Tools – Wrench – screwdriver – or driver therefor – Machine
Reexamination Certificate
2000-04-17
2001-05-29
Smith, James G. (Department: 3723)
Tools
Wrench, screwdriver, or driver therefor
Machine
C081S057330
Reexamination Certificate
active
06237445
ABSTRACT:
BACKGROUND OF THE INVENTION
Power tongs and backup tools are devices used to secure together (make up) and detach (break out) threaded ends of adjacent sections of tubular products such as production tubing, casing or drill pipe by gripping, applying torque to, and rotating one of the sections. A power tong applies torque to one tubular member section to cause it to rotate. A backup tool holds the adjacent tubular member section much as pipe wrenches are used often in conjunction with a power tong to grip and prevent rotation of the adjacent sections of tubular product. A backup tool is also capable of applying torque to the tubular product section.
Conventional power tongs and backup tools used in the oil industry often damage the tubular sections. In recent years, major oil companies have required that strings of tubular products must be coupled (“made up”) and decoupled (“broken out”) with a minimum of (i) damage to the tubular products from teeth marks; (ii) deformation of the tubular products; and (iii) cracking of cement or plastic coating on the inside of the tubular products. The goal of these requirements is to minimize concentrations of corrosion and stress on the tubular products resulting from the tears and gouges caused by the gripping teeth of power tongs and backup tools. Also, to maintain integrity of the threaded connection it is desirable to reduce deformation of the pipe by the power tong and backup tool near the location of threads during makeup to assure more compatible meshing of the threads of adjacent products and reduce frictional wear.
U.S. Pat. No. 5,172,613 issued Dec. 22, 1992, entitled “Power Tongs with Improved Gripping Means” (“Wesch I”) and U.S. Pat. No. 5,542,318 issued Aug. 6, 1996, entitled “Bidirectional Gripping Apparatus” (“Wesch II”) are incorporated herein for all purposes. The Wesch I patent discloses a cam ring turned against a concentric drag ring which moves the gripping assemblies into and out of contact with the tubular surface of the pipe. The Wesch II patent discloses bidirectional gripping assemblies having a double-seated linkage which supports a pivoted jaw within a housing so that the jaw may be used to grip a pipe and exert radial force thereon to hold the pipe against the torque applied in opposite directions. U.S. Pat. No. Re. 31,993 (also incorporated herein by reference for all purposes) issued Oct. 1, 1985, as a reissue of U.S. Pat. No. 4,281,535 and describes apparatus to accomplish the task of making and breaking threaded joints of tubular products using wrap-around pivoted jaw assemblies.
Generally, gouging and tearing of pipe is caused by (i) ineffective gripping assemblies; (ii) gripping jaws having insufficient gripping force; or (iii) the gripping surface of the teeth. These conditions can over-stress the pipe when the radial force is applied in addition to torsion force required to either hold or apply torque to the tubular member. The gripping surface (whether teeth or any other friction surface which increases the coefficient of friction between the gripping assembly and the pipe) must be designed to substantially conform to the outer surface of the pipe even though the pipe may not be round or the tong may not be located transversely to the pipe at the time of gripping. Any improper alignment causes reduced contact areas between the pipe and gripping system. Thus it is important that proper alignment be maintained.
Conventional clamp backup tools apply gripping force to jaws with hydraulic rams or arms actuated directly by hydraulic rams. It has been demonstrated that counterforces on the jaws caused by applied torque may compress oil in the hydraulic rams sufficiently to cause skidding of the pipe on the gripping surfaces. Even at 3,000 P.S.I., oil is soft compared to the mechanically applied gripping force discussed herein.
Normally, conventional tongs and backup tools do not apply the gripping force evenly around the pipe. Instead, it is applied to areas around the pipe which are insufficient to minimize the causes of deformation and teeth marks on the surface of the pipe. The balanced pivoted jaws of U.S. Pat. No. Re. 31,993; U.S. Pat. Nos. 5,172,613 and 5,542,318 solve these problems.
U.S. Pat. No. 5,669,653 discloses a backup tool in which a cam wedge is pushed by a fluid cylinder using pivoted jaws. FIG. 3 of U.S. Pat. No. 4,463,635 also discloses a tool having a wedge block which uses a roller to operate two arms to grip a cylinder. Since the wedge is pushed in the tool disclosed in U.S. Pat. No. 5,669,653 in order to cause gripping of a tubular member, the backup tool is unusually long and cumbersome to mount on the power tong. U.S. Pat. No. 5,669,653 also shows an actuating fluid cylinder with two bolts or pins at its base. Seldom is oil field pipe truly round. Accordingly, if an egg-shaped pipe cross section is gripped, side load is transferred to the wedge and therefore to the fluid cylinder.
SUMMARY OF THE INVENTION
In accordance with the present invention, apparatus is provided for gripping the exterior of a tubular member to resist bidirectional rotation of the member from torque applied about the longitudinal axis of the tubular member. The apparatus comprises a body to receive the tubular member and a reactive gripping jaw attached to the body. A pair of arms having first and second ends is provided. Each of the arms is pivotally mounted on the body about an axis parallel with the longitudinal axis of the tubular member. The first end of each arm supports an active gripping jaw and the active gripping jaws, in conjunction with the reactive gripping jaw, receive and secure the tubular member.
A force multiplying device is interposed between the second ends of the arms for engagement with the second ends of the arms. An actuator is coupled to the force multiplying device for moving it in a first direction to engage the second ends of the arms and pivot the arms and move the active gripping jaws so that the tubular member is secured between the reactive gripping jaw and the active gripping jaws with force sufficient to prevent rotation of the tubular member at a predetermined applied torque. The active gripping jaws are disengaged from the tubular member by returning the force multiplying device to its initial position.
In one embodiment the force multiplying device comprises a roller attached to the second end of each arm and a wedge member with two inclined surfaces intermediate the pair of arms for engaging the roller of each arm. Biasing apparatus is provided for maintaining engagement of the rollers against the inclined surfaces in another embodiment the force multiplying device comprises an arcuate cam surface on the second end of each arm and rollers operatively coupled to the actuator for engagement with the arcuate cam surfaces of the arms. Biasing apparatus is also provided for mounting engagement of the rollers with the arcuate cam surfaces. In yet a third embodiment the force multiplying device comprises a toggle block pivotally coupled to the arms with toggles.
In accordance with the present invention the force applied to the pipe outer surface is predetermined and mechanical instead of applied by a hydraulic ram directly to the jaw. The consequential radial loading to the three jaws on the pipe outer surface is sufficient to keep the pipe from rotary skidding at the gripping surfaces when a predetermined torque is applied to the pipe.
In the present invention surfaces on jaws having a high coefficient of friction are urged into frictional engagement with the surface of an elongated member having an outer surface and a longitudinal axis. When force is applied to the elongated member to rotate the elongated member either clockwise or counterclockwise, the surfaces of the jaws are clamped to the elongated member.
For any given torque the radial force is predetermined and uniformly applied on the pipe. The gripping jaw area, as well as number and size of hardened teeth, are predetermined to reduce the forces which tend to cause teeth marks or crush the tubular body to a magnitude les
Kanz Jack A.
Smith James G.
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