Abstract:
A bearing mount assembly for a powered roller conveyor of the type used in veneer dryers comprising a bearing mount base and a bearing holder, the base having a lower part with a vertical surface adapted to abut a cage angle and apertures for fastening it to a vertical face of the cage angle, an upper end of the base being in the shape of a yoke open at the top for locating the shaft of an upper roller, the bearing holder having a pocket for holding an arcuate section of a sleeve bearing, the base and holder having mating surfaces capable of locating the holder in a position where it supports the bearing in registry with the desired axis of rotation of the shaft of a lower roller.

Description:
[0001]    The invention relates to powered roller conveyors and, in particular, to improvements in bearing supports for conveyor rollers in board dryers. 
       BACKGROUND OF THE INVENTION 
       [0002]    Dryers used in manufacturing boards and panels such as veneer dryers employ roller conveyors to carry raw material through the dryer while it is exposed to forced hot air. In a veneer dryer, for example, the powered rollers carrying the material being dried are paired, one overlying the other so as to create a nip through which the material is conveyed. In conventional designs of veneer dryers and similar equipment, the rollers, shafts, bearings and sprockets are located in confined spaces. Sprocket driven roller shafts are ordinarily carried in carbon bearings and these bearings are in-board of the sprockets and roller chain. 
         [0003]    The bearings, due to their operating conditions and being impractical to lubricate require relatively frequent replacement, typically as often as once a year. The labor involved in replacing the bearings in existing prior art equipment is extensive. Each of the corresponding sprockets must first be removed, the spent bearings must be forced out of their cylindrical housing bores, the replacement bearings positioned in the bores, and the sprockets remounted. This procedure is done manually one bearing at a time. Oftentimes the sprockets, which are typically keyed and closely fitted to their shafts, will be frozen on the shafts and not easily removed. A percentage of conventional sprockets, because of corrosion, can be frozen on the shafts so tightly that it is necessary to destroy them to remove them from the shafts. This frequent loss of sprockets obviously adds to the operating costs of the dryer. 
       SUMMARY OF THE INVENTION 
       [0004]    The invention provides a bearing mounting system particularly suited for a veneer dryer style conveyor that enables worn roller shaft bearings to be removed and replaced with significant savings in labor, downtime, and parts costs. The bearing mount permits the bearings to be changed without requiring drive sprockets to be removed. This feature saves the time otherwise needed to loosen, remove and later reposition and tighten the sprockets or risking destruction of the sprockets in an effort to remove them. The system, in the illustrated embodiment, utilizes a bearing segment of 180 degrees or less, thereby enabling it to be removed and installed on a roller shaft radially rather than sliding it axially over the normal operating location of the temporarily removed sprocket. 
         [0005]    More specifically, the system includes a bearing mount assembly comprising a base and a holder. The base has a receiving zone with surfaces arranged to complement the configuration of the holder so as to allow the holder to self-align itself to the base. The bearing mount base is arranged to be bolted on a conventional cage angle and, as is conventional, has provisions for holding the shaft of the upper roller of the roller set. The base receives the holder, in which the bearing is disposed, radially from the space below the shaft. Extraneous assembly motion or gyration of the bearing holder is avoided and in an essentially intuitive manner, a technician can simply raise the bearing holder after roughly locating it under the lower roller shaft while biasing it against the mount base to properly position it in the receiving zone. 
         [0006]    In addition to affording a much simpler and quicker manner of replacing the spent bearings than has been heretofore available, the invention can reduce the cost of the bearings themselves since the volume of bearing material is cut at least in half when practicing the invention compared to full cylinder prior art bearings. The bearing holder, besides serving the primary function of carrying the radial forces on the bearing, automatically captures the bearing with the base to angularly and axially lock it in place without separate retaining elements. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]      FIG. 1  is a fragmentary perspective view, axially exploded, of a set of rollers of a veneer dryer style roller conveyor employing the invention; 
           [0008]      FIG. 2  is a fragmentary elevational sectional view of the conveyor looking in the conveying direction; 
           [0009]      FIG. 3  is a fragmentary side elevational view of the conveyor taken from the chain side; 
           [0010]      FIG. 4  is a fragmentary elevational view of the conveyor taken from the operator side; 
           [0011]      FIG. 5  is a perspective view of a bearing holder of the invention taken from a reference point corresponding to the inside of the conveyor; 
           [0012]      FIG. 6  is a perspective view of a bearing mount base of the invention, again taken from a reference point corresponding to the inside of the conveyor; and 
           [0013]      FIG. 7  is an elevational view similar to  FIG. 3  with the sprocket and chain removed to show constructional details of the relevant parts. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0014]    Referring now to the figures and, in particular, to  FIG. 1 , there is partially shown a powered roller conveyor  10  such as in a veneer dryer. The axes of pairs of rollers  11 ,  12  are horizontal and aligned in a common imaginary vertical plane. While only one set of rollers  11 ,  12  is illustrated, the conveyor  10 , as is conventional, has a series of identical roller sets or pairs evenly spaced along a conveying direction in a common horizontal plane, commonly referred to as a deck. The typical dryer will have several such decks spaced one above the other. Hot air is forced through the decks to dry material being conveyed between each pair of rollers  11 ,  12 . 
