Abstract:
A tool which connects the last sucker rod of a sucker rod string to a downhole pump has a circularly cylindrical cylinder and piston so that the piston slides reciprocally and rotates freely within the cylinder. However, the closed upper end of the cylinder and the upper face of the piston have a cooperable tongue and groove which prevent relative rotational motion of the piston in the cylinder when the tongue is engaged in the groove so that the tool can be disconnected from the pump in response to rotation of the string at the uppermost stroke of the plunger to engage and turn the tongue and groove.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    This invention relates generally to equipment used in producing fluid from a well and more particularly concerns tools to enhance the operation of downhole reciprocating pumps. 
         [0002]    U.S. Pat. No. 6,068,052, issued to the present inventor on May 30, 2000, explains the common practice and problems of “tapping” and discloses a no tap tool for downhole reciprocating pumps. That tool eliminates the need for “tapping” in the operation of a downhole pump, reduces the unidirectional application of force to the plunger of a downhole pump and allows the plunger to take the path of least resistance to overcome a “stuck” condition. 
         [0003]    The tool is connectable between the last sucker rod of the sucker rod string and the downhole pump. A cylinder with a closed end and an internal annular seat proximate an open end houses a piston which reciprocates slidably within the cylinder and is free to rotate within the cylinder. The tool components are concentric about the longitudinal axis of the tool, so the tool components are independently free to rotate about the tool axis, allowing the plunger of the pump to rotate to the path of least resistance to achieve its freedom, thereby further reducing the forces exerted on the system components. 
         [0004]    The freedom of the tool components to independently rotate is one of the keys to the success of this “old” tool. However, because of this freedom of the tool components to independently rotate, use of the tool in the string renders the tool and any of the equipment downhole of the tool irretrievable without retrieval of all of the equipment downhole of the tool. 
         [0005]    It is, therefore, an object of this invention to provide a no tap tool which affords the benefits of the “old” tool. To this end, it is also an object of this invention to provide a no tap tool which utilizes independently rotating components. But, it is a further object of this invention to provide a no tap tool which does not prevent retrieval of equipment downhole of the tool. 
     
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0006]    Other objects and advantages of the invention will become apparent upon reading the following detailed description and upon reference to the drawings in which: 
           [0007]      FIG. 1  is a diametric cross section of a preferred embodiment of the no-tap tool; 
           [0008]      FIG. 2  is an elevation view of the upper portion of the piston of the tool of  FIG. 1 ; 
           [0009]      FIG. 3  is a cross-sectional view taken along the line  3 - 3  of  FIG. 1 ; 
           [0010]      FIG. 4  is a cross-sectional view taken along the line  4 - 4  of  FIG. 1 ; and 
           [0011]      FIG. 5  is a cross-sectional view taken along the line  5 - 5  of  FIG. 1 . 
       
    
    
       [0012]    While the invention will be described in connection with a preferred embodiment, it will be understood that it is not intended to limit the invention to that embodiment. On the contrary, it is intended to cover all alternatives, modifications and equivalents as may be included within the spirit and scope of the invention as defined by the appended claims. 
       SUMMARY OF THE INVENTION 
       [0013]    In accordance with the invention, a tool is provided for connection between the last sucker rod of a sucker rod string and a downhole pump. A circular cylinder has a closed upper end which is externally adapted for connection to the last sucker rod of the sucker rod string. A circular cylindrical piston slides reciprocally and rotates freely within the cylinder. The piston has a lower portion which extends through an open lower end of the cylinder and is adapted for connection to the pump. The closed upper end of the cylinder and the upper face of the piston have a cooperable tongue and groove which prevent relative rotational motion of the piston in the cylinder when the tongue is engaged in the groove. Preferably, the tongue and groove are of rectangular cross section, are diametric in relation to the cylinder and piston and the groove is sufficiently wider than the tongue to facilitate their engagement. 
