Patent Description:
The invention relates to tracking apparatuses for tracking conveyor belts.

Rollers for conveyor belts are arranged so that the conveyor belt travels thereover in a downstream belt travel direction and path. However, conveyor belts can tend to meander or mistrack laterally toward one side or the other of the rollers due to reasons such as uneven loads carried by the belt. Conveyor belt tracking devices have been developed that respond to belt mistracking to attempt to redirect the belt back to its correct travel path substantially centered on the conveyor rollers.

One type of belt tracking device configured to correct a misaligned belt has sensor rollers that are mounted to arms that are each operatively connected to a frame for tracking or training rollers under a belt. If the belt becomes misaligned, it will forcefully engage the sensor roller at the misaligned side, which will cause the arms to force the belt training roller to pivot for steering the belt back toward its proper downstream travel path. However, the sensor rollers are generally located upstream or downstream of the training rollers to create the necessary moment arm for pivoting the rollers. This upstream or downstream mounting of the sensor rollers means that the correcting mechanism is limited to use when the belt travels in a single direction. Furthermore, this solution requires the edge of the belt to forcefully make contact with the sensor rollers, which can undesirably damage the belt.

One type of belt tracker that avoids the use of sensor rollers is disclosed in <CIT>. The Cumberlege system includes a pair of rollers mounted to an elongate support shaft that is pivotable about its center relative to a support frame. The shaft includes a vertical post that pivots within a cylindrical bushing mounted to the support frame. The rollers include an outwardly decreasing taper at the outer ends, which operate to cause the rollers mounted to the elongate shaft to pivot in a horizontal plane about the vertical axis to steer a misaligned belt back toward its proper downstream travel path. The rollers can be mounted to the shaft either in a trough configuration or in a non-troughed or flat configuration. In the troughed configuration, the rollers pivot about the vertical axis while maintaining their orientation relative to the vertical pivot axis. This configuration is limited, however, because the disclosed system is not capable of tilting or raising an outer end of the roller to provide additional steering control over a mistracking belt.

Another belt tracking device that avoids the use of sensor rollers has an inclined pivot axis of the rollers located upstream of the rollers. This belt tracker is disclosed in <CIT>and includes an idler roller that is pivotal about a pivot axis that is upwardly inclined in the downstream direction. In this regard, when a conveyor belt mistracks toward one end portion of the idler roller, the drag forces acting downstream on the idler roller end portion increase, urging the end portion to shift downstream, while the downstream tilt of the pivot axis causes the idler roller end portion to also simultaneously shift downwardly under the increased weight of the mistracked belt passing over the end portion. Thus Parker's belt tracker utilizes the weight of the conveyor belt and drag forces acting on the end portion toward which the belt is mistracking to energize the idler roller to pivot about the pivot axis. However, the Parker belt tracker is limited because the tilt of the pivot axis restricts its use to belts that travel in a single direction.

A belt tracking apparatus is disclosed in <CIT> assigned to the Applicant herein. The belt tracking apparatus has an inclined pivot axis. However, the pivot axis is located downstream of the idler tracking roller so that when the tracking roller pivots about the included pivot axis, the one end portion of the roller that shifts downstream will also simultaneously shift upwardly for urging the mistracking belt back toward its correct travel path. The belt tracking apparatus of the `<NUM> publication also relies on engagement between an edge of the belt and the corresponding one of the sensor rollers to generate the energizing force for pivoting the tracking roller so that its end portion is shifted downstream and upwardly. Further, because the tracking roller pivots about an inclined pivot axis, shifting of the roller end portion upwardly will be dictated by the angle of the inclination of the pivot axis and the amount of downstream shifting of the roller end portion. In other words, the inclination of the pivot axis defines a predefined relationship between the amount of downstream shifting of the tracking roller end portion and the amount of upward shifting thereof when the tracking roller is pivoted for correcting a mistracking conveyor belt. This can require that greater energizing force be generated from the sensor roller for actuating the pivoting of the tracking roller since it simultaneously has its end portion shifted both downstream and upwardly. In addition, the use of sensor rollers and an inclined pivot axis restricts use of the '<NUM> publication tracking apparatus to conveyor belts that travel in a single direction.

Another known belt tracking apparatus is disclosed in <CIT> assigned to the Applicant herein. The disclosed apparatus includes a support frame for mounting the apparatus to the conveyor belt system, a tilt channel device mounted to the support frame so that the tilt channel device can shift laterally and tilt relative to the support frame, and a roller assembly mounted to the tilt channel device so as to be rotatable and pivotable. Accordingly, the frame assembly is configured to allow the reaction force from the conveyor belt caused by the downstream shifting of an end portion of an idler roller due to mistracking of the conveyor belt for directing or steering the belt back toward its correct travel path to be used for energizing a tilting action of the idler roller to raise the downstream end portion thereof.

<CIT> discloses a bi-directional, self-energizing tracking apparatus according to the preamble of claim <NUM>.

The invention provides a bi-directional, self-energizing tracking apparatus according to claim <NUM>. The apparatus utilizes downstream shifting of an end portion of an idler roller due to mistracking of the conveyor belt for directing or steering the belt back toward its correct travel path and a reaction force from the belt due to the steering thereof for energizing a tilting action of the idler roller to raise the downstream end portion thereof. In this manner, the tilting of the idler roller is not mechanically coupled to the downstream shifting of the roller end portion since it is the steering action that first generates the reaction force in the belt against the shifted idler roller which is used as the actuation or energizing force for tilting the idler roller. By mechanically separating the downstream shifting and tilting actions of the roller, an inclined pivot axis for the idler roller such as provided in prior belt tracking devices is avoided allowing the belt tracking apparatus herein to be bi-directional for use with conveyor belts that may be run in opposite travel directions.

Also, the energizing force for tilting the idler roller is independent of the energizing force for downstream shifting of the idler roller end portion thus allowing the tracking apparatus to generate an amount of tilting of the idler roller that is in proportion to the resistance of the belt being steered by the shifted idler roller. In other words, if the belt provides little resistance to being steered back toward its correct travel path by the shifted idler roller, then the idler roller will not be tilted to the same degree as when there is greater resistance by the mistracking belt to the steering action. In this instance, the tilting of the idler roller will be greater so that the tilted idler roller creates another influence on the mistracking belt, in addition to the steering action, that will urge the belt back towards its correct travel path.

