Patent Publication Number: US-7896111-B2

Title: Gripping tool with driven screw grip activation

Description:
FIELD OF THE INVENTION 
     This invention relates generally to applications where tubulars and tubular strings must be gripped, handled and hoisted with a tool connected to a drive head or reaction frame to enable the transfer of both axial and torsional loads into or from the tubular segment being gripped. In the field of earth drilling, well construction and well servicing with drilling and service rigs this invention relates to slips, and more specifically, on rigs employing top drives, applies to a tubular running tool that attaches to the top drive for gripping the proximal segment of tubular strings being assembled into, deployed in or removed from the well bore. This tubular running tool supports various functions necessary or beneficial to these operations including rapid engagement and release, hoisting, pushing, rotating and flow of pressurized fluid into and out of the tubular string. 
     BACKGROUND 
     Until recently, power tongs were the established method used to run casing or tubing strings into or out of petroleum wells, in coordination with the drilling rig hoisting system. This power tong method allows such tubular strings, comprised of pipe segments or joints with mating threaded ends, to be relatively efficiently assembled by screwing together the mated threaded ends (make-up) to form threaded connections between sequential pipe segments as they are added to the string being installed in the well bore; or conversely removed and disassembled (break-out). But this power tong method does not simultaneously support other beneficial functions such as rotating, pushing or fluid filling, after a pipe segment is added to or removed from the string, and while the string is being lowered or raised in the well bore. Running tubulars with tongs also typically requires personnel deployment in relatively higher hazard locations such as on the rig floor or more significantly, above the rig floor, on the so called ‘stabbing boards’. 
     The advent of drilling rigs equipped with top drives has enabled a new method of running tubulars, and in particular casing, where the top drive is equipped with a so called ‘top drive tubular running tool’ or ‘top drive tubular running tool’ to grip and perhaps seal between the proximal pipe segment and top drive quill. (It should be understood here that the term top drive quill is generally meant to include such drive string components as may be attached thereto, the distal end thereof effectively acting as an extension of the quill.) Various devices to generally accomplish this purpose of ‘top drive casing running’ have therefore been developed. Using these devices in coordination with the top drive allows rotating, pushing and filling of the casing string with drilling fluid while running, thus removing the limitations associated with power tongs. Simultaneously, automation of the gripping mechanism combined with the inherent advantages of the top drive reduces the level of human involvement required with power tong running processes and thus improves safety. 
     In addition, to handle and run casing with such top drive tubular running tools, the string weight must be transferred from the top drive to a support device when the proximal or active pipe segments are being added or removed from the otherwise assembled string. This function is typically provided by an ‘annular wedge grip’ axial load activated gripping device that uses ‘slips’ or jaws placed in a hollow ‘slip bowl’ through which the casing is run, where the slip bowl has a frusto-conical bore with downward decreasing diameter and is supported in or on the rig floor. The slips then acting as annular wedges between the pipe segment at the proximal end of the string and the frusto-conical interior surface of the slip bowl, tractionally grip the pipe but slide or slip downward and thus radially inward on the interior surface of the slip bowl as string weight is transferred to the grip. The radial force between the slips and pipe body is thus axial load self-activated or ‘self-energized’, i.e., considering tractional capacity the dependent and string weight the independent variable, a positive feedback loop exists where the independent variable of string weight is positively fed back to control radial grip force which monotonically acts to control tractional capacity or resistance to sliding, the dependent variable. Similarly, make-up and break-out torque applied to the active pipe segment must also be reacted out of the proximal end of the assembled string. This function is typically provided by tongs which have grips that engage the proximal pipe segment and an arm attached by a link such as a chain or cable to the rig structure to prevent rotation and thereby react torque not otherwise reacted by the slips in the slip bowl. The grip force of such tongs is similarly typically self-activated or ‘self-energized’ by positive feed back from applied torque load. 
     In general terms, an embodiment of the “Gripping Tool” of WIPO Patent Application PCT/CA2006/000710 may be summarized as a gripping tool which includes a body assembly, having a load adaptor coupled for axial load transfer to the remainder of the body, or more briefly the main body, the load adaptor adapted to be structurally connected to one of a drive head or reaction frame, a gripping assembly carried by the main body and having a grip surface, which gripping assembly is provided with activating means to move from a retracted position to an engaged position to radially tractionally engage the grip surface with either an interior surface or exterior surface of a tubular work piece in response to relative axial movement or stroke of the main body in at least one direction, relative to the grip surface. A linkage is provided acting between the body assembly and the gripping assembly which, upon relative rotation in at least one direction of the load adaptor relative to the grip surface, results in relative axial displacement of the main body with respect to the gripping assembly to move the gripping assembly from the retracted to the engaged position in accordance with the action of the activating means. 
