TONG

Abstract: A tong for rotating tubulars, the tong having, in certain embodiments, a tong outer case, a rotary movably mounted in the case for rotating a tubular, apparatus for rotating the rotary to rotate the tubular, at least one gripper or jaw (50) movably mounted in the case and movable by the rotary for gripping the tubular, the at least one gripper or jaw having at least one cam following member or roller (51, 52), and at least one non-circular cam surface (20, 30) on the rotary, the at least one cam following member or roller contacting and movable on the at least one non-circular cam surface for maintaining a desired position of the at least one gripper or jaw with respect to the tubular. In certain embodiments a specific cam angle, within certain tolerances, is maintained substantially the entire length along a cam surface.

Description: TONG This invention is directed to operations involving the connection and disconnection of threaded tubular members, both at the surface in making and breaking connections with tongs and, in one particular aspect, in wellbore operations using wellbore tongs; to apparatus and methods for aligning wellbore tubulars; to power tongs used in making and breaking joints of tubular members such as pipe and wellbore casing and tubing; to parts thereof, including, but not limited to cam surface members elements; and methods of the use of these things. Tongs are used to assist in the make-up and break-out of threaded tubular members. Certain operations during the drilling of oil and gas wells and the production of materials therefrom require the connection and disconnection of successive lengths of threaded tubulars such as pipe, casing, or tubing. Tools known as tongs are used to "make" and "break" such connections. Certain known power tongs have a body, a rotary rotatably mounted in said body and at least one active jaw with one, two or more cam rollers or followers. Such a jaw (or jaws), on rotation of the rotary, is cammed against a pipe in the rotary and grips it for rotation with the rotary. The camming action is typically generated by a cam member which is bolted to or machined as part of the rotary and is shaped so that the active jaw is cammed against the pipe on rotation of the rotary relative to the active jaw in one sense and will be released on rotation of the rotary relative to the active jaw in the opposite sense. With known tongs, high torques are applied to tubulars due to combinations of factors such as thread sealing requirements, the presence of corrosion, the existence of distortion, and tolerances in pipe size and weight. Both in the "make" direction of rotation when a shoulder is suddenly encountered, and in the "break" direction at initial engagement of the tong and disengagement of the threads stresses may arise; e.g., with a power-driven tong, in excess of 50,000 foot-pounds (68000 Nm) of torque may be exerted, while die elements which may be relative small, or a jaw or jaws of the tong engage the pipe. The grip mechanism of a tong translates a rotative input force into coplanar vector forces, acting chordally across the joint section. At the points of grip contact with the joint surface, these chordal forces are resolved into normal and tangential components relative to the joint contour and the rotative torque delivery capability of the tong system is a function of the normal component of the chordal vector multiplied by the coefficient of drag (friction) at the joint contact points of the grip elements. Grip elements are often provided with multiple serrations, or penetration features, to provide the interference contact needed at the joint surface for the development of a suitably high coefficient of drag (friction). Torque delivery capability is a function of the normal force times the drag (friction) coefficient times the radius of the joint to be worked and the required magnitude of the normal force varies inversely with the coefficient of drag developed at the contact between the grip elements and the joint surface. Consequently, the distribution, balance and consistency of grip element energising forces are critical factors in the design of a tong mechanism. The prior art discloses a variety of mechanisms involving linkages, levers, wedges, and cams which are in current use for the disposition and balance of the normal and tangential force components. Usually, grip elements, or dies, are disposed within carrier bodies, or jaws, which span a circumferential segment of the joint surface. These jaws are structured to accept the translated input chordal vector and deliver it to the joint surface in normal and tangential components. Fig. IH shows schematically a problem encountered with a prior art tong G having a jaw W with cam following rollers F. While one roller F may be maintained in contact with a corresponding cam surface of a rotary Y, the other roller F fails to contact a cam surface which can result in an unbalanced jaw/pipe contact. Another problem encountered