FIELD OF THE 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 
   Modular belts and particular flat top modular belts are widely used for the transport of foodstuff with direct contact of the foodstuff with the conveying surface of the belt. Belts and equipment for such transport must be regularly cleaned in order to avoid contamination of the food with decomposed residual matters and bacteria. 
   The modules are usually constructed from plastics that are approved for direct contact with foodstuff. The modules typically have a closed, smooth surface that cleans well. The main area of difficulty is the hinge where the modules are connected together. The hinges typically have gaps where foodstuff can penetrate and become trapped. These residual deposits of foodstuff are difficult to remove. In order to address this problem, there have been designs that provide conical gaps that open when the belt modules move around a sprocket. One such design is shown in U.S. Pat. No. 6,725,883 which is assigned to the assignee of the present invention. Another design is shown in U.S. Pat. No. 5,706,934. These belt designs are further characterized by a smooth flat bottom side that is only interrupted by the links needed to connect the modules to form a belt. In most cases this type of belt is used in a bricklayed assembly of more than one module per module row. These bricklayed belts have small gaps where the module ends meet. In order to eliminate these gaps and as a further improvement in cleanability long modules were used to form a chain-like belt and to eliminate the bricklayed arrangement completely as shown in U.S. Pat. No. 6,758,329. Although the gaps between the module ends are eliminated, these long modules still suffer from a large number of gaps between the equally spaced interdigited links and therefore there was still room for improvement. A further improvement is possible by eliminating some of the links and therefore reducing the number of gaps between the side of the interdigited links. This design offers even better cleanability due to less hinge links but results in low belt strength. The strength reduction is not only caused by the reduction of the number of load transmitting links, but also by the large distance between links. The risk with such a design is the hinge pin, usually made from plastic, being bent between the wider, equally-spaced links and if under load (tension) results in a very flexible and less stable belt. Accordingly, there is a need for a belt module that improves cleanability while maintaining good belt strength. 
   SUMMARY OF THE INVENTION 
   The present invention meets the above described need by providing a module that reduces the undesirable elasticity of the belt under load by having link pairs that are moved as close together as possible leaving large open spaces between the link pairs. 


   
     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 perspective view of a belt module according to a first embodiment of the present invention; 
       FIG. 2  is a top plan view of a portion of a belt formed from the module shown in  FIG. 1 ; 
       FIG. 3  is a bottom plan view of the belt of  FIG. 2 ; 
       FIG. 4  is a perspective view of a portion of the belt as it bends around a sprocket; 
       FIG. 5  is another perspective view of a portion of the belt as it bends around a sprocket; 
       FIG. 6  is an enlarged detailed view taken from  FIG. 3 ; 
       FIG. 7  is an enlarged bottom perspective view of a portion of the belt of the present invention; 
       FIG. 8  is a bottom plan view of the belt of the present invention when the top conveying surface is flat; 
       FIG. 9  is a bottom plan view of the belt of the present invention as it bends around a sprocket; 
       FIG. 10A  is a cross-sectional view taken along lines  10 - 10  of  FIG. 8 ; 
       FIG. 10B  is an alternate embodiment of the belt of  FIG. 10A ; 
       FIG. 11  is a cross-sectional view taken along lines  11 - 11  of  FIG. 9 ; 
       FIG. 12  is a perspective view of a belt module according to a second embodiment of the present invention; 
       FIG. 13  is a perspective view of a belt formed from the module of  FIG. 12 ; 
       FIG. 14  is another perspective view of the belt shown in  FIG. 13 ; 
       FIG. 15  is a bottom plan view of belt of the present invention as it bends around a sprocket; 
       FIG. 16  is an enlarged view of a portion of the belt shown in  FIG. 15 ; 
       FIG. 17  is a partial bottom plan view of an alternate embodiment of the link ends of the present invention; 
       FIG. 18  is a top plan view of a belt according to another embodiment of the present invention; 
       FIG. 19  is a bottom plan view of the belt of  FIG. 18 ; 
       FIG. 20  is a bottom plan view of an alternate embodiment that is not end-to-end reversible; 
       FIG. 21  is an end view of the belt of  FIG. 18  in a straight-running, closed configuration; 
       FIG. 22  is an end view of the belt when it moves around a sprocket; 
       FIG. 23  is an enlarged bottom plan view of the belt in the flat horizontal position; 
       FIG. 24  is an enlarged bottom plan view of the belt in an angled position when the belt is moving around a sprocket or drum; and 
       FIG. 25  is an enlarged view of a portion of  FIG. 23 . 
