THIS invention relates to a cable handling apparatus.

Electrical cables are used to supply electrical power to certain items of mining equipment, for example mining machines in coal mining operations. The electrical cables which are used typically have a diameter of 50mm or 70mm, a mass of 40kg/m or more, and may have an overall length of over 300m.

The cable is usually supplied on a wooden cable drum which has too large a diameter and which is in general too bulky to be taken underground. Common practice is to unreel the cable from the drum on surface and then to drag the cable underground by means of a tractor, typically a flame-proof tractor in the case of a coal mine, or manually. In practice, the cable is normally laid along underground roadways and tunnels. When the cable is to be moved or retrieved, it must again be dragged either to the new location or out of the mine.

A problem which is encountered is that the cable is frequently damaged, and may even break, when it is dragged from one location to another and has to pass over a rough floor or around sharp corners. Although broken cables can theoretically be repaired by means of cable joints, such joints tend to be stiff and have the effect of reducing the overall flexibility of the cable. Added to this, cable jointing and replacement can be expensive exercises. Accordingly, if a cable is damaged, it is often replaced entirely.

Certain of the problems that exist with cable handling in underground locations also exist in above ground applications, particularly where the unreeled cable has to be dragged from one location to another. In this application the cable may be buried so there may be an even greater risk of damage to the cable as it is dragged from its buried position. SUIVHV1ARY OF THE INVENTION

According to the present invention there is provided a cable handling apparatus comprising a rotatable drum onto and from which a flexible electrical cable can be wound and unwound, drum drive means for rotating the drum, at least during cable winding, about an axis of the drum, a feeder configured to feed cable onto and off the drum, in a direction transverse to the axis of the drum, during cable winding and unwinding, and feeder drive means arranged, at least during cable winding, to move the feeder lengthwise relative to the drum, in a direction parallel to the axis of the drum, at such a speed that the feeder moves a distance substantially equal to or slightly greater than a diameter of the cable for each rotation of the drum by the drum drive means.

The apparatus includes a receptacle in which the drum is rotatably mounted and which is transportable in a transport direction with the drum and receptacle being configured such that the axis of the drum extends in the transport direction. The apparatus may also includes a wheeled vehicle, preferably a trailer, for transporting the receptacle, most preferably a scissors-type trailer operable to pick up, transport and put down the receptacle. The receptacle itself may be in the form of an open-topped bin with a base and side walls, or an open frame.

In one version of the invention, the drum drive means and feeder drive means are provided on the receptacle. In another version, these components are provided on the vehicle.

Typically, the drum drive means comprises an hydraulic motor. This may be a unidirectional motor which can drive the drum in rotation during cable winding. The motor can include an hydraulic bypass allowing the drum to freewheel in the event that torque required to rotate the drum exceeds a predetermined limit. The feeder is typically arranged to move on guides extending parallel to the axis of the drum.

The drum drive means can be arranged to drive the feeder drive means. In one embodiment of this version the feeder drive means comprises a chain drive arranged to translate rotation of the hydraulic motor of the drum drive means into longitudinal movement of the feeder. In another version, the feeder drive means also comprises an hydraulic motor. In this case the feeder drive means can include a worm rotatable by the hydraulic motor of the feeder drive means and a follower carried by the feeder and meshing with the worm. It is also within the scope of the invention for the feeder drive means to take other forms, for example a rack and pinion drive.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described in more detail, by way of example only, with reference to the accompanying drawings in which:

Figure 1 illustrates a cable handling apparatus according to a first embodiment of the invention;

Figure 2 shows a partially ghosted perspective view of components of the apparatus seen in Figure 1 prior to cable winding;

Figure 3 illustrates components of a chain drive forming part of the apparatus seen in Figure 1 ;

Figure 4 shows a perspective view of components of the apparatus seen in Figure 1 during cable winding or unwinding;

Figure 5 shows a front perspective view, from above, of a cable handing apparatus according to a second embodiment of the invention; Figure 6 shows a front view of the apparatus seen in Figure 5;

Figure 7 shows a front perspective view, from below, of the apparatus seen in Figure 5;

Figure 8 shows a rear view of the apparatus seen in Figure 5;

Figure 9 shows a side view of the apparatus seen in Figure 5; and

Figure 10 shows a rear perspective view, from above, of the apparatus seen in Figure 5

DESCRIPTION OF THE ILLUSTRATED EMBODIMENT

Figures 1 to 4 illustrate a first embodiment of the invention. For clarity of illustration, the chain drive seen in Figure 3 has been omitted from Figures 2 and 4.