with such systems occurs when both cam rollers are in contact with a cam surface, but the jaw does not contact the pipe squarely. This is shown in Fig. IH, and results in unbalanced contact of the jaw W with an outer surface of a pipe P, which can cause damage to the pipe P. Fig. 2 A shows a prior art tong N as disclosed in U.S. Patent 4,404,876 which has cam surfaces Bi, B 2 , B 3 , B 4 , B 5 , and B 6 on a rotary D. Each of these cam surfaces is a part of a circle when viewed from above as in Fig. 2A. U.S. Patent 4,404,876 discloses certain tong embodiments in which the cam angle does not exceed 5Y 2 degrees; others in which the cam angle is substantially 2 l Λ degrees; and others in which the cam angle is not substantially less than V. degree. The cam angle for a tong, illustrated in Fig. 2B, is the angle between: (a) a line of action from the centre of a rotary (which is also the centre of the tubular being rotated) through a cam following member to a cam surface; and (b) a line through the cam following member normal to the cam surface at the point cam-following-member/cam-surface contact. The "cam angle" is defined in U.S. Patent 4,404,876 as the angle formed by two lines originating at the point of contact between the cam and follower positioned when the dies are in contact with the pipe, by lines originating at the centre of rotation of a rotary or partial ring of the tong and a point on a line perpendicular to the centre line of a throat (for receiving a pipe section) and passing through the centre of rotation and terminating at a point on the cam surface at which the cam follower or roller is positioned when dies or die carriers or jaws are in contact with a pipe section in the tong. Referring to a "cam angle" is a way of quantifying the ratio of tangential force and normal force applied through the cam from the rotary. The normal force at the jaw/pipe interface is equal to the above described normal force modified by the effect of any kinematic device between the jaw and the cam. Theoretically, it is preferred that an optimal cam angle be maintained for whatever position the cam follower or roller has on the entire length of the cam surface. In practice with various prior art circular-section cam surfaces, this is not achieved. Figs. 1A - 1G show a typical prior art power tong T that uses fixed or "centring" jaws J and a movable jaw M to grip pipe for tubular disconnecting and connecting operations. The jaws have gripping elements or dies D for engaging the pipe. An outer case C houses a powered rotary R to which fixed jaws J are mounted. A cam surface S of the rotary moves a movable (ACTIVE or MASTER) jaw M into (and away from) gripping contact with a tubular, e.g. pipe. The movable jaw M has one or two rollers L that move on the cam surface of the rotary. Each jaw has toothed gripping inserts to facilitate engagement with the surface of the tubular (see Fig. IF). Fig. 1G shows the tong T in an "OPEN" position in which the tubular is not gripped. The cam surface S is defined by surfaces Si, S , S 3 , S 4 , S 5 , and S 6 on cam inserts I which are secured to the rotary R. Each of these surfaces is defined by part of a circle when viewed from above. The prior art tong shown in Fig. 1A is a Weatherford Model 14.5-50 High Torque Tong, as described in the brochure "New! Weatherford Model 14.5-50 High Torque Tong," (1991) and the manual entitled "Model 14.5-50 Hydraulic Power Tong Installation, Operation and Maintenance" (1993). It is to be understood that the teachings of the present application are applicable to any tong and any tong system that has one or more grippers or jaws and one or more cam surfaces and that the Model 14.5- 50 tong is shown here for illustrative purposes and not by way of limitation of the scope of the present invention. There has long been a need for a tong which applies a consistent force to a tubular to be rotated. There has long been a need for such a tong that efficiently rotates the pipe without damaging it and without slipping on it. There has long been a need for a tong with a jaw or jaws with two rollers in which the two rollers are maintained in contact with a tong cam surface. According to a first aspect, the present invention provides a tong for rotating tubulars, comprising a tong outer case, a rotary movably mounted in the case for rotating a tubular, apparatus for rotating the rotary to rotate the tubular, at least one gripper movably mounted in the case and movable by the rotary for gripping the tubular, the at least one gripper having at least one cam following member, and at least one non-circular cam surface on the rotary, the at least one cam following member contacting and movable on and with respect to the at least one non-circular cam surface for maintaining a desired position of the at least one gripper with respect to the tubular. Preferably, in this desired position, the at least one jaw (and/or a die, dies, and/or gripping structure thereon) does not slip on the pipe and does not crush