MULTI-WAY UNDERGROUND LINK BOX FIELD OF THE INVENTION

The present invention relates to the interconnection of low voltage high current carrying cables and, in particular discloses a compact form of interconnect with switching capabilities.

BACKGROUND OF THE INVENTION The distribution of electricity to household residential and commercial premises is often by way of three phased sector cables. The sector cables are designed to carry large currents at fairly low voltages from a step down transformer. When providing a power distribution network, it is often necessary to interconnect cables and to provide switching capabilities there between. Recently, it has become increasingly popular to provide for underground distribution of the sector cables.

Fig. 1 to Fig. 4 illustrate a prior art arrangement utilised in underground sector cable interconnection placed in the pavement or the like. The arrangement includes a central switching box 2 and two defined staging boxes 3, 4. The staging boxes 3, 4 are, after interconnection with the sector cables, filled with a resinous hard setting material. Turning to Fig. 2, there is illustrated one form of staging box 3 with its top cover removed and before the resin has been added. Fig. 2 illustrates the attachment of each phase of the sector cable in addition to the neutral which are in turn attached to connection junction tabs projecting from the side of the switching box 2.

The arrangement of Fig. 1 is then installed underground with the switching box 2 being separately accessible. A pavement installation is illustrated in Fig. 3. Normally, as illustrated in Fig. 4, a bell housing 7 is provided so as to allow for waterproofing and an manhole cover 8 is provided for allowing for a flush finish in the underground arrangement when utilised as part of a floor or the like.

The prior art arrangement has a number of disadvantages apart from its excessive cost. A large quantity of resin is required to fill the staging boxes 3, 4 and it requires a large volume space to install when including the staging boxes. Further, the bell housing arrangement often results in condensation forming around the bell housing and dropping onto the switching box which is undesirable. The arrangement also, once installed, has difficulty in breaking the neutral line. The breaking the neutral line is an important

procedure that is often required to be undertaken during maintenance operations. Because the unit is sealed in resin it is difficult to provide for such breaking.

Any discussion of the prior art throughout the specification should in no way be considered as an admission that such prior art is widely known or forms part of common general knowledge in the field.

SUMMARY OF THE INVENTION

The summary of the present invention provides an improved form of link arrangement.

In accordance with a first aspect of the present invention, there is provided a link box arrangement for interconnecting sector cables together, the arrangement including: a base having an upturned lip, the lip having a series of apertures for insertion of sector cables therethrough; a switching box including a series of link switch cavites having first and second conductive surfaces on sides thereof, the surfaces insulate from one another; a first conductive surface interconnected to a conductive tab having a sector cable clamping arrangement on one end thereof; a second conductive surface interconnected to a busbar arrangement which interconnects to other predetermined surfaces of other link switch cavities.

There are preferably four bus bars for interconnecting three phases and one neutral in accordance with requirements. The arrangement preferably also provides a bell housing for placing over the link box arrangement; and a clamping means for clamping the bell housing to the link box arrangement.

Preferably, there is provided a series of detachable link switch cavity covers for covering the link cavities and at least one link switch for insertion into a link switch cavity for electrically interconnecting the conductive surfaces. The base preferably can include an internal cavity surrounding each conductive tab and the arrangement further preferably can include: a hard setting insulating resin encasing the conductive tab. The arrangement can also include a series of aperture plugs for plugging any gaps between any sector cable and aperture wall of the series of apertures. The bell housing can be formed from a plastic material. The bell housing preferably can include an upturned circumferential lip for capture of any moisture forming on the external surface of the bell housing.

Unless the context clearly requires otherwise, throughout the description and the claims, the words "comprise", "comprising", and the like are to be construed in an inclusive sense as opposed to an exclusive or exhaustive sense; that is to say, in the sense of "including, but not limited to".

BRIEF DESCRIPTION OF THE DRAWINGS

A preferred embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawings in which:

Fig. 1 to Fig. 4 are perspective views of a prior art underground link box in common use; Fig. 5 illustrates an exploded perspective of the preferred embodiment;

Fig. 6 illustrates a side perspective view of the preferred embodiment in an assembled form;

Fig. 7 and Fig. 8 are side perspective views of the preferred embodiment with resin encasing; Fig. 9 illustrates a bottom side perspective view of the preferred embodiment;

Fig. 10 illustrates a side perspective of an initial base plate assembly; Fig. 11 illustrates a side perspective view of a subsequent base plate assembly; and

Fig. 12 illustrates a partly exploded bottom side perspective view of the base plate assembly.

