Abstract:
A conveyor system and methods for conveying and unstacking flat and non-flat packages. The conveyor system includes an inclined conveyor belt delivering packages to a tilted conveyor belt that conveys flat packages along its length while non-flat packages tumble off its lower side edge to initially cull flat packages from a bulk flow of packages. Retention means, such as a high-friction outer conveying surface or a raised barrier along the length of the outer conveying surface of the tilted conveyor belt, holds flat packages on the tilted conveyor belt. The inclined conveyor belt has stop elements spaced apart along the belt&#39;s length and is advanced in stop-and-go fashion to help unstack piggy-backed packages as they are conveyed up the incline. The initially separated packages are more fully culled in a conveyor comprising a roller conveyor belt with package-supporting belt rollers rotated in a direction to push packages sidewise toward a culling element that extends along the length of the roller conveyor belt.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a divisional patent application of co-pending U.S. patent application Ser. No. 13/040,919, filed Mar. 4, 2011, which claims the priority of U.S. provisional patent application Ser. No. 61/311,610, “Package-Culling Conveyor System and Method,” filed Mar. 8, 2010. Both prior applications are incorporated into this application by reference. 
     
    
     BACKGROUND 
       [0002]    The application relates generally to power-driven conveyors and more particularly to conveyor systems and associated methods for using conveyor belts to unstack and separate a bulk supply of flat packages and non-flat packages. 
         [0003]    In the postal and parcel industries, envelopes are culled from a bulk flow of packages that include envelopes, boxes, tubes, and other mail. Typically, the culling is performed by postal workers who manually pluck envelopes from a mass flow of packages. This work is labor intensive. 
       SUMMARY 
       [0004]    One version of a conveyor embodying features of the invention comprises a tilted conveyor belt having an outer conveying surface that extends in width from an elevated side edge to a lower side edge. The tilted conveyor belt advances in a direction of belt travel parallel to the elevated and lower side edges. Its outer conveying surface is tilted at a tilt angle off horizontal sufficient for non-flat packages received on the outer conveying surface to tumble downward across the width of the conveyor belt and over the lower side edge. The tilted conveyor belt further comprises retention means to prevent flat packages from sliding on their bottoms across the width of the outer conveying surface of the conveyor belt and over the lower side edge. The retention means may be realized by a high-friction outer conveying surface or by a raised barrier extending along the length of the outer conveying surface. 
         [0005]    In another aspect of the invention, a method for culling flat packages from a bulk flow of flat and non-flat packages, comprises: (a) feeding a batch of packages onto a tilted conveyor belt advancing in a direction of belt travel; (b) operating the tilted conveyor belt tilted off horizontal enough to allow non-flat packages to tumble across the tilted conveyor belt and off its lower side edge; and (c) retaining flat packages on the tilted conveyor belt to convey the flat packages in the direction of belt travel. 
         [0006]    In yet another aspect of the invention, a conveyor comprises a conveyor belt having a conveying surface advancing up an incline from a lower end to an upper end. Stop elements extend across the width of the conveying surface of the conveyor belt at spaced apart locations along the belt&#39;s length. The conveyor belt advances up the incline with a continuous stop-and-start pulsing motion. 
