Abstract:
A support stand for supporting an elongated rotary drum for rotation about a longitudinally extending drum axis includes a lower portion extending upwardly from a base to a tilted top extending in a plane of tilt; a correspondingly tilted upper portion mounted atop the lower portion, and a carrying roller rotatably mounted on the upper portion for rotation about a roller axis while a riding ring extending coaxially around the drum bears against and rides in rolling contact on the roller. The upper portion is rotatably positionable relative to the lower portion about a skew axis perpendicularly intersecting the plane of tilt at a fixed point. The skew axis substantially radially intersect the drum axis. As well, the skew axis substantially radially intersects the roller axis. A mechanism for adjusting the amount of skew and an indicator for displaying the amount of skew are also disclosed. Further, rotary drum supported by a plurality of such stands and a method of aligning the stands with respect to the drum is also disclosed.

Description:
BACKGROUND TO THE INVENTION 
     The present invention relates to roller supported rotary drums of the type used for agitating, mixing, heating and/or otherwise handling material (for example, particulate matter). More particularly, the present invention relates to rotary drums having riding rings that are supported on carrying rollers for rotation on a drum axis diverging slightly from a horizontal axis, and which typically require the rollers to be skewed with respect to the riding rings. 
     The prior art is replete with designs for stands having carrying rollers used to carry rotary drums during rotation about a drum axis that slopes slightly from the horizontal. The slope is necessary to ensure that material being handled by the drum properly travels lengthwise within the drum during the handling process. Typically, a drum will include riding rings extending coaxially around the drum for receiving the required support from the carrying rollers. However, by reason of the slope and the force of gravity, special measures have to be taken to confine axial movement of the drum. Unless restrained, the natural tendency of the drum will be to move axially downhill as the drum rotates. 
     The primary mechanisms for confining axial movement of a drum are thrust rollers. They act on the riding rings and assist to maintain the rings in a centered position on the carrying rollers. However, they are often not designed to resist the full thrust that a rotary drum and its load may impart—at least not for any significant period of time. To address this limitation, it is commonplace to skew a drum&#39;s carrying rollers in relation to the riding rings in a manner that urges the drum axially uphill as the drum rotates; in effect counteracting the force of gravity. The skew takes place about a skew axis, viz. the axis on a line drawn from the center of rotation of a roller and radially intersecting the drum axis. However, if the skewing is insufficient, a thrust roller may still encounter significant force leading to premature failure. Conversely, if the skewing is excessive, then excessive wear and tear may take place on the riding ring and the carrying roller. 
     Various mechanisms have been devised for supporting carrying rollers and for adjusting the skew of carrying rollers relative to riding rings. However, they are often quite complex. As well, in the case of many designs, the adjustment of a roller&#39;s skew actually requires a series of adjustment steps; for example, first moving one side of a roller&#39;s support (e.g. to draw it forwardly by a small amount), then moving the other side of the roller&#39;s support (e.g. to push it backwardly by a small amount), then having to repeat such steps until a desired degree of skew rotation has been achieved. The problem is that translational as well as rotational movement may occur unless such adjustments are made with extreme care and precision. With repeated adjustments, serious misalignments with other rollers that should be similarly adjusted can gradually develop. The costly process of realigning an entire installation may then become necessary. 
     A primary object of the present invention is to provide a new and improved support stand for a rotary drum, the stand including a carrying roller that can be precisely skewed with respect to a riding ring of the drum without allowing translational movement. 
     A further object of the present invention is provide in association with such a support stand, an adjustment mechanism that permits desired skew adjustments to be easily made. 
     Yet another object of the present invention is to provide in association with such a support stand a means for easily discerning the amount of skew. 
     A still further object of the present invention is to provide a rotary drum supported by such support stands, and a method for aligning the stands with respect to the drum. 
