Abstract:
A modular conveyor belt formed of rows of belt modules pivotally interlinked by transverse pivot rods and specially adapted for following a curved conveyor path. The modules include a top, product conveying surface and a bottom, sprocket-driven surface. The belt modules have a plurality of first link ends disposed in the direction of travel of the conveyor belt and a plurality of second link ends disposed in the opposite direction. Transverse holes in the link ends are aligned to accommodate a pivot rod. When the link ends of the consecutive rows of side by side modules are intercalated, the pivot rod serves as a hinge pin in a hinged joint between consecutive interlinked rows. To permit the belt to flex sidewise, the openings in the first link ends are slotted longitudinally in the direction of belt travel.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
   The present application is a continuation of U.S. patent application Ser. No. 10/282,068 filed Oct. 29, 2002, now abandon which is a continuation of U.S. patent application Ser. No. 09/874,589 filed Jun. 5, 2001, now U.S. Pat. No. 6,523,680, which is a continuation-in-part application claiming priority to U.S. patent application Ser. No. 09/579,090 file May 25, 2000, now U.S. Pat. No. 6,330,941 and entitled “Radius Conveyor Belt”, all of which are incorporated herein by reference. 

   FIELD OF INVENTION 
   This invention relates to conveyor belts and, more particularly, to modular plastic conveyor belts formed of rows of plastic belt modules pivotally interlinked by transverse pivot rods. 
   BACKGROUND OF THE INVENTION 
   Because they do not corrode, are light weight, and are easy to clean, unlike metal conveyor belts, plastic conveyor belts are used widely, especially in conveying food products. Modular plastic conveyor belts are made up of molded plastic modular links, or belt modules, that can be arranged side by side in rows of selectable width. A series of spaced apart link ends extending from each side of the modules include aligned apertures to accommodate a pivot rod. The link ends along one end of a row of modules are interconnected with the link ends of an adjacent row. A pivot rod journaled in the aligned apertures of the side-by-side and end-to-end connected modules forms a hinge between adjacent rows. Rows of belt modules are connected together to form an endless conveyor belt capable of articulating about a drive sprocket. 
   In many industrial applications, conveyor belts are used to carry products along paths including curved segments. Belts capable of flexing sidewise to follow curved paths are referred to as side-flexing, turn, or radius belts. As a radius belt negotiates a turn, the belt must be able to fan out because the edge of the belt at the outside of the turn follows a longer path than the edge at the inside of the turn. In order to fan out, a modular plastic radius belt typically has provisions that allow it to collapse at the inside of a turn or to spread out at the outside of the turn. 
   Apertures slotted in the direction of travel of the belt are commonly provided in the link ends on at least one side of the modules to facilitate the collapsing and spreading of the belt. 
   The requirement of following a curved path caused problems not found in straight-running belts. As one example, radius belts especially if tightly tensioned or running fast and lightly loaded, tend to rise out of the conveyor support around a turn. As another example, because belt pull is concentrated in the outer portion of the belt as it rounds a turn, outer link end are more likely to fail unless otherwise strengthened or bolstered. 
   There are other problems with some common belt designs. For example, stresses can be molded into the plastic modules during the manufacturing process. Sharp, as opposed to curved, junctions between molded features on a belt are more likely to form concentrated stress regions. When such modules make up a conveyor belt, operation of the belt increases the stress in those regions. In a radius belt, in which the pulling load is unevenly distributed across the width of the belt as it rounds a turn, the problem is exacerbated. One way to solve the problem is to add more material to belt, but that makes the belt heavier, increases the production cost due to the larger molding cycle and closes in some of the desirable open area that allow for drainage of air flow. 
   Another problem with some structures of radius belt is compression of the modules transverse to the direction of belt travel. A radius belt bricklayed to a width of, for example one meter, may compress by three to four millimeters as the belt rounds a turn, which can cause the belt to come out of the conveyor support. Belt having the corrugated configuration shown in U.S. Pat. No. 5,372,248 to Horton are especially susceptible to bending and compression of this type. 
   What is needed is a modular radius conveyor belt that is resistant to compression and that improves the engagement of the belt to the drive sprocket. 