Figure 1 shows a tractor 10 hitched to a trailer 12 which is in this embodiment a PowerX™ - type trailer manufactured and sold by the applicant. Persons skilled in the art will be familiar with trailers of this kind, which are described in the specification of South African patent 68/6139, and will know that such trailers include a scissors mechanism that can be operated to raise, lower and transport a variety of different receptacles for various applications, for example general transportation, refuse transportation and so on.

In the illustrated embodiment, the PowerX™-type trailer 12 is shown with a receptacle, in the form of an open-topped bin 14, designed for use in cable handling operations as described below. Referring also to Figures 2 and 4, the bin 14 has a base 16 and side walls 18 and 20. The latter side wall carries an inclined upper extension 22 on which longitudinally extending upper and lower guide rails 24 and 26 are mounted.

Supported rotatably by pedestals 28 and 30 mounted on the base 16 of the bin 14 is a drum 32 having a spindle 34 and end flanges 36. The pedestal 28 also supports a drum drive means in the form of an hydraulic motor and gearbox assembly 38 arranged to drive a stub axle 40 projecting axially from the drum. Pressurised hydraulic fluid to power the motor is supplied by an hydraulic pump (not shown) which is typically mounted on the tractor 10. It will be understood that, in use, the drum 32 is driven in rotation by the hydraulic motor about the central axis of the spindle 34. It will furthermore be understood that the axis of rotation of the drum extends in the longitudinal direction, i.e. is aligned with the direction of forward or rearward movement of the tractor 10 in use.

Figures 2 and 4 also show a feeder 42 which is mounted for longitudinal movement on the guide rails 24 and 26. The feeder 42 is in the form of an open rectangular frame defining opposed cable feed openings 44, 46 surrounded by rollers 48.

Figure 3 shows a chain drive 50 which is used to drive the feeder 42 back and forth along the guide rails 24 and 26. The drive 50 includes an output sprocket (not visible in Figure 3) driven by the motor and gearbox assembly 38, the input sprocket 52 of a gearbox 54 mounted at one end of the side wall 20 of the bin 14 and a chain 56 entrained about the respective output and input sprockets. The gearbox drives an output sprocket 57. A further chain 58 is entrained about the output sprocket 57 and a further sprocket 59 mounted at the other end of the side wall 20 of the bin 14. For simplicity of illustration, only the upper run of each chain is shown in Figure 3

The chain 58 is located behind a longitudinally extending plate 60 mounted to the side wall 20. The feeder 42 is attached to the chain 58 by means of a drive arm 62. The numeral 64 in Figures 1 and 4 indicates a flexible electrical cable which has been omitted from Figures 2 and 3 in the interests of clarity of illustration. This is typically a cable of the kind mentioned at the outset. So, for example, the cable may have a diameter of 50mm or 70mm and a length of 300m or more. Figures 1 and 4 show the cable extending alongside a roadway on which the tractor 10 moves, and partially wound onto the spindle 34 of the drum 32.

The motor and gearbox assembly 38 is designed to rotate the drum 32 in one direction only when the motor is operational. This direction, referred to as the winding direction, is indicated by the numeral 66 in Figure 4.

During cable winding, i.e. during an operation to wind the cable 64 onto the drum, the tractor 10 may be stationary or it may be driven at an appropriate speed in the direction in which the cable extends along the roadway. In the former case the unwound length of cable must be pulled to the drum while in the latter case, which is generally preferred, only a relatively short portion of the cable is pulled onto the drum at each position of the tractor as the tractor advances.

During the cable winding operation, the hydraulic motor and gearbox assembly rotates the drum 32 in the direction 66 and, at same time, drives the feeder 42 longitudinally along the guide rails 24 and 26 through the action of the chain drive 50. The various sprocket and gearbox ratios are selected such that the feeder moves longitudinally by a distance corresponding to the diameter of the cable for each rotation of the drum. In practice, the feeder may move a distance slightly greater than the cable diameter to take account of local irregularities on the surface of the cable, caused for example by adhering muck or the like. For example where the cable diameter is 70mm, the feeder may move, say, 75mm for each rotation of the drum. The cable is accordingly wound onto the spindle 34 with each successive turn of the cable lying quite compactly next to the preceding turn. The small gap, if any, between successive turns means that substantially the maximum possible length of cable can be wound onto the spindle in each layer.