     This gripping tool thus utilizes a mechanically activated grip mechanism that generates its gripping force in response to axial load or stroke activation of the grip assembly, which activation occurs either together with or independently from, externally applied axial load and externally applied torsion load, in the form of applied right or left hand torque, which loads are carried across the tool from the load adaptor of the body assembly to the grip surface of the gripping assembly, in tractional engagement with the tubular work piece. 
     The grip surface of prior art gripping tools are generally comprised of a coarse profiled and hardened surface typical of tong dies known to the art, where such dies are designed to be sufficiently “sharp” so as to provide a consistent and reliable tractional engagement with the work piece for a gripping tool&#39;s grip ratio. Where grip ratio is defined as the normal force (radial load for tubulars) acting between the grip surface and the work piece divided by the magnitude of the shear force (arising from applied hoisting and torsional loads) and by definition must exceed the inverse of the effective coefficient of friction existing between the grip surface and the work piece to prevent slippage. “Sharper” dies, with less contact area, generally penetrate the work piece at lower normal forces providing a higher effective friction coefficient at the correlative lower hoisting load than “duller” dies but this has the side effect of causing greater indentation depth at greater loads leaving localized regions of plastic deformation on the surface of the work piece which are undesirable in certain applications. 
     As grip surfaces wear the die tooth tips become more rounded and the tooth tip area increases such that the effective coefficient of friction tends to decrease at the same normal stress. In addition, work pieces with hardened, inconsistent, or coated surfaces offer reduced coefficient and require a tool with a higher grip ratio or a more aggressive grip surface to safely run. Similarly a higher grip ratio is typically required at lower magnitudes of normal force. The present invention is directed to this need. 
     SUMMARY 
     In general terms the present invention is an improved gripping tool of the type generally described in PCT/CA2006/000710, with the improvement comprising the incorporation of one or more features to enhance the tool&#39;s grip ratio over some or all of the range of applied axial or torsional loads. 
     There is provided a gripping tool having at least one body, including an associated load adaptor adapted to be connected to and interact with one of a drive head or reaction frame. A gripping assembly is carried by the at least one body. The gripping assembly has at least one grip surface adapted to move from a retracted position to an engaged position to radially engage the grip surface with one of an interior surface or an exterior surface of a work piece upon relative axial displacement of the at least one body relative to the grip surface in at least one axial direction. A grip activation assembly acts between the at least one body and the grip surface and includes a motor driven load screw to create relative axial displacement of the at least one body relative to the grip surface and correlatively increases the grip ratio of radial engagement force of the grip surface relative to applied axial load. 
    
    
     
       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: 
       Externally Gripping (External Grip) Tubular Running Tool with Motor Driven Load Screw Activation 
         FIG. 1  is a partial cutaway trimetric view of a simplified version of a tubular running tool provided with an external bi-axially activated wedge-grip mechanism with a motor driven load screw activator in its base configuration architecture (latched position w/o casing) 
         FIG. 2  is a cross-section view of a simplified version of a tubular running tool shown in  FIG. 1  as it appears in its set position gripping the proximal end of a threaded and segment of casing 
       Internally Gripping (Internal Grip) Tubular Running Tools with Motor Driven Load Screw Activation 
         FIG. 3  is a partial cutaway trimetric view of a tubular running tool provided with an internal bi-axially activated wedge-grip mechanism with a motor driven load screw activator in its base configuration architecture (latched position w/o casing). 
         FIG. 4  is a cross-section view of an internal grip tubular running tool shown in  FIG. 3  as it appears set on the proximal end of a threaded and coupled segment of casing. 
         FIG. 5  is a partial cutaway trimetric view of a tubular running tool provided with an internal bi-axially activated helical wedge-grip mechanism with a motor driven load screw activator in its base configuration architecture (latched position w/o casing). 
