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You are an expert at summarizing long articles. Proceed to summarize the following text: 
BACKGROUND OF THE INVENTION 
       [0001]    The present invention relates generally to coiled tubing injector apparatus for inserting and removing coiled tubing from a well. More particularly, the present invention relates to a traction system for use in the coiled tubing injector apparatus wherein the traction system includes a roller chain and carrier gripper block assembly. 
         [0002]    Coiled tubing operations are growing in use as compared to traditional well drilling operations. The ability to inject coiled tubing with increased diameter has added to the use of such operations. Coiled tubing injector assemblies typically comprise an injector head, a spool reel for transporting the coiled tubing, and some type of hydraulic power apparatus or other power apparatus. The injector head grips the coil tubing through a series of grippers powered by a roller chain. The roller chain includes a carrier gripper block assembly which provides force to grip and move the tubing as necessary to complete the insertion and removal. 
         [0003]    It is an object of the present invention to provide an improved roller chain traction system for use with a carrier gripper block assembly for use in a coiled tubing injector head. 
       SUMMARY OF THE INVENTION 
       [0004]    The present invention provides an improved roller chain assembly for use as part of a coiled tubing injector apparatus. The improved roller chain assembly includes a carrier gripper block to grip the tubing in the injector head. 
         [0005]    The carrier gripper block transmits the squeezing force for the injector traction system, which is usually hydraulic but can utilize other types of force. Force is transmitted from the skate plate to the roller chain to the carrier gripper block to grip the tubing. Due to the force on the carrier gripper block in gripping the chain for injection, the roller chain pins are subjected to high forces. The roller chain pins can experience bending moments as the chain articulates around the sprockets that are part of the traction system. 
         [0006]    The present invention utilizes roller chain with center plates and cover plates that are press fit onto the chain pins. Such press fitting better supports length of the chain pins across the width of the chain, which must be wide enough to accommodate the carrier gripper block, and thus reduces the pin bending moment by the loading from the carrier gripper blocks. This results in an increase in fatigue strength of the chain pins. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]    In the drawings, 
           [0008]      FIG. 1  is a side view of a portion of a roller chain gripper block assembly; 
           [0009]      FIG. 2  is a side view of a injector head including the roller chain carrier/gripper block assembly; 
           [0010]      FIG. 3  is a side view of the roller chain in accordance with a first embodiment of the present invention; 
           [0011]      FIG. 4  is a perspective view of a roller chain with chain pins and center plates being press fit thereon; 
           [0012]      FIG. 5  is a perspective view of a roller chain in accordance with the first embodiment of the present invention having chain pins with a carrier block and rollers; 
           [0013]      FIG. 6  is a perspective view of a roller chain in accordance with the first embodiment of the present invention with the carrier block assembly and second center plates being press fit onto the chain pins; 
           [0014]      FIG. 7  is a side view of a roller chain carrier block assembly in accordance with the first embodiment of the present invention further including roller links applied to the chain pins; 
           [0015]      FIG. 8  is a side view of a roller chain gripper block assembly in accordance with the first embodiment of the present invention further including cover plates press fit onto chain pins; 
           [0016]      FIG. 9  is a perspective view of a roller chain gripper block assembly in accordance with the first embodiment of the present invention further including a second roller link assembly being applied to chain pins; 
           [0017]      FIG. 10  is a perspective view of a roller chain carrier block assembly in accordance with the first embodiment of the present invention further comprising cover plates press fit onto chain pins, and 
           [0018]      FIG. 11  is a perspective view of a roller chain gripper block assembly in accordance with the first embodiment of the present invention further comprising cotter pins being placed through lateral openings in the ends of chain pins. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0019]    Referring now to  FIGS. 1 and 3  of the drawings, a roller chain gripper block assembly is shown generally at  10 . Such roller chain gripper block assembly is seen to comprise a plurality of chain pins  19 , with adjacent chain pins  19  joined by press fit center plates  11  and  11   a . The press fitting of such center plates requires the use of a mechanical device, usually a hydraulic press as the openings in the center plates  11  and  11   a  are only a very small interference in diameter smaller than the diameter of chain pin  19  itself. Such interference is usually 0.0025 inch (0.064 mm). 
