GB2144591A - Fitting an outlet box - Google Patents

Abstract

A circular outlet box 1 for electrical wiring fitting has a side wall which is at least part circular. The box is preferably completely circular or in the form of an oblong with circular ends, and is fitted into a corresponding recess 2 having a flat ledge 3 on which the base 4 of the box rests. The recess 2 may be cut in a wall using a tool comprising a pilot drill (23), a circular slot cutting part (27) and a flat-end portion cutting part (29, 30).

Description

SPECIFICATION Fitting an outlet box The invention relates to electrical wiring outlet boxes.

By the term "electrical wiring outlet box" or more simply "outlet box" - is meant an open-topped box usually of galvanised steel sheet which is set into a wall for electrical wiring fittings to be secured to. Generally outlet boxes are provided with a number of frangible discs which can be pushed out to allow entry to the box of wires set into the wall. Outlet boxes are normally secured initially by means of one or more screws engaging in one or more plugs in the wall behind each box. On plastering of the wall, the box becomes more firmly set in the wall by plaster filling any gaps around the side of the box.

Once the wall has been plastered, the required fitting, for example a socket or a switch, is attached to the outlet box by means of screws engaging in captive nuts attached in the outlet box to the inside of the sides thereof.

Setting of outlet boxes into the walls is a very time consuming process. Despite many advances in the tools available to electricians the recesses for outlet boxes are still in the main cut by hand with a cold chisel. The chief reason for this is that outlet boxes are square or rectangular.

The object of the present invention is to provide an improved method of fitting an outlet box.

According to the present invention there is provided a method of fitting an outlet box to a wall comprising cutting into the wall a circular recess having an, at least substantially, flat end portion and securing the box into the recess with its base resting against the said end portion.

Although the said end portion may extend across the full width of the hole, it preferably extends across only part of the width, for reasons explained below. Such a portion is conveniently cut in the form of a "flat ledge".

Since the material of the wall may be of uneven hardness, where the wall is of concrete blocks and hard brick for example, it is not realistic to expect that the ledge will be entirely flat. However, provided it is sufficiently flat to present a steady support for the outlet box, as opposed to an uneven support allowing rocking of the box, this will suffice.

Preferably the circular hole is cut with a tool having a central pilot drill. The resultant drilling may be used for receiving a plug and a screw for initial securing of the outlet box.

Although conventional, that is to say square or rectangular, outlet boxes may be used, these leave sizeable gaps adjacent the midpoints of the sides which require to be filled.

Such filling can be inconvenient, involving possible slippage and/or sinking of the filling plaster and an unsightly end result. Accordingly, a circular outlet box of the next aspect of the invention is preferably used.

According to the second aspect of the invention, there is provided a circular outlet box having a base for abutting the, at least substantially, flat end portion of a circular recess therefor and an at least part circular side wall provided with means for attachment to the box of an electrical wiring fitting.

Preferably the base portion of the box has a central securing-screw hole.

According to a third aspect of the invention there is provided a circular recess cutting tool for cutting a circular hole with an, at least substantially, flat end portion, comprising a pilot drill, a circular slot cutting part and a said-flat-end-portion cutting part, the arrangement being such that the pilot drill extends in front of the circular slot cutting part to act as a steady therefor and the circular slot cutting part extends in front of the flat cutting part to act as a steady therefor.

The circular slot cutting part may comprise a supporting tube having on its forward face as few as three hard cutting inserts, the minimum number for steady cutting support of the part itself. The said-flat-end-portion cutting part, hereinafter referred to as the "flat cutting part" may have only one cutting insert on a ring clamped outside the said support tube. Normally two or more cutting inserts will be provided.

Although the flat cutting part may be disposed within the circular slot cutting part, it is preferably provided outside this part. Such an arrangement leaves a stub of brick, or other wall material standing proud of the flat ledge.

This stub is readily removed with a hammer blow or at the most a few cold chisel blows.

Where the electrical fitting is a double fitting, for example a double socket, the circular outlet box may be modified to an oblong shape. The recess for such an outlet box may be cut by making two interconnecting circular recesses. A small amount of cutting out by hand will remain to be done.

To help understanding of the invention, a specific embodiment thereof will now be described with reference to the accompanying drawings in which: Figure 1 is a cross-sectional view through a circular outlet box of the invention set in a circular recess, Figure 2 is a plan view of the outlet box shown, in Fig. 1, Figure 3 is a plan view of a blank for the box of Figs. 1 and 2, on a smaller scale, Figure 4 is a plan view of an oblong/double box of the invention, Figure 5 is a cross-sectional view similar to Fig. 1 of the tool of the invention for cutting the recess of Fig. 1, and Figure 6 is an end view of the tool of Fig.

Referring first to Fig. 1, the outlet box 1 can be seen fitted into a circular recess 2 having a flat ledge 3 on which the base 4 of the outlet box rests. The recess 2 has a central pilot drill drilling 5 in which is accommodated a plug 6 having a screw 7 passing through a central aperture 8, see Fig. 2, and securing the base 4 to the ledge 3 and thus the box in the recess. The recess has a circular slot 9 surrounding a stub 10 of brick.

The stub originally extended to the surface 11 of the brickwork, see dotted outline 12, and has been knocked off at the level of the ledge 3.

The outlet box 1 has a number of frangible discs 13, which, to allow access for wiring (not shown), can be pushed out prior to fitting of the box. The discs are provided both in the base 4 and a circular side 14. The base 4 also has a number of extra screw-apertures 1 5 at a pitch circle to allow plugging into the ledge 3 if need be. The side 14 has a pair of diametrically oppositely arranged captive nuts 1 5 for securement of an electrical fitting (not shown).