The feeder drive includes a reversing facility which operates automatically to reverse the direction of movement of the feeder each time it reaches a limit position at which it feeds the cable onto an end of the spindle. Thus, after one layer of adjacent cable turns has been laid on the spindle by the feeder, the feeder direction is reversed in order to lay another layer of turns over the first layer. This procedure continues until the full length of the cable has been wound onto the spindle. The required reversing facility may, for example, be provided by a suitable reverse gear in the gearbox 54 which is engaged or disengaged at each limit position of the feeder.

In order to prevent breakage of the cable in the event that it gets snagged during cable winding, the hydraulic motor or its supply will typically include a bypass valve to vent hydraulic fluid to tank in the event that the torque required to rotate the drum, corresponding to hydraulic fluid pressure, reaches a predetermined limit.

As an additional feature, a shear pin may be provided between the motor and the stub shaft of the drum which will shear in the event of excessive drag on the cable during cable winding.

During cable unwinding, the drum 32 is free to rotate. In this case, the tractor 10 will usually be driven in the cable laying direction at a speed selected for the cable to unwind from the spindle at the same linear speed. A limited slip clutch may be provided to ensure that the cable does not overwind in an uncontrolled manner and possibly become entangled or coiled.

At the commencement of a cable winding operation, the cable must be attached to the spindle in some way. It is envisaged that this could be achieved quite simply by providing a transverse opening in the spindle through which the end of the cable can be threaded. After a few turns have been drawn onto the spindle, the cable is then anchored by friction. During unwinding, the end of the cable will simply pull out of the opening when fully paid out. Alternatively, as shown in Figure 4, an end flange of the drum may have a tubular element 33 attached to it to retain a free end of the cable.

The fact that the feeder is arranged to feed the cable onto the drum in a controlled manner, as described above, allows for a maximum length of cable to wound onto and stored on the drum, for a given length of drum, without the outer diameter of the wound cable being excessive. With the overall diameter of the fully wound cable, and hence of the drum, kept at a minimum it is possible to restrict the overall height of the apparatus to a value suitable for mining applications where limited headroom is a concern.

Figures 5 to 10 illustrate a second embodiment of the invention. In these Figures, components corresponding to components of the first embodiment are designated by the same reference numerals.

The embodiment of Figures 5 to 10 includes a PowerX™ - type trailer 12 on which is mounted a receptacle 14 accommodating a cable drum 32 with a spindle 34 and end flanges 36. Whereas the corresponding receptacle 14 in the first embodiment is in the form of an open-topped bin with a base and side walls, it will be seen that the receptacle 14 in Figures 5 to 10 is in the form of an open frame.

In the embodiment of Figures 5 to 10, the feeder 42 is mounted for longitudinal movement on parallel guide rails 24 and 26 which are, in this case, supported on a support member 100 carried by the trailer 12. The feeder includes spaced apart guide plates 102 on a base plate 104 carrying rollers 106 which engage the guide rails from the inside as shown particularly clearly in the enlargement of the encircled area in Figure 7. The guide plates 102 have curved cable guide regions 108 to lead the cable (not seen in Figures 5 to 10) to and from the drum 32. The rollers 106 are mounted for rotation about vertical axes between the base plate 04 and a lower plate 110. Connected to the underside of the lower plate 110 is a bracket 112 carrying a follower 114 that meshes with a longitudinally extending worm 116 driven by an hydraulic motor 118 supported on an end plate 120 connected to the support member 100. It will be understood that when the hydraulic motor 118 is operative to rotate the worm 16, the interaction of the follower 114 with the worm causes the feeder 42 to move longitudinally on the guide rails 24, 26.

The follower 144 is typically of a diametrically split design, i.e. a split nut, enabling it to be assembled on the worm 116.

