Background of the Invention During mining operations it is necessary to protect a variety of electrical cables, water hoses and other service lines from damage. One particular area where line protecting apparatus is required, is in the area of coal mining, particularly in longwall coal mining in which a coal cutter traverses back and forth across a coal face depositing coal cut from the coal face into a conveyor disposed behind the coal cutter. In order to operate, the coal cutter requires a supply of water and electricity which are provided by service lines. The service lines are located in a trough which is typically disposed on the opposite side of the conveyor from the coal cutter and the lines travel up and down the trough as the coal cutter moves up and down the coal face. It should be noted however, that whilst the type of apparatus envisaged by the present invention is particularly suitable for use in handling and protecting service lines for longwall coal mining, it will be appreciated that other applications of the apparatus are possible.

In order to protect such service lines it is known to enclose, or at least partially enclose them in a protective articulated cable handler formed from a link or plurality of interconnected links. US 4988838 discloses one such cable handler formed from a plurality of interconnected links. Each link has a central web forming a common base for a pair of laterally open channels on respective sides of the central web. For at least some of the links, each channel is formed with a inwardly extending nib so that the entrance to the channel is narrower than the width of the channel. Each link is formed from a plastics material typically nylon so that the channel sides are resiliently flexible and a service line can be inserted into a respective one of the channels by deflecting walls of the channel and the nibs apart. After a service line is passed through the channel entrance, the channel sides return back to regain their original position and thus prevent the line from inadvertently moving out of the channel. The links are joined by linking the central web of one link to adjacent links hence such cable handlers are referred to as"centre pull"cable handlers.

PCT/GB95/00384 discloses a development of the apparatus shown in US 4988838 in which the web is located to one side of the link instead of being centrally

located, and the channel is approximately twice the depth of the centre pull design.

This type of cable handlers is referred to as a"side pull"cable handler as the links are articulated via the side web and are pulled along one side.

One problem which is common to the cable handlers of both US 4988838 and PCT/GB95/00384 results from the presence of stones, flints and the like in the trough along which the cable handler runs. These flints and stones are often narrower than the channel entrance and they can enter the channel and may puncture the water hose or electric cable interrupting the supply of power or water to the coal cutter and disrupting production. Further, the type of heavy duty cables used in underground mining are expensive, particularly the electric cables. The cost of replacing any damaged cables, is high, such that in some environments, mining operators will not use cable handlers of the type described in US 4988838 because of the potential for damage to the service lines.

To avoid this problem twin pull cable handlers have been developed and are currently used at many longwall operations, particularly in the USA and the UK. In a twin pull cable handler, each link defines a generally rectangular shaped box in which the electric cable and water line are located. A removable plate or plates are bolted or otherwise fixed to the tops of the side walls of the rectangle, thereby locking the cables in the U shaped link. The base side walls and plate are all solid providing all round protection for the electric cable and water line. The links may be linked/pulled from either or both sides, and are typically pulled from both sides, hence the name"twin pull". However, whilst such a twin pull design provides a high degree of protection for cables, it will be appreciated that it is an extremely lengthy, tedious and time consuming process to install a pair of lines in a twin pull cable handler compared to a centre pull cable handler such as in US 4988838 or a side pull cable handler because of the need to attach a plate to each link in turn. For a typical long wall mine which might require a cable handler which is many metres long, this may take much time and result in loss of operating time. There is also the risk of the bolts, clips or the like securing the plates to the channels, becoming loose and separating from the channel. It will also be appreciated that because the links have to be articulated to allow the cable to fold back upon itself, as the coal cutter traverses up and down the coal face, that however the cable handler is designed, it is impossible to totally enclose the cables in a cable handler which is made of articulated rigid protective elements as gaps are required between links to allow articulation.

It is an object of the present invention to provide a line protecting apparatus which approaches the level of line protection afforded by a twin pull cable handler but

which retains the advantages of the flexible cable handlers such as is described in US 4988838 in the ease of loading the line into the cable handler. As a consequence of the absence of loose plates, springs, clips, dowels or the like which make loading the lines into the cable handlers more time consuming and increase the risk of springs, clips dowels or the like becoming shaken loose from the cable handler in use.

Any discussion of documents, acts, materials, devices, articles or the like which has been included in the present specification is solely for the purpose of providing a context for the present invention. It is not to be taken as an admission that any or all of these matters form part of the prior art base or were common general knowledge in the field relevant to the present invention as it existed in Australia before the priority date of each claim of this application.

Summary of the Invention In a first broad aspect, the present invention provides apparatus for protecting cables, service lines and the like in the form of a chain link a means defining a channel for receiving at least one service line, said channel having a first end wall, two opposed side walls integral with said first end wall defining free ends each of the side walls being generally flexible characterised in that first engaging formations are defined on the free ends of the side walls and in that a second end wall defining second engaging formations adapted to engage with the first engaging formations is provided, engagement between the first and second engaging formations being enabled by flexing of the side walls to securely engage the second end wall between the side arms engagement of the receiving formations preventing movement of the second end wall relative to the side walls absent flexure of the side walls, and wherein at least one of the end walls is provided with pivotal formations to enable the chain link to be pivotally connected to a similar link to form a chain.

It is preferred that both of the end walls are provided with pivotal formations to enable the chain link to be pivotally connected to a similar link to form a chain of the twin pull type.

The present invention has a number of substantial advantages over prior art cable handlers.

The first advantage is that no springs, clips, dowels or the like are required to retain the side plate to the chain link and the link itself may comprise only two parts, namely the means defining a channel and the second end wall.

Further, the fact that both of the side arms are flexible and that the side plate is separable from each side arm, makes removal of the side plate straightforward and

simple regardless of the orientation of the chain link. The flexibility of the side walls makes it easier to clip the side plate into the side walls, no pins or clips are needed.

