Patent Description:
Power tongs have for many years been used to "make up" (i.e., assemble) threaded connections between sections (or "joints") of tubing, and to "break out" (i.e., disassemble) threaded connections when running tubing strings into or out of petroleum wells, in coordination with the hoisting system of a drilling rig. Tubing strings typically comprise a number of tubing sections having externally-threaded ends, joined end-to-end by means of internally-threaded cylindrical couplers mounted at one end of each tubing section, forming what is commonly called the "box" end, while the other externally-threaded end of the tubing section is called the "pin" end. Such tubular strings can be relatively efficiently assembled or disassembled using power tongs to screw additional tubing sections into a tubing string during make-up operations, or to unscrew tubing sections from a tubing string being pulled from a wellbore (i.e., break-out operations).

However, power tongs do 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 wellbore. Running tubulars with tongs, whether powered or manual, also typically requires the deployment of personnel in comparatively high-hazard locations such as on the rig floor and on so-called "stabbing boards" above the rig floor.

The advent of drilling rigs equipped with top drives has enabled another method of running tubing strings, and casing strings in particular, using tools commonly known as casing running tools or CRTs. These tools are configured to be carried by the top drive quill, and to grip the upper end of a tubing section and to seal between the bore of the tubing section and the bore of the top drive quill. In coordination with the top drive, CRTs support hoisting, rotating, pushing, and filling of a casing string with drilling fluid while running casing into a wellbore.

Ideally, these tools also support make-up and break-out operations traditionally performed using power tongs, thereby eliminating the need for power tongs entirely, with attendant benefits in terms of reduced system complexity and increased safety. As a practical matter, however, obtaining these benefits without negatively impacting running rate or consistency requires the time taken to make up connections using CRTs to be at least comparable to that required for the running rate and consistency achievable using power tongs. In addition, it is a practical reality that making up tubing strings using CRTs does increase the risk of damage to the connection threads, or to seals in so-called "premium connections" where these are present.

<CIT>) [the contents of which are incorporated herein in their entirety, in jurisdictions where so permitted] teaches a prior art CRT in the form of a gripping tool that includes a body assembly comprising:.

For purposes of this patent document, a CRT configured for gripping an internal surface of a tubular workpiece will be referred to as a CRTi, and a CRT configured for gripping an external surface of a tubular workpiece will be referred to as a CRTe.

CRTs as taught by <CIT> utilize a mechanically-actuated gripping assembly that generates its gripping force in response to axial load with corresponding axial stroke, either together with or independently from externally-applied axial load and externally-applied torque load applied by either right-hand or left-hand rotation. These loads, when applied, 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 workpiece.

Additionally, such CRTs or gripping tools may be provided with a latch mechanism acting between the body assembly and the gripping assembly, in the form of a rotary J-slot latch having a hook-and-receiver arrangement acting between first and second latch components, where the first latch component is carried by the body assembly and the second latch component is carried by the grip assembly (for example, see <FIG> and <FIG> in <CIT>, showing the latch in externally-gripping and internally-gripping full-tool assemblies respectively, and also <FIG> in <CIT>, describing how mating latch teeth <NUM> and <NUM> act as a hook and receiver with respect to each other).

When in a first (or latched) position, with the hook in the receiver, this latch prevents relative axial movement between the body assembly and the gripping assembly so as to retain the grip mechanism in a first (or retracted) position. However, relative rotation between the body assembly and the gripping assembly (which rotation is typically resisted by some amount of torque, which will be referred to herein as the "latch actuation torque") will move the mating hook and receiver components to a second (or unlatched) position, thereby allowing relative axial movement between the body assembly and the gripping assembly, with associated movement of the grip surface into the second (or engaged) position. Accordingly, when in the latched position, this latch mechanism will support operational steps that require the gripping assembly to be held in its retracted position, to enable positioning of the tool relative to the workpiece preparatory to engaging the grip surface, and conversely retaining the grip surface in its retracted position enabling separation of the CRT from the workpiece.

Operationally, achieving this relative movement where the CRT is attached to the top drive quill requires the development of sufficient reaction torque, through tractional engagement when the "land surface" of the CRT is brought into contact with the upper end of a tubular workpiece and axial "set-down" force is applied, to resist the latch actuation torque arising from the rotation applied to move the latch into the unlatched position (typically arranged as right-hand rotation) and to cause axial movement if required (i.e., to move the hook up the "slot" of a J-slot). Any operational step moving the latch from the latched position to the unlatched position is said to "trigger" the tool, thus allowing the tool to be "set".

To re-latch, this same requirement for sufficient tractional resistance between the tool's land surface and the workpiece must be met, with the applied torque direction reversed (i.e., typically left-hand rotation) to "un-set" the tool. For mechanically-set CRTs such as in <CIT>, the tractional resistance required to re-latch is less than that required to unlatch.

<CIT>) [the contents of which are incorporated herein in their entirety, in jurisdictions where so permitted] discusses how it may be difficult in some applications to achieve sufficient tractional rezistance between the land surface of a CRT and a workpiece, such as in cases where both the CRT land surface and the contact face of the workpiece are smooth steel, particularly when rotating to release the latch in such tools, <CIT> teaches means for increasing the effective friction coefficient acting between the workpiece and tool under application of compressive load (i.e., the ratio of tractional resistance to applied load). While these teachings disclose effective means for managing this operational variable and thus reducing operational uncertainty, operation of the tool still requires the steps of first setting down a somewhat controlled amount of axial load and then applying rotation with the top drive to move the latch into its unlatched position. Therefore, when the CRT is used to for make-up operations, the time, load, and rotation control to carry out these steps on certain rigs may result in slower cycle times than achievable using power tongs for make-up.

Tubing sections in a tubing string are typically oriented "pin down, box up", Accordingly, during make-up operations, the upper end of the uppermost section in the string, as supported by rig floor slips or a "spider", presents as "box up" in the so-called "stump" into which the pin end of the next tubing section (i.e., workpiece) is stabbed. When using a CRT for make-up, it may be difficult to control the amount of top drive "set-down" load on the stabbed pin and similarly the amount of rotation applied with set-down load present, introducing the possibility of the undesirable situation where the pin end of the workpiece is rotated in the box in the stump before the pin-end and box-end threads are properly engaged, with the attendant risk of galling damage to the threads. While these risks can be ameliorated by careful control of the top drive by the driller, they contribute to both additional uncertainty and increased cycle time.

Accordingly, there is a need for methods and means for reducing the risk of thread damage when using CRTs for make-up, and for providing greater assurance of cycle times comparable to or less than cycle times achievable using power tongs for make-up and other aspects of casing running operations,.

In general terms, the present disclosure teaches non-limiting embodiments of a rotary latch mechanism (alternatively referred to as a trigger mechanism) comprising upper and lower latch assemblies, plus a latch release mechanism comprising an upper rotary latch component carried on and rotationally coupled to the upper latch assembly, and a lower rotary latch component carried on and rotationally coupled to the lower latch assembly. The upper and lower rotary components are configured to move from a first (or axially-latched) position to a second (or axially-unlatched) position in response to rotation of the lower rotary component relative to the upper rotary component in a first (or unlatching) direction. Such rotation induces the development of an associated latch actuation torque,.

The latch release mechanism has a movable land element (alternatively referred to as a "cushion bumper") which carries a downward-facing land surface that acts in response to relative axial displacement to urge relative rotation between the upper and lower rotary latch components, so as to exert the latch actuation torque required to move the latch components from the latched position to the unlatched position. Where needed for latch configurations requiring both relative axial compression movement and rotation (such as commonly required for a J-slot latch), the mechanism may be configured such that the axial movement of the movable land element will cause the relative axial movement required to release the latch in combination with the required rotation. Accordingly, exemplary embodiments in accordance with the present teachings are directed to means for inducing the rotation and latch actuation torque required to move the component forming a rotary latch from the latched position to the unlatched position using externally-controlled axial movement of a movable land element carried by the latch release mechanism, without requiring externally-induced rotation sufficient to move the mechanism from the latched position to the unlatched position,.

Latch release mechanisms as disclosed herein eliminate the need for externally-applied rotation after applying set-down force when using a tool such as a mechanical CRT that employs a J-latch type mechanism to move from a first (latched) to a second (unlatched) position, by transforming relative axial movement between the tubular workpiece and a component of the tool so as to produce the relative rotation needed to release the latch. This enables a mechanical CRT equipped with such a latch release mechanism (or trigger mechanism) to produce comparable or shorter cycle times with reduced risk of connection thread damage while running casing, as compared to using power tongs for such operations.

In one aspect, the present disclosure teaches embodiments of a rotary latch release mechanism comprising:.

such that when the one or more trigger dog teeth are disposed within the one or more trigger reaction dog pockets, an upward force applied to the land surface of the bumper element will tend to cause relative axially-upward displacement of the bumper so as to urge rotation of the lower latch assembly, wherein the trigger element acts between the bumper element and through engagement with the trigger dogs with the upper latch assembly so as to force relative rotation between upper and lower latch components to induce axial disengagement of the upper and lower rotary latch components, whereupon continued application of the upward force and resultant axial and rotary displacement of the bumper element relative to the lower latch assembly will cause withdrawal of the trigger dog teeth from the trigger dog reaction pockets.

