GB2288699A

GB2288699A - Earthing cable entry of a junction box

Info

Publication number: GB2288699A
Application number: GB9508086A
Authority: GB
Inventors: Franz Lackinger
Original assignee: WESTWARD INVESTMENTS; Westward Investments Ltd
Current assignee: WESTWARD INVESTMENTS; Westward Investments Ltd
Priority date: 1994-04-20
Filing date: 1995-04-20
Publication date: 1995-10-25
Also published as: GB9508086D0; AU1654995A

Abstract

A junction box has entry apertures in each of which is mounted a tube 16 having a flange 15 (fig. 2), an internal screw-thread and a flared end 17 which retains the tube in the aperture. The flange 15 and the body of the box sandwich either an L-bracket 12 of an earth continuity plate 10, an L-bracket (30, fig. 6, not shown) electrically connected to an earth continuity plate, or a section of an earth continuity strip (20, fig. 4, not shown) which extends round the inside of the side wall of the box. The box may be round in section with and have a sealed lid. The flange 15 may be permanently attached to the bracket or strip. <IMAGE>

Description

ELECTRICAL CONNECTION BOX HAVING EARTH CONTINUITY ARRANGEMENT FIELD OF THE INVENTION This invention relates to an electrical connection or junction box made of electrically insulating material, usually a moulded plastics, optionally reinforced and containing filler material such as a dough moulding composition, and wherein an electrical continuity arrangement is included so that metal connection spigots of cable glands associated with each cable entry into the box are interconnected to provide for electrical continuity of what is usually the earth.

BACKGROUND TO THE INVENTION Many different forms of electrical connection boxes having electrical continuity between the cable entries thereto have been produced. Usually the arrangement is such that an electrical connection is automatically provided when a nut on the inside of the electrical connection box, and co-operating with an externally screw-threaded spigot of a cable gland passing through the wall of the box, is secured in position.

In one arrangement which applicant has used heretofore the electrically conductive nuts are rigidly interconnected by means of robust conductor rods brazed to each other and to the nut. Whilst applicant is unaware of any difficulties which have been occasioned by this arrangement in the field, it has met with certain rejection on the basis that stresses and strains imposed on the joints between the nuts and conductors, when the various nuts have a cable gland secured thereto, could cause the joint to fracture or crack and the electrical continuity to be thus interrupted.

An alternative arrangement is to provide a loose metal continuity plate having upstanding zones located adjacent the cable entry apertures. When installed in the box, an upstanding zone is automatically engaged by the electrically conductive nut, which is loose and forms part of the cable gland. This arrangement has two disadvantages, the first of which is that the plate can simply be left out during installation and such an omission cannot be observed visually once the connection box is closed. Secondly, dirt or other material leading to breakdown of electrical continuity can become interposed between the nut and plate, for example during installation.

The first of these difficulties has been addressed by the proposal put forward in British Patent no.

2262000. In this case the electrical continuity plate is actually partly moulded into the plastic from which the box is manufactured. This proposal does not address the second problem mentioned above. This proposal is also costly to manufacture, as the positioning of a pre-manufactured continuity plate in an injection die is time consuming and slows down production of the moulded plastics boxes.

It is the object of this invention to provide an improved arrangement involving the use of an electrical continuity plate or strap in which all of the disadvantages mentioned above may be obviated.

SUMMARY OF THE INVENTION In accordance with this invention there is provided an electrical connection box made of electrically insulating material and embodying a continuity plate or strap electrically connected to a plate-like zone associated with each cable entry aperture to the box, and wherein each of such zones has associated therewith a fitting having a flange for bearing against the said zone, with the fitting have a tubular portion extending into the associated cable entry aperture of the box with the free end of the tubular portion being flared outwardly to lock the fitting in position, and wherein the fitting is internally screw threaded to receive an externally screw threaded spigot of a cable gland or the like.

Further features of the invention provide for the flange portion of each fitting to be soldered, brazed or otherwise permanently secured to the plate-like zone (an operation which may conveniently be carried out after assembly of the box, continuity plate and fittings); for the flange portion of each fitting to be of a polygonal shape suitable for engagement by a spanner as may be required; and, for the electrical continuity plate or strap to assume either the form of a plate extending over the greater portion of the bottom of the electrical connection box or, alternatively, for it to assume the form of a broad strap extending around a major portion of the inner sidewall of the electrical connection box.