         FIG. 6  is a cross-section view of an internal grip tubular running tool shown in  FIG. 5  as it appears set on the proximal end of a threaded and coupled segment of casing. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     General Principles 
     The gripping tool described in PCT patent application CA 2006/00710,is comprised of three main interacting components or assemblies: 1) a body assembly, 2) a gripping assembly carried by the body assembly, and 3) a linkage acting between the body assembly and gripping assembly. The body assembly generally provides structural association of the tool components and includes a load adaptor by which load from a drive head or reaction frame is transferred into or out of the remainder of the body assembly or the main body. The gripping assembly, has a grip surface, is carried by the main body of the body assembly and is provided with means to radially stroke or move the grip surface from a retracted to an engaged position in response to relative axial movement, or axial stroke, to radially and tractionally engage the grip surface with a work piece. The gripping assembly thus acts as an axial load or axial stroke activated grip element. 
     The main body is coaxially positioned with respect to the work piece to form an annular space in which the axial stroke activated gripping assembly is placed and connected to the main body. The grip surface of the gripping assembly is adapted for conformable, circumferentially distributed and collectively opposed, tractional engagement with the work piece. The means to radially stroke the gripping surface carried by the gripping assembly is configured to link relative axial displacement, or axial stroke, in at least one axial direction, into radial displacement or radial stroke of the grip surface against the work piece with correlative axial and collectively opposed radial forces then arising such that the radial grip force at the grip surface enables reaction of applied axial load and torque into the work piece, where the distributed radial grip force is internally reacted, which arrangement comprises an axial load activated grip mechanism where axial load is carried between the drive head or reaction frame and work piece; the load adaptor, main body and grip element, generally acting in series. 
     The linkage acting between the body assembly and gripping assembly is adapted to link relative rotation between the load adaptor and grip surface into axial stroke of the gripping assembly and hence radial stroke of the grip surface. The axial load activated grip mechanism is thus arranged to allow relative rotation between one or both of axial load carrying interfaces between the load adaptor and main body or main body and grip element which relative rotation is limited by at least one rotationally activated linkage mechanism which links relative rotation between the load adaptor and grip surface into axial stroke of the grip element and hence radial stroke of the grip surface. The linkage mechanism or mechanisms may be configured to provide this relationship between rotation and axial stroke in numerous ways such as with pivoting linkage arms or rocker bodies acting between the body assembly and gripping assembly but can also be provided in the form of cam pairs acting between the grip element and at least one of the main body or load transfer adaptor to thus readily accommodate and transmit the axial and torsional loads causing, or tending to cause, rotation and to promote the development of the radial grip force. The cam pairs, acting generally in the manner of a cam and cam follower, having contact surfaces are arranged in the preferred embodiment to link their combined relative rotation, in at least one direction, into axial stroke of the grip element in a direction tending to tighten the grip, which axial stroke thus has the same effect as and acts in combination with axial stroke induced by axial load carried by the grip element. Application of relative rotation between the drive head or reaction frame and grip surface in contact with the work piece, in at least one direction, thus causes radial stroke or radial displacement of the grip surface into engagement with the work piece with correlative axial, torque and radial forces then arising such that the radial grip force at the grip surface enables reaction of torque into the work piece, which arrangement comprises torsional load activation so that together with the said axial load activation, the grip mechanism is self-activated in response to bi-axial combined loading in at least one axial and at least one tangential or torsional direction. 
     In one embodiment of the present invention the axial load activated grip mechanism of the improved gripping tool is further arranged to allow for a motor driven load screw to induce a relative axial movement between the main body of the body assembly and the grip assembly. This motor driven load screw assembly generally consists of, but is not limited to, a motor, a driven gear, and a load screw pair. This motor driven load screw assembly can be configured to provide relative axial displacement between the grip assembly and the main body in numerous ways, but is generally configured such the motor is rigidly attached to the main body and the driven gear is allowed to rotate relative to the main body but is fixed axially while one half of the load screw pair is fixed to the drive gear the other is fixed to one of the cams and allowed to move axially relative to the main body but is configured such that it is rotationally fixed to the main body. The result is that activation of the motor drives the grip assembly axially relative to the main body and thus induces radial displacement of the grip surface, moving it into contact with the work piece. This motor driven load screw mechanism is configured such that the axial load and torque activated gripping mechanisms remain active. The drive motors of the present invention are illustrated to be hydraulic motors and as such require hydraulic fluid supplied at pressure through a rotating seal assembly which is not illustrated, it is expected that the rotary seal assembly will be of standard commercially available design and is mounted to the motor mount as convenient for a given embodiment. (It is understood that it may be desirable to use drive motor of a different type and as such accommodations for supply of power to the motors through the rotating interface must be made regardless of power type.) 