         [0014]    In a preferred embodiment, the cylinder is concentric about a vertical longitudinal axis and has an internally threaded upper portion, a smooth middle portion and a lower portion of inner diameter less than the inner diameter of the middle portion so as to form an annular seat at a junction of the cylinder middle and lower portions. The piston is a plunger which is concentric about the vertical longitudinal axis and has an externally threaded lower portion adapted to be coupled to the pump, a smooth middle portion and a smooth upper portion with a horizontal end face and an outer diameter greater than an outer diameter of the middle portion so as to form an annular stop at a junction of the plunger middle and upper portions. The plunger upper portion slides reciprocally and rotates within the cylinder middle portion and the stop and seat are cooperable to limit the lowermost travel of the plunger upper portion within the cylinder. A pin concentric about the vertical longitudinal axis has an externally threaded lower portion with a horizontal end face engaged in the internally threaded upper portion of the cylinder, a middle portion of outer diameter greater than an inner diameter of the plunger so as to position the pin end face at the top of the cylinder middle portion when the pin lower portion is fully threaded into the cylinder upper portion and an externally threaded upper portion adapted for engagement with the last sucker rod of the sucker rod string. The pin and plunger end faces are cooperable to limit the uppermost travel of the plunger upper portion within the cylinder with the plunger lower portion extending below the cylinder lower portion. The horizontal end face of the pin has a diametric groove therein and the plunger upper portion horizontal end face has a diametric tongue thereon. The tongue and groove are cooperable to disconnect the tool from the pump in response to rotation of the string to engage and turn the tongue and groove at the uppermost stroke of the plunger. 
       DETAILED DESCRIPTION 
       [0015]    Turning to  FIGS. 1 through 5 , the tool consists of a cylinder  30 , a piston or plunger  50  and a pin  70 , all concentrically aligned on a vertical longitudinal axis  27 . 
         [0016]    In the preferred embodiment shown, the cylinder  30  has an internally threaded upper portion  31 , a smooth middle portion  33  and a lower portion  35 . The lower portion  35  has an inner diameter less than the inner diameter of the middle portion  33  so as to define an internal annular seat  37  at the junction of the middle and lower portions  33  and  35  of the cylinder  30 . At least one aperture  41  is provided through the upper side wall of the middle portion  33  of the cylinder  30 , preferably substantially immediately below the top of the middle portion  33  of the cylinder  30 . At least one aperture  43  is also provided through the lower side wall of the middle portion  33  of the cylinder  30 , preferably substantially immediately above the internal seat  37 . Preferably, four upper apertures  41  and four lower apertures  43  will be substantially equally spaced about the circumference of the cylinder  30 . 
         [0017]    The piston or plunger  50  has a smooth upper portion  51 , a smooth middle portion  53  and an externally threaded lower portion  55 . The outer diameter of the middle portion  53  is less than the outer diameter of the upper portion  51 , thus providing a stop  57  which cooperates with the seat  37  of the cylinder  30  to limit the lowermost travel of the downstroke of the piston  50  within the cylinder  30 . The length of the middle portion  53  of the piston  50  is such that the upper portion  51  of the piston  50  can reciprocate from the top to the bottom of the middle portion  33  of the cylinder  30  with the lower threaded portion  55  of the piston  50  extending below the bottom of the cylinder  30 . Since the components of the cylinder  30  and the components of the piston  50  are all concentric, the piston  50  may be slidably reciprocated along the tool axis  27  and is also free to rotate within the cylinder  30  about the tool axis  27 . As shown, the middle portion  53  of the piston  50  is provided with tooling flats  61 . 
         [0018]    As best seen in  FIGS. 1 and 2 , a diametric tongue  63  extends upwardly from the upper face  59  of the piston  50 . The tongue  63  shown is, looking at  FIG. 1 , rectangular in cross-section, but is most easily formed by use of a rotating cutter so that the upper face  59  of the piston  50  is, looking at  FIG. 2 , arcuate. Other cross-sections and machining methods may be used, however, and the upper face  59  of the piston  50  may be in a horizontal plane. The upper face  65  of the tongue  63  is, preferably, in a horizontal plane, as is hereafter explained. 