In one aspect, not part of the present invention, a tracking apparatus is provided that includes an idler roller for supporting the conveyor belt and a frame assembly that is configured to operatively mount the idler roller to conveyor structure. The frame assembly is further configured to allow the idler roller to shift when the conveyor belt is mistracking so that one end portion of the idler roller is further downstream than the other end portion thereof for directing the belt back toward the correct travel path. The frame assembly is also configured to allow the idler roller to use a reaction force from the belt as the belt is being directed by the shifted idler roller to actuate the idler roller to be tilted for urging the belt back toward the correct travel path. Rather than defining a predetermined relationship between the amount of downstream shifting of the idler roller and the amount of upward shifting thereof as in prior tracking apparatuses, the tracking apparatus herein utilizes a reaction force from the belt as it is being directed by the idler roller that is shifted to have one of its end portions further downstream than the other end portion as the actuation force for tilting the idler roller for urging the belt back toward the correct travel path. In this manner, the tilting action of the idler roller is in proportion to the amount of resistance generated by the belt to the steering action undertaken by the shifted idler roller. In particular, the end portion of the tilted idler roller has been shifted in a direction transverse to the surface of the conveyor belt, e.g. raised upwardly into the belt when the idler roller is installed underneath the conveyor belt, so as to increase the force exerted by the idler roller end portion on the engaged surface of the belt.

In another form, not part of the present invention, the tracking apparatus includes an idler roller having opposite end portions and a neutral position when the conveyor belt is traveling along the correct travel path, a central support shaft configured to operatively mount the idler roller to conveyor structure with the central support shaft extending along a longitudinal axis transverse to the correct travel path of the conveyor belt, and a tilt coupling operably connected between the central support shaft and to the idler roller with the tilt coupling disposed entirely within the idler roller. The tilt coupling is configured to allow the idler roller to pivot with respect to the central support shaft when the conveyor belt is mistracking so that one of the end portions of the idler roller is further downstream from the neutral position thereof and further downstream than the other end portion of the idler roller for directing the conveyor belt back toward the correct travel path. The tilt coupling also allows the idler roller to use a reaction force from the conveyor belt as the conveyor belt is being directed by the pivoted idler roller to actuate the idler roller to be tilted so that the one end portion of the idler roller is shifted in a direction transverse to the surface of the conveyor belt so as to increase the force exerted by the idler roller end portion on the conveyor belt surface for urging the conveyor belt back toward the correct travel path. In one form, the tilt coupling allows for tilting of the idler roller only as a result of the pivoting of the idler roller, but tilting does not occur with the idler roller in the neutral position thereof. The tilt coupling is configured for shifting of the idler roller along the longitudinal axis of the central support shaft, such as via one or more rollers between the tilt coupling and the central support shaft, and causes the idler roller to tilt when the idler roller is shifted along the longitudinal axis of the central support shaft. The tilt coupling has a central throughopening and the central support shaft extends through the central throughopening with the tilt coupling mounted thereto. The idler roller of the tracking apparatus is configured to urge the mistracking conveyor belt back toward a correct travel path without the use of sensor or edge rollers, and regardless of whether the conveyor belt is traveling in one direction or an opposite direction. In addition, the idler roller may be operably connected to the tilt coupling via a pivot connection having a pivot axis extending through the tilt coupling and about which the idler roller rotates. The idler roller may be connected to the tilt coupling via an inner tube member that is pivotally connected to the tilt coupling via the pivot connection, with the idler roller rotatably mounted about the inner tube member such that the idler roller is configured for simultaneous rotation and pivoting about the tilt coupling.

According to the invention, a bi-directional, self-energizing tracking apparatus for redirecting a mistracking conveyor belt back toward a correct travel path whether the conveyor belt is traveling in one direction or in an opposite direction is provided. The tracking apparatus includes an idler roller that engages a surface of the conveyor belt and a frame assembly for operatively mounting the idler roller to conveyor structure. A shiftable connection of the frame assembly for operably connecting the idler roller to the frame assembly is provided that is internal to the idler roller for shifting the idler roller relative to the frame assembly in response to the mistracking conveyor belt. The shiftable connection is configured to allow the idler roller to pivot about a pivot axis such that an end of the idler roller is shifted downstream relative to a neutral position thereof corresponding to the conveyor belt traveling along a correct travel path, and allows the idler roller to tilt such that the downstream end of the idler roller is shifted in a direction transverse to the surface of the conveyor belt so as to increase the force exerted by the idler roller end on the conveyor belt surface for guiding the mistracking conveyor belt back toward a correct travel path.

The shiftable connection is configured to allow the idler roller to translate along a translation axis transverse to the one conveyor belt direction and preferably configured to tilt the idler roller when the idler roller translates along the translation axis. In some forms, the shiftable connection is configured to pivot the idler roller about the pivot axis prior to tilting the idler roller such that in operation the idler roller only tilts when the idler roller is pivoted. The shiftable connection may take the form of a tilt coupling that is shiftably mounted about a central support shaft of the frame assembly for allowing the idler roller to tilt with respect to the central support shaft. An inner tube member may be pivotally mounted to the tilt coupling, with the idler roller rotatably mounted about the inner tube member such that the idler roller is configured to simultaneously rotate and pivot about the tilt coupling. The tilt coupling can be configured for translation laterally along the central support shaft, and the tilt coupling and the central support shaft have stops therebetween to limit lateral translation and tilting of tilt coupling relative to the central support shaft by a predetermined amount. Sealing members may be provided at either end of the idler roller for keeping debris or foreign materials from fouling the shiftable connection disposed within the idler roller.

In one form, not part of the present invention, the tracking apparatus has an outer idler roller that supports the conveyor belt and a frame assembly including a tilt device mounted to a central support shaft and about which the outer idler roller is mounted to allow the outer idler roller and tilt device to shift relative to the central support shaft. The outer idler roller includes lateral end portions that taper down toward a reduced diameter end thereof to cause the idler roller and tilt device to shift relative to the central support shaft so that one end of the outer idler roller is further downstream than the other end when the conveyor belt mistracks toward the one end for steering the conveyor belt back toward the correct travel path. The central support shaft extends across the conveyor belt and is operatively configured to be mounted to conveyor structure along the outer side portions of the conveyor belt. The tilt device tilts the outer idler roller with respect to the central support shaft as the outer idler roller receives a reaction force from the conveyor belt when the idler roller and tilt device are shifted for steering of the mistracking conveyor belt so that the idler roller is tilted and the downstream idler roller end is raised relative to the other idler roller end to urge the conveyor belt towards the correct travel path.

