GB2044709A

GB2044709A - Conveyor for a Mine Working Tensioning Arrangement

Info

Publication number: GB2044709A
Application number: GB7910605A
Authority: GB
Original assignee: WINSTER ENGR Ltd
Current assignee: WINSTER ENGR Ltd
Priority date: 1979-03-27
Filing date: 1979-03-27
Publication date: 1980-10-22

Abstract

In a conveyor for a mine working, comprising an endless chain (6) extending around two sprockets (8, 10), the upper run (12) of the chain being operative to convey cut mineral from the face being worked, is a tensioning mechanism (16) which may be rendered operative to engage the lower run of the chain, to deflect the lower run from its normal path of travel, to place the lower run under tension. <IMAGE>

Description

SPECIFICATION Improvements Relating to Mining Conveyors This invention relates to conveyors used in mine workings. Conventionally such a conveyor comprises two endless chains, each extending around an associated pair of spaced sprockets to provide upper and lower runs. The upper runs of the two chains travel over a bed, on which mined mineral such as coal is loaded, and scraper bars secured to and extending between the two chains move the mineral along the bed as the chains are caused to travel along the bed by rotation of the sprockets.

Alternatively, a single endless chain may be used, extending generally centrally of the conveyor, with the scraper bars secured to the chain at spaced intervals, at a position centrally of the scraper bars.

A problem is encountered when, due to continual use, and due to high load which is applied to the chains, they become stretched.

Since the upper run of the chain is usually under a high load, surplus chain accumulates in the lower run, and this can be hazardous. It is therefore necessary, at regular intervals to shorten the chains by removing therefrom one or more links.

Conventionally this is effected by stalling one of the sprockets associated with the chain, and slowly rotating the other of the sprockets in the normal operative direction, to tension the lower run of the chain and to deposit all the surplus chain on the upper run. The upper run of the chain may now be broken, and one or more links removed, and the free ends of the chain joined together.

This is not wholly satisfactory, since by using this method alone, it is only possible to tension the lower run of the chain. Thus in carrying out the method above described, it is conventional practice to use mechanical means to pull the free ends of the broken chain together, to enable them to be joined under some tension. It is however for practical purposes difficult or impossible to apply to the upper run of the chain using this method the tension which will be applied to the chain during normal operation thereof, and for practical purposes it has been normal practice to accept some slack in the upper run of the chain, subsequent to the operation of link removal.

Due to the inability of applying to the whole of the chain the load to which it will be subjected during operation, it is for practical purposes impossible to shorten the chain to an extent as would entirely remove slack, and this necessitates that a chain tensioning operation be carried out on the conveyor at relatively frequent intervals.

According to this invention there is provided a conveyor for a mine working in which an endless flexible linear element extends around rwo spaced, direction-reversing elements to afford upper and lower runs, the conveyor comprising a tensioning mechanism interposed between the two direction reversing elements and which is movable between an operative condition in which it places the lower run under tension and an inoperative condition in which it does not place the lower run under said tension.

Normally, the endless flexible linear element will be provided by a chain, and the directionreversing elements will be provided by sprockets, in which context the invention will hereinafter be described. In the use of the conveyor, it is possible to tension the chain in the conventional manner, whilst the tension mechanism is in its inoperative position. Subsequent to the removal of one or more links from the upper run of the chain, and resumption of operation of the drive sprockets, the tensioning mechanism will be rendered operative conveniently to an extent which compensates at least in part for the inability of the mine operative, whilst removing a link in the chain from the upper run, to place the upper run under tension, or under the amount of tension which is supplied to the upper run during normal operation of the conveyor.

By the use of this invention, it is possible to dispense with the mechanical means which is utilised to apply some tension to the upper run of the chain, during a normal link removal operation, whilst removing sufficient slack from the chain to maintain safe working conditions.

Conveniently the tensioning mechanism when in its operative condition, applies a predetermined tension to the lower run. Thus, where the tensioning mechanism comprises at least one tensioning member which, when the tensioning mechanism is in its operative condition is in an advanced condition in which it increase the distance of travel of the chain between the two sprockets on the lower run, the extent of the increase in said distance of travel may itself increase, during gradual stretching of the chain over a period of use. Thus, the tensioning mechanism may to some extent at least be continuously compensating for stretch in the chain.

