Abstract:
A material handling system incorporates one or more transfer conveyor sections configured to selectively discharge articles being conveyed in at least one direction which is disposed at a transverse angle relative to the incoming direction of the article. The transfer conveyor includes rotary cams with circumferential cam tracks which engage cam followers carried respective vertically movable conveying assemblies. Rotation of the cams disposes the carrying surfaces at desired conveying heights for selecting the discharge.

Description:
BACKGROUND 
     The present disclosure relates generally to material handling systems, and is more particularly directed to a material handling system and subsystems thereof having one or more transfer conveyor sections configured to selectively discharge articles being conveyed in at least one direction which is disposed at a transverse angle to the incoming direction of the article. The innovation will be disclosed in connection with, but not necessarily limited to, a transfer conveyor subsystem in which there are two conveying surfaces which are raised and lowered by a rotary actuator. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings illustrate embodiments of the invention, and, together with specification, including the detailed description which follows, serve to explain the principles of the present invention. 
         FIG. 1  is a perspective view of a conveyor subsystem having a transfer conveyor. 
         FIG. 2  is perspective view of a transfer conveyor constructed in accordance with the teachings of the present invention. 
         FIG. 3  is an exploded perspective view of the transfer conveyor of  FIG. 2 . 
         FIG. 4  is an exploded perspective view of the base assembly of the transfer conveyor of  FIG. 2 . 
         FIG. 5  is an exploded perspective view of the first conveying assembly of the transfer conveyor of  FIG. 2 . 
         FIG. 6  is an exploded perspective view of the second conveying assembly of the transfer conveyor of  FIG. 2 . 
         FIG. 7  is a top plan view of the transfer conveyor of  FIG. 2 . 
         FIG. 8  is a bottom plan view of the transfer conveyor of  FIG. 2 . 
         FIG. 9  is a side view of the transfer conveyor of  FIG. 2  in the direction of line  9 - 9  of  FIG. 7 , the side base frame omitted for clarity showing the conveying surface of the second conveying assembly at a retracted position. 
         FIG. 10  is an enlarged fragmentary side view of the left end of  FIG. 9 . 
         FIG. 11  is an enlarged fragmentary end view taken in the direction of line  11 - 11  of  FIG. 10 . 
         FIG. 12  is a perspective view from the bottom of the transfer conveyor of  FIG. 2  with an end base frame and a side base frame omitted for clarity, showing the cams oriented to locate the conveying surface of the second conveying assembly a retracted position. 
         FIG. 13  is the same side view as  FIG. 9  showing the conveying surfaces of the first conveying assembly and the second conveying assembly at substantially the same height. 
         FIG. 14  is an end view of the transfer conveyor with the end base frame omitted for clarity showing the conveying surfaces of the first conveying assembly and the second conveying assembly at substantially the same height as also shown in  FIG. 13 . 
         FIG. 15  is a perspective view from the bottom of the transfer conveyor of  FIG. 2  with an end base frame and a side base frame omitted for clarity, showing the cams oriented to locate the conveying surfaces of the first conveying assembly and the second conveying assembly at substantially the same height. 
         FIG. 16  is the same side view as  FIG. 9  showing the conveying surface of the first conveying assembly at a lowered position. 
         FIG. 17  is an enlarged fragmentary side view of the left end of  FIG. 16 . 
         FIG. 18  is an enlarged fragmentary end view taken in the direction of line  18 - 18  of  FIG. 17 . 
         FIG. 19  is a perspective view from the bottom of the transfer conveyor of  FIG. 2  with an end base frame and a side base frame omitted for clarity, showing the cams oriented to locate the conveying surface of the first conveying assembly a retracted position. 
         FIG. 20  is an end plan view of a first end of a cam. 
         FIG. 21  is a left side plan view of the cam shown in  FIG. 20 . 
         FIG. 22  is a right side plan view of the cam shown in  FIG. 20 . 