     In brief, a stroke or axial force activated grip mechanism, where the axial component of stroke causes radial movement of the grip surface into tractional engagement with the work piece, provides a work piece gripping force correlative with axial force, which tractionally resists shear displacement or sliding between the work piece and the gripping surface. The tool provides a further rotation or torque activated linkage acting to stroke the grip surface in response to relative rotation induced by torque load carried across and reacted within the tool in at least one rotational direction, which rotation or torque induced stroke is arranged to have an axial component that causes the radial movement of the grip surface with correlative tractional engagement of the work piece and gripping force internally reacted between the work piece and grip mechanism structure. 
     The present invention provides an additional means to stroke the grip surface relative to the main body of the tool using a motor driven load screw. Activation of the motor causes an axial load to be applied to the grip assembly, which is reacted within the main body, and results in a relative axial movement of the grip assembly relative to the main body resulting in a radial movement of the grip surface with correlative tractional engagement of the work piece. 
     All of the embodiments of improved gripping tools subsequently described are defined by a single configuration architecture, where the term configuration architecture refers to the arrangement of the cams. It is understood that any of the improvements of the present invention can be applied to a gripping tool with any of the seven (7) cam architectures described in detail in PCT/CA2006/000710, now in the US national phase under U.S. patent application Ser. No. 11/912,656, filed Oct. 25, 2007. 
     External Grip Tubular Running Tool with Motor Driven Load Screw Activation 
     Referring to  FIGS. 1 and 2 , there will now be described a preferred embodiment, of gripping tool, referred to here as an “external grip tubular running tool with motor driven load screw activation”. Shown in a simplified form this external tubular running tool with motor driven load screw activation has its grip element provided as a wedge-grip and is incorporated into a mechanically set and unset tubular running tool, embodying the flat-cam configuration (4) torque activation architecture. This ‘flat-cam configuration (4) wedge-grip’ bi-axially activated tubular running tool with load screw activation is shown in  FIG. 1 , generally designated by the numeral  100 , where it is shown in an trimetric partial cut-away view as it appears configured to grip on the external surface of a tubular work piece, hence this configuration is subsequently referred to as an external grip tubular running tool. Referring now to  FIG. 2 , this external grip tubular running tool  100  of the preferred embodiment is shown in relation to tubular work piece  101  as it is configured for running casing strings comprised of casing joints or pipe segments joined by threaded connections arranged to have a ‘box up pin down’ field presentation, where the most common type of connection is referred to as threaded and coupled. Work piece  101  is thus shown as the upper end of a piece of casing having a pipe body  102  with exterior surface  103  and upper end  104 . It is understood that generally the work piece  101  will consist of mill end connection, including a coupling which is preassembled to the threaded proximal end of a joint of casing, but for illustration purposes this simplified version of the external grip tubular running is shown engaging a piece of casing with no end connection style indicated. It will be apparent to one skilled in the art that the tool can be modified by increasing the internal dimensions radially and/or axially as required to accommodated any desired coupling style. The presence of a coupling on the upper end of the work piece is not an essential requirement for the functioning of this embodiment of the present invention as a tubular running tool. 
     Referring still to  FIG. 2 , tubular running tool  100  is shown in its activated position, as it appears when engaged with and gripping tubular work piece  101  and configured at its upper end  110  for connection to a top drive quill, or the distal end of such drive string components as may be attached thereto, (not shown) by load adaptor  120 . Load adaptor  120  connects a top drive to an external bi-axially activated gripping element assembly  111  having at its lower end  112  an interior opening  113  where the external gripping interface is located and into which interior opening  113  the upper the proximal end  104  of a tubular work piece  101  is inserted and coaxially located. Load adaptor  120  is generally axi-symmetric and made from a suitably strong material. It has an upper end  121  configured with internal threads  122  suitable for sealing connection to a top drive quill, with internal through bore  123 . 
