GB2050281A - Belt tensioning device - Google Patents

Abstract

A conveyor belt tensioning device 1 comprises a tensioning drum 7 around which the belt 2, 5 to be tensioned is adapted to be looped, a ballast weight 13 operative on the tensioning drum 7 to induce tension in the belt 2, 5, a balance weight 20 operable on the tensioning drum 7 to provide a force on the tensioning drum 7 acting in the opposite direction to that effected by the ballast weight 13, and stop means 17, 18, 19, to limit uncontrolled descent of the ballast weight 13, the tensioning drum 7 being suspended by the balance weight 20 when the ballast weight 13 reaches the extreme position defined by the stop means 17, 18, 19 upon breakage of the belt 2, 5. <IMAGE>

Description

SPECIFICATION Belt tensioning device This invention relates to a belt tensioning device for a belt conveyor for handling coal, coke, iron ore, sand etc., and to a belt conveyor incorporating such a device.

Belt tensioning devices, which ensure that adequate tension remains in the belt under varying conditions of load from empty to fully loaded and varying driving forces, usually incorporate a ballast weight to effect tensioning via a drum, around which belt is looped and from which the ballast weight is suspended. On occasion, however, breakage of the belt occurs, sometimes at a joint and sometimes within the fabric of a belt, resulting in the uncontrolled fall, under gravity, of tensioning drum and ballast either to the floor of a building, e.g. a transfer tower, or to the ground.Provided these items are located near ground level, little material damage is effected, although of course it is necessary to fence off the area beneath for the safety of personnel, but it is not uncommon for these items to be located in a building art a substantial height from ground level.

Upon belt breakage then occuring, the tensioning drum and ballast weight fall to the nearest floor of the building which may be adequate to halt their fall but the impact involved usually imposes loads sufficient to damage the floor or even shear beam connections, if the building is of structural steelwork, resulting in the tensioning drum, the ballast weight and further debris continuing their descent to the next floor or to the ground below.

The object of the present invention is to provide a conveyor belt tensioning device whereby belt breakage will not result in damage to a building etc., due to the uncontrolled fall ofthetensioning drum and ballast weight.

According to the present invention, a conveyor belt tensioning device comprises a tensioning drum around which the belt to be tensioned is adapted to be looped, a ballast weight operative on the tensioning drum to induce tension in the belt, a balance weight operable on the tensioning drum to provide a force on the tensioning drum extending in the opposite direction to that effected by the ballast weight, stop means to limit uncontrolled descent of the ballast weight, with the tensioning drum being suspended by the balance weight when the ballast weight reaches the extreme position defined by the stop means upon breakage of the belt.

Thus, uncontrolled fall of the tensioning drum is prevented by the action of the balance weight which becomes operational after the ballast weight has engaged the stop means and is therefore unable to exert any further downward loading on the tensioning drum. The distance of the stop means from the operational position of the ballast weight is ideally the minimum commensurate with movement of the balance weight to effect satisfactory belt tensioning, thereby limiting to a minimum the kinetic energy attained by the ballast weight upon belt failure.

With such a device providing limited fall of the ballast weight and fall avoidance of the tensioning drum, it is possible to install the device in buildings whose floor strengths were not previously adequ ate or with less floor damage risk than previously.

Preferably, the ballast weight is connected to the tensioning drum by one or more wire ropes, either directly orthrough a roller system, and located slightly above ground level, so as to preclude positively floor damage and/or deformation. With this preferred arrangement, the stop means can conveniently consist of a pit of sand, gravel etc. In detail, the ballast weight is preferably supported by a carrier frame to which the wite rope(s) is attached, slidable in vertical guides and located just above ground level at an operational height only slightly greater than the distance required for the ballast weight to move before the balance weight becomes operational.

Preferably, the tensioning drum is carried by a framework slidably mounted in vertical guides so that in service, the tensioning drum may move up or down these guides to provide a belt tension in accordance with the magnitude of the ballast weight.

By means of at least one pulley, a wire rope from the balance weight may be connected to the top of the tensioning drum framework. It follows that the mass of the balancing weight needs to exceed slightly that ofthetensioning drum and its framework.

The invention will now be described in greater detail, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a side elevation of a belt tensioning device in accordance with the present invention; and Figure 2 is an end elevation of Figure 1.

