Abstract:
Multi-piece rollers for a conveyor belt. First and second roller sections fit together to form a complete roller. The two roller sections together define a bore for receiving an axle. The bore and the periphery of the roller are formed in part by each of the first and second roller sections. The roller is assembled by sliding the two sections together in a direction perpendicular to the axle with the bore closing around the axle. The roller sections have fingers that interdigitate with each other to prevent axial separation of the first and second roller sections. The interdigitated fingers surround a majority of the bore.

Description:
BACKGROUND 
     The invention relates generally to power-driven conveyors and more particularly to multi-piece article-supporting rollers for conveyor belts. 
     Article-supporting rollers are used in modular plastic conveyor belts to provide low-friction rolling support to conveyed articles. In many roller-top belts, the rollers are mounted on steel axles in cavities formed in the belt modules used to construct the modular belt. Roller-top belt modules with steel axles are more difficult to manufacture than standard modules without rollers. One way to manufacture a roller-top module is to injection-mold the module around a roller on a steel axle. The ends of the axle extend into the mold and are encapsulated in the molded module body. Another way is to injection-mold a module body with a receptacle for a roller. Then, in a secondary manufacturing step, a roller and axle are placed in each receptacle, and a cover is welded or otherwise retained in place over the ends of the axle to hold the roller in the module. Thus, there is a need to simplify the manufacture of roller-top belts. 
     SUMMARY 
     A multi-piece roller embodying features of the invention and usable in a conveyor belt comprises first and second roller sections that fit together to form a complete roller. The complete roller has an outer periphery between opposite ends. Together, the first and second roller sections define a bore that extends along the central axis of the roller and opens onto the opposite ends for receiving an axle. The bore is formed in part by each of the first and second roller sections. At least one first interdigitating member on the first roller section and at least two second interdigitating members on the second roller section interdigitate with each other. The two sections are assembled by sliding the two sections together in a direction perpendicular to the central axis of the complete roller. The interdigitated first and second interdigitating members prevent axial separation of the first and second roller sections. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These aspects and features of the invention, as well as its advantages, are described in more detail in the following description, appended claims, and accompanying drawings, in which: 
         FIG. 1  is an isometric view of a portion of a modular plastic conveyor belt embodying features of the invention; 
         FIG. 2  is a top plan view of a portion of the conveyor belt of  FIG. 1 ; 
         FIG. 3  is an enlarged isometric view of the top surface of a module of a conveyor belt as in  FIG. 1 ; 
         FIG. 4  is an axonometric cross section of the module of  FIG. 3  taken along lines  4 - 4 ; 
         FIGS. 5A-5C  are oblique views of first and second roller pieces and a complete roller usable in a conveyor belt module as in  FIG. 3 ; 
         FIGS. 6A-6C  are axonometric views of a first roller piece, a second roller piece, and another complete roller usable in a conveyor belt module as in  FIG. 3 ; 
         FIGS. 7A and 7B  are axonometric views of a roller piece and another complete roller usable in a conveyor belt module as in  FIG. 3 ; and 
         FIG. 8  is an isometric view of a mold for a conveyor belt module as in  FIG. 3 ; 
         FIG. 9  is an isometric view from the top side of a portion of another version of conveyor belt module usable to make a conveyor belt as in  FIG. 1 ; and 
         FIG. 10  is an isometric view of a portion of the bottom side of the conveyor belt module of  FIG. 9 . 
     
    
    
     DETAILED DESCRIPTION 
     A portion of a conveyor belt embodying features of the invention is shown in  FIG. 1 . The portion of the modular conveyor belt  10  shown is an interior portion. Three conveyor belt modules  12  are connected together in three belt rows  14 . The modules are shown offset laterally from row to row in a bricklay pattern. Although only one module  12  is shown in each row  14 , other similar modules are connected side by side in each row to form an endless conveyor belt. Drive pockets  16  opening onto bottom sides  18  of the modules admit teeth  20 ,  21  of drive or idle sprockets  22 . The teeth  20 ,  21  of drive sprockets drive against leading drive surfaces  24  bounding the pockets. The teeth  20 ,  21  of idle sprockets are driven by trailing drive surfaces  25  bounding the pockets opposite the leading drive surfaces. The teeth are arranged in two groups around the periphery of each of the sprockets. Each group is laterally offset from the other across the width of the sprocket. The teeth  20  in a first group are staggered circumferentially from the teeth  21  in a second group, with the teeth in each group spaced at twice the pitch of the conveyor belt. In this way, the teeth are positioned to engage the drive pockets  16 , which are laterally offset from row to row. The teeth  20  in the first group engage all the even rows, and the teeth  21  in the second group engage all the odd rows. The endless belt is trained around idle and drive sprocket sets, which are mounted on shafts (not shown) received in bores  26  of the sprockets. The shaft of the drive sprockets is rotated by a motor and gear box (not shown) to drive the belt in a direction of travel  28 . 
