Abstract:
A cleanable belt conveyor and a method for making a cleanable belt conveyor having an underside sculpted with concave indentations to match the shape and positions of the elongated support rails forming a carryway. The support rails may be circular in cross section, and the indentations may be complementary portions of circular cylinders to receive the rails along an extended contact area.

Description:
BACKGROUND 
       [0001]    The invention relates generally to power-driven conveyors and more particularly to belt conveyors that are easy to clean. 
         [0002]    In the meat, poultry, fruit, and vegetable industries, conveyor belts are used to transport food products. Most conveyor belts are supported along carryways atop flat-topped wearstrips. Flat bottom surfaces on the belts riding along the flat-topped wearstrips provide sufficient contact area to spread the load and avoid high-pressure wear regions on the underside of the belt. But horizontal flat-topped support surfaces allow cleaning water to pool. Dirt and bacteria in the pooled water can contaminate the conveyed products. Crowned wearstrips prevent pooling of cleaning water, but contact the undersides of belts along a smaller high-pressure contact area, which results in increased wear of the belts and wearstrips. 
         [0003]    Thus, there is a need for a cleanable, wear-resistant belt conveyor. 
       SUMMARY 
       [0004]    This need and other needs are addressed by a conveyor embodying features of the invention. One version of such a conveyor comprises a carryway supporting a conveyor belt on support rails. The carryway includes parallel elongated support rails that extend longitudinally to define the length of the carryway. The parallel support rails are spaced apart laterally and have convex upper surfaces. The conveyor belt has an outer conveying side and an opposite underside supported on the support rails. The underside includes concave indentations that are spaced apart laterally and aligned longitudinally in columns to receive the support rails in the carryway. The concave indentations are shaped to contact the convex upper surfaces of the support rails along a contact area. 
         [0005]    In another aspect, a conveyor belt embodying features of the invention comprises an outer conveying side and an opposite underside. Concave indentations are spaced apart laterally across the underside. The concave indentations are aligned in longitudinal columns in a direction of belt travel and are shaped to contact complementarily shaped support rails received in the concave indentations. 
         [0006]    In another aspect, a method for making a cleanable belt conveyor comprises: (a) constructing a carryway with a plurality of parallel elongated support rails that have convex upper surfaces; and (b) supporting a conveyor belt in the carryway on columns of concave indentations laterally spaced on the underside of the conveyor belt to mate with the convex upper surfaces of the support rails. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]    These aspects and features of the invention are described in more detail in the following description, appended claims, and accompanying drawings, in which: 
           [0008]      FIG. 1  is an oblique view of a portion of a conveyor belt and carryway embodying features of the invention; 
           [0009]      FIGS. 2A-2C  are front elevation, side elevation, and bottom perspective views of one version of a conveyor belt module for a conveyor belt as in  FIG. 1 ; 
           [0010]      FIGS. 3A-3C  are front elevation, side elevation, and perspective views of another version of a conveyor belt module for a conveyor belt as in  FIG. 1 ; 
           [0011]      FIG. 4  is a front elevation view of a third version of a conveyor belt module for a conveyor belt usable on a carryway as in  FIG. 1 ; 
           [0012]      FIG. 5  is an isometric view of a portion of the underside of another version of a conveyor belt usable with support rails as in  FIG. 1 ; and 
           [0013]      FIG. 6  is an isometric view of a portion of the underside of a conveyor belt as in  FIG. 5 , but with deeper concave indentations. 
       
    
    
