Abstract:
A bearing mounting system for a roller conveyor used in a hot air dryer, comprising an elongated bearing support cartridge having an elongated base with individual bearing carriers distributed between the ends of the base and each being arranged to carry a bearing sleeve segment of the type that has a bearing surface that lies in an imaginary cylinder such that an axis of the bearing surface lies in a horizontal plane perpendicular to the length of the cartridge and corresponds to the axis of rotation of a roll of the conveyor, the cartridge having mounting elements distributed at least on its ends for mounting to a frame of the dryer, the individual bearing carriers being installable and removable on and off the dryer frame only as a unit with other portions of the cartridge. The bearing sleeve segments and bearing carriers can be provided with interlocking grooves and tabs to stabilize the positioning of the bearing sleeve segments while allowing a relatively loose fit between the bearing sleeve segments and the bearing carriers.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The invention relates to roller conveyors and, more particularly, to improvements in bearing systems for the conveying rollers of hot air dryers. 
       PRIOR ART 
       [0002]    Industrial forced hot air dryers are used in the manufacture of sheet or board-like products, such as drywall, ceiling tile, wood-based panels, rigid insulation, and various other building products. These dryers typically use rollers to convey raw, moisture laden material through the dryer while hot air is circulated through the dryer so that excess moisture is removed and the material is converted from a wet layer to a more rigid self-supporting intermediate or final product. It has long been customary to rotationally support the conveyor rollers on carbon sleeve-like bearings. Originally, the bearings were configured to completely encircle the roller shafts. In more recent times, half sleeves have been employed. Also in recent times, polytetrafluoroethylene as well as ceramic material have been used to make roller shaft bearings. The carbon and polytetrafluoroethylene materials are characterized by being low in friction, abrasion-resistant, and resistant to thermal degradation in the hot air environment found in the subject dryers. 
         [0003]    A typical dryer has several vertically spaced levels or decks with the rollers all being parallel to each other and at each deck being spaced along a common imaginary horizontal plane that extends through the dryer. The bearings are usually supported in individual brackets that are each secured to dryer frame members often called cage angles by pairs of bolts. Thus, the regular practice is to provide a bearing mount at each roller end that is wholly independent from the other bearing mounts. While this technique has served the industry for decades, if not nearly a century, it has disadvantages which include associated manufacturing costs of the dryer frame and bearing mounts and the labor involved in assembling and securing individual bearing units. 
       SUMMARY OF THE INVENTION 
       [0004]    The invention provides improvements in bearings and bearing mounts for roller conveyors of industrial dryers. Bearings of the present invention take the general form of partial cylindrical sleeves or arcuate segments and can include axially oriented slots that serve to stabilize the bearing during service. In a preferred version of the bearing, the segments subtend an arc that is somewhat less than 180 degrees and can be about 120 degrees, for example. The invention further provides a bearing system in which a plurality of bearing segment carriers are disposed on a common base, typically at a regular spacing between one another. The disclosed unitary base and multiple carrier system enables a whole section of bearing carriers for one side of a deck to be manufactured and subsequently installed with reduced manufacturing costs and reduced assembly time. 
         [0005]    The disclosed bearing system includes a novel bearing retainer capable of holding multiple bearing segments in place at respective bearing carriers. The retainer can be held in operational position and released from this position by manipulating a limited number of fastening elements thereby retaining or releasing multiple bearing segments in an expeditious manner. This feature makes the original assembly of a conveyor deck quicker and, later reduces the effort required to release the bearing segments for inspection and for replacement when a bearing is excessively worn. Furthermore, with the disclosed versions of the unitary bearing carrier base and unitary bearing retainer, the bearing segments can be removed and replaced with minimal effort involving the quick release of the retainer, limited lifting of the associated roller, and ejection of a spent bearing with its new replacement. That is, a new bearing is positioned on a side of the base remote from the roller and is aligned coaxially with the spent bearing. With the roller shaft lifted slightly out of its operating position, the new bearing is pushed against the worn bearing causing the latter to be ejected from the respective bearing carrier pocket. 