         [0007]    In another aspect of the invention, a method for unstacking packages being conveyed up an incline comprises (a) arranging a conveyor belt having spaced apart stop elements extending across the width of the conveying surface at spaced apart locations along the length of the conveyor belt on an incline from a lower end to an upper end; (b) advancing the conveyor belt up the incline in a stop-and-go pulsing motion to slide packages stacked atop other packages down the conveyor belt; and (c) stopping the slide of the previously stacked packages with the stop elements. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]    These features and aspects of the invention, as well as its advantages, are described in more detail in the following description, appended claims, and accompanying drawings, in which: 
           [0009]      FIG. 1  is a top plan schematic of a portion of a package-culling conveyor system embodying features of the invention; 
           [0010]      FIG. 2  is a side elevation schematic of the portion of the conveyor system shown in  FIG. 1 ; 
           [0011]      FIG. 3  is a top plan schematic of a culling conveyor belt usable in the conveyor system of  FIG. 1 ; 
           [0012]      FIG. 4  is a front elevation schematic of a portion of the culling conveyor of  FIG. 3  showing a powered roller lifting non-flat packages off flat packages; 
           [0013]      FIG. 5  is a front elevation schematic as in  FIG. 4 , showing the powered roller with a guard and rollers in the conveyor belt passing flat packages under the guard; 
           [0014]      FIG. 6  is a front elevation schematic as in  FIG. 5  with powered ejection rollers to help pull flat packages from under a stack; and 
           [0015]      FIG. 7  is an oblique view of another version of a culling conveyor as in  FIG. 3 , embodying features of the invention, including a side rail, rather than a powered roller, used as a culling element. 
       
    
    
     DETAILED DESCRIPTION 
       [0016]    A conveyor system for culling flat packages from a bulk supply of packages to separate flat packages from non-flat packages is shown in  FIGS. 1-3 . As used in this description, the term “flat packages” refers to envelopes and other packages that have a small thickness; the term “non-flat packages” refers to packages, such as boxes and tubes that are not “flat packages.” A bulk supply of packages P from which flat packages are to be culled is dumped on an infeed conveyor  10 . The infeed conveyor may be realized as a belt conveyor having a belt  12 , which may be a flat belt or a flat-top modular plastic conveyor belt. The belt conveys the packages in bulk in a conveying direction  14  to an incline conveyor  16 . 
         [0017]    The incline conveyor shown is an inclined conveyor belt  18  having stop elements  20 , such as short flights, extending across the width of the belt at regular intervals along its length. The stop elements may extend across the entire width as shown or may extend across half the width staggered from the left-side half to the right-side half of the belt. The stop elements divide the conveying surface of the inclined belt  18  into bins  22 , each containing a batch of packages received from the bulk flow supplied by the infeed conveyor. The incline conveyor is inclined off horizontal at an inclination angle a that is sufficient to allow larger non-flat packages and even flat packages at the top of a stack to tumble or slide backward until they reach the stop elements. The inclined conveyor belt  18  advances up the incline with a continuous start-and-stop motion. The jerky, pulsing motion of the belt also helps in the unstacking and unshingling of stacked packages. Rubber or other high-friction pads or areas on the inclined belt&#39;s conveying surface may be used instead of flights to serve as stop elements. The pads provide enough friction to prevent packages from sliding past. 
         [0018]    The inclined conveyor belt  18  drops packages off its upper end onto a tilted conveyor belt  24 . The tilted conveyor belt can be realized as a flat rubber belt or a modular plastic friction-top belt, such as an INTRALOX® Series 1400 Friction Top belt or an INTRALOX® Series 900 Diamond Friction Top belt manufactured and sold by Intralox, L.L.C. of Harahan, La., U.S.A. The outer conveying surface  26  of these modular high-friction belts is largely covered by a high-friction elastomer. As an alternative, the tilted belt may be made high-friction by texturing a normally low-friction outer conveying surface. In any event, the outer surface&#39;s frictional characteristics, such as the coefficient of friction the belt presents to the bottoms of packages, and the tilt angle β of the belt are selected to hold flat packages F whose bottoms rest on the outer conveying surface to the belt, while allowing non-flat packages N to tumble downward from an elevated side edge  28  of the tilted belt across the belt and past a lower side edge  29 . Of course, flat packages that are stacked atop other packages or that drop to the tilted conveyor on edge are likely to fall past the lower side edge along with the tumbling non-flat packages. The tilted conveyor belt  24  conveys the retained flat packages F in a direction of belt travel  30 . A horizontal collection conveyor  32  parallel and adjacent to the lower side edge  29  of the tilted conveyor belt  24  receives all the non-flat packages N and the few flat packages that tumble off the tilted belt and conveys them in the direction of belt travel  30 . Both the tilted conveyor belt  24 , which conveys mostly flat packages, and the horizontal conveyor  32 , which conveys mostly non-flat packages, feed those initially separated packages onto a culling conveyor  34  to provide further culling if necessary. 
