Abstract:
A sorting switch for diverting articles from one or more infeed conveyors to two or more outfeed conveyors. A cannulae pre-alignment conveyor receives articles from one or more infeed conveyors and selectively diverts individual articles into two or more lateral regions for delivery to an alignment conveyor downstream. The alignment conveyor more precisely aligns the articles within each of the regions for delivery to outfeed conveyors at the downstream end of the alignment conveyor. The alignment and pre-alignment conveyors are realized as belt conveyors with rollers arranged to rotate universally or on axes in specific orientations. In some versions, a belt&#39;s rollers roll on bearing surfaces whenever the belt is advancing. In other versions, rollers are selective actuated by moving bearing surfaces. In yet other versions, rollers are not contacted by bearing surfaces at all.

Description:
BACKGROUND 
     The invention relates generally to power-driven conveyors and, more particularly, to horizontal switches including conveyor belts with selectively rotatable rollers useful in diverting conveyed articles to selected positions across the width of the belt. 
     In the package-handling industry, switches are used to merge, divert, or sort packages or articles received from one or more infeed conveyors and discharged onto one or more output conveyors. In a typical sorting application, as illustrated in  FIG. 20 , a switch  20  sorts articles  22  received from an infeed conveyor  24  by selectively diverting individual articles to one or the other of two parallel outfeed conveyors  26 ,  27 . Shoe sorters are often used as sorting switches in this application. 
     One typical shoe sorter switch includes an endless conveyor belt or chain constructed of a series of slats flanked by drive chains. Another typical sorter includes rods uniformly spaced between parallel drive chains. A shoe for pushing articles across the sorter is movably attached to each slat or between consecutive rods. Typically, the shoe has an appendage that extends downward of the slat or between the rods. A guide track arrangement in the conveyor frame beneath the conveyor guides the shoes across the conveyor as it is driven in the conveying direction. The specific arrangement of the guide track programs the system to push conveyed articles to specified lateral positions on the sorter. 
     But these chain-driven sorting switches have shortcomings. One shortcoming is that their construction limits the placement of connecting joints between consecutive slats or rods because of interference with the shoes and associated appendages. For that reason, the slats or rods can sag in the middle because they are supported mainly at the drive chains positioned out of the shoe&#39;s travel range at the side edges of the slats. This problem is especially noticeable on wider conveyors. Another shortcoming is that the shoe mechanisms and the guide track arrangement can be complex and, consequently, expensive. 
     Roller conveyors are also used as shoe sorters in many applications, especially for heavy articles, such as tires, and also for beverage cases and for low-profile, multi-sized articles, such as packages and mail. But one of the problems with roller conveyors is that these metal conveyors can be noisy, especially as their bearings wear. Frequent maintenance operations, such as lubricating and tightening, and repairs are a way of life with roller conveyors. 
     Thus, there is a need for a conveyor that can sort and divert conveyed articles, such as cases and packages, but without the shortcomings of shoe sorters or roller conveyors. 
     SUMMARY 
     This need and other needs are satisfied by a switch embodying features of the invention. One version of the switch comprises an alignment conveyor having a conveying surface that extends longitudinally in a conveying direction from an upstream end to a downstream end and laterally in width from a first side edge to a second side edge. The alignment conveyor includes a carryway having bearing surfaces and at least one conveyor belt advancing along the carryway in the conveying direction. The conveyor belt forms the conveying surface and also includes rollers rotatable on axes oblique to the conveying direction. The rollers extend upward through the thickness of the belt into supporting contact with conveyed articles along the carryway and downward into rolling contact with the bearing surfaces in the carryway. The conveying surface is divided into a first region extending laterally inward from the first side edge and a second region extending laterally inward from the second side edge. The rollers in the first region are oriented to rotate to direct conveyed articles in the first region toward the first side edge, and the rollers in the second region are oriented to rotate to direct conveyed articles in the second region toward the second side edge. A pre-alignment conveyor advances articles in the conveying direction and feeds the articles selectively to the first and second regions of the conveying surface at the upstream end of the alignment conveyor. 
