Abstract:
A modular gravity-advance roller conveyor for conveying articles down an inclined path. The conveyor comprises an easy-to-configure modular conveyor mat supported in a conveyor frame with an inclined base. The conveyor mat is constructed of a series of rows of roller-top modules with rollers that extend above the top surface of the mat. Connecting elements along the ends of each row are connected to the connecting elements of adjacent rows to form the mat. The rollers on a roller-top module rotate about an axis of rotation. Modules with rollers that rotate about a given axis of rotation can be combined with modules with rollers that rotate about a different axis of rotation in a variety of patterns to meet common or special conveying requirements.

Description:
BACKGROUND OF INVENTION  
       [0001]     The invention relates generally to gravity-advance conveyors and, more particularly, to inclined rollerways made of modular roller sections for conveying articles down an inclined path.  
         [0002]     Gravity-advance roller conveyors, in which a roller conveyor bed is arranged on an incline, are often used to convey pallets or boxes from high levels to lower levels in warehouses. Because gravity-advance conveyors do not require a drive system, they are less complex than powered-roller conveyors. But, like all conventional metal roller conveyors, powered or not, gravity-advance roller conveyors are noisy when articles are advancing along them. Furthermore, the conveyor frames include mounting holes positioned along the sides to support the ends of the rollers or shafts on which the rollers rotate. Because of the fixed position of the mounting holes in a given conveyor frame, it is difficult to adapt the conveyor frame to accommodate, for example, a change in the orientation of the rollers without extensive rework.  
         [0003]     Thus, there is a need for a conveyor that avoids some of the shortcomings of conventional gravity-advance roller conveyors.  
       SUMMARY OF INVENTION  
       [0004]     This need and other needs are satisfied by a modular gravity-advance roller conveyor embodying features of the invention. One version of conveyor comprises a mat that is constructed of a plurality of rows of modules. Each row extends longitudinally from a first end to a second end, transversely from a left side to a right side, and in thickness from a top surface to a bottom surface. Each row further includes connecting elements along each end linked with the connecting elements of consecutive rows to form the mat, which extends from an entrance end to an exit end. At least some of the rows have rollers extending above the top surface of the row. A conveyor frame includes an inclined base that supports the mat. The elevation of the entrance end of the mat is higher than the elevation of the exit end. In this way, the weight of an article introduced onto the mat causes the rollers beneath the article to rotate. The rotating rollers move the article down the inclined mat toward the exit end.  
         [0005]     In another version of the invention, a modular gravity-advance roller conveyor comprises a stationary mat, which includes a plurality of modules linked together in rows. At least some of the modules have rollers extending above the top surface of the mat. A conveyor frame includes an inclined base supporting the mat between a higher end and a lower end. The weight of articles introduced onto the mat causes the rollers in contact with the articles to rotate and move the articles toward the lower end of the mat.  
         [0006]     In another aspect of the invention, a modular gravity roller conveyor comprises a conveyor frame with an inclined base. A length of modular plastic roller-top conveyor belt is supported stationarily on the inclined base to form a modular gravity roller conveyor.  
         [0007]     In yet another aspect of the invention, a method for constructing a gravity conveyor comprises providing a conveyor frame with an inclined base and supporting a length of modular roller-top conveyor belt stationarily on the inclined base of the conveyor frame.  
     
    
     BRIEF DESCRIPTION OF DRAWINGS  
       [0008]     The features, aspects, and advantages of the invention are better understood by reference to the following description, appended claims, and accompanying drawings, in which:  
         [0009]      FIG. 1  is an isometric view of a gravity roller conveyor embodying features of the invention;  
         [0010]      FIGS. 2A and 2B  are top and bottom isometric views of a cylindrical roller-top module usable in a conveyor as in  FIG. 1 ;  
         [0011]      FIG. 3  is an isometric view of a ball-top module useable in a conveyor as in  FIG. 1 ;  
         [0012]      FIG. 4  is a schematic representation of a plan view of the gravity roller conveyor of  FIG. 1 ; and  
         [0013]      FIGS. 5, 6 , and  7  are schematic representations of plan views of other roller arrangements for gravity conveyors embodying features of the invention. 