   BRIEF SUMMARY OF THE INVENTION 
   The present invention meets the above-described need by providing an endless conveyor belt formed of plastic belt modules and capable of following a curved path. The modules include first and second modules surfaces, i.e., a top, product-conveying surface and a bottom, sprocket-driven surface. An intermediate section extends across the width of each module transverse to the direction of belt travel. The intermediate section is formed in part by a web and in part by a thin, corrugated strip having a pair of essentially parallel walls. The corrugated strip form a series of regularly spaced alternating ridges and valleys along each wall. Link ends extend outward from the ridges on each wall of the corrugated strip. Each link end has a leg portion attached at a ridge of the strip and a thick distal portion at the end of the link end distant from the corrugated strip. Transverse holes in the link ends extending from respective walls of a module are aligned to accommodate a pivot rod. When the link ends of consecutive rows side-by-side modules are intercalated, the pivot rod serves as a hinged joint between consecutive interlinked rows. To permit the belt to follow a curved path, the pivot rod openings in a least one of the link ends extending from one of the walls of the corrugated strip are slotted longitudinally in the direction of belt travel. 
   The belt is driven by engagement of the sprocket tooth with the curved outside surface of the link ends. The link end engaged by the sprocket tooth is subjected to a compressive force rather than an undesirable tensile force. Thus, the link ends provide pull strength, resistance to belt and sprocket wear, and sprocket drivability. As an alternative, a central portion of a link end disposed in the middle belt modules may also engage with a tooth on the drive sprocket. Because the mid modules do not have to collapse fully, they may be formed with a thicker and fully straight cross-rib. 
   Each wall of the corrugated strip forms a series of arched recesses with the leg portions of the link ends. The recesses are large enough to provide room for a thick link end of an interlinked module of an adjacent row to collapse into the recess or to rotate as belt rows fan out going around a turn. Because the recesses along one wall overlap in a transverse direction with the recesses along the other wall, additional space for collapsing is provided. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention is illustrated in the drawings in which like reference characters designate the same or similar parts throughout the figures of which: 
       FIG. 1  is a top plan view of a radius conveyor belt of the present invention with a portion of one of the belt modules cutaway; 
       FIG. 2  is a top plan view of a belt module of the present invention; 
       FIG. 3  is an end elevation view of the belt module of the present invention; 
       FIG. 4  is a sectional view taken along lines  4 — 4  of  FIG. 2 ; 
       FIG. 5  is a bottom plan view of a belt module of the present invention; 
       FIG. 6  is a top perspective view of the belt module of the present invention; 
       FIG. 7  is a bottom perspective view of the belt module of the present invention; 
       FIG. 8  is a top plan view of an alternate embodiment of a belt module suitable for use in the middle of a bricklayed modular radius conveyor belt according to the present invention; 
       FIG. 9  is a bottom plan view of the belt module of  FIG. 8 ; 
       FIG. 10  is an end elevational view of the belt module of  FIG. 8 ; 
       FIG. 11  is a section view taken along lines  11 — 11  of  FIG. 8 ; 
       FIG. 12  is a top plan view of an alternate embodiment of the belt module of the present invention; 
       FIG. 13  is a sectional view taken along lines  13 — 13  of  FIG. 12 ; 
       FIG. 14  is a side elevational view of a drive sprocket engaging with the radius conveyor belt of the present invention; and 
       FIG. 15  is a cutaway side elevational view of a drive sprocket engaging with the link end and center cross-rib of the mid modules of the present invention. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Referring now to the drawings,  FIGS. 1  to  7  show a first embodiment of a portion of a modular belt  20  of the present invention. The portion of the modular belt  20  shown is formed from molded plastic modules  23 ,  26 , and  29 . For reference, the direction of belt travel is indicated by arrow  32 , however, the belt of the present invention may be conveyed in either direction. A pivot rod  35  connects adjacent belt modules by passing through openings in the modules disposed transverse to the direction of belt travel. 
   As shown in  FIG. 2 , an exemplary one of the belt module  26  has an intermediate section  38  supporting a plurality of first link ends  41  and a plurality of second link end  44 . The first link end  41  are disposed in the direction of belt travel indicated by arrow  32  and the plurality of second link ends  44  extend opposite the first link ends  41 . As will be described in detail hereinafter, the intermediate section  38  is comprised of an upper, transverse stiffening web  47  forming into a lower corrugated portion  50 . The corrugated portion  50  forms a series of ridges  53  and valley  56  in a sinusoidal manner. Along with the transverse web  47  of the intermediate section  38 , the ridges  53  extending toward the left of  FIG. 2  support the link end  41  while the ridges  53  extending toward the right in the drawing support the second link ends  44 . 
