AU720814B2 - Belt tracking and tensioning system - Google Patents

Description

P/00/01i1 Regulation 3.2

AUSTRALIA

Patents Act 1990

ORIGINAL

COMPLETE SPECIFICATION STANDARD PATENT Invention Title: BELT TRACKING AND TENSIONING SYSTEM The following statement is a full description of this invention, including the best method of performing it known to us: FHPSYDCEANATPO320\97122010.5 1 CE97101(X)4.4 Belt Tracking and Tensioning System FIELD OF THE INVENTION The present invention relates to belt tracking and belt tensioning systems.

BACKGROUND OF THE INVENTION Belt tracking and belt tensioning systems can each be provided as separate systems to conveyors and weigh feeders. Belt tensioning devices provide the requisite tension so that the drive roller can rotate an endless belt for the conveying of products.

Belt tracking is the term which refers to the process of locating the endless belt, whilst the conveyor is operating, with respect to the rollers in the conveyor or weigh feeder system.

Alternatively a belt tensioner and tracking device can be provided as a single piece of equipment.

One of the difficulties of some prior art belt tracking devices is that they operate by the provision of side rollers which engage the sides of the endless belt. They rely on there being sufficient strength at the edge of the belt so that when it engages the side roller, it will move the ::t1 side roller. Because the side roller is attached by levers to a tracking roller, the tracking roller will rotate so as to re-direct the belt onto its proper tracking path.

Such systems are thus not suitable for use with relatively weak edged belts. Also, because of the engagement of the side roller with the side edges of the belt, damage can occur to the belt.

o It is an object of the present invention to alleviate, at least one of the disadvantages of the prior oooo 1 art, at least in part or in whole.

SUMMARY OF THE INVENTION The invention provides a combination belt tensioning and tracking device, said device including a first and second arm each of which, at a first end thereof, is adapted to be pivotally mounted to a support frame about a common pivot axis, and a tracking/tensioning roller means rotatably secured to said first and second arms at a second end, the tracking/tensioning roller means being adapted to continue to rotate around its longitudinal axis when it also rotates about the longitudinal axis of said first and or said second arm.

.~1y said tracking/tensioning roller is connected at each end to said first and second arms i via ajo in which allows for misalignment.

2 CE97 1(1X)4.4 2 Preferably said joint is selected from one of the following: a spherical bearing, spherical bearing housing; a self aligning bearing, a self aligning housing, a universal type connection.

Preferably said tracking/tension roller has a mass which acts as a belt tension device.

Preferably said tracking/tension roller has a mass which will allow the tracking/tensioning roller to move into or at least partially through the general plane of an endless belt which it will contact and interact with.

Preferably said tracking/tensioning roller when it interacts and contacts said belt generates a friction force which enables said tracking/tensioning roller to translate or track said belt in a corrective direction, when the belt moves from a desired location.

Preferably the position of at least one of said support arms is adjustable at its pivot point with said support frame, in a direction towards or away from a tail roller or in a substantially horizontal direction.

Preferably at least one of said support arms is telescoping or adjustable in length.

The invention also provides a combination belt tensioning and tracking device, said device oooo including a first and second arm connected end to end so as to have a common longitudinal axis 9999 9999 r and so that said first arm is able to rotate relative to said second arm about said longitudinal 9999 axis, said second arm being pivotally mounted to a support frame, and a tracking/tensioning roller means secured to said first arm, the tracking/tensioning roller means being adapted to continue to rotate around its longitudinal axis when it also rotates about the longitudinal axis of oooo said first and or said second arm.

9999 9 Preferably said tracking/tensioning roller means is secured to said first arm via a carriage which -o includes the axis of rotation of said roller means.

o: Preferably said longitudinal axis of said first and said second arm is postionable relative to the S direction of travel of a belt which is to be engaged by said roller means, so that the angle between the direction of travel and the longitudinal axis of said first and second arm is in the range 1 and 890 with the approach side of the belt.

Preferably said angle is in the range of 25' and 650.

Preferably said angle is in the range of 400 and said tracking/tension roller has a mass which acts as a belt tension device.

3CE97101(X)4.4 3 Preferably said tracking/tension roller has a mass which will allow thetracking/tensioning roller to move into or at least partially through the general plane of an endless belt which it will contact and interact with.

Preferably said tracking/tensioning roller when it interacts and contacts said belt generates a friction force which enables said tracking/tensioning roller to translate or track said belt in a corrective direction, when the belt moves from a desired location.

