Patent Publication Number: US-6702091-B2

Title: Conveyor roller assembly

Description:
RELATED APPLICATION 
     This application is a continuation-in-part of application Ser. No. 09/740,173, filed Dec. 18, 2000 now U.S. Pat. No. 6,454,077 which is a continuation-in-part of application Ser. No. 09/557,525, filed Apr. 24, 2000, U.S. Pat. No. 6,161,673, which is a continuation-in-part of application Ser. No. 09/153,443, filed Sep. 15, 1998, Pat. No. 6,053,298. 
    
    
     BACKGROUND OF THE INVENTION 
     In the art of endless belt or roller conveyors, it is common to use a series of roller assemblies each of which includes an elongated metal roller tube supported on opposite ends by a pair of anti-friction ball bearings. The bearings are mounted by bushings on an elongated hexagonal axle which extends axially through the roller tube and has opposite end portions projecting from the tube. The axle is spring biased to a center position to permit axial movement of the axle relative to the roller tube for installing the roller assembly between horizontally spaced frame members or channels of a roller or belt conveyor having hexagonal holes within the channels to receive the end portions of the axle. One example of such a roller assembly is produced by Applicants&#39; assignee and shown on its Product Bulletin #102. Another example of such a roller assembly is manufactured by Ralphs-Pugh Co. and shown on a 1999 catalogue page 112. The axle or shaft extending through the roller tube may also be provided with a retractable stub axle or plunger for installing the conveyor roller between frame members, for example, as disclosed in U.S. Pat. No. 3,610,387. Other forms of roller assemblies having bearing shafts supporting retractable stub axles to facilitate installation and removal of the roller assemblies, are disclosed in U.S. Pat. No. 3,713,521 and No. 5,421,442. 
     With any such conveyor roller assembly, it is desirable to minimize the construction and maintenance costs of the assembly and to eliminate wear of the holes within the supporting frame members or channels. It is also desirable to provide for extending the service life of the roller assembly and for easily and quickly installing and replacing the roller assembly. In addition, it is desirable to minimize the noise level of operation of the roller assembly and to minimize the weight of the roller assembly for reducing shipping costs and simplifying roller replacement. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to an improved conveyor roller assembly which is adapted for use between horizontally spaced frame members or channels of a conveyor and which provides all of the desirable features and advantages mentioned above. The roller assembly of the invention may be used for directly supporting articles to be conveyed or for supporting an endless conveyor belt which carries and transports the articles. 
     In accordance with one embodiment of the invention, a conveyor roller assembly includes an elongated roller cylinder or tube which may be formed of metal or extruded of an electrically conductive rigid plastics material. Each end portion of the tube receives a bearing assembly or unit which includes a tubular shaft having an outer end portion which collapses slightly to receive the inner race of an anti-friction ball bearing having an outer race confined within the end portion of the roller tube by an annular adapter or bushing. The shaft has a hexagonal bore which receives an axially moveable hexagonal stub axle and encloses a compression spring which urges the stub axle to an outer projecting position. The outer collapsible end portion of the shaft also receives in snap-fit relation an annular dust cover which protects the shaft and retains the inner race of the bearing on the shaft. 
     The stub axle has an inner end portion with spring tabs having cam surfaces which engage a shoulder within the shaft but permit the stub axle to be pulled outwardly from the shaft for replacement of the axle while the coil spring is retained within the shaft by the shoulder. The hexagonal stub axle has a tapered and twisted outer tip portion which extends from a slightly tapered and resilient portion to provide self-alignment and a close fit of the hexagonal stub shaft with the hexagonal hole in the adjacent frame channel. The tubular shaft, stub axle, dust cover and adaptor bushing are all molded of a glass fiber reinforced plastics material which also contains carbon to provide electrical conductivity and dissipation of any static electrical charge. 
     In accordance with another embodiment of the invention, the stub shaft is constructed of a slightly resilient plastics material and has an internal metal reinforcing pin, and the stub shaft is biased to its extended position by a coil spring or other spring element supported by the tubular bearing shaft which is molded integrally with the bearing dust cover. In a further embodiment, the resilient stub shafts are reinforced by opposite end portions of a cylindrical metal pin or rod which connects the stub shafts. 