The self-energizing tracking apparatus does not rely on sensor rollers for generating either the actuation or energizing force for shifting of the idler roller for steering the conveyor belt back towards the correct travel path or for tilting of the idler roller for urging the conveyor belt back towards the correct travel path. Instead, it is the frictional engagement of the mistracking conveyor belt with the tapered end of the idler roller that generates the actuation force for shifting thereof when the belt mistracks. When the idler roller is shifted for steering the mistracking conveyor belt, a reaction force from the conveyor belt is received by the idler roller, which is used as the actuation force for causing the tilt device to tilt the idler roller relative to the central support shaft. In this manner, the idler roller end is also raised so that in addition to being steered back toward the correct travel path, the idler roller is tilted to urge the conveyor belt back toward the correct travel path. Since the tracking apparatus does not need to employ sensor rollers for generating its energizing or actuation forces for shifting and tilting the idler roller, the tracking apparatus is bi-directional in that it can be used without being reconfigured for correcting the travel path of the belt whether it is traveling in one direction or in a direction opposite to the one direction.

In one form, the tilt device takes the form of a tilt coupling about which the idler roller is rotatably connected to allow the idler roller to rotate relative to the tilt coupling. The rotatable connection can be in the form of one or more roller bearing assemblies between an inner tube and the outer roller that allows the roller to rotate relative to the tilt device. The inner tube is also pivotally mounted to the tilt coupling at a pivot connection so that the inner tube and idler roller may pivot about the tilt coupling about a pivot axis that is orthogonal to the rotational axis of the idler roller. The tilt coupling is translateably mounted to the central support shaft via rollers that allow the tilt coupling to roll therealong to provide low friction support to the tilt coupling as it shifts relative to the central support shaft and as the tilt coupling tilts along with the idler roller. Accordingly, via the roller's rotatable connection with the inner tube, the inner tube's pivotal connection with the tilt coupling, and the tilt coupling's translatable and tiltable connection with the central support shaft, the idler roller is capable of complex and polyaxial shifting energized solely by the belt to correct the travel path of the belt. Advantageously, all of the moveable connections between the idler roller and the support shaft are internal to the idler roller, resulting in a significantly lighter, mechanically simplified tracking apparatus with fewer parts that is efficient to produce, and offers simplified installation and maintenance. In addition, because the moving parts of the frame assembly are internal to the roller, the moving parts are advantageously protected from the elements and from debris or other foreign material, offering improved reliability and performance.

In another aspect, not part of the present invention, a method for urging a mistracking conveyor belt back toward a correct travel path is provided including mounting an idler roller disposed about a central support shaft to conveyor structure such that the idler roller is operably supported by the central support shaft extending through the idler roller and is configured to rotate about the central support shaft, as well as pivot and tilt with respect thereto, the idler roller having outer end portions adjacent outer side surface portions of the conveyor belt, pivoting the idler roller with respect to the central support shaft so that one end portion of the idler roller is further downstream than the other end portion in response to conveyor belt mistracking toward the one end portion of the idler roller, steering the conveyor belt back toward the correct travel path with the pivoted idler roller. The method further includes causing the idler roller to undergo a tilting action with respect to the central support shaft so that the idler roller end portion that has been shifted downstream shifts in a direction transverse to the corresponding outer side surface portion of the conveyor belt so as to increase the force exerted by the idler roller end portion on the corresponding outer side surface portion of the conveyor belt in response to a reaction force exerted by the conveyor belt being steered by the idler roller, and urging the conveyor belt to generally shift in a lateral direction away from the transversely shifted downstream idler roller end portion back toward the correct travel path due to the tilting of the idler roller. Causing the idler roller to undergo a tilting action may include shifting the idler roller along a longitudinal axis of the central support shaft. In one form, mounting the idler roller includes securing the central support shaft to the conveyor structure such that the central support shaft is fixed to the conveyor structure so as to remain stationary. The central support shaft in some forms may be mounted to the conveyor structure with the central support shaft between an upper carry run and a lower return run of the conveyor belt. The tracking apparatus is configured to urge the conveyor belt to generally shift in a lateral direction away from the transversely shifted downstream idler roller end portion back toward the correct travel path due to the tilting of the idler roller with the belt traveling in a second direction opposite from a first direction such that the idler roller urges a mistracking conveyor belt back toward a correct travel path regardless of whether the belt is traveling in the first or second directions.

In another form, not part of the present invention, a method for urging a mistracking conveyor belt back toward a correct travel path includes positioning an idler roller having tapered outer end portions under outer side portions of the conveyor belt, shifting the idler roller so that one of the idler roller outer end portions is further downstream than the other outer end portion in response to conveyor belt mistracking toward the one idler roller due to greater engagement of the corresponding belt outer side portion with the tapered outer end portion of the idler roller, steering the conveyor belt back toward the correct travel path with the shifted idler roller, tilting the idler roller by tilting a tilt device internal to the idler roller so that the outer end portion that has been shifted downstream is raised relative to the other end in response to a reaction force received from the conveyor belt being steered by the idler roller, and urging the conveyor belt to generally shift in a lateral direction away from the raised outer end portion back towards the correct travel path due to the tilting of the idler roller.

As illustrated in <FIG>, a conveyor belt tracking apparatus <NUM> is adapted to be used with an endless conveyor belt system positioned under a conveyor belt <NUM> thereof to track the belt <NUM> along a generally longitudinal belt travel path, the center line <NUM> of which is indicated at the Z axis in <FIG>. To this end, the belt tracking apparatus <NUM> will be described with respect to correcting lateral misalignment of the belt <NUM> relative to the center line <NUM>. The belt tracking apparatus <NUM> is generally symmetrical such that the structure and function of the apparatus <NUM> on one lateral side will be applicable to the opposite side as well.

As shown in <FIG>, the belt tracking apparatus <NUM> includes a roller assembly <NUM> having a roller <NUM> being mounted for rotation about its longitudinal axis L to a frame assembly <NUM> including an elongate central support shaft <NUM> extending through the roller <NUM> about which the roller <NUM> rotates. The roller <NUM> has a symmetrical configuration with a cylindrical main portion <NUM> and tapered outer or lateral end portions <NUM>, <NUM>. The tapered outer end portions <NUM>, <NUM> have an outwardly decreasing diameter relative to the main portion <NUM>. In the disclosed embodiment, the roller <NUM> is comprised of an outer cover <NUM> made of urethane mounted about an outer roller tube <NUM>, shown in <FIG>. The outer cover <NUM> includes the tapered outer end portions <NUM>, <NUM> and is configured to be replaceable due to wear caused by friction with the belt <NUM>. In other forms, the outer cover <NUM> and outer roller tube <NUM> could be one integral piece.