or damage the pipe. Further preferred features are set out in claims 2 to 21. Thus the present invention, in certain embodiments, discloses a power tong for use in operations for joining and disconnecting wellbore tubulars. According to a second aspect, the present invention provides a method for rotating a tubular, comprising positioning a tong as described above about the tubular, and rotating the tubular with the tong. According to a third aspect, the present invention provides a cam member for a tong, the cam member having at least one non-circular cam surface. Further preferred features are set out in claims 23 to 28. According to a fourth aspect, the present invention provides a rotary for a tong, comprising a rotary body and at least one non-circular cam surface on the rotary body. In one aspect, "cam angle" as used herein is a way of quantifying the ratio of tangential force and radial force applied through a cam from a rotary of a tong. The radial force at a jaw/pipe interface is equal to the radial force modified by the effect of any kinematic device between the jaw and the cam (see Fig. 2B). The tangential (torquing) force component at the jaw/pipe interface is the tangential force multiplied by the ratio of the radial distance from a cam/roller interface to the pipe centre and the radius of the pipe, modified by the effect of any kinematic device between the jaw and the cam. Thus preferred embodiments of the invention provide a tong with one or more cam followers or cam following rollers on a gripper and one or more non-circular cam surfaces on a rotary of the tong; such tongs including structure and apparatus to apply a consistent force to a gripper so the gripper adequately grips a tubular without slipping on it, crushing it, or damaging it; such a tong with a gripper or gripper and/or with a jaw or jaws with two cam following members or rollers and non-circular cam surfaces so that consistent contact is enhanced and maintained between the cam following members or rollers, the cam surfaces, and the pipe, and therefore consistent desired forces; and parts for and methods of using such a tong. Some preferred embodiments of the invention will now be described by way of example only and with reference to the accompanying drawings, in which: Fig. 1 A is a schematic perspective view of a prior art power tong system for wellbore operations; Fig. IB is a side view and Fig. IC is a top view of part of the tong system of Fig. 1 A; Fig. ID is an exploded view of a rotary assembly of the system of Fig. 1A; Fig. IE is a top perspective view of a rotary of the rotary assembly of Fig. ID; Figs. IF and IG are top schematic views of a rotary and jaws of the tong system of Fig. 1 A; Fig. IH is a top schematic cross-section view of part of a prior art tong; Fig. 2 A is a top view of part of a prior art tong; Fig. 2B is a diagram regarding a tong cam angle; Fig. 3 A is a perspective view of a tong; Fig. 3B is an exploded view of part of the tong of Fig. 3 A; Fig. 3C is a top view of part of the tong of Fig. 3 A; Fig. 3D is a bottom view of the part as shown in Fig. 3C; Fig. 3E is a top view of part of the tong of Fig. 3 A; Fig. 4A is a top perspective view of a tong cam; Fig. 4B is a rear view of the tong cam of Fig. 4 A; Fig. 4C is a bottom view of the tong cam of Fig. 4A; Fig. 4D is a view along line 4D-4D of Fig. 4C. Fig. 5 A is a top perspective view of a tong cam; Fig. 5B is a rear view of the tong cam of Fig. 5 A; Fig. 5C is a bottom view of the tong cam of Fig. 5 A; Fig. 5D is a view along line 5D-5D of Fig. 5C; Figs. 6 A - 6F are top views of tong cams; Fig. 7 A is a rear perspective view of a tong jaw insert; Fig. 7B is a back view of the insert of Fig. 7A; Fig. 7C is a front view of the insert of Fig. 7 A; Fig. 7D is a top view of the insert of Fig. 7 A; Fig. 8 A is a top view of a tong according to the present invention; and Fig. 8B is an enlargement of part of the tong of Fig. 8 A. Fig. 3 A shows a power tong 10 which is like the power tong T of Fig. 1A, but which does not have cam surfaces with the circular section shape (as viewed from above) of the cam surfaces Si - S 6 . Figs. 3B and 4A - 5D show cam inserts 20 and 30 each with cam surfaces 21, 22 and 31, 32 respectively. Each of the cam surfaces 21, 22, 31, 32 is non-circular as viewed from above to facilitate the maintenance of a desired cam angle when cam following rollers 12 of an active jaw 14 are located anywhere on the cam surfaces so that a desired force is exerted consistently on a tubular. Dies 8 engage a tubular to be rotated. It is within the scope of this invention to use any known dies or gripping elements on any jaw of the tong. The additional description of the power tong T above is repeated and incorporated here with respect to the power tong 10. As shown in Fig. 3 A, the power tong 10 has an hydraulic shifting mechanism 11 ; a case 13; a brake system 15; a safety interlock system 17; and a rotary 40. Two fixed or "centring" jaws 19 are secured to the rotary 40. A