     Other features and advantages of the invention will be apparent from the following description, the accompanying drawings and the appended claims. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an elevational view of a conveyor roller assembly constructed in accordance with the invention and shown installed between horizontally spaced frame members or channels; 
     FIG. 2 is a fragmentary axial section of the opposite end portions of the roller assembly shown in FIG.  1  and showing bearing assembly units constructed in accordance with the invention; 
     FIG. 3 is an exploded perspective view of one end portion of the roller assembly shown in FIGS. 1 &amp; 2; 
     FIG. 4 is an axial section of a modified bearing assembly unit constructed in accordance with the invention; 
     FIG. 5 is an axial section similar to FIG.  2  and showing another embodiment of the invention; 
     FIG. 6 is an axial section similar to FIG.  2  and showing another embodiment of the invention; and 
     FIG. 7 is a radial section taken generally on the line  7 — 7  of FIG.  6 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     A conveyor roller assembly  10  constructed in accordance with the invention is adapted for use on a conveyor system which includes horizontally spaced elongated frame members or channels  12  having longitudinally spaced pairs of laterally aligned hexagonal holes  14  each having a dimension across the flats of 0.4375 inch. The roller assembly  10  includes a cylindrical roller tube  16  which is commonly cut from welded steel tubing, but may also be formed from an extruded tube of rigid plastics material. The extruded tube may have inwardly projecting and longitudinally extending reinforcing ribs or concentric walls connected by such ribs to provide maximum strength with minimum wall thickness and weight and also to provide for corrosion resistance. 
     Each of the opposite end portions of the conveyor roller tube  16  is rotatably supported by a corresponding bearing assembly unit  20  which preferably includes an anti-friction ball bearing  22  having an outer race confined within an annular adaptor bushing  24  molded of a rigid plastics material such as polypropylene and reinforced with glass fibers. The bushing  24  has an outer cylindrical surface  27  which slides into the end portion of the tube  16 , and the bushing is retained within the tube by crimping the surrounding end portion  28  of the tube radially inwardly into a slight recess within the bushing around the periphery of the bushing  24 . The rigid plastics material forming the bushing  24  also includes sufficient carbon particles so the bushing is electrically conductive to dissipate any electrostatic charge on the tube  16  into the bearing  22 . 
     A tubular shaft member  35  has an outer end portion with spring fingers  36  formed between axially extending and circumferentially spaced slots  38 , and each finger  36  has an arcuate outer tip portion  41  with a tapered cam surface  42 . The outer end portion of the tubular shaft  35  is slightly collapsible so that the end portion may be pressed into the inner cylindrical race of the bearing  22  during assembly of the bearing onto the shaft  35 . The shaft member  35  is also injection molded of the same rigid plastics material as the bushing  24  and includes reinforcing glass fibers and carbon particles for conducting any electrostatic charge transferred through the bearing  22 . An annular dust cover  45  is also mounted on the outer portion of the shaft  35  and has an inner bore with a diameter the same as the bore of the inner race of the bearing  22 . Thus after the bearing  22  is mounted on the outer shaft portion, the dust cover  45  is mounted on the shaft portion by collapsing the spring fingers  36  in response to camming the tip portions  41  inwardly when the dust cover  45  is forced axially onto the cam surfaces  42 . 
     The shaft member  35  defines an internal hexagonal chamber  52  and a slightly smaller hexagonal bore  54  within the collapsible outer portion of the shaft member. The bores  52  and  54  cooperate to define a tapered internal hexagonal shoulder  56 . A hexagonal stub shaft or axle  60  is also molded of the same plastics material as the bushing  24 , shaft member  35  and dust cover  45 , and the material has glass reinforcing fibers and carbon for electrical conductivity. The stub axle  60  has a twisted and tapered outer tip portion  62  with a hexagonal outer end surface  63  oriented about 30° with respect to the larger hexagonal portion of the stub axle  60  which has a dimension across the flats slightly less than the dimension of the hole  14  in the frame channels  12 . The hexagonal end surface  63  of the tip portion  62  has a dimension across the flats of about 0.375 inch. 