The frame assembly <NUM> is configured to operatively mount the roller <NUM> to the conveyor structure (not shown) and to allow the roller <NUM> to shift when the conveyor belt <NUM> is mistracking so that one of the end portions <NUM>, <NUM> of the roller <NUM> is further downstream from a neutral position (shown in <FIG>) than the other end portion <NUM>, <NUM> to direct the belt <NUM> back toward the correct travel path. The frame assembly <NUM> is further configured to allow the roller <NUM> to use a reaction force from the belt <NUM> as the belt is being directed by the shifted roller <NUM> to actuate the roller <NUM> to be tilted so that the one end portion <NUM>, <NUM> shifted downstream is also raised upwardly relative to the neutral position to further urge the belt <NUM> back to the correct travel path. The tilting and raising up of the roller end portion <NUM>, <NUM> only occurs as a result of the downstream shifting of the one end portion <NUM>, <NUM>, but does not occur with the roller <NUM> in the neutral position.

The roller <NUM> is thus capable of compound rotary motion relative to the conveyor structure, i.e., rotation about its longitudinal axis L, pivoting about a central pivot axis P orthogonal to longitudinal axis L, translation along a support shaft longitudinal axis S, and tilting relative to the support shaft <NUM>. The rotary motion of the roller <NUM> and the pivoting, translation, and tilting of components of the frame assembly <NUM> as described hereinafter combine to urge the belt <NUM> back toward the center to correct a misalignment in the event the belt <NUM> becomes misaligned to one side as shown in <FIG> and <FIG>. As will be described in further detail below, the self-correcting ability of apparatus <NUM> can be accomplished without requiring the belt <NUM> to actively contact sensor rollers to force a change in orientation of the roller <NUM>. This form of belt correction is known as "self-energizing," and preserves the integrity of the belt edges more effectively than the non-self-energizing types of belt trackers that require contact with sensor rollers or the like. Furthermore, the symmetrical nature of the apparatus <NUM> allows for the apparatus to be used with a belt travelling in both a first longitudinal belt travel direction and a reversed longitudinal direction opposite the first direction.

It should be noted that the term "symmetrical" refers to the general orientation of the components of the apparatus <NUM> when the apparatus is in a neutral position, and refers to the symmetry on the left and right side of a central longitudinal axis Z that is generally parallel to the direction of belt travel, as well the symmetry on the fore and aft side of a lateral axis X that is generally parallel to the length of the support shaft <NUM>. As will be described in further detail, when the belt <NUM> becomes misaligned to one side, the roller <NUM> will pivot about its connection to the support shaft <NUM>, which ultimately causes the roller <NUM> to translate laterally to the side of the misalignment relative to the support shaft <NUM> and at the same time causes the corresponding end portion of the roller <NUM> to tilt upwardly. In such a condition, the overall apparatus <NUM> will no longer be symmetrical, but will return to its symmetrical orientation after the belt <NUM> has returned to its intended path of travel with roller <NUM> in its neutral position. The symmetrical orientation allows for correcting the belt <NUM> in the same manner regardless of the direction of travel of the belt <NUM> or the particular side to which the belt <NUM> becomes misaligned.

Furthermore, the terms "lateral" or "laterally" refer to a lateral direction along the X axis. The terms "fore," "forward," "aft," and "rearward" refer to a longitudinal direction along the Z axis orthogonal to the X axis, and relative to the direction of belt travel, so that forward refers to the direction of belt travel and rearward refers to the direction opposite belt travel. The terms "upward" or "vertical" refer to the vertical Y axis orthogonal to the X and Z axes. Tilting of the roller <NUM> refers to vertical movement of one end of the roller, but which may also include a lateral component, a rotational component, or a combination thereof.

As shown in <FIG>, the frame assembly <NUM> includes the support shaft <NUM> fixedly mounted to the conveyor frame via conveyor frame mounting brackets <NUM> and support shaft brackets <NUM>. The conveyor frame mounting brackets <NUM> have longitudinally extending mounting slots 24a for positional adjustment in the fore and aft directions, and vertically aligned mounting holes 24b for positional adjustment of the belt tracking apparatus <NUM> in the vertical direction, allowing the apparatus <NUM> to be mounted in a plurality of orientations relative to the conveyor frame structure with suitable fasteners. The central support shaft <NUM> extends through a gap between the vertically extending legs 24c of the conveyor frame mounting bracket <NUM> and is mounted to thereto via the support shaft brackets <NUM>, which are disposed about the support shaft <NUM> at either end thereof. The lateral position of the roller <NUM> is adjustable by shifting the support shaft <NUM> laterally from side to side within the support shaft brackets <NUM>. Once in the correct lateral position, the support shaft <NUM> is fixed to the support shaft brackets <NUM> with suitable fasteners.

As shown in <FIG>, the frame assembly <NUM> further includes an inner tube <NUM> which is movably mounted to the support shaft <NUM> via a tilt device or coupling <NUM> of the frame assembly <NUM>, which allows the roller <NUM> to pivot, translate, and tilt in response to forces transmitted to the roller <NUM> by a mistracking belt <NUM>, and will be described in greater detail below. As shown in <FIG>, roller bearing assemblies <NUM> are mounted about an outer surface <NUM> of the inner tube <NUM> at outer lateral ends thereof. The outer tube <NUM> is rotatably mounted to the inner tube <NUM> via the roller bearing assemblies <NUM> such that the outer tube <NUM>, together with the outer cover <NUM>, i.e. the roller <NUM>, may rotate about a common longitudinal axis L about which inner tube <NUM> and roller <NUM> extend. Sealing members are provided to protect the moveable members of the frame assembly <NUM> from debris while allowing the moveable members to shift with respect to the support shaft <NUM>. For example, conical bellows <NUM> of a flexibly resilient material, e.g. elastomeric or rubber material, are positioned over the ends of the inner tube <NUM> and over the support shaft <NUM> to keep debris or other foreign materials from entering the inner tube <NUM> and fouling the tilt coupling <NUM> and other internal components, while allowing the moveable components of the frame assembly <NUM> to shift, pivot, or tilt. The inner tube <NUM> is provided with a radial groove about its exterior surface adjacent each end for mating with a corresponding internal projection of the inboard end of bellows <NUM> for securing the bellows about the end of the inner tube <NUM>, while the outboard end of the bellows <NUM> relies on a friction fit for connection to the support shaft. However, clamping members or other securing means may be used to secure the bellows <NUM> in place. The conical bellows <NUM> may expand and contract along the support shaft axis S, as well as flex or shift in any direction to compensate for the movement of the moveable components of the frame assembly <NUM>. The central support shaft <NUM> also includes end caps <NUM> to keep debris from entering the shaft <NUM>.