     In another aspect of the invention, a switch comprises a first conveyor advancing in a conveying direction and receiving articles from an infeed conveyor and a second conveyor advancing in the conveying direction and receiving articles from the first conveyor. The first conveyor includes a roller belt advancing in the conveying direction and having rollers extending through the belt. The rollers are arranged to rotate on axes oblique to the conveying direction. A bearing surface underlying the roller belt is selectively actuatable between a first position out of contact with the rollers and a second position contacting the rollers and causing the rollers to rotate as the roller belt advances. Thus, articles conveyed atop the rollers while the bearing surface is in the second position are pushed to one side of the roller belt by the rotating rollers as the roller belt advances. The second conveyor includes at last one roller belt extending in width from a first side to a second side. Rollers extending through the belt are arranged to rotate on axes oblique to the conveying direction. The one or more roller belts include a first region extending inward from the first side positioned to receive articles pushed to one side on the first conveyor and a second region extending inward from the second side positioned to receive the other articles. Bearing surfaces underlie at least a portion of the rollers to cause the rollers to rotate by contact with the bearing surfaces as the roller belt or belts advance in the conveying direction. The rollers in the second region are in constant contact with the underlying bearing surfaces and are arranged to rotate on second oblique axes oriented to direct articles conveyed atop the rollers in the second region toward the second side. The rollers in the first region are out of contact with the bearing surfaces or are in contact with the underlying bearing surfaces and arranged to rotate on first oblique axes oriented to direct articles conveyed atop the rollers in the first region toward the first side. 
     In another aspect of the invention, a switch for distributing articles received from an infeed conveyor to a plurality of outfeed conveyors comprises an alignment conveyor and a pre-alignment conveyor. The alignment conveyor advances from an upstream end to a downstream end in a conveying direction and has a conveying surface divided laterally in width into a plurality of lanes. Each lane terminates in an associated outfeed position marking an outfeed conveyor at the downstream end of the alignment conveyor. Articles received in each lane at the upstream end are directed to the associated outfeed position of the lane as the articles are conveyed from the upstream end to the downstream end of the alignment conveyor. The pre-alignment conveyor, which is disposed at the upstream end of the alignment conveyor and extends from an upstream end to a downstream end in the conveying direction, conveys articles received from an infeed conveyor at the upstream end. The pre-alignment conveyor selectively shifts the articles laterally to distribute the articles among the lanes of the alignment conveyor. The alignment conveyor includes at least one roller belt having article-supporting rollers extending through the belt and rotatable on axes oblique to the conveying direction. Bearing surfaces underlie the roller belt and contact at least a portion of the rollers to cause the rollers to rotate and direct articles laterally as the roller belt advances in the conveying direction. The pre-alignment conveyor includes a roller belt with article-supporting rollers arranged to enable articles conveyed atop the rollers to be directed laterally across the pre-alignment conveyor as the roller belt advances. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These features and aspects of the invention, as well as its advantages, are better understood by reference to the following description, appended claims, and accompanying drawings, in which: 
         FIG. 1  is an isometric view of a conveyor switch embodying features of the invention, including selectively actuated oblique-roller belts in a pre-alignment conveyor; 
         FIG. 2  is a top plan schematic of the switch of  FIG. 1  illustrating its operation; 
         FIG. 3  is an isometric view of a portion of a modular roller conveyor belt usable in a switch as in  FIG. 1 ; 
         FIG. 4  is a bottom plan view of a portion of the roller belt of  FIG. 3 ; 
         FIG. 5  is a front elevation view of the belt portion of  FIG. 4  showing the rollers engaging underlying bearing surfaces; 
         FIG. 6  is an isometric view of another version of bearing surfaces engaging the rollers of a roller belt usable in a switch as in  FIG. 1 ; 
         FIG. 7  is an isometric view of another version of a switch embodying features of the invention, including a pre-alignment conveyor with two ball belts and selectively actuated roller balls; 
         FIG. 8  is a top plan schematic of the switch of  FIG. 7  illustrating its operation; 
         FIG. 9  is an axonometric view of a portion of a ball belt and a ball-contacting friction-top belt usable in a switch as in  FIG. 7 ; 
         FIG. 10  is an isometric view of another version of a switch embodying features of the invention, including a pre-alignment conveyor with a pair of transverse-roller belts selectively drivable in opposite directions; 
         FIG. 11  is a top plan schematic of the switch of  FIG. 10  illustrating its operation; 
         FIG. 12  is an isometric view of yet another version of a switch embodying features of the invention, including a pre-alignment conveyor with an oblique-roller belt having selectively actuated regions; 
         FIG. 13  is a top plan schematic of the switch of  FIG. 12  illustrating its operation; 
         FIG. 14  is an isometric view of another version of a switch embodying features of the invention, including a pre-alignment conveyor with a single, selectively driven, unidirectional transverse-roller belt; 
         FIG. 15  is a top plan schematic of the switch of  FIG. 14  illustrating its operation; 
         FIG. 16  is an isometric view of another version of a switch embodying features of the invention, including a pre-alignment conveyor with an oblique-roller belt having a selectively actuated region beside a permanently actuated region; 
         FIG. 17  is a top plan schematic of the switch of  FIG. 16  illustrating its operation; 
         FIG. 18  is an isometric view of another version of a switch embodying features of the invention, including a pre-alignment conveyor having a selectively tiltable transverse-roller belt; 
         FIG. 19  is a top plan schematic of the switch of  FIG. 18  illustrating its operation; and 
         FIG. 20  is a top plan schematic of a switch conveyor fed by a single infeed conveyor and feeding two parallel outfeed conveyors. 