The rotary latch release mechanism may include a first axially-oriented biasing means acting between the upper and lower latch assemblies so as to bias the latch release mechanism toward the latched position, and a second axially-oriented biasing means acting between the movable bumper element and the trigger element so as to bias the bumper element axially downward relative to the trigger element.

The upper latch assembly may define a downward-facing upper ramp surface that is matingly engageable with an upward-facing lower ramp surface defined by the lower latch assembly, such that the application of an upward force to the land surface of the bumper element will bring the upper and lower ramp surfaces into sliding engagement so as to constrain the relative axial approach of the upper and lower latch assemblies while allowing relative rotation between the upper and lower latch assemblies.

In another aspect, the present disclosure teaches embodiments of a rotary latch release mechanism acting between (<NUM>) a generally cylindrical main body having a main body bore, and (<NUM>) a generally cylindrical load adaptor coaxially disposed within the main body bore and both axially and rotatably movable therein, with a lower end of the load adaptor being operatively engageable with an axial-load-actuated latching linkage disposed within the main body. In one embodiment, the latch release mechanism comprises:.

In this embodiment, the primary and secondary trigger elements are configured such that axial compressive load applied to the load adaptor will be reacted by contact and engagement of the first reaction surface with the primary trigger reaction surface and the second reaction surface with the secondary trigger extension, causing corresponding axial displacement between the load adaptor and the main body, thereby inducing rotation and axial movement of the secondary trigger element relative to the primary trigger element, thus generating torque and corresponding rotation to unlatch the latching linkage.

Optionally, in alternative embodiments, a plurality of primary trigger dog teeth each comprising a primary trigger dog tooth load flank, a primary trigger dog tooth crest, and a primary trigger dog tooth lock flank, may be provided on the downward-facing reaction surface on the primary trigger element, with a corresponding plurality of mating reaction dog pockets, each defining a reaction pocket load flank, a reaction pocket crest, and a reaction pocket lock flank, being provided on the upward-facing dog reaction surface provided on the main body extension.

Several exemplary embodiments of latch release mechanisms in accordance with the present disclosure are described below, in the context of use with a CRT utilizing a J-latch to retain the grip surface of the CRT in its retracted position, and providing means for triggering the J-latch by application of set-down load without requiring the application of external rotation and latch actuation torque through the load adaptor.

Embodiment #<NUM> relies on tractional resistance to react latch actuation torque. In this embodiment, the latch release mechanism is carried by the lower latch assembly (comprising the grip assembly of a CRT), and has a movable land element (or cushion bumper) with a generally downward-facing land surface adapted for tractional engagement with the upper end of a tubular workpiece. Upward axial compressive movement of the movable land element relative to the lower rotary latch component, in response to contact with a tubular workpiece, causes the latch release mechanism to rotate the lower rotary latch component relative to the upper rotary latch component in the unlatching direction.

The latch release mechanism is further provided with biasing means (such as but not limited to a spring), for biasing the land surface to resist axial compressive displacement relative to the lower rotary latch component, correspondingly producing tractional resistance to rotary sliding between the land surface and the tubular workpiece. Thus arranged, with the upper and lower rotary latch components initially in the axially-latched position, and with the upper latch assembly (comprising the body assembly of a CRT) supported through the load adaptor to resist rotation relative to the tubular workpiece, axial compressive movement transmitted through the load adaptor to the upper rotary latch component relative to the tubular workpiece tends to urge rotation (as well as axial compressive stroke, if required) of the lower rotary latch component relative to the upper rotary latch component, and where tractional resistance between the land surface and the tubular workpiece is sufficient to exceed the latch actuation torque, the axial compressive movement causes rotation relative to the upper rotary latch component to move the lower rotary latch component to the unlatched position.

Embodiment #<NUM>, like Embodiment #<NUM>, relies on tractional resistance to react latch actuation torque. In this embodiment, the upper latch assembly has a load adapter slidingly coupled to a main body to carry axial load while still allowing axial stroke, The upper rotary latch component is axially carried by the main body, but is rotationally coupled to the load adaptor. The lower latch assembly is carried by and is rotationally coupled to the main body, while allowing axial sliding, over at least some range of motion, when in the unlatched position. The lower latch assembly is further configured to carry a land surface for contact with a tubular workpiece to support set-down loads and to provide tractional resistance to rotation.

The latch release mechanism is carried by a selected one of the load adaptor and the main body, and has a generally axially-facing movable clutch surface adapted for tractional engagement with an opposing reaction clutch surface on the other of the load adaptor and the main body, Axial compressive movement of the movable clutch surface relative to the reaction clutch surface, as urged by set-down force applied to the load adaptor, causes the latch release mechanism to urge rotation between the load adaptor and the main body in the unlatching direction, The latch release mechanism is further provided with biasing means (such as but not limited to a spring), for biasing the movable clutch surface to resist axial compressive displacement relative to the component on which it is carried (i.e., either the load adaptor or the main body), correspondingly producing tractional resistance to rotary sliding between the contacting movable clutch surface and the reaction clutch surface (or clutch interface).

Thus arranged, with the upper and lower rotary latch components initially in the axially-latched position, and with the load adaptor supported to generally allow free rotation relative to the main body and hence the tubular workpiece, axial compressive movement within the axial stroke allowance of the load adaptor relative to the main body tends to urge rotation (and axial compressive stroke, if required) of the upper rotary latch component relative to the lower rotary latch component. Where the tractional resistance of the clutch interface is sufficient to exceed the latch actuation torque (and perhaps some external resistance torque of the generally freely-rotating load adaptor), the axial compressive movement induces rotation of the upper rotary latch component relative to the lower rotary latch component to move to the unlatched position.

Where free rotation of the load adaptor is inhibited, the rotation urged by set-down load tends to urge sliding at the clutch interface and at the land-to-workpiece interface. The corresponding torque induced at these two interfaces, upon application of sufficient set-down load, will thus tend to induce sliding on one interface or the other. If sliding occurs on the land-to-workpiece interface, the rotation necessary to release the latch will occur. However, if sliding occurs at the clutch interface, then relative rotation of the latch components will not occur, rendering the latch release mechanism ineffective for its intended purpose in these particular circumstances. It may therefore be advantageous to provide means for increasing the torsional resistance of the clutch interface to increase the effective tractional resistance under application of axial load, such as by providing these mating surfaces as conicallyconfigured surfaces to increase the normal force driving rotational tractional resistance, for a given axial load. Such modifications may be provided in the absence of or in combination with contouring or other surface treatments for increasing frictional resistance.

However, in all cases where it is desired to allow for re-latching, the tractional resistance to rotation occurring at the clutch interface will tend to impede the relative rotation of upper and lower rotary latch components if set-down load is required to effect re-latching. For certain applications it may be possible to reliably control the tractional response of these two interfaces by providing a selected combination of biasing spring force, contact surface geometry, and surface treatment of the clutch and land-to-workpiece surfaces, in coordination with load control sufficient to reliably prevent clutch interface slippage in support of latch release rotation for a first compressive load, while simultaneously allowing clutch interface slippage without resultant land-to-workpiece slippage to support re-latching, for a second selected compressive load in combination with applied rotation.

As described above, Embodiments #<NUM> and #<NUM> rely on the presence of sufficient tractional engagement between contacting components for reliable unlatching with set-down movement. In Embodiment #<NUM>, the only limiting tractional resistance is between the tubular workpiece and the cushion bumper, with the additional constraint that the latch actuation torque is further resisted by external support carrying the upper latch assembly. To state this otherwise, relative rotation between the upper rotary latch component and the tubular workpiece must be largely prevented (at least in the unlatching direction) to support grip engagement without externally-applied rotation.

In Embodiment #<NUM>, sufficient tractional resistance of the clutch interface is required, typically with the added constraint of free rotation of the load adaptor of the upper latch assembly. For applications where these boundary conditions can be readily and reliably met, Embodiments #<NUM> and #<NUM> can provide the benefits of faster cycle times and reduced risk of connection thread damage, plus the benefit of comparative mechanical simplicity. However, for applications where these boundary conditions cannot be readily achieved, means can be provided for releasing a J-latch independent of available tractional resistance or control of top drive rotation, as in alternative embodiments described below.

Embodiment #<NUM> is configured to force relative rotation of the upper and lower rotary latch components through the latch release mechanism. In this embodiment:.

The movable land element and the trigger element are coupled to each other and to the lower latch assembly such that upward axial compressive movement or stroke of the movable land element relative to the lower latch assembly from a first (or land) position to a second (or fully-stroked) position, as urged by contact with a tubular workpiece, will urge rotation and downward axial movement of the trigger dog teeth. Initially, rotation of the trigger dog teeth is prevented by interaction with the reaction dog pockets which causes rotation of the lower rotary latch component relative to the upper rotary latch component to their unlatched position, and when the movable land element is fully stroked, the trigger dog teeth are fully retracted and disengaged from the reaction dog pockets. The retraction of the trigger dog teeth from the reaction dog pockets supports re-latching under application of external rotation in the re-latching direction. This embodiment preferably includes biasing means tending to resist both the axial compression of the movable land element and the retraction of the trigger element, so that the land and trigger elements return to their initial positions upon unloading and withdrawal from the tubular workpiece.

