Abstract:
A pivot rod that is formed by overmolding the end of a grooved rod with a plastic head. The pivot rod may be formed out of shear resistant materials such as steel or the like. Alternatively, a headed rod may be formed by overmolding a highly shear resistant, reinforced extruded plastic rod with a plastic ring or head of a moldable compound.

Description:
FIELD OF THE INVENTION 
       [0001]    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 INVENTION 
       [0002]    Because they are lightweight, do not corrode, and are easy to clean, unlike metal conveyor belts, plastic conveyor belts are used widely. 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 or slots 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. 
         [0003]    Headed pivot rods may be used for joining belt modules. There are many versions available in the market including snap-fit retaining versions such as shown in U.S. Pat. Nos. 5,181,601 and 5,645,160, which are incorporated herein by reference. Another system is the Habasit Smart Fit system as disclosed in U.S. Pat. No. 7,108,127, which is also incorporated herein by reference. The pivot rods are typically manufactured from plastic that is molded or extruded with thermoformed heads and/or retaining rings integrally formed thereon. These rod heads and retaining rings function well for rod retaining and provide for ease of assembly and disassembly. These systems work well for all applications where the loads on the belts are moderate. For conveyors where very high loads need to be conveyed, “heavy duty” plastic belts with pivot rods of 10 mm diameter or greater are typically used. The modules for heavy duty belts may reach a thickness of one inch or more. Typically in the automotive and paper (paper roll handling) industries, loads may reach a very high level where plastic pivot rods are not strong enough. To achieve the necessary strength, steel chains may be used instead of plastic chains. However, thick plastic modules are preferred since they need no lubrication and run more quietly and smoothly. In most of those cases the weak point is the shearing strength and elasticity of the plastic pivot rod. This problem may be solved by using steel rods to join the heavy duty plastic modules. Although it is possible to form the retaining ring on the steel rod directly, the process is expensive and inefficient. Accordingly, what is needed is an improved high strength pivot rod for use with heavy duty plastic modules. 
       SUMMARY OF INVENTION 
       [0004]    The present invention meets the above-described need by providing a pivot rod that is formed by overmolding the end of a grooved rod with a plastic head. The pivot rod may be formed out of shear resistant materials such as steel or the like. Alternatively, a headed rod may be formed by overmolding a highly shear resistant, reinforced extruded plastic rod with a plastic ring or head of a moldable compound. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWING FIGURES 
         [0005]    The invention is illustrated in the drawings in which like reference characters designate the same or similar parts throughout the figures of which: 
           [0006]      FIG. 1  is a cutaway perspective view of an overmolded rod of the present invention; 
           [0007]      FIG. 2  is a cutaway perspective view of a belt module containing the overmolded rod of the present invention; 
           [0008]      FIG. 3   a  is an elevational view of a first embodiment of the overmolded rod; 
           [0009]      FIG. 3   b  is another elevational view of the overmolded rod shown in  FIG. 3   a;    
           [0010]      FIG. 4   a  is an elevational view of a second embodiment of the overmolded rod of the present invention; 
           [0011]      FIG. 4   b  is another elevational view of the rod of  FIG. 4   a;    
           [0012]      FIG. 5  is an elevational view of another embodiment of the invention; and, 
           [0013]      FIG. 6  is a plan view of a portion of a modular belt formed with pivot rods according to the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0014]    Turning to  FIG. 1 , a pivot rod  10  may be constructed of a high strength material such as steel. Alternatively, a highly shear resistant, reinforced plastic rod may be used. Other materials with high shear strength and low elasticity such as composites or the like may also be suitable. A middle portion  13  of the rod  10  has a substantially constant diameter  14 . As best shown in  FIG. 3   a , the end portion  16  of the rod  10  has a profile  19  that is different than the middle portion  13 . The end portion  16  includes reduced diameter portions  22  and grooves  25  integrally formed in the rod. As shown, a cap  28  ( FIG. 3   b ) is molded onto the end of the rod. The cap  28  includes a retaining ring  31  and a head  34  which are shown in outline in  FIG. 3   a . The retaining ring  31  is used for snap rod retaining systems as will be evident to those of ordinary skill in the art based on this disclosure. The cap  28  includes a portion  37  between the ring  31  and the head  34 . The portion  37  has a diameter  38  that is approximately equal to the diameter  14  of the rod. The cap  28  is molded onto the end of the rod  10 . The plastic molding process will be evident to those of ordinary skill based on this disclosure. 