The invention further provides an endless belt or conveyor means including a drive roller and a tail roller mounted on a frame, an endless belt located around said drive roller and said tail roller, said endless belt or conveyor means also including a tracking means which includes at least one support arm being pivoted on an axis substantially parallel to an axis of said endless belt or conveyor means which is transverse to the direction of travel and a tracking roller pivotally held by said support arm, said tracking roller having an axis of rotation, said tracking means being characterised by said axis of rotation of said tracking roller being adapted to rotate freely through a pre-determined angular displacement about at least two orthogonal axes so that if said belt slides transversely relative to said tracking roller, said axis of rotation of said .tracking roller will rotate through an angular displacement in said at least two orthogonal axes °go° 1 to impart to said endless belt a corrective force to realign said endless belt relative to said too tracking roller.

.i Preferably tracking roller is connected to said at least one arm via a joint which allows for misalignment.

Preferably said joint is selected from one of the following: a spherical bearing, self aligning at least one of said at least one support arms is adjustable at its pivot in a direction selected from one of the following: towards said tail roller, or away from said tail roller, a direction having a S: horizontal component, a horizontal direction. oo Preferably at least one of said at least one support arms is telescoping or is adjustable in length.

Preferably said tracking roller also performs a belt tensioning function.

Preferably said tracking/tension roller has a mass which acts as a belt tension device.

Preferably said tracking/tension roller has a mass which will allow the tracking/tensioning roller to move into or at least partially through the general plane of an endless belt which it will and interact with.

-0~Z -o 4 CE97 I 1 ()4.4 4 Preferably said tracking/tensioning roller when it interacts and contacts said belt generates a friction force which enables said tracking/tensioning roller to translate or track said belt in a corrective direction, when the belt moves from a desired location.

The invention also provides a method of tracking an endless belt by means of a roller said method including the steps of 1. positioning said roller in contact with said belt in an equilibrium position; 2. loadingthe roller towards said belt; 3. constraining the rotation or pivoting of said roller so that as the belt moves in a longitudinal direction of the roller, the end of the roller furthest away from the centre of the belt rotates or pivots in a downward direction or a direction towards said belt and simultaneously in a direction which is opposite to the direction of travel of the belt at the point of contact with the roller.

The invention further provides a tracking mechanism for a conveyor or weigh feeder, said mechanism including a tracking roller which is adapted to engage an endless belt of said weigh feeder or conveyor, said tracking mechanism reacting directly to the endless belt moving in a longitudinal direction of said tracking roller, so that the end of said tracking roller which is furthest away from the centre of said endless belt rotates or pivots in a direction towards said S endless belt and simultaneously in a direction opposite tothe direction of travel of said belt at the point of contact of said belt with said tracking roller.

*0 1•2J Preferably said tracking roller is carried in a carriage.

Preferably said carriage is adapted to rotate about a single pivot.

Preferably said single pivot is attached toa second pivot substantially at right angles to a frame of said conveyor or weigh feeder.

S Preferably said second pivot is pivoted at two points, one of which points includes a position Preferably the tracking roller is held by an arm on each end.

Preferably each arm is individually pivoted to a frame holding the endless belt.

Preferably the tracking roller is connected to the arms via a joint which allows for misalignment such as a spherical or self aligning bearing.

a pivot point of one arm includes a position adjustment mechanism.

5CE97101 (X)4.4 Preferably said tracking roller performs a tensioning function.

Preferably said tracking/tension roller has a mass which acts as a belt tension device.

Preferably said tracking/tension roller has a mass which will allow the tracking/tensioning roller to move into or at least partially through the general plane of an endless belt which it will contact and interact with.

Preferably said tracking/tensioning roller when it interacts and contacts said belt generates a friction force which enables said tracking/tensioning roller to translate or track said belt in a corrective direction, when the belt moves from a desired location.

The advantage of a preferred embodiment is that it removes the need for side rollers thus removing a source of belt damage. Another advantage is that, it can be used on both strong and weak edged belts providing there is sufficient elasticity in the belt.

