Abstract:
A casing slip lifter includes a frame, upper and lower lift arm assemblies, at least one air cylinder connected to a pipe that rotates to pivot the arm assemblies, and a wrap arm to which the slips are attached and which is coupled to the arm assemblies by a hinge. The arm assemblies include mutually pivotable plates, one of which may be latched to enable the arm assemblies to be raised into one of two raised positions, depending on which the lower arm assembly is locked. The higher position permits the casing lifter to be used when centralizers are installed on the casing.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    This invention relates to a mechanism for lowering a casing slip into a bushing bowl and for subsequently lifting the casing slip out of the bushing bowl, and in particular to a mechanism that uses hydraulic cylinders to lower and raise the casing slip.  
           [0003]    2. Description of Related Art  
           [0004]    Casing slips have conventionally been lowered into and lifted out of a drilling hole manually. Since casing slip insertion and removal must be repeatedly carried out in order to lock and release successive casing sections during deep well drilling operations, such as oil well drilling, difficulties in removing the casing slips can add significantly to drilling costs.  
           [0005]    Devices for automatically lifting and lowering casing slips have previously been proposed, but all require integral or modified bushing bowls and/or casings. Examples of such powered slip assemblies, which integrate the bushing bowl and casing slip, and which lift the casing slip so as to enable removal of at least elements of the casing slip from the integrated bushing bowl, are disclosed in U.S. Pat. Nos. 4,253,219 (Krasnov); 3,760,469 (Brown); 2,641,816 (Liljestrand) ; and 2,030,087 (Young). While such mechanisms lift the casing slip sufficiently to enable disengagement, they are not capable of lifting the casing slip completely out of the bushing bowl, are relatively complex and/or difficult to implement, and furthermore the mechanisms themselves must be lowered and lifted, resulting in an increase rather than a decrease in the effort required to manipulate the casing slip.  
           [0006]    In contrast, the present invention provides a hydraulically actuated lift mechanism that is intended to lift a casing and allow the casing slip to completely clear the bushing bowl, without modifying or integrating the bushing bowl that cams the casing slips into gripping engagement with the casing section. None of the above-cited patents, or any of background U.S. Pat. Nos. 6,227,587 (Terral); 4,511,168 (Haynes); and 4,275,488 (Gray), while U.S. Pat. Nos. 6,224,112 (Eriksen); 5,669,653 (Penisson) ; 5,301,750 (Watkins) ; and 4,340,116 (Weise), discloses such a mechanism.  
         SUMMARY OF THE INVENTION  
         [0007]    It is accordingly a first objective of the invention to provide apparatus for lowering a casing slip into and for lifting a casing slip completely out of a bushing bowl, in order to decrease the effort required to carry out the lowering and raising, increase drilling efficiency, and reduce risks of injury or equipment damage.  
           [0008]    It is a second objective of the invention to provide a powered casing slip lift mechanism that can be used with existing casing slips and wellhead configurations.  
           [0009]    It is a third objective of the invention to provide a powered casing slip lift mechanism that has a simple construction and is easily manufactured.  
           [0010]    It is a fourth objective of the invention to provide a powered casing slip lift mechanism that is simple and safe to use.  
           [0011]    These objectives are accomplished, in accordance with the principles of a preferred embodiment of the invention, by providing casing slip lift mechanisms arranged to be pinned in pairs to the rotary bushing prior to the start of a casing job. When each of the pinned mechanisms is in a raised position, casing can be run in conventional fashion without interference. Once the casing joint is lowered to the collar, the slips may be lowered into the bushing bowl by actuating a hydraulic control valve, which lowers the slips into the bushing bowl around the casing, thus locking the casing into place.  
           [0012]    The casing slip lifter of the preferred embodiment includes a frame, upper and lower lift arm assemblies, at least one air cylinder connected to a pipe shaft that rotates to pivot the arm assemblies in response to actuation of the air cylinder, and a wrap arm to which the slips are attached and which is coupled to the arm assemblies by a hinge.  
