WO2013082642A1

WO2013082642A1 - Tracking apparatus for trough conveyors

Info

Publication number: WO2013082642A1
Application number: PCT/AU2011/001581
Authority: WO
Inventors: Timothy O'CARROL
Original assignee: Tru-Trac Rollers (Pty) Ltd; Savage, Paul
Priority date: 2011-12-07
Filing date: 2011-12-07
Publication date: 2013-06-13

Abstract

Conveyor tracking apparatus comprising a support frame adapted to be mounted to a conveyor support structure below a conveyor belt to be tracked by the apparatus. The belt intended to travel along the conveyor support structure and be substantially aligned with a longitudinal central travel axis. The tracking apparatus includes a sub-frame pivotally mounted to the support frame and able to pivot about a pivot axis which is perpendicular to the plane of the centre of the belt. The pivot axis is located on the central travel axis. A pair of wing rollers are mounted for rotation on the sub-frame on opposite sides of the pivot axis, the axes of rotation of the wing rollers both being in a plane which includes the pivot axis. At least the outer region of each wing roller is tapered convergently in a direction away from the pivot axis. Two central rollers are mounted for rotation on the sub- frame and aligned generally perpendicular to the central travel axis and perpendicular to the pivot axis, the central rollers having parallel axes of rotation located on opposite sides of the pivot axis. The sub-frame is supported from the support frame on a pivot support located on the pivot axis and at an elevated location adjacent the underside of the belt.

Description

TRACKING APPARATUS FOR TROUGH CONVEYORS

BACKGROUND OF THE INVENTION

This invention relates to apparatus for tracking conveyor belts, in particular although not exclusively, trough shaped conveyor belts.

Conveyor belts, particularly those that run over long distances, in harsh operating conditions, or in particularly dirty operating environments, tend to drift laterally out of their intended path of travel. This can result in the edge of the belt coming into contact with the conveyor support structure on which the belt is supported, resulting in damage to either the structure or the belt edge. With trough conveyors as the belt moves towards one side of the frame that side of the belt moves upwards whilst the opposite side moves downwards, resulting in spillage of the load earned by the belt. Conveyor belts are typically supported on idlers which are aligned perpendicularly to the direction of travel of the belt. Misalignment of the idlers can cause the belt to drift laterally. Also, build-up of deposits on the idlers can cause belt drift. Temperature changes during operations also tend to cause belt drift as sections of the belt may tend to stretch as the temperature increases. Also, as a belt ages, or is repaired, differential stretch can cause belt drift.

The problem of belt drift is particularly prevalent with reversible belts since it is possible to adjust the set-up of the frame and belt so that the belt will track in a satisfactory manner in one direction of belt travel, but will then not track centrally in the opposite direction of travel.

To alleviate the aforementioned problems it is known to install tracking rollers at selected locations along the path of the belt. Tracking rollers are typically mounted on some form of pivot arrangement, and when a belt travels out of alignment the tracking roller will be caused to pivot on its axis so as to steer the belt back to its central path. Tracking apparatuses for both flat belts and trough belts are known, some of which are more effective in operation than others.

Tracking of trough shaped belts is particularly problematic since the tracking roller on each side of the belt tends to press into the inclined part of the belt as the tracking device attempts to correct the alignment of the belt. In other words, pivoting of the apparatus is resisted by the rollers on each side of the belt tending to press into the underside of the belt, causing the tracking action to be less effective than otherwise would be the case.

Tracking of trough shaped belts is also made difficult due to the fact that the entire tracking apparatus needs to be robust. Since the tracking apparatus will typically have a pair of wing rollers and one or more central roller, all of which are supported on a frame which needs to pivot, the entire apparatus will be heavy, and pivoting of the apparatus tends to be sluggish at best.

SUMMARY OF THE INVENTION

According to the invention there is provided conveyor tracking apparatus comprising: a support frame adapted to be mounted to a conveyor support structure below a conveyor belt to be tracked by the apparatus, the belt intended to travel along the conveyor support structure and be substantially aligned with a longitudinal central travel axis ;

a sub-frame pivotally mounted to the support frame and able to pivot about a pivot axis which is perpendicular to the plane of the centre of the belt, the pivot axis being located on said central travel axis;

a pair of wing rollers mounted for rotation on the sub-frame on opposite sides of the pivot axis, the axes of rotation of the wing rollers both being in a plane which includes the pivot axis, at least the outer region of each wing roller being tapered convergently in a direction away from the pivot axis; and

a pair of central rollers mounted for rotation on the sub-frame and aligned generally perpendicular to the central travel axis and perpendicular to the pivot axis, the central rollers having parallel axes of rotation located on opposite sides of the pivot axis;

wherein

the sub-frame is supported from the support frame on a pivot support located on the pivot axis and at an elevated location adjacent the underside of the belt.

