Abstract:
A modular conveying system with sprockets engaging the modules such that they do not cover any link gaps but are positioned between the link gaps. The module is characterized by link structures having link pairs that are spaced apart sufficiently at a distance to allow the sprockets to be located between the link pairs. Positioning the sprockets between the link pairs leaves the hinge gaps uncovered and thus allows free access to the hinge gap for cleaning.

Description:
FIELD OF INVENTION 
     The present invention relates to conveying systems, and specifically to modular conveying belts. 
     BACKGROUND OF THE INVENTION 
     Modular belts, e.g., flat top belts, are widely used for applications where food is transported in direct contact with the belts. Belts and equipment for such transport must be regularly cleaned in order to avoid contamination due to contact of the food with decomposed residual matter or bacteria. Cleanability is therefore an important requirement for modular belts and efforts have been made to improve cleaning, to reduce cleaning time, and to reduce costs associated with cleaning. 
     Modular belts are assembled from individual modules linked by hinges to form a conveyor belt. The modules are typically made from solid plastics with a smooth surface. The plastic material is selected from materials that are approved for direct contact with foodstuff. These types of plastic modules are normally well cleanable. The main problem associated with cleaning occurs in the hinge area where the individual modules are linked together. The hinge area typically has gaps where foodstuff penetrates and may become trapped. These deposits of residual food matter are difficult to remove. In addition, the cleaning problem is often made worse by sprockets that are driving the belt. The sprocket teeth may press the residual food matter into the hinge area where it can become trapped and difficult to remove. 
     A modular conveying belt used in the food industry is shown in U.S. Pat. No. 4,925,016. In order to drive the conveying belt, a transverse rib is arranged on the underside of the module bodies. The rib is disposed transverse to the conveying direction. The conveying belt is driven by a plurality of parallel, spaced-apart toothed drive wheels that have drive teeth that are positioned against the transverse ribs. Guide teeth are provided on the toothed drive wheel in addition to the drive teeth. The guide teeth engage in the gap between two adjacent link ends of interengaging modules and thus guide the modular conveying belt laterally. This conveying apparatus has the disadvantage that the toothed drive wheels have guide teeth in addition to the drive teeth. Also, the additional guide teeth make cleaning more difficult, and there is a risk of conveyable articles passing onto the underside of the conveying belt and being pressed by the guide teeth into the narrow interspace between two adjacent link ends. 
     An improved design has been proposed by U.S. Pat. No. Re 38,607, assigned to Habasit AG, the assignee of the present invention. Although the problem of the additional tracking teeth was eliminated and thus the cleanability improved, these sprockets still cover the hinge area and therefore may hinder the accessability of cleaning fluid to the hinge gaps. The contact of the hinges with the sprocket teeth is needed in order to allow the belt to be tracked by the sprocket. Also, the sprocket is kept aligned with a certain position of the belt so that the proper engagement of the sprocket teeth with the hinge structure is maintained. Accordingly, there is a need for an improved system that maintains proper sprocket engagement yet allows for exposure of the hinge area for cleaning. 
     SUMMARY OF THE INVENTION 
     The present invention meets the above-described need by providing a conveying system with sprockets positioned such that they do not cover any link gaps but are positioned in between them. The present invention provides for this arrangement by means of a special hinge design characterized by link structures having link pairs, that are spaced apart sufficiently at a distance to allow the sprockets to be located between the link pairs. Positioning the sprockets between the link pairs leaves the hinge gaps uncovered and thus allows free access to the hinge gap for cleaning. In order to provide belt tracking, the center transverse rib may be shaped such that the engaged sprockets cannot move sideways (transversal to the belt running direction), the transverse rib may be provided with at least one protuberance for tracking, or the sprocket may be fixed to the shaft in combination with edge guiding of the belt or the like. 
