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CROSS REFERENCE TO RELATED APPLICATION 
   This application is a continuation-in-part of pending U.S. patent application Ser. No. 09/962,105 filed on Sep. 26, 2001, now U.S. Pat. No. 6,681,853, filed as a CIP of U.S. patent application Ser. No. 09/517,555 filed Mar. 2, 2000, now U.S. Pat. No. 6,318,462 and issued Nov. 20, 2001, the entirety of which is incorporated herein by reference. 

   FIELD OF THE INVENTION 
   The invention relates to a tool for preventing rotation of a tubing string or progressive cavity pump in the bore of a casing string. 
   BACKGROUND OF THE INVENTION 
   Oil is often pumped from a subterranean reservoir using a progressive cavity (PC) pump. The stator of the PC pump is threaded onto the bottom of a long assembled string of sectional tubing. A rod string extends downhole and drives the PC pump rotor. Large reaction or rotor rotational forces can cause the tubing or PC pump stator to unthread, resulting in loss of the pump or tubing string. 
   Anti-rotation tools are known including Canadian Patent 1,274,470 to J. L. Weber and U.S. Pat. No. 5,275,239 to M. Obrejanu. These tools use a plurality of moving components, slips and springs to anchor and centralize the PC Pump stator in the well casing. 
   Further, the eccentric rotation of the PC Pump rotor imposes cyclical motion of the PC Pump stator, which in many cases is supported or restrained solely by the tool&#39;s slips. Occasionally a stabilizing tool is added to dampen or restrain the cyclical motion to failure of the anti-rotation tool. 
   SUMMARY OF THE INVENTION 
   A simplified anti-rotation tool is provided, having only one jaw as a moving part but which both prevents rotation and stabilizes that to which it is connected. In simplistic terms, the tool connects to a progressive cavity (PC) pump or other downhole tool. Upon rotation of the tool in one direction a jaw, which is biased outwardly from the tool housing, engages the casing wall to arrest tool rotation. This action causes the tool housing to move oppositely and come to rest against the casing opposing the jaw. The tool housing and the downhole tool are thereby restrained and stabilized by the casing wall. 
   In a broad apparatus aspect, an anti-rotation tool comprises: a tubular housing having a bore and having at least one end for connection to a downhole tool and a jaw having a hinge and a radial tip. The jaw is pivoted at its hinge from one side of the housing, so that the jaw is biased so as to pivot outwardly to a first casing-engaging position, wherein the radial tip engages the casing, and the housing is urged against the casing opposite the jaw. The jaw is also inwardly pivotable to a second compressed position towards the housing to enable movement within the casing during tripping in and tripping out. 
   Preferably, the jaw is biased to the casing-engaging position by a torsional member extending through the hinge, which is rigidly connected to the housing at a first end and to the jaw at a second end. Compression of the jaw twists the torsional member into torsion which then acts to bias or urge the jaw outwardly again. 
   Preferably, the swing of the jaw is arranged for tools having conventional threaded connections wherein the jaw is actuated under clockwise rotation and is compressed by counter clockwise rotation of the tool. 
   More preferably, the jaw is formed separately from the housing so that the housing and bore remain independent and the bore can conduct fluid. 