BRIEF DESCRIPTION OF THE DRAWINGS An embodiment of the present invention will now be described, by way of example only, with reference to the accompanying drawings in which: oooa Figure 1 illustrates a plan view of a portion of a weigh feeder or conveyor; °eoo ooo Figure 2 illustrates a side view of the apparatus of the Figure 1; o o Figure 2A to 2C illustrate in detail, items 48, 46 and 62 of Figure 2; Figure 3 illustrates a front elevation of the apparatus of the Figure 2; °o o Figure 4 illustrates a detailed cross-section through the roller/bearing arrangement of Figure 2; Figures 5 to 7 illustrate, in schematic view, the operation of the embodiment of Figures 1 to 4; Figures 8 to 10 illustrate the force diagrams on the apparatus of Figures 5 to 7 respectively; Figure 11 illustrates in schematic view a second embodiment of the invention; Figure 12 schematically illustrates the embodiment of Figures 1 to 4; Figure 13 illustrates a perspective view of one end of a swing arm 24 showing an alternative connection between the tracking roller and the swing arms; and Figure 14 illustrates a perspective view of a part of an alternative swing arm which allows the swing arms to retract and extend when motive power is provided.

6 CE9710 I4.4 6 DETAILED DESCRIPTION OF THE EMBODIMENTS Illustrated in Figures 1, 2 and 3 is the tail end of a weigh feeder or conveyor2. It is constructed of side frames 4 and 5 to which is attached a tail roller 8. The tail roller 8 may include a crown (not illustrated). A crown is formed on the tail roller 8 by forming it so that it has a part spherical surface (a surface formed by a sector of a circle rotated about an axis) which has a diameter at its ends which is smaller than at the centre. The tail roller 8 is attached to the side frames 4 and 5 via an axle and by respective mountings which respectively include a bearing 7 held in a bearing housing 9. The housings 9 are bolted to respective position adjustment mechanisms 6. The position adjustment mechanisms 6 are respectively secured to the side frames 4 and 5. The adjustment mechanisms 6 allow each side of the tail roller 8 to be moved in the direction of arrow 10 (and in the opposite direction) so that a belt 12 can be mounted on the conveyor 2 and around the tail roller 8. The adjustment mechanisms 6 allow the correct geometrical relationship of the tail roller 8 relative to the drive roller (not illustrated) to be established. The belt 12 is supported when it travels around the drive roller (not illustrated) and 15 the tail roller8, by rollers 13 (see Figure 2) which are mounted between side frames 4 and The rollers 13 have been removed in Figures 1 and 3 for clarity of illustration.

To the left of the tail roller 8 is a tracking/tension device 20 which includes a cylindrical roller "222" 22. The mass and diameter of the roller 22 is selected so as to be able to perform both a tracking I• and a tensioning function. In the weigh frame of figure 1, the weight of the roller 22 is approximately 100 kg, to function with a belt width of 1 metre. However, the size of the belt, its *955 elasticity, geometrical constraints and possibly other factors will influence the diameter and o mass of a roller 22 required to achieve either its tracking function or additionally a tensioning S function.

The roller 22 is rotatably connected at each end of an axle connected or passing through the *o SS 2 roller 22, to two swing arms 24, by means of respective bearings 26 which are of the spherical S type or could also be of the self aligning type. Alternatively, the roller 22 or its axle can be connected to the swing arms 24 by means of spherical housings or self aligning housings or other mechanisms such as a universal joint which will allow for misalignment but also allowing continuing rotation of the roller 22 around its axle. The spherical roller bearings 26 allow a maximum of about 3' to 50 of misalignment of the axis of rotation of the roller 22 at each Dective end.

7 CE9701(X)4.4 7 As is illustrated in Figure 4 the roller 22, bearing s26 and swing arms 24 are secured together by means of countersunk set screw 28. In this assembly a shoulder spacer 30 is located near the roller 22 whilst on the other side a bearing retaining washer 32 is used in conjunction with the counter sunk set screw 28 to hold the bearing 26 relative to swing arm 24. For the purpose of illustration only, in Figure 2 those portions of the swing arm 24 which overlap the side frame have been illustrated in sold line, whereas, normally they would be hidden detail and should be represented by broken lines. The longitudinal axis of the swing arms 24 is taken to be the direction from the centre of rotation of the swing arms 24 around pivot shaft 34 to the centre of rotation of the axle of the roller 22 on the swing arm 24.

The swing arm 24 extends upward and away from tail roller 8 until it reaches pivot shaft 34 onto which it is pivotally connected by means of a collar 35 mounted on swing arm 24, through which the pivot shaft 34 is passed. If desired a bearing means can be provided between the collar 35 and the pivot shaft 34. The pivot shaft 34 extends between and is supported by the side frames 4 and 5. The pivot shaft 34 has one end 36 at side frame 5 and another end 38 at side 15 frame 4. The end 38 is rotatably held by the side frame 4 without any allowance for a translational position adjustment.

