FIELD OF THE INVENTION

This invention relates to an electrical connection box having a switch for controlling the supply of electrical energy to an item of electrically operated equipment connected by way of the electrical connection box.

The invention also relates to a conversion kit whereby an existing electrical connection box that does not have a switch associated with it can be converted to one that does have a switch. It is to be noted that the term standard electrical connection box as used in the specification is intended to mean an electrical connection box that is produced for the purpose of being used on its own independently of the present invention. BACKGROUND TO THE INVENTION

There are numerous electrical installations in which multiple electrical connection boxes are installed in an electrical supply line in order to provide multiple items of electrically operated equipment such as lights that may need isolation individually for the purpose of service or maintenance, especially, in the instance of lights, for the purpose of replacing bulbs or ballasts.

Existing installations are generally such that an entire group of lights needs to be switched off simultaneously in order to isolate the relevant electrical circuit. This is not always convenient or desirable if operations are to continue in the area that is illuminated by the group of lights such as in at least particular areas of mines and mineral processing facilities.

One alternative that has been proposed in order to solve this problem is to provide a separate switch box attached to each of the individual electrical connection boxes on one side thereof so that each of multiple circuits can be switched off individually as and when required. However, this solution is not particularly attractive in many instances as there is often no physical space available in a laterally offset position for the safe location of such a switch box.

There is accordingly a need for an electrical connection box having a switch in communication with the interior of the electrical connection box. There is also a need for a conversion kit whereby an electrical connection box in an existing installation that is devoid of a switch can be provided with one.

SUMMARY OF THE INVENTION

In accordance with a first aspect of the invention there is provided an electrical connection box assembly comprising an electrical connection box having a bottom and sidewalls that define an internal space having a central axis extending in the direction in which the sidewalls extend and openings in the sidewalls or bottom wall or both for receiving electrical cable glands or closure plugs in the alternative; an open top surrounded by free edges of the sidewalls, and a separate housing assembly coaxial with the box and having a generally tubular side wall with a closed outer end and a switch therein that is operable from the closed outer end of the separate housing assembly wherein an inner end of the tubular side wall of the separate housing assembly has a periphery that is releasably sealed to the free edges of the sidewalls of the electrical connection box in the closed condition of the electrical connection box assembly.

Further features of the first aspect of the invention provide for the generally tubular side wall of the separate housing assembly to be a generally tubular extension unit forming an extension to the sidewalls of the electrical connection box; for the separate housing assembly to include a switch supporting unit mounted to an outer end of the tubular side wall of the separate housing assembly; for the tubular side wall and switch supporting unit to be of circular shape in cross-section at least where they are attached to each other at an outer end of the tubular side wall in which instance they are preferably secured to each other utilising a union nut having a thread engaging a cooperating thread on the outer surface of the tubular side wall with a seal interposed between adjacent peripheries of the tubular side wall and switch supporting unit; for the electrical connection box to be a standard electrical connection box; for the switch to be coaxial with the electrical connection box and separate housing assembly; and for the switch operating member to be a generally diametrically extending finger grip whereby the operating member can be rotated about the axis of the assembly.

Still further features of the first aspect of the invention provide for the outer end of the separate housing assembly to have a removable dust cover thereon that is preferably permanently held captive relative to the separate housing assembly by means of a flexible element that in turn is preferably attached to the centre of the dust cover in the instance that the latter is screw threaded for installation on a cooperating screw thread on the separate housing assembly; and for the switch operating member and separate housing assembly to have formations in registration with each other in the "off" condition of the switch when any dust cover is removed so as to be capable of receiving a removable padlock or the like to prevent unauthorised closing of the switch. Yet further features of the first aspect of the invention provide for connectors to be provided either within the electrical connection box or on a mounting plate that is secured to the electrical connection box either internally or in the region of the open top thereof; for the switch supporting unit to be of a explosion proof type embodying a explosion proof switch cover through which an operating shaft of the switch extends axially in close fitting relationship with the switch being enclosed within a suitable explosion proof enclosure; and for a compression type of seal to be provided at an entrance to a explosion proof enclosure of the switch supporting unit for sealing onto individual conductors to be connected to the switch.

In accordance with a second aspect of the invention there is provided a conversion kit for an existing electrical connection box of the type having a bottom, sidewalls that define an internal space having a central axis extending in the direction in which the sidewalls extend and openings in the sidewalls or bottom wall or both for receiving electrical cable glands or closure plugs in the alternative wherein the electrical connection box has an open top surrounded by free edges of the sidewalls wherein the electrical connection box has a lid for closing the open top, the conversion kit comprising a separate housing assembly for coaxial mounting on the electrical connection box with its lid removed and wherein the separate housing assembly has a generally tubular side wall with a closed outer end and a switch therein that is operable from the closed outer end of the separate housing assembly with an inner end of the tubular side wall of the housing assembly having a periphery adapted to be sealed to the free edges of the sidewalls of a cooperating electrical connection box in the operative condition of the conversion kit.