   


   DETAILED DESCRIPTION OF THE INVENTION 
   In  FIG. 1 , a belt module  20  of the present invention has an upper conveying surface  23  that is generally smooth and flat. The upper conveying surface  23  extends from a first side edge  26  to a second side edge  29  in a direction transverse to the direction of belt travel indicated by arrow  32 . The upper conveying surface  23  also includes a first edge  38  and a second edge  41  disposed opposite from the first edge  38 . The shapes of the first and second edges  38  and  41  are defined by a plurality of link ends and openings. The first edge  38  has a first portion  39  extending in a direction transverse to the direction of belt travel. The first portion  39  extends to a first link end  44 . The link end  44  forms a portion of the upper conveying surface  23  and also has a rounded end portion  47 . The first link end  44  has a pair of side walls  50  and  53  defining a transverse thickness. On the side of the link end  44  adjacent to side wall  53  there is an elongate opening  56  in the conveying surface  23 . The opposite end of the opening  56  is bordered by another link end  44  having a pair of side walls  50  and  53  defining a transverse thickness. The link ends  44  have transverse pivot rod openings  56  ( best shown in  FIGS. 10-11 ) for receiving a pivot rod  59  to pivotally connect adjacent modules to form a belt  100  as shown in  FIG. 2 . On the side of the module  20  opposite from link end  44  a corresponding opening  45  is provided. When adjacent modules  20  are intercalated as shown in  FIG. 2 , link ends  44  fit into openings  45 . 
   The belt module  20  also includes a link end  65  having a plate  68  extending therefrom. The link end  65  and plate  68  have a width that is slightly smaller than the elongate opening  56  such that adjacent modules  20  are capable of being intercalated and connected by a pivot rod  59  to form a belt  100  capable of articulating around a sprocket (not shown). The belt module  20  also includes a link end  70  that is connected to a wider plate  72 . The link end  70  and the wider plate  72  fit into an opening  75  in an adjacent module  20  as shown in  FIGS. 2 and 3 . 
   Turning to  FIG. 2 , the belt  100  may be formed by intercalating adjacent modules  20 , aligning their transverse pivot rod openings  56  ( FIG. 3 ), and inserting a pivot rod  59  ( FIG. 3 ), as known to those of ordinary skill in the art based on this disclosure. The belt  100  forms a closed top surface with very minimal gaps to prevent foodstuff from becoming trapped between the belt modules  20 . The link ends  44 ,  65 , and  70  on one side of the belt module  20  intercalate with the corresponding openings  45 ,  69 , and  75 , on the opposite side of an adjacent belt module  20 . 
   In  FIG. 3 , the bottom of belt  100  is shown. A longitudinal rib  101  is formed on the bottom surface  103 . In order to reduce the undesirable elasticity of the belt under load the link ends are positioned as close together as possible. The target is to reduce the transversal distance B to a minimum. This configuration of the link ends concentrates the shearing forces on the pivot rod  59  into two planes with a very small distance B between them and thus avoids rod bending and reduces belt elasticity. However, the link gap A of the two adjacent links must remain large enough to allow for easy cleaning. The link gap A is created by an angled shaping of the link ends. The gap A between the links is formed by the opposed side walls  106 ,  109  on adjacent link ends being substantially parallel to each other and disposed at an angle β with respect to the other side wall  112 ,  115  on each link end. Preferably β is approximately 20 degrees. When the belt  100  moves around a sprocket or drum (not shown), the hinged link ends will rotate around the pivot rod  59  and the hinge gap A will increase releasing any trapped residual matters. The bigger the angle β the more the gap A will increase. The side wall  112 ,  115  opposite to the angled side wall  106 ,  109  may be parallel to the direction of belt travel or alternatively may be angled as well as discussed herein. The configuration of the opposite side wall allows for optimization of the link shape to keep sufficient link thickness S at the rearward link end. 
   From the center cross rib to the leading and trailing edges  38 ,  41  of the belt  100 , the underside of the module  20  may be flat or it may be provided with a plate-like surface (best shown in  FIGS. 10A and 11 ) that slopes away in the direction of belt travel ending at the belt edge between the link ends. As shown in  FIG. 10A , the plate-like portion  110  of the module  20  may define a smooth and slightly concave back surface continuing across the module in the direction of belt travel. 
   Turning to  FIGS. 4-5 , when the belt  100  travels around a sprocket or drum, a gap  120  is formed between the edges of adjacent modules  20 . The gap  120  provides access to the hinge area for cleaning when the belt  100  travels over the sprocket. 