         FIG. 23  is a perspective view of the cam shown in  FIG. 20  from the upper right. 
         FIG. 24  is a perspective view of the cam shown in  FIG. 20  from the upper left. 
         FIG. 25  is a perspective view of the opposite end of the cam shown in  FIG. 20  from the lower right. 
         FIG. 26  is a perspective view of the opposite end of the cam shown in  FIG. 20  from the lower left. 
         FIG. 27  is a top plan view of the cam shown in  FIG. 20 . 
         FIG. 28  is a bottom plan view of the cam shown in  FIG. 20 . 
         FIG. 29  is an end plan view of a first end of another cam. 
         FIG. 30  is a left side plan view of the cam shown in  FIG. 29 . 
         FIG. 31  is a right side plan view of the cam shown in  FIG. 29 . 
         FIG. 32  is a perspective view of the cam shown in  FIG. 29  from the upper right. 
         FIG. 33  is a perspective view of the cam shown in  FIG. 29  from the upper left. 
         FIG. 34  is a perspective view of the opposite end of the cam shown in  FIG. 29  from the lower right. 
         FIG. 35  is a perspective view of the opposite end of the cam shown in  FIG. 29  from the lower left. 
         FIG. 36  is a top plan view of the cam shown in  FIG. 29 . 
         FIG. 37  is a bottom plan view of the cam shown in  FIG. 29 . 
         FIG. 38  diagrammatically shows the first conveying assembly cam track and the second conveying assembly cam track radii as a function of the cam angular position. 
     
    
    
     Reference will now be made in detail to one or more embodiments illustrated in the accompanying drawings. 
     DETAILED DESCRIPTION 
     In the following description, like reference characters designate like or corresponding parts throughout the several views. Also, in the following description, it is to be understood that terms such as front, back, inside, outside, and the like are words of convenience and are not to be construed as limiting terms. Terminology used in this patent is not meant to be limiting insofar as devices described herein, or portions thereof, may be attached or utilized in other orientations. 
     Referring to  FIG. 1 , conveyor subsystem  2  includes a first pair of aligned conveyors  4  and  6  and a second pair of aligned conveyors  8  and  10 . Transfer conveyor  12  is disposed at the intersection of conveyors  4 ,  6 ,  8  and  10 . Each conveyor  4 ,  6 ,  8  and  10  define a respective conveying surface of that conveyor configured to convey an article  14  disposed thereon. In the embodiment depicted, transfer conveyor  12  is configured to direct articles which reach its conveying surface traveling in a first conveying direction, either direction, aligned with arrow  16 . In the embodiment depicted, article  14  is illustrated as moving in the conveying direction of arrow  16 , also referred to as the infeed direction, being discharged from conveyor  4  onto transfer conveyor  12 , and configured to discharge article  14  on to conveyor  6  in the same first conveying direction, indicated by arrow  18 . Transfer conveyor  12  is also configured to selectively discharge articles therefrom in a transverse conveying direction relative to the first direction. In the embodiment depicted, transfer conveyor  12  is configured to discharge articles in a second conveying direction, indicated by arrow  20 , on to conveyor  8 , or in a third conveying direction, indicated by arrow  22 , on to conveyor  10 . In the embodiment depicted, the transverse conveying direction is oriented generally perpendicular to the direction of arrows  16 ,  18 , the infeed direction, but a transfer convey is not limited to the right angle configuration used herein to explain the teachings of the present invention. 
     As used herein, a transverse conveying direction is any direction which is not aligned with the infeed direction. It is noted that two transverse conveying directions, as illustrated in  FIG. 1 , are not required. A transfer conveyor constructed in accordance with the teachings of the present invention may be used in a subsystem having one or more transverse conveying directions. Additionally, it is noted that conveyor  6  may be omitted—transfer conveyor  12  may be used without a discharge direction aligned with the infeed direction: Conveyor subsystem  2  may be configured for transfer conveyor  12  to selectively discharge articles only in one or in more than one transverse conveying directions. When an article is discharged 90° from transfer conveyor  12  in either direction illustrated by arrows  20  and  22 , the transfer is commonly referred to as a right angle transfer. 