     
    
     DETAILED DESCRIPTION  
       [0014]     A conveyor embodying features of the invention is shown in  FIG. 1 . The conveyor includes a frame  10  having front legs  12  and longer rear legs  13  supporting a base  14  inclined downwardly from rear to front in  FIG. 1  to form a gravity-advance conveyor frame. Wearstrips  16  in the form of transversely spaced longitudinal strips support a conveyor mat  18 . The mat is constructed of a series of rows  20 A-D of modules  22 . Each row extends longitudinally from a first end  24  to a second end  25 , transversely from a right side  26  to a left side  27 , and in thickness from a top surface  28  to a bottom surface  29 . Connecting elements  30  that are spaced apart along the ends of each row interleave with the connecting elements of adjacent rows. A connecting pin  32  extending through a passageway formed by aligned transverse apertures  34  through the connecting elements connects adjacent rows together. Pins  36  through the apertures of the uppermost and lowermost connecting elements of the mat are retained at their ends in retainers  38  on the frame to secure the mat in place. The mat can be easily constructed from a length of modular plastic conveyor belt, such as the roller-top versions of the Series 400 belt manufactured and sold by Intralox, Inc., of Harahan, La., USA. Although a single mat is shown, the conveyor could be constructed of a number of abutting or closely spaced individual mats, and the term “mat” refers to both constructions.  
         [0015]     The mat shown in  FIG. 1  is constructed of roller-top modules  40 ,  41 ,  42 . The center modules  40  have rollers  44  that are arranged to rotate about transverse axes  46 . The rollers in the left-side modules  41  rotate about first axes  48  oblique to the transverse direction. The rollers in the right-side modules  42  rotate about second axes  49  oblique to the transverse direction and mirroring the first axes about the centerline of the mat. At least a portion of each roller extends above the top surface of the mat to engage the undersides of articles  50  introduced onto the conveyor. Because of the incline, the weight of the articles on the rollers causes the rollers in contact with the articles to rotate and direct the articles in a direction generally perpendicular to the roller axes. An outer portion of each roller could, but does not have to, extend beyond the bottom surface of the mat. If the rollers do extend beyond the bottom surface of the mat, they are preferably arranged in transversely spaced longitudinal lanes so that the mat can be positioned on the supporting wearstrips with the strips between the roller lanes to avoid interfering with the rotation of the rollers. If the rollers do not extend outward of the bottom surface, other wearstrip patterns can be used.  
         [0016]     In the example conveyor of  FIG. 1 , the angled roller arrangement on the left side urges articles entering the upper entrance end  43  of the mat toward the right, and the oppositely angled roller arrangement on the right side urges articles towards the left. As articles reach the center of the mat, the central rollers that rotate about transverse axes direct the articles straight down the conveyor and off the lower exit end  45  of the mat. Thus, the conveyor of  FIG. 1  acts as a gravity-advance centering roller conveyor by directing articles toward the center of the conveyor.  
         [0017]     A typical angled roller-top belt module that could be used as a left-side module in the conveyor of  FIG. 1  is shown in  FIGS. 2A and 2B . The module  52  has a flat top surface  54  and an opposite bottom surface  55 . Cylindrical rollers  56  are rotatably mounted in cavities  58  that open onto the top surface and the bottom surface. The rollers rotate on axles  60  retained in the interior of the module. Connecting elements  62  along each end of the module include aligned apertures  64  for receiving connecting pins to interconnect modules together. A module usable in the center or in right side of the conveyor of  FIG. 1  would be similarly formed, but with the orientation of the rollers appropriately arranged. The module bodies are preferably formed by injection molding out of thermoplastic materials such as polyethylene, polypropylene, acetal, and composite resins, for example.  