     The stub axle  60  has an inner end portion formed by six inwardly projecting tabs  66  (FIG. 3) each having an outwardly projecting V-shaped cam surface  67 . The spring fingers or tabs  66  are cammed inwardly or collapsed slightly when the stub axle  60  is pressed axially into the hexagonal bore of the shaft member  35  to the position shown in FIG.  2 . When the stub axle  60  is pulled axially outwardly from the hexagonal bore  54 , the spring tabs  66  are cammed inwardly by the hexagonal tapered shoulder  56 . Thus when the outer surface of a stub axle  60  is worn and it is desired to replace the stub axle, the roller assembly  10  is removed from the frame channels  12 . The old stub axle may then be quickly pulled from the shaft member  35 , after which a new stub axle  60  is inserted into the shaft member  35 . 
     Each stub axle  60  is normally retained in its outwardly projecting or extended position, as shown in FIG. 2, by a compression coil spring  68  retained within the chamber  52  of the shaft member  35  by a spring retaining ring  69  pressed into a counterbore  71  within the inner end portion of the shaft member. The diameter of the spring  68  is sufficiently large so that the spring is confined within the chamber  52  against the shoulder  56  when the stub axle  60  is pulled axially from the shaft member  35  for replacement. The length of the chamber  52  is sufficiently long to permit the stub axle  60  to be depressed inwardly against the bias of the spring  68  until the end surface  63  of the tip portion  62  is flush with the outer end surface of the shaft member  35 . 
     When it is desired to install a relatively short roller assembly  10  between the frame channels  12 , the stub axles  60  projecting from opposite ends of the roller assembly are depressed axially inwardly against the springs  68  until the outer end surfaces  63  of the stub axles  60  are substantially flush with the outer end surfaces of the corresponding shaft members  35 . The roller assembly  10  is then shifted downwardly until the tip portions  62  of the stub axles  60  enter the corresponding hexagonal holes  14 . If either or both of the stub axles  60  is not rotationally aligned with the corresponding holes  14 , the twisted and tapered tip portions  62  of the stub axles rotate the stub axles and shafts  35  until the stub axles are precisely aligned and are forced outwardly by the springs to their fully projecting positions (FIG. 2) within the mating openings  14 . The stub axles  60 , shaft members  35  and dust covers  45  are then prevented from rotating so that the bearings  22  support the tube  16  for free rotation. The tapered and twisted tip portion  62  of each stub axle  60  also permits one stub axle of a relatively long roller assembly  10  to be inserted into its corresponding hole  14  while the roller assembly is in a tilted position relative to the frame channels so that it is only necessary to depress one of the stub axles  60  inwardly to its retracted position in order to install a longer roller assembly  10  to its operating position as shown in FIG.  1 . 
     Referring to FIG. 4 which shows a modified bearing assembly unit  20 ′ constructed in accordance with the invention, the components which are the same as the components in the embodiment described above in connection with FIGS. 1-3 have the same reference numbers. The modified components have the same reference number with a prime mark, and additional components have additional reference numbers. Accordingly, the stub axle  60 ′ is constructed similar to the stub axle  60 , but is molded of a slightly resilient plastics material such as polyurethane and also includes a slightly tapered hexagonal portion  61 ′ which is slightly resilient. For example, the slightly larger end of the tapered portion  61 ′ and the base portion of the stub axle  60 ′ may have a width across the flats which is 0.001″ less than the width across the flats at the hexagonal hole  14  within the frame member or channel  12 . For example, if the width across the flats of the hex hole  14  is 0.678″, which is common, the large end of the slightly tapered portion  61 ′ and the base portion of the stub axle  60 ′ would have a width across the flats of 0.677″. 
     The modification shown in FIG. 4 also includes an annular dust cover  45 ′ with a projecting cylindrical ring portion  46 ′ which surrounds the shaft segments or tips  41  of the tubular shaft  35 . The projecting ring portion  46 ′ protects the shaft end segments  41  and prevents them from being accidentally forced inwardly when the stub axle  60 ′ is depressed inwardly, for example, if the bearing assembly unit  20 ′ was dropped with the stub axle  60 ′ hitting the floor. As also shown in FIG. 4, the compression spring  68  is retained within the chamber  62  by a cylindrical cap member  76  which is press fitted on the tubular shaft member  35 . The cap  76  may also be retained by a suitable cement or adhesive which is compatible with the fiber reinforced plastics material. 