   Preferably, overextension of the jaw during assembly is prevented using cooperating stops in the jaw and the housing. In a broad aspect, a downhole tool comprises a tubular housing for suspension in a wellbore casing and having a wall which engages the wellbore casing and having at least one end for threaded connection to the downhole tool, a jaw having a radial tip and which is rotatable along an axis along a base of the jaw and along a hinge on wall of the housing opposing the casing engaging wall for varying the effective diameter of the tool, a first stop formed on the base of the jaw, and a second stop formed in the wall of the housing at the hinge. The first and second stops co-operate so as to limit maximum rotation of the jaw, while permiting the effective diameter of the tool to increase to a diameter greater than the casing. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIGS. 1   a  and  1   b  are isometric views of one embodiment of the tool showing the jaw with its radial tip in its extended position ( FIG. 1   a ) and the stored position ( FIG. 1   b ); 
       FIG. 1   c  is a side view of an optional housing embodiment in which the threaded portion has its center offset from the housing center; 
       FIG. 2  is an enlarged view of the hinge pin, inset into the housing before welding to the housing; 
       FIGS. 3   a  and  3   b  are cross sectional views of the tool through the hinge, illustrating the jaw open and engaging the casing ( FIG. 3   a ) and closed for installation ( FIG. 3   b ); 
       FIG. 4  is an isometric view of a third embodiment of the tool showing the jaw with its radial tip in its extended position; and 
       FIGS. 5   a  and  5   b  are cross sectional views of the tool according to  FIG. 4 , viewed through the hinge with the jaw open and engaging the casing ( FIG. 5   a ) and closed for installation ( FIG. 5   b ). 
       FIGS. 6   a , is an isometric view of another embodiment of the anti-rotation tool of the present invention showing the jaw with its radial tip in its extended position; 
       FIG. 6   b  is an isometric view according to  FIG. 6   a  with the jaw removed to show the orientation of a hinge spring in the extended position; 
       FIG. 7  is a perspective view of the jaw of  FIG. 6   a , removed from the housing; 
       FIG. 8  is a perspective view of a stationary hinge spring holder according to  FIG. 6   a;    
       FIG. 9  is a perspective view of a rotational hinge spring holder and retaining pin according to  FIG. 6   a;    
       FIG. 10   a  is a perspective view of the hinge spring and first and second end spring holders showing their respective orientation when the jaw has been biased to its to extended position; 
       FIG. 10   b  is a perspective view of the hinge spring and first and second end spring holders showing their respective orientation when the jaw is urged against the spring to the closed position; 
       FIGS. 11   a  and  11   b  are cross sectional views of the tool through the hinge, illustrating the jaw open and engaging the casing and showing the ends of the hinge spring substantially aligned at the first and second spring holders (FIG.  10   a ) and then compressed for tripping in and tripping out ( FIG. 10   b ), showing the ends of the hinge spring out of plane as the hinge spring is in torsion; 
       FIG. 12  is cross sectional view of another embodiment of the tool through the hinge, illustrating the co-operating stops on the jaw and housing; 
       FIG. 13  is an exploded perspective view of the embodiment of  FIG. 12 ; 
       FIG. 14   a  is perspective view of the embodiment of  FIG. 12  inside a casing; 
       FIG. 14   b  is a cross-sectional view of the embodiment of  FIG. 12  inside a partial section of casing; and 
       FIG. 14   c  is a close-up partial cross-section of the jaw of  FIG. 14   b.    
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   Having reference generally to  FIGS. 1   a,    1   b,    5   a , and  5   b , a tool  10  is provided for preventing rotation relative to casing  6  in a wellbore. The tool  10  comprises a tubular housing  1  with a bore  2 . The bore  2  has at least one threaded end  3  for connection to a downhole tool such as the bottom of a PC pump (not shown). A jaw  5  is pivotably mounted to the housing  1  and swings between a stowed position ( FIGS. 1   b ,  5   b ) and a casing-engaging position ( FIGS. 1   a,    5   a ). 
   In a first embodiment, as illustrated in  FIGS. 1   a – 3   b , the jaw  5  pivots out of the housing, interrupting the housing and opening the bore to the wellbore. As a variation of the first embodiment, a second embodiment demonstrates a specialized housing which centralizes the bore in the wellbore, as illustrated in  FIG. 1   c.  In a third embodiment, an alternate arrangement of the jaw is shown which does not compromise the tool&#39;s housing or bore. 
   More particularly, in the first embodiment and having reference to  FIGS. 1   a,    1   b,    3   a  and  3   b  a portion of the housing wall  4  is cut through to the bore  2  to form a trapezoidal flap or jaw  5 . The jaw  5  has an arcuate profile, as viewed in cross-section, which corresponds to the curvature of the housing wall  4 . Accordingly, when stowed, the jaw  5  projects minimally from the tubular housing  1  and avoids interfering with obstructions while running into the casing  6  ( FIG. 3   b ). 
   Referring to  FIGS. 1   a – 2 , the jaw  5  is pivoted to the housing  1  along a circumferential edge  7  at hinge  30 . The jaw  5  has a radial tip edge  11 . 
   Hinge  30  comprises tubing  9  welded to the hinge edge  7  with a pin  8  inserted therethrough. Pin  8  is welded to the housing wall  4  at its ends. In a mirrored and optional arrangement (not shown), the jaw&#39;s hinge edge  7  has axially projecting pins and the housing wall is formed with two corresponding and small tubular sockets for pinning the pins to the housing and permitting free rotation of the jaw therefrom. 
   The hinge edge  7  and hinge  30  are formed flush with the tubular housing wall  4 . 
   The running in and tripping out of the tool  10  is improved by using a trapezoidal jaw  5 , formed by sloping the top and bottom edges  12 , 13  of the jaw  5 . The hinge edge  7  is longer than the radial tip edge  11 . Accordingly, should the radial tip  11  swing out during running in or tripping out of the tool  10 , then incidental contact of the angled bottom or top edges  12 , 13  with an obstruction causes the jaw  5  to rotate to the stowed and non-interfering position. 
   The jaw&#39;s radial tip  11  can have a carbide tip insert  14  for improved bite into the casing  6  when actuated. 
   If the wall thickness of the jaw  5 , typically formed of the tubular housing wall  4 , is insufficient to withstand the anchoring stress, then a strengthening member  15  can be fastened across the chord of the radial tip  11  to the hinge edge  7 . 
   The strengthening member  15  can include, as shown in  FIGS. 3   a ,  3   b , a piece of tool steel or the equivalent which substitutes for the carbide insert. 
   In operation, the tool  10  is set by clockwise rotation so that the jaw  5  rotates out as an inertial response and is released simply by using counter-clockwise rotation. Specifically, as shown in  FIG. 3   b , when the tool is rotated counter-clockwise as viewed from the top, the jaw&#39;s radial tip edge  11  rotates radially inwardly and becomes stowed flush with the housing wall  4 , minimizing the width or effective diameter of the tool  10 . Conversely, as shown in  FIG. 3   a , when the tool  1  is rotated clockwise as viewed from the top, the jaw  5  rotates radially outwardly from the housing  1 , increasing the effective diameter of the tool  10 , and the radial tip engages the casing  6 . Further, the housing  1  is caused to move in an opposing manner and also engages the casing  6  opposite the jaw  5 , the effective diameter being greater than the diameter of the casing  6 . 
   Significant advantage is achieved by the causing the tool&#39;s housing  1  and its associated downhole tool (PC Pump) to rest against the casing  6 . The casing-engaged jaw  5  creates a strong anchoring force which firmly presses the tool housing  1  and the PC Pump stator into the casing  6 . Accordingly, lateral movement of the PC Pump is restricted, stabilizing the PC Pump&#39;s stator against movement caused by the eccentric movement of its rotor. It has been determined that the stabilizing characteristic of the tool  10  can obviate the requirement for secondary stabilizing means. 
   Referring back to  FIG. 1   c,  in an optional second embodiment, the threaded end  3  can be formed off-center to the axis of the housing  1 , so that when the radial tip  11  engages the casing  6 , the axis of the threaded end  3  is closer to the center of the casing  6  than is the axis of the housing  1 . This option is useful if the PC Pump or other downhole tool requires centralization. 
   In the first and second embodiment, the jaw  5  is conveniently formed of the housing wall  4 , however, this also opens the bore  2  to the wellbore. If the tool  10  threaded to the bottom of a PC Pump, this opening of the bore  2  is usually irrelevant. However, where the bore  2  must support differential pressure, such as when the PC Pump suction is through a long fluid conducting tailpiece, or the tool  10  is secured to the top of the PC Pump and must pass pressurized fluids, the bore  2  must remain sealed. 