   The first link ends  41  include a leg portion  59  connected to an intermediate section  62  and extending to a distal head portion  65 . In a similar manner, the second link ends  44  include a leg portion  68  connected to the intermediate seccion  71  and extending to a distal head portion  74 . 
   With respect to the orientation shown in  FIG. 2  to  4 , the intermediate section  38  formed of the stiffening web  47  and the corrugated portion  50  is comprised of an upper surface  77  extending to and meeting with opposed left and right walls  80  and  83  which, in turn meet with a lower surface  86  of the module. The left wall  80  is comprised of an upper wall  89 , which is part of the stiffening web  47 , and extends downwardly to a curved wall  92  which forms into a lower vertical wall  95 . The curved wall  92  and the lower vertical wall  95  are part of the corrugated portion  50  of the intermediate section  38 . The lower vertical wall  95  extends to the lower surface  86  of the module which, is turn, extends to and meets with the right vertical wall  83 . 
   As shown in  FIG. 2 , the head portion  65  is preferably larger than the leg portion  59 . Accordingly, the head portion  65  is connected to the leg portion  59  by the angled intermediate section  62 . The head portion  65  is preferably formed with two substantially parallel sides  98  and  101  connected by an outer end  104 . The corners between the sides  98 ,  101  and ends  104  are preferably radiused to be smooth and to protect the conveyed product from damage. 
   An opening  107  is defined between spaced apart sides  110 ,  113  of adjacent link ends. At a distal end  116 , the ends of adjacent links form the mouth  119  of the opening  107 . At the opposite end  122 , the opening  107  terminates in the multi-level surface defined by the web  47  and corrugated portion  50  as described above. The top level of the surface (best shown in  FIG. 1 ) is defined by wall  89  of the web  47 . The corners where the side walls of the link ends  41  meet the straight wall  89  of web  47 , are also radiused to be smooth and to protect the conveyed product from damage. 
   In  FIG. 5 , the bottom level of the surface is defined by the relatively thin corrugated portion  50  having a pair of essentially parallel walls  125 ,  128 . The corrugated portion  50  forms the series of regularly spaced alternating ridges  53  and valleys  56  along the intermediate section  38 , as described herein. 
   Returning to  FIG. 2 , the straight wall  89  is shown bordering the opening  107 . The curved surface defined by corrugated portion  50  is shown in broken lines. The curved surface receives link ends from an adjacent belt module such that the belt  20  is capable of collapsing for movement around a curved path as described in detail herein. 
   The plurality of second link ends  44  extend from the belt module  26  in the opposite direction from the first link ends  41 . The second link ends  44  have the same overall shape as the first link ends  41  (except for last link end  45 ) and are designed to fit into the openings between the first link ends  41  such that adjacent belt modules can be intercalated and pivotally connected by the pivot rods  35 . 
   As shown in  FIG. 3 , the belt module  26  includes a slot  134  that is disposed through the link ends  41  transverse to the direction of belt travel. The slot  134  extends in the direction of belt travel such that it is generally oblong. The slot  134  receives the pivot rod  35 . The pivot rod  35  passes through the slots  134  in the first link ends  41  and through the openings  137  in the second link ends  44  (as shown in FIG.  1 ). The openings  137  correspond to the shape of the shaft  138  ( FIG. 1 ) of the pivot rod  35  such that the pivot rod  35  is received through the opening  137  but in contrast to slot  134 , the pivot rod  35  preferably cannot move in the direction of belt travel inside opening  137 . Due to the oblong shape of slot  134 , the pivot rod  35  can pivot inside the slot  134  such that the belt  20  is capable of collapsing on one side while the other side fans out due to the pivoting of rod  35  and the nesting of the link ends  41 ,  44  and cooperating spaces in the adjacent belt modules. 
   The last link end  45  of the belt module  26  includes a second opening  140  disposed around opening  137  to provide for countersinking a head (not shown) at the end of the pivot rod shaft  138 . 
   The back surface of the last link end  45  includes a rounded surface  143  that provides clearance for pivoting an adjacent link end  45 . 
   In  FIG. 4 , the transverse slot  134  in link ends  41  and the transverse opening  137  in link end  44  receive pivot rods  35  to connect adjacent belt modules  23  and  29  as shown in FIG.  1 . The web  47  is coterminous with the top surface  77  of the belt module  26  and terminates at the top of the corrugated portion  50  that defines the space between adjacent link ends (best shown in FIG.  5 ). 