The blank shown in Fig. 3 is such that the strip 1 6 can be rolled to form the side 14 and its ends flanged together as at 1 7, see circled detail in Fig. 2. The strip is provided with a number of lugs 1 8 which are bent under the base 4 when it has been bent in at its point of connection 1 9 to the strip rolled to form the circular side, in across the end of the circular side. The arrangement is such that in use the lugs 18 are captive between the base 4 and the ledge 3; hence the circular side 14 is held in position.

The oblong/double outlet box 20 of Fig. 4 is of similar construction to that of the single outlet box 1.

Turning now to Figs. 5 and 6, the circular recess cutting tool 21 has a mandrel 22 in a central bore of which a pilot drill 23 is locked by a grub screw 24. The mandrel has a threaded portion 25 with a shoulder 26 radially spaced from the pilot drill bore. A tube 27 is internally threaded to fit onto the threaded portion 25 and abut against the shoulder 26. The forward end of the tube 27 has four tungsten carbide cutting tips 28 set in it. The arrangement of the pilot drill 23 and the cutting tube 27,28 is such that the drill 23 extends in front of the tips 28 sufficiently far for the drill to steady initial cutting of the tips 28.

A ring 29 having a pair of cutting tips 30 fits over the tube 26 and is secured thereto with grub screws 31. The ring 29 and cutting tips 30 provide the flat-cutting part of the tool, and are set back on the tube 27 to allow the tube in the slot which it has cut to act as a steady for cutting the flat ledge 3.

The invention is not intended to be restricted to the details of the above described components. For instance the tube 27 and ring 29 could be a single integral member.

Alternatively, the tube and ring could both be a suitable length for them both to abut the mandrel. The box 1 could be formed with a plurality of joints around the side wall 14 and a corresponding plurality of connections 19.

The preferred material for the box is galvanised steel. However it is envisaged that it could be of aluminium, in which case it could be formed as an integral pressing, or again it could be a plastics material moulding.

Claims (22)

1. A circular outlet box having a base for abutting the, at least substantially, flat end portion of a circular recess therefor and an at least part circular side wall provided with means for attachment to the box of an electrical wiring fitting.

2. A circular outlet box as claimed in claim 1 wherein the base portion of the box has a securing screw hole central of the side wall curvature.

3. A circular outlet box as claimed in claim 1 or claim 2 wherein the box is formed from a sheet metal blank comprising a base portion and a strip-like side portion, the side portion being shaped into the at least part circular side wall, the portions being connected at a bend in the sheet metal.

4. A circular outlet box as claimed in claim 3 wherein the side portion is provided with lugs which are bent under the base.

5. A circular outlet box as claimed in claim 3 or claim 4 wherein the ends of the strip-like side portion are flanged together whereby the side wall is continuous.

6. A circular outlet box as claimed in any preceding claim wherein the box is of galvanized steel.

7. A circular outlet box as claimed in claim 1 or claim 2 wherein the base and side wall of the box are formed as an integral pressing.

8. A circular outlet box as claimed in claim 7 wherein the box is of aluminium.

9. A circular outlet box as claimed in claim 1 or claim 2 wherein the base and side wall are formed as a plastics material moulding.

10. A circular outlet box as claimed in any preceding claim wherein the side wall is circularly curved throughout its peripheral length.

11. A circular outlet box as claimed in any one of claims 1 to 9 wherein the side wall has two half circular sections interconnected by planar sections.

1 2. A method of fitting an outlet box to a wall comprising cutting into the wall a circular recess having an, at least substantially, flat end portion and securing the box into the recess with its base resting against the said end portion.

1 3. A method of fitting an outlet box as claimed in claim 12 wherein the, at least substantially, flat end portion is formed as a ledge.

14. A method of fitting an outlet box as claimed in claim 1 2 or claim 1 3 wherein a central drilling is made at the same time as the circular recess is cut.

1 5. A method of fitting an outlet box as claimed in claim 12, claim 1 3 or claim 14 wherein a stub is left during the cutting operation and the stub is knocked out after the cutting operation.

1 6. A circular recess cutting tool for cutting a circular hole with an, at least substantially, flat end portion, comprising a pilot drill, a circular slot cutting part and a said-flat-endportion cutting part, the arrangement being such that the pilot drill extends in front of the circular slot cutting part to act as a steady therefor and the circular slot cutting part extends in front of the flat cutting part to act as a steady therefor.

1 7. A circular recess cutting tool as claimed in claim 16 wherein the circular slot cutting part comprises a supporting tube having on its forward face at least three hard cutting inserts.

18. A circular recess cutting tool as claimed in claim 1 6 or claim 1 7 wherein the said-flat-end-portion cutting part has at least one cutting insert on a ring clamped outside the said support tube.

19. A circular recess cutting tool as claimed in claim 16, claim 1 7 or claim 18 wherein the said-flat-end-portion cutting part is provided outside the circular slot cutting part.

20. A circular outlet box substantially as hereinbefore described with reference to Figs.

1,2 and 3 or Fig. 4 of the accompanying drawings.

21. A method of fitting an outlet box to a wall substantially as hereinbefore described with reference to Fig. 1 of the accompanying drawings.

22. A circular recess cutting tool substantially as herein before described with reference to Figs. 4 and 5 of the accompanying drawings.