Both the means defining the channel and the second end wall are typically moulded in nylon over a steel plate defining the pivotal formations in the form of apertures for receiving a link pin or the like for joining adjacent chain links.

This provides a further advantage in that the chain link also provides a basic integrity since removal of the side plate does not affect the integrity of the connection between the side walls and the first end wall as in prior art twin pull cable handlers.

Preferably the first engaging formation is in the form of a nib extending away from each of the side walls generally parallel to the first integral end wall such that the entrance of the channel is narrower than the width of the channel Thus the projecting nibs prevent egress of the cable from the cable handler in the event that the side plate is removed or comes detached from the cable handler, in contrast with the prior art twin pull handlers wherein if the side plates become detached, the cables may fall out from the chain link.

It is also envisaged that a side plate without any pivotal connections can be inserted to existing centre pull and side pull designs for added protection and for the other benefits described above.

Brief Description of the Drawings A specific embodiment of the invention will now be described by way of example only and with reference to the accompanying drawings in which: Figure 1 is a top view of a chain link embodying the present invention; Figure 2 is a front view of the chain link of Figure 1 ; Figure 3 is a bottom view of the chain link of Figure 1 ; Figure 4 is a view of a detachable end plate of the chain link of Figure 1 ; Figures 4A and 4B are sections on B-B and C-C respectively of Figure 4; Figure 5 is a section on A-A of Figure 1 ; Figure 6 is a similar view to Figure 2 but showing the link open; Figures 7A and 7B are enlarged views of section B-B showing the link open and closed respectively; Figures 7C and 7D are enlarged views of section C-C showing the link open and closed respectively; Figure 8A is a front view of a side pull chain link embodiment of the invention; Figure 8B is a section on A-A of Figure 8A;

Figure 9A is a front view of a centre pull chain link embodiment of the invention; and Figure 9B is a section on A-A of Figure 9A.

Detailed Description of a Preferred Embodiment Referring to the drawings a line protecting apparatus or chain link 10 which forms one link of an articulated chain to be described below is shown. The chain link comprises two parts a generally U-shaped channel element 12 and a detachable end wall or plate 14. The U-shaped channel element 12 defines an end wall 16 and two identical opposed side walls 18,20 integral with the end wall, and defining free ends 18A, 20A. The channel element is formed from a moulded plastics material such as high viscosity nylon incorporating a steel insert 22 to provide additional strength and to provide linkage means. The side walls are not reinforced and are generally flexible.

As is best seen in Figure 5, the steel insert 22 comprises two parallel cranked linkage elements and at one end 30 defines a through aperture 32, and at the other end 34 defines two parallel arms 36 which define co-axial apertures 38. The relatively narrower portion 30 of one insert 22 can be inserted between the arms 36 of an adjacent insert and the inserts linked together with a bolt or other suitable means passing through apertures 32 and 38.

The detachable end wall or plate 14 is similar in design to the end wall of the U- shaped channel element in that it is formed from a moulded plastics material typically high viscosity nylon incorporating a steel insert of substantially the same shape and design as insert 22 of the end wall 16 to provide additional strength and to provide linkage means. Thus when the end wall 14 is attached to the channel means as shown in Figures 2 and 5, a twin pull chain link is defined.

The means for attaching the second end wall 14 to the channel means comprise first engaging formations in the form of three projections 60,62 and 64 extending away from the free ends 18A, 20A of each side wall generally perpendicular to the side wall and parallel to the end wall 16. The projections engage in mating recesses 66,68 and 70 defined in the top and bottom ends of the second end wall 14. As is best seen by viewing Figures 4,6 and 7A to 7D, the middle projection 62 and middle recess 70 are longer and deeper respectively than the outer two projections/recesses 60,62, 66,70, which are substantially identical. Also when viewed from the side as shown in Figure 6 the two outer projections are aligned parallel to but not co-axial with the inner projection 64.

As seen in Figure 1, the chain link 26 defines two parallel edges 70,72, a convex end 74 and a concave end 76. When the individual units are linked together the concave end 76 of one link locates adjacent and faces the convex end 74 of the adjacent link in the chain and the facing curved surfaces allow the links to rotate relative to each other about the pivot axis 78 of the link without the side walls 74,76 interfering with one another. The provision of the curved ends 74 and 76 allows the gaps between adjacent links to be smaller than if the side wall were rectangular., In use, the end wall 14 is detached from the channel element 12 by flexing either side wall 18 or 20 and removing one set of projections from the recesses in one end of the side wall. Because both side walls are flexible this allows access to the interior of the link whichever way up the link is oriented. This is important as when the cable is to be accessed in a mine the chain link is removed from a trough and typically supported on a board resting on the top of the trough and only the uppermost side will be able to be readily flexed. Cables in the line protecting apparatus can then be removed or inserted as necessary before the end wall 14 is replaced.

A water line 100 is first inserted in the channel followed by a relatively larger electric cable 102. The electric cable is sufficiently large in diameter to be retained in the channel by the projections 62.

The size and strength of the nylon projections and recess and in particular the cross sectional area of the projections is sufficiently large for the end wall 14 to take the same load as the other end wall before failure.

It is also envisaged that a side plate 100 without any pivotal connections shown in Figures 8A and 8B can be connected to the channel element 12 or to existing centre pull designs of line protecting apparatus. Whilst this does not enable the line protecting apparatus to be twin pull it does provide substantial added protection which is relatively easy to remove, if required. A centre pull variant is shown at 120 in Figures 9A and 9B.

It will be appreciated by persons skilled in the art that numerous variations and/or modifications may be made to the invention as shown in the specific embodiments without departing from the spirit or scope of the invention as broadly described. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive.