Abstract:
A separation conveyor using a roller belt whose rollers are already rotating before receiving an article to provide immediate pull-away from an infeed conveyor. The rollers of a roller belt extend through the thickness of the belt and into contact with a bearing surface in a reversing segment of a belt path between the returnway and the carryway of the separation conveyor. The rollers are already rotating on the bearing surface in the reversing segment at the infeed end before they contact articles to avoid delays in pulling articles away from the infeed conveyor and onto the separation conveyor.

Description:
BACKGROUND 
       [0001]    The invention relates generally to power-driven conveyors and, more particularly, to conveyors with roller belts having rotatable article-supporting rollers that roll on a bearing surface at the infeed end of the conveyor as the belt advances. 
         [0002]    Roller belts are used in material-handling conveyors to increase the separation of conveyed articles by accelerating the articles along the conveying surface at a speed greater than the speed of the belt itself. Roller belts are typically characterized by a plurality of freely rotatable embedded rollers whose diameters exceed the thickness of the belt. In this way, salient portions of the rollers extend past the top and bottom surfaces of the belt, as shown in  FIG. 7 . The rollers  10  of the belt  12  ride on a bearing surface  14  under the carryway portion of the belt&#39;s path. As the belt advances in a direction of belt travel  16 , the rollers are rotated in the direction of arrows  18  by their contact with the stationary bearing surface. The rotation of the rollers propels articles atop the rollers in the direction of belt travel, but at a higher speed—typically twice the belt speed if the rollers do not slip on the bearing surface. Because of the conventional positioning of idle sprockets  20  at the infeed end of the roller-belt conveyor, the bearing surface, to avoid interference, extends upstream to a position  22  downstream of the sprockets, which engage the belt between rollers. Until the rollers making their way around the sprockets reach the bearing surface, they do not rotate. Because the rollers  10 ′ immediately at the infeed end of the roller-belt conveyor are not rotating, there is a delay before articles transferred onto the conveyor are accelerated on the belt and separated from trailing articles. 
       SUMMARY 
       [0003]    This shortcoming is overcome by a conveyor embodying features of the invention. In one aspect, the conveyor comprises a roller belt having a plurality of rollers extending through the thickness of the roller belt. The roller belt advances along a conveying path that includes: (a) an upper carryway segment along which articles are conveyed in a conveying direction; (b) a lower returnway segment below the carryway segment along which the roller belt advances in a direction opposite to the conveying direction; (c) a first reversing segment along which the roller belt transitions upward from the returnway segment to the carryway segment; and (d) a second reversing segment along which the roller belt transitions downward from the carryway segment to the returnway segment. A stationary bearing surface underlies the roller belt in the first reversing segment and provides a surface on which the rollers roll in the first reversing segment as the roller belt advances. 
         [0004]    In another aspect, a conveyor comprises a reversing wheel defining an exit end of the conveyor and a stationary convex bearing surface defining an infeed end of the conveyor. A belt arranged in a loop is trained around the reversing wheel and the bearing surface. A carryway segment of the belt loop extends from the infeed end to the exit end of the conveyor. The belt includes a plurality of rollers that extend through the thickness of the belt. The rollers roll on the bearing surface as the belt advances along the carryway from the infeed end to the exit end in a conveying direction. 
         [0005]    In yet another aspect of the invention, a conveyor comprises a conveyor belt having rollers extending through the thickness of the conveyor belt. The conveyor belt advances in a conveying direction from an upstream end to a downstream end of a carryway segment of a conveying path. A bearing surface has a planar portion supporting the conveyor belt on the carryway segment and a stationary convex portion having a first end generally continuous with the planar portion at the upstream end and a second end below the plane of the planar portion. Tension in the advancing conveyor belt conforms the conveyor belt to the convex portion of the bearing surface and causes the rollers to rotate by contact with the convex portion so that the rollers are already rotating as they approach the carryway portion of the bearing surface at the upstream end of the conveyor. 
