Patent Publication Number: US-2007095575-A1

Title: Adjustable bent housing

Description:
FIELD OF THE INVENTION  
      The present invention relates to an adjustable bent housing used for deviating a drilling string when directional drilling.  
     BACKGROUND OF THE INVENTION  
      An adjustable bent housing is used to accommodate a drive shaft that connects a power section and a bit section of a down hole drilling motor. Canadian Patent 2,022,452 (Wenzel et al from 1990) illustrates a form of adjustable bent housing that has been in use for the past decade. The Wenzel et al reference allows adjustment to take place without changing the overall length of the housing. This is of importance, as it permits more rapid adjustment by the rig crew. If the length had to be increased in order for an adjustment to be made, the rotor of the power section would have to slide axially in the stator of the power section in order for an adjustment to be made.  
      A moineau-style power unit having a rotor and stator is generally used for the power section. In recent years there has been a trend to lengthen the power section by using longer rotors and stators. This has resulted in increased torque output, which has required that larger drive shafts be used. There is a limit as to the size of drive shaft that can be accommodated by the Wenzel et al adjustable bent housing.  
     SUMMARY OF THE INVENTION  
      What is required is an adjustable bent housing which can accommodate larger diameter drive shafts, while allowing adjustment to take place without changing the overall length of the housing.  
      According to the present invention there is provided an adjustable bent housing which includes a first tubular body and a second tubular body. The first tubular body has an internal surface defining a first portion of an interior bore and internal threads in the internal surface at one end. The second tubular body has an external surface, an internal surface defining a second portion of the interior bore, first external threads on the external surface at one end and second external threads on the external surface spaced from the first external threads. The one end of the second tubular body is adapted to telescopically extend into the one end of the first tubular body with the first external threads engaging the internal threads. Means is provided to create a first axial deviation in the first tubular body and means being provided to create a second axial deviation in the second tubular body, such that by relative rotation of the first tubular body and the second tubular body the first axial deviation and the second axial deviation can be either offset, made cumulative or set at an angular range between the offset and cumulative rotational positions. A locking sleeve is non-rotatably coupled with and slidably movable along the exterior surface of the second tubular body between a locking position and an adjusting position. The locking sleeve has an engagement face. In the locking position, the engagement face of the locking sleeve engages the one end of the first tubular body thereby preventing relative rotation of the first tubular body and the second tubular body. In the adjusting position, the locking sleeve is spaced from the one end of the first tubular body, thereby permitting relative rotation of the first tubular body and the second tubular body to occur. A locking nut is movable along the second external threads on the external surface of the second tubular body to selectively clamp the locking sleeve in the locking position.  
      The adjustable bent housing, as described above, provides a larger interior bore and a stronger body, while still allowing adjustment to take place with minimal change to the overall length of the housing.  
      The preferred embodiment, hereinafter described, has a number of further features which provide additional benefits. In the past, the incursion of drilling fluids have damaged engagement threads. In the preferred embodiment, all of the threads are sealed to prevent the incursion of drilling fluids. In the past, problems have been encountered in getting the locking sleeve to release. In the preferred embodiment, the locking nut and the locking sleeve have been coupled, so that the locking nut draws the locking sleeve from the locking position to the adjusting position. In the past, metal stress problems have been experienced. In the preferred embodiment, stress relief has been incorporated into the design. In the past, a spline engagement has been provided between the locking sleeve and the second tubular body. In the preferred embodiment, the same function is performed by a single locking key. This makes the adjustable bent housing easier and cheaper to manufacture, more robust, and easier to use in the field. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      These and other features of the invention will become more apparent from the following description in which reference is made to the appended drawings, the drawings are for the purpose of illustration only and are not intended to in any way limit the scope of the invention to the particular embodiment or embodiments shown, wherein:  
       FIG. 1  is a side elevation view, in section, of an adjustable bent housing constructed in accordance with the teachings of the present invention, in one adjustment position.  
       FIG. 2  is a side elevation view, in section, of the adjustable bent housing illustrated in  FIG. 1 , in another adjustment position.  
       FIG. 3  is a cross-section view of the adjustable bent housing illustrated in  FIG. 1 , taken across the locking sleeve.  
       FIGS. 4 and 5  are exploded side cross-section views of the adjustable bent housing showing alternative means of engaging the locking sleeve and the locking nut.  
       FIG. 6  is an exploded side cross-section view of the adjustable bent housing showing an alternative means of engaging the locking sleeve and the first tubular body.  
       FIG. 7  is a cross-section view taken of the adjustable bent housing across the locking sleeve showing an alternative locking means. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
      The preferred embodiment, an adjustable bent housing generally identified by reference numeral  10 , will now be described with reference to  FIGS. 1 through 7 .  