         [0006]    The bearing segment affords several advantages, including a considerable savings in material over a full circumference bearing. The bearing surfaces at the ends of the arc are at a considerable incline, i.e. about 30 degrees from the horizontal allowing dust and other debris to shed and be carried off by the effects of gravity and vibration thereby protecting the actual interface area between the bearing support surface and the shaft. The axial or longitudinal slots in the wall of the bearing at the arcuate ends are engaged by surfaces of the bearing retainer. The parts forming these surfaces are, while being proportioned to provide a relatively loose mutual fit at rest, are arranged to prevent rotation of the bearing and, importantly, to minimize skewing of the bearing such that its axis does not become out of parallelism with the shaft to a degree that is detrimental to the performance or life of the bearing. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]      FIG. 1  is an exploded perspective view of parts of a bearing system incorporating aspects of the invention; 
           [0008]      FIG. 2  is a plan view of a blank used to make an elongated base of the bearing cartridge assembly of the invention; 
           [0009]      FIG. 3  is a side elevation of the base after it has been formed into an elongated inverted U-shape; 
           [0010]      FIG. 4  is an end view of the base; 
           [0011]      FIG. 5  is a plan view of a blank used to make a bearing retainer of the bearing cartridge assembly; 
           [0012]      FIG. 6  is a side elevational view of the bearing retainer after it has been formed into an elongated inverted U-channel; 
           [0013]      FIG. 7  is an end view of the bearing retainer; 
           [0014]      FIG. 8  is a partial side elevational view of a cartridge assembly constructed in accordance with the invention; 
           [0015]      FIG. 8A  is a fragmentary elevational view of the bearing cartridge assembly mounted on a cage angle and portions of a roller and roller shaft in their respective assembled positions when supported by a bearing of the bearing cartridge assembly. 
           [0016]      FIG. 9  is an enlarged axial end view of a bearing constructed in accordance with the invention and in its environment in the bearing cartridge assembly; 
           [0017]      FIG. 10  is a radial view of the bearing of  FIG. 9 ; 
           [0018]      FIG. 11  is a side view of the bearing of  FIG. 9 ; 
           [0019]      FIG. 12  is an enlarged axial end view of a modified bearing constructed in accordance with the invention and in its environment in the bearing cartridge assembly; 
           [0020]      FIG. 13  is a radial view of the bearing of  FIG. 9 ; 
           [0021]      FIG. 14  is a side view of the bearing of  FIG. 9 ; 
           [0022]      FIG. 15  is an enlarged axial end view of another bearing constructed for use with the invention and in its environment in the bearing cartridge assembly; 
           [0023]      FIG. 16  is a radial view of the bearing of  FIG. 9 ; and 
           [0024]      FIG. 17  is a side view of the bearing of  FIG. 9 . 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0025]    Referring now to the figures, and in particular to  FIG. 1 , there is shown a bearing system  10  for use in a roller conveyor for a hot air dryer. Such dryers are used for removing moisture from slurries or wet layers of solids such as that formulated in the production of drywall, ceiling tile, and like board products. Typically, the dryer has several layers or decks of roller conveyors. At each deck, a plurality of parallel rollers are serially arranged side-by-side in a horizontal plane with their axes parallel to one another and collectively forming a conveyor. Rollers  11  are all driven in a common rotational direction and mutually support and convey a moisture laden layer of material in the dryer. Hot air is forced through the dryer over the mat or layer of material being conveyed to absorb moisture. Typically, a burner utilizing natural gas, coal or other fuel, known in the art, heats the air and a blower forces it through the dryer. As is common, the rollers  11 , which are typically all of the same construction, are carried on associated round steel shafts  12 . Sprockets, not shown, on one end of each of the shafts  12  are driven in the conveying direction by an endless chain. 
         [0026]    The bearing system for the conveyor rollers  11  of a single deck or level comprises a cartridge assembly  13  mounted on a horizontally extending frame member  14 , sometimes called a cage angle in the industry. It will be understood that a cartridge assembly  13  is provided at each side of a conveyor deck or level, that is, at each of the ends of the rollers  11 . The bearing cartridge assembly  13  comprises an elongated base unit or rail  16  and a complementarily shaped retainer  17 . In the illustrated example, the unitary base  16  and unitary retainer  17  are made to accommodate a plurality of eleven (11) bearings, but it will be evident that a cartridge assembly  13  can be made to accommodate other numbers of bearings as needed or desired. The base unit  16  and retainer  16  can be fabricated from 12 gauge steel sheet, for example.  FIGS. 2 and 5 , respectively, illustrate planar sheet metal preforms or blanks of the base unit  16  and retainer  17 . 
         [0027]    The base unit blank, designated  21 , shown in  FIG. 2 , has ovoid holes  22  punched out at each of the ultimate bearing centers. At the minor axis of the holes  22 , opposed tabs  23  are left in the sheet metal stock. After the holes  22  are formed in the blank, the blank is folded into an elongated narrow U-shaped channel with a bight or web  24  aligned with the tabs  23  and with opposed sides or legs  26  depending from the web  24 . After the blank  21  is formed into a channel  27  round, preferably semi-cylindrical steel shells  28  are inserted into the holes  22  and permanently fixed in place such as by welding to the edges of the holes at  29 . An end view of the base unit  16  in  FIG. 8A  reveals that the shells  28  are longer in the direction of their axes than the outside width of the base channel  27 . The shells  28  are fixed to the channel  27  such that they project laterally of the channel further at one side (to the left in  FIG. 8A ) than the other side. The shells  28  are concave with reference to the upper face of the base unit  16  so that they form carriers or seats for bearings  31  that rotationally support the shafts  12  of the conveyor rollers  11 . 