movable jaw 50 secured to a cradle 23 has two spaced-apart cam following rollers 51, 52 that move on the cam surfaces of the cam inserts 20 and 30, respectively to move the movable jaw 50 with respect to a tubular passing through the tong 10 that is to be rotated, e.g. a pipe 25. Each roller 51, 52 (shown in Fig. 3E with cradle 23 removed) is mounted on a roller shaft 53. A cover 54 secured on top of the cradle 23 holds the roller shafts in place. A latch 56 releasably latches optional 57 and 58 of the rotary shut. A brake block 55 secured to the cradle 23 is part of the brake system 15 and is used to retard the cradle, preventing its rotation while the rotary and cams advance the cradle and jaw toward the pipe, thus temporarily retarding motion of the cradle with respect to the rotary facilitates cam operation. A rounded edge dovetail structure 43, 44 on each cam insert 20, 30 respectively facilitates securement of the cams in corresponding recesses 43a, 44a of the rotary 40. It is within the scope of this invention to provide any tong employing a cam surface which is contacted by a cam follower or cam following roller with a non- circular cam surface (non-circular as viewed from above viewing an edge of the cam surface that defines the shape thereof) that facilitates maintenance of a desired cam angle and, in one particular aspect, maintenance of a desired cam angle substantially along the entire length of the cam surface and/or maintenance of a desired cam angle, preferably within .95 degrees of tolerance, plus or minus, and most preferably within .50 degrees, plus or minus. As shown in Figs. 4A - 5D, the various non-circular cam surfaces 21 , 22 and 31 , 32 are portions of an Archimedes spiral. These particular cam surfaces are designed to maintain a cam angle of about 5 degrees (with tolerances as stated above) for the roller/cam interface along the entire cam surface. In certain preferred embodiments useful cam angles range between 2° and 30°. As shown in Figs. 3E, 4C and 5C, the cams 20 and 30 each have asymmetrical surfaces 21, 22 and 31, 32, respectively. By using such asymmetrical surfaces, the problem illustrated in Fig. IH is alleviated or overcome; i.e., by employing such asymmetrical surfaces, each of the cam following rollers 51, 52 is maintained in contact with its corresponding cam surface so that the jaw 50 is applied in a balanced even manner to the pipe 25 (as in Fig. 3E). In the preferred embodiments shown in Figs. 3E, 4C and 5C, by "asymmetrical" is meant that the "inboard" cam surfaces 21, 31 are not symmetrically shaped or configured with respect to the corresponding "outboard" cam surfaces 22, 32, respectively, e.g. with respect to the intersections of the surfaces. Extended cam surface portions 27, 37, referred to as "ears" or "wings" are optional and are used for greater radial jaw movement on existing rotaries and for increasing cam travel in existing tongs to accommodate tolerances in tong and pipe structure and size. Figs. 6A - 6F present a set of cams 61, 62, 63, 64, 65 and 66 each with corresponding cam surfaces designated by these numerals with "a" or "b". The cams of Figs. 6A and 6B correspond, respectively, to the cams 31, 21 respectively described above and are designed to maintain a cam angle of about 6.5 degrees; those of Figs. 6C and 6D, a cam angle of about 7.5 degrees; and those of Figs. 6E and 6F, a cam angle of about 8.75 degrees. It is within the scope of this invention to provide for a particular tong a set of a plurality of cams of any desired number to achieve any desired cam angles. It is within the scope of this invention that a cam on one side produce a cam angle x, and a cam on other side produce a cam angle y, where y is not equal to x. Figs. 7A - 7D present a jaw 70 having a carrier 72 for a die, dies, and/or gripping element(s) with a rear mounting structure 74 for mounting the jaw 70 to a cradle (as the jaw 50 is mounted to the cradle 23 as described above. The jaw 50 may be mounted to the cradle 23 in any suitable manner, with or without a mounting structure like the mounting structure 74). Figs. 8A and 8B show a tong 80 which is an improvement of the tong of U.S. Patent 4,404,876, which, to the extent it describes this tong 80 (all but cam surface shapes) is incorporated herein for all purposes. The tong 80 has non-circular cam surfaces 81, 82, 83, and 84, like the previously described non-circular cam surfaces. Cam inserts 85, 86, respectively with these surfaces are mounted to a rotary 87 (as are, e.g., the cams 20, 30 described above). Although the cam members and cam surfaces described above have been described as on a rotary, it is within the scope of this invention to provide such a surface or surfaces on a gripper or jaw and to have a cam following member or roller on the rotary for co-action therewith to effect the gripping described herein. In two actual embodiments of the Weatherford 14.50 tong described above, cam angles of 7.5 and 8.75 degrees have been used effectively.