   Accordingly, and having reference to  FIGS. 4–5   b , in a third embodiment, the housing wall  4  is not interfered with so that the bore  2  remains separate from the wellbore. This is achieved by mounting the jaw  5  external to the housing  1 . The profile of jaw  5  conforms to the housing wall  4  so as to maintain as low a profile as possible when stowed ( FIG. 5   b ). 
   More specifically as shown in  FIG. 4 , as was the case in the first embodiment, the profile of the jaw  5  corresponds to the profile of the housing wall  4 . In this embodiment however, the jaw  5  is pivoted along its circumferential edge  7  at a piano-type hinge  30  mounted external to the housing wall  4 . Corresponding sockets  9  are formed through the circumferential edge of the jaw and the hinge  30 . Pin  8  is inserted through the sockets  9 . A carbide insert  14  is fitted to the radial tip edge  11  of the jaw  5 . 
   In operation, as shown in  FIG. 5   a , if the tool  1  is rotated clockwise as viewed from the top, the radial tip edge  11  of the jaw rotates radially outwardly from the housing and the carbide insert  14  engages the casing  6 . The housing wall  4  moves and also engages the casing  6 , opposite the jaw  5  for anchoring and stabilizing the tool. As shown in  FIGS. 3   a  and  5   a , the overall dimension of the extended jaw  5  and the housing  1  is greater than the diameter of the casing  6  so that contact of the radial tip edge  11  with the casing  6  forces the housing against the casing opposing the jaw. 
   As shown in  FIG. 5   b , if the tool is rotated counter-clockwise as viewed from the top, the jaw&#39;s radial tip edge  11  rotates radially inwardly and becomes stowed against the housing wall  4 . 
   Having reference to  FIGS. 6   a – 11   b,  in a fourth embodiment, a novel jaw  105  is provided, which is biased outwardly from the housing  1 . The jaw  105  is pivotally connected to wall of the housing  1  with a hinge  107 , the hinge  107  having first and second ends  113 , 114  and which lies along a rotational axis. The jaw  105  comprises a tubular conduit  120 , having first and second ends  109 ,  110 , formed along edge  106 , which co-operates with a linearly extending, flexible torsional member  121 , shown as having a rectangular section, to bias hinge  107  and jaw  105  outwardly from the housing  1 . The torsional member or spring  121  extends through the tubular conduit  120  and is attached to the tool housing  1  using a first hinge spring holder  122 , and to the jaw  105  using a second hinge spring holder  123 . A preferred hinge utilizes a coupled pin and cavity arrangement at each end of the jaw  105 . 
   One of either the first or second spring holders  122 , 123  rigidly connects a first end  124  of the hinge spring  121  to the housing  1 , preventing it from rotating with the pivoting jaw  105 . The other spring hinge holder  123 ,  122  rotatably connects a second end  125  of the hinge spring  121  to the housing  1 , causing it to rotate therein, with the jaw  105 . Accordingly, as the jaw  105  is rotated from the outwardly extending position to a more compressed position, the hinge spring  121  is twisted into torsion. 
   As shown in  FIGS. 6   b  and  8 , a first stationary spring holder  130 , fixes the spring&#39;s first end  124  to the tool housing  1 . The stationary spring holder  130  comprises a body  131  having a tubular shaped edge  132 , corresponding to the tubular conduit  120  of the jaw  105 . The body  131  further comprises a counter-sunk screw hole  135  for attaching the stationary holder  130  to the housing  1 , using a suitable fastener  136 . A cylindrical retaining pin  133  extends outwards from the holder&#39;s tubular edge  132 , along the same axis, for insertion into the cavity of the jaw&#39;s tubular conduit  120 . A spring-retaining slot  134  is formed in the retaining pin  133  for engaging the hinge spring&#39;s first end  124 . The orientation of the slot  134  relative to the pin  133  is such that when the stationary holder  130  is affixed to the housing  1 , the jaw  105  is biased to the outwardly extending position. 
   Having reference to  FIGS. 6   b  and  9 , a second rotating spring holder  140  is shown, which fixes the spring  121  to the jaw  105 . The rotating holder  140  comprises a body  141  having a tubular edge  142 , corresponding to the jaw&#39;s tubular conduit  120 . The tubular edge  142  has a bore  143 . The body  141  further comprises a counter-sunk screw hole  149  for attachment of the holder  140  to the housing  1 , using a suitable fastener  136 . A connector body  144  comprises a first end or retaining pin  145 , which extends into the cavity or bore  143  for free rotation therein, enabling pivoting of the hinge  107 . The connector body  144  further comprises a profiled middle portion  146  (such as an oval or polygonal shape; hexagonal shown) which is inserted into and co-operates with a correspondingly profiled first end  109  of the jaw&#39;s conduit  120 , to rotationally fix connector body  144  to the jaw  105 . Lastly the connector body  144  has a spring-retaining end  147 . The spring retaining end  147  further comprises a slot  148  for retaining the hinge spring&#39;s second end  125 . 
   As shown in  FIG. 10   a,  the hinge spring  121  attached to the housing  1  and the jaw  105  (partially shown—hidden lines) is oriented with the first and second ends  124 ,  125  in the same plane, biasing the jaw  105  to the open outwardly extending position as a result of the orientation of the spring  121  relative to the stationary hinge spring holder  122 . Further, showing the spring action in greater detail in  FIG. 10   b,  when the jaw  105  (hidden lines) is urged to a more compressed position, the stationary holder  122  retains the spring&#39;s first end  124  orientation, however, the rotating spring holder  123  allows the spring&#39;s second end  125  to be rotated with the jaw  105 . Rotation of the spring&#39;s second end  125 , as the jaw  105  is compressed, twists the spring  121  into torsion. As soon as the force causing the jaw  105  to pivot to the compressed position is released, the spring  121  biases the jaw  105  to return the jaw  105  to the casing-engaging position once again. 
   Further, the preferred construction of the hinge  107  avoids supporting loads imposed on the jaw  105  when in the casing-engaging position. The jaw&#39;s conduit  120  and the bore  143  of the rotational spring holder are both oversized relative to their respective retaining pins  133 ,  145 , allowing limited lateral movement of the jaw  105  relative to the housing  1  without interfering with the jaw&#39;s pivoting action. Accordingly, when the jaw is in the outwardly extended, casing engaging position, the reaction on the jaw  105  drives the jaw sufficiently into the housing  1  so that the back of the tubular conduit  120  at edge  106  engages the housing  1 , transferring substantially all of the forces directly from the jaw  105  to the housing  1 , and avoiding stressing of the retaining pins  133 ,  145  and spring holders  122 ,  123 . 
   In operation, as shown, viewed from the top, in  FIGS. 11   a  and  11   b,  the tool  10  is set into a casing  6  by clockwise rotation with the jaw  105  in the biased open position and is released from the casing  6  simply by using counter-clockwise rotation, contact of the jaw  105  and casing to compressing the jaw  105  towards the housing  1 . Specifically, as shown in  FIG. 11   b,  when the tool  10  is rotated counter-clockwise, the interaction of the jaw  105  and casing  6  causes the jaw to pivot inwardly towards the housing  1 , minimizing the width or effective diameter of the tool  10 . The inward rotation of the jaw  105  causes the hinge spring&#39;s rotational end  125  to rotate relative to the hinge spring&#39;s stationary end  124 , putting the hinge spring  121  into torsion. Conversely, as shown in  FIG. 11   a , when the jaw  105  is not being compressed, such as when the tool  10  is at rest or when rotated clockwise, the jaw  105  is biased outwardly by the hinge spring  121  to return to the outwardly extending casing-engaging position, increasing the effective diameter of the tool  10 . The radial tip  11  engages the casing  6  and the housing  1  is caused to move in an opposing manner so as to engage the casing  6  and brace itself opposite the jaw  105 , the effective diameter being greater than the diameter of the casing  6 . 
