Abstract:
A coiled tubing injector skate having rollers that independently adjust position to more uniformly distribute roller loading forces is provided. The skate includes a frame and at least one roller having a roller shaft with a first end retained by the frame and a second end retained by the frame. A first resiliently compressible material is disposed between the first end of the roller shaft and the frame. A second resiliently compressible material disposed between the second end of the roller shaft and the frame.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates generally to coiled tubing injectors, and more particularly, relating to coiled tubing injector skates. 
       BACKGROUND OF THE INVENTION 
       [0002]    Coiled tubing also referred to as coiled pipe or continuous pipe is conventionally used in the oil and gas industry. The coiled tubing is stored on a reel, and during use the tubing is unwound from the reel and inserted into a well. The coiled tubing is inserted and removed from a well using a device commonly referred to as a coiled tubing injector. 
         [0003]    Coiled tubing injectors are well known in the technological field of the invention, and conventionally include a pair of continuous chain loops to which are attached a plurality of tubing gripper blocks. As the chain loops are driven, confronting tubing gripper blocks are pressed together on opposite sides of the coiled tubing and grip the exterior of the coiled tubing. The coiled tubing, grasped by the tubing gripper blocks, is conveyed in the same direction as the tubing gripping blocks. Examples of coiled tubing injectors are shown in U.S. Pat. Nos. 6,892,810; 6,216,780; 5,918,671; 5,553,668 and 5,188,174, which are incorporated herein in their entirety by reference. 
         [0004]    The tubing gripper blocks are pressed together by skates that are positioned on opposite sides of the coiled tubing with the tubing gripper blocks running between the tubing and the skates. The skates include rollers which engage the tubing gripper blocks and provide a rolling contact surface between the moving gripper blocks and the skates. Hydraulic cylinders or other mechanisms are used to force the oppositely positioned skates together which cause the tubing gripper blocks to press against the tubing. A significantly high force is applied to the skates to cause the tubing gripper blocks to grip the coiled tubing with a sufficiently great force that prevents the tubing from slipping between the tubing gripper blocks. 
         [0005]    The skate rollers bear the force exerted upon the tubing gripping blocks, and thus during use are under a considerably high loading force. Consequently, the rollers have a limited cycle life. Further, the cycle life of the rollers is reduced as a result of non-uniform loading across the rollers as a result of inconsistent manufacturing tolerances within the rollers themselves and inconsistent manufacturing tolerances within the various other elements forming the coiled tubing injector. Additionally, during use the gripper blocks and/or chain loops may become misaligned also creating a non-uniform loading on the rollers. Replacement of the rollers is an expensive and time consuming task, and thus it is desirable to minimize the frequency of replacement. Accordingly, there is a need and a desire for a device and/or system that reduces wear and fatigue on the rollers due to non-uniform loading. 
       SUMMARY OF THE INVENTION 
       [0006]    Embodiments of the present invention addresses this need by providing a coiled tubing injector skate having a roller mounting arrangement that permits each roller to independently adjust its position to more uniformly distribute loading across the roller. 
         [0007]    Embodiments of the present invention also provide a coiled tubing injector skate having rollers that are each independently mounted to the skate by separate resilient floating mounts. 
         [0008]    To achieve these and other advantages, in general, in one aspect, a coiled tubing injector skate is provided. The skate includes a frame and at least one roller having a roller shaft with a first end retained by the frame and a second end retained by the frame. A first resiliently compressible material is disposed between the first end of the roller shaft and the frame. A second resiliently compressible material disposed between the second end of the roller shaft and the frame. 
         [0009]    In general, in another aspect, the skate further includes a force distributing disc disposed between the first end of the roller shaft and the first resiliently compressible material, and a force distributing disc disposed between the second end of the roller shaft and the second resiliently compressible material. 
         [0010]    There has thus been outlined, rather broadly, the more important features of the invention in order that the detailed description thereof that follows may be better understood and in order that the present contribution to the art may be better appreciated. 
         [0011]    Numerous objects, features and advantages of the present invention will be readily apparent to those of ordinary skill in the art upon a reading of the following detailed description of presently preferred, but nonetheless illustrative, embodiments of the present invention when taken in conjunction with the accompanying drawings. The invention is capable of other embodiments and of being practiced and carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein are for the purpose of descriptions and should not be regarded as limiting. 
         [0012]    As such, those skilled in the art will appreciate that the conception, upon which this disclosure is based, may readily be utilized as a basis for the designing of other structures, methods and systems for carrying out the several purposes of the present invention. It is important, therefore, that the claims be regarded as including such equivalent constructions insofar as they do not depart from the spirit and scope of the present invention. 