Embodiment #<NUM>, like Embodiment #<NUM>, is configured to force relative rotation of the upper and lower rotary latch components through the latch release mechanism. In this embodiment:.

The latch release mechanism is configured to act between the sliding load adaptor and main body, and, similar to Embodiment #<NUM>, comprises three main elements:.

In the following discussion, it is assumed that the reaction dog pockets are upward-facing and are carried by the main body, and that the primary trigger element (having downward-facing trigger dog teeth) and the secondary trigger element (having a downward-facing standoff surface) are carried by the load adaptor. When the tool is in the latched position, the trigger dog teeth and the reaction dog pockets are configured for aligned engagement upon downward axial sliding movement of the load adaptor through its axial stroke, as urged by contact with a tubular workpiece.

An upward-facing reaction surface is also provided with the reaction dog pockets, and therefore is rigidly carried by the main body and arranged to contact the downward-facing standoff surface at an axial stroke position lower than required for engagement of the trigger dog teeth with the reaction dog pockets. The secondary trigger element and the primary trigger element are coupled to each other and to the load adaptor assembly such that downward axial compressive movement or stroke of the standoff surface relative to the load adaptor from a first (land) position to a second (fully-stroked) position, as urged by contact with a tubular workpiece, will urge both rotation and upward axial movement of the trigger dog teeth.

Initially, rotation of the trigger dog teeth is prevented by interaction with the reaction dog pockets, which causes rotation of the lower rotary latch component relative to the upper rotary latch component to their unlatched position, and when the secondary trigger element is fully stroked, the trigger dog teeth will be fully retracted and disengaged from the reaction dog pockets, and this retraction of the trigger dog teeth will support re-latching under application of external rotation in the re-latching direction. This embodiment preferably includes biasing means tending to resist both axial compression of the secondary trigger element and retraction of the primary trigger element, such that upon unloading and withdrawal from the tubular workpiece, the primary and secondary trigger elements return to their initial positions.

To further support reverse rotation under set-down load as needed to effect re-latching, the secondary trigger element may be provided as a secondary trigger assembly comprising a secondary trigger extension, having a downward-facing standoff surface, threaded to the secondary trigger element but rotationally keyed to the main body such that rotation in the direction of unlatching tends to move the standoff surface lower, causing compressive engagement of the standoff surface and the reaction surface at axially-higher positions, which prevents the premature engagement of the trigger dog teeth with the reaction dog pockets until the rotational position for re-latching has been reached.

Embodiments will now be described with reference to the accompanying Figures, in which numerical references denote like parts, and in which:.

<FIG> illustrates a prior art internally-gripping CRT <NUM> essentially corresponding to the CRTi shown in Figures <NUM> and <NUM> of <CIT>. CRT <NUM> includes a body assembly <NUM>, a grip assembly <NUM>, and a cage <NUM> linked to grip assembly <NUM>. CRT <NUM> is shown in <FIG> as it would appear in the latched position and inserted into a tubular workpiece <NUM> (shown in partial cutaway). In this latched position, relative axial movement between body assembly <NUM> and grip assembly <NUM> is prevented, such that grip assembly <NUM> is held in its retracted position.

The upper end of body assembly <NUM> is provided with a load adaptor <NUM>, illustrated by way of non-limiting example as having a conventional tapered-thread connection <NUM> for structural connection to a top drive quill (not shown) of a drilling rig (not shown). Grip assembly <NUM> includes a land surface <NUM> carried by a fixed bumper <NUM> rigidly attached to cage <NUM> of grip assembly <NUM>. As described in <CIT>, body assembly <NUM> carries an upper rotary latch component, and grip assembly <NUM> carries a lower rotary latch component, which is linked to cage <NUM> so as to be generally fixed against rotation and axial movement relative to cage <NUM> when in the latched position, but configured for rotary movement to an unlatched position in response to typically right-hand rotation of body assembly <NUM> relative to grip assembly <NUM>, with the latch actuation torque corresponding to this rotary movement being reacted by tractional engagement of land surface <NUM> with tubular workpiece <NUM>.

<FIG> illustrates a CRTi <NUM> generally corresponding to CRT <NUM> in <FIG>, but modified to incorporate an embodiment of a rotary latch release mechanism (alternatively referred to herein as a trigger mechanism) in accordance with the present disclosure. CRTi <NUM> is shown in <FIG> as it appears in the latched position. In this particular embodiment, CRTi <NUM> includes a latch release mechanism <NUM> (schematically illustrated in figures that follow) comprising:.

Cage extension <NUM>, trigger element <NUM>, and movable bumper <NUM> are generally configured as a coaxially-nested group of closely-fitting cylindrical components, where relative rotary and translational movements between these components are constrained to keep them coaxially aligned, but also linked by cam pairs in the manner of cam followers and cam surfaces as described later herein.

<FIG>, <FIG>, <FIG>, <FIG>, and <FIG> schematically illustrate the operative relationships of the various components of latch release mechanism <NUM>, at sequential stages of the operation of latch release mechanism <NUM>. Although latch release mechanism <NUM> is a three-dimensional rotary assembly, in order to facilitate a clear understanding of the structure and operation of latch release mechanism <NUM>, the basic components of latch release mechanism <NUM> are shown in <FIG> in a generally two-dimensional schematic manner, with the tangential (rotary) direction being transposed into the horizontal direction, and with the axial direction being transposed into the vertical direction.

<FIG> illustrate latch release mechanism <NUM> in relation to a schematically-represented CRT, still in the fully-latched position, with a schematically-represented tubular workpiece <NUM> disposed slightly below movable bumper <NUM>. Reference number <NUM> represents an upper latch assembly rigidly coupled to body assembly <NUM> of the CRT, and having a trigger reaction dog pocket <NUM> and an upper rotary latch receiver <NUM>. Reference number <NUM> represents a lower latch assembly comprising a cage extension <NUM> incorporating a lower rotary latch hook <NUM> shown in the latched position relative to upper rotary latch receiver <NUM>. Upper latch assembly <NUM> carries an internal upper cam ramp surface <NUM>, shown nearly in contact with an internal lower cam ramp surface <NUM> on cage extension <NUM>, with an internal biasing spring <NUM> disposed and acting between body assembly <NUM> and cage extension <NUM>. These features are shown to represent the internal reactions and forces operative between body assembly <NUM> and grip assembly <NUM> of the CRT, to facilitate an understanding the functioning of the CRT in coordination with latch release mechanism <NUM>.

Cage extension <NUM> carries a movable bumper <NUM> having a movable land surface <NUM> and a trigger element <NUM>. Movable bumper <NUM> is linked to trigger element <NUM> by a bumper-trigger cam follower <NUM> rigidly fixed to movable bumper <NUM> and movable within an axially-oriented bumper-trigger cam slot <NUM> (having an upper end <NUM> and a lower end <NUM>) formed in trigger element <NUM>, such that movable bumper <NUM> is axially movable relative to trigger element <NUM>. A bumper-cage cam follower <NUM>, rigidly fixed to cage extension <NUM>, is constrained to move within a bumper-cage cam slot <NUM> formed in movable bumper <NUM> (with bumper-cage cam slot <NUM> having an upper end <NUM> and a lower end <NUM>); and a trigger-cage cam follower <NUM>, rigidly fixed to cage extension <NUM>, is constrained to move within a trigger-cage cam pocket <NUM> provided in trigger element <NUM>.

Notwithstanding the particular and exemplary arrangement of the components of the latch release mechanism <NUM> as described above and illustrated in <FIG>, it will be apparent to persons skilled in the art that the choice of fixing the cam follower to one or the other of two components to be paired, and the cam profile in the other, is arbitrary with respect to the relative movement constraint, and corresponding freedom, associated with such a mechanism. Similarly, the choice of cam follower/cam surface as the means for providing the desired movement constraint is not intended to be in any way limiting. Persons skilled in the art will readily understand that generally equivalent mechanism can be provided in other forms without departing from the intended scope of the present disclosure.

In the illustrated embodiment, bumper-trigger cam slot <NUM> is provided as an axially-oriented slot, closely fitting with the diameter of the associated bumper-trigger cam follower <NUM>, and thus having a single degree of freedom to permit only relative axial sliding movement between trigger element <NUM> and movable bumper <NUM> but not relative rotation, with a trigger bias spring <NUM> being provided to act between trigger element <NUM> and movable bumper <NUM>, in the direction of axial sliding, to bias movable bumper <NUM> downward relative to trigger element <NUM>. Bumper-cage cam slot <NUM> is sloped at a selected angle relative to the vertical (shown by way of non-limiting example in <FIG> as approximately <NUM> degrees) and is closely-fitting with the diameter of the associated bumper-cage cam follower <NUM> to provide a single degree of freedom linking relative axial movement of movable bumper <NUM> to rotation of cage extension <NUM>. However, free movement of trigger-cage cam follower <NUM> is permitted within the trapezoidal trigger-cage cam pocket <NUM>, constrained only by contact against cam constraint surfaces defining the perimeter of trigger-cage cam pocket <NUM>, as follows:.

During typical operations, the operative status of latch release mechanism <NUM> may be characterized with reference to the position of trigger-cage cam follower <NUM> within trigger-cage pocket <NUM>, as follows:.

