Abstract:
AD overhead conveyor, components therefor and method for making same, in which the conveyor chain has a nominal pitch “X,” bit a maximum allowable chain pull value which is equal to or greater than the maximum allowable chain pull value for a chain having a nominal pitch of X+1. Trolleys can be attached to the chain at intervals which differ from the intervals of a chain with pitch of X+1. Fewer synchronized drives are required for driving longer chains. A lower pitch chain can be used to drive larger trolleys, without sacrificing the maximum allowable chain pull value always used in conjunction with the larger trolley.

Description:
CLAIM OF PRIORITY 
       [0001]    This application claims priority to U.S. Provisional Application Ser. No. 61/723,482, filed Nov. 7, 2012, entitled HIGH LOAD CONVEYOR CHAIN AND METHOD. 
     
    
     FIELD AND BACKGROUND OF THE INVENTION 
       [0002]    The present invention relates to overhead conveyors, which typically comprise at least an “I beam” track, trolleys which have opposed wheels engaging the bottom flanges of said I beam track on opposite sides of the center web of the beam, and a driven conveyor chain connected to said trolleys at spaced intervals. The chains usually comprise center links alternating with a pair of side links, which overlap the end of the center link on the opposite, sides thereof, and are joined to the center link by a pin passing through the overlapping ends of the side links and center links. 
         [0003]    In accordance with long standing industry practice, the links of said chains come in lengths giving them a nominal 2 inch, 3 inch, 4 inch or 6 inch pitch dimension. The pitch is the distance between the centers of adjacent pins, and is referred to as nominal, as the pitch is typically 1/16 of an inch more than the nominal number. The actual length of each chain link is long enough to provide for the overlap, and leave the nominal pitch dimension as indicated. Chains are identified in part by their pitch. Thus a chain with a two inch pitch is referred to as a 2 inch chain, and so or By industry standard, a 2 inch chain uses pins which are 2/8 (¼) inch pins which are 4/8 (½) inch in diameter, and is more specifically identified as an X 348 chain. These and other dimensions for 2, 3, 4 and 6 inch chains are set forth in Table 1, with dimension “F” being the pin diameter. The other dimensions, A, B, C, etc listed in Table 1 are indicated in  FIGS. 1 and 2 . These are industry standards established through years of practice, and are set forth in the publications of the Conveyor Equipment Manufacturers Association (CEMA). 
         [0000]    
       
         
               
               
               
               
               
               
               
               
               
               
             
           
               
                   
               
               
                   
                   
                   
                 C 
                   
                 E 
                   
                 G 
                 H 
                 I 
               
               
                 Chain 
                 A 
                 B 
                 max 
                 D 
                 max 
                 F 
                 min 
                 min 
                 min 
               
               
                   
               
             
             
               
                 X-228 
                 2 
                  15/32 
                  11/16 
                 ⅜ 
                 1⅛ 
                 ¼ 
                  53/64 
                 1 1/16 
                  5/16 
               
               
                 X-50-6 
                  (50) 
                 (11.90) 
                 (17.46) 
                  (9.53) 
                 (28.57) 
                  (6.35) 
                 (21.03) 
                 (26.98) 
                  (7.94) 
               
               
                 X-348 
                 3 
                 ¾ 
                 1 3/32 
                 ½ 
                 1 27/32 
                 ½ 
                 1 9/32 
                 1⅝ 
                  9/16 
               
               
                 X-75-13 
                  (75) 
                 (19.05) 
                 (27.78) 
                 (12.70) 
                 (46.83) 
                 (12.70) 
                 (32.54) 
                 (41.27) 
                 (14.28) 
               
               
                 X-458 
                 4 
                 1 
                 1 13/32 
                 ⅝ 
                 2¼ 
                 ⅝ 
                 1⅝ 
                 2¼ 
                  11/16 
               
               
                 X-100-16 
                 (100) 
                 (25.4) 
                 (35.71) 
                 (15.87) 
                 (57.15) 
                 (15.87) 
                 (41.27) 
                 (57.15) 
                 (17.46) 
               
               
                 X-678 
                 6 
                 1 9/32 
                 2 
                  13/16 
                 3-118 
                 ⅞ 
                 2¼ 
                 3-318 
                  31/32 
               
               
                 X-150-22 
                 (150) 
                 (32.50) 
                 (50.80) 
                 (20.63) 
                 (79.37) 
                 (22.22) 
                 (57.15) 
                 (85.72) 
                 (24.61) 
               
               
                   
               
             
          
         
       
     