The wing rollers may be inclined relative to the central rollers. Further there is provided for the axes of rotation of the wing rollers to be inclined at an angle of between 30° and 60° to the axes of the central rollers. Preferable the rollers include adjustment means for varying the angle of inclination of the wing rollers. The wing rollers preferably taper along their entire length with the widest diameter on the proximate ends thereof and the narrowest diameter at the distal ends thereof. The angle of taper is preferably constant, and may be between 2° and 10° half cone angle.

The width of the support frame may be variable to fit with a range of conveyor support structures. The support frame may include mounting means having a plurality of mounting positions to enable the height of the rollers relative to the conveyor support structure to be varied.

The support frame may include an upstanding post about which the sub- frame is able to pivot. The support post may include the pivot support in the form of a pivot ball on the upper end of the post on which the sub-frame rests and is able to pivot. The sub-frame may include a sleeve or socket having an axis coincident with the pivot axis, the sleeve fitting in a telescopic and rotatable manner over the support post, and having a blind end against which the pivot ball bears in use. The blind end may include a recess or cup within which the pivot ball is received. These and further features of the invention will be made apparent from the description of an embodiment of the invention, given below by way of example. In the description reference is made to the accompanying drawings, but the specific features shown in the drawings should not be construed as limiting the scope of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 shows a perspective view of a tracking assembly for trough conveyor belts according to the invention;

Figure 2 shows an exploded perspective view of the tracking assembly shown in Figure 1 ;

Figure 3 shows a side view of the assembly shown in Figure 1 ;

Figure 4 shows a plan view of the assembly shown in Figure 1 ; Figure 5 shows a side view of the assembly shown in Figure 1, highlighting the manner in which the angle of inclination of the wing rollers can be adjusted;

Figure 6 shows a plan view of the assembly slewed through an arc for steering a belt back to its central path of travel;

Figure 7 shows a similar view to that of Figure 6, but with the assembly slewed in the opposite direction; Figure 8 shows a plan view of the support frame, depicting the manner in which its width can be adjusted to accommodate different conveyor support frames;

Figure 9 shows a side view of the support frame; Figure 10 shows in a part cut away drawing the manner in which the sub-frame and the support frame fit together; and Figure 11 shows a side view of the sub-frame and support frame fitted together.

DESCRIPTION OF A PREFERRED EMBODIMENT

Referring initially to Figures 1 and 2, a tracking assembly 10 for trough shaped conveyor belt 12 is depicted. The assembly is comprised essentially of a support frame 1 , and a sub-frame 16 which is pivotally supported on the support frame.

A pair of central rollers 18 will support the central region of the conveyor belt 12 and a pair of wing rollers 20a and 20b support or are contacted by the edge regions of the belt on opposite sides of the belt. The relationship between the wing rollers and the belt is discussed in more detail below.

The support frame 14 includes a pair or extendible rails 22 which a joined together by cross braces 24. The central cross brace has an upstanding post 26 mounted thereto onto which the sub-frame 16 is mounted to enable the sub-frame 16 to pivot relative to the support frame 14. At each end of the rails 22 is located a mounting bracket 28 which is connected to the rails 22 by tubular rods 30 which slide telescopically into the ends of the rails 22, and are secured therein by lock bolts 32. By varying the extent to which the rods slide into the rails 22 the width of the support frame can be varied to accommodate different conveyor structures (not shown).

Each mounting bracket 28 includes an angle bracket 34 with a series of mounting positions 36 to enable the height of the assembly relative to the conveyor structure to be varied. This enables the contact pressure between the tracking assembly and the conveyor belt to be varied which is important for the purpose of adjusting tracking responsiveness and efficacy of the device. The angled brackets also include slotted mounting holes 37 for mounting to the conveyor structure.

The sub-frame 16 includes a pair of support plates 38, each of which has a lateral support arm 40 mounted thereto for supporting the wing rollers 20. The support plates 38 are connected together by a tubular beam 42 which holds the support plates in position relative to each other, and provides rigidity to the structure. The tubular support beam 42 carries a downwardly extending tubular socket 44 which in use fits over the post 26 to enable the sub-frame 16 to pivot relative to the support frame 14. This is discussed in more detail below. The support plates 38 each have a pair of notches 46 therein for receiving the central rollers 18. As shown, when mounted to the support plates 38 the rollers 18 are parallel to each other and parallel to the tubular beam 42. The rollers are on opposite sides of the tubular beam and the socket 44. The central rollers are load supporting, and may be steel drum rollers, or, for more grip, may be lagged with vulcanized rubber or the like.

