Abstract:
A modular radius conveyor belt having magnetic material in adjacent belt rows, including magnets in selected rows of belt modules. Magnets in one belt row attract magnets or paramagnetic material in adjacent rows to prevent vibration between rows that could shake a conveyed article out of its preferred position or orientation on the conveyor belt.

Description:
BACKGROUND 
       [0001]    The invention relates generally to power-driven conveyors and more particularly to modular radius conveyor belts having magnets to prevent vibration between consecutive rows of belt modules. 
         [0002]    Side-flexing, or radius, conveyor belts are used to convey articles on a conveying path that includes turns. Modular plastic radius conveyor belts, such as the INTRALOX® Series 2600 SPIRALOX® 1.1 Radius belt manufactured and sold by Intralox, L.L.C. of Harahan, La., U.S.A., are constructed of a series of rows of belt modules linked together end to end at interleaved hinge eyes forming hinge joints. When negotiating a turn, these radius belts collapse at the inside of the turn because the travel path at the edge of belt at the inside of the turn is shorter than the path of the opposite edge at the outside of the turn. Because all the belt tension passes through the outside edge portion of the belt, the outside edge is fully expanded and stretched tight, while the collapsed inside edge is free of tension. Unlike the taut outside edges of the belt rows, the untensioned inside edges are free to move relative to each other in the direction of belt travel. As the inside edges of the rows rub along the inside rail or the side of a drive tower in a spiral conveyor, they tend to stick and release continuously. As they do so, they bump into each other as the belt advances. The bumping causes the belt edges to chatter and the belt to vibrate, which can cause conveyed articles to change their orientations atop the belt. In many applications, product orientation is important. And chatter is annoying. 
         [0003]    Thus, there is a need for a conveyor belt that does not vibrate enough to change product orientation. And there is a need to reduce chatter in radius and spiral belts. 
       SUMMARY 
       [0004]    These needs and others are addressed by a modular conveyor belt embodying features of the invention. One version of such a conveyor belt comprises a series of rows of one or more belt modules hingedly linked together at hinge joints that extending transverse to a direction of belt travel from a first side edge of the rows to an opposite second side edge. Magnetic material is disposed in selected rows. At least some of the selected rows are magnet rows in which the magnetic material in each magnet row comprises a first magnet arranged to attract the magnetic material in an adjacent selected row. 
         [0005]    In another aspect of the invention, a conveyor belt module comprises a first hinge end and an opposite second hinge end that define first and second hinge axes extending transverse to a travel direction between first and second side edges. At least one magnet has a polar axis parallel to the travel direction. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0006]    These aspects and features of the invention, as well as its advantages, are described in more detail in the following description, appended claims, and accompanying drawings, in which: 
           [0007]      FIG. 1  is a bottom plan view of a portion of one version of a modular radius conveyor belt embodying features of the invention; 
           [0008]      FIG. 2  is a top plan view of one edge of the conveyor belt of  FIG. 1  at the inside of a turn; and 
           [0009]      FIG. 3  is a top plan view of the opposite edge of the conveyor belt of  FIG. 1  at the outside of a turn. 
       
    
    