     Referring still to  FIG. 2 , main body  130  is generally cylindrical in shape and comprised of upper end  131  and lower end  132  with internal frusto-conical surface  133 . Main body  130  is rigidly connected to the motor drive assembly  140  at upper end  131 . The motor drive assembly  140  is comprised of a motor mount flange  141 , a plurality of drive motors  142  and pinion gears  143  (in this case two), and ring gear  144 . The pinion gears  143  are rigidly connected to the drive motors  142 , which are mounted to the motor mount flange  141 . Ring gear  144  meshingly engages with pinion gears  143  and slidingly engages with motor mount flange  141  to prevent relative axial movement. A thread cam  150  is provided that has internal surface  151 , external surface  152  and bottom cam face  153 . The external surface  152  of thread cam has a plurality of axially oriented splines  155  which slidingly engage with mating axial splines  135  on the internal surface  134  of main body  130 , forming guide spline pair  156 . Load screw  145  on ring gear  144  threadingly engages with load screw  154  on the inside surface  151  gear cam  150 . Dual cam  160  with upper cam face  161  and lower cam face  162  is rigidly attached to the lower end  124  load adaptor  120 . The bottom cam face  153  of thread cam  150  slidingly engages the upper cam face  161  of dual cam  160 , and collectively form the upper cam pair  163 . A cage  170  is provided with upper end  171 , lower end  172 . A plurality of radially oriented windows  173 , in this case five (5), are provided in the bottom end  172  of cage  170 . Upper end  171  of cage  170  is provided with cam profile  174 . The lower cam face  162  of dual cam  160  slidingly engages with cam profile  174  on the upper end  171  of cage  170  and collectively form the lower cam pair  164 . In this case the cam pairs  163  and  164  are shown in the flat-cam configuration arrangement with a simple saw tooth cam profile. The present invention is provided with a plurality of jaws  180 , in this case five (5), with outer frusto-conical segment surface  181 , inner cylindrical surface  182 , upper end  183  and lower end  184 . The jaws  180  are assembled in windows  173  of cage  170  such that the outer surface  181  slidingly engages with inner frusto-conical surface  133  of main body  130 . The inner substantially cylindrical surface  182  of jaw  180 , with a coarse profiled and hardened surface finish typical of tong dies, designed to increase friction and improve wear characteristics, the inner surfaces  182  of jaws  180  collectively form the gripping surface  183  which tractionally engages outer surface  103  of work piece  101 . While the gripping surface  183  in this case is shown to be integral with the jaws  180  to form a so-called jaw-die, it is understood that it may be desirable to have a separate “die” component which is rigidly attached to the inner cylindrical surface of the jaw  180  and in either case the grip element assembly  111  tractionally engages the exterior surface  103  of work piece  101 . The external tubular running tool with motor driven load screw activation  100  is designed such that activation of drive motors  142  will result in the axial movement of thread cam  150  relative to main body  130  along guide spline pair  156 . Driving thread cam  150  axially downwards relative to main body  130  will bring upper cam pair  163  and lower cam pair  164  together and subsequently push cage  170  downward relative to main body  130 . The jaws  180 , which are axially constrained within the windows  173  of cage  170  move down the internal frusto-conical surface  133  of main body  130  consequently move radially inwards until inner surface  182  makes contact with and tractionally engages outer surface  103  of work piece  101 . Driving thread cam  150  axially upwards will allow the dies to become disengaged from the casing. It is understood that the preferred embodiment of the present invention is not limited to the cam profiles illustrated and that other cam profiles or arrangements can used in this embodiment the tool. It will be understood by one skilled in the art that, while not shown in this simplified configuration, the jaws are required to be retracted on reversal of the drive motors. As such any one of an number of mechanical means can be used to retract the jaws which include but are not limited to keying the jaw to the frusto-conical internal surface of the main body or providing a radially acting spring attached to the jaws. 
     Internal Gripping Tubular Running Tool Incorporating an Axi-Symmetric Wedge Grip with Motor Driven Load Screw Activation 
     In an alternative embodiment, this ‘base configuration wedge-grip’ bi-axially activated tubular running tool with motor driven load screw activation is provided in an internally gripping configuration, as shown in  FIGS. 3 and 4 , and generally designated by the numeral  200 . Referring now to  FIG. 3  where the tool is shown in a trimetric partially sectioned view as it appears configured to grip on the internal surface of a tubular work piece, thus also referred to here as an internal grip tubular running tool. This alternate configuration shares most of the features of the external grip tubular running tool of the preferred embodiment already described; therefore it will be described here more briefly. 