When latch release mechanism <NUM> is in the latched position (as shown in <FIG>), bumper-cage cam follower <NUM> is positioned toward upper end <NUM> of bumper-cage cam slot <NUM>, and trigger-cage cam follower <NUM> is urged toward the start position within trigger-cage cam pocket <NUM> by trigger bias spring <NUM>. At the same time, trigger bias spring <NUM> maintains the engagement of trigger dog tooth <NUM> within trigger reaction dog pocket <NUM>, which engagement can position trigger dog tooth lock flank <NUM> in close opposition with reaction pocket lock flank <NUM> of trigger reaction dog pocket <NUM>, as in this illustrated embodiment, so as to prevent accidental rotation of upper latch assembly <NUM> relative to lower latch assembly <NUM> as controlled by the selection of the mating flank angle and gap, where a more vertically-inclined angle is selected to more strongly resist rotation for a given trigger bias spring <NUM> force.

It will be apparent that upper rotary latch receiver <NUM> and lower rotary latch hook <NUM> (configured as a J-slot requiring axial displacement) already provides some protection against accidental rotation. However, for the type of J-latch typically employed in CRTs where axial displacement is not required and unlatching with only torque is allowed, the trigger dog tooth lock flank <NUM> and mating reaction pocket lock flank <NUM> provide the additional benefit of protection against accidental rotation.

In actual operation of the rotary latch release mechanism, the contact force reacted by tubular workpiece <NUM> against movable land surface <NUM> tends to build as CRTi <NUM> is lowered. However, as a matter of convenience for purposes of illustration in <FIG>, upper latch assembly <NUM> will be considered as the datum, with tubular workpiece <NUM> being viewed as tending to move upward relative to upper latch assembly <NUM>, and correspondingly tending to urge movable land surface <NUM> upward (rather than downward as in actual operation).

Referring now to <FIG>, where the force of trigger bias spring <NUM> is sufficient to prevent relative movement between the components of latch release mechanism <NUM>, force applied to movable land surface <NUM> will be transmitted through to cage extension <NUM>, with upward movement being resisted until the force of internal biasing spring <NUM> is overcome, resulting in upward movement of the entire lower latch assembly <NUM>, and correspondingly moving lower rotary latch hook <NUM> axially upward relative to upper rotary latch receiver <NUM>. This upward movement is restricted by contact between internal upper cam ramp surface <NUM> and internal lower cam ramp surface <NUM>, as illustrated in <FIG>.

While such upward movement causing axial separation of lower rotary latch hook <NUM> from upper rotary latch receiver <NUM> is not a required movement for the type of J-latch typically employed for all CRTs, as will be known to persons skilled in the art, mating lower rotary latch hook <NUM> and upper rotary latch receiver <NUM> can alternatively be configured to disengage in response to applied torque only.

Independent of whether the applied load is first sufficient to overcome the force of the internal biasing spring <NUM>, when sufficient force is applied by tubular workpiece <NUM> to overcome the force of trigger bias spring <NUM>, movable bumper <NUM> will move upward, causing bumper-cage cam follower <NUM> to move downward within sloped bumper-cage cam slot <NUM>, as shown in <FIG>. The upward movement of movable bumper <NUM> tends to cause rotation of cage extension <NUM>, but such rotation is resisted by the actuation torque acting between upper latch assembly <NUM> and lower latch assembly <NUM>. This torque is transferred through movable bumper <NUM> to trigger element <NUM> via bumper-cage cam follower <NUM> and cam slot <NUM>, and through trigger dog tooth load flank <NUM> to reaction pocket load flank <NUM> and thence back to upper latch assembly <NUM>, thus internally reacting the latch actuation torque and causing trigger-cage cam follower <NUM> to move along trigger advance cam surface <NUM> to the advanced position within trigger-cage cam pocket <NUM>, thus moving the rotary latch to its unlatched position as shown in <FIG>. This movement is illustrated as right-hand rotation of upper latch assembly <NUM> relative to lower latch assembly <NUM>.

As may be understood with reference to <FIG>, further upward movement of movable bumper <NUM> continues to urge rotation of cage extension <NUM>, causing: (<NUM>) movement of trigger-cage cam follower <NUM> to the withdrawn position within trigger-cage cam pocket <NUM>, (<NUM>) resultant downward movement of trigger element <NUM>, and (<NUM>) corresponding withdrawal of trigger dog tooth <NUM> from engagement with trigger reaction dog pocket <NUM>. The slope angle of trigger withdraw cam surface <NUM> of trigger-cage cam pocket <NUM> is selected relative to the orientation of bumper-cage cam slot <NUM> to promote the withdrawal of trigger dog tooth <NUM> without jamming or otherwise inducing excess force considering the operative trigger bias spring <NUM> force and frictional forces otherwise tending to affect the withdrawal movement. Furthermore, it will be apparent that with trigger element <NUM> withdrawn from trigger reaction ring <NUM>, upper latch assembly <NUM> is free to rotate relative to the lower latch assembly <NUM>, and, more specifically, allows left-hand rotation of upper latch assembly <NUM> relative to lower latch assembly <NUM> to re-latch the tool.

This rotation supports movement of lower rotary latch hook <NUM> into engagement with upper rotary latch receiver <NUM> (i.e., the latched position), with corresponding actuation torque being resisted by tractional engagement of movable land surface <NUM> with tubular workpiece <NUM>. In general, though, the portion of the set-down load carried by contact between internal upper cam ramp surface <NUM> and internal lower cam ramp surface <NUM>, as a function of the associated cam ramp angle, tends to require less tractional engagement for this re-latching movement than required for unlatching in tools having different types of latch release mechanisms.

Referring now to <FIG>, it will be seen that as the operational step to remove the tool from tubular workpiece <NUM> causes a reduction of the upward axial force acting on movable land surface <NUM>, trigger bias spring <NUM> urges movable bumper <NUM> downward and correspondingly causes rotation of movable bumper <NUM> relative to cage extension <NUM>, possibly with associated sliding at the interface between movable land surface <NUM> and tubular workpiece <NUM>, and resultant tractional frictional force acting in the direction to maintain latching. This movement of movable bumper <NUM> and the force from trigger bias spring <NUM> tend to urge trigger element <NUM> to reverse the withdrawal movement just described, moving trigger dog tooth <NUM> upward. However, this upward movement is prevented when trigger dog tooth crest <NUM> slidingly engages reaction pocket crest <NUM>, forcing trigger-cage cam follower <NUM> to move from the withdrawn position toward the reset position within trigger-cage cam pocket <NUM>.

As movable bumper <NUM> continues to move downward, following the movement of tubular workpiece <NUM>, a point is reached where trigger dog tooth crest <NUM> no longer engages (i.e., slides off) reaction pocket crest <NUM>, thereby allowing trigger-cage cam follower <NUM> to move from the reset position and back toward the start position within trigger-cage cam pocket <NUM>, thus returning latch release mechanism <NUM> to the operational state shown in <FIG>, in which the tool is once again ready to initiate the operational sequence illustrated in <FIG> and <FIG> and <FIG>.

<FIG> illustrates a CRTi <NUM> modified to incorporate an exemplary embodiment of a latch release mechanism <NUM> in accordance with the present disclosure, and a tri-cam latching linkage <NUM> generally as disclosed in <CIT>. <FIG>, <FIG>, <FIG>, and <FIG> illustrate sequential operational stages of latch release mechanism <NUM>.

In the embodiment illustrated in <FIG>, modified CRTi <NUM> comprises a body assembly <NUM> incorporating a load adaptor <NUM> for structural connection to the top drive quill of a drilling rig (not shown), a grip assembly <NUM> comprising a cage <NUM> and jaws <NUM>, latch release mechanism <NUM>, and tri-cam latching linkage <NUM>. Tri-cam latching linkage <NUM> comprises an upper latch assembly <NUM> fixed to and carried by body assembly <NUM>, and a lower latch assembly <NUM> fixed to and carried by grip assembly <NUM>.

As illustrated in <FIG>, latch release mechanism <NUM> includes an upper latch assembly <NUM> comprising a drive cam body <NUM> carrying a plurality of drive cam latch hooks <NUM>, and a drive cam housing <NUM>, with drive cam body <NUM> being rigidly constrained to body assembly <NUM> of CRTi <NUM>. Latch release mechanism <NUM> further includes a lower latch assembly <NUM> comprising a driven cam body <NUM>, a driven cam housing <NUM>, and a latch cam <NUM>, with latch cam <NUM> having a plurality of latch cam latch hooks <NUM>, and being rigidly constrained to grip assembly <NUM> of CRTi <NUM>, Tri-cam latching mechanism <NUM> also includes an intermediate cam body w having load threads <NUM> on the inside surface that engage with load threads <NUM> on the outside surface of drive cam body <NUM>.