The lateral support arms 40 are coplanar with the tubular beam 42 and the socket 44. Each support arm 40 supports one of the wing rollers 20. The proximate ends of the wing rollers 20 are supported on brackets 46 and the distal ends of the wing rollers 20 are supported on an adjustable support bolt 48. As shown, the support bolts 48 are relatively long and are fixed relative to the support arms by a pair of nuts 50 which are used to position the support bolts 48 relative to the support arms. Clearly, by varying the effective length of the support bolts 48 the angle of the wing rollers can be varied. This wilt be used to accommodate different belt trough configurations.

Figure 4 depicts the assembly in plan view with the longitudinal central travel axis shown at numeral 60. The edges of the belt are shown at 62 when the belt is travelling centrally, and the sub-frame 16 will be perpendicular to the travel axis 60. The travel axis 60 is shown with an arrow on each end thereof, indicating that the belt may travel in either direction, that is, the tracking apparatus will operate for belts which travel in either direction and reversible belts.

Figure 5 depicts two different positions of the wing rollers 20. As shown wing roller 20a is inclined at an angle of approximateJy 47°. Roller 20b is inclined at an angle β of inclination of approximately 40°. Clearly for any set-up, rollers 20a and 20b will be at the same inclination, but the Figure 5 drawing depicts how the wing rollers can be inclined relative to the support arrangement.

It will also be appreciated that the invention will operate through a wide range of wing roller inclinations. Indeed, it will be possible for the wing rollers to be horizontal, as would be the case for flat belts. Typically, for trough conveyors, the wing rollers will be inclined at between 30° and 60° and usually around 40°.

The post 26 and socket 44 together form a pivot assembly about which the sub-frame 16 is able to pivot relative to the support frame 14. The pivot axis 52 of this pivot arrangement is perpendicular to the belt, that is, for a horizontally travelling belt the pivot axis 52 will be vertical. The axes of rotation of the wing rollers 20 and the pivot axis will all be coplanar.

Figure 3 depicts a side view of the manner in which the assembly supports the belt 16. As shown, the belt is in contact with the central rollers 18 and the wing rollers 20. However, different conveyors and set-up arrangements might dictate a different contact arrangement between belt and wing rollers. For example, for certain set-ups it may be preferable for the wing rollers to be more steeply inclined than the side regions of the belt with only the outer edge region of the belt being in contact with the wing rollers when the belt is in its central position. When the belt drifts to one side of its intended central path, more of the belt on that side will come into more direct contact with the wing roller, causing the wing roller on that side to be dragged forward, resulting in the sub-frame 16 slewing to thereby steer the belt back to its central position. It is found, however, that for most applications tracking is best achieved when the wing rollers are at approximately the same angle of inclination as the sides of the trough belt, and are thus aligned with the idlers immediately adjacent the tracking assembly. In the preferred arrangement, the belt 12 will thus be in direct contact with both wing rollers, much as is depicted in Figure 3 of the drawings.

The two wing rollers are tapered over their entire length, although it is only the outer portion of the rollers that must be tapered. It will be appreciated that the belt travelling over the wing rollers will cause the wing rollers to rotate. However, since the outer portion of the wing rollers are travelling at a slower peripheral speed than the inner portion of the wing rollers, due to the reduced diameter of the outer portion, the outer portion of the wing rollers will tend to be dragged forward by the belt causing the sub-frame 16 to slew and steer the belt back to its central position. Figure 4 shows sub- frame 16 in its central position, Figure 5 shows the sub-frame 16 slewed to a position in which the wing roller 20a has been dragged forward, and Figure 6 shows the sub-frame 16 slewed to a position in which the wing roller 20b has been dragged forward. Clearly when the sub-frame 16 is in a position such as those shown in Figures 5 or 6 the central rollers 18 will act to steer the belt back towards the centre of the frame. As the belt reaches the centre the forces on the rollers 20a and 20b will equalize, causing the sub-frame 16 to once again adopt the perpendicular position shown in Figure 4. The sub-frame 16 will remain in that position until such time as the belt once again moves off centre.

One advantage of the arrangement shown is that the aforementioned pivoting or slewing action will take place irrespective of the direction of travel of the belt. That is, because the wing rollers are coplanar with the pivot axis 52 the wing rollers will not be on the leading or the trailing side of the belt and the apparatus will thus work well with reversible belts. It has been mentioned that the pivot axis 52 for horizontal belts will be vertical. It has been found that the aforementioned slewing action works best when the point about which the sub-frame 16 pivots is as high as possible. Obviously there is a limit to the height of the pivot point, since it cannot be higher than the belt. However, the height of the post 26 is selected so that the sub frame is supported at a height which is approximately coplanar with the axes of rotation of the centre rollers 18. It will be noted that the post 26 has a ball 54 on the upper end thereof and the socket 44 is closed off by an end plate 56 which has a hemi-spherical recess 58 formed therein in which the ball 54 locates. The ball 54 and recess 58 define a pivot support for the assemble, which allows the sub- frame 16 to pivot relative to the support frame 14, but also supports the sub-frame 16 from the support frame. Clearly other forms of support bearing arrangements are possible, including thrust bearings and the like, but as mentioned above it is found to be desirable that the support arrangement is as high as possible, that is, just adjacent the belt if possible. Figure 11 shows the ball and socket arrangement in more detail.