         [0013]    For a better understanding of the invention, its operating advantages and the specific objects attained by its uses, reference should be had to the accompanying drawings and descriptive matter in which there are illustrated embodiments of the invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]    The following drawings illustrate by way of example and are included to provide further understanding of the invention for the purpose of illustrative discussion of the embodiments of the invention. No attempt is made to show structural details of the embodiments in more detail than is necessary for a fundamental understanding of the invention, the description taken with the drawings making apparent to those skilled in the art how the several forms of the invention may be embodied in practice. Identical reference numerals do not necessarily indicate an identical structure. Rather, the same reference numeral may be used to indicate a similar feature of a feature with similar functionality. In the drawings: 
           [0015]      FIG. 1  is a diagrammatic perspective view of a pair of opposing coiled tubing injector skates constructed in accordance with the principles of an embodiment of the invention acting upon confronting tubing gripper blocks and a section of tubing; 
           [0016]      FIG. 2  is a back perspective view of a coiled tubing injector skate constructed in accordance with the principles of an embodiment of the present invention; 
           [0017]      FIG. 3  is a front perspective view of a coiled tubing injector skate constructed in accordance with the principles of an embodiment of the present invention; 
           [0018]      FIG. 4  is an enlarged, partial and exploded perspective view a coiled tubing injector skate constructed in accordance with the principles of an embodiment of the present invention; 
           [0019]      FIG. 5  is an exploded perspective view of a roller constructed in accordance with the principles of an embodiment of the present invention; 
           [0020]      FIG. 6  is a side elevation view of a coiled tubing injector skate constructed in accordance with the principles of an embodiment of the present invention; 
           [0021]      FIG. 7  is a cross-sectional view through a mounted roller and the skate taken along line  7 - 7  in  FIG. 6 ; 
           [0022]      FIG. 8  is an enlarged detail view as indicated in  FIG. 7 ; 
           [0023]      FIG. 9  is a loading diagram of a mounted roller; 
           [0024]      FIG. 10  is a loading diagram of a resilient compression material utilized in the floating mount of a roller; and 
           [0025]      FIG. 11  is a loading graph of a resultant roller load as a function the compression of the resilient compression material and the applied load. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0026]    In  FIG. 1  there is representatively illustrated a pair of oppositely mounted skates  10   a,    10   b,  each of which are constructed in accordance with the principles of an embodiment of the present invention, and are for use in connection with a coiled tubing injector. Skates  10   a,    10   b  are pushed together by hydraulic cylinders (not shown) to press together a series of confronting pairs of tubing gripper blocks  12   a,    12   b  against tubing  14  that is disposed between the skates  10   a,    10   b.  The force exerted by the hydraulic cylinders upon each skate  10   a,    10   b  is generally represented by force vectors F. Conventionally, each pair of gripper blocks  12   a,    12   b  are connected to driven chains, not shown for the purpose of illustrative clarity, to convey the gripper blocks across the skates  10   a,    10   b  while being pressed together, and thus convey the tubing  14  between the skates. 
         [0027]    Skates  10   a,    10   b  are identical, and thus a discussion of only skate  10   a  is required. 
         [0028]    With reference to  FIGS. 2 ,  3 , and  4 , skate  10   a  includes an elongated beam or frame  18  and a plurality of rollers  20  mounted to the frame along the inward facing side  30 . Rollers  20  provide a rolling bearing surface against which gripper blocks  12   a  are pressed and conveyed when gripping tubing  14  (not shown), for purpose of illustrative clarity only a single gripper block is illustrated. As will be described in further detail below, rollers  20  are mounted to frame  18  in a fashion that permits each roller to independently float or move with respect to the frame. The ability for each roller  20  to independently float permits the positioning of each roller to separately adjust to irregular geometries of the roller itself, frame  18 , gripper blocks  12   a,  tubing  14  and/or other elements that otherwise create uneven pressure distribution across the rollers  20  resulting in increased wear and fatigue. The floating mount of each roller  20  reduces wear and fatigue caused by irregular geometries, and thus increases the service life of the roller. 