           [0013]    According to an especially preferred aspect of the invention, the casing slip lifting mechanism can be pivoted into two alternative raised positions, depending on whether the lower arm assembly is locked by a manually positioned ear lock. The higher position permits the casing slip mechanism to be used when centralizers are installed on the casing.  
           [0014]    Finally, the design of the lifter mechanism of the invention may easily be adapted to lift tubing and drill pipes, as well as casing, by simply replacing the wrap arms with arms of appropriately smaller dimensions. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0015]    [0015]FIG. 1 is a plan view of a casing slip lifter constructed in accordance with the principles of a preferred embodiment of the invention.  
         [0016]    [0016]FIG. 2 is a plan view of a frame for supporting the preferred casing slip lifter.  
         [0017]    [0017]FIG. 3 is a rear elevation of the frame illustrated in FIG. 2.  
         [0018]    [0018]FIG. 4 is a side elevation of the frame illustrated in FIGS. 2 and 3.  
         [0019]    [0019]FIG. 5 is a plan view of a pipe shaft and lower arm assembly of the preferred casing slip lifter.  
         [0020]    [0020]FIG. 6 is a plan view of the left and right lower arm assemblies included in the pipe shaft and lower arm assembly of FIG. 5.  
         [0021]    [0021]FIG. 7 is a side view of the right hand lower arm assembly illustrated in FIG. 6.  
         [0022]    [0022]FIG. 8 is a disassembled side view of the right hand lower arm assembly illustrated in FIG. 7.  
         [0023]    [0023]FIG. 9 is a side view showing the relationship between the lower arm assembly and the air cylinder arm used to rotate the lower arm assembly.  
         [0024]    [0024]FIGS. 10 and 11 are side views showing respective retracted and extended positions of the air cylinder illustrated in FIG. 1.  
         [0025]    [0025]FIG. 12 is a plan view of the air cylinder illustrated in FIGS. 10 and 11.  
         [0026]    [0026]FIG. 13 is a plan view of the casing slip lifter with locking mechanism and lower arm assemblies removed to better illustrate the position of the upper arm assemblies.  
         [0027]    [0027]FIG. 14 is a plan view of the left and right upper arm assemblies illustrated in FIG. 13.  
         [0028]    [0028]FIG. 15 is a side view of one of the upper arm assemblies illustrated in FIG. 14.  
         [0029]    [0029]FIG. 16 is a disassembled side view of the upper arm assembly of FIG. 15.  
         [0030]    [0030]FIG. 17 is side view showing the assembled lower and upper arm assemblies together with a hinge and locking mechanism.  
         [0031]    [0031]FIGS. 18 and 19 are, respectively, a side view and a plan view of a hinge for use in coupling a wrap arm to the lower and upper arm assemblies of the preferred embodiment.  
         [0032]    [0032]FIG. 20 is a side view of a grabber arm assembly for use in securing a casing slip to the preferred casing slip lifter.  
         [0033]    [0033]FIG. 21 is a plan view of a wrap arm and fixtures according to the preferred embodiment of the invention.  
         [0034]    [0034]FIG. 22 is a plan view of an alternative wrap arm that may be substituted for the wrap arm illustrated in FIG. 21.  
         [0035]    [0035]FIG. 23 is a side view of the frame illustrated in FIG. 2, together with a handle for activating the locking mechanism of the preferred embodiment.  
         [0036]    [0036]FIG. 24 is a side view of an ear lock used in the preferred locking mechanism.  
         [0037]    [0037]FIG. 25 is an end view of the preferred casing slip lifter, including the ear lock.  