         [0020]    Two identical chain assemblies are shown, with chain assembly roller link  30  comprised of laterally adjacent link plates  32  and  34 , with roller  21  there between. It should be understood that rollers  21  have openings such that chain pins  19  fit there through. Further, link plates  32  and  34  have openings such that chain pins  19  fit there through with sufficient tolerance with openings in link plates  32  and  34  to allow roller link  30  to flex about chain pins  19 . Finally, cover plate  12  is press fit onto ends of chain pins  19 . Openings in cover plate  12  are of a diameter slightly greater than the diameter of chain pin  19  such that cover plate  12  must be press fit onto the ends of chain pin  19  by a mechanical means such as a hydraulic press. Similarly, at the other side of roller chain gripper block assembly  10 , with a second roller link assembly mounted onto adjacent chain pins  19 , it can be seen that cover plate  13  is press fit onto adjacent ends of chain pins  19 . The openings in cover plate  13  are again of a smaller diameter than the chain pin  19  diameter such that the placement of cover plate  13  onto chain pins  19  requires a mechanical device such as a hydraulic press. Such interference across the diameter is usually 0.006 inch (0.152 mm). Finally, cotter pin  16  can be utilized and placed through lateral openings  17  in chain pins  19  to secure those ends of chain pin  19  outside cover plate  13 . It should be mentioned here that other ends of chain pins  19  are stamped to a larger diameter such that cover plates  12  are held in place by such increased stamp diameter of the end chain pins  19 , which acts to secure cover plates  12  in addition to press fit of cover plate  12  onto chain pin  19  ends. 
         [0021]    It should be here explained that the preferred material for chain pins  19  is a steel rod, usually a AISI 8640 or other medium carbon alloy steel. Further, the usual materials for center plates  11  and  11   a , and cover plates  12  and  13  are a stamped steel, usually a AISI 5140 or another medium carbon alloy steel. Finally, rollers  21  are a section of a cylindrical tube, usually comprised of a AISI 10B21 or other low carbon high alloy steel. 
         [0022]    Referring now to  FIG. 2 , a typical roller chain gripper block assembly is shown at  10  located within a injector head frame  22 . Tubing itself is shown at  20  and is seen to be grasped by the carrier block grippers which themselves are pressed into engagement with tubing  20  by gripper block loading cylinders  24 . A hydraulic or other motor is shown at  26  to power sprockets to drive gripper block chain thereby enabling tubing  20  to be inserted or withdrawn as needed. 
         [0023]    Referring now to  FIGS. 4-11  the steps in assembling roller chain for use in roller chain gripper block assembly  10  are set forth. The initial step includes providing a plurality of chain pins  19 , and press fitting center plates over adjacent chain pins  19  in a mechanical operation usually requiring a use of a hydraulic press. The openings in center plates  11  are only very slightly smaller, to an interference of usually 0.0025 inch (0.064 mm) smaller than the diameter of chain pins  19  which requires that the center plates be press fit onto chain pins  19 . The next step is shown in  FIG. 5  wherein carrier blocks  36  are places over adjacent chain pins  19 . Carrier blocks  36  include carrier block rollers  37 . Openings  38  in carrier block  36  are sufficiently larger in diameter than the diameter of chain pins  19  such that carrier blocks may be placed onto adjacent pins  19  without the use of a mechanical device. 
         [0024]    Referring now to  FIG. 6 , a second center plate  11   a  is press fit onto the other ends of adjacent chain pins  19 . Again, as with center plates  11 , the openings in center plates  11   a  are only slightly larger in diameter than the diameter of chain pins  19  whereby center plates  11   a  must be press fit using a mechanical device, usually a hydraulic press to enable the center plates to be placed onto adjacent chain pins  19 . Also shown in  FIG. 6  are carrier block grippers  40 . Carrier block grippers  40  are utilized to grasp coil tubing  20  in thus inserted or withdrawn in the drilling operation. 