     Referring now to  FIG. 4 , internal grip tubular running tool  200  is shown inserted into work piece  201  and engaged with its interior surface  202 ; having an elongate generally axi-symmetric mandrel  203 , which in this configuration functions as the main body. Mandrel  203  having an upper end  204 , in which load adaptor  205  is integrally formed, a lower end  206 , a centre through bore  207  and a generally cylindrical external surface  208  except where it is profiled to provide ramp surface  209  distributed over a plurality of individual frusto-conical intervals  210  here shown as four (4), and splined interval  211 . 
     Referring still to  FIG. 4 , a plurality of circumferentially distributed and collectively radially opposed jaws  220 , shown here as five (5), are disposed around ramp surface  209 ; jaws  220  have internal surfaces  221  profiled to generally mate to and slidingly engage with ramp surface  209 , and external surfaces  222 , typically provided with rigidly attached dies  223 ; dies  223  having external surfaces  224  collectively forming grip surface  225  configured with a shape and surface finish to mate with and provide effective tractional engagement with the interior surface  202  of work piece  201 , such as provided by the coarse profiled and hardened surface finish, typical of tong dies. Generally tubular cage  226 , having upper and lower ends  227  and  228  respectively, is coaxially located between the exterior surface  208  of mandrel  203  and interior surface  202  of work piece  201 . Referring now to  FIG. 3 , cage  226  having windows  229  in its lower end  228  in which the jaws  220  are placed and thus axially and tangentially aligned, the assembly of jaws  220  and cage  226  forming wedge-grip element  230 . The cage  226  together with jaws  220  collectively form the grip assembly. 
     Jaws  220  can also be retained where the jaws having upper and lower ends  270  and  271  respectively are provided with retention tabs  272  extending upward on their upper ends  270 , and referring now to  FIG. 4 , where the retention tabs  272  are arranged to engage the inside of cage  226  when the jaws  220  are installed in windows  229  and are positioned at their intended limit of radial extension; and at their lower ends  271  to be similarly retained by retainer ring  273  attached to and carried on the lower end  228  of cage  226  overlapping with lower ends  271  of jaws  220 . As a further means to urge retraction of the jaws, split ring  274  is provided attached to mandrel  203  above ramp surface  209  and trapped inside cage  226  and arranged so that when relative downward axial movement of the mandrel  203  required to retract the jaws  220  occurs, retention tabs  272  slide under split ring  274  tending to force jaws  220  inward. 
     Referring still to  FIG. 4 , upper end  227  of cage  226  is rigidly attached to generally tubular cage cam  240  having upward facing profiled end surface  241 . Thread cam  242  is similarly tubular with downward facing profiled end surface  243  generally interacting with the upward facing profiled surface  241  of cage cam  240  to act as a cam pair  244  providing torque activation. Thread cam  242  has load thread  245  on the outer surface  247  at the generally tubular upper end  246  and axially oriented guide splines  249  on inner surface  248 . The axially oriented guide splines  249  of thread cam  242  are designed such that they mesh with and are assembled such that they slidingly engage with guide spline interval  211  near the center of the external surface  208  of mandrel  203 . Cam pair  244  has external latch housing  250  which is generally tubular in shape and rigidly attached to the outside surface  247  of thread cam  242 , the lower end  251  of external latch housing  250  slidingly engages the outside surface  251  of cage cam  240  and provides a positive axial stop such that upward facing internal upset surface  252  of external latch housing  250  engages with the downward facing external upset surface  253  on cage cam  240  so that the axial separation of cam pair  244  is limited. While external latch housing  250  is illustrated in this case to function solely as a axial stop/latch, it is understood that it may be desirable to have an air spring acting between the cam faces of cam pair  244 , and as such the external latch housing  250  can be adapted to provide an air reservoir and to sealingly and slidingly engage with cage cam  240 . As such air pressure in this reservoir will act to provide some initial die engagement and improve the grip ratio of the tool at low hoisting loads. 