In the drawings, a tensioning device 1 for a conveyor belt 2 is located within a building having vertical columns 3 (one only shown) and horizontal floor elements 4. The conveyor belt 2 illustrated is in fact the return run in contrast to the conveying run (not shown) and a loop 5 is formed in the belt between rollers 6 secured to an upper floor element 4 and a tensioning drum 7 located beneath the upper floor element 4 and within the belt loop 5. The tensioning drum 7 is rotatably carried in a framework 8 slidably mounted in vertical guides 9 secured to a lower floor element 4.The area occupied by the framework 8 and guides 9 is surrounded by a cage 10 comprising stanchions 11 and wire mesh 12 to preclude access to the zone beneath the framework 8, while the distance A (Figure 2) between the underside of the framework 8 and lower floor elements 4 is such as to accommodate the maximum amount of framework movement likely to be encountered to maintain satisfactory belt tension in any loading/drive condition of the belt 2.

A ballast weight 13, of magnitude sufficient to provide satisfactory tension in the belt 2 at all load conditions, is mounted in a carrier frame 14 slidable within vertical guides 15 and connected by a wire rope 16 to the framework 8 so that in service, the framework 8 and hence the tensioning drum 7 may readily move up or down the guides 9 to provide a belt tension in accordance with the magnitude of the ballast weight 13, and to a lesser extent its carrier frame 14. Attheir lower ends, the vertical guides 15 terminate in a stop means constituted by a gravel pit 17 located at ground level 18 and confined by concrete walls 19. The distance B (Figure 2) between the underside of the carrier frame 14 and the gravel pit 17 slightly exceeds that necessary to accommo date movement of the carrier frame 14 to achieve satisfactory belt tension.

A balance weight 20, of magnitude slightly in excess of the total weight of the tensioning drum 7 and its framework 8, is supported by a carrier frame 21 slidable with respect to vertical guides 22 also terminating in the pit 17. The area occupied by both the ballast weight 13 and the balance weight 20 is surrounded by a cage comprising stanchions 23 and wire mesh 24 to preclude access to the area beneath the ballast weight 13. The balance weight 20 is connected to the framework 8 by a wire rope 25 passing over a first pulley 26 and a second pulley 27 both mounted on the upper floor elements 4.

In use, should the belt 2 break, the ballast weight 13 and carrier frame 14, and with them the tension ing pulley 7 and its framwork 8, will then fall, while simultaneously the balance weight 20 and its carrier frame 21 will be raised, but only by the distance B, for upon striking the gravel pit 17, the ballast weight 13 becomes ineffective, thus leaving the balance weight 20 and its carrier frame 21 suspending the tensioning drum 7 and its framework 8.

Claims (7)

1. A conveyor belt tensioning device comprising a tensioning drum around which the belt to be tensioned is adapted to be looped, a ballast weight operative on the tensioning drum to induce tension in the belt, a balance weight operable on the tensioning drum to provide a force on the tensioning drum extending in the opposite direction to that effected by the ballast weight, stop means to limit uncontrolled descent of the ballast weight, with the tensioning drum being suspended by the balance weight when the ballast weight reaches the extreme position defined by the stop means upon breakage of the belt.

2. A device as claimed in Claim 1, wherein the ballast weight is connected to the tensioning drum by one or more wire ropes, either directly or through a roller system, and located slightly above ground level, so as to preclude positively floor damage and/or deformation.

3. A device as claimed in Claim 2, wherein the stop means consists of a pit of sand, gravel etc.

4. A device as claimed in Claim 2 or Claim 3, wherein the ballast weight is supported by a carrier frame to which the wire rope(s) is attached, slidable in vertical guides and located just above ground level at an operational height only slightly greater than the distance required for the ballast weight to move before the balance weight becomes operational.

5. A device as claimed in any preceding Claim, wherein the tensioning drum is carried by a framework slidably mounted in vertical guides so that in service, the tensioning drum may move up or down these guides to provide a belt tension in accordance with the magnitude of the ballast weight.

6. A device as claimed in Claim 5, wherein by means of at least one pulley, a wire rope from the balance weight may be connected to the top of the tensioning drum framework.

7. A conveyor belt tensioning device substantially as hereinbefore described with reference to the accompanying drawing.