Technical Field

This invention relates to a drive for a belt conveyor, and more particularly a drive situated between the head and tail ends of the conveyor. Background Art

Conventional conveyors are driven by drives located at or near the head end or tail end, or both, of the conveyor. For very long conveyors, or conveyors required to convey material up relatively steep inclinations, as might be used in the mining industry, the belt tensions necessary, without transfer stations between separate conveyor belt lengths, to convey the material are very high requiring belts with strength ratings which are not practical and if available would

be both heavy and expensive. In addition the power requirements for the drives for such belts are also increased due to extra belt weight.

There is therefore a demand to, where possible, minimize the belt strength requirements, and also to minimize the power requirements for the drive motors. Therefore capital and running costs for the installation should be greatly reduced.

It is known from the patent literature to provide supplementary drives between the head and tail ends of such relatively long or steeply inclined conveyors, which comprise drive systems positions between the upper and lower (return) runs of the conveyor and which consists of relatively short belt conveyors driven such that their upper runs frictionally engage the underface of the upper run of the main conveyor so as to drive the upper run of the conveyor belt. Such systems have not proven to be successful in practice.

It is therefore a primary object of the present invention to provide a conveyor drive which supplements the conventional conveyor drives and which minimizes the problems associated with other supplementary drives, or which may be, in some circumstances, an alternative conveyor drive to conventional conveyor drives at the head and/or tail ends of the conveyor. Disclosure of the Invention

In accordance with the present invention, there is envisaged a conveyor drive adapted for positioning between the head and tail ends of an endless belt conveyor to drive an upper run of the conveyor via a lower run, comprising means to drive the lower run of the conveyor in the required direction and means between said upper and lower runs to transfer a proportion of drive power from the lower run to said upper run.

Preferably said drive means includes a motor driven roller drivingly engaging the lower run of the belt of the conveyor to drive it in the return direction and at least one snub pulley around which the lower run of the belt is trained before passing around said drive pulley.

Preferably said snub pulley, or at least an additional snub pulley, is coupled to means to adjust the belt tension at said conveyor drive.

The invention also envisages a belt conveyor incorporating one, or more, conveyor drives as defined above.

Preferably the belt conveyor has a main conveyor drive at the head and/or tail end thereof and said conveyor drive or drives defined above is or are supplementary thereto. Brief Description of the Drawings

One preferred embodiment of the invention will now be described with reference to the accompanying drawings, in which:

Figure 1 is a schematic side elevational view of a conveyor belt incorporating a conveyor drive in accordance with the preferred embodiment of the present invention;

Figure 2 is an enlarged side-elevational view of the conveyor drive as circled by arrow 2 in Figure 1;

Figure 3 is a cross-sectional view taken along line 3-3 of Figure 2, and

Figure 4 is a cross-sectional view taken along line 4-4 of Figure 3. Best Mode for Carrying out the Invention

Turning firstly to Figure 1 of the drawings, there is illustrated an upward inclined belt conveyor 10, which comprises a conveyor belt 11 trained around a head pulley 12 at one end and around a tail pulley 13 at the other end to form an upper, load-conveying, run 14

and a lower, return run 15. In this embodiment the elevated head end of the conveyor discharges conveyed material into a storage hopper 40 from which it is controlled to flow to a transfer conveyor 41. Either the head pulley 12 or the tail pulley 13, usually the head pulley, is coupled to a drive motor in the conventional manner to drive the conveyor belt in the direction indicated in Figure 1, or in some cases both the head and tail pulleys may be driven. Alternatively, or in addition thereto, a further conventional drive applied to the lower or return run may be utilised. As shown the various drives and support rollers may be supported by a support framework 16 having vertical support members, 17, outer longitudinal frame members 18a, inner support brackets 18b and transverse frame members 19.

With reference to all figures of the drawings, the upper run 14 of the conveyor is supported at spaced apart intervals along its length by an arrangement 20 of idler rollers, comprising a base roller 21, and with reference to Figures 3 and 4, a pair of upwardly and outwardly inclined rollers 22, to form a trough along the length of the upper run for receiving the material to be conveyed. As shown in Figure 4 of the drawings the idler roller arrangements 20 are supported by vertical roller support members 23 the upper end portions 24 of which are inwardly inclined and via support members 25 support the outermost and innermost ends of the inclined idler rollers 22 by slotted support plates 25a which receive the opposite ends of the axle for rollers 22. Each of the support brackets 25 carry an additional slotted support plate 25b which receives the adjacent end of the axle for the associated base roller 21. The vertical roller support members 23 are supported at their lower ends by the transverse frame members 19 and on the longitudinal frame members 18a by

bracing plates 27 bolted at 28 to the frame member 18a. Along the majority of the length of the conveyor, the lower run is confined and suspended within the main frame in the conventional manner, except where the supplementary drive 29, in accordance with this preferred embodiment of the invention, is situated.