     Additionally, either or both conveyors  8 ,  10 , may feed an article onto transfer conveyor  12 , in a direction aligned with but opposite arrows  20 ,  22 , with transfer conveyor  12  discharging the article onto conveyor  4  or  6  (traveling in the appropriate direction for the discharge). This is a merge function, and when conveyors  4 ,  6  are at a 90° angle to conveyors  8 ,  10 , it is commonly referred to as a right angle merge. 
     Referring to  FIGS. 2-6 , transfer conveyor  12  includes base assembly  24 , first conveying assembly  26  and second assembly  28 . Base assembly  24  includes base frame  30  comprising base frame sides  32   a ,  32   b  and base frame ends  34   a ,  34   b , which are connected together, such as by bolting or welding, to form base frame  30 . Base frame side  32   a  includes a plurality of spaced apart slots  36   a  which align with spaced apart slots  36   b  of base frame side  32   b . Each base frame side  32   a ,  32   b , includes a respective pair of spaced apart guides  38   a ,  40   a  (not seen) and  38   b ,  40   b , made of any suitable material, such as UHMW polyethylene. Base assembly carries two spaced apart generally parallel rotary actuators  42 ,  44 . In the embodiment depicted, actuators  42 ,  44  are illustrated as rollers and will also be referred to herein as roller  42  and roller  44 , it being understood that rotary actuators  42 ,  44  are not limited to the roller illustrated. A pair of spaced apart cams  46   a ,  46   b  are carried by roller  42 , rotating therewith. Similarly, a pair of spaced apart cams  48   a ,  48   b  are carried by roller  44 , rotating therewith. The cam tracks (described below) of cams  46   a  and  48   a  are identical to and rotationally aligned with each other. The cam tracks (described below) of cams  46   b  and  48   b  are identical to and rotationally aligned with each other. The cam tracks (described below) of cams  46   a ,  48   a  have mirror image symmetry with cams  46   b ,  48   b . Synchronizing drive pulleys  50 ,  52  are non-rotatably carried by rollers  42 ,  44 , respectively at ends  42   a ,  44   a . Synchronizing drive belt  54  extends between and around synchronizing drive pulleys  50 ,  52 . 
     In the depicted embodiment, roller  44  is a motorized drive roller (MDR) which may be controlled to rotate in either direction through an total rotational angle consistent with the configuration of cams  46   a ,  46   b ,  48   a ,  48   b , in the embodiment depicted, less than 360° of total rotation. Synchronizing drive belt  54  drives roller  42  without slippage to maintain the relative angular position between cams  46   a ,  46   b  and cams  48   a ,  48   b . Synchronizing drive pulleys  50 ,  52 , and synchronizing drive belt  54  may include features which resist or prevent slippage therebetween, such as external ridges or teeth on synchronizing drive pulleys  50 ,  52 , and internal ridges or teeth on synchronizing drive belt  54 . Any suitable drive mechanism may be used, disposed to synchronously raise and lower the conveying surfaces  120 ,  122  (see  FIG. 9 ) of first conveying assembly  26  and second conveying assembly  28 , respectively, which is effected in the embodiment depicted through rotation of cams  46   a ,  46   b ,  48   a ,  48   b . For example, synchronizing belt  54  and synchronizing pulleys  50 ,  52 , may be omitted by configuring drive roller  42  as an MDR, and controlling it so as to synchronize the relative angular positions of cams  46 , a ,  46   b ,  48   a ,  48   b.    
     As illustrated in  FIG. 5 , first conveying assembly  26  includes side frames  56   a ,  56   b  which are secured to each other in a spaced apart relationship by end frames  58   a ,  60   a ,  58   b ,  60   b . Side frame  56   a  includes a plurality of spaced apart slots  62   a  which align with spaced apart slots  62   b  of side frame  56   b . Side frame  56   a  includes a plurality of spaced apart slots  64   a  which align with spaced apart slots  64   b  of side frame  56   b.    