         [0038]    FIGS.  26 - 29  are side views illustrating, respectively, situations in which the lifter is lowered in the lock position, raised in the lock position, lowered in the unlocked position, and raised in the unlocked position. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0039]    As illustrated in FIGS.  1 - 4 , the casing slip lifter of the preferred embodiment of the invention includes a frame  1  in the form of a base plate  2  having integral lateral railings  3  to enable transport and positioning of the frame adjacent to the rotary bushing, and a backplate  4  welded to a rear edge of the base plate  2 . Arm assembly supports  5  extend vertically from base plate  2  and are welded to edges of backplate  4  and to the base plate  2 . Air cylinder supports  6 , only one of which is shown in FIG. 2, extend vertically from and are welded to a forward portion of the base plate  2 . An arc-shaped reinforcement plate  7  having pin openings  8 , through which base plate  2  may be secured to the bushings using appropriately shaped pins (not shown), is fixed to an arc-shaped front edge portion of the base plate  2 . Arm assembly supports including openings  9  for receiving pipe-support bearings  15  (FIG. 5), and openings  10  for pivotably securing the upper arm assemblies illustrated in FIGS.  14 - 16  to the frame via supports  5 . Cylinder supports  6  include openings  11  for receiving cylinder coupling pins  12  (FIG. 1).  
         [0040]    Those skilled in the art will of course appreciate that the illustrated shapes and manner of attachment of the various frame pieces shown in FIG. 4 are not intended to be taken as limiting, and that the construction of the frame may be varied by those skilled in the art in a variety of ways without departing from the scope of the invention.  
         [0041]    As shown in FIGS.  5 - 8 , the lower arm assemblies  13  are each fixedly attached to a pipe shaft  14  supported by bearings  15  extending through openings  9  (FIG. 3) in support plates  5 . Each lower arm assembly  13  includes a first lower plate  16  pivotally coupled to a second lower plate  17  by means of pivot pin  18 . The second lower plate  17  is fixedly secured to a third lower plate  19 . First lower plate  16  includes an opening  20  for an end  21  of pipe shaft  14 , an opening  22  for securing a coupling pin  23  for cross-bar  24  (see FIGS. 17 and 26- 29 ), and an opening  25  for receiving the pivot pin  18 . Second lower plate  17  includes an opening  26  for the pivot pin  18 , and third lower plate  19  includes an opening  27  for receiving a pin  28  for pivotably coupling hinge plate  29  (FIGS. 17 and 26- 29 ) to the lower arm assembly  3 . Locking tabs  30 , whose function will be described below in connection with FIGS.  23 - 25 , extend laterally from each second lower plate  17 .  
         [0042]    As shown in FIGS. 5 and 9, a pair of cylinder arms  31  are fixedly attached to pipe shaft  14 . Each of the cylinder arms includes an opening for receiving the pipe shaft  14 , and distal openings  32  for receiving an air cylinder coupling pin  34  (FIG. 13). The cylinder arms  31  extend at a fixed angle with respect to first lower plates  16  such that when cylinder arms  31  are pushed by the air cylinders, shaft  4  is rotated to cause pivoting of lower arm assemblies  13 .  
         [0043]    As illustrated in FIGS.  10 - 12 , air cylinders  35  each includes a pair of arms  36  extending from a first end of the cylinder, a piston  37 , and a pair of arms  38  extending from the piston. One of the pairs of arms  36 ,  38  is secured to cylinder supports  6  by means of pins  12  extending through openings  11  (FIGS.  2 - 4 ) and corresponding openings  39  or  40  in the arms  36 ,  38 , and the other pair of arms  36 ,  38  is secured to the cylinder arm  31  by means of coupling pins  34  extending through openings  32  and corresponding openings  39  or  40 . It of course does not matter, for purpose of the general principles of the present invention, whether the piston is on the shaft-side or fixed-support-side of the cylinder, or whether dual pistons are included.  