A drive cam body-housing seal <NUM>, a drive cam body-mandrel seal <NUM>, a drive housing-driven housing seal <NUM>, a drive cam body-cage seal <NUM>, and a cage mandrel seal <NUM> define an annular piston area and a gas spring chamber <NUM>. When pressurized with a gas, gas spring chamber <NUM> forms an internal gas spring that tends to urge the separation of upper latch assembly <NUM> and lower latch assembly <NUM>, thereby tending to urge separation of body assembly <NUM> and grip assembly <NUM> to move latch release mechanism <NUM> between a first (unlatched) position and a second (latched) position. Such separation is resisted by matingly-engageable drive cam latch hooks <NUM> and latch cam latch hooks <NUM>, which can be disengaged by the application of sufficient right-hand torque (i.e., latch actuation torque) and corresponding right-hand rotation of body assembly <NUM> relative to grip assembly <NUM>. Tri-cam latching linkage <NUM> is considered to be in the latched position when drive cam latch hooks <NUM> and latch cam latch hooks <NUM> are engaged, and in the unlatched position when drive cam latch hooks <NUM> and latch cam latch hooks <NUM> are disengaged.

The following section details a mechanism that can be employed to use only axial compression and corresponding axial displacement to generate the right-hand torque and rotation required to unlatch the tri-cam latching linkage <NUM>, having reference to <FIG>, which is a cross-section through latch release mechanism <NUM> shown in the latched position. For purposes of the discussion of this mechanism, the body assembly <NUM> will be considered as the datum, and the tubular workpiece <NUM> will be viewed as tending to move upward.

As illustrated in <FIG>, latch release mechanism <NUM> comprises a trigger reaction ring <NUM> fixed to body assembly <NUM>, a trigger element <NUM>, a trigger bias spring <NUM>, a movable bumper <NUM> having a movable land surface <NUM>, a bumper cam follower <NUM>, and a cage extension <NUM> fixed to grip assembly <NUM>. The components of latch release mechanism <NUM> and tri-cam latching linkage <NUM> are generally configured as a coaxially-nested group of closely-fitting cylindrical components, with relative rotary and translational movements between these components being constrained to first maintain them in coaxial alignment.

In operation, CRTi <NUM> with latch release mechanism <NUM> would first be inserted or "stabbed" into tubular workpiece <NUM> and lowered until movable land surface <NUM> contacts tubular workpiece <NUM>, and the contact force resulting from tool weight and set-down load applied by the top drive (not shown) increases above the "trigger set-down load", at which point latch release mechanism <NUM> has applied the required latch actuation torque and the displacement required to disengage drive cam latch hooks <NUM> and latch cam latch hooks <NUM>. The gas spring will cause axial displacement of body assembly <NUM> relative to grip assembly <NUM>, transitioning CRTi <NUM> with latch release mechanism <NUM> from the retracted position to the engaged position. This operational sequence differs from prior art CRT <NUM> in two ways:.

As best understood with reference to <FIG>, trigger reaction ring <NUM> has one or more downward-facing trigger reaction dog pockets <NUM>, each of which is generally defined by a reaction pocket load flank <NUM>, a reaction pocket crest <NUM>, and a reaction pocket lock flank <NUM>, with each trigger reaction dog pocket <NUM> being engageable with a corresponding upward-facing trigger dog tooth <NUM>. Each trigger dog tooth <NUM> is generally defined by a trigger dog tooth load flank <NUM>, a trigger dog tooth crest <NUM>, and a trigger dog tooth lock flank <NUM> (when the tool is in the latched position as shown in <FIG>). Movable bumper <NUM> and trigger element <NUM> are linked by bumper cam follower <NUM>, fixed to movable bumper <NUM> and movable within a trigger cam slot <NUM> provided in trigger element <NUM>, between an upper end <NUM> and a lower end <NUM> of trigger cam slot <NUM>. Additionally, movable bumper <NUM> is linked to cage extension <NUM> by bumper cam follower <NUM>, which is constrained to move within a bumper-cage cam slot <NUM> between an upper end <NUM> and a lower end <NUM> thereof. Trigger element <NUM> is linked to cage extension <NUM> by a trigger cam follower <NUM>, which is fixed to trigger element <NUM> and is constrained to move within a cage cam pocket <NUM> provided in cage extension <NUM>. Additionally, cage extension <NUM> is rigidly fixed to driven cam body <NUM>.

It will be apparent to persons skilled in the art that the cam follower can be fixed to either of the two components to be paired, with the cam profile defined in the other of the two paired components, and that the design choice in this regard will typically be based on practical considerations such as efficiency of assembly, disassembly and maintenance. Similarly, the choice of cam follower/cam surface as the means for providing the desired movement constraint is not intended to be in any way limiting, where persons skilled in the art will understand that generally equivalent mechanisms can be provided in other forms.

In the embodiment shown in <FIG>, trigger cam slot <NUM> is provided as an axially-oriented slot, closely fitting with bumper cam follower <NUM>, and thus generally providing a single degree of freedom to permit relative axial movement between trigger element <NUM> and movable bumper <NUM>, but not permitting relative rotation. Trigger bias spring <NUM> is provided to act between trigger element <NUM> and movable bumper <NUM> in the direction of axial sliding, to bias movable bumper <NUM> downward, Bumper-cage cam slot <NUM> is sloped at a selected angle relative to the vertical (shown by way of non-limiting example in <FIG> as approximately <NUM> degrees), and is closely-fitting with the associated bumper cam follower <NUM> to provide a single degree of freedom linking relative axial movement of movable bumper <NUM> to rotation of cage extension <NUM>. However, free movement of trigger cam follower <NUM> is permitted within trapezoidal cage cam pocket <NUM>, constrained only by contact against cam surfaces defining the perimeter of cage cam pocket <NUM>, as follows:.

During typical operations, the operative status of latch release mechanism <NUM> may be characterized with reference to the position of trigger cam follower <NUM> within cage cam pocket <NUM>, as follows:.

With the latch release mechanism in the latched position as in <FIG>, with bumper cam follower <NUM> positioned at lower end <NUM> of bumper-cage cam slot <NUM>, trigger bias spring <NUM> will urge trigger cam follower <NUM> toward the start position within cage cam pocket <NUM>, while simultaneously maintaining the engagement of trigger dog teeth <NUM> within corresponding trigger reaction dog pockets <NUM>. This engagement of trigger dog teeth <NUM> disposes trigger dog tooth lock flanks <NUM> in close opposition to corresponding reaction pocket lock flanks <NUM> so as to prevent accidental rotation of upper latch assembly <NUM> relative to lower latch assembly <NUM> as controlled by the selection of the mating flank angle and gap. If necessary, a more axially-aligned camming surface may be selected to more strongly resist rotation for a given force exerted by trigger bias spring <NUM>.

Referring now to <FIG>, when sufficient force is applied by tubular workpiece <NUM> to overcome the force of trigger bias spring <NUM>, movable bumper <NUM> moves upward, causing bumper cam follower <NUM> to move axially upward within bumper-cage cam slot <NUM>. This axially-upward axial movement tends to rotate cage extension <NUM>, but such rotation is resisted by the latch actuation torque acting between upper latch assembly <NUM> and lower latch assembly <NUM>, which torque is transmitted through movable bumper <NUM> to trigger element <NUM> via bumper cam follower <NUM> and trigger cam slot <NUM>, and through trigger dog tooth load flank <NUM> to reaction pocket load flank <NUM> and to upper latch assembly <NUM>. This causes the latch actuation torque to be internally reacted, and causes trigger cam follower <NUM> to move along advance cam surface <NUM> to the advanced position within cage cam pocket <NUM>, thereby disengaging drive cam latch hooks <NUM> from latch cam latch hooks <NUM> and changing the state of tri-cam latching linkage <NUM> from the latched position as in <FIG> to the unlatched position as in <FIG>, through right-hand rotation of upper latch assembly <NUM> relative to lower latch assembly <NUM>.

Once drive cam latch hooks <NUM> and latch cam latch hooks <NUM> have disengaged, the gas spring urges separation of upper latch assembly <NUM> from lower latch assembly <NUM>. It is at this point in the operational sequence of casing runhing that a combination of axial tension and rotation will be applied during the course of connection make-up to induce right-hand rotation of upper latch assembly <NUM> relative to lower latch assembly <NUM>. During this stage of operation, latch release mechanism <NUM> will not interfere with the regular function of the casing running tool.

Further upward movement of movable bumper <NUM> continues to urge rotation of cage extension <NUM> and, therefore, movement of trigger cam follower <NUM> to the withdrawn position within cage cam pocket <NUM>, thereby moving trigger element <NUM> down and correspondingly withdrawing trigger dog teeth <NUM> from engagement with trigger reaction dog pockets <NUM> as shown in <FIG>. The angle of withdraw cam surface <NUM> relative to sloped bumper-cage cam slot <NUM> may be selected so as to promote the withdrawal of trigger dog teeth <NUM> from engagement with trigger reaction dog pockets <NUM> without jamming or otherwise inducing force in excess of the operative trigger bias force and frictional forces otherwise tending to affect the withdrawal movement.

With trigger element <NUM> withdrawn from trigger reaction ring <NUM> as shown in <FIG>, trigger dog tooth lock flank <NUM> is no longer opposite reaction pocket load flank <NUM>, so upper latch assembly <NUM> can be rotated relative to lower latch assembly <NUM> in order to re-latch tri-cam latching linkage <NUM>. As may be seen in <FIG>, this rotation of upper latch assembly <NUM> relative to lower latch assembly <NUM> causes latch cam latch hooks <NUM> to move into engagement with drive cam latch hooks <NUM> (i.e., the latched position), with the corresponding actuation torque induced by this rotation being resisted by tractional engagement of movable land surface <NUM> with tubular workpiece <NUM>.

