Abstract:
An article pusher assembly for use with a roller conveyor having a plurality of parallel rollers that define a conveying surface having opposed sides at a given distance. The pusher assembly comprises a carriage assembly mounted under the conveying surface. The carriage assembly includes first and second carriages. A pusher blade is positioned with a contact portion above the conveying surface and at least one post extending between a pair of adjacent rollers and connected to the one of the carriages. A drive unit is mounted under the conveying surface selectively drives the carriage assembly. A multiplier unit interconnects the first and second carriages and is configured to move the first carriage relative to the second carriage in direct relation to movement of the second carriage.

Description:
BACKGROUND 
     The present invention relates to conveyor pushers. More particularly, the present invention relates to a pusher assembly mounted on the underside of a roller conveyor. 
     Package delivery companies pick up millions of packages daily from thousands of locations over a large geographical area and transport them to sorting facilities, primarily by truck and airplane, so they can be routed to a correspondingly large number of scattered destinations. To meet a rigorous schedule and provide accurate deliveries, a package delivery company must use automated transfer systems in the sorting facilities to match incoming packages with proper outgoing transport headed for the packages&#39; destinations. Because deliveries are time sensitive, the sorting equipment must be very fast, yet provide gentle and accurate handling of packages. 
     Belt and roller conveyor systems have often been used in package sorting systems to move packages from incoming loading docks to outgoing transport. An initial sorting of packages traveling along a conveyor may be accomplished by diverting packages from the conveyor based on their destinations, or based on their size or another characteristic. 
     To automate handling of articles traveling on conveyor systems, conveyor diverter assemblies of various types have been developed. Several systems have been developed to push articles off conveyors with pushing arms that sweep directly across the conveyors. Examples of such systems are shown in U.S. Pat. Nos. 3,026,988, 4,295,559, and 4,732,260. These pushers generally mount over or on the side of the conveyor. The pushers also often require special guarding to protect operators from the moving pusher. Both of these characteristics generally limit access to the conveyor. 
     SUMMARY 
     The present invention relates to an article pusher assembly for use with a roller conveyor having a plurality of parallel rollers that define a conveying surface having opposed sides at a given distance. The pusher assembly generally comprises a carriage assembly adapted to be mounted under the conveying surface. A pusher blade is adapted to be positioned such that a portion thereof is generally above the conveying surface and at least one portion extends between a pair of adjacent rollers and connects to the carriage assembly. A drive unit is adapted to be mounted under the conveying surface and to selectively drive the carriage assembly. 
     The carriage assembly preferably includes first and second carriages. A multiplier unit interconnects the first and second carriages and is configured to move the first carriage relative to the second carriage in direct relation to movement of the second carriage. The preferred carriage assembly further includes a biasing member positioned between the carriage and the pusher blade such that the pusher blade is generally maintained in, but deflectable from, a plane parallel to the conveying surface. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an isometric view of a roller conveyor assembly incorporating a pusher assembly according to a first embodiment of the present invention. 
     FIG. 2 is a cross sectional view along line  2 — 2  in FIG.  1 . 
     FIGS. 3 and 4 are side and top, respectively, schematics illustrating the pusher assembly in a home position. 
     FIGS. 5 and 6 are side and top, respectively, schematics illustrating the pusher assembly moving across the conveyor. 
     FIGS. 7 and 8 are side and top, respectively, schematics illustrating the pusher assembly in an extended position. 
     FIG. 9 is a side schematic illustrating the pusher assembly in the home position and the extended position (in phantom). 
     FIGS. 10 and 11 are side schematics illustrating deflection of the preferred pusher assembly as it returns to the home position. 
     FIG. 12 is a cross sectional view similar to FIG. 2 illustrating a second embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The present invention will be described with reference to the accompanying drawing figures wherein like numbers represent like elements throughout. Certain terminology, for example, “top”, “bottom”, “right”, “left”, “front”, “frontward”, “forward”, “back”, “rear” and “rearward”, is used in the following description for relative descriptive clarity only and is not intended to be limiting. 
     A preferred embodiment of the present invention will be described with reference to FIGS. 1-9. Referring specifically to FIGS. 1 and 2, the pusher assembly  20  of the preferred embodiment is shown positioned relative to a roller conveyor  10 . The roller conveyor  10  generally comprises a plurality of parallel rollers  12  supported between opposed frame members  16  and  18 . There is an open space  14  between each pair of adjacent rollers  12 . Articles (not shown) generally travel along the conveyor  10  in the direction of arrow A in FIG.  1 . 
     The pusher assembly  20  generally comprises a pusher blade  30 , a carriage assembly  40  and a drive unit  80 . The pusher blade  30  includes a contact surface  32  that is supported above the conveyor rollers  12  by a pair of posts  34 . The contact surface  32  is configured to sit slightly above the conveyor rollers  12  and to move across the conveyor  10  to divert articles substantially perpendicular to the direction of travel A of the conveyor  10 . 
     The carriage assembly  40  will be described with reference to FIGS. 2-9. The carriage assembly  40  includes a base frame  42  and  43  fixed under the conveyor  10  between the conveyor frame members  16  and  18 . In the illustrated embodiment, the base frame member  42  extends from frame member  16  to the approximate midpoint of the conveyor  10  and member  43  extends from frame member  16  to the opposed frame member  18 , but the base frame  42  and  43  may be cantilevered or may otherwise be supported under the conveyor  10 . 
