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CROSS REFERENCE TO RELATED APPLICATION 
     This application claims priority to U.S. Provisional Patent Application No. 61/745,755, filed Dec. 12, 2012 entitled Liner Hanger. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of Invention 
     The present invention relates to hydrocarbon well construction in general and in particular method and apparatus for removably setting a liner hanger within a well bore. 
     2. Description of Related Art 
     In hydrocarbon production, many wells include a main vertical bore and one or more horizontal bores extending therefrom. During preparation for production, liners are frequently located within each horizontal bore having valves and other associated production components therein. Such liners are commonly suspended from the vertical bore by liner hangers. 
     Conventionally, liner hangers are adapted to frictionally or otherwise engage the vertical bore or liner with one or more gripping element. One current difficulty with conventional liner hangers is that they are commonly set in place and are not thereafter able to be readily removed. 
     SUMMARY OF THE INVENTION 
     According to a first embodiment of the present invention there is disclosed an apparatus for suspending a liner within a bore comprising a central tubular member and first and second sets of radially expandable arms. Each set of arms are expandable by corresponding longitudinally movable cones spaced apart along the tubular member. The apparatus further includes a seal located between the first and second sets of radially expandable arms and a selectably longitudinally compressible sleeve located between the first and second sets of radially expandable arms. 
     The first and second cones may be selectably secured to the tubular member. The first and second cones may be selectably secured to the tubular member by shear pins. 
     Each of the first and second sets of radially expandable arms may extend from a common ring at proximate ends thereof. Each of the first and second sets of radially expandable arms may be expanded by pressing the corresponding cones under distal ends of the arms. Each of the first and second radially expandable arms may include a bracing sleeve extending from the proximate end of the arms and having a distal end adapted to engage the corresponding cone so as to prevent overexpansion of the arms. 
     The compressible sleeve may comprise a plurality of arms having end surfaces selectably engageable with a corresponding receptacle sleeve. The plurality of arms may extend longitudinally from a ring extending around the tubular member. The arms may extend towards the second set of radially expandable arms. The receptacle sleeve may extend from a location proximate to the second set of radially expandable arms. The receptacle sleeve may extend between first and second ends wherein the first end overlies end surfaces of the arms and wherein the second end is proximate to the cone corresponding to the second set of radially expandable arms. 
     The end surfaces of the arms may include teeth engageable with corresponding grooves in the sleeve. The end surfaces of the arms may be maintained in engagement with the sleeve by the central tubular member. The central tubular member may include a recess at a position therealong corresponding to a position at which the arms are desired to be released from engagement with the sleeve. 
     The seal may comprise a tubular seal element extending between first and second ends located around the central tubular member. The seal element may include end walls located around the first and second ends thereof. The end walls may overlap a portion of the seal element. 
     The first set of radially expandable arms may be slidable along the central tubular member from an initial position towards the second set of radially expandable arms. The second set of radially expandable arms may be secured to the central tubular member. 
     Other aspects and features of the present invention will become apparent to those ordinarily skilled in the art upon review of the following description of specific embodiments of the invention in conjunction with the accompanying figures. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In drawings which illustrate embodiments of the invention wherein similar characters of reference denote corresponding parts in each view, 
         FIG. 1  is a cross-sectional view of a wellbore having a liner hanger according to a first embodiment of the present invention located therealong. 
         FIG. 2  is a perspective view of the liner hanger of  FIG. 1 . 
         FIG. 3  is a longitudinal cross-sectional view of the liner hanger of  FIG. 2  as taken along the line  3 - 3  in a first or retracted position. 
         FIG. 4  is a detailed cross-sectional view of the first bore engaging arms of the liner hanger of  FIG. 2  at a retracted position. 
         FIG. 5  is a detailed cross-sectional view of the first bore engaging arms of the liner hanger of  FIG. 2  at an extended position. 
         FIG. 6  is a detailed cross-sectional view of the sealing element of the liner hanger of  FIG. 2  at a retracted position. 
         FIG. 7  is a detailed cross-sectional view of the sealing element of the liner hanger of  FIG. 2  at an extended position. 
         FIG. 8  is a detailed cross-sectional view of the second bore engaging arms of the liner hanger of  FIG. 2  at a retracted position. 
         FIG. 9  is a detailed cross-sectional view of the second bore engaging arms of the liner hanger of  FIG. 2  at an extended position. 
         FIG. 10  is a detailed cross-sectional view of the compressible section of the liner hanger of  FIG. 2  at an extended position. 
         FIG. 11  is a detailed cross-sectional view of compressible section of the liner hanger of  FIG. 2  at a compressed position. 
     
    
    
     DETAILED DESCRIPTION 
     Referring to  FIG. 1 , a wellbore  10  is drilled into the ground  8  to a production zone  6  by known methods. The production zone  6  may contain a horizontally extending hydrocarbon bearing rock formation or may span a plurality of hydrocarbon bearing rock formations such that the wellbore  10  has a path designed to cross or intersect each formation. As illustrated in  FIG. 1 , the wellbore includes a vertical section  12  having a valve assembly or Christmas tree  14  at a top end thereof and a bottom or production section  16  which may be horizontal or angularly oriented relative to the horizontal located within the production zone  6 . After the wellbore  10  is drilled the liner  18  is suspended therein from a liner hanger  20 . 
     With reference to  FIGS. 2 and 3 , a liner hanger according to a first embodiment of the present invention is illustrated generally at  20 . The liner hanger  20  extends between first and second ends,  22  and  24 , respectively, and is formed around a central tubular member  26 . The tubular member  26  includes the second end  24  which is operable to have a liner  18  connected thereto according to known methods such as threading and the like. As illustrated the liner hanger  20  includes first and second collets,  40  and  70 , respectively and a seal  110  therebetween. 
     The tubular member  26  may include a first end  28  having a threaded or other known end connector for connection to a production tubing, tool string or the like (not shown). The first end  22  of the liner hanger  20  also includes a setting sleeve  30  located therearound. The setting sleeve  30  is longitudinally slidable along the tubular member  26  such that the tubular member may be drawn in an upward direction towards the first end  22  of the liner hanger relative to the setting sleeve as will be more fully described below. The setting sleeve  30  extends between a threaded first end  32  for connection to a setting tool or the like, and an enlarged portion  36  at a second end thereof. Optionally, the setting sleeve  30  may also include separate hammer sleeve  34  threadably secured thereto which has an enlarged surface for engaging and extending the first bore engaging collets  40  as will be more fully described below. 
     Turning now to  FIG. 4 , a detailed cross sectional view of the first collet  40  is illustrated. The first collet  40  comprises a common ring  42  having a plurality of longitudinally extending arms  44  extending therefrom in a direction generally towards the second end  24  of the liner hanger. The arms  44  have distal ends  46  having outwardly oriented bore engaging surfaces  48  as are commonly known and a bottom angled surface  49 . As illustrated, the arms  44  extend substantially parallel to the tubular member and are separated from each other by slots  47  as illustrated in  FIG. 2 . The first collet  40  may also include a longitudinally compressible spring  52  located between the common ring  42  and the hammer sleeve  34  so as to prevent premature expansion of the arms  44  during run in and the like. The first collet  40  includes a first cone  54  associated therewith comprising a tubular body selectably secured to the tubular member with at least one shear pin  60 . The first cone  54  includes an angled trailing surface  56  corresponding to the bottom surface  49  of the arms and ending at a trailing edge  58 . The arms  44  may further secured to the first cone  54  by shear pins  45  so as to prevent extension of the arms during run in and the like. 
     The first collet  40  further includes a first bracing sleeve  62  located between the arms  44  and the tubular member  26 . The first bracing sleeve  62  comprises a substantially tubular body extending between first and second ends  64  and  66 , respectively and includes an enlarged portion having an upright surface  68  and a retracting surface  69  oriented towards the first end therealong. The first bracing may be threadably or otherwise secured to the hammer sleeve  34  so as to move longitudinally therewith. As illustrated in  FIG. 5 , as the tubular member  26  is drawn towards the first end  22  of the liner hanger, the first cone  54  is drawn into the first collet  40  so as to bear the angle surface  56  of the first cone against the angle bottom surface  49  of the arms  44  thereby biasing the arms  44  in a radially outward direction. Upon being extended by a predetermined distance, the trailing edge  58  of the first cone  54  will engage upon the second end  66  of the first bracing sleeve thereby preventing any further movement of the first cone relative to the arms  44  and thereby transferring any additional force exerted on the first cone  54  to the bracing sleeve  62 . It will be appreciated therefore that the bracing sleeve  62  will prevent any of such excess force from bending or otherwise damaging the arms  44 . At a predetermined activation pressure, the shear pins  60  are sheared thereby permitting the first cone  54  to remain fixed relative to the first collet  40  while the tubular member  26  is drawn therepast. In operation, the pressure at which the shear pins  60  are sheared may be selected to be any pressure, although it has been found that a force of between 5,000 and 30,000 pounds force has been useful. 