Referring now to <FIG>, with CRTi <NUM> thus in the re-latched position, as the operational step of removing CRTi <NUM> from tubular workpiece <NUM> reduces the axial force acting on movable land surface <NUM>, trigger bias spring <NUM> urges movable bumper <NUM> downward and correspondingly causes movable bumper <NUM> to rotate relative to cage extension <NUM>, with possible attendant sliding between movable land surface <NUM> and tubular workpiece <NUM>. Tractional frictional force from trigger bias spring <NUM> thus tends to urge trigger element <NUM> to reverse the withdrawal movement described above, moving trigger dog teeth <NUM> upward. However, this upward movement of trigger dog teeth <NUM> is prevented by sliding engagement of trigger dog tooth crests <NUM> with reaction pocket crest <NUM>, forcing trigger cam follower <NUM> to move from the withdrawn position to the reset position within cage cam pocket <NUM>, As movable bumper <NUM> continues to move downward, following the movement of tubular workpiece <NUM>, a point is reached where trigger dog tooth crests <NUM> no longer engage (i.e., they slide off) reaction pocket crest <NUM>, thereby allowing trigger cam follower <NUM> to move from the reset position to the start position within cage cam pocket <NUM>, thus returning latch release mechanism <NUM> to the position shown in <FIG>, from which position the operational sequence shown in <FIG> can be repeated.

There will now be described a latch release mechanism which in quasi-static operation relies on tractional resistance between movable land surface <NUM> of movable bumper <NUM> and tubular workpiece <NUM>. This latch release mechanism is a modification to the latch release mechanism <NUM> described previously herein under the heading "CRTi Embodiment". As used in this disclosure, the phrase "quasi-static operation" with respect to a latch release mechanism is to be understood as referring to operation of the mechanism such that axial load is applied in a sufficiently slow manner that dynamic effects associated therewith are minimal or negligible.

<FIG> is a sectional view of a prior art CRTi <NUM> fitted with a tri-cam latching linkage <NUM> and a latch release mechanism <NUM> carried by lower latch assembly <NUM> and comprising a movable bumper <NUM>, a bumper cam follower <NUM> fixed to movable bumper <NUM>, a trigger bias spring <NUM>, and a cage extension <NUM>, which are generally configured as a coaxially-nested group of closely-fitting cylindrical components, with relative rotary and translational movements between these components being constrained so as to keep them coaxially aligned. Tri-cam latching linkage <NUM>, movable bumper <NUM>, and bumper cam follower <NUM> in <FIG> are identical to those previously described under the "CRTi Embodiment" heading and depicted in <FIG>.

As best understood with reference to <FIG> and <FIG>, movable bumper <NUM> and cage extension <NUM> are linked by bumper cam follower <NUM>, which is movable within a cage cam slot <NUM> provided in cage extension <NUM> and between an upper end <NUM> and a lower end <NUM> of cage cam slot <NUM>. Cage cam slot <NUM> is sloped at a selected angle (shown by way of non-limiting example in <FIG> as approximately <NUM> degrees) relative to the longitudinal axis of the tool, and is closely-fitting with the associated bumper cam follower <NUM>, which defines a translational-rotational relationship between movable bumper <NUM> and cage extension <NUM>. Additionally, cage extension <NUM> is rigidly fixed to driven cam body <NUM>, and trigger bias spring <NUM> is provided to act between cage extension <NUM> and movable bumper <NUM> to bias movable bumper <NUM> axially downward, as well as biasing bumper cam follower <NUM> to be in contact with lower end <NUM> of cage cam slot <NUM>.

It will be apparent to persons skilled in the art that bumper cam follower <NUM> can be fixed to either one of the two components to be paired, with the cam profile being defined in the other one of the paired components. The design choice in this regard will typically be based on practical considerations including efficiency of assembly, disassembly, and maintenance. Similarly, the choice of cam follower/cam surface as the means for providing the desired movement constraint is not intended to be in any way limiting; persons skilled in the art will understand that functionally effective alternative mechanisms can be provided in other forms.

For purposes of the present discussion, body assembly <NUM> will be considered as the datum, relative to which tubular workpiece <NUM> will be viewed as tending to move upward. As shown in <FIG> and <FIG>, when tri-cam latching linkage <NUM> is in the latched position, bumper cam follower <NUM> will be positioned at lower end <NUM> of cage cam slot <NUM> due to the axial downward force applied by trigger bias spring <NUM>. In operation, CRTi <NUM> with latch release mechanism <NUM> will be lowered until movable land surface <NUM> on movable bumper <NUM> contacts tubular workpiece <NUM>, and the contact force resulting from tool weight and set-down load applied by the top drive (not shown) increases above the "trigger set-down load", at which point latch release mechanism <NUM> will have applied the required latch actuation torque and the rotation required to disengage drive cam latch hooks <NUM> from latch cam latch hooks <NUM>.

As illustrated in <FIG> and <FIG>, when sufficient force is applied in a quasi-static manner by tubular workpiece <NUM> to overcome the force of trigger bias spring <NUM>, movable bumper <NUM> will move upward, generating torque between itself and cage extension <NUM> due to the interaction of bumper cam follower <NUM> within cage cam slot <NUM>, which torque, for the movable bumper <NUM>, must be reacted by tractional engagement of movable land surface <NUM> with tubular workpiece <NUM>, which tractional engagement, if sufficient, will result in rotation of cage extension <NUM>.

The rotation of cage extension <NUM> will be resisted by the latch actuation torque acting between upper latch assembly <NUM> and lower latch assembly <NUM>. The latch actuation torque will be transmitted from upper latch assembly <NUM> to load adaptor <NUM>, and in turn must be reacted by the top drive, thereby disengaging drive cam latch hooks <NUM> from latch cam latch hooks <NUM>, and resulting in movement of tri-cam latching linkage <NUM> from a latched position as shown in <FIG> to an unlatched position as shown in <FIG>, through right-hand rotation of upper latch assembly <NUM> relative to lower latch assembly <NUM>. Once drive cam latch hooks <NUM> and latch cam latch hooks <NUM> have disengaged, a gas spring associated with latch release mechanism <NUM> (generally as previously described with reference to latch release mechanism <NUM>) will urge upper latch assembly <NUM> to separate from lower latch assembly <NUM>.

It will be apparent to persons skilled in the art that the described latch release mechanism <NUM> will be able to generate the latch actuation torque and corresponding rotation required to move CRTi <NUM> from a disengaged position to an engaged position by means of quasi-static application of axial set-down load and displacement only, provided that the following two boundary conditions can be readily met:.

In instances where the above two conditions can be readily and reliably met, latch release mechanism <NUM> can provide the benefits of faster cycle times, operational simplicity, and comparative mechanical simplicity.

Additionally, the nature of the tool's operation can be taken advantage of to supplement the tractional engagement between movable land surface <NUM> and tubular workpiece <NUM>, i.e., movable bumper <NUM> can be designed with a high moment of inertia about the tool's axis relative to the combined moment of inertia of the cage extension <NUM> and grip assembly <NUM>, and when the set-down load is applied with sufficient speed, the cage extension <NUM> and grip assembly <NUM> will have a greater tendency to rotationally accelerate, causing right-hand rotation of upper latch assembly <NUM> relative to lower latch assembly <NUM>, and disengaging drive cam latch hooks <NUM> from latch cam latch hooks <NUM>.

To disengage CRTi <NUM> from tubular workpiece <NUM>, set-down load and left-hand torque are applied to load adaptor <NUM> and are reacted between movable bumper <NUM> and tubular workpiece <NUM>. When the set-down load and left-hand torque are sufficient, upper latch assembly <NUM> will rotate in the left-hand direction relative to lower latch assembly <NUM>, causing drive cam latch hooks <NUM> to move into engagement with latch cam latch hooks <NUM> (i.e., into the latched position), with the corresponding torque induced by this rotation being resisted by tractional engagement of movable land surface <NUM> with tubular workpiece <NUM>.

The operational step of removing CRTi <NUM> from tubular workpiece <NUM> will reduce the axial force acting on movable land surface <NUM>, with trigger bias spring <NUM> urging movable bumper <NUM> downward and correspondingly causing movable bumper <NUM> to rotate relative to cage extension <NUM>, with possible attendant sliding between movable land surface <NUM> and tubular workpiece <NUM> and resultant tractional frictional force acting in the direction to maintain latching. With sufficient axial downward movement of tubular workpiece <NUM>, bumper cam follower <NUM> will contact lower end <NUM> of cage cam slot <NUM>, thus returning latch release mechanism <NUM> to the position shown in <FIG>, from which position the operational sequence shown in <FIG> can be repeated.