         [0019]    Although the high-friction outer conveying surface of the tilted conveyor belt described constitutes one kind of retention means used to prevent flat packages from sliding off the lower side edge of the tilted conveyor belt, other retention means may be used. For example, a raised barrier  33  upstanding from the outer conveying surface  26  and extending along its length near the lower side edge  29  of the tilted conveyor belt  24  is another retention means that could be used to catch the flat packages and prevent them from sliding off the lower side edge. If a raised barrier is used, the conveying surface does not necessarily have to exhibit high-friction characteristics. The height of the barrier can be slight, as long as it is high enough to stop flat packages whose bottoms are sitting on the outer conveying surface from sliding past. The barrier may be continuous along the length of the tilted conveyor belt, or it may be segmented. 
         [0020]    The culling conveyor  34  includes a roller conveyor belt  36  (also shown in  FIGS. 4-6 ) that has package-supporting rollers  38  protruding from its outer surface. The rollers are arranged to rotate in a first direction  40  in an upstream portion  41  of the culling conveyor  34  and in a reverse direction  42  in a downstream portion  43 . In this way, packages are pushed toward a first side of the roller conveyor belt in the upstream portion along a trajectory more or less in the direction of arrow  46  and toward an opposite second side  45  in the downstream portion along a trajectory more or less in the direction of arrow  47 . The roller conveyor belt  36  is realized as an INTRALOX® Series  7000  roller belt in which the rollers  38  extend through the thickness of the belt and rotate on axes  48  parallel to the travel direction  50  of the belt. The rollers are actuated in the upstream portion of the conveyor by passive actuating rollers  52  mounted to the conveyor frame on which the belt rollers ride as the roller belt advances in the travel direction (out of the page in  FIG. 4 ). One version of such an actuated roller-belt conveyor is described in U.S. Pat. No. 7,506,751, “Conveyor Systems for Diverting Objects,” Matthew L. Fourney, issued Mar. 24, 2009. The disclosure of that patent is incorporated by reference in to this description. 
         [0021]    A culling element in the form of an elongated powered roller  54  extends along the length of the culling conveyor in the upstream portion and is aligned laterally closer to the elevated side edge  28  of the tilted conveyor belt  24  than with the horizontal conveyor  32 . The powered roller is rotated continuously in the direction indicated by arrow  56  in  FIG. 4 . A vertical gap  58  between the bottom of the powered roller  54  and the tops of the belt rollers  38  is large enough to allow flat packages F to pass through, but not non-flat packages N. The powered roller  54  rotates in a direction that pushes the faces  60  of the non-flat packages that come in contact with the side of the roller opposite the first side  44  upward. This causes the non-flat package to pivotally lift off flat packages it is stacked on to allow them to be propelled through the gap across the belt in the direction of arrow  62  and over the first side  44  onto a chute or tilted tray  64  ( FIG. 3 ) for removal. 
         [0022]    To prevent flat packages from encountering the powered roller  54 , which would tend to eject a flat package out of the gap the wrong way, the powered roller is outfitted with a guide  66  having a bottom surface  68  that prevents flat packages F passing through the gap from contacting the roller, as shown in  FIG. 5 . The vertical position  70  of the guide  66  may be adjusted to set the maximum thickness of flat packages allowed to pass through the gap. The maximum thickness is the distance between the bottom surface  68  of the guide and the tops of the belt rollers  38  in the roller conveyor belt. 