   In  FIG. 6 , the module pitch P is the distance between the same point on adjacent modules  20  in the direction of belt travel. The link pitch C is the largest distance between the same point on two adjacent link ends. In order to reduce the number of link ends and therefore reduce the number of gaps, the link pitch C may be greater than or equal to the module pitch P. The gap  120  is at its maximum width when the belt  100  is positioned as shown in  FIG. 6 . In  FIG. 6 , the belt  100  is rotated around the pivot rod  59  when the belt  100  is turning around a sprocket or drum. The hinge gap A is enlarged due to the bending of the belt  100  around the sprocket. 
   In  FIG. 7 , a bottom perspective view is shown. The longitudinal rib  101  extends from the bottom surface  103  of the module and provides a point of engagement for the teeth of the sprocket (not shown). The longitudinal rib  101  has a top wall  123  and a pair of side walls  126 ,  129  extending from opposite sides of the top wall  123 . The side walls  126  and  129  extend toward the bottom wall  103  of the module  20 . As shown the side walls  126  and  129  intersect with the plate-like portion  110  in a smooth curve that extends from the rib  101  toward the link ends. As an alternative, the side walls  126  and  129  may extend to the bottom surface  103  of the module  20  which may be flat between the base of the rib  101  and the link ends as shown in  FIG. 10B  and as known to those of ordinary skill in the art based on this disclosure. 
     FIG. 8  shows the bottom of the belt  100  when the top conveying surface  23  of the belt  100  is closed. When the belt  100  is travelling along a straight path, the gaps between adjacent modules  20  are minimized and the gaps where foodstuff could pass through the belt surface are minimized. The opposed side walls of the link ends on adjacent modules define the hinge gap A which increases when the belt travels around a sprocket as shown in  FIG. 9 . 
   As shown in  FIG. 10A , the side walls  126 ,  129  of the longitudinal rib  101  intersect with plate-like portions  110  that extend toward the link ends along a curved path. The pivot rod openings  56  may be provided with an oblong shape with pivot rod openings  56  on opposite sides of the modules being oriented at equal and opposite angles. As a result, a gap is created around the pivot rod to facilitate cleaning. As shown in  FIG. 11 , the gap widens as the belt passes over the sprocket.  FIG. 10B  shows an alternate embodiment of the invention with a standard rib  178  having side walls  172  and  174 , a top wall  179  and extending to a flat bottom surface  170 . 
   In  FIGS. 12-16 , an alternate embodiment of the present invention is shown. Belt module  200  has a first side edge  201  and a second side edge  202 . A top conveying surface  205  extends between the side edges  201 ,  202 . A first plurality of link ends  203  extend from the conveying surface  205  in the direction of belt travel indicated by arrow  215 . A second plurality of link ends  209  extend in the opposite direction. The first plurality of link ends  203  fit into the spaces between the second plurality of link ends  209  on the adjacent module  200 . Belt module  200  has plate-like extensions  207 ,  220  extending from the sides of the link ends  203 ,  209  with an edge  208 ,  213  that is sized to extend approximately halfway between neighboring link ends  203 ,  209  creating a staggered gap when the belt  250  runs around a sprocket. The transversal width W of the edge  208  may of course also be another percentage of the distance between link ends  203 . The cleaning properties remain the same for this version, but it may be of advantage for molding and load distribution to the link ends. Link ends  227 ,  229  are located at or near the side edges  201 ,  202 . 
   The center cross rib  230  may be in the center axis of the modules equally spaced to the transverse pivot rod openings  235  or may be offset to either side. The cross rib  230  serves for engagement of sprockets to drive the belt. Further it stiffens the link connection to the module and may better accommodate the impact of heavier loads to be conveyed. 
   In  FIGS. 13-14  a belt  250  constructed of modules  200  connected by pivot rods  254  is shown as it travels around a sprocket (not shown). Gaps  255  open between the plate-like extensions  207 ,  220  and the openings between adjacent link ends  203 ,  209 . 
   Turning to  FIGS. 15-16 , a longitudinal rib  270  is formed on the bottom surface  273 . In order to reduce any undesirable elasticity of the belt under load the link ends are positioned as close together as possible. The target is to reduce the transversal distance B to a minimum. This configuration of the link ends concentrates the shearing forces on the pivot rod  254  in two planes with a small distance B between them and thus avoids rod bending and reduces belt elasticity. However, the link gap of the two adjacent links must remain large enough to allow for easy cleaning. The link gap A is created by an angled shaping of the link ends. The gap A between the links is formed by opposed side walls  280 ,  283  on adjacent link ends being substantially parallel to each other and disposed at an angle β with respect to the other side wall  287 ,  288  on each link end. Preferably β is approximately 20 degrees. When the belt  250  moves around a sprocket or drum (not shown), the hinged link ends will rotate around the pivot rod  254  and the hinge gap A will increase releasing any trapped residual matters. The greater the angle β the more the gap A will increase. The side wall  287 ,  288  opposite to the angled side wall  280 ,  283  may be parallel to the direction of belt travel or alternatively may be angled as discussed herein. The configuration of the opposite side wall allows for optimization of the link shape to keep sufficient link thickness S at the rearward link end. 