It will be noted that the post and socket pivot arrangement not only supports the sub-frame 16 from the support frame 14, but since the post 26 is a sliding telescopic fit in the socket 44 the arrangement will hold the sub- frame 16 in its correct alignment, even when the loads on the sub-frame 16 are off-centre. The sub-frame 16 must be able to rotate about axis 52, but must not tilt relative to axis 52. The pivot arrangement thus defined will thus need to be a quality interaction, machined to a fine degree of tolerance and filled with suitable lubricant. Seals (not shown) will prevent the ingress of contaminants into the pivot arrangement. It will be noted that since the socket is inverted, that is, opened at its lower end, the ingress of contaminants into the pivot will in any event be kept to a minimum. An annular bearing arrangement could be included into the pivot arrangement for particularly high load installations.

In one arrangement the interface between the ball 56 and the recess 58 is approximately, at the elevation of the rotational axes of the central rollers. The support could be higher or lower than this elevation. It is considered important that the support point is well above the point at which the axes of rotation of the wing rollers intersect. Figures 8 and 9 depict the manner in which the support frame 14 can be adjusted to accommodate different conveyor structures. It will be appreciated that for wider belts substantially the same support frame 14 an sub-frame 16 can be used, although the plates 38 might be spaced further apart from each other, and longer central rollers 18 will then be used to support the central region of the belt. The support bolts 48 will be adjusted to accommodate different belt configurations and also to ensure that optimum tracking effect is achieved for a particular weight and tension of conveyor belt. It is preferred that the central rollers 18 each have an outer diameter of at least 100mm, and preferably approximately 150mm, to ensure that these rollers do not rotate too fast which could cause damage to the bearings which rotationally support these rollers 18. The height of the post 26 on which the sub-frame 16 is supported will be selected to lie just below the peripheral upper edge of the central rollers so as to ensure the post 26 does not interfere with or cause damage to the belt travelling on the assembly.

Many variations may be made to the embodiment without departing from the invention. In particular, the wing rollers may differ from those described herein, in that only the outer region of the wing rollers need be tapered. The entire pivot and support arrangement for the sub-frame may differ from that described herein, although having the pivot support at an elevated location adjacent the underside of the belt is considered to be an important feature of the invention.

Claims

1 According to the invention there is provided conveyor tracking apparatus comprising: a support frame adapted to be mounted to a conveyor support structure below conveyor belt to be tracked by the apparatus, the belt intended to travel along the conveyor support structure and be substantially aligned with a longitudinal central travel axis, the belt having a generally horizontal central region;

a pair of central rollers mounted for rotation on the sub-frame and aligned generally perpendicular to the central travel axis and perpendicular to the pivot axis, the central rollers having parallel axes of rotation located on opposite sides of the pivot axis; wherein

2 Conveyor tracking apparatus according to claim 1 wherein the wing rollers are inclined relative to the central rollers.

3 Conveyor tracking apparatus according to claim 2 wherein the axes of rotation of the wing rollers are inclined at an angle of between 30° and 60° to the axes of the central rollers.

4 Conveyor tracking apparatus according to claim 2 or 3 wherein the sub-frame includes adjustment means for varying the angle of inclination of the wing rollers.

5 Conveyor tracking apparatus according to any preceding claim wherein the wing rollers taper along their entire length with the widest diameter on the proximate ends thereof and the narrowest diameter at the distal ends thereof.

6 Conveyor tracking apparatus according to any preceding claim wherein the angle of taper is constant, and between 2° and 10° half cone angle. 7 Conveyor tracking apparatus according to any preceding claim wherein the width of the support frame is variable to fit with a range of conveyor support structures.

8 Conveyor tracking apparatus according to any preceding claim wherein the support frame includes an upstanding post about which the sub-frame is able to pivot.

9 Conveyor tracking apparatus according to claim 8 wherein the support post includes a pivot support in the form of a pivot ball on the upper end of the post on which the sub- frame rests and is able to pivot.

10 Conveyor tracking apparatus according to claim 9 wherein the sub-frame includes a sleeve or socket having an axis coincident with the pivot axis, the sleeve fitting in a telescopic and rotatable manner over the support post, and has a blind end against which the pivot ball bears in use.