Still further features of the invention provide for the said plate-like zone to be defined, in each case, by one flange of a right angled bracket, the other flange of which is in electrical contact with the continuity plate or strap itself; for the electrical connection between the said other flange of each bracket and the continuity plate to be effected by a screw threaded fastener extending into a nut, preferably moulded into the base of the electrical connection box, and whereby the said flange and electrical continuity plate are held in firm engagement with each other, and thus in electrical contact; and for the said other flange of each bracket to have a slot for accommodating the screw threaded fastener to thereby allow for radial adjustment of the flange relative to the box and continuity plate.

Preferably the electrical connection box itself is of a substantially right circular cylindrical configuration having a circular lid for co-operation with one end of the cylindrical shape and conveniently having an O-ring for sealing the box in a closed condition by engagement with the associated end edge of the cylindrical box.

In order that the invention may be more fully understood, three different embodiments thereof will now be described with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings: Figure 1 is an exploded isometric view showing part of the interior of an electrical connection box according to the invention; Figure 2 is a partly sectioned elevation of the connection box in a closed condition; Figure 3 is an exploded view illustrating a fitting and associated zone of a continuity plate; Figure 4 is an illustration similar to Fig. 1 but of a different embodiment of the invention; Figure 5 is an exploded isometric view of an alternative and preferred electrical connection box with its lid removed entirely; Figure 6 is a partly sectioned elevation of the electrical connection box of Figure 5 in the closed condition; and Figure 7 is a detailed exploded view showing one bracket arrangement of the embodiment of Figures 5 and 6 in detail.

DETAILED DESCRIPTION WITH REFERENCE TO THE DRAWINGS In the embodiment of the invention illustrated in Figures 1 to 3 the electrical connection box assumes the form of a squat, right circular cylindrical box (generally indicated by numeral 1) having radially extending mounting lugs 2 at the base end thereof and open at its other end 3 which provides a circular access opening. The box has external screw-threads 4 at its access opening which co-operate with screw-threads 5 on a circular lid 6 having a rubber O-ring 7 for sealing on the upper edge 8 of the box. This box is of basically known configuration and has f our equally angularly spaced cable entry apertures 9 in the circular sidewall thereof.

In terms of this invention an electrical continuity plate 10 is provided, the plate, in this case, extending over a major portion of the bottom 11 of the electrical connection box. The continuity plate 10 has basically a diamond-shape in plan view with an upstanding zone 12 at each corner thereof.

Each upstanding zone 12 is of basically rectangular shape; is centrally perforated; and, is arranged such that the perforation registers with the associated cable entry aperture 9.

Each of the upturned zones 12 is arranged to be substantially flush with a flat zone 13 formed on the inside of the sidewall of the box.

Each of the zones 12 is fastened in this position by means of a fitting 14 (shown most clearly in Fig. 3) where each fitting comprises a square flange 15 from which a tubular portion 16 extends.

The tubular portion extends, in each case, through the cable entry aperture and the free edge 17 of the tubular portion is flared outwardly by mechanical deformation to lock the fitting and, in consequence, the zone 12 of the plate, firmly in their operative positions. The fitting therefore serves substantially like a large tubular rivet.

In order to ensure excellent electrical continuity, the flange 14 is then subsequently soldered, brazed, or otherwise electrically united with the adjacent zone 12 of the continuity plate. Such soldering, brazing or the like need only take place along the most accessible edge of the flange which will be nearest the access opening of the box.

The bore through the fitting is internally screw-threaded, as indicated by numeral 18, to receive an externally screw-threaded spigot of a cable gland in the usual way.

It will be understood that an electrical connection box and continuity plate assembly as described above avoids the disadvantages of the prior art arrangements outlined in the preamble hereto.

Whilst not being considered to be particularly necessary, it may be required to additionally secure the plate in its position on the bottom of the box. In this event the plate may be suitably perforated and secured to the bottom by means of screws 19 extending into co-operant metallic nuts moulded into the bottom of the electrical connection box in known manner.