     First conveying assembly  26  comprises a plurality of spaced apart conveying elements, illustrated as rotatable rollers  66 , having respective axels  66   d  which may be disposed into respective slots  64   a ,  64   b . The upper tangent edges of rollers  66  define the conveying surface of first conveying assembly  26 . Axles  66   d  may be spring loaded and capable of being depressed into rollers  66 , or may be fixed. 
     In the embodiment depicted, rollers  66  are powered, driven by a single MDR roller  66   c  which may be disposed near the middle of first conveying assembly  26 . In the embodiment depicted, each roller  66  includes a respective pair of spaced apart annular grooves  68 ,  70 , which are generally aligned. Aligned with groves  70  is a plurality of rotatable idler pulleys  72  which are attached to side frame  56   a  by fasteners engaging holes  74  and vertical slots  76 . Although holes  74  and vertical slots  76  of side frame  56   a  are not visible, reference is made to the corresponding numbered features of side frame  56   b , which because of commonality of components is identical to side frame  56   a . Vertical slots  76  allow the position of those idler pulleys to be adjusted vertically. 
     Drive belt  78  is circuitously routed in a serpentine path engaging each roller  66  in grooves  70  and each idler pulley  72 . Vertical adjustment of each idler pulley  72  allows tension and slack in drive belt  78  to be adjusted. In the embodiment depicted, drive belt  78  is a flat belt, accommodating the reverse bending around rollers  66  and idler pulleys  72 . Because grooves in rollers typically have a rounded profile, a band (not shown) may be disposed in each groove  70  to present a crowned profile more suitable for flat drive belt  78 . In the embodiment depicted, rollers  66   a  and  66   b  are driven by but not directly engaged by drive belt  78 . Roller  66   a  is driven by the adjacent roller  66  through drive element  80   a  disposed in grooves  68   a ,  68  of the respective rollers  66 ,  66   a . Similarly, roller  66   b  is driven by its adjacent roller  66  through drive element  80   b  disposed in groves  68   b ,  68  of the respective rollers  66 ,  66   b . Drive elements  80   a ,  80   b  may be O-belts, as is known. Although in the embodiment depicted, all rollers  66  are driven, the practice of the present invention is not so limited. One or more rollers  66  may be non driven idler rollers. Additionally, the present invention is not limited to the use of a MDR to drive rollers  66 . Any suitable drive configuration and mechanism may be used a as the source of rotational power to drive rollers  66 , which may or may not move vertically with first conveying assembly  26 . 
     Transfer conveyor  12  would typically be oriented such that conveying direction of rollers  66  is in alignment with the primary infeed direction, arrow  16  in  FIG. 1 . Thusly, roller  66   c  would be configured to drive rollers  66  to advance articles in the downstream conveying direction in the direction of arrows  16  and  18 . Rollers  66  could be configured to rotate in either direction, such as in a configuration in which transfer conveyor  12  is oriented in such that the conveying direction of rollers  66  is transverse to the primary infeed direction. 
     First conveying assembly  26  is vertically moveably supported by two pairs of spaced apart rotatable cam followers  82   a ,  82   b  and  84   a ,  84   b , respectively carried by side frames  56   a ,  56   b . Cam followers  82   a ,  82   b ,  84   a ,  84   b  are in engagement with cams  46   a ,  46   b ,  48   a ,  48   b  in a manner which will be described below. Alternately, cam followers  82   a ,  82   b  and  84   a ,  84   b  may be configured not to rotate, such as being configured to slide along the cam tracks described below. 