         [0015]    The rollers  11 ,  12  are carried on respective shafts  13 ,  14  projecting from both ends of the rollers. The lower roller shaft  11  has a sprocket  16  fixed by a key and set screw on one of its ends. The sprocket  16  and like sprockets on the other rollers of the same deck are all aligned with a common imaginary vertical plane extending in the conveying direction and are all driven by a single roller chain  17 . 
         [0016]    Powered rotation of the lower roller  11  is imparted to the upper roller  12 , in the opposite direction, by a pair of star gears  18  each fixed to a respective shaft  13 ,  14 . The side of the conveyor  10  in the forefront of  FIG. 1  is referred to as the chain side of the conveyor, while the far side is referred to as the operator side. The roller shafts  13 ,  14  are located adjacent their chain side ends by a bearing mounting unit or assembly  21  and at their operator ends by bearing mounting units  22 . The chain side bearing mounting unit  21  comprises a base  23  and a bearing holder  24  removably mounted on the base. Both bearing mounting units  21 ,  22  are constructed of ductile iron or other suitable material and are appropriately machined. 
         [0017]    The illustrated base  23  has an H-shaped profile when viewed in the axial direction of a roller. A lower opening  26  between lower legs  27  receives the shaft  13  and an opening  28  between upwardly extending arms  29  receives the upper shaft  14 . 
         [0018]    Lower ends of the legs  27  have aligned slots  31  sized to receive an upper edge of a frame element of the conveyor  10  referred to commonly as a cage angle  32 . Vertical side surfaces  30  of the slots  31  abut vertical faces of the cage angle  32 . The same cage angle  32  supports other bearing mount units or assemblies  21  on the same level or deck. The base  23  is bolted to the cage angle  32  by socket head cap screws  33  ( FIG. 7 ) in threaded holes  34  ( FIG. 6 ) preferably aligned with holes  35  ( FIG. 1 ) existing in the cage angle  32 . The threaded holes  34  can be arranged to align with the original cage angle holes  35  of a dryer installation enabling the bearing arrangement of the invention to be retrofitted to existing dryer conveyors. Additionally, set screws  36  ( FIG. 7 ) are threaded into tapped holes  37  ( FIG. 6 ) and tightened against the part of the cage angle  32  received in the slots  31  to ensure that the base  23  is firmly fixed on the cage angle. 
         [0019]    Vertical guide surfaces  38  of the legs  27 , facing each other, lie in planes parallel to the roller shafts  13 ,  14  and, at their upper ends terminate at horizontal stop surfaces  39 . Bridging the space between the horizontal surfaces  39  is an arcuate surface  41  that is concentric with the nominal axis of the lower shaft  13  and is of a radius large enough to ensure clearance with this shaft. The vertical and horizontal surfaces  38 ,  39  frame a boundary of a receiving zone or pocket  42  for the bearing holder  24 . 
         [0020]    The bearing holder  24  is in the form of a hollow cylindrical segment with an integral radially extending mounting flange  46 . At an end of the holder  24  remote from the flange  46 , is an integral radially inwardly extending lip  47 . The radius and axial length of an inside surface  48  of the holder  24  are proportioned to form a pocket that closely fits the corresponding outer dimensions of a bearing  49 . The mounting flange  46  has an inwardly facing flat surface  51  which lies in a plane transverse to the axis of the cylindrical surface  48 . The flange  46  is formed with holes  52  adjacent its ends and spaced to line up with tapped holes  50  in the base  23  straddling the receiving zone  42 . Preferably, upper surfaces  53  on the holder  24  lie in a plane that includes the axis of the cylindrical surface  48 . The bearing  49  has the form of a segment of a cylindrical shell and is formed of carbon for its self-lubricating and temperature resistant properties. 