         [0028]    In conventional style dryer construction and, in particular, when existing dryers are retrofitted with the bearing cartridge assemblies  13 , the inside dimension of the base channel  27  is sized to slip over a vertical leg  32  of a cage angle  14 . This leg thickness may be ⅜″ or a similar dimension, or an equivalent metric dimension. The legs of the base unit channel  27  are drilled, punched, or otherwise formed with a limited number of aligned pairs of holes  33 , for example, a pair adjacent each end and a pair at mid-length of the base unit  16 , located to line-up with holes existing in the respective cage angle  14 . A like number of bolts  34  assembled through these holes fix the base unit  16  and ultimately the entire cartridge assembly  13  in place. At each end, the base unit channel  27  has a vertical pin welded or otherwise permanently attached to it so that it extends upright to register with the bearing retainer  17  as explained below. 
         [0029]    A retainer blank  41  shown in plan view in  FIG. 5  is an elongated flat strip of steel punched with pairs of aligned slots  42  on its opposite longitudinal edges  43 . The slots or notches  42  have round inner ends and are sized to fit over the roller shafts  12  with a small clearance. The retainer blank or sheet  41  is folded into a U-shape as shown in  FIG. 7  with an inside width sized to slip over the channel  27  of the base unit  16 . Holes  44  are formed in the ends of a web or bight  46  of the retainer  17  to receive the pins  36  on the base unit  16  and thereby be indexed to the base unit. Tabs  47  at each end of the retainer  17  are extensions of the web  46  and are bent down and dimensioned to abut the web  24  of the base unit channel  27  to properly vertically locate the retainer  17  above the base unit  16 . The retainer  17  serves as a cover or close fitting hood to protect the bearings  31  from dirt, dust and other debris. Still further, the bearing retainer  17  restrains the bearing segments  31  radially by limiting radial displacement of the roller shafts  12  which, in turn, prevent the bearing segments from lifting radially out of the carrier shells  28 . 
         [0030]      FIGS. 9-11  illustrate one form of a preferred bearing  31 , a plurality of which are assembled in the cartridge assembly  13 . The bearing  31  has a profile when viewed axially with reference to the axis of rotation of a roller  11 , which is an arcuate segment of a hollow generally circular cylinder subtending an arc of nominally about 120 degrees. The bearing  31  has an internal cylindrical bearing surface  51  and an outer surface  52  that is also cylindrical and concentric with the bearing surface. The radius of the bearing surface  51  is nominally the same size as that of the roller shaft. Typically, the roller shaft will be 1¼″ or metric equivalent in diameter, but may be somewhat smaller or larger as required. The length of the bearing  31 , measured in the direction parallel to the axis of the surface  51  is typically about 1 7/16″ or metric equivalent, but can be somewhat smaller or larger as desired. 
         [0031]    At the ends of the arcuate span of the bearing  31  are generally radial faces  53 . Adjacent the inner bearing surface  51 , these faces are preferably truly or nearly radial so that they are inclined from the horizontal at an angle of about 30 degrees. This inclination of these areas  54  serves to shed dust and other debris that may be generated during operation of the dryer and rotation of the rollers  11  so as to carry such dirt and debris away from the interface of the bearing surface  51  and surface of the roller shaft  12  under the influence of gravity and any vibratory forces, as well as a wiping action on the leading side of the rotating roller shaft. Because the bearing  31  subtends an arc substantially less than 180 degrees, the roller shaft  12  overlies the exposed arcuate ends of the interface of its surface and the bearing surface  51  thereby tending to shield this area from falling dirt and debris. 
         [0032]    The radial faces  53  are, additionally, characterized by the presence of axial slots or grooves  56 , outward of the radial areas  54 . The grooves  56  are shaped with planar surfaces  57 ,  58  that in the views of  FIGS. 8 and 9  lie in respective planes that are chordal or tangential to imaginary cylinders concentric with the bearing surfaces  51 ,  52 . The surfaces  58  lie in planes substantially perpendicular to an imaginary plane intersecting the radial faces  53 . The tabs  23  associated with the holes  22  in the base unit  16  are bent down out of the plane of the bight  24  so that they are received in the grooves  56 . Vertical surfaces  61  of the tabs  23  are arranged to abut vertical surfaces  58  of the grooves  56  and effectively restrain the bearing  31  from any cocking or skewing in the pocket of the shell  28  in which it is received. Such skewing of the bearing where its axis is misaligned with the axis of the roller shaft  12 , can lead to excessive and/or unpredictable wear of the bearing. The bearing material is preferably a substance that exhibits low friction, abrasion resistance and durability when exposed to the temperatures existing in the dryer. Carbon and polytetrafluoroethylene are examples of suitable materials. 