     Turning now to  FIGS. 8 and 9 , a detailed cross sectional view of the second collet  70  is illustrated. The second end  24  of the liner hanger  20  includes a shear sleeve  90  extending therearound which is selectably secured to the tubular member by at least one shear pin  92 . The shear sleeve provides an end stop for the second collet and transmits movement of the tubular member  26  to the second collet  70 . The second collet  70  comprises a common ring  72  having a plurality of longitudinally extending arms  74  extending therefrom in a direction generally towards the first end  22  of the liner hanger. The arms  74  have distal ends  76  having outwardly oriented bore engaging surfaces  78  as are commonly known and an inner angled surface  79 . As illustrated, the arms  74  extend substantially parallel to the tubular member and are separated from each other by slots  77  as illustrated in  FIG. 2 . The second collet  70  may also include a longitudinally compressible spring  82  located between the common ring  72  and the shear sleeve  90  so as to prevent premature expansion of the arms  74  during run in and the like. The second collet  70  includes a second cone  84  associated therewith comprising a tubular body slidably located about the tubular body by a locating ring  94 . The second cone  84  includes an angled leading surface  86  corresponding to the bottom surface  79  of the arms and ending at a trailing edge  88 . The arms  74  may further secured to the second cone  84  by shear pins  83  so as to prevent extension of the arms during run in and the like. 
     The second collet  70  further includes a second bracing sleeve  96  located between the arms  74  and the tubular member  26 . The second bracing sleeve  96  comprises a substantially tubular body extending between first and second ends  98  and  100 , respectively and includes an enlarged portion having an upright surface  102  therealong. The second bracing sleeve  96  may be threadably or otherwise secured to the tubular member  26 , such as within a depression as illustrated so as to move longitudinally therewith. As illustrated in  FIG. 9 , as the tubular member  26  is drawn towards the first end  22  of the liner hanger, the second collet  70  is drawn into the second cone  84  so as to bear the angle surfaces  79  of the arms  74  against the angled leading surface  86  of the second cone  84  thereby biasing the arms  74  in a radially outward direction. Upon being extended by a predetermined distance, the first end  98  of the second bracing sleeve  96  will engage upon the leading edge  88  of the second cone  84  thereby preventing any further movement of the first cone relative to the arms  74  and thereby transferring any additional force exerted on the cone  84  to the bracing sleeve  96 . It will be appreciated therefore that the bracing sleeve  96  will prevent any of such excess force from bending or otherwise damaging the arms  74 . 
     With reference to  FIG. 6 , the seal  110  comprises a tubular sealing element  112  located around the tubular member  26  between first and second extrusion barriers,  114  and  116 , respectively. The seal  110  may be formed of any suitable compressible sealing element, such as, by way of non-limiting example GraphicBraid™ produced by MinSeal™ of Tuscon Ariz. The extrusion barriers  114  and  116  comprise upright walls having an annular wall portion,  115  and  117 , respectively located to overlay the sealing element  112 . 
     The seal  110  also includes first and second bearing rings,  118  and  120 , respectively having the sealing element  112  and extrusion barriers  114  and  116  therebetween as well as first and second compression springs  122  and  124 , respectively located outside thereof. A backing ring  126  is secured to the tubular member  26  with backing ring shear pins  128  as illustrated in  FIG. 10  and is located to an opposed side of the seal  110  from the first cone  54  which is operably connected to the second cone  84 , through the compression joint, as further described below and is longitudinally displaceable along the tubular member  26  with the second cone. 
     In operation, as the tubular member is drawn in a direction generally towards the first end  22  of the liner hanger, backing ring  126  is drawn in a direction generally towards the first end  22  by the backing ring shear pins  128 . In such movement, the first cone  54  is held stationary relative to the first collet  40  and setting sleeve  30  after the shear pins  60  have been sheared as set out above. During such movement, the backing ring  126  is moved towards the first cone  54  thereby compressing the first and second compression springs  122  and  124  and sealing element  112  as illustrated in  FIG. 7 . The extrusion barriers  114  and  116  will retain and guide the sealing element  112  to be extruded in a generally radially outward direction as illustrated. In such a manner, the tubular member  26  is drawn upwards relative to the setting sleeve  30  until the first and second collets  40  and  70  and sealing element  112  are engaged upon the inside of the bore thereby forming a secure sealed mounting location for liner located therebelow. 
     With reference to  FIGS. 10 and 11 , a compressible section  130  may be located between the seal  110  and the second collet  70 . The compressible section permits the distance between the seal  110  and the second collet  70  to be selectably reduced when the liner hanger is desired to be removed. The compressible section comprises a plurality of compression arms  132  extending substantially longitudinally from the backing ring  126  in a direction generally towards the second end  24  of the liner hanger. Each arm includes a plurality of teeth or grips  134  at a distal end thereof oriented radially outward. 