Conveniently the tensioning member is in the form of tensioner sprocket over which the lower run of the conveyor chain extends, the tensioning mechanism comprising a fluid operated device which when the tensioning mechanism is in its operative condition urges the tensioner sprocket towards its advanced position. Associated with the tensioner sprocket there is advantageously provided two fixed idler sprockets, which limit the extent of the deformation of the chain from its lower run on opertion of the tensioner sprocket.

Alternatively the tensioning mechanism may comprise two linked sprockets, the link being rotable about an axis extending at right angles to the lower run so that both sprockets engage the chain, or engage the chain to a greater extent, to increase the distance of travel of the chain between the two sprockets on the lower run. In such a construction, conveniently fluid operating means would be provided to rotate the said link, to cause the tensioning mechanism to apply a desired tension to the lower run of the chain.

Where the conveyor comprises two continuous chains extending side by side, each link passing around to associated sprockets, the chaintensioning mechanism will comprise two chain tensioning devices, one being associated with each of the chains, and which may be moved simultaneously to their respective advanced positions.

By the use of this invention, it is possible to decrease the frequency at which an adjustment to the number of links in the chain is necessary.

This invention also provides a method of operating a conveyor for a mine working, which is effective to reduce the frequency at which surplus chain is removed from the upper run, said method involving the use of tensioning mechanism which, when in an operative condition, increases the distance of travel of the conveyor chain between the drive sprockets on the lower run, said tensioning mechanism being rendered inoperative whilst surplus chain is being removed from the conveyor, and being rendered operative during operation of the conveyor.

There will now be given detailed descriptions, to be read with reference to the accompanying drawings, of two conveyors for a mine working, which are embodiments of this invention and which have been selected to illustrate the invention by way of example.

In the accompanying drawings: Figure 1 is a schematic view of the conveyor which is the first embodiment, illustrating the conveyor during normal working thereof; Figure 2 is a view showing the condition adopted by chain tensioning mechanism, during an operation of the removal; Figure 3 illustrates the conveyor, on resumption of normal operation; Figure 4 illustrates a chain tensioning mechanism of a conveyor which is the second embodiment of this invention.

The conveyor which is the first embodiment of the invention comprises an endless chain 6, which extends around drive sprockets 8, 10 to afford upper and lower runs 12, 14. The conveyor comprises chain tensioning mechanism afforded by a chain tensioning device, comprising a fluid operated piston/cylinder device 16, to the piston of which a tensioner sprocket 1 8 is secured.

Mounted on either side of the device 1 6 are fixed idler sprockets, 20, 22.

During normal operation of the conveyor illustrated in figure 1 , the tensioner sprocket 1 8 will be moved by the device 1 6 to an advanced position, in which it deforms the lower run 14 of the chain, effectively increasing the distance of travel of the chain on said lower run, the sprockets 20, 22 maintaining the chain in an effective straight line from sprockets 8 and 10, respectively.

As the chain 1 6 stretches during continued use under load, the device 16, operating under generally constant fluid pressure, will slowly increase the extent of deformation of the lower run 14, until a maximum permissible deformation is reached. At this stage, it becomes necessary to remove one or more links from the chain 6.

To do this, the sprockets 8 and 10 are declutched, and the sprocket 8 is locked against rotation. Simultaneously, the chain tensioning mechanism afforded by the device 1 6 and sprocket 1 8 is moved to an inoperative condition, as illustrated in figure 2. The sprocket 10 is then rotated slowly, in its normal operating direction as indicated by the arrow in figure 2, to take surplus chain from the lower run 14 and deposit it on the bed 4 of the conveyor. The chain is now broken at the upper run, and one or more links are removed from the chain, and the free ends of the chain are rejoined. It will be appreciated that at this stage, the lower run 14 is substantially straight between the sprockets 8 and 10, and under tension due to the rotation of the sprocket 10.