0* The connection of the swing arms 24 to the pivot shaft 34 does have allowance for horizontal .000 S: translation of the end 36 in the direction of extension of the side frame 4, which results in some ooo• angular rotation of the end 36 around the end 38, to accommodate adjustment. The end 36 is rotatably held in slot 50 of the side frame 5 by means of a horizontal positioning mechanism 0.00 which includes allowance for the pivot shaft 34 being oriented non perpendicularly to the side frame 5. The positioning mechanism 40 is made up of a threaded rod 42 and four nuts 44. The threaded rod 42 and two nuts 44 engage bracket 46 (see Figure 2B) which is welded or secured o. to side frame 5 so as to be immovable. A moveable bracket 48 (see Figure 2A) through which 2 the pivot shaft 34 passes has the threaded rod 42 passing through it and another two nuts 44.

S The moveable bracket 48 re-positions the pivot shaft 34 along slot 50 when the moveable bracket 58 is released by loosening the nuts 44 which engage moveable bracket 48. Once in position, the nuts 44 can be tightened against the moveable bracket 48. The end 36 of the pivot shaft 34 is thus secured or prevented from moving relative to the side frame member The swing arms 24 can rotate about the pivot shaft 34 independently of each other. The swing arms 24 are prevented from approaching each other along the pivot shaft 34, by means of a S ~be52 which is placed over the pivot shaft 34.

b> OPR t- 8 CE9710114.4 8 A lifting mechanism 56 (illustrated in Figure 2) is made up of components mounted on side frame 5 which engage components on the spacer tube 52 to engage swing arms 24. On side frame 5 there is mounted a set screw 58 having a hexagonal head, a lock nut 60 and a threaded bracket member 62 (see Figure 2C). On the spacer tube 52 there are secured two arms 54 which engage the swing arms 24. Also secured to the spacer tube 52 is a lever 64 which extends from the spacer tube 52 in a direction which is angularly displaced lies on a different diametrical direction of the spacer tube 52) from the direction that the arms 54 extend away from the spacer tube 52.

The lever 64 is engaged by the set screw 58. The spacer tube 52 and arms 54 are rotated by means of set screw 58 engaging lever 64. By rotation of set screw 58 the arms 54 engage the swing arm 24 to make them rotate (together with or against gravity) there by lifting or lowering the roller 22 (out of engagement with the belt 12 or lowered to engage the belt 12). The fully retracted position of roller 22 is shown by the circle 66. When the roller 22 is fully retracted, the belt 12 can be replaced. The amount of tension applied to the belt 12 can be varied by varying the weight of the roller. The weight of the roller 22 for tensioning purposes can be calculated by first determining the tension required in the belt to provide effective operation in respect of the design criteria. Once the tension is known and the desired path of the belt is determined, the

C

s:ee s swing arm 24 is theoretically positioned at 450 to the vertical, and by summing the vectors the mass of the roller 22 can be calculated.

Co For the roller 22 to operate in its tracking function, there must be produced a sufficient amount of friction between the roller 22 and the rear surface of the belt. The magnitude of friction will *see 000 be dependent upon several factorswhich include: the coefficient of friction of the roller surface; the coefficient of friction of the rear surface of the belt which engages the roller 22; the angle of seeso wrap or contact of the belt around the roller 22; the diameter of the roller 22; the mass of the OS e roller 22; the distance between the conveyor or weigh-feeders drive and tail rollers; the S: longitudinal elasticity of the belt. No formula is known at this time to take into account of all these factors and a trial and error process may be required to determine for any one factor, what the other factors will need to be in order to achieve the necessary friction force to allow the tracking device described above to function correctly. The operation of the tracking system is somewhat analogous to the tyres of a car on a road and the ability of the steerable wheels to steer the car. If sufficient friction is present between the tyres and the road, then the steerable PMs can change the direction of motion of the wheels and the car. However, if insufficient FIC~ 9 CE97J(X)4.4 9 friction is present between the steerable wheels and the road, no matter how much turning of the steerable wheels occurs, the car and the direction of motion of the steerable wheels will not change. In the tracking situation the roller 22 is similar to the steerable wheels of the car and the belt 12 is analogous to the road way. The same is thus true for the roller 22 and the rear surface of the belt 12 which is engagedby the roller 22. The amount of friction developed between the respective surfaces will affect the level of steer or tracking that will result from the roller 22 to the belt 12.

