Patent Application
20090014169
The present invention is directed to an apparatus and a method for securely gripping and releasing a tubular segment for use in drilling operations, particularly for hoisting the tubular segment into alignment with a tubular string.
Wells are drilled into the earth's crust using a drilling rig. Tubular strings are lengthened by threadably coupling add-on tubular segments to the proximal end of the tubular string. The tubular string is generally suspended within the borehole using a rig floor-mounted spider as each new tubular segment or stand is coupled to the proximal, end of the tubular string just above the spider. A single joint elevator is used to grip and secure the segment or stand to a hoist to lift the segment or stand into position for threadably coupling to the tubular string.
For installing a string of casing, existing single joint elevators generally comprise a pair of hinged body halves that open to receive a tubular segment and close to secure the tubular within the elevator. Elevators are specifically adapted for securing and lifting tubular segments having conventional connections. A conventional connection comprises an internally threaded sleeve that receives and secures an externally threaded end from each of two tubular segments to secure the segments in a generally abutting relationship. The internally threaded sleeve is first threaded onto the end of a first tubular segment to form a “box end.” The externally threaded “pin end” of the second tubular segment is threaded into the box end to complete the connection between the segments. Typical single joint elevators have a circumferential shoulder that forms a circle upon closure of the hinged body halves. The shoulder of the elevator engages the tubular segment under a shoulder formed by the end of the sleeve and the tubular segment. However, conventional single joint elevators cannot grip a tubular segment having integral connections, because an integral connection has no sleeve to form a circumferential shoulder.
What is needed is a single joint elevator that is securable to a tubular at any position along the length of the tubular segment, and not only at the sleeve. What is needed is a versatile single joint elevator that can automatically and positively open and close about a tubular segment having either integral connections or conventional connections.
The present invention provides a single joint elevator for gripping a tubular segment to be hoisted by a hoisting member. The single joint elevator comprises a first jaw retainer having a proximal end pivotally coupled to a proximal end of a second jaw retainer for movement of the retainers between an opening position for receiving a tubular segment and a closed position for engaging the tubular segment. Each jaw retainer secures at least one jaw, and each jaw has at least one gripping surface for engaging the tubular segment. The single joint elevator also includes a powered door pivotally coupled to the distal end of the first jaw retainer for selectively securing to the distal end of the second jaw retainer. The powered door includes a pivotable collar, a linear actuator assembly supported by the pivotable collar, and a linkage mechanism for selectively closing the door. In operation, the linear actuator assembly selectively clamps the distal ends of the first and second jaw retainers with sufficient force for the jaws to grip and support the tubular segment for lilting. In order to selectively open the powered door, the linear actuator assembly should include a double-acting actuator.
In one embodiment, the linear actuator assembly includes a fluid powered motor and a drive screw rotatably coupled to the fluid powered motor, wherein the drive screw threadably engages a stationary screw collar secured to the pivotable collar. The linkage mechanism is also acted upon by the linear actuator assembly to selectively move the powered door into a closed position during a first phase of actuation. Continued movement of the linear actuator assembly selectively clamps the distal end of the second jaw retainer during a second phase of actuation. The linear actuator assembly preferably further includes a sliding plate cam that moves linearly with the linear actuator assembly to act upon the linkage mechanism. For example, the linkage mechanism may include a bell crank that is rotated by linear movement of the sliding plate cam, and wherein rotation of the bell crank pulls the powered door into the closed position.
The powered door preferably includes a clam shell clamp member that moves with the linear actuator assembly, wherein the second jaw retainer includes a clam shell seat for receiving the clam shell clamp member. Accordingly, the clam shell set self-centers the clam shell clamp member during clamping of the jaw retainers. Most preferably, the clam shell seat includes a slot for receiving a portion of the linear actuator assembly, such as a drive screw.
The foregoing and other objects, features and advantages of the invention will be apparent from the following more particular description of a preferred embodiment of the invention, as illustrated in the accompanying drawings wherein like reference numbers represent like parts of the invention.