Further features of the conversion kit are as defined above in relation to the electrical connection box assembly itself. In accordance with the third aspect of the invention there is provided a method of providing a switch in an electrical circuit supplied from a existing standard electrical connection box, the method comprising removing the lid from the existing standard electrical connection box; providing any additional internal electrical connectors; providing a connector kit as defined above; reconnecting an outlet connection by way of the switch forming part of the conversion kit; and installing the conversion kit on the electrical connection box in place of the lid thereof and in sealing relationship relative thereto to form a combined sealed space within the resultant electrical connection box assembly.

In one variation of the invention that is applicant's preferred variation, the electrical connection box is of generally circular shape and has a circular lid with a screw thread at or towards its periphery for cooperating with a co- operant screw thread surrounding the open top of the box itself such that the lid may be installed on the box by rotating it about its own axis. This arrangement affords enhanced security against unauthorised opening of the electrical connection box that is brought about by shaping the exterior of the lid for engagement by a dedicated or custom tool for rotating the lid.

In another variation of the invention the electrical connection box may have a generally rectangular, especially square, lid secured in position using screws at or towards the four corners of the rectangle. In either variation the electrical connection box generally has the usual lugs for securing it to a mounting surface.

In order that the invention may be more fully understood one embodiment thereof as well as a variation 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 of one form of standard electrical connection box of a first variety namely one having a circular lid;

Figure 2 is a sectional elevation of one embodiment of electrical connection box assembly according to the invention;

Figure 3 is an exploded isometric view of a the electrical connection box illustrated in Figure 2;

Figure 4 is a view similar to Figure 2 but illustrating more clearly the second aspect of the invention as applied to that embodiment;

Figure 5 is a view similar to Figure 3 but illustrating a variation of the embodiment of the invention illustrated in Figure 3;

Figure 6 is a side view of a second embodiment of electrical connection box assembly according to the invention which is of an explosion proof category;

Figure 7 is an enlarged sectional side view thereof;

Figure 8 is an exploded isometric view similar to Figure 3 but showing the electrical connection box illustrated in Figures 6 and 7; and, Figure 9 is an exploded side view of the explosion proof switch supporting unit and its various components.

DETAILED DESCRIPTION WITH REFERENCE TO THE DRAWINGS

In the embodiment of the invention that is illustrated in Figures 2 to 4 of the accompanying drawings, a standard electrical connection box (1 ) is of generally circular shape and in the instance that it is an existing installed connection box, it would have a circular lid (2) that is illustrated in Figure 1 . The electrical connection box has a screw thread (3) at or towards its periphery for cooperating with a co-operant screw thread on the lid itself such that the lid may be installed on the box by rotating it about its own axis.

As mentioned above, this arrangement affords enhanced security against unauthorised opening of the electrical connection box as by shaping the exterior of the lid with a series of lobes (4) encircling the lid the periphery thereof is made suitable for engagement by a dedicated custom complementarily ring shaped tool (not shown) with diametrically extending handles for rotating the tool and lid.

The electrical connection box has a bottom (5) from which sidewalls (6) project, in this instance at right angles, to define an internal space that is used to accommodate connectors of any suitable type such as those indicated by numeral (7). The upper free edges of the sidewalls define an open top to the internal space. The internal space has a central axis indicated by line A-A that extends parallel to the direction in which the sidewalls extend.

Openings (8) are provided, in this instance in the sidewalls, for receiving electrical cable glands or closure plugs in the alternative (neither of which are illustrated in Figures 2 to 4). As provided by this invention, a separate housing assembly, generally indicated by numeral (9), is provided for attachment coaxially to the box (with any lid (2) removed and optionally discarded), the housing assembly having a switch (1 1 ) therein that is operable from a closed outer end of the housing assembly. The housing assembly is, in this instance, made up of a generally tubular extension unit (12) forming an extension to the sidewalls of the electrical connection box and a switch supporting unit (13) mounted to an outer end of the extension unit. Both the extension unit and the switch supporting unit are of circular shape in cross-section and the extension unit is provided with an internal screw thread cooperating with the external screw thread on the box itself so that it can be screwed onto the box in place of the lid that is illustrated in Figures 1 and 4. The extension unit seals onto the upper free edges of the sidewalls by way of a large diameter O-ring (14) in exactly the same manner as the lid may have formerly. The extension unit and switch supporting unit are secured to each other utilising a union nut (15) having a thread engaging a cooperating thread on the outer surface of the extension unit, as indicated by numeral (16), with a ring shaped seal (17) interposed between adjacent peripheries of the two units. This arrangement enables conductors to be attached to the switch whilst the connection box assembly is closed without twisting the conductors in any way.

