DESCRIPTION

This invention relates to endless belts and is especially likely to find application in the so-called twin-grip caterpillar haul-offs by which long, flexible materials such as cable or hose may be driven from a source.

For the handling of such materials, it has been proposed that a pair of endless belts should be used, the belts running face-to-face and synchronously through a reach in which the material is gripped by, and between, the belts and thus drawn forward by them. Conveniently, each belt may be driven by the co-operation of teeth dis¬ tributed along its length with one, or both, of the end drums over which the belt passes. Whilst the use of such an arrangement can ensure that the belts are positively driven and, by control of the drums, move in synchronism, it may be desirable to incorporate additional means to promote a good gripping relationship between the belts and the material being drawn throughout the reach. Such additional means may be provided by use of the present invention.

According to the present invention there is provided an endless belt and means by which pressure acting inwardly may be resisted throughout a reach of the belt, the inner surface of the belt being provided throughout its length with inwardly projecting teeth through which the belt is driven and there being within the ambit of the belt a

subsidiary endless belt of which the outer surface is provided throughout its length with teeth that mesh throughout the reach with teeth of the mainbelt, and resilient means acting on the subsidiary belt throughout the reach to urge the teeth of the subsidiary belt into engagement with the teeth of the main belt and resist inward movement of the belts throughput the reach.

By way of example an embodiment of the invention will now be described with reference to the accompanying drawings in which ,

Figure 1 illustrates, somewhat diagramatically, a longitudinal side view of a caterpillar haul-off apparatus;

Figure 2 illustrates in more detail a section of Figure 1 on the line II-II of Figure 1; and

Figure 3 shows the right-hand end of a section on the line III-III of Figure 2.

In the caterpillar haul-off apparatus shown in Figure 1, there are two units 1 that are essentially similar to each other. ""They extend lengthwis.e between two tubular structures 2, with the lower unit upside-down relatively to the upper unit but with a parallel space between them. The structures 2 are connected together at their ends by circular end walls 2a and the units are mounted on the end walls 2a in such a way that the vertical separation between them can be varied. Control apparatus by which this can be effected is indicated broadly at C.

Each unit 1 includes two parallel side plates 3, connected together by a hollow central core 3a, that extend for the whole of the length of the units. Between the plates there runs an endless belt 4 having an external coating 5. T e hose or cable to be hauled-off from a source (not shown) to the left of what is shown

in Figure 1 is gripped throughout the reach from A to B, between the two belts 4; the external coating 5 serves to provide a good grip with what is being hauled.

The inner surface of each belt 4 is provided on its inner face with teeth 6 which extend perpendicular to the direction of travel across the entire width of the belt 4. At the right hand end of the unit 1, the belt passes over a driving roller 8, the' teeth 6 engaging with correspond¬ ing recesses 9 in the outer surface of the roller 8. The roller 8 is itself driven by an electric motor 10.

At the other end, 'the belt 4 passes over an idling roller 11 and tension in the belt 4 is maintained by springs 12 acting between the axis of the idling roller 11 and fixed anchors on the side plates 3. To ensure that the hose or cable is drawn off efficiently without slippage, means is provided to exert a pressure from the inside of the belt 4 of each unit on to the hose or cable that is gripped between them. This means includes, for each unit, the subsidiary endless belt 15, of the same width as the main belt 4, that runs inside themain belt 4. The outer surface of the sub¬ sidiary belt 15 is provided with teeth 6a that co-operate along the effective run of the belt 4 i.e. the lower run of the upper unit 1 and the upper run of the lower unit with the teeth 6 as the sole means by which the belt 15 is driven. At each end, the belt 15 runs over flanged rollers 16. Tension to the belt 15 is applied by springs 17 fixed to unit 18 on which the rollers 16 are mounted and anchored to the side plates 3. Throughout the reach from A to B in which the hose or cable is fixed, there is. a sequence of rollers 20 extending across, and.acting on, the inner surface of the subsidiary belt 157 Each roller 20 has an axle 21

of which the ends are received in blocks 22 that can reciprocate vertically to some extent in channels 23 defined by the side plates 3. On each block 22 there acts a spring 26 of which the end remote from the block 22 abuts a shoulder formed on the hollow central core 3a. The rollers 20 thus exert a pressure on the main belt 4, through the subsidiary belt 15.

The blocks 22 each carry the vertical axis about which a roller 30 rotates. The rollers 30 abut the edges of the belts 4 and 15 and serve to prevent wander through¬ out the operation run. To act against wander during the return run, and to prevent outward housing, flanged rollers 32 act on the top and sides of the belts 4 and 15. It will be realised that the two motors 10 are synchronised so that the belts 4 move at identical rates. Since the teeth6 and 6a extend across the width of both the main and subsidiary belts, the engagement of the teeth produces considerable transverse rigidity in the belts 4 and 15 and. this..is especially valuable when the material being drawn is subject to tangential as well as longitudinal force e.g. when the material is a hose or cable covered with transversely laid strands or tapes. These will exert a transverse force and the teeth help tomake the belt stiff enough laterally for these forces not to cause buckling ofthe belt.

In a modification of the haul-off that has been described, the framework 2,2a may be mounted so that it can rotate about the axis of the material passing through the reach to impart a twist to the material. As the framework twists, the flanged rollers 32 that prevent the return runs of main belts from bowing outwards became especially valuable.

It is also envisaged that a haul-off may be provided with three units, such as has been described, with the belts not transversely parallel but inclined at 120° to each other.