     As shown in  FIG. 2 , each module  12  has an intermediate portion  30  that extends from a first end  32  to an opposite second end  33  defining the length of the module. The module extends in width from a first side edge  42  to an opposite second side edge  43 . The thickness of the module is measured from the bottom side  18  to an opposite top side  19 . Hinge elements of a first set  34  are spaced apart laterally along the first end  32 , and hinge elements of a second set  35  are spaced apart laterally along the second end  33 . First and second gaps  36 ,  37  between the hinge elements of the first and second sets  34 ,  35  are sized to allow the first set of hinge elements of one row to interleave with the second set of hinge elements of an adjacent row. Hinge pins  38  through aligned openings  39  in the interleaved hinge elements connect adjacent rows together at hinge joints  40  in the endless belt  10 . 
     Each belt module  12  has one or more cavities  44  that open onto the top side  19  of the module. In the version of module shown in  FIG. 2 , the cavities also open onto the bottom side  18  and are alternately positioned across the width of the intermediate portion with the drive pockets  16 , which are shown opening onto the top side  19 , too. A belt roller  46  is mounted in each cavity for rotation on an axis  47  parallel to the length of the intermediate portion. The rollers  46  on one row  14  are shown offset in the width direction from those in an adjacent row  14 ′ for more even article support. The lateral offset from row to row means that the drive pockets  16  are also laterally offset from row to row. The laterally offset and circumferentially staggered groups of teeth  20 ,  21  on the sprockets accommodate the offset roller arrangement. Salient portions of the rollers  46  extend above the top side  19  of the belt into a supporting position for conveyed articles. 
     First and second parallel ridges  48 ,  49  extend laterally across the width of the module along the first and second ends  32 ,  33 . The ridges increase the module&#39;s beam stiffness. The ridges shown are wavy, their height above the top side varying across the width of the module. The height of the ridges is at a maximum at the position of the roller cavities  44 . But the peak of the ridges is below the tops of the rollers. The height of the ridges decreases to a minimum midway between cavity positions in the module. In this way, the bottoms of conveyed articles are guaranteed to ride atop the rollers, and trip points on the ridges are minimized. 
     A portion of the belt module  12  without a roller is shown in  FIG. 3 . The roller cavity  44  in the intermediate portion  30  is bounded by a perimetric wall  50 . An axle  52  for the rollers extends diametrically across the cavity. The ends  54  of the axle terminate at opposite positions on the wall. As shown in cross section in  FIG. 4 , the axle  52  is formed unitarily with the intermediate portion  30  of the module  12 , its ends  54 ,  55  continuous with the wall  50  and the rest of the module. In this example, the axle&#39;s axis ( 47 ,  FIG. 2 ) is parallel to the length of the intermediate portion  30  so that the roller rotates transverse to the direction of travel. But the axle  52  could be formed in the cavity at other angles, such as with its axis of rotation parallel to the width of the direction of the intermediate portion to rotate in or opposite to the direction of travel. 
     Another version of a conveyor belt module that can be used to construct stiff roller-top belts is shown in  FIGS. 9 and 10  from the top and bottom sides. The conveyor belt module  110 , which is similar to the belt module  12  of  FIG. 3 , has on its top side  111  first and second ridges  112 ,  113  that are segmented across the width of the intermediate portion of the module into individual ridge segments  112 ′,  113 ′ whose maximum heights coincide with the positions of the rollers  46 . As seen from the bottom side  115  of the module in  FIG. 10 , the length dimension  116  of the drive pockets  16  is less than the length dimension  117  of the roller cavities  44 , which means that the beam portions  118  between the hinge elements and the cavities are thinner than the beam portions  119  between the hinge elements and the drive pockets  16 . The ridge segments  112 ′,  113 ′ on the top side of the thinner beam portions  118  add stiffness to those thinner portions. 