Of course, the outer peripheries of both the extension unit and the union nut may be provided with a lobes that are substantially identical to those illustrated in Figure 1 on their peripheries so that the same tool can be used to rotate them.

The switch is coaxial with the electrical connection box and separate housing assembly and has an operating member in the form of a generally diametrically extending finger grip (18) rotatable about the axis of the assembly. A removable dust cover (21 ) is provided for the outer end of the switch supporting unit so as to totally enclose the outer end of the switch. The dust cover is held captive relative to the supporting unit by means of a flexible element (22) (see Figure 2) that in turn has one end attached in relatively rotatable manner to the inside of the dust cover at its centre and the other end attached to the inside of the switch supporting unit. The dust cover may either clip into its operative position or it may have a screw thread for cooperation with a cooperating screw thread on the switch supporting unit. It is preferred that the switch operating member and separate housing assembly have formations, typically apertures (23) that are in registration with each other in the "off" condition of the switch, so that a removable padlock or the like can be installed in the apertures in the "off" condition to prevent unauthorised closing of the switch. The padlock does not interfere with the dust cover which is inoperative in such an instance whilst remaining attached to the switch supporting unit by means of the flexible element.

It will be understood that the electrical connection box assembly described above can be assembled and sold in the form described, or, alternatively, the separate housing assembly may be sold as a conversion kit for a substantially conventional existing electrical connection box. The separate units are clearly illustrated in Figure 4.

In the latter instance of the sale of the conversion kit, the method of providing a switch in an electrical circuit supplied from an existing electrical connection box simply involves removing the lid from the existing box; providing any additional internal electrical connectors; providing a connector kit as described above and indicated by numeral (9) and reconnecting an outlet connection by way of the switch that forms part of the conversion kit. Of course, installation of the conversion kit on the electrical connection box would take place by firstly installing the tubular extension unit (12) followed by completing the electrical connections and thereafter closing the conversion kit by installing the switch unit using the union nut. The conversion kit plus replaces the lid of the connection box with which it is in sealing relationship to form a combined sealed space within the resultant electrical connection box assembly. It will be understood that, for example, a row of interconnected lights in an underground mining situation that is connected to a common source of electrical energy and wherein each light has a power take off whereof the connections are contained within a standard electrical connection box, may be provided with individual switches utilising the conversion units provided by this invention. Such switches can easily be added in order to provide a separate switching facility for each light so that it can be turned off independently of the others for service or maintenance purposes. The remaining lights of an interconnected series thereof can therefore remain illuminated whilst any one of the lights is individually switched off and subjected to maintenance or service, as may be required.

Referring now to Figure 5 of the drawings, in a variation of the embodiment pf the invention described above, the standard electrical connection box may have a generally square configuration with the lid, or in this instance the extension unit (25), secured in position using screws at or towards the four corners of the generally square shape of the box that in this instance is formed by four lugs (26) at the corners of the square. In such an instance, the extension unit (25) has corresponding lugs (28) that are secured to the lugs of the box using screws in well-known manner.

Turning now to the embodiment of the invention illustrated in Figures 6 to 9 of the drawings, the electrical connection box (31 ) is, in this instance, of the type that the sidewalls are inclined to the bottom so that easier access is provided to the interior when the walls are inclined upwards in the installed position. In this instance electrical connectors (32) are provided on a mounting plate (33) that is in the electrical connection box assembly provided by this invention, releasably secured to the electrical connection box in the region of the open top thereof. Openings (34) for receiving one or more cable glands (35) are provided in the operatively lower sidewalls of the electrical connection box. The necessary conductors (36) to which the cables are to be connected may pass through the mounting plate for convenience of making connections on both sides thereof.

In this instance a tubular extension unit (37) forms an extension to the sidewalls of the electrical connection box and a switch supporting unit (38) is mounted to an outer end of the extension unit. In this instance the switch supporting unit is of a explosion proof type and the switch assembly includes a explosion proof switch cover (41 ) through which an operating shaft (42) of the switch (43) extends axially in close fitting relationship. The switch is enclosed within a suitable explosion proof enclosure that includes a blind tubular housing (44) receiving a switch housing bush (45) fitted with a closure (46) at the end opposite the switch cover. An entrance through the closure has a compression type of seal (47) to the explosion proof enclosure of the switch supporting unit. The compression seal has individual holes (48) through it for sealing onto individual conductors that need to pass into the explosion proof enclosure in order to be connected to the switch. The switch is fixed within the switch housing bush (45) by means of a ring of bonding compound (49) at the inner end thereof.

The switch supporting unit is sealed to the outer free end of the tubular extension unit using a sealing ring (51 ) and union nut (52) in the same manner as is described above.

It will be understood that numerous variations may be made to the embodiments of the different aspects of the invention described above without departing from the scope hereof.