     Referring still to  FIG. 4 , drive screw  260  with upper end  261 , lower end  262  and internal surface  263 , is assembled coaxially with mandrel  203  and located above cam pair  244 . Lower end  262  of drive screw  260  has thread element  264  on internal surface  263 , which threadingly engages with load thread  245  on the outer surface  247  of thread cam  242 . The upper end  261  of drive screw  260  is rigidly attached to ring gear  270 , which has upper end  271 , lower end  272  and internal geared surface  273 . The tubular running tool of the present invention is provided with motor mount  280  that has upper end  281 , lower end  282 , internal surface  283  and external flange  284  with a plurality of mounting holes  285 , in this case five (5). The motor mount  280  is assembled coaxially with mandrel  203  above drive screw  260  and the internal surface  283  is rigidly attached to the external surface  208  of mandrel  203 . A plurality of drive motors  290  and pinion gears  291  are provided, in this case five (5). The drive motors  290  are rigidly attached to mounting holes  285  on the external flange  284  of motor mount  280 . Pinion gear  290  is rigidly attached to and coaxially mounted to the motor shaft  292  of drive motor  290 , and has gear teeth  293  on external surface  294  which meshingly engage with gear teeth on the internal surface  273  of ring gear  270 . Bump ring  300  is attached to the upper end  227  of cage  226  and is dimensioned to act as a land or stop for the proximal end  216  of work piece  201 . The lower end  206  of mandrel  203  is provided with an annular seal  215 , shown here as a packer cup, sealingly engaging with the internal surface  202  of work piece  201 , thus providing a sealed fluid conduit from the top drive quill through bore  207  of mandrel  203  into the work piece  201 , to support filling and pressure containment of well fluids during casing running or other operations. In addition, flow control valves such as a check valve, pressure relief valve or so called mud-saver valve (not shown), may be provided to act along or in communication with this sealed fluid conduit. 
     Thus configured, interior gripping tubular running tool  200 , functions in a manner very similar to that already described in the preferred embodiment of exterior gripping tubular running tool  100 , where it is unlatched and set by forward activation of the drive motors and latched by reverse activation of the drive motors. Once set the tool activates in a fully mechanical manner with biaxial activation, referring still to  FIG. 4 , the tool is shown as it would appear under application of right hand torque causing rotation and activation of the cam pair  244 . 
     Internal Gripping CRT Incorporating Helical Wedge Grip with Motor Driven Load Screw Activation 
     In an alternative embodiment of the present invention, the bi-axially activated internally gripping tubular running tool with motor driven load screw activation is configured to have a helical wedge grip. This variant embodiment is illustrated in  FIGS. 5 and 6  as an internal gripping bi-axially activated tubular running tool employing a torque activation architecture single cam pair characterized and generally designated by the numeral  400 . Referring now to  FIG. 5  where the tool  400  is shown in a trimetric partially sectioned view as it appears retracted and configured to insert into a tubular work piece. This alternative configuration shares many of the features of the internally gripping axi-symmetric wedge grip tubular running tool with motor driven load screw activation of embodiment  200  previously described, therefore it will be described here with emphasis on the different architectural features. 
     Referring now to  FIG. 6 , which shows tubular running tool  400  as it would appear inserted into work piece  401  and engaged with its interior surface  402 ; having an elongate mandrel  403 , which in this configuration functions as the main body. Mandrel  403  made from a suitably strong and rigid material and having a centre through bore  404 , a lower end  405 , and having an interval above the lower end  405  of generally increasing diameter and comprised of dual ramp surface interval  406 , characterized by a helical profile  407  which tapers inward towards the lower end  405  of mandrel  403  and is generally shaped as a tapered thread form with lead, taper, helix direction, load flank angle and stab flank angle all selected in accordance with the needs of a given application, but shown here in the preferred embodiment as a right hand V-thread formed by load and stab flank surfaces  409  and  410  respectively together forming dual ramp surface  411 , where the load and stab flank angles or axial radial flank tapers are selected to be similar to those typically employed for the frusto-conical surfaces of slips. Above the dual ramp surface is a cage thread interval  412  in which are placed external carrier threads  413  having a lead matching that of helical profile  407 . Above the cage thread interval  412  is an axial splined interval  414 , and above that are the load thread element  416  with a lead also matching that of helical profile  407 . 