The ability of the roller 22 to track is dependent upon the ability of the roller 22 to move downward into the belt 12 or.at least move partially through the plane in which the belt 12 lies, during which it will stretch the belt 12 around the roller 22. If the belt has no elasticity, and was taut, the belt would not allow the roller 22 to move towards the belt and the belt would not follow the roller 22. If the roller 22 does not move in the direction of the belt that the roller is contacting, then the longitudinal axis of the roller 12 could not be positioned at an angle to the direction of motion of the belt 12. Thus no corrective tracking force would be generated and the *999 15 tracking device would not function.

9 l: For the roller 22 to perform its tracking function the mass of the roller 22 and the elasticity of 9999 the belt 12 must be matched or be compatible so as to obtain sufficient movement of the roller 22 in the direction of the belt 12 in the drawings it is the downward direction) on a respective side of the belt 12 to produce angling of the longitudinal axis of the roller 22 to the direction of the travel of the belt 12 to provide a corrective tracking force.

9999 9999 0 Thus in order for the tracking mechanism to operate with a belt 12 having low elasticity, it is S" necessary for the roller 22 to have'a high mass so as to ensure that it can move into the belt 9999 9 overcoming the elasticity forces of the belt, in order to produce the corrective tracking force.

9999 S Where as the opposite will be true for a high elasticity belt a lower mass of roller 22 should suffice.

To engage the tracking/tension device 20, the lifting mechanism 56 is fully retracted so that the roller 22 can apply its weight to the belt 12 and the arms 54 will not prevent the movement of the swing arms 24 when the tracking/tension device is operational. When the roller 22 is in its operative position, the swing arms 24 will make an angle of approximately 450 to the vertical.

Some initial belt tension can be adjusted by means of the adjustment mechanism 6 but the main NUt ning is done by the retraction of the arms 54 allowing the swing arms 24 to rotate b

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10CE9710I(X)4.4 towards the belt 12 enabling the roller 22 to make contact with the belt 12. Once the roller 22 has its weight applied to the belt 12, a mark 68 which is drilled or impressed into the side of the swing arm 24 is located approximately in the centre of the diamond shaped aperture 70 which is present through the side frame 5. When in its operational position the roller 22 has its lowest point below the lowest point of the tail roller 8. A contact angle of approximately 150 between the belt 12 and the roller 12 is achieved however other contact angles may be appropriate depending upon the elasticity of the belt and the other parameters of the system. The amount of weight provided in the roller 22 will also be dependent upon the desired belt tension and other factors as is known in this art. The mark 68 will be located approximately in the aperture because of the calculated deflection of the belt 12 for the weight of the roller 22 when suspended on the beltl2.

Once the belt tension has been adjusted, the conveyor 2 is activated and the end 36 of pivot shaft 34 is moved in the slot 50 until such time as the belt 12 is sitting on the tail roller 8 in the desired position. Once the belt 12 has attained the correct position, the end 36 of the pivot shaft 34 is moved to a position (by releasing nuts 44 near moveable bracket 48 and adjusting the 9 *o position of moveable brackets) so that the roller 22 is no longer exerting any lateral or corrective force on the belt 12, so that no further movement of the belt 12 occurs and it remains in that position. At this point, the positioning mechanism 40 is secured and the tracking S mechanism/tensioning device 20 is operational.

Once set up, the tracking mechanism/tensioning device 20 operates automatically in response to S movement of the belt 12 in a longitudinal direction of the roller 22.

The automatic operation of the tracking/tension device 20 is readily understood by reference to *o Figures 5 to In Figure 5 the roller 22 is shown in a position where the belt 12 is off to one side and needs corrective action. The swing arm 24 which is the one adjacent to the side frame 5, makes an angle D 1 to the vertical. Whereas the swing arm 24 closest to the side frame 4 makes an angle D 2 and D 2 is much less than D 1 In operation, the roller 22 of Figures 1 to 3 Can make angle to the swing arm 24 of between 00 at equilibrium to approximately 5' This range is dictated by the maximum angle possible at the spherical bearing 26. The belt 12 travels in the direction of arrow 72. The movement of the belt 12 in the direction of arrow 74 will mean that a portion of t ill overhang the side 76 of the belt 12. Because of the weight of the roller 22 and lasticitf the belt 12, the roller 22 rotates to adopt an angle to the direction of travel as is 11CE9714)1()4.4 11illustrated in the plan view in Figure 8. Because the swing arms 24 are of the same length there is also an angle into the page of Figure 8. To explain it another way the end of the roller 22 overhanging side 76 has rotated downwardly about the longitudinal axis of the belt 12 and in a direction opposite to arrow 72 about an axis normal to the surface of the belt 12. When the roller 22 rotates into the belt 12, about the longitudinal axis of the belt 12, it will exert greater pressure on one side and less on the other side of the belt 12. Because of the orientation of the roller 22 in a downward and rearward direction, (or direction opposite to the direction of travel of arrow 72) the belt 12 is forced in the direction of arrow 78 (see figs The larger the angle of the roller 22 is to the direction of travel of arrow 72, the larger will be the force in a direction of arrow 78.