   The outer ends  104  of the link ends  41  and  44  are radiused in a smooth rounded surface  146 . The rounded surface  146  preferably comprises a rounded surface having a constant radius and provides a driving surface for engagement with the drive sprocket  149  as described herein. 
   Also, the curvature of the outer ends  104  of the link ends enables the links to clear the web  47  when the adjacent modules collapse along the edge. The clearance enables the link ends to extend under the web  47  into the space defined by the corrugated portion  50  (best shown in FIGS.  6 - 7 ). In this manner, the web  47  partially hoods the link ends when the belt  20  collapses. Accordingly, the belt module  26  provides a web  47  for structural stability while maintaining a corrugated portion  50  to allow for recesses that provide maximum space for collapsing the belt modules around a curved path. 
   Turning to  FIGS. 8-11 , an alternate embodiment comprising belt module  200  is shown. Belt module  200  is suitable for center modules in a bricklayed belt. 
   The belt module  200  includes link ends  206 ,  207  which are supported by an intermediate section  208 . The link ends  206  have a slot  209  disposed transverse to the direction of the belt travel indicated by arrow  211 . Link ends  207  have a transverse opening  213  that corresponds to the shaft  138  of pivot rod  35 . 
   As shown in  FIG. 9 , the belt module  200  has a web  212  that is part of the intermediate section  208  and that is wider than the corrugated portion  50  of the edge module  26  shown in  FIGS. 1-7  (best shown in FIG.  5 ). In  FIG. 8 , the opening  218  between the link ends  206  is defined by a mouth  221  at one end  224  and is defined at the opposite end  227  by a multilevel surface defined by the web  212  and by a straight wall portion  230  that joins with the link end in a curved section  233 . 
   As shown in  FIGS. 10 and 11 , the bottom of the intermediate section  208  of the link ends is angled to provide a face  236  for engagement of the intermediate section  208  with the teeth  148  on the drive sprocket  149  (FIG.  14 ). The drive sprocket  149  is described in detail hereafter. 
   The link ends  207  have the transverse opening  213  capable of receiving the pivot rod  35 . Link ends  206  have the transverse slot  209  that is oblong and extends in the direction of belt travel such that the pivot rod  35  can move inside the slot  209  to pivot and facilitate collapsing. 
   The engagement of the face  236  on the central portion  215  with the tooth  148  on the drive sprocket  149  (shown in  FIG. 15 ) assists in maintaining engagement between the belt  20  and the drive sprocket  149  and assists in driving the belt  20 . The primary drive mechanism is described in detail below. 
   Turning to  FIGS. 12-13 , belt module  300  is an alternate embodiment of belt modules  23 ,  26 ,  29  of  FIGS. 1-7 . Belt module  300  differs from the previous modules because the slot and the holes are positioned off center on the link ends  303  and  306 , respectively. The transverse slot  309  and transverse openings  312  are located lower on the belt module  300  which provides for increased module strength. The distance  315  from the top surface  318  to the center  321  of the opening  312  is greater than the distance  316  from the center  321  of the opening  312  to the bottom surface  324 . Also, the link end  303  with the transverse slot  309  is designed such that the radius of curvature at the rounded end is greater above the slot  309  than is below the slot  309 . 
   As an option, the belt module  300  includes a plurality of openings  331  that provide for reducing the weight and material cost for the belt and provide open areas for clearing the belt. The vertical openings  331  in the link ends  306  are shown in  FIGS. 12 and 13 . 
   Turning to  FIGS. 14 and 15 , the belt modules  20  ( FIGS. 1-7 ) are shown driven by the teeth  148  on the drive sprocket  149 . The drive sprocket  149  is center driven by a rotating shaft (not shown) as known to those of ordinary skill in the art. The teeth  148  engage with the rounded surface  146  on the outside of the link ends and push the link ends, the central portions  215  ( FIG. 15 ) of the middle modules push against the teeth along the angled face  236 . 
   While the invention has been described in connection with certain preferred embodiments, it is not intended to limit the scope of the invention to the particular form set forth, but, on the contrary, it is intended to cover such alternatives, modifications, and equivalents as may be included within the spirit and scope of the invention as defined by the appended claims.