     SUMMARY OF THE INVENTION 
     In a broad aspect of the present invention, there is provided a support stand for supporting an elongated rotary drum for rotation about a longitudinally extending drum axis, the drum including a riding ring extending coaxially around the drum for receiving such support. The stand includes a lower portion extending upwardly from a base to a tilted top which extends in a predefined plane of tilt. A correspondingly tilted upper portion is rotatably mounted atop the lower portion, and is rotatably positionable relative to the lower portion about a skew axis perpendicularly intersecting the predefined plane of tilt at a fixed point. A carrying roller is rotatably mounted on the upper portion for rotation about a roller axis while the ring bears against and rides in rolling contact on the roller with the skew axis substantially radially intersecting the drum axis. As well, the skew axis substantially radially intersects the roller axis. 
     In a preferred embodiment, the upper portion of the stand is constrained to rotate relative to the lower portion about the skew axis by a center pin extending from the lower portion to the upper portion. The center pin has a center pin axis coinciding with the skew axis. By definition, this arrangement dictates that the skew axis intersects the plane of tilt at a fixed point, that point being the point where the center pin axis likewise intersects the plane of tilt. 
     Adjustment to a desired position of rotation may be achieved in various ways. An adjustment mechanism that is both rugged and simple comprises a resistance block mounted to the lower portion of the stand and an opposed pair of adjustment bolts, each bolt being threadingly engaged with an associated support bracket mounted to the upper portion of the stand. The bolts are aligned on a common axis that extends tangentially in relation to the skew axis, and the resistance block extends upwardly between the bolts. Each bolt is screwable within its support bracket to bear against the resistance block and thereby urge rotation of the upper portion of the stand relative to the lower portion of the stand about the skew axis. When a desired position of adjustment has been achieved, it may be secured in various ways such as with locking bolts. 
     In a preferred embodiment, the support stand includes an associated indicator for displaying the amount of rotation about the skew axis of the upper portion of the stand relative to the lower portion of the stand. This amount may be indicated in degrees, minutes, millimeters, or other units of measurement. The particular units of measurement are not critical. Those skilled in the art will understand that a suitable indicator may take various forms ranging from purely mechanical arrangements to electronic or electro-optical position sensing devices coupled to analog or digital readouts. In a preferred embodiment the indicator is a mechanically rugged arrangement comprising a measuring scale visibly marked on one portion of the stand and a pointer directed to the scale from the other portion of the stand. As the upper portion of the stand rotates relative to the lower portion about the skew axis, the pointer moves relative to the scale and the amount of rotation thus can be seen. 
     Advantageously, first and second pairs of such stands may be used in combination with a rotary drum of the foregoing type, the drum including first and second longitudinally spaced riding rings extending coaxially around the drum. The first pair of stands is associated with the first riding ring and provides support to the drum from opposed sides of the first riding ring. Similarly, the second pair of stands is associated with the second riding ring and provides support to the drum from opposed sides of the second riding ring. Each of the stands has upper and lower portions and a carrying roller as described above, and preferably each includes an indicator as described above for displaying the amount of its rotation about its skew axis. The riding ring associated with each stand bears against and rides in rolling contact on the stand&#39;s roller, the skew axis of the stand substantially radially intersecting both the roller axis and said drum axis. 
     In another aspect of the present invention, there is provided a method of providing roller support for an elongated rotary drum rotatable about a longitudinally extending drum axis, the drum including first and second longitudinally spaced riding rings extending coaxially around the drum, the method comprising: 
     (a) for each riding ring, providing a pair of stands for supporting the drum from opposed sides of the ring, each of the stands comprising: 
     (i) a lower portion extending upwardly from a base to a tilted top lying in a plane of tilt; 
     (ii) a correspondingly tilted upper portion rotatably mounted atop the lower portion, the upper portion being rotatably positionable relative to the lower portion about a skew axis perpendicularly intersecting the plane of tilt at a fixed point; 
     (iii) a carrying roller rotatably mounted on said upper portion for rotation about a roller axis, the riding ring associated with the stand bearing against and riding in rolling contact on the roller, the skew axis substantially radially intersecting both the roller axis and the drum axis; and, 
     (iv) an indicator for indicating the amount of rotation of the upper portion of the stand relative to the lower portion of the stand about the skew axis from an initial datum, 
     (b) rotating the upper portion of each of the stands about its associated skew axis to a position such that the indicated amount of rotation relative to its lower portion is the same as for all stands. 