The present invention is directed to a single joint elevator for releasably securing a tubular segment to a cable, rope, line or other hoisting member. Accordingly, the tubular segment can be lifted into position to be threadably coupled to a pipe string suspended in a borehole. One embodiment of the invention comprises a first jaw retainer having a proximal end pivotally coupled to a proximal end of a second jaw retainer for movement of the retainers between an opening position for receiving a tubular segment and a closed position for engaging the tubular segment. Bach jaw retainer secures at least one jaw between its proximal end and a distal end, and each jaw has at least one gripping surface for engaging the outer wall of the tubular segment. A powered door is pivotally coupled to the distal end of the first jaw retainer for selectively securing the distal end of the second jaw retainer. The powered door includes an actuator for selectively closing the door and clamping the distal end of the second jaw retainer to the distal end of the first jaw retainer. The actuator selectively clamps the jaw retainers with sufficient force for the jaws to grip and support the tubular segment for lifting. Accordingly, the elevator can be lilted and transfer the weight of the tubular segment to a cable, rope, line or other hoisting member.
First and second jaw retainers are pivotally coupled at the proximal ends. The pivotal coupling or hinge allows the jaw retainers to open wide enough to receive a tubular segment, and then to close around the circumference of the tubular segment. The pivotal coupling or hinge may have an adjustable stop so that the opening of the jaw retainers can be customized for tubular of various diameters. Opening and closing the jaw retainers loosely about the tubular segment may be achieved manually. The jaw retainers may be spring-biased to the open position. The jaw retainers and pivotal coupling must be strong enough to support gripping forces against the tubular segment and must be precise enough that the jaw retainers pivot along a plane that is perpendicular to the axis of the pivot. Any significant misalignment or “play” in the pivot might cause misalignment of the jaws against the tubular segment or misalignment with the door.
Each jaw retainer supports at least one jaw. Preferably, the first and second jaw retainers collectively support at least three jaws, with two jaws on one jaw retainer and at least one jaw on the other jaw retainer. Even more preferably, each jaw retainer will include two jaws spaced apart and angularly oriented about ninety (90) degrees one from the other. The jaws are configured for gripping the outer surface of a tubular segment. Preferably, the jaws have a first gripping surface that faces radially inward to grip the outer surface of the tubular segment and a second surface that is tapered in order to self-tighten the grip by the first gripping surface to the tubular segment when acted upon by the weight of the tubular segment.
The powered door includes a collar pivotally coupled to the first jaw retainer, a linear actuator extendably secured to the collar, and a mechanical linkage coupled between the door and the first jaw retainer. The pivotal coupling between the collar and the first jaw retainer allows the door to move between a fully open position and a fully closed position. In the open position, the door is held open and allows a tubular segment to be received within the jaw retainers. In the closed position, the door may be selectively secured to the second jaw retainer and clamp the distal ends of the jaw retainers to prevent their separation while gripping a tubular segment. The pivotal coupling between the first jaw retainer and the collar must also be strong and precise to withstand the gripping forces and avoid misalignment of the door with the second jaw retainer.
The pivotable collar has a proximal end pivotally secured to the first jaw retainer and a second end that secures a proximal end of the linear actuator, which is selectively extendable and retractable in order to selectively clamp the jaw retainers. Extension and retraction of the linear actuator is preferably powered by a pressurized fluid. Most preferably, the linear actuator is a screw shaft coupled at its distal end to a bi-directional pneumatic motor. By securing a screw collar to the pivotable collar and disposing the screw shaft in threaded engagement with a screw collar, rotation of the pneumatic motor causes in a fluid direction the screw shaft to retract relative to the screw collar. To accommodate retraction of the screw shaft, and therefore clamping of the jaw retainers, one embodiment of the pivotable collar includes a central bore that receives the end of the screw shaft after it has advanced through the screw collar. Most preferably, the pivotable collar includes a tubular portion that is axially aligned with the screw collar for axially receiving the screw shaft.