         [0019]    The pin  70  has an externally threaded lower portion  71  which engages within the internal threads of the upper portion  31  of the cylinder  30 . the middle portion  73  of the pin  70  has an outer diameter which is greater than the inner diameter of the upper portion  31  of the cylinder  30  so that, when the pin  70  is fully threaded into the cylinder  30 , the middle portion  73  of the pin engages the upper end of the cylinder  30  and sets the horizontal lower face  75  of the pin  70  at the junction of the upper and middle portions  31  and  33  of the cylinder  30 . the upper portion  77  of the pin  70  is externally threaded for engagement with a polish rod coupling at the lowermost end of the sucker rod string. The pin  70  closes the upper end of the cylinder  30  and the lower horizontal face  75  of the pin  70  is cooperable with the upper face  59  of the piston to limit the uppermost travel of the piston  50  within the cylinder  30 . As shown, the middle portion  73  of the pin  70  is provided with tooling flats  81 . 
         [0020]    As best seen in  FIGS. 1 and 5 , a diametric groove  83  extends upwardly into the lower horizontal face  75  of the threaded lower portion of the pin  70 . The groove  83  in the pin  70  is wider than the tongue  63  of the piston  50 . The difference should be sufficient to facilitate engagement of the tongue  63  in the groove  83  even if the tongue  63  is slightly flared or debris may have collected in the path of engagement. 
         [0021]    In operation, the tool is mounted between the lowermost sucker rod and the pump. The stroke of the plunger in the pump is set so that the plunger does not strike the pump at the bottom of its stroke. However, during the reciprocation of the sucker rod string, as the cylinder  30  is reciprocated, the upper face  65  of the tongue  63  of the piston  50  strikes the lower face  75  of the pin  70  and the stop  57  of the piston  50  strikes the seat  347  in the cylinder  30 , resulting in cyclical upward and downward impact n the pump plunger without impacting the pump. At the same time, the piston  50  and therefore the plunger which is attached to it, are free to rotate about the tool longitudinal axis  27 , thus allowing the plunger to take the path of least resistance and resulting in minimal force being exerted on the other system components while the plunger is freed from a stuck condition. 
         [0022]    Since the piston  50  is free to rotate in the cylinder  30 , it is possible but relatively uncommon that the piston tongue  63  will align with the groove  83  in the pin  70  during normal operation of the tool. Generally, the upper horizontal face  65  of the tongue  63  will strike the lower horizontal face  75  of the pin  70 . However, even if this rare event should occur, the minimal duration of any penetration of the tongue  63  into the groove  83  will have no substantial effect on the freedom of rotation during normal operation. The tool is presented as seen in  FIG. 1  to illustrate the intentional alignment of the tongue  63  and groove  83  so that the tool can be disengaged from the downhole equipment for retrieval of the tool without the equipment. This is accomplished by an intentional rotation of the string and, therefore, the tool pin  70  at the top of the stroke. As the groove  83  rotates it comes into alignment with the tongue  63  and the upward inertia of the tongue  63  causes it to engage in the groove  83  and turn the tool. The opposite rotation of the string can be used as a tool is lowered to engage the tongue  63  and groove  83  and permit connection of the tool to downhole equipment. 
         [0023]    While, in the preferred embodiment, the piston  50  extends through the open lower end of the cylinder  30 , the tool could be inverted and the piston  50  adapted for connection to the sucker rod string and the pin  70  adapted for connection to the pump. 
         [0024]    Thus, it is apparent that there has been provided, in accordance with the invention, a no-tap tool that fully satisfies the objects, aims and advantages set forth above. While the invention has been described in conjunction with specific embodiments thereof, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art and in light of the foregoing description. Accordingly, it is intended to embrace all such alternatives, modifications and variations as fall within the spirit of the appended claims.