     Referring again to  FIG. 6 , tubular running tool  400  has mandrel carrier ring  420  with upper end  421  lower end  422 , internal bore  423  and external surface  424 . Load thread  425  at the lower end  422  of mandrel carrier ring  420  on the internal bore  423 , threadingly engages the load thread element  416  on upper end of mandrel  403 . Load shoulder  426  is located at the upper end  421  on the external surface  424  of mandrel carrier ring  420 . Upper nubbin  430  with upper end  431 , lower end  432  outer surface  433  and inner bore  434 , has splined interval  435  and threaded interval  436  on outer surface  433 , stinger  437  at lower end  432  and load adaptor  438  at upper end  431  which is designed to threadingly and sealingly engage with the top drive quill. Referring now to  FIG. 5 , upper cam ring  440  with upper end  441 , lower end  442 , has interior shoulder  443 , interior threaded interval  444  and torque dogs  445  at upper end  441 . The lower face  442  of upper cam ring  440  consists of cam profile  446 , which in this case is shown to be a symmetric saw tooth profile, although it is understood that it may be desirable to use a different profile. The interior shoulder  443  of upper cam ring  440  is assembled such that it contacts and slidingly engages downward facing shoulder  426  of mandrel carrier ring  420  and as such completes the primary hoisting load path between the load adaptor  438  on upper nubbin  430  and the grip element  475  on jaws  470 . 
     Referring still to  FIG. 5 , tubular running tool  400  is provided with lower cam ring  450  with cam profile  451  at upper end  452  and is rigidly connect to, in this case integrally formed with, motor mount flange  453  at lower end  454 . Lower cam ring  450  is assembled coaxially with and adjacent to upper cam ring  440  such that cam profiles  451  and  446  respectively slidingly engage one another collectively forming cam pair  457 . Cage  460  with is rigidly connect to, in this case integral with, gear housing flange  461  at upper end  462 , is generally tubular in shape with elongate lower interval  463 , carrier thread element  466  and a plurality of radially oriented windows  464 , in this case five (5), which are evenly spaced around the circumference. The upper end  462  of cage  460  is rigidly connected to motor mount flange  453  of lower cam ring  450  collectively forming a gear housing cavity  465 . A plurality of drive motors  480 , in this case two (2) are located on and rigidly attached to the upper face  455  of motor mount flange  453 , such that the drive shaft  481  of motor  480  passes through the motor mount flange and is rigidly connected to pinion gear  482  in gear housing cavity  465 . Drive gear  490  with outside surface  491  and inside surface  492 , has guide splines  493  on inside surface  492 , which slidingly engage with and restrict relative circumferential displacement relative to splined interval  414  on mandrel  403 . Outside geared surface  491  meshingly engages with pinion gear  482 . Drive gear  490  is assembled such that upper surface  494  and lower surface  495  engage respectively with thrust bearing elements  496  and  497  and react axial load to hold the drive gear  490  axially stationary relative to the cage  460 . A plurality of jaws  470 , equal to the number of windows  464  in cage  460 , in this case five (5), with an interrupted tapered helical profile  471  on inner surface  472  designed to mate with tapered helical profile  407  of mandrel  403 , has grip surface  473  on outer surface  474 . In this case grip=surface  473  is shown to be integral to the jaw  470  and collectively form grip element  475 . The jaws  470  and cage  460  collectively form the grip assembly. 
     Referring again to  FIG. 6 , the bottom end assembly  497  which in this case includes a packer cup  498  facilitates sealing against the inside surface  402  of work piece  401 . Also provided in the bottom end assembly  497  is stabbing guide  499  which facilitates alignment of the tool with and subsequent insertion of the tool into the proximal end of work piece  401 . 
     Referring again to  FIG. 6 , which shows a cross section view of the bi-axially activated internally gripping tubular running tool with motor driven load screw activation and helical wedge grip. The tubular running tool  400  is shown inserted into and tractionally engaged with work piece  401  such that the lower face  486  of bump ring  485  is in contact with the proximal end of the work piece  401 . Drive motors  480  have been activated resulting in mandrel  403  being driven helically downward such that the jaws  470  are displaced radially outwards sufficiently for grip surface  473  to engage the inside surface  402  of work piece  401 . Right hand torque has also been applied to the load adaptor sufficiently so that cam pair  457  is engaged, resulting in an axial downward movement of the cage  460  such that the jaws  470  are moved downward relative to mandrel  403  and radially outward by contact with window  464  in cage  460 . The movement of the cage relative to the mandrel is allowed by providing sufficient backlash between carrier thread  413  of mandrel  403  and carrier thread  466  of cage  460 . 
     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.