Accordingly, in a preferred form, all of the components of the frame assembly <NUM>, other than the support shaft <NUM> that extends beyond the ends of the idler roller <NUM>, and the mounting bracketry <NUM>, <NUM>, are located within the idler roller <NUM>. Thus, the moveable components of the frame assembly, i.e., the inner tube <NUM> and tilt coupling <NUM>, as well as their associated components, including pivot pads <NUM> and tilt coupling rollers <NUM>, <NUM>, are internal to the roller <NUM> and are enclosed therein by the conical bellows <NUM> and by end caps <NUM> enclosing the central support shaft <NUM>. The moveable frame assembly components are thus protected from fouling by debris (such as the conveyed material), as well as from corrosion and wear caused by the elements when the conveyor is located in an outdoor environment.

Inner tube <NUM> does not rotate about its longitudinal axis like the outer tube <NUM>, but is mounted to the tilt coupling <NUM> via a pivot connection <NUM> to allow the inner tube <NUM> rotate with respect to the tilt coupling <NUM> about pivot axis P, which is orthogonal to longitudinal axis L. With the roller <NUM> in its neutral or non-tilted orientation, the pivot axis P extends vertically while the longitudinal axis L extends horizontally in the lateral direction across the conveyor belt <NUM>. As shown in <FIG>, the pivot connection <NUM> is formed between upper and lower surfaces <NUM>, <NUM> of the tilt coupling <NUM> and pivot pads <NUM> that are pivotally mounted to the tilt coupling outer upper and lower surfaces <NUM>, <NUM> via pivot bolts <NUM> that are aligned along pivot axis P. A pivot strip <NUM> of a thin material, such as UHMW polyethylene, is provided between the pivot pad <NUM> and the outer surfaces <NUM>, <NUM> of the tilt coupling to reduce friction therebetween.

The pivot pads <NUM> have a generally rectangular footprint that matches the shape of the upper and lower surfaces <NUM>, <NUM> of the tilt coupling. The pivot pads <NUM> include laterally spaced apart inner tube engagement portions <NUM> for matingly engaging with the inner surface <NUM> of the inner tube <NUM>. The tube engagement portions <NUM> extend transversely across each end of the pivot pads <NUM> and have arcuate engagement surfaces <NUM> with a radius that substantially matches the inner radius of the inner tube inner surface <NUM> to mate with the inner tube <NUM>, as shown in <FIG>. Accordingly, the pivot pads <NUM> engage with the inner tube inner surface <NUM> at the four inner tube engagement portions <NUM>. The inner tube <NUM> is fastened to the tilt coupling <NUM> via the pivot pads <NUM> with pivot bolts <NUM> and pivot bushings <NUM> so that the inner tube <NUM> is permitted to pivot about pivot bolts <NUM> which extend along pivot axis P while also fixing the inner tube <NUM> against lateral shifting with respect to the tilt coupling <NUM>. The pivot bolts <NUM> are received in centrally located and axially aligned upper and lower threaded bosses <NUM> which extend outwardly from the respective upper and lower outer surfaces <NUM>, <NUM> of tilt coupling and which define pivot axis P. Each pivot pad <NUM> includes a central aperture <NUM> through which the threaded boss <NUM> extends forming a pivotal connection about which the pivot pads <NUM> rotate or pivot. Accordingly, the inner tube <NUM> and pivot pads <NUM> are configured to pivot together about pivot axis P.

The inner tube <NUM> is permitted to pivot to a limited degree due to the interference between the inner surface <NUM> of the inner tube <NUM> and the support shaft <NUM>. Accordingly, the relative sizes of the central support shaft <NUM> and the length and diameter of the inner tube <NUM> may affect the maximum amount of pivoting of the apparatus <NUM>. For example, the support shaft <NUM> may be a <NUM> (<NUM>") square tube and the inner tube <NUM> may have an outer diameter of approximately <NUM> <NUM>-(<NUM>/<NUM> inches) and a length of between <NUM> - <NUM> (<NUM>-<NUM> inches), depending on the width of the conveyor belt <NUM>. In a currently preferred form, the inner tube <NUM> is permitted to pivot up to approximately <NUM> degrees in either direction about the pivot axis P, and more preferably up to approximately <NUM> degrees. In other forms, stops could be provided on the support shaft, inner tube, or tilt coupling to permit the desired amount of pivoting.

As best shown in <FIG> and <FIG>, the tilt coupling <NUM> is formed from separate upper and lower portions <NUM>, <NUM> that are fastened together by threaded fasteners in corresponding matching bosses 53a, 53b on each of the upstream and downstream sides of each of the coupling portions <NUM>, <NUM>. The upper and lower coupling portions <NUM>, <NUM> when assembled have a generally octagonal profile so that the coupling <NUM> is an internal tilt coupling <NUM> of the frame assembly <NUM> that fits within the cylindrical interior of the inner tube <NUM>. The internal tilt coupling <NUM> has a tube-like configuration with an interior passage <NUM> extending between open ends <NUM> of the coupling <NUM> to allow the central support shaft <NUM> to extend therethrough. Although the tilt coupling <NUM> could be formed of an integral monolithic material, dividing the coupling into two or more portions, such as separate upper and lower portions allows for ease of manufacturing, as well as installation and maintenance because the coupling <NUM> can be removed or installed on the support shaft <NUM> without removing the shaft from the mounting brackets <NUM>, <NUM>. In a preferred form, the tilt coupling portions <NUM>, <NUM> are formed of cast stainless steel. In another form shown in <FIG>, the tilt coupling <NUM> is formed of several machined pieces that are fastened together.

