Abstract:
A conveyor and method for moving articles across a conveying surface using electromagnetically operated movers in a conveyor belt. The movers are retained in tracks in the conveyor belt. A magnetic field source produces a magnetic field that varies across the width of the belt. The magnetic field interacts with electrically conductive material, ferromagnetic material, or permanent magnets in the movers to propel the movers and divert articles engaged by the movers across the belt. Movers with retractable pushers fold down at the sides of the belt to allow articles pushed by other movers to pass over and off the side of the belt.

Description:
BACKGROUND 
     The invention relates generally to power-driven conveyors and more particularly to shoe-type diverting conveyors. 
     Diverting conveyors, such as shoe sorters, are used to divert articles across the width of a conveyor as the conveyor transports the articles in a conveying direction. Typical shoe sorters include article-pushing elements referred to as shoes that are driven laterally across the conveyor to push articles off one or both sides of the conveyor to one or more outfeed locations. Slat conveyors and modular conveyor belts are used as the platform for the shoes, which ride in tracks extending across the widths of the slats or belt modules. The shoes are conventionally blocked-shaped with depending structural elements that keep the shoe in the track and serve as cam followers that extend below to be guided by carryway guides that control the lateral positions of the shoes. Although shoe sorters are widely used in package-handling applications, they are not so useful in food-handling and other applications where sanitation is important because they are not easy to clean. Another problem is the noise caused by impacts between the shoes and the carryway guides. 
     SUMMARY 
     One version of a conveyor embodying features of the invention comprises a conveyor belt and a magnetic field source. The conveyor belt has tracks that extend across the conveyor belt transverse to the direction of belt travel. Movers are retained in the tracks to move along the tracks across the belt. The movers have contact faces that engage articles conveyed on the belt. The magnetic field source provides a magnetic field that interacts with the movers to propel the movers along the tracks and conveyed articles engaged by the contact faces across the conveyor belt. 
     In another aspect of the invention, a conveyor comprises a conveyor belt having atop conveying surface and tracks that extend across the conveyor belt transverse to the direction of belt travel. Movers retained in the tracks move along the tracks across the belt. The movers have contact faces that engage articles conveyed on the belt. The movers include pushers on which the contact faces are formed to push conveyed articles across the top conveying surface in an extended position of the movers. Joints on the movers allow the pushers to fold down in a retracted position to a level at or below the top conveying surface. 
     In yet another aspect of the invention, a method for moving articles across the conveying surface of the conveyor comprises: (a) creating a magnetic field that varies spatially or temporally across the width of a conveyor; (b) coupling the magnetic field to movers mounted in the conveyor to propel the movers across the width of the conveyor with the varying magnetic field; and (c) engaging articles on the conveying surface of the conveyor with the movers to move the articles across the width of the conveying surface. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These aspects and features of the invention 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 diverting conveyor embodying features of the invention; 
         FIG. 2  is an isometric view of one version of a belt module usable in a conveyor as in  FIG. 1 ; 
         FIG. 3  is a cross section of the belt module of  FIG. 2  taken along lines  3 - 3 ; 
         FIG. 4  is an isometric view of a mover for a conveyor as in  FIG. 1 ; 
         FIG. 5  is a bottom axonometric view of a mover usable in a conveyor as in  FIG. 1  and having permanent magnets in its base; 
         FIG. 6  is a bottom axonometric view of another mover usable in a conveyor as in  FIG. 1  and having a Halbach array of magnets in its base; 
         FIG. 7  is an isometric view of yet another mover usable in a conveyor as in  FIG. 1  illustrating a mover with a toothed linear rotor driven by a linear stator. 
         FIGS. 8A-8D  are isometric views of the conveyor of  FIG. 1  illustrating the step-by-step operation of the conveyor as a sorter; 
         FIG. 9  is an isometric view of another version of a belt module usable in conveyor as in  FIG. 1 , in which the movers fold down from an extended position to a retracted position; 
         FIG. 10  is an axonometric view of a mover for use in a belt module as in  FIG. 9 ; 
         FIG. 11  is an enlarged view of an outside edge portion of the module of  FIG. 9 , showing the mover in a retracted position; and 
         FIGS. 12A and 12B  are enlarged views of the outside edge portion of the module of  FIG. 9  showing the mover moving from a retracted position to an extended position. 