    
    
     
       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. 1A  is a top plan view of a portion of a belt according to the present invention; 
         FIG. 1B  is a bottom plan view of the belt of  FIG. 1A  with a conventional transverse rib; 
         FIG. 2A  is a bottom plan view of the typical prior art sprocket engagement over the hinge area; 
         FIG. 2B  is perspective view of the sprocket and belt show in  FIG. 2A ; 
         FIG. 2C  is a side elevational view of the sprocket and belt shown in  FIG. 2A ; 
         FIG. 3  is a bottom plan view of a module according to the present invention; 
         FIG. 4  is a bottom plan view of an alternate embodiment of the module according to the present invention; 
         FIG. 5  is a bottom plan view of another alternate embodiment of the module according to the present invention; 
         FIG. 6  is a perspective view of the sprocket engaged on the center transverse rib between the links of the hinges leaving the link gaps freely accessible for cleaning; and, 
         FIG. 7  is a bottom plan view showing two sprockets located between the link pairs such that the hinge area is exposed for cleaning. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In  FIG. 1A , a portion of a belt  9  is shown. A first module  10  is designed for easy cleaning with a closed flat top surface  13 . Also, the number of link ends is reduced to reduce the number of hinge areas. A second module  16  is intercalated with the first module  10 . The modules  10 ,  16  extend from a first side edge  19  to a second side edge  22  in a transverse direction indicated by arrow  25 . The modules  10 ,  16  comprise an intermediate section  12 . As shown, the modules are assembled as chains with the modules  10 ,  16  extending the full width of the belt  9 . As will be evident to those of ordinary skill in the art based on this disclosure, the chain configuration eliminates the gaps between modules that are present when the belt  9  is assembled in a bricklayed configuration with several modules in each row. The modules  10 ,  16  are end-to-end reversible. Alternatively, they can be designed as unidirectional. The conveying direction is indicated by arrow  28 . Each belt has a leading edge  31  and a trailing edge  34 . The edges  31 ,  34  have alternating openings  37  and protrusions  38  that define the shape of the edges  31 ,  34 . The protrusions  38  comprise a plate  46  ( Fig. 1   b ) that connects first link ends  40 ,  43  which extend from the intermediate section  12  in the same direction as described below. The protrusions  38  of module  10  fit into the openings  37  of adjacent module  16  when the modules  10 ,  16  are intercalated. 
     Turning to  FIG. 1B , the modules  10 ,  16  of the present invention are shown with a standard transverse rib  41  for conventional sprocket engagement. The first link ends  40 ,  43  are disposed in pairs connected by the plate  46 . The plate  46  has a top surface  49  ( FIG. 1A ) that is coplanar with the surface  13 . The number of first link ends  40 ,  43  is reduced to reduce the number of gaps to be cleaned. The arrangement of the first link ends  40 ,  43  in pairs as shown provides for reducing the number of link ends  40 ,  43  while maintaining sufficient belt strength. Second link ends  44 ,  45  extend in the opposite direction from first link ends  40 ,  43  and are connected by a plate  47 . As best shown in  FIG. 2   a , when the adjacent modules are intercalated a first link end  40  is disposed adjacent to a second link end  45  on the adjacent module with minimal transverse distance A between them. Each of the modules  10 ,  16  has the center transverse rib  41  for stiffening the belt  9  and at the same time allowing a driving sprocket  55  ( FIGS. 2   a - 2   c ) to be engaged to submit the driving torque. The bottom surface  58  of the module  31  is flat for easy cleaning. 