The tilt coupling <NUM> is configured to both translate laterally as well as tilt with respect to the central support shaft <NUM>. The support shaft <NUM> includes a plurality of rollers, including two upper rollers <NUM> and a lower roller <NUM> for engaging with the tilt coupling <NUM> along respective smooth rolling surfaces thereof. The support shaft <NUM> can be hollow so that the rollers <NUM>, <NUM> are rotatably mounted within the support shaft <NUM> with their axes of rotation extending orthogonally to the longitudinal axis of the shaft <NUM>. The support shaft <NUM> includes roller apertures 60a, 61a to allow a portion of the rollers <NUM>, <NUM> to extend beyond the outer surface of the support shaft <NUM> as shown in <FIG>. The lower roller <NUM> engages with and rolls along a flat interior surface <NUM> of the lower coupling portion <NUM>. The upper rollers <NUM> each engage with and roll along corresponding surfaces of the upper coupling portion <NUM>. In particular, the upper coupling portion <NUM> includes cantilevered ramp portions <NUM> extending from each end <NUM> of the upper coupling portion <NUM>, with an inclined ramp surface <NUM> on an interior side thereof. The inclined ramp surface <NUM> extends into the interior passage <NUM> of the tilt coupling <NUM> to a transition surface <NUM>, which extends between both inclined ramp surfaces <NUM>. The upper rollers <NUM> are each configured to roll and travel along the respective inclined ramp surface <NUM> and the transition surface <NUM>. Both ramp surfaces <NUM> are oriented to have an incline that is at the same angle of approximately <NUM> degrees with respect to the longitudinal axis of the tilt coupling <NUM> (which axis is parallel to the X axis when in the neutral position), although other configurations could be used.

As shown in <FIG>, in the neutral position, the lower roller <NUM> is centered inside the tilt coupling <NUM>, and the upper rollers <NUM> each engage the inclined ramp surfaces <NUM> at equal lateral distances from the central pivot axis P. When the belt <NUM> begins to mistrack and one edge of the belt moves closer to one lateral side of the roller than the other, the roller <NUM> and inner tube <NUM> will pivot about pivot axis P, which causes one of the outer ends of the roller <NUM>, <NUM> to move downstream. The resulting reaction force caused by the belt <NUM> on the skewed roller <NUM> causes the tilt coupling <NUM> to translate along the central shaft longitudinal axis toward the end of the shaft closest to the downstream end <NUM> of the roller <NUM>. At the same time, due to the inclined ramp surfaces <NUM> of the tilt coupling <NUM>, the tilt coupling also tilts as one of the upper rollers <NUM> rolls up the inclined ramp surface towards the transition surface <NUM> while the other upper roller <NUM> rolls down the opposite inclined ramp surface <NUM> toward its outermost extent, as shown in <FIG>. Preferably, stops <NUM> are provided on the support shaft <NUM> to limit the range of travel of the tilt coupling <NUM> and to keep the rollers <NUM> from rolling off the ends of the inclined ramp surfaces <NUM>. In other forms, the range of travel of the tilt coupling <NUM> could be limited by interference between the interior passage <NUM> of the tilt coupling <NUM> and the outer surface of the support shaft <NUM> or by stops engaging with portions of the roller <NUM> or inner tube <NUM>.

As shown in <FIG>, the tilt coupling <NUM> includes guide pads <NUM> which can have a disc shape and are mounted to the tilt coupling <NUM> in the interior passage <NUM> thereof at both the upstream and downstream sides thereof for slidingly engaging the upstream and downstream sides of the support shaft <NUM> and keeping the tilt coupling <NUM> aligned with the support shaft <NUM>. In particular, both the upper and lower portions of the tilt coupling <NUM>, <NUM> include two pairs of opposed guide pads <NUM>.

Having described the structure of the belt tracking apparatus <NUM> above, the operation of the apparatus <NUM> is described below.

As previously described, the belt tracking apparatus <NUM> is mounted to the belt conveyor structure via the conveyor frame mounting brackets <NUM>. The belt <NUM> is in the form of an endless belt having an upper carry run and a lower return run with the belt tracking apparatus <NUM> configured to be mounted below the generally flat lower return run of the belt <NUM>. However, the belt tracking apparatus <NUM> is also configured to be mounted above a lower return run of the belt <NUM> such that the idler roller <NUM> engages with the top side of the belt <NUM>, i.e. the side of the belt that does not engage with material to be conveyed. In this mounting configuration, the belt tracking apparatus <NUM> is rotated <NUM> degrees about the longitudinal axis S of the support shaft shown in <FIG> so that end portion of the idler roller <NUM>, <NUM> that is pivoted downstream, when tilted, will be shifted generally vertically downwardly, rather than upwardly, i.e., in a transverse direction to the surface of the belt so as to increase the force exerted by the idler roller end portion on the belt <NUM>.

The apparatus <NUM> supports or engages the belt <NUM> via contact with the roller <NUM>. When the center of the belt <NUM> is aligned along the centerline <NUM>, the belt <NUM> will contact the generally cylindrical central portion <NUM> of the roller <NUM> and similar sized-portions of each of the tapered outer end portions <NUM>, <NUM>. As the belt <NUM> is driven along its path, the contact between the belt <NUM> and the roller <NUM> will cause the roller <NUM> to rotate about its central axis L. More specifically, the roller <NUM> will rotate about the inner tube <NUM> via the rotation of the bearings <NUM> that are disposed about the outer ends of the inner tube <NUM>. While the belt remains generally centered on the centerline <NUM>, the roller <NUM> will rotate in a generally forward direction, and the longitudinal axis L of the roller <NUM> will be generally aligned with the longitudinal axis S of the support shaft <NUM>. With the belt <NUM> centered on the centerline <NUM>, the roller <NUM> may be referred to as being in the neutral position, which is shown in <FIG>. In the neutral position, the inner tube <NUM> is also oriented to extend generally parallel to the support shaft <NUM>. The tilt coupling <NUM> is generally not translated or tilted relative to the support shaft <NUM> as long as the apparatus <NUM> remains in its neutral position.

As shown in <FIG>, <FIG>, and <FIG>, in the event the belt <NUM> begins to track off center, or become misaligned, the belt tracking apparatus <NUM> will operate to urge the belt <NUM> back toward its centered position as further described below. As the belt tracking apparatus <NUM> is generally symmetrical, the operation of the correcting features of the apparatus <NUM> is generally the same whether the belt becomes misaligned to the right or the left. For purposes of illustration, the operation of the apparatus <NUM> will be described with respect to a lateral misalignment to the left. For reference, a left misalignment refers to the belt <NUM> becoming misaligned laterally to the left relative to the direction of the belt travel. While the description of the misalignment will be described with respect to a left misalignment, it will be appreciated that a misalignment to the right operates in the same manner. <FIG>, <FIG>, and <FIG> illustrate a misalignment of the belt <NUM> to the left, with the belt tracking apparatus <NUM> fully shifted, tilted, and rotated to correct the misalignment.