     
    
    
     DETAILED DESCRIPTION 
     One version of a switch is shown in  FIG. 1 . The switch  220  comprises an alignment conveyor  28  fed by a pre-alignment conveyor  30 . The alignment conveyor includes a roller belt  32  trained about drive and idler sprocket sets  34 ,  35 . The belt is supported in an upper carryway formed by wearstrips  36  mounted to a carryway bed  38 . The upper surfaces of the wearstrips form bearing surfaces on which the roller belt rides. The sprocket sets are mounted on shafts  40  rotatably mounted to a conveyor frame (not shown) in bearing blocks  42 . A motor  44  coupled to the drive shaft advances the roller belt longitudinally in a conveying direction  46  from an upstream end  48  to a downstream end  49 . The roller belt is supported by shoes or rollers  50  in a lower returnway. 
     Rollers  52  extend through the thickness of the belt into contact with the bearing surfaces of the wearstrips below the belt on the carryway and into supporting contact with articles conveyed atop the belt. As the belt advances in the conveying direction, the rollers roll on the wearstrips and rotate on their axes to further propel conveyed articles. The conveying surface of the roller belt is divided into two regions, or longitudinal lanes, along the carryway. The rollers in a first region  54  extending inward of a first side edge  56  of the belt are oriented on axes oblique to the conveying direction to propel conveyed articles toward the first side edge as indicated by arrow  58 . The rollers in a second region  55  extending inward of an opposite second side edge  57  of the belt are oriented on axes oblique to the conveying direction to propel articles toward the second side edge as indicated by arrow  59 . Thus, an article received on the belt at the upstream end in the first region is diverted toward the first side edge, and an article received in the second region is diverted toward the second side edge. Side rails (not shown) flanking the belt at the first and second side edges form a registration surface along the edges and prevent diverted articles from falling off the conveyor. Articles exiting the belt in the first region are transferred off the downstream end to one of the outfeed conveyors, and articles exiting the belt in the second region are transferred to the other outfeed conveyor. 
     The pre-alignment conveyor  30  is programmed to selectively feed articles to the first or second region of the alignment conveyor  28 . The pre-alignment conveyor comprises two oblique-roller belts  60 ,  61  in series. The two belts advance in the conveying direction driven by individual motors  44  coupled to drive shafts  40  and sprocket sets  34 . The carryways of the oblique-roller belts include bearing surfaces  62 ,  63  that are selectively movable into and out of contact with the rollers. The bearing surfaces  62 ,  63  may be raised and lowered into and out of contact with the rollers as indicated by arrows  64 ,  65  or moved side to side into and out of contact. Various means may be used to selectively rotate the rollers by moving the bearing surfaces; e.g., hydraulic or pneumatic pistons, solenoids, electric motors. When the bearing surface contacts the rollers, they roll on the bearing surface and rotate to propel conveyed articles toward a side edge of the belt as it advances. The rollers in the upstream belt  60  are arranged to rotate on axes oblique to the conveying direction to propel articles toward one side edge of the conveyor as indicated by arrow  66 . The rollers in the downstream belt  61  are arranged to divert articles toward the other side edge as indicated by arrow  67 . Raising or otherwise moving the bearing surfaces into contact with the rollers actuates the rollers to roll as the belts advance. 