     
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0006]    These features and aspects of the invention are better understood by reference to the following description, appended claims, and accompanying drawings, in which: 
           [0007]      FIG. 1  is a side elevation view of a portion of a roller-belt conveyor embodying features of the invention, including a bearing surface in a reversing portion of the conveying path; 
           [0008]      FIG. 2  is an isometric view of a conveyor pan providing a bearing surface usable in the conveyor of  FIG. 1 ; 
           [0009]      FIG. 3  is an isometric view of two wearstrips providing a portion of a bearing surface usable in the conveyor of  FIG. 1 ; 
           [0010]      FIG. 4  is an axonometric view of a portion of a roller belt supported by wearstrips as in  FIG. 3  in a conveyor as in  FIG. 1 ; 
           [0011]      FIG. 5  is a cross section taken along lines  5 - 5  of  FIG. 4 ; 
           [0012]      FIG. 6  is a top plan view of the infeed portion of another version of a roller-belt conveyor (with the belt removed to simplify the drawing) embodying features of the invention, including wearstrips extending from the carryway into the reversing portion at the infeed end of the conveyor; and 
           [0013]      FIG. 7  is a prior art roller-belt riding atop a conventional bearing surface in a separation conveyor. 
       
    
    
     DETAILED DESCRIPTION 
       [0014]    One version of a roller-belt conveyor embodying features of the invention is shown in  FIG. 1 . The conveyor  24  transports articles on a roller belt  12 , which forms an endless belt loop defining a belt path. The belt path can be considered to be divided into four segments: (a) an upper carryway segment  26  along which articles are conveyed in a conveying direction  16 ; (b) a lower returnway segment  28  (shown in part) below the carryway segment; (c) a first reversing segment  30  at an upstream, or infeed, end  31  of the conveyor along which the roller belt transitions upward from the returnway to the carryway; and (d) a second reversing segment  32  at a downstream, or exit, end  33  of the conveyor along which the roller belt transitions downward from the carryway to the returnway. A reversing wheel  36 , which may be a drive drum or a drive sprocket mounted on a shaft  38  and driven by a motor (not shown) to rotate in the direction of the arrow  38 , engages the underside of the belt loop in the second reversing segment to drive the belt and transition it to the returnway. Alternatively, the roller belt may be driven in the returnway segment by a drum or sprocket. In that case, the reversing wheel at the exit end of the conveyor is an idle wheel with its shaft not coupled directly to a drive motor. 
         [0015]    The roller belt  12  includes a plurality of rollers  10  having salient portions that protrude past inner  40  and outer  41  sides of the belt. Articles  42  are supported atop the salient portions of the rollers extending above the outer side of the belt along the carryway. The salient portions of the rollers extending past the inner side of the belt on the carryway ride along a planar carryway bearing surface  44 . As the belt advances, the rollers roll on the bearing surface and rotate in the direction of the arrows  18 . The rotation of the rollers propels articles in the direction of belt travel at twice the speed of the belt if the rollers don&#39;t slip as they roll along the bearing surface. In this way, the conveyor increases the spacing between consecutive conveyed articles. 
         [0016]    At the downstream, or exit, end  33  of the conveyor, the planar bearing surface  44  terminates upstream of the reversing wheel to avoid interference. There is no reversing wheel at the upstream end  31  of the conveyor in this version. Instead, the roller belt reverses around a stationary convex bearing surface  46  in the first reversing segment. In this version, the convex bearing surface is continuous with the planar bearing surface  44 . Tension in the advancing roller belt conforms the belt to the convex bearing surface as the belt is pulled through the first reversing segment at the upstream end of the conveyor. By providing a bearing surface for the rollers in the first reversing segment, the convex bearing surface allows the rollers to rotate before they reach the carryway. Because all the rollers at the upstream end of the conveyor are rotating at full speed before they enter the carryway, articles fed onto the conveyor at the upstream end are immediately pulled away by the rotating rollers. There is no delay due to non-rotating rollers at the infeed to the conveyor. 