      Structure and Relationship of Parts:  
      Referring to  FIG. 1 , adjustable bent housing  10  includes a first tubular body  12  and a second tubular body  14 . First tubular body  12  has an internal surface  16  defining a first portion  18  of an interior bore  20  and internal threads  22  in internal surface  16  at one end. Second tubular body  14  has an external surface  24 , an internal surface  26  defining a second portion  28  of interior bore  20 , first external threads  30  on external surface  24  at one end and second external threads  32  on external surface  24  spaced from first external threads  30 . The one end of second tubular body  14  is adapted to telescopically extend into the one end of first tubular body  12  with first external threads  30  engaging internal threads  22 . A seal  52  is positioned at the one end of second tubular body  14  between internal surface  16  of first tubular body  12  and external surface  24  of second tubular body  14  to prevent drilling fluids passing along interior bore  20  from getting into first external threads  30 .  
      As is known to persons skilled in the art, means must be provided to create a first axial deviation  34  (shown in dotted lines) in first tubular body. Similarly, means must be provided to create a second axial deviation  36  (shown in dotted lines) in second tubular body  38 . Upon relative rotation of first tubular body  12  and second tubular body  14 , first axial deviation  34  and second axial deviation  36  can be either offset, made cumulative or set at an angular range between the offset and cumulative rotational positions. Referring to  FIG. 2 , the changes are shown to be cumulative. The manner of creating such axial deviations is known in the art and will not be described in any great detail. The means to create first axial deviation  34  may include one or more of: machining first tubular body  12  to create an inherent deviation or machining internal threads  22  with an inherent deviation or machining the one end of first tubular body  12  with an inherent deviation. The means provided to create the second axial deviation  36  may include one or more of: machining second tubular body  14  to create an inherent deviation or machining first external threads  30  with an inherent deviation or machining engagement face  46  on locking sleeve  44  with an inherent deviation. The apparatus is designed such that changes in internal and external diameter should be curved to accommodate limited flexing and provide stress relief.  
      Referring now to  FIG. 1 , a locking sleeve  44  is non-rotatably coupled with, and slidably movable along, exterior surface  24  of second tubular body  14  between a locking position and an adjusting position. Referring to  FIG. 3 , locking sleeve  44  is non-rotatably secured to external surface  24  of second tubular body  14  by a single key  54 , although more may be used. Referring now to  FIG. 7 , splines  55  may be used to non-rotatably secure locking sleeve  44  to external surface  24  instead of a key  54 . While four splines are shown, any convenient number could be used. Referring again to  FIG. 3 , locking sleeve  44  has an engagement face  46 . Referring again to  FIG. 1 , in the locking position, engagement face  46  of locking sleeve  44  engages the one end of first tubular body  12  thereby preventing relative rotation of first tubular body  12  and second tubular body  14 . In the adjusting position, locking sleeve  44  is spaced from the one end of first tubular body  12 , thereby permitting relative rotation of first tubular body  12  and second tubular  14  body to occur. A locking nut  48  is movable along second external threads  32  on external surface  24  of second tubular body  14  to selectively clamp locking sleeve  44  in the locking position. An engagement, such as a retaining ring  50 , is provided between locking nut  48  and locking sleeve  44 , so that locking nut  48  is used to pull locking sleeve  44  from the locking position to the adjusting position. Referring to  FIG. 4 , flexible fingers  51  which extend from locking nut  48  into locking sleeve  44  may also be used as an engagement. Flexible fingers  44  may also extend from locking sleeve  44  to locking nut  48  instead. Referring to  FIG. 5 , an arrangement using balls  53  in corresponding grooves  55  and  57  in locking sleeve  44  and locking nut  48 , respectively will also provide the necessary engagement. Referring again to  FIG. 1 , an interlocking engagement  56  in the form of teeth  58  is provided between engagement face  46  of locking sleeve  44  and the one end of first tubular body  12 . Referring to  FIG. 6 , pins  59  may also be used as interlocking engagement  56  instead of teeth  58 . Referring again to  FIG. 1 , a seal  60  is positioned between an internal face  62  at a remote end of locking nut  48  and second tubular body  14  to prevent drilling fluids passing along second tubular body  14  from getting into second external threads  32 .  
      Operation:  
      The use of adjustable bent housing  10  will now be discussed with reference to  FIGS. 1 through 7 . When an adjustment is desired, adjustable bent housing  10  is brought above the surface of the Earth. Referring to  FIG. 1 , locking nut  48  is rotated along threads  32  and, as it is engaged to locking sleeve  44  through retaining ring  50 , locking sleeve  44  is moved in the same direction as locking nut  48 , such that locking sleeve  44  slides along key  54 . This is continued until interlocking engagement  56  is disengaged from engagement face  46 . First and second tubular bodies  12  and  14  are then free to be rotated along threads  22  and  30  to adjust the angle of adjustable bent housing  10  through axial deviations  34  and/or  36 .  FIG. 2  shows an example where both axial deviations  34  and  36  are used to cause a greater angle adjustment. Once the desired angle is achieved, locking nut  48  is then tightened again such that locking sleeve returns to it original position, with interlocking engagement  56  engaged.  
      In this patent document, the word “comprising” is used in its non-limiting sense to mean that items following the word are included, but items not specifically mentioned are not excluded. A reference to an element by the indefinite article “a” does not exclude the possibility that more than one of the element is present, unless the context clearly requires that there be one and only one of the elements.  
      It will be apparent to one skilled in the art that modifications may be made to the illustrated embodiment without departing from the spirit and scope of the invention as hereinafter defined in the claims.