GB2162381A - Electrical connection box - Google Patents

Abstract

A generally square electrical connection box has a base 2 and sides 3 which are shaped to provide a threaded circular aperture 6. A threaded cover 10 screws onto the box and over the aperture 6. <IMAGE>

Description

SPECIFICATION Electrical connection box This invention relates to an electrical connection box for use in the connection for electrical cables, one to the other or, alternatively, electrical wires passing through conduit tubes or the like.

Electrical connection boxes are generally rectangular in shape and have a lid which can be sealingly secured over the access opening of the box by means of a plurality of screws.

The securing of such screws is not only time consuming but also leads to other wastages of time and money in that screws become lost, thereby resulting in time being lost in obtaining replacement screws or, alternatively, the screws are simply not installed which creates a hazard.

Electrical connection boxes of the type under consideration are often made to a rectangular shape so that the flat sidewalls thereof can be provided with a plurality of access apertures to which parallel cable glands or conduits can be secured, in use.

In addition, where the electrical connection boxes are to be partially embedded in concrete they have to be sufficiently robust to withstand the pressures exerted thereon whilst the concrete is wet. Accordingly, in many cases, cast iron electrica,l connection boxes are employed in view of the fact that relatively thin walled, pressed metal boxes are insufficiently robust. Such cast iron boxes are extremely costly.

It is the object of this invention to provide an electrical connection box which exhibits advantageous characteristics over those described above.

In accordance with this invention there is provided an electrical connection box having a hollow, substantially rectangular body with a circular access opening thereto in one face of the body, the access opening having screw threads complementary to those carried on a closure having a circular screw threaded portion.

The electrical connection box may be moulded from suitable, optionally reinforced, plastics material, in particular a dough moulding compound.

The electrical connection box may be moulded in two parts subsequently secured together. The two parts may have interengaging formations and one part adapted to fit inside another part. In the latter instance, the part having the outermost formation can when in a heated condition, preferably freshly moulded, the brought together with the other part in a cooler condition so that contraction upon cooling of the heated part causes firm locking of the parts together.

The plastics material or dough moulding compound may be reinforced with glass fibre reinforcing material.

The cover may have either a female screw thread co-operable with a male screw threaded rim surrounding the aperture to the connection box, in which case the cover may be provided with external friction affording formations on the periphery thereof. Alternatively, the cover may have a male screw threaded section co-operating with an internal screw thread associated with the access aperture. In either case the cover could be circular on its outer configuration with a circular portion for co-operation with the access opening or, alternatively, the cover itself may have a rectangular peripheral shape.

Where the cover has a circular peripheral shape and an externally screw threaded portion for co-operation with an internally screw threaded access aperture, the whole cover can be recessed so that its outer surface, in the closed condition, is flush with the remainder of outer adjacent peripheral surface of the connection box.

An earthing insert may be embodied in the rectangular shaped body, the earthing insert assuming the form of a metal plate following a rectangular path to substantially conform with the inside surfaces of the sidewalls of the box. In the case where the box is made in two parts, such an earthing insert can be introduced into the connection box prior to assembly thereof. Conveniently such an insert is located by means of a moulded lip in one part of the box and by the base at its opposite edge. The box can be provided with flanges, optionally perforated or provided with slots, for enabling it to be secured by means of fasteners to a support surface therefor.

In order that the invention may be more fully understood, two different embodiments thereof will now be described by way of example with reference to the accompanying drawings in which: Figure 1 is a partly sectioned plan view of an electrical connection box according to this invention; Figure 2 is a sectional side elevation thereof; and, Figure 3 is an exploded isometric view of a second embodiment of the invention.

In the embodiment of the invention illustrated in Figs. 1 and 2 a generally square electrical connection box 1 is moulded of a dough moulding compound which is reinforced with glass fibres. The moulding is effected by a press moulding technique and the box itself is made into parts 2 and 3.

The one part 2 is in the form of a substantially flat bottom base having extensions 4 at each of two sides thereof which are perforated as indicated by numeral 5 to enable the base to be secured to a support surface for the box.

The side walls part 3 is of basically square shape but with a circular aperture 6 at the top opposite the base 2.

The aperture 6 occupies substantially the entire transverse dimension of the box with only roughly triangular shaped shoulders 7 being defined at the corners. The aperture 6 forms the inside surface of an externally screw threaded ring shaped protrusiion 8 next to shoulder 9.

A similarly manufactured cover 10 is made to co-operate with the access aperture and, accordingly, has internal screw threads in cooperative engagement with the external screw threads on the ring shaped portion of the box.

The lid has, in a circular groove 11 therein an Ring, which, in operative position, engages the end surface of the ring shaped portion in order to seal the box in a closed condition.

The cover is to some extent domed in order to improve rigidity.

In order to secure the two parts of the electrical connection box together a squareshaped ridge 1 2 is provided on the base 2 so as to be located on the inside of the sidewalls part 3. The part 3, on the other hand, has a rebate 1 3 adapted to accommodate the ridge 1 2 and, in the regions where the extensions are present, these sidewalls are accommodated in what is effectively a groove defined between the ridge and the extensions.