         [0044]    As shown in FIGS.  13 - 17 , pivoting of the lower arm assemblies  13  causes pivoting of upper arm assemblies  42 , which are secured to the supports  5  by pins  43  extending though support openings  10  (FIG. 3) and openings  44  in first upper plates  45 . The upper arm assemblies  42  are coupled to the lower arm assemblies  13  by means of cross-bar  24  secured by coupling pins  46  extending through openings  22  in first lower plates  16  and corresponding openings in the cross bar  24 , and openings  47  in the first upper plates  45 . In addition, respective ones of the upper arm assemblies  42  are coupled to corresponding lower arm assemblies  13  by means of hinge plates  29  secured by coupling pins  48  extending through elongated openings  54  in third upper plates  49  and openings  66  in hinge plates  29 . Second upper plates  50  are pivotally secured to the first upper plates  45  by means of pivot pins  51  extending through respective openings  52  and  53  in the first and second upper plates, while third upper plates  49  are fixedly secured to second upper plates  50  by, for example, welding.  
         [0045]    As shown in FIGS. 18 and 19, hinge plates  29  each includes a planar section  56  to which is welded a pipe section  57 . The pipe section  57  is in turn welded to one of the alternative wrap arms  59 ,  60  and  58  respectively illustrated in FIGS. 21 and 22. Hinge plates  29  preferably include openings  61  and  62  for respectively receiving pins  28  and  48 .  
         [0046]    As illustrated in FIG. 21, wrap arm assembly  59 ,  60  includes wrap arms  59  and  60  secured together by hinge sections  63 ,  64 , which may take the form of a pair of plates  65  extending from one of the wrap arms and a single plate  64  extending from the other wrap arm into the space between the pair of plates, sections  63  and  64  being pivotably coupled by a pin  66 . Plates  67  and  68  extend from arm  59  and  60  in this embodiment to secure ends of a bias spring  69  (see FIG. 13), while grabber arm fixtures  70  are mounted on the wrap arms to secure grabber arms  71 , illustrated in FIG. 20. Grabber arms  71  include pipes  72  and bifurcated attachment structures  73  having openings  74  for receiving coupling pins (not shown) for coupling to a casing slip (also not shown) that is to be lowered into or raised out of bushing bowl  75 . Pipes  72  may be adjustably positioned in openings of fixtures  70  by set screws  77 , and threaded into the arm structures. Each of the wrap arms  59  and  60  may be formed by an arc-shaped section of rectangular pipe having a square cross-section and caps  78 , 79 .  
         [0047]    Alternatively, as illustrated in FIG. 22, wrap arms  59 ,  60  may be replaced by a single wrap arm  90  in the form of an arc-shaped section of pipe having a rectangular cross-section and caps  91  and  92 . It will be appreciated that the specific wrap arm and arm assembly configurations illustrated herein are not intended to be taken as limiting, and that the such details as materials and shapes may be varied in numerous ways by those skilled in the art without departing from the scope of the invention.  
         [0048]    As shown in FIGS. 17 and 23- 28 , the casing slip lifter of the preferred embodiment includes a lock mechanism that utilizes an ear lock  80  having a vertical leg  81  and a horizontal arm  82  for engaging and latching tab  30  in order to cause the second and third lower latch plates, and consequently the second and third upper latch plates, to pivot relative to each other and extend the vertical travel of the wrap arms  59 ,  60  or  58 , as illustrated in FIGS. 26 and 27. When the tab  30  is not latched, as illustrated in FIGS. 28 and 29, first, second, and third plates of the lower and upper arm assemblies  13  and  42  remain mutually stationary, resulting in reduced vertical travel, as illustrated in FIGS. 28 and 29. Pivoting of the ear lock  80  between the latched and unlatched positions is accomplished by mounting the ear locks on a rod  83  rotatably secured to the base plate  2  by bearing fixtures  84  actuated by handle  85 .  
         [0049]    Having thus described a preferred embodiment of the invention in sufficient detail to enable those skilled in the art to make and use the invention, it will nevertheless be appreciated that numerous variations and modifications of the illustrated embodiment may be made without departing from the spirit of the invention, and it is intended that the invention not be limited by the above description or accompanying drawings, but that it be defined solely in accordance with the appended claims.