     Referring to  FIG. 6 , second conveying assembly  28  includes frame  86  having spaced apart side frame portions  88   a ,  88   b  and spaced apart end frame portions  90   a ,  90   b . Side frame portion  88   a  includes a plurality of spaced apart pairs of slots  92   a  which align with spaced apart pairs of slots  92   b  of side frame portion  88   b . Frame  86  carries two spaced apart pairs of spaced apart guides  94   a ,  94   b  and  96   a ,  96   b . In the embodiment depicted, guides  94   a , 94   b ,  96   a ,  96   b  are respectively carried by the horizontal portion of frame  86  proximal to the corners formed by side frame portions  88   a ,  88   b  and end frame portions  90   a ,  90   b . Alternately, guides  94   a ,  94   b ,  96   a ,  96   b  could be respectively carried on the vertical flanges of end frame portions  90   a ,  90   b . Guides  94   a ,  94   b ,  96   a ,  96   b  extend past the edge of side frame portions  88   a ,  88   b , respectively, and may be adjustable outwardly/inwardly. Guides  94   a ,  94   b ,  96   a ,  96   b  may be made of any suitable material, such as UHMW polyethylene. 
     Second conveying assembly  28  includes a drive element, illustrated as roller  98 , rotatably supported at each end by end frame portions  90   a ,  90   b . In the embodiment depicted, drive roller  98  is a MDR. Drive roller  98  includes sleeve  100  having a plurality of external teeth or ribs, configured to positively engage and drive belts  108  as described below. In the embodiment depicted, sleeve  100  is an aluminum extrusion affixed to drive roller  98 . The present invention is not limited to the use of an MDR with second conveying assembly  28 . Any suitable drive configuration and mechanism may be used, which may or may not move vertically with second conveying assembly  28 . 
     Second conveying assembly  28  is vertically moveably supported by two pairs of spaced apart rotatable cam followers  102   a ,  102   b  and  104   a ,  104   b , respectively carried by end frame portions  90   a ,  90   b . Cam followers  102   a ,  102   b ,  104   a ,  104   b  are in engagement with cams  46   a ,  46   b ,  48   a ,  48   b  in a manner which will be described below. 
     Second conveying assembly  28  includes a plurality of spaced apart cartridges  106  which comprise respective conveying elements, illustrated as belts  108  supported by a plurality of rotatable pulleys  110  (see  FIG. 8 ) respectively carried by assembly frames  112   a ,  112   b , held together by fasteners  114 , which define the axes of rotation for rotatable pulleys  110 . Each assembly frame  112   a ,  112   b , includes a pair of spaced apart tabs  116   a ,  116   b  which, during assembly, may be inserted into engagement with respective slots  92   a ,  92   b . To retain tabs  116   a ,  116   b  in slots  92   a ,  92   b , a retainer (not shown) may be disposed adjacent cartridges  106 , secured to frame  86  so as to prevent tabs  116   b  from being disengaged from slots  92   a ,  92   b . The upper runs of belts  108  collectively define the conveying surface  122  of second conveying assembly  28 . 
     Cartridges  106  are interposed between rollers  66 , and may be individually removed or inserted into second conveying assembly  28  while rollers  66  are in place, by accessing the retainer from above, moving the retainer away, and withdrawing the cartridge  106 . Drive roller  98  externally engages belts  108 . In the embodiment depicted, drive roller positively engages belts  108  in the area indicated at  118  through external teeth on belts  108 . Belts  108  may be driven using any suitable configuration. For example, belts  108  may have a non-toothed exterior surface and frictionally engage drive roller  98 . This external engagement between cartridges  106  and drive roller  98  permits cartridges  106  to be removed or inserted without removal, disassembly or adjustment of drive roller  98 . 
     Transfer conveyor  12  would typically be oriented such that conveying direction of travel of belts  108  is in alignment with second direction arrow  20  or third direction arrow  22 . Drive roller  98  is configured to rotate in either direction so as to drive belts  108  to receive articles from conveyor  8  or  10  or to discharge articles from transfer conveyor  12  onto conveyor  8 , in either direction aligned with arrow  20 , or to discharge articles onto conveyor  10  in the direction of arrow  22 . 