As the belt <NUM> begins to track off center and to the left, the greater amount of contact between the between the belt <NUM> and the left tapered outer end portion <NUM> of the roller <NUM> creating more friction therebetween will cause the roller <NUM> to have its left distal end be pulled downstream in the direction of the travel of the belt <NUM>, as described in further detail below. Because the roller's axis of rotation L is now skewed with respect to the downstream direction of travel of the belt <NUM> to steer the belt <NUM> back to the right toward its intended path of travel (shown in <FIG>), a reaction force from the belt <NUM> is generated to the left and transverse to the direction of belt travel on the roller <NUM>. This causes the roller <NUM>, inner tube <NUM>, and tilt coupling <NUM> to be translated to the left and the tilt coupling <NUM> simultaneously to tilt the inner tube <NUM> and roller <NUM> upward at the left side against the bottom side of the belt <NUM>.

As the tilt coupling <NUM> is urged to the left, it will shift relative to the support shaft <NUM>, which remains fixed to the conveyor structure. More specifically, the tilt coupling <NUM> will translate along rollers <NUM>, <NUM> rotatably mounted in the support shaft <NUM>. With the tilt coupling <NUM> shifting to the left, the upwardly inclined ramp surface <NUM> on the right side of the tilt coupling <NUM> will roll down the upper right roller <NUM> and the upwardly inclined ramp surface <NUM> on the left side of the tilt coupling will roll up the upper left roller <NUM>, causing the tilt coupling to tilt with its left end higher than the right end. The tilt coupling <NUM> eventually will abut the left stop <NUM> mounted to the lower side of the support shaft <NUM>, thereby limiting the amount of tilting and translation of the tilt coupling. However, the degree of tilt of the tilt coupling <NUM> may also be limited to interference between the interior of the tilt coupling <NUM> and the outside of the support shaft <NUM>. With the left side of the tilt coupling <NUM> lifted upward, the right side of the tilt coupling <NUM> thereby moves downward as shown in <FIG> and <FIG>. Corresponding movements in the inner tube <NUM> and the roller <NUM> necessarily result due to the interconnection of the inner tube <NUM> to the tilt coupling via pivot bolts <NUM>, and the connection of the outer tube <NUM> of the roller <NUM> to the inner tube <NUM> via the bearing assemblies <NUM>.

The slope of the inclined ramp surfaces <NUM> and amount of lateral travel allowed the tilt coupling <NUM> along the support shaft <NUM>, along with internal clearances of the tilt coupling <NUM> and/or the inner tube <NUM>, and the support shaft <NUM> are factors that will determine the amount of tilting of the tilt coupling <NUM>. For example, a steeper slope of the inclined ramp surfaces <NUM> would result in a larger degree of tilting. Similarly, extending the inclined ramp surfaces and allowing a larger amount of lateral travel of the tilt coupling <NUM> along the shaft <NUM> would also increase the degree of tilting of the tilt coupling <NUM>.

<FIG> illustrates the tilt coupling <NUM> having shifted its maximum amount to the left and its corresponding maximum amount of tilt. In one form, the tilt coupling is permitted to translate approximately <NUM> - <NUM> (<NUM>/<NUM> to <NUM>-<NUM>/<NUM> inches) to the left or right along the support shaft <NUM>, corresponding with a maximum angle of tilt β of the coupling of approximately <NUM> degrees and a raising of the corresponding end of the roller <NUM> of approximately <NUM> (<NUM>/<NUM> inch) above the horizontal neutral position.

With the tilt coupling <NUM> tilted due to the misalignment of the belt <NUM> to the left, the downward gravitational force and the tension on the belt <NUM> caused by the tilting will tend to urge the belt <NUM> back to the right and toward the center. However, the apparatus <NUM> will also operate to correct the belt by rotating the roller <NUM> via the pivotal connection <NUM> of the inner tube <NUM> with the tilt coupling <NUM> so that the distal end of the roller <NUM> at the side of the misalignment is dragged forward along the direction of the travel of the belt <NUM>, as further described below.

As previously described, when the belt <NUM> is travelling along its intended path, it is centered on and supported by the roller <NUM>. When the belt <NUM> becomes misaligned to one side, the misaligned side of the belt <NUM> will contact more of the tapered outer end portion <NUM> of the roller <NUM> at that side, causing the end <NUM> of the roller <NUM> to be pulled forward or downstream along the direction of belt travel.

More specifically, as the roller <NUM> is rotating about its axis L in response to the belt <NUM> travelling across the top of the belt tracking apparatus <NUM>, the roller <NUM> has a given rotational velocity. However, the linear (i.e. tangential) velocity of the roller <NUM> at the cylindrical main portion <NUM> is greater than the linear velocity at points on the tapered outer end portions <NUM>, <NUM> due to points on the tapered outer end portions <NUM>, <NUM> having a decreased radius relative to the cylindrical main portion <NUM>, i.e., points of the roller <NUM> closer to the center of rotation travel more slowly than points further away from the center, according to the equation v = ω*r, where v is velocity, ω is angular or rotational velocity of the roller, and r is the radius of the roller where the velocity is measured.

The belt <NUM> is traveling at a generally constant speed across its width, which generally corresponds to the linear velocity of the cylindrical main portion <NUM>. When the belt <NUM> becomes misaligned to the left, the belt <NUM> will still be travelling at its previous linear velocity. However, the points along the tapered outer end portion <NUM> are travelling at a linear velocity that is less than the belt <NUM>. Thus, when the belt <NUM> contacts a larger portion of the tapered outer end portion <NUM> on the left side than the tapered outer end portion <NUM> on the right side, the faster moving belt <NUM> will pull the slower moving tapered outer end portion <NUM> on the left side in the direction of the belt travel. As a result, the outer end <NUM> of the roller <NUM> on the left side moves forward or downstream. Because of the pivotal connection <NUM> between the roller <NUM> and inner tube <NUM> with the tilt coupling <NUM>, the roller <NUM> will thereby rotate about the pivot axis P so that when the left side of the roller <NUM> moves forward, the right side of the roller <NUM> moves rearward. This results in the rotational direction of the roller <NUM> being directed toward the right. The roller <NUM> will exert a rightward force on the belt <NUM> in this orientation, thereby steering the belt <NUM> to the right toward its centered position and, as previously described above, the belt <NUM> will exert a reaction force to the left transverse to the direction of the travel of the belt <NUM>, which causes the tilt coupling <NUM> to translate to the left and tilt the left end upwardly, operating to lift the left side of the roller <NUM>. <FIG> illustrates the rotation of the roller <NUM> at an angle α of approximately <NUM> degrees about the vertical Y axis corresponding with a downstream movement of the left end of the roller of approximately <NUM> (<NUM>/<NUM> inch).

