacer plate.

Each spacer plate 20 is arranged to be separated, across a transverse line 26, into two parts 20a, 20b, the part 2Ga then being used on a square (or single) back box.

25 Adjacent this dividing line 26, the part 2Ga is formed with a skirt 21a, margin 22a and rim 23a, corresponding to the opposite end of the part 20b which is discarded.

Claims

Claims

1) A lid for an electrical black box, the lid comprising a generally flat, square or rectangular member for fitting within the open top of the back box, and arranged to be 5 retained in position by engagement with the screw fixing lugs of the back box.

2) A lid as claimed in claim 1, in which the underside thereof is arranged to rest on the upper sides of the screw fixing lugs of the back box.

10 3) A lid as claimed in claim 1 or 2, having one end formed, on its underside, to engage under the corresponding screw fixing lug of the back box.

4) A lid as claimed in claim 3, in which said one end thereof is formed with a socket to receive the respective screw 15 fixing lug of the back box.

5) A lid as claimed in claim 4, in which said socket is formed by a pair of L-shaped fingers which project inwardly from the underside of the lid, then outwardly towards each other. 20 6) A lid as claimed in any one of claims 3 to 5, having its opposite end provided, on its underside, with one or more projections for engaging the side and/or end walls of the back box as an interference fit.

7) A lid as claimed in claim 6, provided with two said 25 projections, arranged to engage into the corners between the side walls and end wall of the back box.

8) A lid as claimed in any preceding claim, which is rectangular in shape for fitting into a double, rectangular back box, and is arranged to be divided into two parts, one of which is arranged to fit into a single, square back box.

5 9) A lid as claimed in any preceding claim, the underside of which is chamfered around its peripheral edges.

10) A lid for an electrical back box, the lid comprising a generally flat, square or rectangular member for fitting within the open top of the back box and arranged to rest on the screw 10 fixing lugs provided at opposite ends of the back box, the lid having at least one projection on its underside for urging against the side and/or end walls of the back box to retain or help retain the lid position.

11) A lid as claimed in claim lo, in which the underside 15 thereof is provided with a pair of said projections being positioned at the corners of the lid, between its side and end edges. 12) A spacer plate for fitting over a lid fitted into an electrical back box, the spacer plate having a peripheral 20 margin For seating on the front surface of the lid, and a raised portion which forms the front of the spacer plate.

13) A spacer plate as claimed in claim 12, which is rectangular in shape for use on a lid fitted into a double, rectangular back box, and is arranged to be divided into two 25 parts, one of which is arranged for use on a lid fitted into a single, square back box.

14) A lid for an electrical back box, the lid being substantially as herein described with reference to the

accompanying drawings.

15) A spacer plate for fitting over a lid fitted into an electrical back box, the spacer plate being substantially as herein described with reference to Figures 1 to 3 of the 5 accompanying drawings.