     The top and bottom of transfer conveyor  12  are presented in  FIGS. 7 and 8 , illustrating the arrangement of base assembly  24 , first conveying assembly  26  and second conveying assembly  28 . Guides  38   a ,  40   a  are disposed between base frame side  32   a  and side frame  56   a , and guides  38   b ,  40   b  are disposed between base frame side  32   b  and side frame  56   b , functioning to locate first conveying assembly  26  relative to base frame sides  32   a ,  32   b  and allow the vertical movement effected by cams  46   a ,  46   b ,  48   a ,  48   b , as described below. Guides  94   a ,  96   a  extend between frame  86  and side frame  56   a , and guides  94   b ,  96   b  extend between frame  86  and side frame  56   b , functioning to locate second conveying assembly  28  relative to side frames  56   a ,  56   b  and allow the vertical movement effected by cams  46   a ,  46   b ,  48   a ,  48   b , as described below. 
     First conveying assembly  26  and second conveying assembly  28  are vertically movable, making their respective conveying surfaces vertically moveable. The vertical movements of first conveying assembly  26  and second conveying assembly  28  is effected by rotation of rotatable cams  46   a ,  46   b ,  48   a ,  48   b . Referring to  FIGS. 9-11 , conveying surface  120  of first conveying assembly  26  is disposed at its conveying height —the height at which it is disposed when conveying articles. In the embodiment depicted, it is the maximum height at which conveying surface  120  can be disposed, which substantially matches the height of the conveying surfaces of conveyors  4 ,  6 ,  8  and  10 . Conveying surface  122  of second conveying assembly  28  is disposed below the height of conveying surface  120 , at its lowest height, at which it will not make substantive contact with articles on conveying surface  120 . For these positions of conveying surfaces  120 ,  122 , articles may be conveyed in the conveying direction of rollers  66 , either direction aligned with arrow  16 . 
     Referring to  FIGS. 9 - 12  and  FIGS. 20 - 27 , which illustrate the configuration of cam  46   a  from different angles, the interaction of cam  46   a  and cam followers  84   a  and  104   a  can be seen. The engagement between and function of cams  46   b ,  48   a ,  48   b  with respective cam followers  82   a ,  82   b ,  84   b ,  102   a ,  102   b  and  104   b  are the same, taking into account the minor image symmetry between cams  46   a  and  46   b  and cams  48   a  and  48   b . Cam  46   a  includes circumferential first conveying assembly cam track  46   a - r  and circumferential second conveying assembly cam track  46   a - t  disposed on opposite sides of cam  46   a . Interposed between cam track  46   a - r  and  46   a - t , are respective flanges  46   a - rf and  46   a - tf . As seen in  FIGS. 20-22 , cam track  46   a - t  extends circumferentially about cam  46   a  having a generally constant radius from point  124  to point  126 , and has a decreasing radius from point  126  to point  128 . Similarly, flange  46   a - tf  extends circumferentially about cam  46   a  having a generally constant radius from point  130  to point  132 , and has a decreasing radius from point  132  to point  134 . The difference in corresponding radii between cam track  46   a - t  and associated flange  46   a - tf  provides clearance for the head of the fastener holding cam follower  84   a  to side frame  56   b . As seen in  FIG. 10 , second conveying assembly cam track  46   a - t  is on side  136  of cam  46   a  and first conveying assembly cam track  46   a - r  is on side  138  of cam  46   a . Flange  46   a - rf  and the corresponding flange on cam  46   b , flange  46   b - rf , cooperate to maintain cam followers  84   a  and  84   b  therebetween, limiting the horizontal movement of first conveying assembly  26 . It is noted that cam  48   a  is identical to cam  46   a .  FIG. 11  illustrates cam  48   a and its relationship with cam followers  82   a ,  102   a  matching the relationship of cam  46   a with cam followers  84   a ,  104   a  shown in  FIG. 10 . 