The dimensioning of the ridge and co-operating regions of the other part, are such that, with the base in a cold condition, the moulded other part can, in a hot condition, be easily pressed onto the ridge. As the hot part cools, it contracts so that an extremely tight engagement is formed between the ridge and rebate to provide a box which will not become separated into two parts in use.

It will be understood that numerous other possibilities exist for the securing of two parts together and the invention is not to be interpreted as being limited to that described above. In particular, the parts may be adhesively secured together and, indeed, the parts could be made from materials other than plastic although plastic is preferred due to its non-corrosive nature.

It will be understood that, in use, the structural strength of the connection box can be chosen to suit requirements and, according to the plastic materials employed. It is an extremely simply matter to secure a cover over the access aperture to the electrical connection box which, in the usual way, is provided with prefabricated access holes 14 in the sidewalls thereof. The holes may be provided with blank closures or, alternatively, integral material may be formed to close off the hole with a zone of weakening around the periphery thereof so that such zones can simply be broken out as and when required. These holes are then employed for the connection of electrical cable glands or conduits to the box in the usual way.

Turning now to Fig. 3 of the drawings there is illustrated a generally similar box 1 5. An internal earthing insert 1 6 provided with prefabricated holes 1 7 therein which are located to correspond with holes, or blank holes, in the walls of the box as indicated by numeral 18. The earthing insert is a strip of conductive metal plate bent to a square configuration to conform substantially with the inner surface of the side walls of the box. Adjacent the top of the side walls a lip 20 is provided for locating and holding the earthing insert in position.

The holes in the earthing insert can be threaded, for example by tapping, or, alternatively, a nut may be secured thereto by any suitable process providing earthing continuity.

Of course it is within the scope of this invention to leave the walls of the earthing insert plain and to employ, in known manner, nuts on the end of a conduit or spigot of a cable gland, for example.

The manufacture of the above described connection box may be that outlined above, and, in such a case, the earthing insert is simply slipped inside the part having the lip, when it is hot, and such part is then pressed onto the base.

In this embodiment of the invention, however, the cover 21 carries the externally screw-threaded protrusion 22 and the box itself has an internally screw-threaded access aperture 1 9 of circular shape. The cover has suitable recesses 23 in its front face for engagement by a complementary tool for locating the cover. Again a suitable sealing ring, such as an O-ring, can be employed between the projecting periphery 24 of the cover and the face 25 of the box.

If required, with the above arrangement, the substantially flat surface of the cover can be flush with the surface of the box simply by providing a recess in the face of the box to accommodate the cover in the closed position.

In this embodiment of the invention there is illustrated knock-out portions 26 moulded integral with the material from which the box is manufactured and which can be simply removed in order to provide the required holes in the sidewalls of the box.

It will be understood that numerous other embodiments of the invention are possible. In particular, the method of manufacture can be varied widely and, in fact, the box could be manufactured of cast iron whilst still providing the advantages of the circular access aperture with a single lid co-operating with screwthreads associated therewith. Also, where the box is made in two parts which are secured together, and divisions of the parts can be employed. In fact, the box could be made to be divided in two along a plane at right angles to the base. In such a case by selection of interengaging formations, it will be possible to make moulds or dies to form the parts of a single configuration provided a two-start thread is employed.

Embodiments of the invention provide a simple yet highly useful electrical connection box which obviates the employment of screws and the like for securing a cover over the access aperture to the connection~ box.

Claims (9)

1. An electrical connection box having a hollow, substantially rectangular body with a circular access opening thereto in one face of the body, the access opening having screw threads complementary to those carried on a closure having a circular screw threaded portion.

2. An electrical connection box according to Claim 1, in which the box parts are made by a moulding technique.

3. An electrical connection box according to Claim 1 or 2 in which the box is moulded in at least two parts which have interengaging formations arranged to co-operate in use to hold the parts together.

4. An electrical conection according to any one of Claims 1 and 3 in which the circular aperture is surrounded by an upstanding protrusion having an external thread for receiving a cover having an internal thread.

5. A generally square electrical connection box having a bottom base, four integrally formed sides shaped to provide an upstanding circular top aperture, with a diameter substantially equal to the width of the box which is externally threaded, and a circular cover which fits over the top with internal threads to co-operate with the thread of the aperture.

6. A connection box according to Claim 5, in which the four sides and the base are separately formed and the four sides are interlocked securely to the base by co-operation formations at the interface between the four sides and the base.

7. A generally square electrical connection box having a bottom base, four integrally formed sides and a top, the top having a threaded aperture substantially equal in area to the cross-sectional area of the box, and a circular cover with a downward threaded protrusion which cooperates with the threads of the aperture.

8. A connection box according to Claim 7 including a metal earthing plate which fits against the extends around the inside surfaces of the sides.

9. A connection box according to any of claims 1-8, in which the box is formed of reinforced moulded plastic parts.

1 0. An electrical connection box substantially as herein described with reference to Figs. 1 8 2, or Fig. 3 of the accompanying drawings.