         [0025]    Referring now to  FIG. 7 , a first roller link  30  is placed onto ends of roller pins  19 . Roller link  30  is seen to comprise link plates  32  and  34 , with rollers  21  in between. Further openings  35  in roller link plate  34  with a similar opening in roller link plates  32  are of a diameter larger than the diameter of chain pin  19  such that roller assembly  21  can rotate about chain pins  19 . 
         [0026]    Referring now to  FIG. 8 , a cover plate  12  is seen to be press fit by a mechanical means, usually a hydraulic press, over the ends of chain pins  19 . Openings in cover plate  12  are smaller in diameter than the diameter of chain pins  19  in the order of 0.006 inch (0.152 mm), such that cover plate  12  must be press fit onto the end of chain pins  19  using a mechanical device such as a hydraulic press. 
         [0027]    Referring now to  FIG. 9 , roller chain gripper block assembly  10  is seen to have a second roller link assembly  42  placed onto the other ends of chain pins  19 . Roller link  42  is seen to be comprised of link plate  44  and  46 , with roller  47  held there between. Link plate  44  includes an opening  45  of a diameter larger than the diameter of chain pin  19  such that when roller link assembly  42  is placed on adjacent chain pins  19 , chain pins  19  can rotate therein. 
         [0028]    Referring now to  FIGS. 10 and 11 , cover plate  13  is seem to be press fit onto ends of chain pins  19 . Should be understood that cover plate  13  includes openings that are slightly larger than diameter than the diameter of chain pins  19  such that the application of cover plates  13  onto the ends of chain pins  19  requires a mechanical press fit operation, usually involving use of a hydraulic press. Finally, cotter pin  48  are placed through lateral openings in the ends of chain pins  19  to further secure cover plates  13  thereon. 
         [0029]    It should be understood that the press fitting of center plates  11  and  11   a , and cover plates  12  and  13  act to secure the holding of chain pins  2  for plates per chain pin thus increasing the rotational force required to turn a chain pin while in service in a roller chain gripper block assembly  10 . 
         [0030]    A summary of the assembly of a roller chain gripper block assembly  10  will now be provided. Two chain pins  19  are placed into press fitting hydraulic press. Lubricating oil is placed on top of chain pins  19  and center plate  11  is placed over the ends of adjacent chain pins  19 . This operation is repeated for all the necessary chain pins in the length of the roller chain required for the roller chain gripper block assembly  10 . A carrier block  36  with rollers is then placed over ends of adjacent chain pins  19 . The openings in carrier block  36  are sufficient to allow rotation of chain pins  19  therein. The carrier block is slid down all the way over chain pins  19  to fit adjacent center plate  11 . 
         [0031]    Now using gear oil lubricate the opposite top of chain pins  19 , second center plates  11   a  are press fit thereon. This is repeated for the entire length of the roller chain as necessary for the roller chain gripper block assembly  10 . A second set of roller links are then slid over the chain pin ends  19  a second set of roller links  42  is then placed over the ends of chain pins  19 . 
         [0032]    A cover plate  12  is then press fit over the ends of chain pins  19  to secure the first carrier block  36  thereon. The second roller link is then assembled over then placed over the ends of second roller link  42  is then placed of the other ends of chain pins  19 , with cover plates  13  then press fit over the ends of chain pins to secure the roller link  42  assembly in place.

Summary:
A coiled tube chain assembly is provided designed for use with a carrier gripper block to grip the coiled tubing. The roller chain assembly provides the traction system for use in the coil tubing injector head. The roller chain is comprised of center plates and cover plates that are press fit onto the chain pins. The use of such press fit center plates and cover plates increases the number of link plates holding the chain pin.