     The operation of the switch  120  is illustrated in  FIG. 2 . If an article  22  fed onto the pre-alignment conveyor  30  is scheduled to be diverted to the second region  55  of the alignment conveyor for delivery to an outfeed conveyor at the second side  57  of the downstream end  59 , the rollers in the upstream oblique-roller belt  60  are deactuated while the rollers in the downstream oblique-roller belt  61  are actuated. In this way, the article  22  is conveyed by the upstream belt without sidewise motion because its rollers are not rotated by rolling contact with the underlying deactuated bearing surfaces. The rollers in the downstream belt  61  are actuated by positioning its underlying bearing surfaces in contact with the rollers. As the downstream belt advances, the article is diverted toward the second region  55  of the alignment conveyor  28 . The pre-aligned article delivered to the second region of the alignment conveyor over the interposed deadplate  68  ( FIG. 1 ) is moved further toward the second side on the alignment belt  32  as it advances until it is transferred off the downstream end of the switch to the outfeed conveyor at the second side. If a subsequent article  22 ′ is scheduled to be delivered to the outfeed conveyor at the first side  56  of the switch, the rollers in the upstream oblique-roller belt  60  are actuated to divert the article toward the first side edge, and the rollers in the downstream pre-alignment belt  61  are deactuated to maintain the article  22 ′ in position laterally to be received in the first region  54  of the alignment conveyor  32  for delivery to the outfeed conveyor at the first side. Sensors  69  positioned at strategic locations along the conveying path, such as at transitions between belts, signal the position of an article to a controller (not shown) that controls the actuation of the bearing surfaces. 
     One realization of the alignment belt  32  of  FIG. 1  is shown in  FIG. 3 . The belt shown is a modular plastic conveyor belt constructed of one or more belt modules arranged side by side in rows  70 ,  70 ′. The rows are held together by hinge pins  72  confined in lateral passageways  74  through aligned hinge eyes  76  at opposite ends of each row. The rollers  52  in the first region  54  are mounted in cavities  78  on axes oblique to the conveying direction  46 . The angle of the axes causes the rollers to rotate in an oblique direction  58 . The rollers in the second region  55  are mounted in cavities on axes oriented to rotate in another oblique direction  59 . As shown in  FIG. 4 , the rollers  52  are mounted on axles  80  extending through opposite walls  82  of the cavities  78 . The axles, which are received in central bores through the rollers, define the axes of rotation of the rollers. As shown in  FIG. 5 , salient portions of the rollers  52  extend past top  84  and bottom  85  surfaces of the belt. The tops of the rollers support conveyed articles  22 . The bottoms of the rollers ride along bearing surfaces  86 , which may be permanently positioned in contact with the rollers, as shown, or selectively movable into and out of contact. If the bearing surfaces are movable into and out of contact with the rollers, a supporting rail  88  is provided to support the belt along longitudinal lanes devoid of rollers. Many of the details in  FIGS. 3-5  may apply to any of the roller belts, whether used as pre-alignment belts or alignment belts. 
     An alternative bearing surface is shown in  FIG. 6 . In this example, the flat bearing surfaces of wearstrips or wear pans is replaced by an array of long rollers  90  whose axes of rotation  92  are parallel to the conveying direction  46 . Like the flat bearing surfaces, the long-roller bearing surfaces can be actuated by appropriate means for selectively rotating the rollers into and out of contact with the bottoms of the belt rollers  52 . Belt rollers with an outer rubber tire  94  are particularly effective because they get better traction on the peripheries of the long rollers. The belt section shown in  FIG. 6  with all the rollers oriented parallel to one side is one realization of the downstream pre-alignment belt  61  in  FIG. 1 . If the angle of the belt rollers in  FIG. 6  is changed to direct articles toward the other side, the belt can be used as the upstream pre-alignment belt  60  of  FIG. 1 . 