     Normally, the initial datum for a stand will correspond to zero degrees of relative rotation between the upper portion of the stand and the lower portion of the stand. When all four stands are at their initial datum and initially aligned with the drum, then the rollers will be fully squared (viz. in full face contact) with the riding rings. Typically, it is contemplated that such an initial alignment will be performed as a preliminary step on a new installation or, if significant wear and tear has occurred, as an initial step in the process of refurbishing or realigning an old installation. In a preferred embodiment, initial alignment comprises the step of aligning the stands with the drum such that: 
     (a) the fixed point of intersection between the skew axis and the plane of tilt of the stands define the corners of a rectangle; 
     (b) the roller axis of a first one of the rollers is axially aligned with the roller axis of a second one of the rollers, and extends parallel to the drum axis; and, 
     (c) the roller axis of a third one of the rollers is axially aligned with the roller axis of a fourth one of the rollers, and extends parallel to the drum axis. 
     However, for reasons well understood by those skilled in the art, it often will be necessary for the drum axis of a rotary drum to diverge by a few degrees from true horizontal, the amount of divergence depending on the particular task at hand. It is then unsatisfactory for the rollers to be fully squared with the riding rings. There should be a suitable degree of skew. The present invention is particularly well adapted to enable desirable suitable skew adjustments to be made easily made without otherwise placing stands out of their initial alignment with a drum. 
     The foregoing and other features and advantages of the present invention will now be described with reference to the drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a representational side elevation view of an aggregate treatment plant incorporating a rotary drum supported by support stands in accordance with the present invention. 
     FIG. 2 is a top view illustrating the positions and initial orientations of four support stands in accordance with the present invention, when used in a plant such as that shown in FIG.  1 . The bases of the stands all lie in the same plane, and the view is taken in a plane parallel to the base plane. 
     FIG. 3 is a detail view, partially cut-away, taken in a plane perpendicular to the drum axis in FIG. 1, and just before one the support stands shown in FIG.  1 . 
     FIG. 4 is a front elevation view of a part of a support stand in accordance with the present invention, the view being taken in a plane perpendicular to the plane of tilt of the stand. 
     FIG. 5 is a top view of the stand shown in FIG. 4, the roller, roller shaft and pillow blocks that appear in FIG. 4 having been removed for the purpose of illustration. 
     FIG. 6 is an enlarged detail section view of the adjustment mechanism shown in FIGS. 4 and 5. 
     FIGS. 7A to  7 C illustrate an indicator for displaying the amount of rotation of the upper portion of the support stand shown in FIG. 4 relative to the lower portion of the support stand. 
     FIGS. 8A and 8B are representational views showing the tending direction of linear movement of a rotary drum as a function of its direction of rotation and the skew orientation of supporting rollers. 
    
    
     DETAILED DESCRIPTION 
     The aggregate treatment plant generally designated  200  in FIG. 1 represents one example of a practical use for the present invention. It is an example where moisture laden material such as damp or wet sand is fed to a rotary drum for moisture removal and ultimately discharged from the drum in a dried condition. 
     The plant includes a generally rectangular frame  201  mounted atop piers  202 ,  203 . Pier  203  is slightly higher than pier  202 . Hence, frame  201  is sloped at a small angle α with respect to horizontal ground  204 . Plant  200  further includes a conventional elongated rotary drum  300  which is driven by conventional means (not shown) to rotate about drum axis a 1 . The drum is longitudinally aligned with the frame. Hence, like the frame, axis a 1  is sloped at a small angle α with respect to ground  204 . In operation, drum  300  receives aggregate material through a conventional auger feed  310  and discharges the treated material through a conventional outlet  320 . Hot air is introduced to the drum through conventional ducting  330  from a hot air source (not shown). 