     The compressible section further includes a receptacle sleeve  140  between the arms  132  and the second cone  84 . The receptacle sleeve  140  extends between first and second ends  142  and  144 , respectively and includes a plurality of grooves  146  on an inner surface of the first end  142  corresponding to the teeth  134  at the end of the arms  132 . The second end  144  of the receptacle sleeve  144  is secured to the second cone by threading or the like. In the first or operating position as illustrated in  FIG. 10 , the grooves  146  of the receptacle sleeve  140  are engaged with the teeth  134  of the arms so as to fix the relative positions therebetween. The arms are retained in a position so as to lock the teeth  134  therein by the tubular member  26  bearing against the bottom surface thereof. As illustrated in  FIGS. 10 and 11 , the tubular member  26  includes an annular groove  150  or release depression which is located below the teeth  134  to permit disengagement of the teeth  134  and grooves  146 . 
     In operation, the liner hanger may be located at the top end of a liner and placed within a well bore. In such a position, the first cone  54 , backing ring  126  and shear sleeve  90  are fixed relative to the tubular member by shear pins  60 ,  128  and  92 , respectively. When the liner hanger  20  is actuated, the setting sleeve is pressed towards the second end relative to the tubular member  26  until the first cone  54  is engaged upon the first bracing sleeve  62  thereby searing the first shear pins  60  and engaging first collet. As the setting sleeve  30  member is pressed towards the second end  24 , the sealing element  112  is compressed between the backing ring  126  and the first cone  54  until it is sufficiently in engagement upon the well bore wall at which pressure the second shear pins  128  are severed thereby sealing against well bore. The pressure for the second shear pins to be severed may be selected to be any pressure above the pressure to sever the first shear pins, however in practice it has been found that a force of between 5000 and 30,000 pounds force has been useful. Further movement of the setting sleeve  30  thereafter presses the second collet  70  onto the second cone  84  so as to extend the second arms  74  thereby fixing the bottom collet within the well bore. 
     When a user wishes to remove the liner hanger, a further force is applied to the tubular member  26  in a direction towards the first end  22  sufficient to shear the third shear pins  92  thereby releasing the shear sleeve  90  from the tubular member. The third shear pressure should be selected to be higher than the first and second shear pressures, and in practice it has been found that a pressure of between 5000 and 30,000 pounds force has been useful. To release the second collet from the well bore wall, the tubular member is further translated relative to the second collet  70  until the tubular member  26  is located relative to the setting sleeve  30  such that the release depression  150  below the teeth  134  and grooves  146  of the compression section thereby permitting radially inward movement of the teeth  134  of the arms  132  thereby disengaging the teeth  134  from the grooves  146  whereupon the retaining sleeve is permitted to move longitudinally towards the first end  22 . Thereafter, the locating ring  94 , which is located within an annular groove in the tubular member engages upon receptacle sleeve  140  or a portion of the second cone  84  whereafter the locating ring will pull the second cone  84  in a direction towards the first end  22  thereby disengaging the bore engaging surfaces  78  of the second collet  70  from the bore wall. After being disengaged, the second collet  70  will be freely movable relative to the well bore wall and may therefore fall down the well bore or along the liner for collection. Furthermore, it will be appreciated that once the collapsible section is collapsed as described above and illustrated in  FIG. 11 , the sealing element will no longer be compressed and will therefore be permitted to return to the retracted position illustrated in  FIG. 6  and the first cone  54  will be permitted to slide towards the second end thereby permitting the first arms  44  to retract from the well bore side wall thereby disengaging the first collet  40 . After being retracted from the well bore side wall, the locating ring  94  will maintain the second cone  84  at a position away from the second collet  70  and the retracting surface  69  will engage the first collet  40  to maintain it at a position away from the first cone  54  so as to prevent subsequent re-engagement of the collets and thereby to facilitate extraction. 
     While specific embodiments of the invention have been described and illustrated, such embodiments should be considered illustrative of the invention only and not as limiting the invention as construed in accordance with the above description.

Summary:
An apparatus for suspending a liner within a bore comprising a central tubular member and first and second sets of radially expandable arms. Each set of arms are expandable by corresponding longitudinally movable cones spaced apart along the tubular member. The apparatus further includes a seal located between the first and second sets of radially expandable arms and a selectably longitudinally compressible sleeve located between the first and second sets of radially expandable arms.