     In  FIGS. 2   a - 2   c , the engagement of the sprocket  55  with the belt  9  in the known manner is shown. The sprocket  55  engages with the belt over the hinge area where the adjacent link ends  43 ,  44  are located. The sprocket teeth  56 ,  57  abut against the side faces  61  of the links to provide tracking. Accordingly, when the belt  9  passes over the sprocket  55 , the hinge gaps are covered, accessibility for cleaning is hindered, and the sprocket teeth  56 ,  57  may press food in to the hinge gaps where it is difficult to remove. The first link ends  40 ,  43  have transverse pivot rod openings  60 ,  63  for receiving a pivot rod  66  when adjacent modules are intercalated and the transverse openings  60 ,  63  are placed in alignment. As shown in  FIG. 2   b , the sprocket  55  has a central opening  69  for receiving a shaft (not shown). The opening  69  is square but other shapes may also be suitable. The engagement of the sprocket tooth  56  with link end  45  for tracking is shown at the bottom center portion of  FIG. 2   b . Turning to  FIG. 2   c , the engagement of the sprocket teeth  56 ,  57  with rib  41  is best shown. 
     In  FIG. 3 , the bottom surface  103  of a module  100  according to the present invention is shown. The bottom surface  103  may be substantially smooth and flat for cleaning purposes. The module  100  has a leading edge  106  and a trailing edge  109 . The module  100  may be formed in different widths depending on the size of the belt and whether the belt is formed like a chain or is bricklayed. First link ends  114  and  115  extend in a first direction. The first link ends  114  and  115  are connected by a plate  118  to form a first link structure  121 . The link ends  114 ,  115  have transverse pivot rod openings  116 ,  117  for receiving a pivot rod  160  ( FIG. 6 ). A plurality of first link structures  121  extend along the leading edge  106 . Openings  124  are disposed between each successive link structure  121 . A second plurality of link ends  124 ,  127  extend opposite the first link ends  114 ,  115  and are connected by a plate  129 . Second link ends have transverse pivot rod openings  132 ,  134 . The module  100  has a center transverse rib  130  that is corrugated between the link pairs. The corrugated section  139  has alternating peaks  131  and valleys  134  in positions between the link ends  114 ,  115  through the middle of the link structure  121 . The corrugated section  139  allows for positioning of the sprocket  55  between the sets of adjacent link ends  114 ,  115  such that the hinge area remains open for cleaning access. Tracking is provided by engagement of the sprocket teeth  56 ,  57  with the rib corrugation  139 . The rib  130  provides for engagement of the sprocket  55  in between the link ends  114 ,  115  of the link structure  121  and therefore away from the hinge gaps where first and second link ends from intercalated modules are disposed adjacent to each other. As shown in  FIG. 3 , the sprocket teeth  56 ,  57  engage with the rib  130  and the guiding function is provided by the corrugated section  139  that engages with the teeth  56 ,  57 . 
     In  FIG. 4 , an alternate embodiment of the transverse rib is shown. The transverse rib  175  is approximately sinusoidal in shape with alternating peaks  178  and valleys  180 . One of the teeth engages the rib  175  in a valley and the two sides of the rib  175  bordering the valley engage the sides of one of the sprocket teeth to provide for guidance. 
     In  FIG. 5 , another embodiment of the present invention is shown. A central rib  190  has at least one protuberance  193  that engages with the sprocket teeth to provide guidance for tracking. 
     It is also possible to have tracking from the edge of the belt. With a straight transverse rib as shown in  FIG. 1B , the sprocket  55  may be fixed to a shaft  456  ( FIG. 6 ) in combination with edge guiding of the belt or the like, as will be evident to those of ordinary skill in the art based on this disclosure, to maintain alignment of the sprockets  55  in the middle of the link structures. 
     In  FIGS. 6-7 , a belt  200  is shown with modules  100  having transverse ribs  130 . As best shown in  FIG. 7 , the sprocket  55  engages the belt modules  100  away from the hinge gap areas  210  where first and second link ends  114 ,  127  from adjacent modules  100  are disposed adjacent to each other on opposite sides of the pivot rod  160 . The sprocket  55  is positioned such that it engages the modules  100  in the midportion of the first link structure  121  between the first link ends  114 ,  115 . Accordingly, the hinge gap areas are not covered by the sprocket  55  and are more accessible for cleaning. 
     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.