   Having reference to  FIGS. 13 and 14   a–c , another embodiment of the tool  10  is shown wherein a stop  200  on the jaw  105  co-operates with a stop  202  in the housing  1  to arrest rotation of the jaw  105  and thereby restrict the amount the jaw  105  rotates radially outwardly from the housing  1 , and to provide additional strength to the entire tool  10  so as to prevent damage which may occur when using power tongs or similar tools during the assembly of the tool  10  on the end of a tubing string or a specific downhole tool. Torque applied to jaw  105  can result in the jaw  105  being over-torqued without some means to stop its rotation. 
   The jaw  105  can rotate outwardly to increase the effective diameter of the tool  10  to a diameter greater than the casing  6 . Accordingly the stops  200 ,  202  are radially spaced sufficiently so as to be inoperative in service and the stops  200 ,  202  do not restrict movement of the jaw  105  under normal use in service in the wellbore. 
   Referring to  FIG. 13 , another embodiment of the tool  10  and hinge mechanism is shown. In this embodiment a first stationary spring holder  130 , fixes the spring&#39;s first end  124  to the tool housing  1 . The stationary spring holder  130  comprises a body  131  having a bore  132   b . A cylindrical retaining pin  133   b  partially extends into the bore  132   b  and partially extends into the cavity of the jaw&#39;s tubular conduit  120  of the jaw  105 . The body  131  further comprises two counter-sunk screw holes  135   b  for attaching the stationary holder  130  to the housing  1 , using suitable fasteners  136 . A spring-retaining slot  134  is formed in the retaining pin  133   b  for engaging the hinge spring&#39;s first end  124 . The retaining pin  133   b  is locked to the holder  130  by means of a locking pin  137  passing through a hole  138  in the body  131  which then engages a recess  133   c  in the retaining pin  133   b . The orientation of the slot  134  relative to the pin  133   b  is such that when the pin  133   b  is affixed to the housing  1 , via the holder  130 , the jaw  105  is biased to the outwardly extending position. 
   A second rotating spring holder  140  is shown, which fixes the spring  121  to the jaw  105 . The rotating holder  140  comprises a body  141  having a bore (not visible). A cylindrical retaining pin  145   b  partially extends into the bore of the body  141 , for free rotation therein, and partially extends into the cavity of the jaw&#39;s tubular conduit  120  of the jaw  105 . The body  141  further comprises two counter-sunk screw holes  149   b  for attachment of the holder  140  to the housing  1 , using suitable fasteners  136 . A spring-retaining slot  144  is formed in the retaining pin  145   b  for engaging the hinge spring&#39;s second end  125 . The retaining pin  145   b  is locked to the jaw  105  by means of a locking pin  137  passing through a hole (not shown) in the jaw  105  and then engaging a recess (not shown) in the retaining pin  145   b . Accordingly, rotation of the spring&#39;s second end  125 , as the jaw  105  is compressed, twists the spring  121  into torsion. As soon as the force causing the jaw  105  to pivot to the compressed position is released, the spring  121  biases the jaw  105  to return the jaw  105  to the casing-engaging position once again.

Summary:
A tool is provided for preventing the rotation of a downhole tool or rotary pump stator, the tool comprising a tubular housing and a jaw which is biased radially outwardly from the tool to engage the casing wall for arresting tool rotation and providing significant stabilization of a rotary pump. In doing so, the tool housing moves oppositely to rest against the casing opposite the jaw. The tool housing and the downhole tool are thereby restrained and stabilized by the casing wall. The tool&#39;s jaw is released by opposite tool rotation. Preferably, the jaw is biased outwardly from the tool housing to a casing-engaging position by a torsional member, housed along the axis of the hinge of the jaw. The tool is released from the casing by opposite tool rotation which increasingly compresses the jaw toward the housing, twisting the torsional member into torsion, which then acts to urge the jaw outwardly again. Overextension of the jaw during assembly is prevented using cooperating stops in the jaw and the housing.