GB2189757A - Improvements relating to tensioning devices for use with chain conveyors - Google Patents

Abstract

It is necessary in chain type conveyors to keep the chain under an optimum tension and preventing sudden surges while at the same time ensuring that the chain stripper/cleaner bar is kept in close proximity to the return wheels. The bearing housing 7 is capable of sliding movement relative to conveyor structure by means of longitudinal bolts 9 having compressible springs 11 ensleeved over them to attain initial chain tension. Tension is maintained by a pawl and ratchet arrangement 15,17 connected to the bolts 9 by a plate 13. An L-shaped plate 21,22 is attached to the bearing housing 7 via plate 10 and extends through the side of the conveyor return structure. The plate 22 carries a combined chain-stripper/groove cleaner plate at its end adjacent the grooved wheels 5. <IMAGE>

Description

SPECIFICATION Improvements relating to tensioning devices for use with chain conveyors Chain conveyors are extensively used as a means of transporting materials and normally consist of a drive motor, which, by means of suitable gearing, rotates a shaft having two grooved sprocket wheels located at each end ofthe shaft, the sprockets engage with the links ofthe haulage chain and thereby propel them along the flat deck plates ofthe conveyor pans or trays, these two parallel chains are connected together across the width of the conveyor pans by means of flight bars which in turn conveythe actual material.At the opposite end of the length of conveyor pans is situated a return or idler shaft having grooved wheels attached at each end such that when the conveyor is in operation, the chains pass around these grooved wheels as they emerge from the bottom race ofthe conveyor pans and change direction of travel priorto entering the upper race of the conveyor pans.

In orderforsuch a chain conveyorto operate efficiently, it is necessaryforthe chain to be tensioned correctly, this is achieved by allowing the bearings of the retu rn, idler shaft fo be moved forward or backward in line with the conveyor itself, the required tension is attained by means of a threaded bolt which forms a part of the actual conveyor pan or its associated structure and engages with a corresponding threaded nut or member forming a part of the said shaft bearings.

During the operation of such achain conveyor, the tension ofthe chain is affected by several variables such as the intermittent loading of the material being conveyed, changes in the density of the material,the frictional resistence ofthe material, undulations along the length of the conveyor, power surges, etc.

thus if the optimum chain tension isto be maintained, it will be necessary to carry out manual adjustment ofthetensioning device several times throughout the running of the conveyorthereby making it an expensive and time-consuming operation.

When the chains are travelling from the drive shaft tothe return shaft along the bottom raceofthe conveyor pans, a great deal of dirt and grit accumulates between the links ofthe chain,this is carried by the chain onto the grooved wheels on the return shaft where it builds up within the space ofthe groove, if this accumulation of dirt is not cleared away regularly, there is a dangerthatthe links ofthe chain will not fit correctly into the groove thereby rendering the conveyor inoperative and causing delays wh ile the id ler structure is dismantled and the dirt is removed manually.In orderto overcomethis problem, it is normal practice to locate a metal bar on the conveyor pans or associated structure, such that it protrudes into the groove so removing the dirt before it has a chance to accumulate, in addition, immediately behind this cleaner bar is located a curved stripper plate, the curved portion of this plate is directed towards the chain as it passes around the return whells and is in close proximity to the chain, the function of this plate isto ensurethatthe links of the chain are effectively separated from the groove as the chain is about to enter the upper race ofthe conveyor pans.If, during any adjustments to the tensioning device, the tension is increased such that the moveable bearings of the return shaft is moved away from the conveyor pans and associated structure, the cleaner bar and stripper plates remain static so rendering them ineffective and allowing the dirtto accumulate.

There are occassions during the operation of such conveyors that a large object falls onto the conveyor and jamsagainsttheflightbars, bars, in such an event, the upper chains are prevented from moving while the lower chains become very tight, such a situation causes the upper chains on one side of the objectto become very slack such that the conveyor chain and flight bars pile up into a large, disorderly mound.

This causes the links of the chain to become twisted and tangled such that when the blockage is removed, the tension is redistributed resulting in permanent distortion ofthe links so that they no longer mesh with the sprockets of the drive shaft or the weakened links ofthe chain break.

The present invention relates to devices for tensioning chain conveyors and has for its object an improvement therein such that any variations to the optimum tension of the chains while they are in use, will be adjusted automatically thereby maintaining the operational efficiency of the conveyor without incurring the expense and delay of effecting minor alterations manually, likewise, to ensure the accurate siting of the cleaner bar in relation to the space between the wheels attached to the idler or return shaft and also the location ofthe chain stripper plate in its position relative to the chain issuing from the return shaft wheels, a combined unit will be so located that regardless of the varying distances between the return shaft and the end ofthe conveyor pans or associated structure when various adjustments are made to accomodatetension changes, the functions of dirt cleaning and chain stripping will be unimpaired, in orderto overcome the problems associated with sudden jamming of the upperchains and flight bars,the chaintensioning device will incorporate a means of arresting excessive movement of the return shaft thereby preventing undue amounts of loose or slack chain from piling up of the conveyor pan deckthereby causeing stress and damage to the chain links.