         [0015]    In  FIG. 2 , the rod  10  of the present invention is shown in position in a belt module  40 . The adjacent belt module has been removed for clarity. The belt module  40  has an intermediate section  43  with a first plurality of link ends  46  extending from the intermediate section  43  in a first direction and a second plurality of link ends  49  extending from the intermediate section  43  in a second direction. The first link ends  46  and the second link ends  49  are offset from each other and have spaces  50  defined between successive link ends. As a result, the first plurality of link ends  46  of a first module  40  fit into the spaces  50  between the second plurality of link ends  49  of an adjacent module  40 . The link ends  46 ,  49  have transverse pivot rod openings  52 . The pivot rod openings  52  in the respective link ends  46  and  49  are capable of aligning when the link ends  46 ,  49  are intercalated. The pivot rod  10  fits into the aligned pivot rod openings  52  to connect one row of modules  40  to an adjacent row. The modules  40  may be connected in bricklayed fashion and the adjacent rows of modules  40  form an endless belt that is capable of articulating about a sprocket (not shown). The retaining ring  31  provides for installation of the pivot rod  10  into the belt from one end and prevents the pivot rod  10  from sliding out of the belt after it is installed. 
         [0016]    In  FIGS. 3   a  and  3   b , the embodiment shown in  FIG. 1  is shown in greater detail. The pivot rod  10  has an approximately constant diameter  14  from the mid portion  13  of the rod  10  toward the end  16 . At a point  60  spaced apart from the end  16 , the diameter of the pivot rod  10  is stepped down to a second diameter  63  that is less than the diameter  14  of the midportion  13  of the rod  10 . In the reduced second diameter  63  section, there are a plurality of grooves  25  defined therein. The grooves  25  shown in  FIG. 3   a  are square however other shapes may also be suitable. The square grooves  25  have opposed side walls  66  and a bottom wall  69 . The grooves  25  extend along the reduced diameter  63  from position  60  where the ring  31  is formed toward the end  16  of the rod  10  where the head  34  is located. The grooves  25  extend to a wider section  72  ( FIG. 3   a ) located at the distal end  16  of the rod  10 . The overmolded cap  28  includes the retaining ring  31  which has a diameter  29  wider than the diameter  14  of the rod  10 . The leading edges  75 ,  78  of the retaining ring  31  may be angled to provide for easier insertion through the transverse pivot rod openings  52 . Beyond the retaining ring  31 , the cap  28  has a diameter  38  that is approximately equal to the diameter  14  of the pivot rod  10  in the midportion  13 . The section  37  having the same diameter as the midportion  13  extends to the head  34  which has a larger diameter  29 . When the pivot rod  10  is installed in a belt, the outermost link end fits between the retaining ring  31  and the head  34 . 
         [0017]    Turning to  FIGS. 4   a  and  4   b , the present invention may also be used to form a “headless” rod where the end of the rod  90  has the same diameter as the midportion. The pivot rod  90  shown in these figures includes a retaining ring  93  but does not include an oversized head at the distal end of the rod  90 . The rod  90  has a groove  96  near the end  97  for rod extraction. Because the retaining ring  93  provides for rod retention, an oversized head is not required. As shown in  FIG. 4   a , the pivot rod  90  also has a midportion  99  with a first diameter  102 . Toward the end  97  of the rod  90 , the rod steps down to a second diameter  108  and a series of square grooves  111  are formed. The grooves  111  extend to a section  114  with a diameter  115  equal to the diameter  102  of the midportion  99 . This section  114  is spaced apart from the distal end  97  of the rod  90  which also has a diameter equal to the diameter  102  of the midportion  99 . The groove  96  near the end  97  provides a space for receiving a screw driver or the like for extracting the pivot rod  90  from a belt for disassembling the belt. 
         [0018]    Turning to  FIG. 5 , an alternate embodiment of the invention includes a pivot rod  200  having smooth side walls  203  with a substantially constant diameter  206  through the middle portion  209 . Toward the distal end  207 , there is a reduced diameter  212 . The distal end  207  has the same diameter  206  as the midportion  209  of the rod  200 . The reduced diameter  212  provides a gap  219  that may be used for manual extraction of the pivot rod  200  for disassembling of the belt. 
         [0019]    A retaining ring  223  is formed by heat shrinking a ring  223  onto the outside of the pivot rod  200  at a position spaced apart from the distal end  207  of the pivot rod. The ring  223  is formed of steel capable of heat shrinking. The rod  200  may also be constructed of steel and may be formed without grooves. The retaining ring  223  is installed by heating the ring  223 , shifting it over the rod  200 , and then cooling the metal ring  223  such that it contracts or shrinks around the pivot rod  200  to become firmly fixed to the rod  200 . 
         [0020]    Turning to  FIG. 6 , a modular belt  299  is constructed with a plurality of modules  300 . The modules have a plurality of first link ends  309  and a plurality of second link ends  312  extending in opposite directions from an intermediate section  304 . The link ends  309 ,  312  are spaced apart and offset to form openings  315  such that the link ends  309  of an adjacent module  300  fit into the openings  315  between the link ends  312 . The link ends  309 ,  312  have transverse pivot rod openings  305  that are capable of aligning to receive the pivot rod when the link ends of adjacent modules are intercalated. The pivot rods  10 ,  90 , and  200  may be used to connect adjacent rows of modules  300  to form an endless belt capable of pivoting such that the belt can traverse a sprocket.