     Drum  300  includes conventional first and second longitudinally spaced riding rings  302 ,  303  extending coaxially around the drum. Four substantially identical support stands generally designated  10   a ,  10   b ,  10   c ,  10   d  (stands  10   c ,  10   d  being hidden from view in FIG. 1 but visible in FIG. 2) are mounted atop frame  201  and work in pairs to support drum  300  for rotation about drum axis a 1 , each on a carrying roller  60 . As indicated in FIG. 1, stands  10   a ,  10   b  are accessible by workers along a railed walkway  340 . A similar walkway (not shown) is provided on the opposite side of plant  200  for access to stands  10   c ,  10   d.    
     As best seen in FIG. 3, stands  10   a ,  10   c  work as a pair to provide support to drum  300  from opposed sides of riding ring  302 . Although not shown in the same detail as stands  10   a ,  10   c  in FIG. 3, stands  10   b ,  10   d  (shown generally in FIG. 2) work similarly as a pair to provide support to drum  300  from opposed sides of riding ring  303 . 
     Details of Stand Construction 
     For the purpose of discussion, the following description will be largely focused on stand  10   a  as depicted in FIGS. 3-5. However, apart the fixed positioning of stands  10   a ,  10   b ,  10   c  and  10   d  in relation to each other on frame  201 , it will be understood that the description of stand  10   a  will apply in generally the same manner to any one of the stands. 
     Stand  10   a  comprises a lower portion  20  extending upwardly from a base  22  to a tilted top (plate  24 ) which extends in a plane of tilt p 1 . A correspondingly tilted upper portion generally designated  30  is mounted atop lower portion  20 . Upper portion  30  is rotatably positionable relative to lower portion  20  about a skew axis a 2  perpendicularly intersecting the plane of tilt p 1  at an fixed point  32 . 
     In more detail, base  22  of lower portion  20  is secured by welding to frame  201 . Upper portion  30  comprises a lower plate  34  which flatly abuts plate  24  of lower portion  20 , a roller  60  carried on roller shaft  61 , and a pair of conventional pillow blocks  65 ,  66  within which shaft  61  is journalled. Each pillow block is secured through its base by mounting bolts  67  to an associated support stand  70 ,  71 . Support stands  70 ,  71  are welded to the upper surface of lower plate  34 . Roller  60  together with its shaft  61  is rotatable on roller axis a 3 . The abutment interface between plates  24 ,  34  includes a layer of grease or other suitable lubricant to minimize friction between the abutting surfaces. 
     Upper portion  30  is constrained to rotate relative to lower portion  20  about skew axis a 2  by a center pin  40  extending from lower portion  20  to upper portion  30 . Center pin  40  is secured in position by a snap ring  41 , the axis of the center pin coinciding with skew axis a 2 . Fixed point  32  referenced above is necessarily on axis a 2  midway along the center pin in plane p 1 . 
     In the position shown in FIG. 3, both roller axis a 3  and drum axis a 1  show as points. Thus the two axes are in parallel and there is zero degrees of relative rotation about skew axis a 2  between the upper and lower portions  20 ,  30  of stand  10   a.  In effect, roller  60  has no skew in below, this is not a normal operating position. However, it is a useful starting point when a stand is being aligned for normal operations. 
     As shown in FIG. 4, but better seen in FIGS. 7A to  7 C, the amount of rotation about skew axis a 2  is displayed by an indicator comprising a measuring scale  90  marked on a thin plate  91  (viz. like a nameplate) secured to the outer perimeter of plate  24 , and a pointer  92  directed to the scale—the pointer being visibly marked on a thin plate  93  (again like a nameplate) secured to the outer perimeter of plate  30 . Scale  90  includes a center or “0” marking for indicating zero degrees or no relative amount of rotation between the upper and lower portions of stand  10   a  about skew axis a 2  (see FIG.  7 A), a first series of markings on one side of the “0” marking for indicating a progressive amount of rotation in one direction (e.g. clockwise rotation—see FIG. 7B) about skew axis a 2 , and a second series of markings on the opposite side of the “0” marking for indicating a progressive amount of rotation in the opposite direction (e.g. anticlockwise rotation—see FIG. 7C) about skew axis a 2 . 