         [0033]    From the foregoing disclosure, it will be understood that the cartridge assembly  13  is capable of receiving and holding a plurality of bearings  31  in a horizontal array. The plurality of bearings  31  are held in position against axial movement by the opposed legs, designated  45 , of the inverted channel-shaped retainer  17 . More specifically, the inside surfaces of the legs  45  are arranged to axially constrain the bearings  31  by abutting end faces  59  of the bearings  31  which lie in planes transverse to the axes of the bearings. The slots  42  in the retainer legs  45  are proportioned to clear their respective roller shafts  12 . As earlier suggested, the cartridge assembly can be installed in a dryer of generally conventional construction, having what is known as cage angles or like frame elements  14  by simply bolting it in using the holes  33  and bolts  34 . Such an arrangement where all of the bearing supports, represented by the shells  28  are installed with a few bolts is a great savings in manufacturing costs, manufacturing labor, and assembly labor, over traditional arrangements where these bearing mounts have been individually mounted on a cage angle or its equivalent. 
         [0034]    The bearing retainer  17  is held in place on the pins  36  by hitch pins  71  ( FIG. 1 ) assembled through cross holes  72  drilled through the pins just above the upper surface of the retainer web  46 . The retainer  17  can be quickly and easily removed from the base unit  16  by removing the hitch pins  71  and lifting the retainer off the base unit pins  36  thereby exposing all of the bearings  31  for inspection and releasing the same for removal and replacement. With the retainer  17  lifted from the base unit  16 , the bearings  31  are unrestricted axially but for the weight imposed by a roller  11  through the roller shaft  12 . Consequently, a spent bearing  31  can be displaced by simply lifting its associated roller shaft  12  slightly to release its load from the spent bearing and pushing a fresh bearing against it in the axial direction so that the fresh bearing ejects the spent bearing from the receiving pocket formed by the associated shell  28  and is automatically replaced by this new bearing when the latter is fully received in the shell. It will be noted that in the fully received position, the new or fresh bearing  31  is substantially flush with both ends of a respective shell  28 . 
         [0035]      FIGS. 12-14  illustrate a second form of a bearing  131  that has an increased arcuate length. The arcuate length is advantageously slightly less than 180 degrees enabling two pieces to be cut from a cylindrical blank. The bearing  131  fits comfortably into a bearing carrier shell  28  with a nominal 180 degree expanse with a clearance shown at opposite sides  81 . The bearing  131  can have the ID and OD and length of the bearing  31 , for example. Tabs  123  are received in grooves  156  and serve the same purposes as that described in connection with the tabs  23  and grooves  56  described above in connection with the bearing  31 . In simple terms, the tabs  131  work like keys to ensure that the bearing remains in proper orientation and therefore provides a full service life. 
         [0036]      FIGS. 15-17  illustrate still a further form of a bearing  160  useful in practicing the invention. The bearing  160  at a bearing surface  161  surrounds nearly 180 degrees of a roller shaft  12 . The bearing  160  has ID, OD and length dimensions corresponding to the bearing  31 . Diametrically opposite faces  162  of the bearing have coplanar flat areas  163  lying in a plane adjacent an imaginary plane aligned with the axis of the bearing surface  161  and downwardly sloping areas  164  at outlying zones of the faces  162 . When the bearing  160  is employed, tabs  223  corresponding to the tabs  23  of the embodiment of  FIGS. 1-11 , are coplanar with the web  24  of the base channel  27 . 
         [0037]    While the invention has been shown and described with respect to particular embodiments thereof, this is for the purpose of illustration rather than limitation, and other variations and modifications of the specific embodiments herein shown and described will be apparent to those skilled in the art all within the intended spirit and scope of the invention. For example, the multiple bearing cartridge of the invention can be used in dryers, often used for example in veneer manufacture, where roller shaft bearings are suspended or hung from above. In such cases, the disclosed multiple bearing cartridge can be employed with suitable mounting adapters. Accordingly, the patent is not to be limited in scope and effect to the specific embodiments herein shown and described nor in any other way that is inconsistent with the extent to which the progress in the art has been advanced by the invention.