     Roller  42 , which functions with drive roller  44  as an actuator to effect the positioning of conveying surfaces  120 ,  122 , is disposed at an angular position in  FIGS. 9-12  at which cam  46   a  (and concomitantly cams  46   b ,  48   a  and  48   b ) is oriented so as to position conveying surface  120  at its conveying height and position conveying surface  122  at a retracted height. In  FIG. 10 , the radius of first conveying assembly cam track  46   a - r  adjacent cam follower  84   a  at  140  is at its maximum and the radius of second conveying assembly cam track  46   a - t  adjacent cam follower  104   a  at  142  is at its minimum.  FIG. 11  shows an end view of cam  48   a , which is in the same angular orientation as cam  46   a  as a result of the synchronized motion therebetween. Cam follower  102   a  is adjacent second conveying assembly cam track  48   a - t , at its minimum radius. 
     In  FIGS. 13-15 , cams  46   a ,  46   b ,  48   a ,  48   b  are disposed at an intermediate position, the midpoint of the their range of angular rotation. The radii of first conveying assembly cam tracks  46   a - r ,  46   b - r ,  48   a - r ,  48   b - r  adjacent cam followers  82   a ,  82   b ,  84   a ,  84   b  are at their maximum and the radii of second conveying assembly cam tracks  46   a - t ,  46   b - t ,  48   a - t ,  48   b - t  adjacent cam followers  102   a ,  102   b ,  104   a ,  104   b  are at their maximum. This locates both conveying surface  120  at its conveying height and conveying surface  122  its conveying heights, co-incident with each other. 
     Alternatively, the conveying height of conveying surface  122  could be set to be slightly below the conveying height of conveying surface  120 , with second conveying assembly cam track  46   a - t ,  46   b - t ,  48   a - t ,  48   b - t  could be correspondingly configured, such that as first conveying assembly  26  is lowered through rotation of cams  46   a ,  46   b ,  48   a ,  48   b , articles on first conveying surface  120  are slightly lowered on to conveying surface  122  to be discharged by second conveying assembly  28 . 
     Referring to  FIGS. 16 - 19 , roller  42  is disposed at an angular position in  FIGS. 14-16  at which cam  46   a  (and concomitantly cams  46   b ,  48   a  and  48   b ) is oriented so as to position conveying surface  122  at its conveying height and position conveying surface  120  at a retracted height. In  FIG. 17 , the radius of first conveying assembly cam track  46   a - r adjacent cam follower  84   a  at  140  is at its minimum and the radius of second conveying assembly cam track  46   a - t  adjacent cam follower  104   a  at  142  is at its maximum.  FIG. 18  shows an end view of cam  48   a  in this same angular orientation. Cam follower  102   a  is adjacent second conveying assembly cam track  48   a - t , at its maximum radius. 
     In use, an article is received by transfer conveyor  12 , conveyed along conveying surface  12  by rollers  66  at its conveying height, with second conveying assembly  28  at its retracted height, as seen in  FIGS. 9-11 . If the article is to be conveyed in a direction which is disposed at a transverse angle to the incoming direction of the article, i.e., in the conveying direction of second conveying assembly  28 , driving of rollers  66  ceases when the article is at the desired position, with rollers  66  thereafter being free to coast. Roller  42  and drive roller  44  may be actuated at any appropriate time by causing drive roller  44  to rotate, based on the location of an article in anticipation of transferring that article, such as prior to ceasing to drive rollers  6 . As cams  46   a ,  46   b ,  48   a ,  48   b  rotate, first conveying surface  120  remains at its conveying height through the initial rotation because the radii of first conveying assembly cam tracks  46   a - r ,  46   b - r ,  48   a - r  and  48   b - r  are constant at their maximum. As cams  46   a ,  46   b ,  48   a ,  48   b  are rotated, the radii of second conveying assembly cam tracks  46   a - t ,  46   b - t ,  48   a - t  and  48   b - t  increases up to their maximum, thereby raising second conveying assembly  28  and locating second conveying assembly conveying surface  122  co-incident with first conveying surface  120 , such that the article is engaged by rollers  66  and belts  108 , decelerating the article. As cams  46   a ,  46   b ,  48   a  and  48   b  rotate further, the radii of second conveying assembly cam tracks  46   a - t ,  46   b - t ,  48   a - t  and  48   b - t  remains constant at their maximum, maintaining second conveying surface  122  at its conveying height, and the radii of first conveying assembly cam tracks  46   a - r ,  46   b - r ,  48   a - r  and  48   b - r  decrease lowering first conveying assembly  26  to a retracted position out of contact with the article. At the appropriate time, such as as soon as rollers  66  begin being lowered, belts  108  may be driven to advance in the desired direction so as to discharge the article in the desired transverse direction. 