<FIG> is a sectional view of a prior art externally-gripping casing running tool (CRTe) <NUM> comprising a main body assembly <NUM>, which has a main body upper housing <NUM> rigidly fixed to a main body lower housing <NUM>, a floating load adaptor <NUM> for structural connection to the top drive quill of a drilling rig (not shown), a grip assembly <NUM> that rigidly carries a fixed bumper <NUM>, and a tri-cam latching linkage <NUM> comprising an upper latch assembly <NUM> axially fixed to main body assembly <NUM>, and a lower latch assembly <NUM> fixed to and carried by grip assembly <NUM>. Upper latch assembly <NUM> is rotationally coupled to floating load adaptor <NUM>, and comprises a drive cam <NUM> that carries a plurality of drive cam latch hooks <NUM>, plus a drive cam housing <NUM>. Lower latch assembly <NUM> comprises a driven cam <NUM>, plus a latch cam <NUM> that carries a plurality of latch cam latch hooks <NUM>.

As shown in <FIG>, an upper cam-housing seal <NUM>, a main body-housing upper seal <NUM>, a lower cam-housing seal <NUM>, a main body-housing lower seal <NUM>, a lower cam-cage seal <NUM>, and a upper cam-cage seal <NUM> define a gas spring chamber <NUM>, with lower cam-housing seal <NUM> and upper cam-cage seal <NUM> defining a piston area carried by lower latch assembly <NUM>. When pressurized with a gas, gas spring chamber <NUM> forms an internal gas spring that tends to urge separation of upper latch assembly <NUM> from lower latch assembly <NUM>, and thereby tending to urge separation of main body upper housing <NUM> from grip assembly <NUM> so as to move CRTe <NUM> from a retracted position to an engaged position relative to tubular workpiece <NUM>.

Such separation is resisted by matingly-engageable drive cam latch hooks <NUM> and latch cam latch hooks <NUM>, which can be disengaged by the application of sufficient right-hand torque (i.e., latch actuation torque) and corresponding right-hand rotation of floating load adaptor <NUM> relative to main body assembly <NUM>. In the prior art CRTe <NUM>, latch actuation torque is applied through floating load adaptor <NUM>, and is reacted through tractional engagement between tubular workpiece <NUM> and a land surface <NUM> provided on fixed bumper <NUM>. The tri-cam latching linkage <NUM> is considered to be in the latched position when drive cam latch hooks <NUM> and latch cam latch hooks <NUM> are engaged, and in the unlatched position when drive cam latch hooks <NUM> and latch cam latch hooks <NUM> are disengaged.

As also shown in <FIG>, floating load adaptor <NUM> has a floating load adaptor upper axial shoulder <NUM> that permits the transfer of axial tension loads through contact with an axial shoulder <NUM> of the main body assembly <NUM>. Additionally, floating load adaptor <NUM> has a floating load adaptor lower axial shoulder <NUM> that permits the transfer of axial compression loads through contact with an axial shoulder <NUM> on upper latch assembly <NUM> which in turn transfers the axial compression loads to main body upper housing <NUM>. The axial distance between axial shoulder <NUM> on main body upper housing <NUM> and axial shoulder <NUM> on upper latch assembly <NUM> is greater than the axial distance between upper axial shoulder <NUM> and lower axial shoulder <NUM> on floating load adaptor <NUM>, thereby providing an axial range through which floating load adaptor <NUM> can move without transferring axial tension or compressive loads to main body assembly <NUM>.

These components of latch release mechanism <NUM> are generally configured as a coaxially-nested group of closely-fitting, generally cylindrical components, with relative rotational and translational movements between these components being constrained to keep them in coaxial alignment as will be described in greater detail below.

In operation, CRTe <NUM> would first be inserted or "stabbed" over tubular workpiece <NUM>, and the contact force resulting from tool weight and set-down load applied by the top drive (not shown) would increase, causing corresponding axial displacement between main body assembly <NUM> and floating load adaptor <NUM>, enabling latch release mechanism <NUM> to generate the required latch actuation torque and corresponding rotation to unlatch tri-cam latching linkage <NUM>, with the gas spring causing axial displacement between grip assembly <NUM> and main body assembly <NUM> transitioning CRTe <NUM> from the an initial retracted position to an engaged position. This operational sequence for CRTe <NUM> differs from the operation of prior art CRTe <NUM> in two ways:.

The following discussion describes how latch release mechanism <NUM> generates latch actuation torque and corresponding rotation by means of set-down load and axial displacement only.

<FIG> is a cross-section through CRTe <NUM>, with the grip assembly <NUM>, tubular workpiece <NUM>, and main body lower housing <NUM> hidden for clarity, and <FIG> is a section through latch release mechanism <NUM> of CRTe <NUM>, shown in both views in an initial latched position. Load adaptor extension <NUM> is rigidly fixed to floating load adaptor <NUM> by one or more load adaptor lugs <NUM>, and rigidly carries one or more load adaptor cam followers <NUM>, each of which is constrained to move within a primary trigger cam slot <NUM> provided by primary trigger <NUM> and within a secondary trigger cam slot <NUM> provided by secondary trigger <NUM>. Primary trigger cam slot <NUM> also has a vertical lower portion <NUM> contiguous with upper portion <NUM>. Upper portion <NUM> of primary trigger cam slot <NUM> is sloped at a selected angle from the vertical (which angle may vary along the length of upper portion <NUM>). The relative axial and rotational movements between load adaptor extension <NUM> and primary trigger <NUM> are therefore bounded by upper and lower portions <NUM> and <NUM> of primary trigger cam slot <NUM>.

Secondary trigger cam slot <NUM> is axially oriented and closely fitting to load adaptor cam follower <NUM>, thereby coupling the rotation of load adaptor extension <NUM> and secondary trigger <NUM>. Secondary trigger cam slot <NUM> has a lower end <NUM>, plus an upper end <NUM> which load adaptor cam follower <NUM> is biased to be in contact with by trigger bias spring <NUM>, which acts between secondary trigger <NUM> and load adaptor extension <NUM> to apply an axially-downward biasing force to secondary trigger <NUM>. Relative axial movement between load adaptor extension <NUM> and secondary trigger <NUM> is therefore constrained within the upper end <NUM> of secondary trigger cam slot <NUM> and secondary trigger cam slot lower end <NUM>.

Secondary trigger <NUM> rigidly carries one or more secondary trigger cam followers <NUM>, each of which is close-fitting within a dog retraction cam slot <NUM> provided on primary trigger <NUM>. Each dog retraction cam slot <NUM> has an upper end <NUM>, which is circumferentially oriented and constrains secondary trigger <NUM> and primary trigger <NUM> to initially be axially coupled, and which transitions to a lower end <NUM> that is sloped at a selected angle (which angle may vary along the length of lower end <NUM>) from the vertical, and is close-fitting to a corresponding secondary trigger cam follower <NUM> to define a translational-rotational relationship between secondary trigger <NUM> and primary trigger <NUM>. Relative axial and rotational movement between secondary trigger <NUM> and primary trigger <NUM> is therefore constrained within upper and lower ends <NUM> and <NUM> of dog retraction cam slots <NUM>.

Referring still to <FIG> and <FIG>, secondary trigger extension <NUM> has a secondary trigger extension thread <NUM>, with a defining helix in the left-hand direction, that engages a secondary trigger thread <NUM> provided on secondary trigger <NUM>. Additionally, secondary trigger extension <NUM> has a secondary trigger extension lug <NUM> closely fitting to axially-oriented slots <NUM> provided on main body extension <NUM> so as to couple the rotation of main body extension <NUM> and secondary trigger extension <NUM>. Main body lock <NUM> is held fixed to main body upper housing <NUM> by main body lock lugs <NUM>. Clamp ring <NUM> is axially bolted to main body lock <NUM>, with the axial load generated from the bolted connection being transferred into a clamp ring load shoulder <NUM> provided on clamp ring <NUM>, to a main body extension load shoulder <NUM> provided on main body extension <NUM>, and in turn reacted between a main body extension lock surface <NUM> and an upper housing lock surface <NUM> provided on main body assembly <NUM>, which engagement allows main body extension <NUM> to tractionally resist torsional loads that may be generated by latch release mechanism <NUM>. Thus arranged, main body extension <NUM> can first be assembled onto main body assembly <NUM> and rotationally positioned, and then clamp ring <NUM> can be secured, effectively rigidly connecting main body extension <NUM> to main body assembly <NUM>.

As shown in <FIG>, a plurality of primary trigger dog teeth <NUM>, each comprising a primary trigger dog tooth load flank <NUM>, a primary trigger dog tooth crest <NUM>, and a primary trigger dog tooth lock flank <NUM>, may be provided on a downward-facing primary trigger reaction surface <NUM> on primary trigger <NUM>, with a corresponding plurality of mating reaction dog pockets <NUM>, each defining a reaction pocket load flank <NUM>, a reaction pocket crest <NUM>, and a reaction pocket lock flank <NUM> being provided on an upward-facing dog reaction surface <NUM> provided on main body extension <NUM>. In this illustrated embodiment, primary trigger dog teeth <NUM> initially are rotationally aligned with but axially separated from corresponding mating reaction dog pockets <NUM>.

<FIG> is a sectional view of CRTe <NUM>, and <FIG> is a sectional view of latch release mechanism <NUM>, both shown after contact between tubular workpiece <NUM> and fixed bumper <NUM> has been established and sufficient axial set-down load and corresponding displacement have been generated to cause load adaptor extension <NUM>, floating load adaptor lug <NUM>, primary trigger <NUM>, load adaptor cam follower <NUM>, secondary trigger <NUM>, secondary trigger cam follower <NUM> and secondary trigger extension <NUM> to translate axially downwards until primary trigger dog tooth crests <NUM> and their corresponding reaction pocket crests <NUM> initiate contact, at which point a standoff surface <NUM> provided on secondary trigger extension <NUM> is close to but not in contact with a second reaction surface <NUM> provided on main body extension <NUM>.