     One way of manufacturing the module is shown in  FIG. 8 . A molten thermoplastic polymer, such as polypropylene, polyethylene, acetyl, or a composite polymer, is injected into a cavity region  56  of a closed mold consisting of two mold halves  58 ,  59  (shown separated). (The axle and cavity portion  60  of one half of the mold is shown in  FIG. 8 .) Once the mold cavity is filled, heat and pressure are applied to the joined mold halves to mold the module. The mold halves are parted and the molded module ejected. In this way, the axle is molded unitarily with the intermediate portion of the module. 
     Because the axles  52  are unitarily molded with the modules and both ends  54 ,  55  of the axles are continuous with the walls  50 , the belt rollers  46  cannot be axially inserted onto the axles.  FIGS. 5A-5C  show one version of a multi-piece roller  46 . The roller consists of two different pieces: a first roller section  62  and a second roller section  63 . The two sections are inserted radially onto the axle and joined together like three-dimensional puzzle pieces. When joined, the two roller sections form the complete roller  46  with a central bore  64  along a central axis  66  of the roller. The first roller section  62  has a first interdigitating member  68  that interdigitates with a pair of second interdigitating members  69  on the second roller section  63  to form the complete roller  46 . The complete roller is assembled by sliding the two roller sections  62 ,  63  together in a radial direction  70  perpendicular to the central axis  66 . 
     Each of the interdigitating members  68 ,  69  has a lateral face  72  in contact with a lateral face  73  of an adjacent interdigitated member. In this example, the outward facing lateral faces  72 ,  72 ′ of the first roller section  62  contact the inward-facing lateral faces  73  of the second roller section  63 . The axially overlapped faces prevent axial separation of the two interdigitated roller sections. Each of the interdigitating members  68 ,  69  has a pair of fingers  74 ,  75  on opposite sides of the bore  64 . Each finger  74 ,  75  forms a portion  76 ,  77  of the outer periphery of the complete roller  46 . The fingers extend from a cap member  78  out to distal ends  80 ,  81 . Like the fingers, the cap members form a portion of the periphery of the complete roller. The interdigitated roller sections are retained together by locking means in the form of locking ears  82  formed on the lateral faces  73  of the second roller section  63  in cooperation with matching detents  84  formed in the lateral faces  72 ,  72 ′ of the first roller section  62 . The ears snap in place in the detents to lock the roller on the axle and prevent it from radially separating in operation. The first and second roller sections  62 ,  63  surround less than 360° of the bore and form a gap  86  opening into the bore that is wide enough to admit an axle radially into the bore. In this example, the interdigitating members surround about 180° of the bore. 
     Another version of a multi-piece belt roller is shown in  FIGS. 6A-6C . The complete roller  46 ′ is externally identical to the roller  46  of  FIG. 5C . The only difference is the locking means in which locking ears  82 ′ are formed on the cap members  78 ′ of the first and second roller sections  62 ′,  63 ′ and mating detents  84 ′ are formed in the fingers  74 ′,  75 ′. 
     Yet another version of a multi-piece roller that is usable in a conveyor belt as in  FIG. 1  is shown in  FIGS. 7A and 7B . In this version, the complete roller  90  consists of two identical roller sections  92 . Each roller section in this example has three interdigitating members: two internal members  94  and an end member  95 . The interdigitating members are identical except that the end member  95  has a rounded outer face  96  that forms an end of the complete roller  90 . Like the rollers of  FIGS. 5 and 6 , the roller  90  has a cap portion  98  that forms a portion of the outer periphery of the roller across its entire axial length. The interdigitating members  94 ,  95  extend from a flat base  100  of the cap member  98  to flat distal ends  102 . When the complete roller is assembled as in  FIG. 7B , the distal ends of the interdigitating members rest on the flat base of the cap member of the other roller section. Because the cap members are opposite each other, they help prevent impulse or shock loads from separating the roller sections. The interdigitating members  94 ,  95  of each roller section  92  in this roller surround more than 180° of the bore  64 . Unlike the rollers of  FIGS. 5 and 6 , the roller  90  has gaps  104  leading into the bore  64  that, at their narrowest, are narrower than the bore&#39;s diameter  106 . The restricted opening into the bore portion  108  allows each roller section to snap onto an axle whose diameter is slightly greater than the width of the gaps  104 . 
     Other locking means for locking the two roller sections together include adhesive-bonding, sonic welding, and other conventional mechanical and chemical fastening techniques. Furthermore, each of the roller sections could be molded out of more than one material to provide desirable operating characteristics and a variety of outer periphery textures.