As an alternative to the embodiment illustrated in Figs. 1 to 3, the electrical continuity plate may be replaced by a strap 20 illustrated in Fig. 4.

Such a strap extends around the inside of the sidewall of the box 21 to provide a zone passing over each of the cable entry apertures 22. Each of such zones is then secured to the cable entry apertures of the box by means of a fitting 23 as described above. Whilst not being considered to be necessary and as indicated above, a bent tab formation 24 may be used to secure the strap 20 the bottom 25 of the box by means of a screw 26 co-operating with a nut member moulded into the bottom of the box (not illustrated).

The embodiment of the invention illustrated in Figures 5 to 7 of the drawings is a further alternative and to be preferred by virtue of manufacturing tolerances not being as stringent as will be the case at least in the embodiment of Figures 1 to 3.

In this embodiment of the invention, the upturned zones 30 which co-operate with the square flanges 31 of the fittings 32 are, in fact, one flange of a right angled bracket 33. The other flange 34 of the bracket 33 is, in each case, clamped to the base 35 of the box 36 by means of screws 37 which pass through a substantially circular continuity plate 38 and into nut members 39 moulded into the base of the box.

In this manner the said other flange 35 of each bracket and the continuity plate, are firmly clamped together by screw threaded fasteners, this type of connection being commonly accepted as being an adequate and effective electrical connection.

In order to allow for radial adjustment of the position of the brackets, and, accordingly, allow for stress-free connection between the fitting and the zone 30 of the bracket by means of the brazed or soldered connections 40, each bracket has a slot 41 extending, in the operative position, in a radial direction so that radial adjustment of the position of the brackets can be made and, indeed, the end 42 of the tubular portion 43 of the fitting can be pened over prior to securing of the screws 37 in position.

It will be understood that this embodiment of the invention enables tolerances to be fairly large, and yet the advantages described above are all retained.

It will be understood that numerous variations may be made to the embodiments of the invention described above without departing from the scope hereof which is directed particularly at the use of the fittings to secure the electrical continuity plate or strap to the cable entry apertures of an electrical connection box.

Claims

CLAIMS:

1. an electrical connection box made of electrically insulating material and embodying a continuity plate or strap electrically connected to a plate-like zone associated with each cable entry aperture to the box, and wherein each of such zones has associated therewith a fitting having a flange for bearing against the said zone, with the fitting have a tubular portion extending into the associated cable entry aperture of the box with the free end of the tubular portion being flared outwardly to lock the fitting in position, and wherein the fitting is internally screw threaded to receive an externally screw threaded spigot of a cable gland or the like.

2. An electrical connection box as claimed in claim 1 in which the flange portion of each fitting is soldered, brazed, or otherwise permanently electrically united with the associated plate-like zone.

3. An electrical connection box as claimed in either of claims 1 or 2 in which the flange portion of each fitting is polygonal in shape to enable engagement by a spanner.

4. An electrical connection box as claimed in any one of the preceding claims in which the continuity plate extends over the greater portion of the bottom of the connection box.

5. An electrical connection box as claimed in any one of claims 1 to 3 in which the electrical continuity plate assumes the form of a broad strap extending around a major portion of the inner sidewall of the electrical connection box.

6. An electrical connection box as claimed in any one of claims 1 to 4 in which the said plate-like zone is defined by one flange of a right-angled bracket, the other flange of which is in electrical contact with the continuity plate itself.

7. An electrical connection box as claimed in claim 6 in which the electrical connection between the said other flange of each bracket and the continuity plate is effected by a screw threaded fastener,extending into a nut.

8. An electrical connection box as claimed in claim 7 in which the nut is moulded into the base of the box.

9. An electrical connection box as claimed in any one of claims 6 to 8 in which the said other flange of each bracket has a slot for accommodating a screw threaded fastener to enable radial adjustment of the flange relative to the box.

10. An electrical connection box as claimed in any one of the preceding claims in which the box is of a substantially right circular cylindrical configuration having a circular lid for cooperation with one end of the cylindrical shape and having an O-ring for sealing onto the edge of the box in use.

11. An electrical connection box substantially as herein described and exemplified with reference to any of Figures 1 to 3; 4 and Figures 5 to 7 of the accompanying drawings.