Abstract:
A roller assembly for supporting a moving belt and including at least one roller mounted for rotation about a roller axis; and a support arrangement, the roller assembly being mounted on the support arrangement for pivotal displacement about a pivot point, characterized in that the belt tracking regulator includes guide means operable, in use, to constrain the pivotal displacement of the roller assembly to move in a plane containing the pivot and tilted at an acute angle with respect to a horizontal plane defined through the pivot point.

Description:
FIELD OF THE INVENTION 
   This invention relates to belts and, in particular, to conveyor belts. More specifically, the invention relates to a belt tracking regulator for use on conveyor belts. 
   BACKGROUND TO THE INVENTION 
   Several mechanisms exist for regulating the tracking of conveyor belts to ensure that a belt tracks true and does not wander laterally as it moves. Failure to track correctly may have costly consequences, including damage to the belt, the supporting frame, and spillage of material being transported. 
   A mechanism for regulating the tracking of a conveyor belt which is easy to install, requires low activating forces and low maintenance would accordingly be advantageous. It would also be advantageous to have a mechanism which does not operate by impacting or abrading the edge of the belt, since this leads to belt damage. 
   Bi-directional conveyor belts, in which the direction of belt travel may be reversed, require a higher level of alignment accuracy than belts, which travel in one direction only. 
   While this invention will be described with particular reference to the tracking of conveyor belts, it is to be understood that the invention can be used in a number of different applications such as the tracking of other endless belts and other endless flexible materials. 
   OBJECT OF THE INVENTION 
   The object of this invention is to provide a simple yet effective mechanism for regulating the tracking of conveyor belts, particularly a mechanism which is operable with bi-directional conveyor belts, which at least partly achieves the abovementioned objectives and alleviates the problems set out. 
   SUMMARY OF THE INVENTION 
   In accordance with this invention there is provided a belt tracking regulator including
         a roller assembly for supporting a moving belt and including at least one roller mounted for rotation about a roller axis; and   a support arrangement, the roller assembly being mounted on the support arrangement for pivotal displacement about a pivot point
 
characterized in that
   the belt tracking regulator includes guide means operable, in use, to constrain the pivotal displacement of the roller assembly to move in a plane containing the pivot and tilted at an acute angle with respect to a horizontal plane defined through the pivot point.       