         [0021]    With the bearing  49  in the holder  24 , the holder is removably held on the base  23  by two machine screws  54  assembled through the holes  52  in the flange  46  and threaded into the tapped holes  50  in the base  23 . 
         [0022]    On the operator&#39;s side of the conveyor  10 , the bearing mounting unit  22  locates the roller shafts  13 ,  14 . The illustrated mounting unit  22  is conveniently made as a ductile iron casting and mounted by machine screws on an angle  56  common to identical mounting units at each roller pair. The bearing mounting unit  28  has a bearing seat or pocket  57  to receive a bearing  48  that can be identical to the bearing  49  used at the chain side for supporting the lower roller shaft  13 . The upper roller shaft  14  is horizontally constrained between sides  58  formed in a forked upper area of the mounting unit  22  and is vertically supported by the lower roller  11  or material being conveyed through the nip between the rollers  11  and  12 . 
         [0023]    The site of the chain side bearings is crowded owing to the presence of the chain  17 , sprockets  16 , and chain guides (not shown) making access to this area difficult. The invention greatly reduces the time and effort to remove the shaft bearings  49  compared to prior art constructions wherein the sprockets must first be removed and then cylindrical shell bearings have to be driven out of their housings in which they are often frozen. 
         [0024]    At the chain side, a bearing  49  can be removed by simply removing the two machine screws or bolts  54  and dropping the holder  24  down away from the shaft  13  and then out from under the sprocket  16 . The shaft  13  can be temporarily blocked up until a new bearing  49  is in place. A worn bearing is relatively easy to remove from the holder pocket formed by the cylindrical surface  48  and lip  47  even if it becomes frozen in this area because a relatively limited surface contact area between the bearing and holder and because the bearing is largely exposed rather than being encircled by the holder. A new bearing  49  can be installed in the holder  24  by simply dropping it in the pocket formed by the surface  48  and lip  47 . Once it is set in the holder pocket, the new bearing  49  can be quickly installed on the bearing mounting base  23 . This procedure is accomplished by locating the holder  24  beneath the shaft  13  and against the base  23  and then, if necessary, juggling it back and forth in the conveyor direction until a projecting part  61  of the holder inward of the flange  46  and proximate to the base  23  falls into the slot existing between the vertical guide surfaces  38 . The projecting portion  61  of the holder  24  forward of the flange  46  is sized for a clearance fit between these vertical surfaces  38 . Once this forward or lead end  61  of the holder  24  is even partially in the slot between the vertical surfaces  38 , the holder is guided by these surfaces as it is raised into abutment between its upper surfaces  53  and the downwardly facing base stop surfaces  39 . At this time with the holder  24  retained in place manually or with a simple prop, the machine screws  54  can be installed and the job of replacing the bearing  49  is complete. The foregoing steps can be easily performed where the sprocket  16  remains in place on the respective shaft  13 . The bearing  49  is trapped against axial movement between the lip  47  and the base  23  and angularly against rotation by portions of the horizontal stop surfaces  39  at the top of the receiving zone  42 . The bearing  49  at the operator side can be changed by slightly elevating the shaft  13  at this end, popping out the worn bearing and replacing it with a fresh bearing and then lowering the shaft. The bearing  49  at this operator side can be retained by a screw threaded into a hole  59  on the outside of a vertical face of the bearing mounting unit  22 . While the illustrated bearings  49  are shown as half cylinders, i.e. subtending and arc of 180 or slightly less than 180 degrees, other bearing segment configurations are feasible. For example, the bearings  49  can be formed with an arc of 120 degrees or slightly less by appropriately configuring the bearing mounting units  21 ,  22  where they receive the bearings. 
         [0025]    It should be evident that this disclosure is by way of example and that various changes may be made by adding, modifying or eliminating details without departing from the fair scope of the teaching contained in this disclosure. The invention is therefore not limited to particular details of this disclosure except to the extent that the following claims are necessarily so limited.