     FIG. 5 shows another embodiment of the invention and including components which are the same as the embodiments of FIGS. 1-4 and have the same reference numbers. The revised components have additional reference numbers. The same components include the conveyor tube  16 , bushing  24  and anti-friction or ball bearing  22 . In this embodiment, the tubular shaft  85  extends through the inner race of the bearing  22  and is molded integrally with the annular dust cover  87 . The tubular shaft  85  supports a stub axle  90  having a hexagonal outer surface and molded of a slightly resilient plastics material such as polyurethane. The stub axle  90  also has a tapered and twisted tip portion  92  having the same configuration as the tip portion  62 ′ described above in connection with FIG.  4 . The stub axle  90  surrounds an axially extending metal reinforcing core or pin  96  which has an enlarged head portion  97  adjacent the inner end of the stub axle  90 . 
     The stub axle  90  is biased to its extended position (FIG. 5) by a spring element illustrated in the form of a compression coil spring  100  which is supported by a strap like metal strip or bracket  102  having a narrow width, for example, ⅛″. The bracket  102  has an inner end portion  104  which projects into the inner end portion of the coil spring  100 . The bracket  102  has opposite parallel leg portions  106  which confine the coil spring  100  and have outer end portions projecting through corresponding narrow slots within the tubular shaft  85 . The leg portions  106  of the bracket  102  have outer end tabs  108  which project radially outwardly from opposite flat surfaces of the stub shaft  90  and engage the outer end surface of the tubular shaft  85 . The outer end portion of the spring  100  is tapered and is confined within the annular head portion  91  of the stub axle  90  around the head portion  97  of the metal reinforcing pin  96 . As apparent from FIG. 5, the stub axle  90  may be depressed inwardly against the bias of the spring  100  until the outer end surface of the tip portion  92  is flush with the tabs  108  of the spring retaining bracket  102 . 
     Referring to FIG. 6, a roller assembly  120  is constructed in accordance with another embodiment of the invention and includes the metal roller tube  16  having opposite end portions supported by bearing units  121  including corresponding anti-friction bearings  22  retained by the molded plastic adapters  24 . The inner race of each bearing  22  is pressed onto a tubular shaft member  122  having a hexagonal center opening or bore  124  and an integrally molded and outwardly projecting dust cover  126 . Each of the tubular shaft members  122  supports an axially slidable stub axle  130  molded of a urethane material as described above for the stub axle  90 . Each stub axle  130  has a hexagonal outer surface  132  slidable within the bore  124  of the corresponding tubular shaft member  122 . As mentioned above, preferably each molded stub axle  130  has a width of about {fraction (7/16)}″ across the flats of the outer hexagonal surface  132 . The stub axle  130  includes a solid tapered and twisted outer tip portion  134  with a hexagonal cross-sectional configuration in the same manner as the tip portion  62 ′ described above in connection with FIG.  4 . 
     The stub axles  130  at opposite ends of the roller assembly  120  are reinforced by opposite end portions of an elongated cylindrical metal pin or rod  138  which extends the full length of the tube  16  and projects into center bores  139  within the stub axle  130  so that the stub axles  130  are free to rotate on the rod  138 . Preferably, the rod  138  has a diameter of about ¼″ or about one half of the maximum width of the stub axles  130  across the ridges of the hexagonal outer surface  132 , as shown in FIG.  7 . As also shown in FIG. 6, each of the stub axles  130  is molded with a cylindrical inner end portion  142  having an outwardly projecting flange  144 . A tapered wire compression coil spring  146  has its inner end portion seated on the axle portion  142  against the flange  144  and a larger diameter outer end portion engaging the inner race of the bearing  22 . Thus the compression springs  146  cooperate to center the connecting rod  138  and position the stub axles  130  symmetrically or uniformly within their corresponding shaft members  122 . 