     
    
    
     DETAILED DESCRIPTION 
     A portion of a conveyor embodying features of the invention is shown in  FIG. 1 . The conveyor  20  comprises a conveyor belt  22  that advances in a direction of belt travel  24 . The belt may be driven by any conventional drive means (not shown), such as motor-driven drums, pulleys, or sprockets, or by a linear induction motor. In the example shown, the conveyor belt is a modular plastic conveyor belt constructed of a series of belt modules  26  arranged in rows linked together at hinge joints  28 , but a slat belt could alternatively be used. The conveyor belt  22  extends in width from a first outside edge  30  to an opposite second outside edge  31 . Some or all of the modules—all, in the example of  FIG. 1 —have tracks  32  extending transversely across the width of the modules. As shown in  FIGS. 1 and 2 , a shoe, more generically, a mover  34 , is retained in the track  32  of each belt module  26 . The mover is able to slide along the track in both directions  36 . Hinge elements  37  at opposite ends of each module are interleaved with the hinge elements of adjacent modules and linked by hinge pins  39  to form the hinge joints  28  between adjacent rows. A magnetic field source  38  positioned under the upper carryway path of the conveyor belt  22  produces a magnetic or electromagnetic field that varies spatially or temporally across the width of the conveyor in either direction, as indicated by two-headed arrow  40  in  FIG. 1 . The varying magnetic field interacts with metallic material in the movers  34  to propel the movers across the width of the belt without the contact present in cam-guided diverters. The movers divert articles  42  conveyed atop the belt&#39;s top conveying surface  44  across the belt to a selected lateral position or completely off the side of the belt. Magnetic field sources may be installed at selected positions along the length of the conveyor to provide additional divert zones or mover-return zones. 
     As shown in  FIGS. 3 and 4 , the mover has a pusher portion  46  above the top conveying surface  44  of the belt. The pusher  46  has a contact face  48 , which is shown as a curved surface in this example. The opposite side of the pusher has a flat surface  50 . The pusher portion  46  is connected to a base  52  by an intermediate shank  54 . The base  52  is retained in and rides transversely across the width of the belt module  26  in a slot  56  shaped like an inverted T. The base in this example serves as a skid  52  that rides in the base  58  of the inverted-T slot. The narrow shank  54  extends upward from the skid through the vertical branch of the inverted-T slot, which opens onto the top conveying surface  44  and forms the lateral track  32 . Shoulders  60  formed in the interior of the belt module  26  retain the skid in the slot. Ridges  62  formed on top and bottom sides of the skid  52  reduce sliding friction with the walls bounding the base  58  of the slot and also reduce the wobble of the mover in the slot. Instead of a pusher, the mover could have a support plate with a flat horizontal upper contact surface engaging the bottoms of conveyed articles to divert the articles sitting on the contact face of the mover. 
     The skid  52  includes ferromagnetic or electrically conductive metallic elements. The elements can be in the form of metal plates  64  housed in the skids or can be a metallic material combined with a plastic binder and molded to form the skid. The metal plate  64  could also be made of a ferromagnetic material layered atop an electrically conductive material for increased force. As another example, the metallic elements can be permanent magnets  66  housed within or attached to the base  68  as in  FIG. 5 . Permanent magnets  70  can be arranged with the base  68  in a Halbach array  72  as shown in  FIG. 6  to focus their magnetic field toward the bottom of the conveyor belt and the magnetic field source. And, in the example shown in  FIG. 7 , the metallic element can be in the form of a ferromagnetic linear rotor, or forcer  74 , having a series of teeth  76  forming poles. In this case, the magnetic field generator  38  used in the conveyor  20  of  FIG. 1  comprises a stator  78  having poles  80  matching the teeth  76  to form a linear variable reluctance motor or a linear stepper motor with the rotor  74 . The movers of  FIGS. 5 and 6 , whose metallic elements are permanent magnets, are driven transversely across the conveyor belt by the magnetic field source, which has a linear stator that is energized to produce a traveling magnetic field that interacts with the magnets. The linear stator may be operated with a permanent-magnet forcer as a synchronous ac motor or a brushless dc motor. When electrically conductive metallic elements are used in the mover, the magnetic field generator has a linear stator that produces a traveling magnetic field that induces a current in the electrically conductive metallic elements. The induced current produces a magnetic field in the mover that interacts with the traveling magnetic field to produce a force that propels the mover along the track. In this case, the magnetic field generator&#39;s stator and the mover&#39;s electrically-conductive forcer form a linear induction motor. 