     An inner carriage  44  is configured to fit about and ride along the base frame member  42 . Roller bearings  50  or the like may be positioned between the base frame member  42  and the inner carriage  44  to facilitate smooth, relative movement therebetween. An outer carriage  46  is configured to fit about and ride along the inner carriage  44 . Again, roller bearings  52  or the like may be positioned between the inner carriage  44  and the outer carriage  46  to facilitate smooth, relative movement therebetween. 
     A pusher blade support bracket  54  is attached to and moves with the outer carriage  46 . The pusher blade posts  34  extend through the spaces  14  between rollers  12  and are pivotally connected to the support bracket  54  at pivot points  56 . A biasing element  60 , for example a coil or torsion spring, extends between the bracket  54  and an arm  58  extending from each post  34 . The biasing elements  60  maintain the posts  34 , and thereby the contact surface  32 , in a default position substantially perpendicular to the conveyor  10  surface. The biasing elements  60  however allow the pusher blade  30  to deflect in the event the blade  30  makes undesired contact with an object, as will be described hereinafter. 
     The carriage assembly  40  is driven by a drive unit  80  positioned within the base frame member  42 . The drive unit  80  illustrated in FIG. 2 includes a fluid cylinder  82 , for example, a pneumatic cylinder, that extends and retracts in response to signals from control circuitry  84 . The cylinder rod of the fluid cylinder  82  is associated with the inner carriage  44  such that extension and retraction of the cylinder rod moves the inner carriage  44  across the conveyor  10 . 
     A multiplier unit  68  extends between the inner carriage  44  and the outer carriage  46 . The preferred multiplier unit  68  preferably includes a pair of wheels  70  extending from each side of the inner carriage  44 . A tensioned band  72 , for example, timing belt or link band, extends between the wheels  70  on each side of the inner carriage  44 . Referring to FIGS. 3-8, the wheels  70  move along with the inner carriage  44 . A set point  74  fixes each band  72  to the base frame member  43 . The outer carriage  46  includes a pair of outwardly extending flanges  48  that are attached to the respective bands  72 . As the inner frame  44  is driven across the conveyor  10  and the wheels  70  move therewith, the bands  72  are also driven. Since the bands  72  are fixed to the base frame member  43  and also attached to the free outer carriage  46 , the driven bands  72  cause the outer carriage  46  to move relative to the inner carriage  44 . 
     As illustrated in FIG. 9, as the inner carriage  44  moves from the home position to the extended position (in phantom), the inner carriage  44  moves a distance D 1  approximately half the distance of the conveyor  10 . As the inner carriage  44  moves the distance D 1 , the multiplier unit  68  causes the outer carriage  46  to move with and relative to the inner carriage  44 , such that the outer carriage  46 , and thereby the pusher blade  30 , moves a greater distance D 2 , substantially completely across the conveyor  10 . 
     Referring to FIGS. 10 and 11, deflection of the pusher blade  30  will be described. In the preferred embodiment, the support bracket  54  is L-shaped such that the posts  34  are prevented from rotating backward, thereby defining the limit position of the pusher blade  30 . The pusher blade  30  can thereby push desired articles placed in front of the contact surface  32 . However, as the pusher blade  30  returns to the home position, if an object  100 , for example, an operators hand, is inadvertently positioned behind the pusher blade  30 , the biasing members  60  allow the pusher assembly  30  to deflect forward as illustrated in FIG.  11 . The biasing force of the biasing members  60  is preferably chosen to withstand the inertial force created against the blade  30  as it returns to the home position, but otherwise easily deflects to minimize the impact of the blade  30  against the object  100 . Holes (not shown) may be provided in the contact surface  32  to reduce the return inertial force and further minimize the necessary biasing force. 
     As shown in FIGS. 2 and 10, the contact surface  32  is preferably spaced a slight distance d from the top of the conveyor rollers  12  to allow sufficient clearance for the pusher blade  30  to deflect. Referring to FIG. 12, detents  36  aligned with the rollers  12  may be provided along the lower edge of the contact surface  32  to further accommodate deflection of the pusher blade  30 . 
     In addition to deflecting as the pusher blade  30  moves backward, the pusher assembly  20  may also be configured to deflect if an over weight object or the like is placed in front of the contact surface  32 . For example, the support bracket  54  may be configured to allow rotation of the posts  34  both forward and backward. Support springs (not shown) can be provided to prevent reward rotation of the posts  34 . The support springs will have a biasing force equal to the maximum weight to be pushed by the pusher assembly  20 , for example, a biasing force equal to 150 pounds. 
     An alternative embodiment of the present invention is illustrated in FIG.  12 . The pusher assembly  20 ′ includes a pusher blade  30 , a carriage assembly  40 ′ and a drive unit  80 . The pusher blade  30  is substantially the same as the pusher blade  30  in the above embodiment. The carriage assembly  40 ′ is substantially the same as in the previous embodiment, except that the outer carriage  46 ′ has an open configuration. Accordingly, the multiplier unit  68 ′ is only provided on one side of the inner carriage  44 . The drive unit  80  includes a ball lead screw  90  in place of the fluid cylinder. The ball lead screw  90  includes a linear screw  94  driven by an electric motor (not shown) or the like. The ball nut  92  positioned about the screw  94  is associated with the inner carriage  44  such that rotation of the screw  94  extends and retracts the inner carriage  44 . 
     While the invention has been illustrated and described in detail in the drawings and foregoing description, the same is considered as illustrative and not restrictive in character, it being understood that only preferred embodiments have been shown and described and that there are many changes and modifications that come within the spirit of the invention.