While the powered door is pivotally coupled to the first jaw retainer, the door must be able to selectively engage and clamp the second jaw retainer. Accordingly, the linear actuator carries a latch element that cooperatively engages with a mating latch element formed on the distal end of the second jaw retainer. The latch elements may be any of any known type of latch, but preferably forms a stable connection under strong clamping forces. In a preferred embodiment, the linear actuator carries a convex clam shell clamp face and the second jaw retainer forms a concave clam shell seat, such that the convex clamp face and concave seat are self aligning under the clamping force applied by operation of the linear actuator. Advantageously, the clam shell seat or other latch element of the second jaw retainer may be provided without any moving parts. Rather, the jaw retainers are clamped by the movement of the latch element carried by the linear actuator in the door.
A linkage mechanism is coupled between the powered door and the first jaw retainer to cause the door to close prior to clamping the distal ends of the jaw retainers. The actuator acts upon the linkage to selectively move the powered door into a clamping position during a first phase of actuation and selectively clamps the distal end of the second jaw retainer during a second phase of actuation. In this manner, the linkage takes advantage of the actuator movement without requiring a dedicated actuator for closing the door and inherently coordinates the closing and clamping movements so that the door must close before it can begin to clamp. Most preferably, the actuator is a double-acting actuator that can reversibly act upon the linkage, so that when the actuator moves in the reverse direction the door must unclamp and selectively release the distal end of the second jaw retainer before acting upon the linkage to selectively move the door to a removed or open position.
It should be recognized that the linkage mechanism may be accomplished in numerous configurations, but preferred configurations will be both simple and reliable. A presently preferred configuration uses a combination of simple mechanical linkages to convert linear actuation to controlled closing of the door. The preferred configuration includes a sliding plate cam secured to the linear actuator, a simple link arm pivotally secured to the first jaw retainer, and a bell crank that is pivotally secured to each of the sliding plate cam, the simple link arm and the pivotable collar. In this configuration, the bell crank pivots about a fixed pivot point on the collar. The bell crank also secures a rod or pin that is received within a groove of the sliding plate cam. A third point on the bell crank is pivotally coupled to a second end of the simple link arm. Retraction of the actuator causes the sliding plate cam to retract along the collar with the bell crank pin sliding through the groove. When a dog leg in the groove reaches the pin, continued retraction of the sliding plate cam imparts a transverse (outward) force on the pin. The bell crank pin, in turn, causes the bell crank to pivot about the fixed pivot point on the collar. The bell crank pivot coupled to the simple link arm also moves about the fixed pivot point and imparting a pulling force (tension) on the simple link arm. In order for this pulling force to rotate the door in a closing direction, a line between the two pivot points of the simple link arm (i.e., the simple link arm pivots with the bell crank and the first jaw retainer) must be inwardly offset from the axis of pivot coupling between the collar and the first jaw retainer. Accordingly, the pulling force on the simple link arm place a rotational moment on the collar and the door closes.
The dog leg in the groove of the sliding plate cam is designed in conjunction with the bell crank and the simple link arm so that the door completely closes during retraction of the linear actuator and positions the latch element of the door in alignment with the latch element of the second jaw retainer. After the pin has slid along the dog leg segment of the groove causing the door to close, the pin enters a second segment of the groove that is parallel to the linear movement of the linear actuator. Continued retraction of the linear actuator causes the pin to slide within this second segment of the groove such that the door is held closed, but causes no further closing movement. The linear actuator retracts until the door is latched and the jaw retainers are clamped.
It should be recognized that reversing the direction of the actuator and the movement of the linear actuator causes door and linkage mechanism to go through a reversal of the foregoing process. In particular, the single joint elevator can be made to release a tubular segment by initiating extension of the linear actuator. Extension of the linear actuator causes the clamping force to loosen, the latch elements to unseat and separate, and then the linkage mechanism forces the door to swing open as the pin slides into and through the dog leg segment of the groove to force rotation of the bell crank. With the door opened, an operator can manually swing the jaw retainers apart to disengage the tubular segment.