     Another version of a switch is shown in  FIG. 7 . The switch  320 , like the switch  220  in  FIG. 1 , has an alignment conveyor  28  and a pre-alignment conveyor  330 . The alignment conveyor shown is identical to the alignment conveyor in the switch of  FIG. 1 . The pre-alignment conveyor differs in structure, but not function, from the pre-alignment conveyor in  FIG. 1 . Instead of oblique-roller belts, the pre-alignment conveyor of  FIG. 7  uses roller-ball belts  96  with universally rotatable spherical roller balls  98  mounted in cavities  100  opening onto the top and bottom sides of the belt, as also shown in  FIG. 9 . Bearing surfaces for the roller balls is provided by a friction-top belt  102  running inside the loop of the roller-ball belt in a direction  104  transverse to the conveying direction  46 . Rubber or elastomeric pads  106  molded or attached to the outer surface of the friction-top belt contact the bottoms of the roller balls and cause them to rotate to direct conveyed articles  22  across the roller-ball belt opposite to the direction of travel  104  of the friction-top belt. The two ball belts, which constitute means for selectively rotating the rollers, could alternatively be replaced by a single ball belt with a single bidirectional friction-top belt below to divert articles selectively toward one side or the other. As shown in  FIG. 7 , the rollers in a downstream ball belt  97  in the pre-alignment conveyor are driven by a friction-top belt  103  traveling in a direction  105  opposite to the direction  104  of the friction-top belt  102  engaging the roller balls of the upstream ball belt  96 . 
     The operation of the pre-alignment conveyor  330  is shown in  FIG. 8 . As a first article  22 , destined for the outfeed conveyor at the downstream end of the second region  55  of the alignment conveyor  28 , is received on the pre-alignment conveyor, the upstream friction-top belt  102  is stopped or disengaged from contact with the roller balls extending through the upstream roller-ball belt  96 . This allows the article  22  to proceed along the upstream ball belt without being shifted laterally. The downstream friction-top belt  103  is timely activated to engage the rollers in the downstream roller-ball belt  97  to push the article, as indicated by arrow  107 , toward the second region  55  of the alignment conveyor  28 . Another article  22 ′, destined for the outfeed conveyor receiving articles from the first region  54  of the alignment conveyor, is pushed in the opposite direction  106  by the roller balls&#39; engagement with the upstream friction-top belt  102 . The downstream friction-top belt is stopped or disengaged from the roller balls in the downstream roller belt  97  to maintain the article&#39;s lateral position for delivery to the first region  54  of the alignment conveyor. 
     A switch with an alternative pre-alignment conveyor is shown in  FIGS. 10 and 11 . The switch  420  has an alignment conveyor as those in  FIGS. 1 and 7 . A pre-alignment conveyor  430  directing conveyed articles  22  selectively to the first or second regions  54 ,  55  of the alignment conveyor is constructed of two parallel transverse-roller belts  108 ,  109  driven in opposite directions  110 ,  111  transverse to the main conveying direction  46 . The belts, which are driven conventionally, such as by motors, drive shafts, and sprockets or pulleys, constitute means for selectively rotating the rollers. The rollers  52  in the transverse-roller belts rotate on axes  112  oriented in the direction of travel  110 ,  111  of the belts. The rollers in the transverse-roller belt do not contact bearing surfaces below the belt and are free to rotate on their axes. This allows articles propelled in the conveying direction on an infeed conveyor to ride across the conveying surfaces of the pre-alignment conveyor atop the freely rotatable rollers. A conveyed article supported atop the rollers is shifted laterally across the conveyor by the advancement of one or the other of the transverse-roller belts. As illustrated in  FIG. 11 , a first article  22  rolling across the rollers in the pre-alignment conveyor is diverted toward the second region  55  of the alignment conveyor  28  by driving the downstream roller belt  109  in the direction  111  toward the second region. The upstream roller belt  108  is stopped as the first article is pushed onto the pre-alignment conveyor  430 . A second article  22 ′, destined for the first region  54  of the alignment conveyor, is diverted toward the first region by advancing the upstream roller belt in the direction  110  indicated. The downstream roller belt is stopped when the second article reaches it. In this way, the second article is allowed to roll across the downstream roller belt toward the first region without further lateral shifting. 