     Whether or not there is any degree of relative rotation between the upper and lower portions of stand  10   a , it readily will be discerned from FIG.  4  and the foregoing description that skew axis a 2  substantially radially intersects both drum axis a 1  and roller axis a 3 . 
     Skew Adjustment 
     From a practical point of view, it is desirable to provide a simple means to adjust the amount of rotation of upper portion  30  of stand  10   a  about skew axis a 2 , and to provide a simple means to secure the adjustment once it has been made. In this regard, stand  10   a  includes a rugged adjustment mechanism generally designated  50 , and three locking bolts  58  the latter of which serve to secure a desired position of adjustment once it has been made. 
     Referring to FIGS. 4,  5  and  6 , it will be seen that adjustment mechanism  50  comprises an opposed pair of adjustment bolts  51 ,  52  which are threaded through and carried by support brackets  53 ,  54  mounted on plate  34  of upper portion  30 , and which extend on a common axis  59  tangentially (see FIG. 5) in relation to skew axis a 2 . Either adjustment bolt can be screwed through its support bracket without effect until its distal end begins to bear against a resistance block  55  which is mounted on plate  24  of lower portion  20  and extends upwardly through opening  36  in plate  34  of upper portion  30 . Block  55  is secured to the upper surface of plate  24  by a strong filet weld  56 . 
     Locking bolts  58  extend downwardly from upper portion  30  through elongated slots  38  in plate  34  to threadingly engage plate  24  of lower portion  20 . When bolts  58  are loosened, upper portion  30  may be rotated relative to lower portion  20  about skew axis a 2 , the distance of travel being limited by the arc length of slots  38 . When bolts  58  are tightened, plate  34  is drawn against plate  24  and the amount of rotation becomes fixed. 
     The operation of adjustment mechanism  50  will be readily apparent. To adjust the amount of rotation of upper portion  30  relative to lower portion  20 , the first step is to loosen locking bolts  58  and to screw one of adjustment bolts  51 ,  52  sufficiently away from resistance block  55  to permit the desired amount rotational movement. Then, for example, if it was desired to rotate upper portion  30  anticlockwise in the view shown in FIG. 5, adjustment bolt  51  would be screwed away from block  55  as illustrated by gap  57  in FIG.  6 . The other adjustment bolt (in this example, bolt  52 ) would then be screwed towards resistance block  55 , ultimately to push with significant tangential force against the block. Since block  55  is affixed to lower portion  20 , and since lower portion  20  is immovable, the result would be an equal and opposition reaction urging anticlockwise rotation. Finally, when the desired amount of anticlockwise rotation was achieved, locking bolts  58  would be retightened. 
     In the foregoing example, it should be noted that the amount of screwing torque required on bolt  52  typically will be substantial because the portion of the weight of drum  300  carried by stand  10   a  typically will be substantial. However, the required torque of course is mitigated by the presence of grease or other lubricant at the abutment interface between plates  24 ,  34  (see above). 
     Installation and Operational Alignment 
     Whether installed on a frame such as frame  200  or on some other platform, the positioning of stands  10   a ,  10   b ,  10   c ,  10   d  with respect to each other should be as indicated in FIGS. 2 and 3. As shown in FIG. 2, the stands are aligned such that fixed points  32  where the skew axes of the stands intersect the planes of tilt of the stands are aligned to define the four corners of a rectangle. Parallel lines s 1 , s 2  and parallel lines s 3 , s 4  represent the sides of the rectangle that is so defined. 
     As shown in FIG. 3, opposed stands  10   a ,  10   c  are positioned such that fixed points  32  are at the base of a triangle. The base of the triangle has a length corresponding to s 1 . The apex of the triangle is on drum axis a 1 . Skew axis a 2  of stand  10   a  coincides with and leads on one side of the triangle from fixed point  32  of stand  10   a  to drum axis a 1 . Skew axis a 2 ′ of stand  10   c  coincides with and leads on the opposed side of the triangle from fixed point  32  of stand  10   c  to drum axis a 1 . Although not shown explicitly, opposed stands  10   b ,  10   d  satisfy the same criteria mutatis mutandis. 