Subsequent to rejoining of the ends of the upper run of the chain 6 (which may but not necessarily be accomplished by a mechanical tensioner to apply some tension to the upper run of the chain) normal operation of the conveyor is recommenced. Subsequently, the fluid operated device 1 6 is powered, causing the chain tensioner sprocket 1 8 to move into contact with the lower run 14 of the chain, at a position generally between the idler sprockets 20, 22. In all probability immediately subsequent to the removal of a link as carried out above, the tension in the lower run 14 of the chain will be such that only minimum distortion of the run 14 between the two sprockets 20, 22 will be effected by the device 1 6. However, as the chain 6 continues to stretch under continued use, and as more and more surplus chain is created consequent upon such stretching, the extent of the sprocket 1 8 between the sprockets 20 and 22 will increase, increasing the distance of travel of the chain between the sprockets 8 and 10, and effectively maintaining the chain 6 under a generally constant tension, notwithstanding the constant stretching of the chain 6.

In figure 4, a chain tensioning mechanism which forms part of a conveyor which is the second embodiment of this invention is illustrated, said tensioning mechanism comprising sprockets 30, 32 which are secured together on a link 34. The lower run 14 of the chain 6, as it passes between the sprockets 8 and 10, extends around the sprockets 30 and 32 as illustrated.

The chain tensioning mechanism which forms part of the second embodiment comprises a fluid operated motor operative to rotate the link 34 in the direction indicated by the arrows, again to effect an increase in the distance of travel of the chain between the sprockets 8 and 10 on the lower run 14 thereof. In the same way as described in the first embodiment, the device illustrated in figure 4 can be utilised to place the lower run of the conveyor chain under tension, to compensate to some extent at least for the continual stretching of the chain under normal operating conditions.

By the use of both embodiments, the frequency at which surplus chain is required to be removed from the upper run may be reduced, without the accummulation to any significant extent of slack chain on the lower run during operation of the conveyor.

Claims

1. A conveyor for a mine working in which an endless flexible linear element extends around two spaced, direction-reversing elements to afford upper and lower runs, the conveyor comprising a tensioning mechanism interposed between the two direction reversing elements and which is movable between an operative condition in which it places the lower run under tension and an inoperative condition in which it does not place the lower run under said tension.

2. A conveyor according to claim 1 wherein the endless flexible linear element is provided by a chain, and the direction-reversing elements are provided by sprockets.

3. A conveyor according to claim 2 wherein, when in its operative condition, the tensioning mechanism applies a predetermined tension to the lower run.

4. A conveyor according to claim 2 wherein the tensioning mechanism comprises at least one tensioning member, which when the tensioning mechanism is in its operative condition is in an advanced position in which it increases the distance of the travel of the chain between the two sprockets on the lower run, and which when the tensioning mechanism is in its inoperative condition does not so increase the length of said run.

5. A conveyor according to claim 4 wherein the tensioning member is in the form of a tensioner sprocket over which the lower run extends, the tensioning mechanism comprising a fluid operated device which when the tensioning mechanism is in its operative condition urges the tensioner sprocket towards its advanced position.

6. A conveyor according to claim 5 comprising two fixed idler sprockets one on either side of the tensioner sprocket, said idler sprockets limiting the extent of the deformation of the chain from its lower run on operation of the tensioner sprocket.

7. A conveyor according to claim 2 wherein the tensioning mechanism comprises two linked sprockets, the link being rotatable about an axis extending at right angles to the lower run so that both sprockets engage the chain, or engage the chain to a greater extent to increase the distance of travel of the chain between the two sprockets on the lower run.

8. A conveyor according to claim 7 comprising fluid operating means to rotate said link.

9. A method of operating a conveyor for a mine working, which is effective to reduce the frequency at which surplus chain is removed from the upper run said method involving the use of tensioning mechanism which, when in an operative condition, increases the distance of travel of the conveyor chain between the drive sprockets on the lower run, said tensioning mechanism being rendered inoperative whilst surplus chain is being removed from the conveyor, and being rendered operative during operation of the conveyor.

10. A conveyor for a mine working, constructed and arranged substantially as hereinbefore described with reference (b) to figures 1, 2 and 3 or (b) to figure 4 of the accompanying drawings.

11. A method of operating a conveyor in a mine working, when carried out substantially as hereinbefore described with reference to the accompanying drawings.