DESCRIPTION AND PREFERRED AND OTHER EMBODIMENTS

In the preferred embodiment there is provided a compact arrangement for linking sector cables whilst simultaneously providing switching capabilities.

Turning initially to Fig. 5, the arrangement 10 shown in the prototype form with a bell hosing 11 which is used to protect the switch from moisture. The bell housing 11 is held in place by means of clamping bar 12. The clamping bar 12 is affixed by wing nuts 15, 16 to arms 13, 14. The bottom of the bell housing includes a rim 9 for stopping any condensation.

Fig. 5 illustrates the arrangement with the top bell housing 11 removed, to reveal a series of link switches 20 which sit within pockets 21. The link switches can operate substantially as disclosed in US Patent No. 6,252,187 entitled "Link Switch" the contents which are specifically incorporated by cross reference. The link switches are

utilised to provide interconnection between the sector cables as will be described hereinafter. Each pocket can include a insulating sealing cap e.g. 40 to prevent the ingress of moisture.

Preferably, 16 link switch cavities for switches are provided, one for each phase of each sector cable and one for the sector cable neutral. The link switches are mounted on a base 24 and covered by a protective cover 45.

Sector cables are attached to the arrangement 10 by means of insertion in an aperture e.g. 28. The sector cable 25, having a clamped tabbed end 26 and is inserted through an aperture with a resin seal or plug 27 during manufacture. As can be seen in the figures, each link switch interconnection includes a conductive tab arm e.g. 31 with a corresponding screw end e.g. 30 for attachment of the tabbed end of the sector cable.

Fig. 6 illustrates the preferred embodiment in assembled form with only one sector cable attached. Normally, each tab end will have an attached sector cable. Once assembled, the holes 44 are plugged and the cavity 42 is filled with resinous material. This is illustrated in Fig. 7 and Fig. 8. Fig. 9 illustrates the underside of the preferred embodiment 10. It can be seen from Fig. 7 to Fig. 9 that minimal amounts of resin are required to be used in the construction of the preferred embodiment. Each of the conductive tab arms e.g. 31 is interconnected to one end of a corresponding link switch pocket. Turning now Fig. 10, the link switch pockets are formed from two conductive blocks e.g. 50, 51 which are mounted on an insulating base plate 53. Fig. 10 shows an initial assembly and Fig. 1 1 shows a further assembly. The conductive tab portions e.g. 31 of Fig. 5 are interconnected to a corresponding base 57 of the conductive block e.g. 50 of Fig. 10 by means of a screw-bolt interconnection.

Each of the conductive blocks e.g. 51, 55 of Fig. 1 1 are, in turn, interconnected by a series of bus bars. The bus bars a screw bolted to the base of the corresponding conductive block (e.g. 58 of Fig. 11). Fig. 12 illustrates the bottom side of the plate 53 illustrating the assembly of the bus bars 60-63. Each of the bus bars is bolted e.g. 65 to the underside of the corresponding conductive block. The bus bar interconnection provides for the controlled interconnection of phases via link switches placed within corresponding pockets. The link pockets can be interconnected in phases by means of a series of busbars. The preferred embodiment can include an extra neutral busbar.

A number of alternatives are available. For example, as an alternative to crimping the ends of the sector cables, a separate clamping arrangement can be provided at the end of each tabbed end.

The preferred embodiment provides a number of advantages: -The bell housing is a simple plastic lid with a clamping bar which is much more convenient than the prior art. The fully anchored housing means it is not necessary to use a heavier bell housing of the prior art. The bottom of the bell housing includes a rim 9 for stopping any condensation. The touch safe nature of the link switches is also an advantage, as is their "capping" by caps 40. This assists in stopping condensation and tracking.

-The arrangement is much more compact than the prior art, fitting into more confined spaces, and in difficult environments.

-The preferred embodiment can be easily used for retrofitting of failed link boxes as only interconnection f the tab interconnects is required for operation. -The preferred embodiment uses a minimal amount of resin.

-The preferred embodiment also provides for a linked neutral interconnection allowing for neutral fault inspection.

-The preferred embodiment can be installed relatively quickly.

-In an alternative embodiment the link pockets can be moulded in different colors or include stickers with different colors so as to clearly identify their phase characteristics.

-The preferred embodiment also allow for the use of long keys to activate the phases where the arrangement is in a difficult to access position.

-Obviously the preferred embodiment can be created as a 2, 3, or 4 way unit depending on requirement.

The forgoing describes preferred forms of the present invention. Modifications, obvious to those skilled in the art can be made thereto without departing from the scope of the invention.