As used herein, the term “single joint elevator” is intended to distinguish the elevator from a string elevator that is used to support the weight of the entire pipe string. Rather, a “single joint elevator” is used to grip and lift a tubular segment as is necessary to add or remove the tubular segment to or from a tubular string. Furthermore, a pipe or tubular “segment”, as that term is used herein, is inclusive of either a single pipe or tubular joint or a stand made up of multiple joints of a pipe or other tubular that will be lifted as a unit. In the context of the present disclosure, a tubular segment does not include a tubular string that extends into the well.
The linkage mechanism 26 includes a number of pivotal connections that may be established with pins and nuts, rivets or other known fasteners. However, the exact nature of these pivotal connections will be omitted for simplicity. The linkage mechanism 26 includes a link arm 36 having a pivotal coupling 38 at a proximal end for coupling with the first jaw retainer 12 and a pivotal coupling 40 at a distal end for coupling with a bell crank 42. The bell crank 42 has a fixed pivot coupling 44 for coupling with an arm 46 secured to the collar 22. A slide pin 48 is secured to the bell crank 42 for slidable engagement within a groove 52 formed in a sliding plate cam 50. Furthermore, the screw shaft 54 of the linear actuator assembly 24 is threadably received within a screw collar 56 that is secured to the pivotable collar 22.
The linear actuator assembly 24 includes the sliding plate cam 50 secured to the housing of motor 58 and to the clam shell latch element 60. The motor 58 rotates the screw shaft 54 through a support bearing 62 within the latch element 60. Although the screw shall 54 rotates according to the rotation imparted by the motor 58, the entire linear actuator assembly 24 moves as a unit.
As rotation of the screw shaft 54 continues in the direction of arrow 54′, sliding cam plate 50 will continue to move in the direction of arrow 50′, and the camming action of the grooves 52 of the sliding cam plate 50 of the linear actuator assembly 24 on the slide pin 48 will continue until the slide pin 48 leaves the dog leg segment 64 of the groove 52 and enters the linear position of the groove 52.
The motor 58 may continue to turn the screw shah 54 until the jaw retainers are clamped so tightly by the powered door 18 that the motor will not turn any further. During this further clamping, the slide pin 48 of the bell crank 42 continues to move down the straight segment 74 of the groove 52, although there should be little or no force being applied against the slide pin since the door position is secured. Although a pressurized fluid, such as air, may be continually applied to the motor while the door is clamping the jaw retainers, a suitable screw-type linear actuator may be sufficiently self-locking that the pressurized fluid may be turned off without any loss of clamping forces. With the jaw retainers 12, 14 clamped in this manner, the four jaws 13 forcibly grip and secure the tubular segment 16. This condition of the single joint elevator 10 is maintained during the handling of the tubular segment.
When it is desired for the single joint elevator 10 to release the grip on the tubular segment 16, the motor 58 is reversed to cause extension of the linear actuator assembly 24. As the extension proceeds, the single joint elevator 10 goes through a reversal of the foregoing process of
The terms “comprising,” “including,” and “having,” as used in the claims and specification herein, indicate an open group that includes other elements or features not specified. The term “consisting essentially of,” as used in the claims and specification herein, indicates a partially open group that includes other elements not specified, so long as those other elements or features do not materially alter the basic and novel characteristics of the claimed invention. The terms “a,” “an” and the singular forms of words include the plural form of the same words, and the terms mean that one or more of something is provided. The terms “at least one” and “one or more” are used interchangeably.
The term “one” or “single” shall be used to indicate that one and only one of something is intended. Similarly, other specific integer values, such as “two,” are used when a specific number of things is intended. The terms “preferably,” “preferred,” “prefer,” “optionally,” “may,” and similar terms are used to indicate that an item, condition or step being referred to is an optional (not required) feature of the invention.
It should be understood from the foregoing description that various modifications and changes may be made in the preferred embodiments of the present invention without departing from its true spirit. The foregoing description is provided for the purpose of illustration only and should not be construed in a limiting sense. Only the language of the following claims should limit the scope of this invention.