         [0004]    Trolleys are connected to the driven chains by a depending leg which passes through the opening in a center link. Thus, trolleys can be spaced as close as nominally 4 inches for a two inch chain, or in multiples thereof. For a three inch chain, the spacing would be six inches or multiples thereof, for a four inch, eight inches or multiples and for a six inch, 12 inches or multiples thereof. 
         [0005]    Also by industry standards and practice, the pitch of the chain used matches the nominal height of the I beam track used. The height of the beam may be higher than its nominal value, ex. the actual height of a 2 inch beam is 2 ⅝ inches. Also by industry standard and practice, trolleys are referred to by their nominal wheel diameter, which corresponds to the nominal height of the beam track they are carried on. The actual diameter is slightly less than the actual height of the I beam, so there is no binding of the trolley wheel between the lower beam flange and the upper beam flange. Thus a trolley with a nominal wheel diameter of 2 inches is used on a nominal 2 inch beam, a nominal 3 inch diameter wheel trolley is used on a nominal 3 inch beam, a 4 on a 4, and a 6 on to 6. 
         [0006]    Further, chains made to the various pitches are by practice and industry standard fashioned and manufactured to dimensions and pin sizes which cause the chain to have industry specified maximum allowable “chain pull loads.” Chain pull load refers to the load placed on the chain as it pulls its associated trolleys and any loads they are carrying. Thus, a 3 inch chain has a maximum allowable chain pull load of 1500 pounds. For a 4 inch chain it is 3000 pounds, and for a six inch chain, 5500 pounds. 
         [0007]    Trolleys are referred to by their nominal wheel diameter, which by industry standard and practice corresponds to the nominal beam height. The drive chain is driven by one or more drives. Multiple drives must be synchronized, and are used to make sure the maximum chain pull load for the chain is not exceeded in any portion thereof. 
       SUMMARY OF THE INVENTION 
       [0008]    The present invention comprises an overhead conveyor, components therefor and method for making same, in which the conveyor chain has a nominal pitch “X,” but a maximum allowable chain pull value which is equal to or greater than the maximum allowable chain pull value for a chain having a nominal pitch of X+1. 
         [0009]    In a more preferred embodiment, the conveyor chain has a pitch which is less than the nominal height of the beam on which it is carried, but has a maximum allowable chain pull value which is equal to or greater than that of a chain having a pitch equal to or greater than the height of the beam. 
         [0010]    This invention facilitates hitherto unappreciated advantages. For one, trolleys can be attached to said chain at intervals which differ from the intervals of a chain with pitch corresponding to the nominal height of the beam. Another is that fewer synchronized drives are required for driving longer chains. Yet another is that a lower pitch chain can be used to drive larger trolleys, without sacrificing the maximum allowable chain pull value always used in conjunction with the larger trolley. Thus for example a 2 inch chain can drive 3 inch trolleys, with the same maximum allowable chain pull value provided by a 3 inch chain. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]      FIG. 1  is a side elevational view of a chain segment identify dimensions provided in Table 1; 
           [0012]      FIG. 2  is a top plan view of a chain segment identifying dimensions provided in Table 1; 
           [0013]      FIG. 3  is a side elevational view of a three inch beam carrying a three inch chain with trolleys spaced at six inches; 
           [0014]      FIG. 4  is a side devotional view of a three inch beam carrying, a two inch chain of strength comparable that of a three inch chain, with trolleys spaced at eight inches; 
           [0015]      FIG. 5A  is a side devotional view of the adjoining links and pin for a two inch chain having the strength of a three inch chain; 
           [0016]      FIG. 5B  is a side elevational view of the adjoining links and a pin for a conventional two inch chain. 
           [0017]      FIG. 6A  is a top plan view of the adjoining links of  FIG. 5A ; and 
           [0018]      FIG. 6B  is a top plan view of the adjoining links of  FIG. 5B . 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0019]    The present invention is illustrated in the preferred embodiment by comparing a prior an 3 inch chain  10   a  driving 3 inch trolleys  20   a  on a 3 inch beam  30   a  ( FIG. 3 ), to a 2 inch chain  10   b  driving 3 inch trolleys  20   b  on a 3 inch beam  30   a  ( FIG. 4 ). Each chain has center links  11   a  or  11   b  respectively, joined by pairs of side links  12   a  or  12   b . The adjacent links are joined by pins  13   a  and  13   b  respectively. One of the advantages of the present invention is that by using a 2 inch chain  10   b  with the strength of the 3 inch chain  10   a  or greater, one can achieve the same or greater maximum allowable chain pull load while giving the operator greater flexibility in trolley spacing. For the 3 inch chain shown in  FIG. 3 , an operator must space his trolleys at 6. 12, 18, 24 inches, etc. In contrast, an operator using a 2 inch chain of the present invention enjoys the same maximum allowable chain pull load as the operator using a 3 inch chain, but can space the trolley,  20   b  as close as 4 inches, or at multiples thereof. While a 6 inch spacing might be too close for the operator&#39;s proposed use, is 12 inch spacing may simply waste space, and require a higher chain speed to achieve the desired level of productivity. By using a 2 inch chain in accordance with the present invention, the operator can use a spacing of 8 inches, rather than 6 inches, without sacrificing maximum allowable chain pull load, merely by securing a trolley to every other center link as shown in  FIG. 4 . The same level of productivity can be achieved using a proportionally lower chain speed. 
         [0020]    In the preferred embodiment shown, the 2 inch chain  10   b  is given the strength of the 3 inch chain  10   a  by:
       1. Utilizing a ½ inch pin instead of a ¼ inch pin, and   2. By utilizing 2 inch pitch links which are thicker in material cross section than those of a prior art 2 inch pitch chain.       
 