Thus, after the belt 12 continues to travel the belt 12 and roller 22 adopt the angular positions as illustrated in Figure 6 and Figure 9. As 02 is getting closer to D 1 (as, in Figures 6 and 9) the size of the force in the direction of arrow 78 in Figure 9 is decreased, however, there is still a force present thus continuing to move the belt in the direction of arrow 78 at a slower rate. This will continue until such time as the belt 12 has adopted its equilibrium position, in this instance where the roller 22 is centred on the belt 12 as is illustrated in Figures 7 and 10 where (D D.

A similar operation functioning will occur, if the other end of roller 22 were over hanging the end of belt 12 nearest to the reader in figs 5 to 7.

o* A similar effect would occur if the roller 22 was of a length which was not equal to or wider o...2t than the width of the belt 12. Thus when the length of theroller 22 is less than the width of the belt 12, until such time as the centre of the roller 22 was coincident with the centre line of the a. belt 12, automatic adjustments would continue to occur. In this situation the elastic nature of the belt 12 will help to produce the corrective effect by forcing the roller 22 to rotate both about the ooo• longitudinal axis of the belt 12 and about an axis normal to the surface of the belt 12.

The mechanism by which the roller 22 will correct the tracking when it is shorter than the width of the belt 12 is not completely understood, but it is believed that when the roller 22 is smaller than the width of the belt 12, if it is not centred on the belt 12 the amount of elasticity in the smaller band not covered by roller 22 relative to the amount of elasticity in the larger band not covered by roller 22 (due to the off-centring of the roller 22 on the belt 12) will have a similar effect as that illustrated in Figures 5 to 12CE97 II(X)4.4 12- The conveyor 2 may include, because of wear or other factors, an inherent set of circumstances which would create forces that tend to take the belt 12 off track. In this circumstance, in the system equilibrium position (that is when the belt 12 is in the desired position on the tail roller 8) the roller 22 may need to be positioned at an angle to the direction of travel of the belt 12 by means of the adjustment mechanism 40. That is the roller 12 may be imparting a corrective force at all times so as to take into account the inherent forces which would tend to take the belt 12 off track.

Illustrated in Figure 11 is an embodiment of a different construction by comparison to that of Figures 1 to 10. In this embodiment, the two separate swing arms 24 are replaced by single link comprising swing arms 80 and 84. A joint 82 connects the swing arms 80 and swing arm 84 end to end and having a common longitudinal axis. The joint 82 allows rotation around the longitudinal axis of the swing arms 80 and 84. The arrow 94 represents the direction of rotation of swing arm 84 relative to swing arm 80 by means of the joint 82.

The roller 22 in the embodiment of Figure 11 is mounted on a carriage 86. The swing arm 84 is •5 rigidly connected at 88 to the centre portion of the carriage 86 which is the centre of the roller ooo• 22. The swing arm 80 is rigidly connected at 90 to the pivot shaft 34 which thus allows the swing arms 80 and 84, carriage 86 and roller 22 to rotate in the direction of arrow 92 to allow oo•• S the weight of the roller 22 to act upon the belt 12. The arrows 96 and 98 schematically represent the adjustment of the pivot shaft 34 by means of a positioning mechanism similar to positioning mechanism 40 illustrated in Figures 1 and 2.

ooo Illustrated in Figure 12 is a schematic representation of the embodiments of Figures 1 to Illustrate in Figure 13 is an alternative connection mechanism or joint 23 instead of using a self aligning bearing housing or spherical bearing or housing, for connecting the tracking roller 22 S: to the swing arm 24 so as to allow for misalignment therebetween, and thus proper operation of the tracking device. In this joint 23 the swing arm 24 has a yoke 25 formed on its end so as to carry pins 29 which will provide an axis of rotation for a pivotally attached ring portion 27. The ring portion 27 has the pins 29. A diameter through the ring portion 27 in which the pins 29 lay, is perpendicular to the longitudinal axis of the swing arm 24. The ring portion 27 has another diameter which is at right angles to the previously described diameter in which lay another two pins 29a, which provide an axis of rotation for the axle holder 31. The axle holder 3 in turn secures the axle 33a of the tracking roller 22. The joint 23 gives the roller 22 the S a egrees of freedom as a spherical bearing 26 and the other mechanisms mentioned 13CE9701004.4 13previously, to allow the tracking roller 22 to function as described above, in relation to the embodiments of figs 1 to 11.