According to the present invention, there is provided a chain conveyor tensioning device comprising two units, each being a mirror image of the other and each being located on either side ofthe conveyor and in close proximity to the extensible return or idler shaft, each unit will comprise a steel plate, located and attached to the outer facing sides of the conveyor pans, vertically displaced holes within each plate allowforthe insertion oftwo longitudinal, threaded bolts, the leading ends ofthe bolts are directed towards the return end ofthe conveyor and terminate and are attached to a second plate which forms a part of the conveyor return bearing housing, such bearings being capable of movement towards or away from the ends of the conveyor pans, ensleeved over these bolts are two compressible springs, one end of which abuts against the first plate while the other end abuts against an adjustable nut and check-nut threaded at some point along their lengths, the opposite or following ends ofthe said bolts, protrude and extend beyond the first plate attached to the outer sides of the conveyor pans, such that a generallyTshaped bracket, having holes provided in its horizontal members, such a bracket, when in use, is positioned on its side such that the now vertical members will be in alignmentwith and can be slotted overtheends ofthetwo longitudinal bolts and beheld inthat position by means of opposing threaded nuts, in this position, the central stem of the Tshape will be parallel to the conveyor pans and pointing in a direction away from the return end of the conveyor, the lower edge of this stem has a saw-toothed or serrated edge, which in use will engage with the chisle edge of a pivotly mounted pawl, in order to ensure positive contact between the serrations and the pawl, the other end ofthe pawl is counter-weighted; attached to the plate which forms a part of the return idler bearing, is a further plate having a generally Lshape, one limb of this plate is attached as stated while the other limb extends through an opening in the side of the return structure into the inner side where it is connected to a beam of a U channel section which is telescopically extensible within another U sectional channel beam fixed to the return structure, protruding from the end ofthe extensible member is a combined chain stripper and cleaner unit, the chain stripper portion has its extreme end curved in a concave profile, the radius ofwhich is equal to that of the outer rim ofthe chain return wheel, a simila rly concaved cleaner portion extends beyond the stripper and has a radial equal to that of the recessed inner part ofthe return wheel, excessive movement of the extendable return end of the chain conveyor away from the line of conveyor pans, is prevented by means of elongated holes provided in the sides of the overlapping portions ofthe conveyor pans and the return structure, through these corresponding holes is a boltand nut.

In orderthatthe invention may be fully understood and readily carried into effect, a preferred embodimentthereofwill now be described, by way of example only, with reference to the drawings which accompany this application, in which Figure 1 shows a Sectional Plan View of one half of the chain tensioning device (the chain being removed for reasons of clarity).

Figure2 shows a Sectional Plan View of the chain tensioning device at 'AA' (View on X) with the idler wheel and shaft removed.

Figure 3shows a Sectional View of the chain tensioning device at'BB'.

Figure4shows a Side Elevational View ofthe outside ofthe chain tensioning device.

Figure 5shows a Side Elevational View of the inner-side of the chain tensioning device.

A chain conveyor consisting oftwo parallel chains 1 which are joined together across the width ofthe conveyor by means of flight bars 2, these chains are hauled along thetop guide rail 3 oftheconveyor pans 4, in operation, the endless chains pass around wheels 5 which are located at each end ofthe return or idler shaft 6, this shaft, together with the associated shaft bearing housing 7, is capable of being moved laterally in relationtothe line of conveyor pans.The invention comprises two identical devices, each being a mirrorimageofthe other, is located on either side ofthe conveyor, a plate 8 is attached to the outer sides of the return idler shaft structure, this plate has vertically displaced holes provided through which can be inserted threaded longitudinal bolts 9, the leading edges of these terminate and are attached to a plate 10 which forms a part of the return housing bearing, ensleeved over these bolts are compressible springs 11, adjustments to the compression of these springs in order to attain the correct initial tension to the conveyor chains, is achieved by means of adjustable nuts and lock-nuts 12.The following ends of the longitudinal bolts 9, protrude through holes provided on aTshaped sectional bracket 13, this bracket being secured to the bolts 9 be means of opposing nuts 14, the horizontal stem 15 of the said bracket, has a saw-toother or serrated edge 16 which engages with the chisle edge 17 of a pivotally mounted pawl 18, in order to ensure positive contact between the pawl and the serrated edge, is an adjustable counter-weight 19.Attached to the housing bearing plate loins one limb 21 of an L sectional piate, the other limb ofthis plate 22 extends through an elongated hole provided in the side of the return structure attached to this limb of the plate is a U sectional beam 23 which is telescopically extensible between the upper guide rail 3 and the lower deck 24 of the return structure, extending from the end ofthe U sectional beam, is a concave chain stripper plate 24 whose function is to ensure the correctseperation of the chain from the revolving return wheels, a further extension of the stripper plate is a cleaner plate 26 which extends into the space between the twin return wheels and removes any accumulated dirt. In orderto prevent excessive extension of the return shaft bearings such that the return wheels come into contact with the end plate 27 of the return structure, an elongated slot 28 has a restricting bolt 29 passing through it.

Claims (5)

1. Achain conveyortensioning device located between conveyor pans and an extendable chain return structure comprising two identical units, each unit being a mirror image ofthe other, longitudinal threaded bolts extend between suitable brackets attached to the conveyor pans and the return structure, ensleeved over these bolts and located between the said brackets are compressible springs which are capable of compressionable adjustment by means ofthreaded nuts on the said bolts, aT shaped bracket extends from the bolts and has one end of its horizontal member serrated and in contact with a pivotlly hinged pawl, being counter-weighted to ensure positive contact, a generally Lshaped plate attached by one limb to the chain return structure, has its other limb extending through a suitable slot in the side ofthe said return structure and attached to a telescopically extendable beam having a combined chain stripper and cleaning plate at its leading edge.

2. Achain conveyortensioning device as claimed in Claim 1. in which the extensible movement ofthe return structure from the conveyor pans is restricted by means of corresponding elongated holes and inserted bolt.

3. A chain conveyor tensioning device as claimed in Claim 1. in which the end of the stripper plate has a concaved curved profile equal to the radius of the return wheel.

4. A chain conveyortensioning device as claimed in claim 1. in which the end ofthe cleaner plate has a concaved curved profile equal to the radius of inner portion ofthe return wheels.

5. Achain conveyortensioning device, constructed and arranged substantially as herein described with reference to and as illustrated in any of the accompanying drawings.