     DETAILED DESCRIPTION 
       [0010]    A portion of a modular plastic conveyor belt embodying features of the invention is shown in the bottom plan view of  FIG. 1 . The conveyor belt  10  shown is a radius, or side-flexing, belt following a conveying path that includes straight  12  and curved  13  segments. The belt is constructed of a series of rows  14  of belt modules. Each row extends laterally across the width of the belt from a first side edge  16  to a second side edge  17  and, in the direction of belt travel  18 , from a leading end  20  to an opposite trailing end  21  when the belt is traveling to the left in  FIG. 1 . (The descriptors “leading” and “trailing” are not meant to limit the belt to a certain direction of travel, but merely to help describe the general spatial relationships of various elements of the example versions described.) Each belt row  14  is made up of a number of belt modules arranged side by side. In this example, a row includes a first side edge module  24  and a second side edge module  25  separated at a seam  26 . Internal modules (not shown), formed without belt edge structure, could be positioned between the two side edge modules in a row to form a wider belt. And, even though each row in  FIG. 1  includes more than one belt module, each row could be formed of a single module that has side-edge structure  28 ,  29  at both edges. Consecutive side edge modules are cut to different widths to construct the belt in a bricklay pattern. The belt modules are, for example, injection-molded out of a thermoplastic polymer, such as polyethylene, polypropylene, acetal, nylon, or a composite resin. 
         [0011]    Each row  14  of the conveyor belt  10  has a set of leading projections  30 ′,  30 ″ spaced apart laterally along the leading end  20  and a set of trailing projections  31 ′,  31 ″ spaced apart laterally along the trailing end  21 . The leading and trailing projections are laterally offset from each other so that they can be interleaved with each other. In this example, some of the projections  30 ′,  31 ′ are A-shaped with two legs  32 , and other projections  30 ″,  31 ″ have a single leg  33 . The projections of each row have elongated rod holes  34 ,  35  that form a lateral passageway with the aligned holes of the interleaved projections, or hinge eyes, of adjacent modules. A hinge rod  36  is received in the passageway to connect adjacent belt rows together at a hinge joint  38 . 
         [0012]    In a turn  13 , as in  FIG. 1 , the inside edge  16  of the radius conveyor belt  10  travels a shorter distance than the edge  17  at the outside of the turn. The elongated rod holes  34 ,  35  allow the inside edges  16  of the rows to collapse at the inside of a turn as the outside edges  17  are expanded and bear all the belt tension. Because the inside edges  16  of the rows  14  bear no tension in a turn, they have a certain freedom of movement relative to each other. As the inside edges come into frictional contact with an inside rail  40  or structure on the periphery of a drive drum in a spiral conveyor, the edges can stick against the rail until the belt advances far enough to produce enough force through the belt row to overcome the friction preventing movement of the inside edge along the rail. Because no belt tension is borne by the inside edge  16 , it can jump forward enough to bump into a leading belt row. A magnet  42 , such as a permanent magnet, is disposed in each projection  31 ′ at the inside edge  16  of each belt row, as shown in only two rows to avoid clutter in  FIG. 1  and in all rows in the enlarged top plan view of  FIG. 2 . (Although the drawing shows the magnet in the projection closest to the inside of the turn, the magnet could alternatively reside in one or more projections spaced a few projections farther along the row from the inside of the turn. Thus, the term “edge” is not meant to be limited strictly to an outside border, but to a region along a belt row extending inward along the row from the outside border; and the phrase “at the edge” means “in an edge region.”) The magnets  42  are arranged with their polar axes  44  parallel to the direction of belt travel  18  and with opposite poles (+, −) of adjacent rows facing each other to produce an attractive force between rows. In other words, the magnets face the same way in all the rows and produce magnetic fields that extend outward of the rows. As the inside edge  16  of the belt collapses at the inside of a turn  13 , the attractive forces between the magnets of adjacent rows hold the untensioned inside belt edges together and minimize the number of impacts between inside belt edges to reduce belt vibration, which can cause conveyed articles to move out of their preferred orientation or position on the belt. As shown in  FIG. 3 , the magnets  42  can also be disposed at the outer side edge  17  of the belt to help reduce vibration even more or in case the belt has to negotiate turns in the opposite direction. To reduce weight, the individual magnets  42  at either edge can be replaced by pairs of aligned magnets  46  with their opposite poles facing each other, as shown in the outer side edge  17  of one of the rows of the conveyor belt in  FIG. 3 . It would also be possible to replace the magnets  42  in selected belt rows, such as every other row, with a paramagnetic material  48 , e.g., a piece of iron, or other material that is attracted by the magnets  42  in leading and trailing magnet rows. The paramagnetic material or the magnets could also be realized by compounding paramagnetic particles or magnetic articles with thermoplastic resin and molded together to form the magnetic portion of the belt module or overmolded onto the belt module. Furthermore, not every row needs to have a magnet or paramagnetic material to reduce vibration enough in some cases. Thus, only selected rows would include a magnetic material, with all the selected rows having magnets as their magnetic material (all magnet rows), with some of the selected rows having magnets and other of the selected rows having paramagnetic materials as their magnetic materials, or with all the selected rows having a combination of magnets and paramagnetic materials. If all the rows are selected rows, then all the rows have magnetic material; otherwise, some of the rows are devoid of magnetic material. 
         [0013]    Although the invention has been described with reference to an exemplary version, other versions are possible. For example, the magnets can be embedded permanently within the belt modules or can be detachably mounted to the modules. As another example, each row could include a magnet at the leading edge and a paramagnetic material along the trailing edge attracted by the magnet in the leading edge of the trailing row. As yet another example, electromagnets could be used instead of permanent magnets. So, as these few examples suggest, the scope of the claims is not meant to be limited to the details of the exemplary version.