Referring to <FIG> and <FIG>, continued set-down load and corresponding displacement will cause primary trigger <NUM> to begin to move axially upwards, and to rotate in the right-hand direction, tending to unlatch tri-cam latching linkage <NUM>, as a result of the constraints imposed on primary trigger <NUM> by the engagement of load adaptor cam follower <NUM> in the upper portion <NUM> of primary trigger cam slot <NUM>. This rotation causes the engagement of primary trigger dog tooth load flank <NUM> with reaction pocket load flank <NUM>, producing torque on main body extension <NUM> in the direction tending to unlatch tri-cam latching linkage <NUM>. The torque applied to main body extension <NUM> is resisted by tractional engagement between main body extension lock surface <NUM> and upper housing lock surface <NUM> and is transferred into main body assembly <NUM>. It will now be apparent that the latch release mechanism <NUM> is able to generate the torque and corresponding rotation in the direction tending to unlatch the tri-cam latching linkage <NUM> with the application of set-down load and displacement only.

Referring now to <FIG> and <FIG>, further set-down load and corresponding axial displacement will cause secondary trigger cam followers <NUM> to engage lower ends <NUM> of dog retraction cam slots <NUM>. This engagement tends to move primary trigger dog teeth <NUM> axially upward relative to main body extension <NUM>, transferring the axial set-down load initially reacted between primary trigger dog tooth crests <NUM> and reaction pocket crests <NUM> to be reacted between standoff surface <NUM> and second reaction surface <NUM>. With sufficient set-down load and corresponding displacement, primary trigger dog teeth <NUM> will become completely disengaged from reaction dog pockets <NUM>, allowing relative rotation between the main body assembly <NUM> and floating load adaptor <NUM> in either direction.

<FIG> and <FIG>, respectively, are sectional views of CRTe <NUM> and latch release mechanism <NUM>, both shown after sufficient set-down load has been applied to unlatch tri-cam latching linkage <NUM> whereupon floating load adaptor <NUM> has been moved axially upwards, removing the axial set-down load. At this point, right-hand (or left-hand) rotation can be applied to floating load adaptor <NUM> to make up (or break out) the casing string connection. As shown in <FIG> and <FIG>, the application of right-hand rotation between floating load adaptor <NUM> and main body assembly <NUM> will cause standoff surface <NUM> to move axially downwards due to the left-hand thread formed by secondary trigger extension thread <NUM> and secondary trigger thread <NUM>, which downward axial movement in turn causes standoff surface <NUM> to engage second reaction surface <NUM> at relatively higher axial positions of floating load adaptor <NUM>.

Alternatively, as shown in <FIG> and <FIG>, right-hand rotation can be applied immediately after the axial set-down load and corresponding displacement are sufficient to disengage primary trigger dog teeth <NUM> from the corresponding reaction dog pockets <NUM>, rather than moving floating load adaptor <NUM> axially upwards and then applying right-hand rotation. In this scenario, standoff surface <NUM> engages second reaction surface <NUM>, and the application of right-hand rotation to floating load adaptor <NUM> will generate axially-upward force and corresponding displacement of secondary trigger <NUM>. The axially-upward displacement of secondary trigger <NUM> causes load adaptor cam follower <NUM> to engage lower portion <NUM> of primary trigger cam slot <NUM>.

In either case, right-hand rotation will cause standoff surface <NUM> to move axially downward, and when set-down load is reapplied to re-latch tri-cam latching linkage <NUM>, standoff surface <NUM> will engage second reaction surface <NUM>, thereby preventing primary trigger dog teeth <NUM> from re-engaging reaction dog pockets <NUM>, and thus supporting the application of torque and rotation in the left-hand direction tending to re-latch tri-cam latching linkage <NUM>, as depicted in <FIG> and <FIG>. With tri-cam latching linkage <NUM> in the latched position, grip assembly <NUM> will now be retracted from tubular workpiece <NUM>, while fixed bumper <NUM> is still in contact with tubular workpiece <NUM>.

<FIG> and <FIG> show CRTe <NUM> in the re-latched position. As the operational step of removing CRTe <NUM> from tubular workpiece <NUM> reduces the axial force acting on land surface <NUM>, trigger bias spring <NUM> urges secondary trigger <NUM> downward, and correspondingly causes primary trigger <NUM> to rotate in the left-hand direction and to move axially downwards relative to floating load adaptor <NUM>. However, downward movement of primary trigger <NUM> is impeded by sliding engagement of primary trigger dog tooth crests <NUM> and dog reaction surfaces <NUM>. As floating load adaptor <NUM> continues to move upward, a point is reached where primary trigger dog tooth crests <NUM> no longer engage (i.e., they slide off) dog reaction surfaces <NUM>, thus allowing primary trigger dog teeth <NUM> to re-engage reaction dog pockets <NUM>. Further axially-upward movement of floating load adaptor <NUM> will leave primary trigger dog teeth <NUM> rotationally aligned but axially separated from reaction dog pockets <NUM>, thus returning latch release mechanism <NUM> to the position shown in <FIG> and <FIG>, from which position the operational sequence illustrated in <FIG> can be repeated.

Having reference to the preceding description of the operation of latch release mechanism <NUM>, it will be apparent to persons skilled in the art that:.

It will also be apparent to persons skilled in the art that:.

It will be readily appreciated by those skilled in the art that various alternative embodiments may be devised without departing from the scope of the present teachings, including modifications that may use equivalent structures or materials subsequently conceived or developed.

It is to be especially understood that it is not intended for apparatus in accordance with the present disclosure to be limited to any described or illustrated embodiment, and that the substitution of a variant of a claimed element or feature, without any substantial resultant change in the working of the apparatus and methods, will not constitute a departure from the scope of the disclosure.

In this patent document, any form of the word "comprise" is to be understood in its non-limiting sense to mean that any element or feature following such word is included, but elements or features not specifically mentioned are not excluded. A reference to an element or feature by the indefinite article "a" does not exclude the possibility that more than one of such element or feature is present, unless the context clearly requires that there be one and only one such element or feature.

Any use of any form of the terms "connect", "engage", "couple", "latch", "attach", or any other term describing an interaction between elements is not meant to limit the interaction to direct interaction between the subject elements, and may also include indirect interaction between the elements such as through secondary or intermediary structure.

Relational and conformational terms such as (but not limited to) "vertical", "horizontal", "coaxial", "cylindrical", "trapezoidal", "upward-facing", and "downward-facing" are not intended to denote or require absolute mathematical or geometrical precision. Accordingly, such terms are to be understood as denoting or requiring substantial precision only (e.g., "substantially "vertical" or "generally trapezoidal") unless the context clearly requires otherwise.

In particular, it is to be understood that any reference herein to an element as being "generally cylindrical" is intended to mean that the element in question may have inner and outer diameters that vary along the length of the element.

Wherever used in this document, the terms "typical" and "typically" are to be understood and interpreted in the sense of being representative of exemplary common usage or practice only, and are not to be understood or interpreted as implying essentiality or invariability.

Claim 1:
A latch mechanism (<NUM>) having a longitudinal axis and comprising: an upper latch assembly (<NUM>, <NUM>) and a lower latch assembly (<NUM>, <NUM>), said upper latch assembly (<NUM>, <NUM>) and the lower latch assembly (<NUM>, <NUM>) being coaxially aligned, and wherein:
(a.<NUM>) an upper latch component (<NUM>, <NUM>) is carried on and rotationally coupled to the upper latch assembly (<NUM>, <NUM>);
(a.<NUM>) a lower latch component (<NUM>, <NUM>) is carried on and rotationally coupled to the lower latch assembly (<NUM>, <NUM>);
(a.<NUM>) the upper latch component (<NUM>, <NUM>) and the lower latch component (<NUM>, <NUM>) are movable between:
• a latched position, in which relative axial separation of the upper latch assembly (<NUM>, <NUM>) and the lower latch assembly (<NUM>, <NUM>) is constrained by mating engagement of the upper latch component (<NUM>, <NUM>) and the lower latch component (<NUM>, <NUM>); and
• an unlatched position, in which the upper latch component (<NUM>, <NUM>) and the lower latch component (<NUM>, <NUM>) are disengaged and relative axial separation of the upper latch assembly (<NUM>, <NUM>) and the lower latch assembly (<NUM>, <NUM>) is permitted within a defined range;
in response to relative rotation and associated torque between the upper latch assembly (<NUM>, <NUM>) and the lower latch assembly (<NUM>, <NUM>) in a first rotational direction; characterised in that the latch mechanism further comprises a latch release mechanism (<NUM>) carrying an axially-movable land element (<NUM>, <NUM>) and having actuation means for inducing relative rotation and an associated latch actuation torque sufficient to move the upper latch component (<NUM>, <NUM>) and the lower latch component (<NUM>, <NUM>) from the latched position to the unlatched position in response to axial movement of the land element (<NUM>, <NUM>) resulting from axial force externally applied to the land element (<NUM>, <NUM>).