         [0023]    To further help pull flat packages F through the vertical gap under the powered roller  54 , one or more powered ejection rollers  72 ,  73  with axes of rotation  74  parallel to the powered roller  54 , may be positioned at the first side of the roller belt  36 . The ejection rollers draw the flat package F in the gap with a pinch point  76  between each other and pull the flat package through the gap and eject it onto the flat-package collection chute  64 . In this way, the ejection rollers supplement the belt rollers  38  in moving flat articles through the gap under the powered roller  54 . Both ejection rollers may be powered to counterrotate as indicated by arrows  78 ,  79  in  FIG. 6 , or one of the ejection rollers could be a passive pinch roller biased toward the powered ejection roller. 
         [0024]    In some instances, only the upstream portion  41  of the final culling conveyor  34  may be required. But if a lot of side-by-side packages present a problem, the downstream portion  43  can be used with a similar powered roller  55  to form a two-stage culling conveyor. The downstream powered roller  55  extends along the length of the downstream portion of the culling conveyor laterally offset from the upstream power roller  54  and closer to the second side  45  rotating in the opposite direction to lift the side-by-side non-flat packages that were blocked by other packages from engaging the upstream powered roller. The belt rollers  38  in the downstream portion push the conveyed packages toward the second side of the roller belt with the blocked, side-by-side, non-flat packages the first to hit the downstream powered roller. Except that flat packages in the downstream portion are passed under the rollers onto a collection chute  65  at the second side of the conveyor, the powered rollers in both portions operate similarly. The taller non-flat packages that cannot pass through the vertical gaps between either powered roller and the belt rollers are confined by the powered rollers to the roller belt  36  and exit off its exit end  80 . Thus, the conveyor system automatically separates flat packages from non-flat packages. 
         [0025]    Another version of a culling conveyor is shown in  FIG. 7 . The culling conveyor  82  is identical to the upstream portion of the culling conveyor of  FIG. 3 , except that the culling element is realized as a side guard  84  rather than a powered roller. The side guard, which is shown as a vertical wall, may be positioned above the surface of the roller conveyor belt  36  or just outside the side edge of the belt. A gap  86  between the bottom of the side guard and the belt rollers  38  in the roller conveyor belt permits flat packages F to be pushed under the side guard and through the gap by the belt rollers rotating in the direction of arrow  86 . The flat packages that pass through the gap fall off the side of the belt onto a tilted tray or chute as in  FIG. 3 . The taller non-flat packages N are blocked by the side guard and conveyed downstream on the roller conveyor belt, where they can be collected or passed to a similar downstream culling-conveyor portion in which the belt rollers rotate in the opposite direction and the side rail is along the opposite side of the conveyor, as in the downstream portion of the culling conveyor of  FIG. 3 . The gap may be constant, for example, 0.25 in, along the length of the culling conveyor or may increase with distance downstream to help unstack flat packages resting atop other flat packages. Rollers  90  protruding from the bottom of the side guard may be used to provide low-friction, rolling contact with the flat packages. Alternatively, the side guard may be made of a low-friction, wear-resistant material, such as UHMW plastic. Strings  92 , or danglers, dangling from positions on bases  94  mounted above the roller conveyor belt drag over the tops of the packages being conveyed along the culling conveyor. The danglers drag flat packages off the tops of non-flat packages and onto the belt rollers. 
         [0026]    Although the invention has been described in detail with respect to one version, other versions are possible. For example, the incline conveyor could deposit packages onto the tilted conveyor belt over the upstream end of the tilted conveyor belt rather than over its elevated side. As another example, more powered-roller portions could be added to the culling conveyor to provide more opportunities to remove side-by-sides. And the culling conveyor could comprise one roller conveyor belt with upstream actuating rollers arranged to rotate the belt rollers in one direction and downstream actuating rollers arranged to rotate the belt rollers in the opposite direction, or the culling conveyor could comprise upstream and downstream conveyor belts whose rollers are actuated to rotate in opposite directions. Furthermore, the culling conveyor can be used independently of the incline, tilted, and horizontal collection conveyors, and vice versa. So, as these few examples suggest, the scope of the claims is not meant to be limited to the details of the specific version used to describe the invention.