GB2393854A

GB2393854A - Electrical back box

Info

Publication number: GB2393854A
Application number: GB0223122A
Authority: GB
Inventors: Simon Ticehurst
Original assignee: LARKIN INSTALLATIONS Ltd
Current assignee: LARKIN INSTALLATIONS Ltd
Priority date: 2002-10-05
Filing date: 2002-10-05
Publication date: 2004-04-07
Also published as: GB0223122D0

Abstract

An electrical back box 10 comprises a rear housing 12 and a front lip 14. The rear housing 12 includes a main opening 20 and a housing wall 18 which defines the main opening 20. The housing wall 18 has first and second opposing semi-circular wall portions 22, and the front lip 14 is of quadrilateral or substantially quadrilateral shape and extends around the main opening 20 of the rear housing 12. A method of fitting an electrical back box to a structure, such as a wall, is also provided.

Description

I2LECTRICAL BACK T30X

The present invention relates to an electrical back box for an electrical outlet socket or light switch.

Electrical back boxes typically come in sizes of between one and three gang, with one and two gang boxes being the most common, especially for domestic purposes. JO A structure, usually being a wall, into which the back box is to be recessed can be of particularly hard or awkward material. In this case, a known method is to cut an Outline of a knowntype of back box into the face of the wall using an abrasive disc fitted to an angle grinder or an electric drill fitted with a masonry bit. The material within the outline is then either removed completely by hand, for example using a 15 hammer and masonry chisel, or the drill is first used to drill out as much of the surplus material as possible within the outline before then using the hammer and chisel to finish the job.

However, these methods tend to be inaccurate, leading to the fittings not being 20 level and the back box not lying flush with the t'ace of the wall. 'lithe use of an electric drill with masonry bit to drill out the material within the border takes a long time, and the use of an angle grinder creates a tremendous amount of widely distributed dust.

I'he present invention seeks to provide a solution to these problems.

According to a first aspect of the present inventions there is provided an electrical back box comprising a rear housing and a front lip, the rear housing including a main opening and a housing wall which defines the main opening, the housing wall having first and second opposing semi- circular wall portions' and the 5 front lip being of quadrilateral or substantially quadrilateral shape and extending around the main opening of the rear housing.

Preferable and/or optional features of the first aspect of the invention are set forth in claims 2 to 12, inclusive.

According to a second aspect of the present invention, there is provided a method of fitting an electrical back box, as claimed in any one of the preceding claims, to a structure, the method comprising the steps of: a) determining the position on the structure at which the said back box is to be 15 inserted; b) using a core cutter drill bit having a radius equal to or greater than the radius of the semi-circular wall portions of the back box to forth a recess in the structure; and c) shaping The recess so that the back box can tit flush in the recess.

Preferable and/or optional features of the second aspect of the invention are set t'orth in claim 14 and claim 15.

I'he invention will now be described. by way of example. with reference to the

accompanying drawings, wherein: Figure I is a schematic plan view of an electrical back box, in accordance with the first aspect or the invention, s Figure 2 is a schematic cross-sectional side view, along line 1-A in [figure 1, showing the back box when fitted, and Figures 3 to 6 show, in plan, a method of installation of the electrical back 10 box, in accordance with the second aspect of the invention.

Referring initially to Figure 1, there is shown a two gang electrical back box 10 which comprises a rear housing 12 and a front lip 14. The back box 10 is typically moulded from plastics, but may be formed from any suitable material, such as zinc-

15 plated steel for example.

The rear housing 12 has a base]6, a housing wall 18 formed around the perimeter of the base 16, and a main opening 20 opposite the base 16 which is defined by the housing wall 18.

The housing wall 18 is of non-circular cylindrical or substantially cylindrical form, and comprises first and second opposing semi-circular wall portions 22. and third and fourth opposing wall portions 24 which are integrally formed with. and interposed between, the first and second semi-circular wail portions 22. The first and

second semi-circular wall portions 22 have a radius of, or substantially of, 39 milihnetres. The third and fourth wall portions 24 are planar or substantially planar so that a cross-section taken parallel or substantially parallel to the base 16 of the housing wall 18 is of oval or substantially oval shape.

s The housing wall 18 includes one or more openings (not shown) to enable an electrical power cable (not shown) to be threadably inserted into the back box 10.