     The operation of the conveyor  20  as a sorter is illustrated in  FIGS. 8A-8D . In  FIG. 8A , an article  42  is shown being conveyed by the conveyor belt  22  in a direction of belt travel  24 . All the movers are shown in their reset positions at one side of the belt. In  FIG. 8B , the magnetic field source  38  is activated to produce a magnetic field that intersects the conveyor and varies across the conveyor in the direction of arrow  82 . The interaction of the magnetic field with the metallic elements in the movers  34  produces a force that propels the movers along their transverse tracks  32 . The contact faces  48  of the movers engage the article  42  and push it across the top conveying surface  26  of the conveyor belt  22  in the direction of arrow  84 . In  FIG. 8C , the article  42  is shown pushed off the side of the conveyor belt  22  by the movers  34 . In  FIG. 8D , the magnetic field source  38  generates a magnetic field that varies in the opposite direction  86  to return the movers  34  to their reset position at the opposite side of the belt. 
     Another version of a conveyor belt module usable in a conveyor as in  FIG. 1  is shown in  FIGS. 9-12 . The belt module  88  has two movers  90 ,  91  riding in the same track  92 . The contact faces  94 ,  94 ′ of the movers are shown as flat. The two faces  94 ,  94 ′ face each other across the module. As shown in  FIG. 10 , each mover has an upper pusher  96  connected to a lower base or skid  98  by an intermediate shank  100 . A pair of guide pins  102  and a pair of pivot pins  104  extend from the sides of the shank  100 . The shank also includes a tab  106  extending away from the skid  98 . The pivot pins  104  are received in hinge eyes  108  at one end of the skid  98 . The resulting hinge joint allows the pusher  96  and the shank  100  to pivot relative to the skid  98 , as indicated by the arrows  110 ,  111  in  FIG. 9 . The track  92  is formed by an inverted-T—shaped slot as in  FIG. 3 , but with a guide slot  112  parallel to the base portion  58  between the base portion and the top conveying surface  113  of the module  88 , as best shown in  FIGS. 11 and 12B . The mover&#39;s guide pins  102  are received in the guide slot  112 . The guide slot  112  has a curved portion  114  that curves downward at each end of the track  92 . The downward curve of the guide slot forces the pusher  96  and the shank  100  to pivot at the hinge until it rests flat in a recess  116  in each of the outside edges  118  of the module. In  FIG. 11 , the mover  90  is shown in its retracted position. The flat contact face  94 ′ of the retracted pusher  96  is generally flush with or below the level of the top conveying surface  113  of the belt module. When the mover  90  is folded down in its retracted position, the other mover  91  can push an article off the side of the belt over the retracted mover  90  along the flat face  94 ′ of the pusher  96 .  FIGS. 12A and 12B  illustrate the mover&#39;s pusher  96  rising to an extended position for pushing articles across the belt. As the magnetic field forces the mover along the track in the direction of arrow  120 , the guide pins riding up the curved portion of the guide slot pivot the mover  90  at its joint as indicated by arrow  110  to its unfolded, extended position in  FIG. 12B . Movers with pivotable pushers may be used in more conventional cam-guided diverting conveyors, as well as in the magnetically driven movers previously described.