As the belt <NUM> moves back to the right, the left edge of the belt <NUM> will move further away from the outer end of the tapered outer end portion <NUM>, and the direction of the belt travel will tend to re-orient the roller <NUM> so that the roller <NUM> is rotating in the direction of belt travel and the belt <NUM> will run along its intended path. In the event the belt <NUM> shifts too far to the right as it is being corrected from its misalignment to the left, the belt <NUM> will contact a larger portion of the right tapered outer end portion <NUM> of the roller <NUM> than the left tapered outer end portion <NUM>, causing the right side of the roller <NUM> to be pulled forward, thereby correcting the belt <NUM> in a similar manner to that described above.

The amount that the roller <NUM> will be able to rotate about the pivot connection <NUM> is limited by the clearance of the inner tube <NUM> with the support shaft <NUM> extending therethrough. For example, as the roller <NUM> is pulled forward at the side of the misalignment, the upstream portion of the inner tube <NUM> at the left lateral side of the apparatus will contact the upstream side of the support shaft <NUM>, while a downstream portion of the inner tube <NUM> on the right lateral side of the apparatus will contact the downstream side of the support shaft <NUM>, as shown in <FIG> and <FIG>.

Thus, the belt tracking apparatus <NUM> described above operates to correct a belt misalignment by pivoting, shifting, and tilting the roller <NUM> via the pivot connection <NUM> with the tilt coupling <NUM>, and via the translation and tilting of the tilt coupling <NUM> with respect to the central support shaft <NUM>, to direct the belt <NUM> back toward center. This combined pivoting, shifting, and tilting of the roller <NUM> provides a robust solution to conveyor belt systems that become misaligned. The correcting features of tilting and rotating are caused by the contact between the belt <NUM> and the rollers <NUM>, and do not require the edge of the belt <NUM> to contact any sensor rollers to cause the correction as in other configurations.

A further benefit of the belt tracking apparatus <NUM> is achieved by the symmetrical nature of the configuration. Because the apparatus <NUM> is symmetrical about its center while in the neutral position, the apparatus <NUM> can be installed on a conveyor belt system and operate on a belt <NUM> traveling in both a forward and rearward direction. This means that the belt tracking apparatus <NUM> is reversible. The belt <NUM> may be run in a first longitudinal belt travel direction to carry its payload in that direction, and may be subsequently reversed to deliver payload in the opposite direction. The belt tracking apparatus <NUM> may be installed at various points along the conveyor system without regard to the intended direction of the belt <NUM>. The belt tracking apparatus <NUM> may also be installed to engage the belt <NUM> from below or from above.

An alternate form of the belt tracking apparatus <NUM> is shown in <FIG>, which operates in the same manner to the belt tracking apparatus <NUM> disclosed in <FIG>. However, the components of the belt tracking apparatus <NUM> are sized and configured to accommodate wider belt widths, such as between <NUM> - <NUM> ( <NUM>-<NUM> inches). In general, like components and portions of the belt tracking apparatus <NUM> are labeled with the same number as belt tracking apparatus <NUM> with the addition of <NUM> to the number. For the sake of brevity, only the principle distinctions between the tracking apparatuses <NUM>, <NUM> will be discussed below.

As shown in <FIG>, one distinction between the belt tracking apparatus <NUM> and <NUM> is that the tilt coupling <NUM> is relatively longer than tilt coupling <NUM> to accommodate a corresponding wider width of the belt <NUM>, and is constructed from several machined pieces rather than an investment cast design having upper and lower portions <NUM>, <NUM>. In particular, the tilt coupling <NUM> includes opposing end rings <NUM>, <NUM> to which fore and aft side brace plates <NUM>, <NUM> and upper and lower support plates <NUM>, <NUM> are fastened. The end rings <NUM>, <NUM> define open ends of the tilt coupling <NUM> through which the central support shaft <NUM> extends. As shown in <FIG>, the tilt coupling <NUM> includes inclined ramp surfaces <NUM> disposed on a ramp member <NUM> that is fastened to the upper support plate <NUM>. In a currently preferred form, the ramp member <NUM> is made of alloyed steel and the brace plates and support plates <NUM>, <NUM>, <NUM>, <NUM> are made of mild cold rolled steel. Upper rollers <NUM> and lower roller <NUM> are rotatably mounted within the support shaft <NUM>. Each of the upper rollers <NUM> engages and is operable to roll along one of the ramp surfaces <NUM>, and lower roller <NUM> engages and is operable to roll along a flat interior surface <NUM> of the lower support plate <NUM>.

Claim 1:
A bi-directional, self-energizing tracking apparatus (<NUM>; <NUM>) capable of redirecting a mistracking conveyor belt (<NUM>) back toward a correct travel path whether the conveyor belt (<NUM>) is traveling in one direction or in an opposite direction, the tracking apparatus (<NUM>; <NUM>) comprising:
an idler roller (<NUM>; <NUM>) that engages a surface of the conveyor belt (<NUM>);
a frame assembly (<NUM>) for operatively mounting the idler roller (<NUM>; <NUM>) to conveyor structure;
a shiftable connection of the frame assembly (<NUM>) for operably connecting the idler roller (<NUM>; <NUM>) to the frame assembly (<NUM>) and being internal to the idler roller (<NUM>; <NUM>) for shifting the idler roller (<NUM>; <NUM>) relative to the frame assembly (<NUM>) in response to the mistracking conveyor belt (<NUM>), the shiftable connection being configured to allow the idler roller (<NUM>; <NUM>) to pivot about a pivot axis (P) such that an end (<NUM>, <NUM>) of the idler roller (<NUM>; <NUM>) is shifted downstream relative to a neutral position thereof corresponding to the conveyor belt (<NUM>) traveling along a correct travel path, and allow the idler roller (<NUM>; <NUM>) to tilt such that the downstream end (<NUM>) of the idler roller (<NUM>; <NUM>) is shifted in a direction transverse to the surface of the conveyor belt (<NUM>) so as to increase the force exerted by the idler roller (<NUM>; <NUM>) end (<NUM>, <NUM>) on the conveyor belt (<NUM>) surface for guiding the mistracking conveyor belt (<NUM>) back toward a correct travel path;
characterized in that
the shiftable connection is configured to allow the idler roller (<NUM>; <NUM>) to translate along a translation axis transverse to the one conveyor belt direction.