The front lip 14 is continuous and integrally moulded to the housing wall 18, 10 so that it extends around the main opening 20. As can be seen in Figure 2, the front lip 14 also projects in a direction which is away from the rear housing 12 and overhangs the outer surface 26 of the housing wall 18. The outer surface 28 of the front lip 14 defines a rectangular or substantially rectangular shape to correspond to the shape of a standard two gang electrical socket fitting or light switch fitting (neither 15 of which are shown).

The back box 10 also comprises a pair of Axing lugs 30 which engage respective fixing devices (not shown) by which the electrical socket titling or light switch fitting are held to the back box 10.

The base 16 of the rear housing 12 has two fixing holes 32, each of which can receive a fixing device Ior example a screw 34, tor holding the back box 10 when positioned in or on a wall 36 or other structure.

Referring now to Figures 3 to 6' the mounting of the electrical back box 10 will now be described, by way of example. with reference to fitment in the wall 36.

However' it will be understood that the electrical back box 10 could be fitted in a similar mamier in any suitable structure.

A template 38 of the back box 10 (Figure 3)is first utilised as a cutting guide.

The template 38 has two openings 4() which correspond to the taxing holes 32 in the base 16 of the rear housing 12. The template 38 is held flat against the wall 36 in the vicinity of an electrical power cable (not shown) and at a location in which the back 10 box 10 is to be recessed. Once the template 38 is satisfactorily oriented with the aid of a spirit level 42, two pilot holes 44 are drilled, typically using a masonry bit, into the wall 36 through the two openings 40.

A core cutter drill bit (not shown) having a radius equal to the radius of the 15 first and second semi-circular wall portions 22 of the of the rear housing 12 is used to drill into the wall 36, coaxially with the pilot holes 44, to a depth which corresponds to the depth of the rear housing 12 and the height of the front lip 14 when combined.

Typically, the core cutter will have a 78 millimetre diameter.

20 The two 'cores' formed by the core cutter are then removed from the wall 36 by a tubular removal tool (not shown), leaving a 'figure-of-8' shaped recess 46, as shown in Figure 4.

Inwardly projecting ridges 48 are then removed using any suitable tool. such

as a masonry chisel (not shown), so that the shape of the recess 46' matches or substantially matches the shape of the rear housing 12. See Figure 5.

To enable the back box 10 to fit flush in the recess 46' a portion of the recess -S 46' adjacent to the Iront surface of the wall 36 is shaped, typically with a masonry chisel, to correspond to the front lip 14 of the back box 10. Typically, this involves only the remova] of plasterwork (36' in Figure 2) covering the wall 36.

The electrical power cable is then threadably inserted into the rear housing 12 10 through a convenient one of the housing wa]] openings, and the bacl; box]0 is positioned in the recess 46" so that the free edge 50 of the front lip 14 lies flush or substantially flush with the front surface of the wall 36. See Figures 2 and 6.

Wall plugs 52 (Figure 2) are inserted into the pilot holes 44 formed in the wall 15 36, and suitable threaded fixing devices 34, are inserted through the fixing holes 32 in the base 16 of the rear housing 12 and engaged with the wall plugs 52.

An electrical fitting, such as an electrical outlet socket or light switch. can then be electrically connected to the power cable and t; astened over the back box]O by 20 engagement with the fixing lugs 30 of the back box 10.

Although it is preferable that the front lip is continuous, it could be castellatcd.

The base ot the rear housing could also be dispensed with. A second set of

inwardly projecting fixing lugs, for example, could be fonned on the bottom edge of the housing wall instead. In this case' a suitable set of fixing holes would have to be drilled into the wall in addition to the pilot holes.