     When it is desired to install a roller assembly  120  between a pair of frame members, such as the frame members  12  shown in FIG. 1, one of the stub axles  130  is depressed to its retracted position, causing the opposite stub axle  130  to project further outwardly so that it may be easily inserted within a hexagonal frame opening or hole  14  with the tip portion  134  guiding the hexagonal stub axle  130  into the hexagonal frame hole. The roller assembly  120  is then tilted to a horizontal position where the depressed stub axle  130  is released and allowed to shift or pop outwardly into the hexagonal hole  14  within the opposite frame member  12 . Thus the opposite end portions of the connecting pin or rod  138  project into the holes  14  and assure that the roller assembly  120  is effectively locked to the frame members  12 . 
     From the drawings in the above description, it is apparent that a conveyor roller assembly constructed in accordance with the present invention, provides desirable features and advantages. For example, the roller assemblies  10  and  120  provide for a reduced construction cost since all or most of the plastic components of the bearing units  20  or  20 ′ or  120  may be injection molded in a family mold, and the components of each bearing unit may be quickly and easily assembled before the unit is inserted into the end portion of the tube  16 . The resilient surface of the stub axle  60 ′ or of the stub axle  90  or  130  not only eliminates wear of the hexagonal hole  14  within the corresponding frame channel  12  but also substantially eliminates wear of the stub axle by absorbing the vibrational energy. In addition, the slightly tapered hexagonal portion  61 ′ of the stub axle  60 ′ or the tapered tip portion of the stub axles  90  or  130  helps minimize the clearance between the stub axle and the hexagonal hole  14  to aid in eliminating wear. 
     While wear of the stub axles  60  or  60 ′ or  90  or  130  is substantially eliminated, the stub axle  60  or  60 ′ may be conveniently replaced simply by removing the roller assembly  10  and pulling the stub axle axially from the corresponding shaft member  35  and then replacing it with a new stub axle. As a result, down time of the conveyor is minimized. It has also been found that the resilient plastic stub axle  60  or  60 ′ or  90  or  130  significantly reduced the noise level created by any movement of the stub axles within the holes in the frame channels  12 . The above construction of each bearing unit also eliminates any side or axial loading on the bearing  22  which results in extending the service life of the bearing. 
     The plastic components of the bearing units also provide for high corrosion resistance and for dissipation of any static electricity on the roller tube  16 . Also, if a bearing  22  does freeze or seize up, the bearing will turn on the plastic shaft member  35  or  85  or  122  so that there is no damage to the stub axle or the frame channel  12 . The substantially lower weight of the bearing units  20  or  20 ′ or  84  also significantly reduces the overall weight of the roller assembly  10 . In the embodiment of FIG. 6, the relatively small diameter of the connecting reinforcing pin or rod  138  also minimizes the weight of the roller assembly  120  as well as the cost of the assembly. As a result, the shipping weight and shipment cost are lower, and roller replacement is less fatiguing, especially with the longer roller assemblies. In addition, since each stub axle  130  is free to rotate on the connecting cylindrical rod  138 , the stub axles  130  are self-aligning and accommodate hexagonal frame holes  14  which are not in precise rotational alignment. 
     While the forms of conveyor roller assembly herein described constitute preferred embodiments of the invention, it is to be understood that the invention is not limited to these precise forms of assembly, and that changes may be made therein without departing from the scope and spirit of the invention as defined in the appended claims. For example, the molded stub axle  60  or  60 ′ may have a metal or rigid core pin and a resilient outer surface such as the stub axles  90  and  130 . As another example, the spring  68  (FIG. 2) may have a tapered outer end portion which projects into the cavity surrounded by the tabs  66  of the stub axle  60  or  60 ′. The metal strip spring retaining bracket  102  may be replaced by a specially formed spring wire or spring strip which would eliminate the coil compression spring  100 . The bracket  102  and spring  100  may also be replaced by a radially extending wire coil spring positioned adjacent the head portion  91  of the stub axle  90  and have opposite end portions extending through the shaft  85  in place of the legs  106  of the bracket  102 .