         [0029]    With continued reference to  FIGS. 2 ,  3 , and  4 , frame  18  includes a back side  28 , a front side  30  and a longitudinally extending channel  22  defined by forwardly projecting, longitudinal flanges  24 ,  26  that extend from the front side of the frame. Each roller  20  includes a roller axel or shaft  32  to which it is rotatably mounted. Each roller  20  is disposed within channel  22  with the roller extending transversely with respect to the frame  18  between flanges  24 ,  26 . Opposite ends  34 ,  36  of the shaft  32  are received by cooperatively aligned slots  38 ,  40  extending through flanges  24 ,  26 , respectively. The end  34  of each shaft  32  is retained in its respective slot  38  by a cap plate  42  that is mounted to a forward facing edge  44  of flange  24  by a plurality of threaded fasteners  46  extending cooperating holes  48 ,  50 . Similarly, the end  36  of each shaft  32  is retained in its respective slot  40  by cap plate  52  that is mounted to the forward facing edge  54  of flange  36  by a plurality of threaded fasteners  46  extending cooperating holes  56 ,  58 . Cap plates  42 ,  52  extend the length of flanges  24 ,  26 , respectively, and cover or close slots  38 ,  40 , thereby preventing withdrawal of the shaft ends  34 ,  36  from the slots. 
         [0030]    With further reference to  FIG. 5 , there is illustrated an exploded assembly of roller  20 , shaft  32  and wear washers  60 ,  62 . A longitudinal length of each shaft end  34 ,  36  is squared off for reception by the slots  38 ,  40  and to provide a flat bearing surface for a dampening system that will be further described below. Additionally, the squared off ends  34 ,  36  prevent shaft  32  from rotating about its own axis once received by slots  38 ,  40 . In an embodiment, roller  20  may be a needle roller bearing. Additionally, shaft  32  may include a grease passage  64  for lubricating the roller  20  upon shaft  32 . 
         [0031]    With reference to  FIG. 4  and  FIGS. 6 through 8 , a bottom face  66 ,  68  of slots  38 ,  40  include a blind-hole  70 ,  72 . A cylindrical-shaped elastomeric element  74 ,  76  is inserted into the blind-hole  70 ,  72  followed by a force distributing disc  78 ,  80 . Disc  78 ,  80  include an alignment boss  86 ,  88  that extends from one side thereof and which is received by elastomeric element  74 ,  76  for the purpose of aligning the disc with the elastomeric element. It is important to note that elastomeric elements  74 ,  76  each represent different possible embodiments thereof, and while elastomeric element  74  is illustrated being received by hole  70  and elastomeric element  76  is illustrated being received by hole  72 , in application either or may be utilized in either or both holes. That is, the invention is not limited in any manner by the illustration of hole  70  receiving elastomeric element  74  and hole  72  receiving elastomeric element  76 . 
         [0032]    Further, while elastomeric elements  74 ,  76  each represent different structural features, they share the common principle function of providing a biasing force. Accordingly, the following discussion will address the principal function, and then the specific features of each elastomeric element. 
         [0033]    Now beginning with the principle function, elastomeric element  74 ,  76  and disc  78 ,  80  are appropriately sized such that the disc protrudes from the blind-hole  70 ,  72  a distance dLo. In this manner, a flat side  82 ,  84  of shaft ends  34 ,  36  bears against the disc  78 ,  80  and is spaced from bottom face  66 ,  68  a distance equal to dLo. Accordingly, shaft ends  34 ,  36  are capable of limited vertical movement within slots  38 ,  40  and with respect to frame  18  against the spring force of the elastomeric element  74 ,  76 . Additionally, this mounting configuration permits the roller shaft  32  to rock about an axis perpendicular to the roller shaft. The spring force exerted by the elastomeric element  74 ,  76  upon compression may be adjusted as desired through the selection of a material having a desired or suitable elastic modulus.  FIGS. 9 ,  10 , and  11  are force diagrams illustrating the force distribution across the roller and elastomeric elements, and the relational dimensional characteristics thereof. 
         [0034]    In a first embodiment, elastomeric element  74  includes a spherically-shaped recess  90  formed through one end  92  thereof that is configured to receive boss  86  therein to axially align disc  78  therewith. Additionally, to permit desired compression of the elastomeric element  74 , is of a diameter that provides a radial gap r between the side of the elastomeric element and the sidewall of blind-hole  70 . 
         [0035]    In a second embodiment, elastomeric element  76  includes an axial through-passage  94  into which is received boss  88  of disc  80  to axially align the disc and elastomeric element. In this embodiment, the elastomeric element  76  is configured to have a diameter such that there is no radial gap between the side thereof and the sidewall of blind-hole  72 , and the through-passage  94  permits a desired compression of the elastomeric element. Again, it is important to understand, that discs,  78 ,  80 , elastomeric elements  74 ,  76  and blind-holes  70 ,  72  may be utilized interchangeable, and the invention is not limited to the illustrated configuration. 
         [0036]    A number of embodiments of the present invention have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the invention. Accordingly, other embodiments are within the scope of the following claims.