Claims: CLAIMS: 1. A tong for rotating tubulars, the tong comprising: a tong outer case; a rotary movably mounted in the case for rotating a tubular; apparatus for rotating the rotary to rotate the tubular; at least one gripper movably mounted within the rotary and movable by the rotary to grip the tubular, the at least one gripper having at least one cam following member; and at least one non-circular cam surface on the rotary, the at least one cam following member contacting and movable on the at least one non-circular cam surface for maintaining a desired position of the at least one gripper with respect to the tubular. 2. A tong as claimed in claim 1, further comprising at least one centering gripper on the rotary for facilitating the gripping of the tubular. 3. A tong as claimed in claim 1 or 2, wherein the at least one non-circular cam surface comprises a plurality of non-circular cam surfaces. 4. A tong as claimed in claim 1, 2 or 3, wherein the at least one non-circular cam surface has a shape of part of a spiral. 5. A tong as claimed in claim 4, wherein the spiral is an Archimedes spiral. 6. A tong as claimed in any preceding claim, wherein the at least one gripper is at least one jaw. 7. A tong as claimed in claim 6, wherein the at least one jaw is a plurality of jaws. 8. A tong as claimed in any preceding claim, wherein the at least one gripper includes at least one gripping element for engaging the tubular. 9. A tong as claimed in any preceding claim, wherein the at least one cam following member is a roller movably mounted on the at least one gripper. 10. A tong as claimed in claim 1 wherein the at least one non-circular cam surface is on a cam member, the cam member on the rotary. 11. A tong as claimed in any preceding claim, wherein the cam member is secured on the rotary. 12. A tong as claimed in claim 10 or 11, wherein the cam member is releasably secured on the rotary. 13. A tong as claimed in any of claims 1 to 9, wherein the at least one non-circular cam surface is formed integrally of the rotary. 14. A tong as claimed in any preceding claim, wherein the at least one non-circular cam surface is at least two adjacent non-circular cam surfaces. 15. A tong as claimed in claim 14, wherein the at least two adjacent non-circular cam surfaces is two asymmetrical surfaces. 16. A tong as claimed in any preceding claim, wherein the at least one non-circular cam surface is two spaced-apart pairs of cam surfaces, each pair comprising two adjacent non-circular cam surfaces. 17. A tong as claimed in claim 16, wherein each two adjacent non-circular cam surfaces are asymmetrical. 18. A tong as claimed in claim 16 or 17, wherein the at least one cam following member is two spaced-apart cam following rollers movably mounted on the at least one gripper. 19. A tong as claimed in any preceding claim, wherein the desired position of the at least one gripper is maintained within a cam angle range of about 2 degrees to about 30 degrees. 20. A tong as claimed in claim 19 wherein the cam angle ranges between about 3 to about 9 degrees and a specific cam angle of the tong is maintained within a tolerance of plus or minus .95 degrees. 21. A tong as claimed in any preceding claim, wherein a cam angle of the tong is maintained within a tolerance of plus or minus .50 degrees. 22. A method for rotating a tubular, the method comprising positioning a tong as claimed in any preceding claim about the tubular, and rotating the tubular with the tong. 23. A cam member for a tong, the cam member having at least one non-circular cam surface. 24. A cam member as claimed in claim 23, wherein the at least one non-circular cam surface is at least two adjacent non-circular cam surfaces. 25. A cam member as claimed in claim 24, wherein the at least two adjacent non- circular cam surfaces is two asymmetrical surfaces. 26. A cam member as claimed in claim 23, wherein the at least one non-circular cam surface is two spaced-apart pairs of cam surfaces, each pair comprising two adjacent non-circular cam surfaces. 27. A cam member as claimed in claim 26, wherein each two adjacent non-circular cam surfaces are asymmetrical. 28. A set of cam members for a tong, the set comprising a plurality of cam members as claimed in any of claims 23 to 27, each cam member releasably securable to a part of the tong. A rotary for a tong, the rotary comprising a rotary body, and at least one non-circular cam surface on the rotary body.

Inventors: ALLEN JOHN TIMOTHY, BOX STEVEN ANTONY, ALLEN, JOHN, TIMOTHY, BOX, STEVEN, ANTONY
Applicants: HARDING RICHARD PATRICK, WEATHERFORD LAMB, HARDING, RICHARD, PATRICK, WEATHERFORD/LAMB, INC.
Application year: 2000
Main classification: E21B19
IPC codes: E21B19