     In FIG. 3, the angle between skew axes a 2  and a 2 ′ is indicated as angle β. Preferably, angle β is about 60 degrees. This provides a broad base of support for drum  300  while avoiding undue lateral forces from the weight of drum tending to separate stands  10   a ,  10   c.    
     In FIG. 2, each stand  10   a ,  10   b ,  10   c ,  10   d  is shown with zero degrees of relative rotation between the upper portion of the stand and the lower portion of the stand. Hence, the axis of roller  60  of stand  10   a  aligns with the axis of roller  60  of stand  10   b  along line s 5 . Likewise, the axis of roller  60  of stand  10   c  aligns with the axis of roller  60  of stand  10   d  along line s 6 . When stands  10   a-   10   d  are first installed this normally will be the initial alignment between the roller axes. Indeed, the alignment of the roller axes on lines s 5 , s 6  rather than the alignment of fixed points  32  on lines s 3 , s 4  can be used as one of the criteria for overall proper alignment. In either case, the result will be substantially the same. But, if the alignment is achieved using the roller axes as the criteria, then it is important to ensure that there is no relative rotation between the upper and lower portions of the support stands during the alignment procedure. 
     For reasons indicated in the above background discussion, and again well understood by those skilled in the art, a fully squared alignment as shown in FIG. 2 will not suffice for normal operations unless the tendency of drum  300  to move axially downhill is fully resisted by a thrust roller. In the present case, and although not shown, plant  200  includes a conventional thrust roller to bear against riding ring  302  in a conventional manner. But, as is commonplace, it is not designed to fully resist the thrust that drum  300  and its load may impart. Accordingly, it is necessary for rollers  60  of stands  10   a ,  10   c  to be skewed with respect to riding ring  302  and for the rollers  60  of stands  10   b ,  10   d  to be skewed by the same amount in relation to riding ring  303 . If it is taken that drum  300  is rotating in the direction indicated by arrow  350  in FIG. 8A (looking representationally towards the tops of the rollers), then rollers  10   a-   10   d  are all skewed anticlockwise by a small amount as indicated by arrows  351  in FIG.  8 A. Alternatively, if it is taken that drum  300  is rotating in the direction indicated by arrow  352  in FIG. 8B, then rollers  10   a-   10   d  are all skewed clockwise by a small amount as indicated by arrows  353 . The necessary direction of skew will be readily apparent to those skilled in the art. In any case, the effect of the skew should be to urge drum  300  unhill (viz. from left to right along axis a 1  in FIG. 1) as indicated by arrows  360  in FIGS. 8A,  8 B. 
     The actual amount of required skew will depend on various factors well understood by those skilled in the art and common in the design of rotary drum installations. Obviously the angle α is an important factor. However, since the overall engineering can be very complex, on site testing mitigated by experience is not an uncommon approach. If the angle α is relatively small, the amount of skew will be correpondingly small. 
     In operation, the amount of skew for any given roller  60  should be substantially the same as for all other rollers  60 . This should be the result following initial installation of stands  10   a ,  10   b ,  10   c ,  10   d  and adjustment of the stands&#39; rollers on their associated skew axes, and it should be the result following any subsequent readjustments that may be made due to changing operating conditions. Workers are able to efficiently make such adjustments with stands  10   a ,  10   b ,  10   c ,  10   d  because the only allowed movement is rotational movement of upper portions  30  of the stands on their respective skew axes, and the amount of such rotation is precisely indicated by measuring scale  90  on each of the stands. Translational movements cannot occur without moving the stands themselves. Thus, misalignments between the stands cannot be introduced by the actions of workers who merely are making skew adjustments. 
     Variations 
     A variety of modifications, changes and variations to the invention are possible within the spirit and scope of the following claims, and will undoubtedly occur to those skilled in the art. The invention should not be considered as restricted to the specific embodiment that has been described and illustrated with reference to the drawings.