   In  FIG. 17 , an alternate embodiment is shown with the link ends being shaped such that all of the side walls  292 ,  294 ,  296 , and  298  are disposed parallel to each other. By arranging the side walls in this fashion the thickness T of the link end is maintained uniform on the bottom surface. 
   Turning to  FIGS. 18-25 , another embodiment of the invention is shown. In  FIG. 18 , a pair of end-to-end reversible modules  300 ,  301  are shown. Such modules may be used as chains, particularly in wider width, in order to eliminate the gaps between the modules in the same row of a bricklayed belt. Alternatively, modules  300 ,  301  may be used to build bricklayed belts. The modules  301 ,  302  have a closed top surface  308  extending from a first side edge  307  to a second side edge  309 . A leading edge  311  includes alternating transverse portions  314  and openings  317  for receiving the transverse portions of adjacent modules. The trailing edge  320  includes a recessed portion  323  leading to successive transverse portions  314  and openings  317 . Extending from the trailing edge  320 , link ends  303  and  306  are disposed in pairs connected by a plate  390 . Extending from leading edge  311 , link ends  304  and  305  are connected by a plate  393 . The plates  390  and  393  are elongate and have a top surface  394  that is coplanar with top surface  308  of the modules  300 ,  301 . Accordingly, the plates  390 ,  393  are supported at both sides by the link ends. This arrangement provides the plates  390 ,  393  with greater impact resistance. The modules  300 ,  301  may be provided with a longitudinal rib  318  ( FIG. 19 ). 
   To reduce the undesirable elasticity of the belt under load, widely spaced single links are avoided. Instead the link ends  303 ,  305  on adjacent modules  300 ,  301  ( FIG. 19 ) are moved as near together as possible. A large space  312  is left open between the pairs. The target is to reduce the transversal distance b to a minimum, i.e., ideally near zero, as shown in  FIG. 25 . This configuration concentrates the shearing forces on the pivot rod  330  into two planes with a very small distance b between them, and thus avoids rod bending and reduces belt elasticity. However, the link gap A ( FIGS. 23-24 ) of the neighboring or adjacent links  303 ,  305  of interconnected modules  300 ,  301  must remain large enough to allow easy cleaning. This feature is achieved by a very specific angled shaping of the links. The gap between the links are in an angle β in a generally parallel relationship as shown in  FIG. 25 . Preferably this angle is at least 20 degrees. As shown in  FIG. 24 , when the belt moves around a sprocket or drum (not shown), the hinged links will rotate around the pivot rod  330  and the hinge gap A will increase, releasing any trapped residual matter. The larger the angle β, the more the gap A will increase. The link face  335  opposite to the angled face  340  may be parallel to the running direction of the belt as discussed above in connection with  FIG. 16  or alternatively may be angled as well as best shown in  FIG. 25 . This variation provides for optimizing the link shape to keep sufficient link thickness S at the rearward link end  360 . From the point where the rear end  360  of the links are joining into the module plate, the back surface  355  slopes away in the running direction of the belt ending in between the links at the edge  365 . This plate-like portion of the module defines a smooth and slightly concave back-surface  355  allowing the best possible access to inspection and cleaning of the exposed rods  330 . The edges  365  meeting with the adjacently linked module body are shaped to open a gap A when the belt moves around a sprocket or drum for access of the cleaning fluid and easy removal of residuals collected in the hinge area. 
   In  FIG. 20 , an alternate embodiment of the module that is not end-to-end reversible and therefore cannot be bricklayed is shown. A pair of modules  400 ,  401  having link ends  403 ,  406  and  409 ,  412 , respectively are connected by a pivot rod  415 . The link ends are disposed in pairs as described above when the modules are connected and the link ends are intercalated. 
   While the invention has been described in connection with certain embodiments, it is not intended to limit the scope of the invention to the particular forms 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.
A belt designed for improved cleanability achieved by large link distances thus reducing the number of gaps. The module design reduces the undesirable elasticity of the belt under load by having link pairs, formed by links on adjacent modules, that are moved as close together as possible leaving large open spaces between the link pairs.