         [0018]     Instead of using modules with cylindrical rollers that rotate about fixed axes, the conveyor of  FIG. 1  could use modules  66  with universally rotatable ball rollers  68 , as shown in  FIG. 3 . The module is similar to that of  FIG. 2 , but includes a round cavity  70  opening onto the top surface  72 . The roller ball is confined in the round cavity with a salient portion of the ball extending above the top surface of the module. The module is further shown with openings  74  through the module body for drainage, airflow, or weight reduction. These ball-top modules are usable, for example, as the central modules in  FIG. 1 .  
         [0019]     The spherical and cylindrical rollers described in detail with respect to  FIGS. 2 and 3  are just two examples of the types of rollers that can be used in a conveyor as in  FIG. 1 . Because of the modularity of modular plastic conveyor belts, it is easy to reconfigure a mat constructed of plastic modules to accommodate changing conveyor requirements. The centering conveyor of  FIG. 1  is represented functionally by  FIG. 4 , which is a plan view of the conveyor mat. The arrows indicate the direction in which articles move as they make their way down the conveyor. The arrows are directed generally perpendicular to the axes of rotation of the rollers in that portion of the conveyor mat. Consequently, the schematic representation of  FIG. 4  corresponds to the physical arrangement of  FIG. 1 . The conveyor mat  18  in  FIG. 4  is divided transversely into three longitudinal lanes  76 ,  77 ,  78 . The rollers in the left lane  76  and the right lane  78  are arranged to direct articles toward the center of the mat. The rollers in the center lane  77  direct articles straight down the conveyor mat. Thus,  FIG. 4  represents a centering conveyor.  
         [0020]      FIG. 5  represents another centering conveyor made with a modular mat  79 . In this example, the conveyor mat uses right- and left-side angled roller-top modules arranged in lanes  76 ,  78  similar to those represented in  FIG. 4 . But, unlike the mat represented by  FIG. 4 , this centering conveyor mat does not include a central lane of rollers directing articles straight down the conveyor mat. Instead, articles directed toward the center are allowed to wander slightly back and forth about the centerline of the mat as they advance down the conveyor.  
         [0021]     Another conveyor that can easily be constructed of modular components is represented in  FIG. 6 . In this example, the conveyor can serve to align articles along the outside edges of the conveyor (if a side rail or guard is in place) or to transfer articles off the side edges (if no obstruction is in place at the side). The conveyor includes a mat  80  divided transversely into two longitudinal lanes  82 ,  83 . The rollers in the left lane  82  are arranged obliquely to direct articles toward the left side of the conveyor. The rollers in the right lane  83  are arranged to direct articles toward the right side of the conveyor.  
         [0022]     Yet another conveyor that can be constructed out of roller-top belt modules is represented by  FIG. 7 . This conveyor includes a mat  84  divided longitudinally into two transverse portions  86 ,  87 . The rollers in the upper portion  86  are oriented to direct articles toward the right side of the conveyor mat. The rollers in the lower portion  87  are arranged to direct articles straight down the conveyor. In this way, the conveyor represented by  FIG. 7  moves articles toward the right side before advancing them off the lower exit end.  
         [0023]     As these few examples suggest, a modular roller-top conveyor mat can be easily reconfigured and placed in a gravity-advance roller conveyor frame to accommodate a wide variety of conveying requirements. The modularity allows readily available modules with rollers capable of rotating about a range of axes to be connected together in a pattern, even with non-roller-top modules, to form a custom conveyor mat. It should further be clear that, although the conveyor mats described in detail were laid out in the conveyor frame with connecting pins transverse to the gradient of the incline, the conveyor mats could be laid out on an inclined conveyor frame with connecting pins along or oblique to the gradient. Because it is impossible to describe all the possible patterns and arrangements, the scope of the invention is not meant to be limited to the specific versions described in detail.