     Another version of a switch is shown in  FIG. 12 . This switch  52  comprises a pre-alignment conveyor  530  feeding an alignment conveyor  528 . The alignment conveyor includes an oblique-roller belt  114  that is divided into first and second regions  54 ′,  55 ′ of unequal width. But, like the rollers in the belts of the alignment conveyors with equal-width first and second regions  54 ,  55 , the rollers in each region of this belt are oriented to push articles toward the first and second side edges  56 ,  57  as indicated by arrows  58 ,  59 . The pre-alignment conveyor  530  diverts articles received from an infeed conveyor generally centrally located across the switch&#39;s width. The pre-alignment conveyor includes an oblique-roller belt  116  driven in the conveying direction  46  by a drive motor  44 . One or more selectively actuatable bearing surfaces  118 ,  118 ′ underlie the belt carryway. As shown, the bearing surfaces are raised and lowered  120  to actuate or deactuate the belt rollers  52 . The rollers are all arranged to rotate on axes oblique to the conveying direction to push articles in the direction of arrow  122  toward the second region  55 ′ of the alignment conveyors when the rollers are actuated by contact with the raised bearing surfaces. Multiple sequentially actuatable bearing surfaces can be used along the length of the pre-alignment belt to allow articles to be closely spaced on the switch for greater throughput. As illustrated in  FIG. 13 , the bearing surfaces  118  are raised to actuate the rollers to push a first conveyed article  22  received from a central infeed conveyor in an oblique direction  122  toward the second side region  55 ′ of the alignment conveyor. The bearing surfaces are lowered to deactivate the rollers in the case of a second article  22 ′ destined for the first region  54 ′ of the alignment conveyor. With the rollers deactivated, the article  22 ′ received on the pre-alignment belt is not shifted laterally and advances straight through to the expanded-width first region  54 ′ of the alignment conveyor, which diverts it further to the outfeed conveyor at that side of the switch. 
     Like the switch in  FIG. 12 , the switch  820  in  FIG. 14  has an alignment conveyor  828  with an oblique-roller belt  114  that is divided into first and second lanes, or regions  54 ′,  55 ′ of unequal width. A pre-alignment conveyor  830  includes a transverse-roller belt  109  that is selectively driven in one direction  117  from the wide region  54 ′ toward the narrow region  55 ′. The rollers  52 , which do not necessarily extend through the thickness of the belt, are free to rotate on their axes  112  without engaging an underlying bearing surface. Thus, the rollers act as idle rollers that rotate only when engaged by an article having a component of motion transverse to the rollers&#39; axes. The forward momentum of articles fed onto the pre-alignment conveyor in the conveying direction  46  carries the articles across the freely rotatable rollers to the alignment conveyor. As shown in  FIG. 15 , an article  22  fed onto the pre-alignment conveyor from an infeed conveyor positioned midway along the upstream end of the pre-alignment conveyor can be directed to either the wide region or the narrow region of the alignment conveyor. If the article is destined for the wide region, the transverse-roller belt is halted and the centrally fed package is allowed to proceed directly across the pre-alignment conveyor to the wide region of the alignment conveyor. If the article is destined for the narrow region of the alignment conveyor, the transverse-roller belt is driven in the direction  117  toward the narrow region to deliver the article to the alignment conveyor. Instead of a transverse-roller belt, a belt having freely rotatable roller balls could be used to similar effect. 
     The switch  620  in  FIG. 16  comprises an alignment conveyor  628  and a pre-alignment conveyor  630  both of which include oblique-roller belts  124 ,  126 . The rollers in the alignment belt are arranged to rotate on axes oblique to the conveying direction  46 . Wearstrips  128  underlie the rollers in a first region  54 ″ of the belt. The rollers roll on the bearing surfaces of the wearstrips to propel conveyed articles toward the first side edge  56  of the switch, as indicated by arrow  130 . The rollers in a second region  55 ″ of the oblique-roller alignment belt are mounted to rotate on axes parallel to the axes of the rollers in the first region. But the rollers in the second region do not engage bearing surfaces below the belt. Consequently, articles received in the second region are not shifted laterally across the belt and maintain their lateral positions. In this example, the first region with the actuated rollers is wider than the second region with unactuated rollers. The pre-alignment conveyor  630 , which diverts articles received from an infeed conveyor to either the first region or the second region of the alignment conveyor, is also divided into two regions that correspond to the regions of the alignment conveyor. In a first region  132 , the oblique-roller belt  126  is supported on one or more selectively actuated bearing surfaces  134 . The bearing surfaces are raised and lowered as