     Referring to  FIGS. 29-37 , cam  46   b  is illustrated, which identical to cam  48   b , both of which are a mirror image of cam  46   a . Cam  46   b  includes circumferential first conveying assembly cam track  46   b - r  and circumferential second conveying assembly cam track  46   b - t  disposed on opposite sides of cam  46   b . Interposed between cam track  46   b - r  and  46   b - t , are respective flanges  46   b - rf  and  46   b - tf . As seen in  FIGS. 29-31 , cam track  46   b - t  extends circumferentially about cam  46   b  having a generally constant radius from point  144  to point  146 , and has a decreasing radius from point  146  to point  148 . Similarly, flange  46   b - tf  extends circumferentially about cam  46   b  having a generally constant radius from point  150  to point  152 , and has a decreasing radius from point  152  to point  154 . The difference in corresponding radii between cam track  46   b - t  and associated flange  46   b - tf  is substantially constant. 
     In  FIG. 38 , line  160  diagrammatically represents the radius of the first conveying assembly cam tracks and line  162  diagrammatically represents the radius of the second conveying assembly cam tracks plotted against the cam angular position. Zero degrees represents the position of the cams when both conveying surfaces  120  and  122  are both at their conveying height, co-incident with each other. In the embodiment depicted, cams  46   a ,  46   b ,  48   a ,  48   b  have less than 360° of rotation between the conveying height position of first conveying assembly  26  and the conveying height position of second conveying assembly  28 . In  FIG. 38 , at less than −180° of rotation from the 0° position, the first conveying assembly cam track radius is at its maximum and the second conveying assembly cam track radius is at its minimum. Similarly, at less than 180° of rotation from the 0° position, the second conveying assembly cam track radius is at its maximum and the first conveying assembly cam track radius is at its minimum. Although the profile of the change in radii of the first conveying assembly cam track and the second conveying assembly cam track is diagrammatically illustrated as linear, any suitable profile may be used, such as a non-linear profile. 
     In the embodiment depicted, there are four spaced apart cams  46   a ,  46   b ,  48   a ,  48   b , each with two respective cam tracks for the first conveying assembly and the second conveying assembly, producing through rotational cam action independent vertical movement of the first and second conveying surfaces from a respective conveying height to a retracted height. Fewer or more cams or other structures may be used to produce the same interdependent vertical movement through rotational motion. For example, a single cam or a single pair of cams could be used. 
     The foregoing description has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed. Obvious modifications or variations are possible in light of the above teachings. The embodiment was chosen and described in order to illustrate the principles of the invention and its application to thereby enable one of ordinary skill in the art to utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated. Although only a limited number of embodiments is explained in detail, it is to be understood that the invention is not limited in its scope to the details of construction and arrangement of components set forth in the preceding description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced or carried out in various ways. Also, specific terminology was used herein for the sake of clarity. It is to be understood that each specific term includes all technical equivalents which operate in a similar manner to accomplish a similar purpose. It is intended that the scope of the invention be defined by the claims submitted herewith.