     DETAILED DESCRIPTION 
       [0014]    A portion of a belt conveyor embodying features of the invention is shown in  FIG. 1 . The exemplary conveyor  10  comprises a conveyor belt  12  supported on a carryway  14  composed of parallel elongated support rails  16  supported on legs  18 . In this example, three rails are shown. The length of the carryway is defined by the longitudinal extent of the support rails. The conveyor belt  12  shown in  FIG. 1  is a modular plastic conveyor belt that is constructed of a series of rows  22  of belt modules  24  hingedly linked at hinge joints  26  between consecutive rows. In this example, each row comprises a single belt module. But the rows could include more than one module. Along the carryway, the belt forms a top carryway surface on an outer conveying side  27 . Drive structure  28  formed on an opposite underside  29  of the belt engages drive faces on drive sprockets (not shown). The hinge joints are formed by interleaved leading and trailing hinge elements  30 ,  31  of consecutive rows. The hinge elements may include holes ( 32 ,  FIGS. 2B and 3B ) aligned laterally across the width of the conveyor belt  12  with the holes of interleaved hinge elements of a consecutive module to form a lateral passageway for one or more hinge rods (not shown). Alternatively, some of the hinge elements may include laterally extending stubs serving as hinge rods that are received in laterally opening recesses in adjacent interleaved hinge elements to form the hinge joints. The modular plastic conveyor belt  12  shown in  FIG. 1  is made of a thermoplastic polymer, such as polypropylene, polyethylene, acetal, nylon, or a composite polymer, in an injection-molding process. But other kinds of belts, such as flat belts, may be used in the conveyor. 
         [0015]    The conveyor belt  12  may be conventionally trained around idle and motor-driven drive sprockets or drums (not shown) at each end of the carryway and returned along a returnway (not shown) below the carryway. The drive sprockets engage the drive structure  28  to positively drive the belt along the carryway in the direction of belt travel  20 . 
         [0016]    The conveyor belt module  24  and its engagement with the support rails  16  is shown in more detail in  FIGS. 2A-2C . The module has drive structure on the underside  29  in the form of a drive bar  34  that extends laterally across the width of the module and the belt row. The bottom  35  of the drive bar  34  extends below the bottom surfaces  36  of the hinge elements  30 ,  31 . The support rails  16  are shown with circular cross sections. The convex outer surfaces of the rails are more hygienic and easier to clean than the flat tops of conventional wearstrip supports. Sculpted into the drive bar  34  on the underside  29  of the module  24  are concave indentations  38  spaced apart laterally across the width of the module. When series of modules are linked together into a belt, the indentations are aligned in longitudinal columns. The concave indentations are shaped to match the convex shape of the upper surface  40  of the support rails  16 . In this example, each indentation defines a portion of a circular cylinder that complements the circular cross section of the support rail over some or all of the lateral extents of the indentations and the upper surfaces of the support rails. In this example, the indentation contacts the support rails along a contact area  42  commensurate with at least a major portion of the indentation. (The contact area on the indentation is shown cross-hatched in  FIG. 2C .) The contact area is much greater than for a module with a flat, unsculpted underside that would contact the circular support rail  16  only along its topmost tangent line. The greater contact area distributes the load, decreasing contact pressure and wear. Furthermore, the engagement of the indentations with the support rails provides tracking by preventing the belt from wandering laterally. 
         [0017]    The hinge elements  30 ,  31  are laterally offset from each other and are also shaped along their outer bottom sides  44  to avoid contact with the support rails. Thus, in the example shown in  FIGS. 2A-2C , the middles  46  of the indentations  38  are positioned midway between the middles of leading and trailing hinge elements  30 ,  31  of a module. 
         [0018]    Another version of a belt module usable in a conveyor as in  FIG. 1  is illustrated in  FIGS. 3A-3C . The module  48  differs from the module  24  of  FIGS. 2A-2C  in that its drive bar  50  does not extend below the bottoms  35  of the hinge elements  30 ,  31 . Because of the shallower drive bar  50  with the same hinge-element dimensions and spacings as in  FIGS. 2A-2C , the contact areas  51  provided by the smaller indentations  52  are smaller than those in  FIG. 2C . Furthermore, the support rails  54  are smaller in diameter than the support rails  16  in  FIG. 2A  to avoid the hinge elements. Otherwise, the concave indentations and the convex top surfaces of the support rails are complementarily shaped—in this example, arcuately shaped—so that the contact area between them is increased and wear is reduced. 
         [0019]    As shown in  FIG. 4 , a concave indentation  60  may be formed on an attachment  62  depending below the underside  64  of a belt module  66 . The attachment  62  may be made of the same material as the module  66 , but could be made of a more durable or lower-friction material for a longer wear life. If the attachment does wear, it can be replaced without the need to replace the entire module. The attachment  62  shown in  FIG. 4  has two arms  68  that extend through the module and terminate in tabs  70  that engage structure in the module that retains the attachment in place. But the attachment and the module may be designed with other means for removably fastening the attachment. Instead of a removable attachment, the underside portions of the module could be formed with a more wear-resistant material overmolded onto or co-molded with the rest of the module. 
         [0020]      FIGS. 5 and 6  show other versions of conveyor belts usable with the convex carryways shown in  FIGS. 1-3 . The length portion of the conveyor belt  72  in  FIG. 5  has as an underside  73  with drive bars  74  extending laterally across the width of the belt and regularly spaced along its length. To accommodate convex carryway support rails as in  FIG. 1 , the underside  73  is sculpted with concave indentations  76  from drive bar to drive bar arranged in longitudinal columns extending along the length of the belt to receive longitudinally extending complementary support rails. The conveyor belt  78  in  FIG. 6  has an underside  80  sculpted with a drive bar  82  and laterally spaced concave indentations  84  that are deeper than the height of the drive bar and extend into the thickness of the flat belt mat to form longitudinal columns of concave indentations for receiving convex support rails. The belts shown in  FIGS. 5 and 6  could be positively driven, low-tension conveyor belts or timing belts, as two examples. 
         [0021]    Although the invention has been described with reference to specific versions, other versions are possible. For example, the support rails do not have to be circular over 360° in cross section: a semicircular cross section with the flat side down could be used. And other non-circular convex support rails could be used with non-circular mating concave indentations. As another example, belts without drive bars could be used. In that case, the indentations would be formed in other underside belt structure. So, as these few examples suggest, the scope of the invention is not meant to be limited to the exemplary versions described in detailed.