         [0023]    See  FIGS. 5A ,  5 B,  6 A and  6 B. To reflect the difference in pin diameter, the preferred embodiment 2 inch chain  10   b  is identified more specifically as an X-248 chain, rather than as a prior art X-228 chain. The pins used in the 3 and 4 inch preferred embodiment chains would have diameters of ⅝ and ⅞, and would be more specifically identified as X-358 and X 478 chains, rather than conventional X-348 and X-458. 
         [0024]    The center links  11   b  of the preferred embodiment 2 inch chain  10   b  have spaced. side legs  14   b  with a height of 0.5 inch as compared to 0.3 inch for the leg portion  14   c  of a center link  11   c  of prior art 2 inch chain  10   c . Preferably the center link legs in all of the preferred embodiment chains are 50-75% taller than their corresponding prior art counterparts, i.e. industry standard center links for chains of the same pitch. Similarly, the thickness of the leg portions  14   b  of center link  11   b  are 0.26 inch as compared to 0.19 inch thickness for the legs  14   c  of a prior art 2 inch chain  10   c . Preferably, the center link legs in all of the preferred embodiment chains are 25-50% thicker than their prior art industry standard counterparts. The corresponding dimensions for spaced legs  15   b  and  15   c  of the side links  12   b  and  12   c  are: 
         [0025]    Heights 0.26 inch versus 0.19 inch; and 
         [0026]    Thicknesses 0.35 inch versus 0.25 inch. 
         [0027]    Preferably the side link legs in all of the preferred embodiment chains are 25-50% taller, and 25-50% thicker than their corresponding prior art counterparts. Other measures can be taken to farther strengthen the 2 inch chain  10   b  of the preferred embodiment. In a similar manner. the dimensions of the links used in the 3 and 4 inch chants of the preferred embodiment chains are larger in similar proportions than those of corresponding, prior art 3 and 4 inch chains, 
         [0028]    The trolleys  20   a  and  20   b  shown in  FIGS. 3 and 4  have a pair of wheels  21   a  and  21   b  respectively, each wheel being oriented on an opposite of its respective beam  30   a . A pair of arms  22   a  and  22   b  respectively extend downwardly, one from each of the opposed wheels  21   a  or  21   b . Arms  22   a  and  22   b  respectively extend downwardly and then inwardly towards one another, and then downwardly again to define downwardly depending legs  25   a  and  25   b . The legs  25   a  and  25   b  pass through the openings in the respective center links  11   a  and  11   b . A downwardly depending working attachment (not shown) may be secured between said legs  25 . The working attachment might be a hook for hanging material to convey, or a pusher for pushing free trolleys on a lower track, or some other device. 
         [0029]    Leg  25   b  of trolley  20   b  is slightly narrower than leg  25   a  of trolley  20   a . This allows leg  25   b  to fit within the smaller opening of a 2 inch center link, as compared to the opening of the 3 inch center link  11   a . Further while the arms and legs  22  and  25  of both trolleys  20   a  and  20   b  both have ribs  23   a  or  23   b  running along the respective edges thereof, trolley  20   b  includes an additional rib  24   b  extending between the two ribs  23   b , located so as to be adjacent the top and bottom of the leg of center link  11   b  (compare  FIG. 4  to  FIG. 3 ). This gives greater strength to the narrower leg  25   b  of trolley  20   b . No such joining rib  24  is used in the trolleys  20   a.    
         [0030]    The benefits of the present invention have not at all been recognized or thought of by prior artisans. The use of a 2 inch chain with the strength of a 3 inch chain or more gives an operator greater flexibility in spacing the trolleys used, without sacrificing maximum allowable chain pull load. The same is true for using a 3 inch chain instead of a 4, or a 4 instead of a 5. This not only maximizes chain capacity, but also allows one to use slower chain speeds. If the trolleys and their loads have to be farther apart, the chain must move faster in order to meet production requirements. Closer spacing allows for slower chain speeds to meet the same production requirements. Using the chains at lower speeds causes less wear and tear on the chains, and avoids other problems as well. 100 to 130 feet a minute is about as fast as the chains can be comfortably operated. 
         [0031]    Another advantage is that the higher maximum chain pull value makes possible the use of fewer synchronized drives to drive the chain. Yet another is that a lower pitch chain can be used. to drive larger trolleys, without sacrificing the maximum allowable chain pull value always used in conjunction with the larger trolley. Thus for example, a 2 inch chain can drive 3 inch trolleys, with the same maximum allowable chain pull value provided by a 3 inch chain. 
         [0032]    These and other objects, advantages and features of the present invention will be understood and appreciated by those of ordinary skill in the art.