While initial adjustment etc, is performed by means of the positioning mechanism 40, the same function could be performed by one or both swing arms 24 being constructed so as to be extendable or telescoping. This can be done such as illustrated in Figure 14, by the swing arm 24 having an upper portion 24a which is able to slide relative to lower portion 24b by their enclosure in each other through aperture portions 24c and 24d. The space 24e on the aperture portions 24c and 24d could be enclosed if desired. The aperture portions 24c and 24d have respectively apertures 24f and 24g formed through them. If desired an bearing means or surface might also be included in the apertures 24f and 24g to reduce friction when the upper portion 24a moves relative to the lower portion 24b. The upper portion 24 a and lower portion 24d can be made to move relative to each other by means of a hydraulic, pneumatic cylinder being connected between pins 24h and 24j. The pins 24h and 24j can be positioned at any appropriate location on the upper portions 24a or lower portion 24b. If desired the cylinder actuation could be replaced by a motorised machine screw arrangement, interconnecting the upper and lower portions 24a and 24b. Another alternative for providing the swing arms 24 with a telescoping or extending ability is to manufacture one or both swing arms from a dual action hydraulic cylinder, which can extend and or contract by application of fluid pressure.

The above has been described as a combination tracking and tensioning mechanism. However, "2 if a tensioning mechanism is already provided, the above embodiment can act solely as a :o tracking device.

S S* In the above description there is little to no ability of the swing arms 24 to move relative to move relative to the pivot shaft 34 in the direction of the longitudinal axis of the pivot shaft 24.

This is because any such movement would delay the operation of the tracking/tension device 5 20, which will not function, to correct the position of the belt 12, until no further movement of the swing arms in that direction will occur. Thus any provision for the arms 24 to translate along the pivot shaft 34 in the direction of the longitudinal axis of the pivot shaft 34, will mean that there will be a lead time before correction will occur of the belts position However, this lead time could be easily taken into account in the construction of tracking devices in accordance with the invention.

e tracking device will be most effective when the swing arms 24 have their longit inal direction at an angle of some 450 (and to within 100 either side thereof) to the 14CE97 10( lW4.4 14direction of the side of the belt which is moving toward the roller 22. This is because the maximum possible horizontal and vertical movement of the roller 22 will occur at this angle.

However, the tracking device will also operate, less effectively at an angle in the range of to 650. It may even be possible to have the tracking device operate at an angle in the range of 1° to 890, but as to how effective it will be is uncertain.

The foregoing describes two embodiments of the present invention and obvious modifications by those skilled in the art can be made thereto, without departing from the scope of the present invention.

For example instead of the adjustment mechanism 40 being utilised to initially adjust the position of the roller 22 the swing arms 24 can be replaced by one having a telescoping capability which will achieve a similar effect. The use of positioning mechanism 40 which allows for adjustment or other adjustment means, such as an automatically contracted telescoping swing arm 24, is highly preferred because an operator will not need to place their hands on tools within the confined space or volume swept by the belt 12. Mounting the positioning mechanism 40, or controls on the side frame 5, is thus a safer mounting position.

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Claims (20)

1. A belt tracking mechanism,-said mechanism including a tracking roller which is adapted to engage an endless belt such as for a weigh feeder or conveyor, said tracking mechanism reacting directly to the endless belt moving in a longitudinal direction of said tracking roller, so that the end of said tracking roller which is furthest away from the centre of said endless belt rotates or pivots in a direction towards said endless belt and simultaneously in a direction opposite to the direction of travel of said belt at the point of contact of said belt with said tracking roller.