The drum 32 in Figures 5 to 10 is driven in rotation by an hydraulic motor 122 which may have features similar to those of the motor 38. The motor 122 drives an intermediate shaft 124 through a gearbox 126 and universal coupling 128 as illustrated in the enlarged view of the encircled area in Figure 5. The gearbox 126 and motor are supported on the drawbar assembly 130 of the trailer as illustrated. The shaft 124 is coupled to a drive shaft 132, seen in the enlarged view of the encircled area in Figure 9, supported by bearings 134. The shaft 124 in turn drives a sprocket 135 seen in the enlarged view of the encircled area in Figure 6. A chain 136 is entrained about the sprocket 134 and about a drum sprocket 138 mounted fast on the axis of the drum 32. It will be understood that with the hydraulic motor 122 operative, rotary drive is supplied to the drum 32 via the gearbox 126, intermediate shaft 124, drive shaft 132 and the final chain drive comprising the sprockets 134 and 138 and chain 136.

The motors 118 and 122 and associated gearing are selected such that for each rotation of the drum 32, the feeder 42 advances a distance corresponding to a cable diameter, typically equal to or slightly greater than than one diameter as in the first embodiment, so that the cable is, as before, wound neatly and compactly onto the drum. The feeder drive motor 118 is typically of a reversible design, or drives the worm through reversible gearing, such that the direction of movement of the feeder can be reversed as necessary during cable winding.

The hydraulic motors may be supplied with pressurised hydraulic fluid by a pump driven by the PTO shaft of the associated tractor (not shown in Figures 5 to 10), suitable valves being provided to split the flow of fluid appropriately between the motors. As in the first embodiment, the drum drive motor may have an hydraulic bypass to allow the drum to rotate freely during cable unwinding or if a jam or other fault results in the torque required to rotate the drum exceeding a predetermined limit. The feeder drive motor may have a similar bypass to allow the feeder to move freely during cable unwinding or in excessive torque situations.

An important feature of the invention, particularly in the context of cable winding and unwinding in an underground mine, is the fact that the drum 32 is arranged with its axis extending longitudinally, i.e. in the transport direction, as opposed to transversely. If a drum is arranged transversely its length is limited by the width of the roadway or tunnel along which the drum must be transported. A necessary consequence of a short drum is that a cable of given length, once wound onto the drum, forms a large diameter even if neatly wound. The large diameter which is described may be too great to allow the drum to be taken into a mine or manoeuvred therein. With the illustrated longitudinal orientation the drum can be made as long as is practical in the circumstances of the application, thereby limiting the overall diameter of the fully wound drum.

Bearing in mind that a cable is typically laid to one side of a roadway or tunnel in an underground mining application, it will be understood that if the drum is longitudinally oriented, as in the described embodiments, a consequence is that the cable must be wound in or paid out laterally. The potential disadvantages of this are overcome in the present example by providing the feeder 42 to guide the cable smoothly and accurately. In practice, the feeder which is used may be mounted in a freely tiltable manner so as to be able to orientate itself automatically to suit the exact direction in which the cable is being paid out or wound in. Where the feeder includes rollers, as in the embodiment of Figures 1 to 4, the rollers may have a self cleaning feature to prevent them from jamming and preventing free cable movement. The self-cleaning feature may for example include through-holes extending transversely through the roller surfaces to internal removal passages, so that dirt particles on the roller surfaces will be able to move inwardly through the roller surfaces to be conveyed away through the removal passages.

It will in any event be understood that the cable handling apparatus of the invention has the potential to reduce the chances of cable damage or breakage resulting from dragging a cable from one place to another.

It will also be understood that the operation of the described apparatus is largely automated and avoids the need for personnel to be situated close by during cable winding and unwinding. It is therefore considered that use of the apparatus will be safer than the existing methods described at the outset.

Many variations are possible within the scope of the invention. In other embodiments of the invention, not shown, the feeder chain drive of the first embodiment and the feeder worm drive of the second embodiment could be replaced by other feeder drive arrangements, for example a rack and pinion drive in which the feeder carries a pinion meshing with a longitudinal rack on the drum 32 or on the trailer 2.

In the embodiments described above and illustrated in the drawings, the drum 32 is mounted in a receptacle designed to be handled by a PowerX™- type trailer. This has the advantage that if the cable is not in use for any period of time, the receptacle can be dropped off in a storage area with the cable stored on the drum. When the cable is again required, it is a simple matter to pick up the bin again using an appropriate PowerX™ - type trailer and transport it to the required operational area for redeployment. In other embodiments of the invention, the drum 32 could of course be mounted on any other suitable trailer. In the embodiment of Figures 5 to 10, where the drive and feeder drive components are mounted largely on the trailer itself, and the trailer is accordingly dedicated to cable handling operations, the trailer itself may be left in the storage area when not required.