   In a preferred embodiment of the invention, the belt tracking regulator has a plurality of longitudinally spaced rollers. The rollers may include at least one intermediate roller and two outer rollers, which may be angled with respect to the at least one intermediate roller to define a generally convex up curve and thereby provide a crowned support for a belt. Further preferably, the roller assembly has two laterally spaced parallel intermediate rollers. The rollers may be supported on a sub-frame. 
   The support arrangement may comprise a support frame on which is mounted a ball component of a ball joint, a complementary socket component of which is mounted on the sub-frame, thereby enabling the entire roller assembly to pivot with respect to the support frame about the ball component. It will be appreciated that the centre of the ball component defines the pivot point for the roller assembly. 
   The guide means may comprise a pin receivable in a mating groove formation attached to the support frame, the pin being attached to an end of one of the outer rollers. Preferably, the mating groove formation is adjustable to vary the inclination of the groove. The groove formation may be manually or automatically adjustable. Further preferably, the pin has a spherical head and the groove has a circular cross-section, the groove being shaped to entrap the head of the pin to prevent disengagement from the groove, but allowing the head to slide freely along the groove. Still further, the pin may be operable to telescope to allow the head and groove to remain engaged and the pin to slide freely as the roller assembly pivots under loading. 
   The invention extends to a belt tracking regulator including a roller assembly supported on a sub-frame, the roller assembly supporting a moving belt and including at least one roller mounted for rotation about a roller axis; and a support frame on which is mounted a ball component of a ball joint, a complementary socket component of which is mounted on the sub-frame for pivotal displacement about the ball component. 
   The invention further extends to a conveyor system including a plurality of roller assemblies, at least one of which is a belt tracking regulator as hereinbefore described. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will be described, by way of example only, with reference to the drawings in which: 
       FIG. 1  is a perspective view of a belt tracking regulator in accordance with the invention; 
       FIG. 2  is an elevation view of the belt tracking regulator of  FIG. 1 ; and 
       FIG. 3  is a plan view of the belt tracking regulator of  FIGS. 1 and 2 . 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   A belt tracking regulator  1  is shown in  FIGS. 1 to 3  and includes a support arrangement formed by a support frame  3  which may be attached to a conveyor belt frame (not shown) via bolts (not shown) at either end thereof. 
   In this description, the belt tracking regulator will be described as it is normally oriented in use as shown in the drawings. 
   The frame  3  has a horizontal cross bar  5  formed from a steel angle section, which is positioned with its apex  7  facing up, and welded at each end to a steel plate. Each plate  8  is bolted to a mounting bracket  9  having an upper inwardly bent flange  11 , the flange  11  having two elongate slots  13  extending therethrough, for receiving a bolt to connect into standard mounting holes (not shown) on a conveyor frame. The vertical distance between the tracking regulator  1  relative to the conveyor frame may be adjusted as there are a plurality of vertically spaced pairs of holes  14  on the bracket  9 , any of which may receive the bolt pair for connection to the steel plate  8 . 
   Extending upwardly from the centre of the cross bar  5  is a post  15  carrying a ball component of a ball joint  17  for mating with a complementary socket component  19  in a hitch  21  carried on a roller sub-frame  23 , which is described in more detail below. 
   Above the cross bar  5 , parallel to a plane defined by the conveyor belt, are a pair of spaced apart, parallel shafts  25  journalled at either end to a pair of flat elongate brackets  27 . In between the shafts  25  are a pair of spaced, parallel flat cross members  29 , the shafts  25  and cross members  29  defining a central rectangular space  31  therebetween. 
   On the outer side of each elongate bracket  27 , a U-shaped bracket  33  is fixed at either free end thereto in cantilever fashion and positioned centrally along the length of each bracket  27 . The U-shaped bracket  33  and the elongate bracket  27  to which it is fixed define an elongate rectangular space  35 . 
   A pair of outer shafts  37 , their axes collinear in plan view, are located in each elongate rectangular space  35  and are journalled at the elongate bracket  27  and at the closed end  39  of the U-shaped bracket  33 . The outer shafts  37  are angled downwardly with respect to the centre shafts  25  thereby supporting the belt in a crowned position. The angle of inclination is approximately 12 degrees in this embodiment, but it will be readily appreciated by a person skilled in the art that the angle of inclination may be varied from one application to another, depending on several factors including conveyor carrying capacity and belt length. Shafts  25  carry intermediate idler rollers  51  and shafts  37  carry outer idler rollers  49  and  51  rotatably mounted on the shaft via bearings thereby forming a roller assembly  52  for supporting a moving belt (not shown). 
   The rightmost mounting bracket  9 . 2  has a pin  41  projecting therefrom carrying a spherical head to provide the ball  43  of a ball-type joint. The pin is able to telescope to allow the ball  43  to move axially relative to the pin  41 . The ball  43  is accommodated in a cross-sectionally circular mating slot  45  in a housing  47  which, in turn, is rotatably secured to the mounting bracket  9 . 2 , its position being adjustable by way of an adjustment nut  46 . The slot  45  is linear and accordingly permits the ball  43  to move linearly thereinside. 
   In the central rectangular space  31 , a socket hitch  21  spans between the support members  29 , the socket  19  being shaped and dimensioned to pivotally accommodate the ball  17 . 
   Once installed, the inclination of the housing  47  with respect to the horizontal plane is set by a technician by rotating an adjusting bolt. It will be appreciated that when the belt tracking regulator  1  is used with a bi-directional conveyor system, the housing will be rotated by approximately 180 degrees each time the belt direction is reversed. In the drawings, the position of the housing  47  is shown for use with a belt moving in the direction of the arrow  48 . 
   In use, if the belt drifts off centre, an eccentric load is placed on either one of the outer idlers  49 , causing the entire roller assembly  52  to pivot about the pivot point, defined by the ball component  17 , so that the heavier side of the belt is lower than the lighter side. The pivot action is shown by arrows A and B. Importantly, when viewed in side view, as shown in  FIG. 2 , the increased load on one or other of the idler rollers  49  causes the roller assembly  52  to roll about an axis X through the pivot point, as shown by the arrows A, while simultaneously the roller assembly yaws about an axis Y, normal to axis X parallel to the direction of movement of the belt, as shown by the arrows B in  FIG. 3 . 
   As the roller on the lower, heavier, side is also caused to move away from the direction of movement of the belt, it contacts the belt after the roller on the other side. The belt moves back towards the belt which is on the lighter side causing the belt to retain its normal tracking alignment and the roller assembly  52  to return to its equilibrium position. Since the ball slot  45  may be rotated by 360 degrees relative to the mounting bracket  9 . 2 , the direction of the belt may be reversed, the housing  47  and its slot rotated appropriately without it being necessary to disassemble the entire mechanism. 
   Several modifications to this embodiment are possible without departing from the scope of the invention. For example, the outer rollers need not be inclined relative to the centre rollers. Also, other pivoting mechanisms may be used instead of a ball and socket mechanism. The adjusting means may also be varied and may be automatically operated. Further, the pivot point need not be at the centre of the tracking mechanism. 
   It will be readily appreciated that this invention provides a simple yet effective means for tracking conveyor belts, including reversible belts, to ensure that a belt travels along the centre line of its path on the conveyor frame.