         [0017]    One version of the bearing surfaces of  FIG. 1  is shown in  FIG. 2 . The bearing surfaces are formed on a sheet  48  that includes a planar portion  50  and a convex portion  51 . The sheet is continuous across the width of the conveyor in the carryway segment and in the first reversing segment. When viewed from the side edge  52  of the sheet, the convex portion is C-shaped with a slightly upturned lip  54  at its lower end to prevent the belt from snagging as it first encounters the convex bearing surface. The sheet may be made of metal, which may be coated with a synthetic material to enhance the rolling engagement of the rollers on the bearing surface, or of a synthetic material with desirable rolling properties. The sheet may be a single bent sheet forming one continuous bearing surface or may be made of two sections (the planar portion and the convex portion) separated by a small gap at the interface  56  between the two portions. 
         [0018]      FIG. 3  shows an alternative embodiment of the bearing surface. In this version, the bearing surfaces are segmented across the width of the conveyor. Parallel linear wearstrips  58  provide planar bearing surfaces along the carryway. C-shaped wearstrips  60  provide convex outer bearing surfaces  61  in the first reversing segment. The linear and convex wearstrips are shown separated by a small gap  62  at the interface between the first reversing segment and the carryway segment. Of course, a continuous wearstrip bent to form the convex portion at one end could be used instead. 
         [0019]    Further details of a roller belt and the planar portion of the wearstrips of  FIG. 3  along the carryway are shown in  FIGS. 4 and 5 . The portion of the roller belt shown is a modular plastic belt  64  constructed of rows  66 ,  67  of one or more belt modules, such as edge modules  68  and interior modules  69 , arranged side by side to form a row. Hinge eyes  70  at the leading and trailing ends of each belt row are interleaved with corresponding hinge eyes of a consecutive row and connected together by a hinge rod  72  received in the lateral passageway formed by the aligned, interleaved hinge eyes. Rollers  10  are mounted in cavities  74  formed in the interior of the modules. The rollers are arranged in parallel lanes. The linear wearstrips  58  are also arranged in parallel on spacings equal to the spacings of the lanes of belt rollers to provide planar bearing surfaces underlying each longitudinal lane of rollers. Each roller has a diameter greater than the thickness of the belt so that salient portions of the rollers protrude past the inner  40  and outer  41  sides of the belt. The rollers in this version rotate on axles  76  spanning the cavities and supported at their ends in the interior of the belt modules. Bores in the cylindrical rollers receive the axles. In this example, the axles are arranged perpendicular to the direction of belt travel so that the rollers rotate in the direction of belt travel as the belt advances. Recesses  78  formed in the belt modules on the inner side of the belt loop include drive surfaces that are engaged by driving surfaces, such as teeth, on the reversing wheel. 
         [0020]    In another version of the conveyor shown in  FIG. 6 , reversing wheels  80 , or sprockets, mounted on a shaft  81  supported for rotation in bearing blocks  83 , are used in the first reversing segment. Planar bearing surfaces  82  extend from the carryway segment  26  upstream into the first reversing segment  30  past the centerline  84  of the shaft. The extension of the linear bearing surface into the first reversing portion provides a bearing surface for the roller belt rollers to roll on at the upstream, infeed end of the conveyor. Consequently, articles fed onto the roller-belt conveyor immediately encounter rotating rollers. 
         [0021]    Thus, the various versions of roller-belt conveyors described provide immediate pull-away of articles transferred to the infeed end of a separation conveyor. 
         [0022]    Although the invention has been described in detail with respect to a few preferred versions, other versions are possible. For example, the roller axles in the conveyor belt need not be oriented perpendicular to the direction of belt travel. They could instead be oriented oblique to the direction of belt travel to provide an additional lateral component of motion to conveyed articles. As another example, spherical roller balls without axles, rather than the generally cylindrical rollers described, could be used as belt rollers. As still another example, the convex bearing surface could alternatively be realized as the outer surface of a stationary drum or shoe. So, as these few examples suggest, the scope of the claims is not meant to be limited to the versions described in detail.