Referring to Figures 1 and 2 of the drawings, the supplementary conveyor drive 29, which is situated approximately mid-way along the length of the conveyor, comprises a drive roller 30 driven by a motor (not shown), normally an electric motor, via a gear reducer or chain drive 32 and the lower run 15 of the conveyor belt is trained around the drive roller 30 so as to be driven in the required direction of the return run, and is also trained around a series of snub rollers 32, 33 and 34 whereby, with reference to the direction of movement of the lower run of the conveyor belt, the belt is trained forwardly over snub roller 32, rearwardly around drive roller 30, and forwardly around snub rollers 33 and 34.

In order to adjust for belt tension in the lower run 15, the section of the path of the belt between the two snub rollers 33 and 34 is trained around a weighted roller 35, the axle 36 of which supports a weight member 37 to provide gravity tension to the belt. Alternatively the tensioning device associated with conveyor drive 29 of the preferred embodiment of the present invention may merely comprise a cable coupled to the support for the shaft of one of the snub rollers of the conveyor, and trained over a pulley with a weight connected to the other end of the cable, whereby gravitational force will maintain, via the tensioning device and the snub roller, a constant tension in the conveyor belt. In this embodiment lower return run 15 adjacent the head pulley may also incorporate a further auxiliary drive 43 including a further tensioning device, (not shown) which may comprise a winch around

which a cable is wound and in turn coupled to a support for the shaft of one of the rollers of the auxiliary drive, whilst a tension controller, responsive to belt tension, controls the drive to an electric motor for the winch to draw the roller forwardly or rearwardly to tension or relax the conveyor belt trained therearound.

Other alternative means of maintaining belt tension can of course be utilised.

It will be apparent from the above, that the supplementary conveyor drive 29 and will drive the lower run 15 of the conveyor belt in the required direction. Apart from the power required to drive the lower run in the return direction, the remainder of the power provided by conveyor drive 29 is to be transmitted to the upper run of the conveyor belt to supplement, in this embodiment, the drive power to that run and thus supplement the power to convey the material support thereon.

With reference to all figures of the drawings the means to transmit the drive power from the drive 29 to the upper run 14 comprises a series of pressure rollers 38 spaced apart along the length of the conveyor and supported within the support frame for the conveyor by support members 39 bolted to the support brackets 18b. The series of pressure rollers extend partially along the length of the conveyor and at other points the lower run of the conveyor is supported by conventional lower run support rollers 42. The pressure rollers 38 serve to force the lower run of the conveyor upwardly against adjacent base rollers 21 of each idler roller arrangement 20 above the pressure rollers. By virtue of the upward force exerted by the rollers 38 on the lower run of the belt, and therethrough to the base rollers 21, the base rollers are caused to rotate and by virtue of the weight of the upper run of the belt and

the weight or load of any material thereon, on the upper side of the base roller 21, some of the power from the supplementary conveyor drive 29 will be transmitted to the upper run of the belt to supplement the drive power provided by the head and/or tail drives.

In practice, the conveyor drive 29 is located along the length of the conveyor at a position whereby the total power is split evenly between all drives. The base rollers 21 are covered with rubber lagging or some other high friction material such as ceramic, whilst the pressure rollers 38 are rubber discs or plain or flat lagged rollers.

As shown in the drawings, the pressure rollers are fixed and the supports for the idler roller arrangements 20, via the support member 25 and slotted plate 25b are such as to allow some freedom of vertical movement whereby the total mass of the material on the upper run of the conveyor, the belt itself and the base roller 21 will maintain contact pressure. Alternatively the position of the base roller may be fixed and an upward force applied to the pressure rollers by biasing springs. Power is transferred from the lower run 15 to the upper run 14 by the fact that as higher tensions are imparted to the lower run 15 by means of the supplementary drive 29, it is travelling marginally faster than the upper run 14. If tensions in the lower run are higher it is stretched more and so its mass per unit length is less. Because the conveyor belt is continuous then, when in steady state motion, the mass per unit time passing any point must be constant and as a result the velocity of the lower run is lightly faster than the upper run. As the top run is linked to the lower run through the base rollers 21 in contact with them, the upper run is accelerated and has power imparted to it. It is envisaged there may be some belt slippage but his can be minimized by having a relatively large number of pressure rollers 38 in the series.