5 In the case where only a one gang electrical back box is required. the third and fourth wall portions are dispensed with, and the first and second seni-circular wall portions are simply integrally formed with each other, thereby forming a circular or substantially circular cross-section taken parallel to the rear housing base. Due to this foreshortening, the front lip defines a square or substantially square shape.

The housing base only has one fixing hole. Consequently, during installation, only one corresponding pilot hole is drilled.

Less shaping of the recess formed by the core cutter drill bit is required due to 15 the circular cross-section formed by the semi-circular wall portions.

The single gang electrical back box is advantageous due to the fact that angular adjustment of the back box, when it is fitted, is relatively straightforward, especially when the front lip is not recessed.

Although a core cutter of radius equal to the radius of the semi-circular wall portions is used, a core cutter of slightly larger radius could be used. This would provide for some lateral, transverse and angular adjustment of the back box when inserted into the recess.

Furthermore, although the front lip has been described as defining a solely quadrilateral or substantially quadrilateral shape, the shape of the front lip is largely dependent on the shape of the electrical front fitting to be used.

5 It is thus possible to provide an electrical hack box which can be t'itted Marc easily and more quickly than a conventional type of back box.

The embodiments described above are given by way of example only, and modifications will be apparent to persons skilled in the art without departing from the 10 scope of the invention as defined by the appended claims.

Claims

1. An electrical back box comprising a rear housing and a front lip, the rear housing including a main opening and a housing wall which defines the main opening.

5 the housing wall having first and second opposing semi-circular wall portions, and the front lip being of quadrilateral or substantially quadrilateral shape and extending around the main opening of the rear housing.

2. An electrical back box as claimed in claim 1, wherein the front lip is integrally !0 termed with the rear housing

3. An electrical back box as claimed in claim 1 or claim 2. wherein the front lip is continuous.

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4. An electrical back box as claimed in any one of the preceding claims, wherein the front lip projects away from the rear housing.

5. An electrical back box as claimed in any one of the preceding claims, wherein the housing wall is cylindrical or substantially cylindrical.

6. An electrical back box as claimed in any one of the preceding claims, wherein the housing wall includes third and t'ourth opposing wall portions which are integrally formed with the first and second semi- circular wall portions so that the housing wall det'incs an oval or substantially oval cross-section.

7 An electrical back box as claimed in any one of claims I to 5. wherein the first and second semi-circular wall portions are integrally tonged with each other so that the housing wall defines a circular or substantially circular cross-section.

5

8. An electrical back box as claimed in any one of the preceding claims' wherein the front lip defines a rectangular or substantially rectangular shape.

9. An electrical back box as claimed in any one of claims I to 7. wherein the front lip defines a square or substantially square shape.

10. An electrical back box as claimed in any one of the preceding claims, wherein the back box further comprises a pair of fixing lugs for engaging an electrical outlet letting and/or light switch fitting.

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11. An electrical back box as claimed in any one of the preceding claims' wherein the rear housing includes a base integrally}'ormed with the housing wall.

12. An electrical back box as claimed in any one of the preceding claims, wherein the housing base has one or more fixing holes for fixing the back box to a surface 20 when using a fixing device.

13. A method of fitting an electrical back box, as claimed in any one of the preceding claims, to a structure' the method comprising the steps of:

a) determining the position on the structure at which the said back box is to be inserted; by using a core cutter drill bit having a radius equal to or greater than the 5 radius of the semi-circular wall portions of the back box to form a recess in the structure; and c) shaping the recess so that the back box can fit flush in the recess.

10

14. A method as claimed in claim 13, further comprising a step (d), between the steps (a) and (b), of using a template as a cutting guide.

15. A method as claimed in any one of claim 13 or claim 14, further comprising a step (e) subsequent to step (c) of engaging the back box with the structure using one or IS more threaded-fastening devices.

16. An electrical back box substantially as hereinbefore described with reference to Figures 1 and 2 of the accompanying drawings.

20

17. A method of fitting auk electrical back box substantially as hereinbefore described with reference to Figures 3 to 6 of the accompanying drawings.