indicated by arrows  135  between roller-actuated and idle positions. Because the axes of the rollers in the pre-alignment belt are mirror images of the axes of the rollers in the alignment conveyor belt  124 , the rollers, when actuated, push conveyed articles toward a second region  133 , as indicated by arrow  136 . The rollers in the second region  133  ride along a bearing surface  138  held permanently in place to keep the rollers in the second region in constant rotation to urge articles toward that side of the switch. The operation of the switch is illustrated in  FIG. 17 . A first article  22  fed by an infeed conveyor at the center of the pre-alignment conveyor  630  in the wider first region  132  and destined for the second region  55 ″ of the alignment conveyor, is pushed in the direction of arrow  136  by rollers actuated by the raising of the bearing surfaces  134 . Once an article is transferred to the second region of the pre-alignment belt, the constantly actuated rollers continue to push the article in the same direction to ensure that, by the time the article is advanced to the alignment conveyor, it lies in the second region  55 ″ along which it is conveyed without further lateral translation to an outfeed conveyor at the downstream end of the second region. A centrally fed second article  22 ′ destined for the first region  54 ″ of the alignment conveyor is allowed to pass along the pre-alignment conveyor without diversion by lowering the underlying bearing surfaces  134  into the deactivated position out of contact with the rollers. As indicated in  FIG. 15 , the rollers on the outermost side of the first region do not require underlying bearing surfaces for the rollers to ride on, unless the infeed conveyor is positioned to feed articles in that portion of the first region. Articles received in the first region  54 ″ of the alignment conveyor  628  are translated laterally even farther by the constantly actuated rollers in the second region. The second articles then exit the downstream end of the switch onto another outfeed conveyor. 
     The switch  720  shown in  FIG. 18  comprises a pre-alignment conveyor  730  feeding articles to one of two side-by-side regions  54 ,  55  of an alignment conveyor  728 . Unlike the conveyor of  FIG. 1 , this alignment conveyor is constructed of two side-by-side oblique-roller belts  140 ,  141 . Each belt forms one of the two regions, and the rollers in each belt ride on permanent wearstrips  128 . As the belts advance along the carryway, the rollers rotate. The rollers on the first belt  140  are mounted to rotate on axes oriented to push articles in the direction of arrow  142 . The rollers on the second belt  141  are directed to push articles in the direction of arrow  143 . The two oblique-roller belts may be driven in the conveying direction  46  by the same motor on the same shafts or by separate motors  44 ,  44 ′ on separate shafts  40 ,  40 ′, as shown. The pre-alignment conveyor  730  includes a single transverse-roller belt  144  driven by a motor  44  in the conveying direction. The transverse-roller belt has rollers mounted on axles defining axes  146  parallel to the conveying direction  46 . The pre-alignment conveyor also includes a hydraulically, pneumatically, or electrically activated tilt mechanism that tilts the conveyor about a tilt axis  148  along the longitudinal centerline of the conveying surface, as indicated by two-headed arrow  150 . As shown in  FIG. 19 , tilting the pre-alignment conveyor to the right causes a first article  22  atop the transverse-roller belt to slide downward toward the first side edge  56  of the switch atop the transverse rollers. The tilt mechanism rights the pre-alignment conveyor to transfer the article onto the first region  54  of the alignment conveyor. Similarly, the tilt mechanism tilts the transverse-roller belt to the left to divert a second conveyed article  22 ′ to the second region  55  of the alignment conveyor. In this way, articles can be switched from a single file in an infeed conveyor to two separated outfeed conveyors. The tilt mechanism constitutes means for selectively rotating the rollers. 
     Although the invention has been described in detail with reference to a few preferred versions, other versions are possible. For example, many of the various alignment conveyor configurations may be used with several of the other pre-alignment conveyor configurations. As another example, the long-roller bearing surfaces may be used instead of flat wearstrips or wear pans in any embodiment. As yet another example, all the switches are shown for simplicity as having a single, centrally positioned infeed conveyor and two parallel outfeed conveyors. It is, of course, possible to extend the conveyors in width and to form multiple regions to sort the articles from more than one infeed into more than two outfeeds. And, although sensors were shown in only one of the versions, they would normally be used in all of the versions to signal a controller of the presence of a conveyed article at a strategic location, e.g., a transition from one conveyor to another or from one actuation zone to another. So, as these few examples suggest, the scope of the invention is not meant to be limited to the versions described herein.