2. A belt tracking mechanism as claimed in claim 1 wherein said tracking roller is carried in a carriage.

3. A belt tracking mechanism as claimed in claim 2 wherein said carriage is adapted to rotate about at least one pivot.

4. A belt tracking mechanism as claimed in claim 3 wherein said at least one pivot is attached to a second pivot substantially at right angles to a frame carrying said endless belt. 1 5. A belt tracking mechanism as claimed in claim 4 wherein said second pivot is rotatably held at two points, one of which includes a position adjusting mechanism. •too

6. A belt tracking mechanism as claimed in claim 1 wherein the tracking roller is rotatably held by a first and a second arm on each end of said tracking roller. oooo

7. A belt tracking mechanism as claimed in claim 6 wherein said first and second arms are individually pivoted to a frame holding the endless belt. o*

8. A belt tracking mechanism as claimed in claim 6 or 7 wherein the tracking roller is connected to the first and second arms via a joint which allows for a misalignment.

9. A belt tracking mechanism as claimed in any one of claims 6 to 8 wherein a pivot point of one of said first or second arms includes a position adjustment mechanism.

10. A belt tracking mechanism as claimed in any one of claims 6 to 9 wherein said tracking roller is adapted to continue to rotate around its longitudinal axis when it also rotates about a longitudinal axis of said first and or said second arm.

11. A belt tracking mechanism as claimed in claim 8 wherein said joint is selected from one ollowing: a spherical bearing, spherical bearing housing; a self aligning bearing, a self Saligni 4 ousing, a universal type connection. o 16CE97101(04.4

16- 12. A belt tracking mechanism as claim in claim 9 wherein the position of at least one of said support arms is adjustable at its pivot point with said support frame, in a direction towards or away from said tracking roller or in a substantially horizontal direction. 13. A belt tracking mechanism as claimed in any one of claims 6 to 12 wherein at least one of said first or second arms is extendable or adjustable in length. 14. A belt tracking mechanism as claimed in claiml wherein said mechanism includes a first and second arm connected end to end so as to have a common longitudinal axis and so that said first arm is able to rotate relative to said second arm about said longitudinal axis, said second arm-being pivotally mounted to a support frame, said tracking roller being secured to said first arm, the tracking roller being adapted to continue to rotate around its longitudinal axis when it also rotates about the longitudinal axis of said first and or said second arm. A belt tracking mechanism as claimed in claim 14 wherein said tracking roller means is secured to said firm arm via a carriage which includes the axis of rotation of said roller. o o 16. A belt tracking mechanism as claimed in claim 14 or 15 wherein said longitudinal axis o of said first and said second arm is positionable relative to the direction of travel of said belt which is to be engaged by said roller so that the angle between the direction of travel and the S longitudinal axis of said first and second arm is in the range 10 and 89' with the side of the belt S which is moving toward the roller.

17. A belt tracking mechanism as claimed in claim 16 wherein said angle is in the range of 20 250 and 65 0 S* 18. A belt tracking mechanism as claimed in any one of claims 16 or 17 wherein said angle is in the range of 40' and 500 S: 19. A belt tracking mechanism as claimed in any one of claims 14 to 18 wherein said tracking roller has a mass which acts as a belt tension device.

20. A belt tracking mechanism as claimed in any one of claims 14 to 19 wherein said tracking roller has a mass which will allow the tracking roller to move into or at least partially through the general plane of an endless belt which it will contact and interact with.

21. A belt tracking mechanism as claimed in any one of claims 14 to 20 wherein said roller when it interacts and contacts said belt generates a friction force which enables said roller to 1 7 CE97101004.4 17- translate or track said belt in a correction direction, when the belt moves from a desired location.

22. A belt tracking mechanism as claimed in any one of claims 1 to 21 wherein said tracking roller performs a tensioning function.

23. A belt tracking mechanism as claimed in any one of claims 1 to 22 wherein said tracking roller has a mass which acts as a belt tension device.

24. A belt tracking mechanism as claimed in any one of claims 1 to 23 wherein said tracking roller has a mass which will allow the roller to move into or at least partially through the general plane of an endless belt with which it will contact and interact.

25. A belt tracking mechanism as claimed in any one of claims 1 to 24 wherein said tracking roller when it interacts and contacts said belt generates a friction force which enables said tracking roller to translate or track said belt in a corrective direction, when the belt moves from a desired location.

26. A conveyor belt or weigh feeder having a belt tracking mechanism as claimed in any one ::3l of claims 1 to

27. A belt tracking mechanism being substantially as herein described with reference to the accompanying drawing. Dated this 23rd day of March 2000 Control Systems Technology Pty Ltd ACN 002 611 332 by its Patent Attorneys Freehills Patent Attorneys Freehills Patent Attorneys