Abstract:
Apparatus for gripping tubular members including self aligning gripping jaws with high coefficient of friction for resisting force applied to the elongated member to prevent rotation either clockwise or counterclockwise. Linear cams and cam rollers actuated by a fluid cylinder bring the gripping jaws to an elongated member, applying predetermined gripping force and retract the jaws for removal of the elongated member.

Description:
This application is a division of application Ser. No. 09/260,302 entitled Gripping Apparatus for Power Tongs and Backup Tools filed Mar. 2, 1999 now U.S. Pat. No. 6,116,118. 
     This invention relates to gripping apparatus for power tongs and backup tools used in the oil and gas industry. 
    
    
     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 less than the yield strength of the tubular body. In other words, the number and shape of the hardened teeth in the gripping surface are predetermined so that the force of the teeth on the pipe does not exceed the elastic limit or the ultimate strength of the pipe material at maximum torque. Apparatus employing the invention will hold pipe against either clockwise or counterclockwise rotation, thus obviating the need for changing the structure or the magnitude of force required to hold the pipe against torque applied in either direction. 
     Where marks are absolutely forbidden, the gripping jaw surfaces may be smooth or sandpaper-like and the gripping force increased sufficiently over standard gripping jaw surfaces to keep the gripping jaw surfaces from skidding on the elongated member. 
     In another embodiment a backup tool is provided with a jaw assembly including replaceable gripping inserts with hardened teeth. This embodiment is designed to engage varying diameter tubular members with a gripping force proportional to the applied torque and acts as a unidirectional backup tool with a support system to accommodate reversal of the backup tool for applying gripping force to make or break threads in either direction of the power tongs. Other features and advantages of the invention will become apparent to those skilled in the art in view of the following description taken in connection with the appended claims and attached drawing in which: 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     FIG. 1 is a plan view of a bidirectional backup tool in accordance with the present invention which has a pipe clamped in the jaws of the tool. 
     FIG. 1A is a side elevation view of the bidirectional backup tool of FIG.  1 . 
     FIG. 1B is a plan view of the bidirectional backup tool with jaws open. 
     FIG. 1C is a partial break-out of the jaw in FIG. 1 to illustrate various force vectors. 
     FIG. 1D is an enlarged break-out of the circled area in FIG.  1 . 
     FIG. 2 is a plan view of bidirectional backup tool with jaws open. 
     FIG. 3 is a partial sectional view taken along section  3 — 3  of FIG. 1B with a spring supporting mechanism. 
     FIG. 4 is a partial sectional view taken along lines  4 — 4  in FIG.  2 . 
     FIG. 5 is a partial sectional view taken along lines  5 — 5  in FIG.  2 . 
     FIG. 6 is a sectional view taken along line  6 — 6  in FIG.  2 . 
     FIG. 7 is a plan view of an alternate embodiment of the bidirectional backup tool with jaws closed. 
     FIG. 8 is a plan view of a toggle arrangement for moving the jaws into engagement with the pipe. 
     FIG. 9 is a plan view of an alternate embodiment of the bidirectional backup tool with jaws open. 
     FIG. 10 is a partial sectional view taken along the lines  10 — 10  of FIG.  9 . 
     FIG. 11 is an alternate embodiment of the jaw assembly of FIG.  10 . 
     FIG. 12 is a partial sectional view taken along the lines  12 — 12  of FIG.  13 . 
     FIG. 13 is a partial top view taken of FIG.  12 . 
     FIG. 14 is a partial sectional view taken along line  14 — 14  of FIG.  15 . 
     FIG. 15 is a partial top view of FIG.  14 . 
     FIG. 16 is a plan view of a power tong gripping jaw. 
     FIG. 16A is a plan view of a cam ring in a power tong. 
     FIG. 16B shows power tong force vectors. 
     FIG. 17 is a plan view of alternate embodiment of unidirectional backup tool gripping a large diameter pipe. 
     FIG. 17A is a broken-out view of FIG. 17 clamping a small diameter pipe. 
     FIG. 17B is a broken-out view of the jaw assemblies of FIG. 17 in the open position. 
     FIG. 18 is a front view of the gripping assembly of FIG. 17 for handling different pipe sizes with the same rotary gripping means. 
     FIG. 19 is a partial cross sectional view of the cylindrical dies in FIG.  17 . 
     FIG. 20 is an alternate arrangement for rotary gripping dies. 
     FIG. 21 is a plan view of a bidirectional backup tool in accordance with the present invention which has a pipe clamped in the jaws of the tool. 
     FIG. 22 is a plan view of the tool of FIG. 21 with the jaws open. 
     FIG. 23 is a schematic drawing illustrating various force vectors in the tool of FIG.  21 . 
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
     FIGS. 1,  1 A,  1 B,  1 C,  1 D and  2  illustrate a bidirectional backup tool  10  which has a frame or body  9  formed by spaced top and bottom plates  20  and  21 , respectively, with a pair of pivot arms  22  and  23  pivotally secured to the body  9  by pivot pins  24  and  25 , respectively. Active jaws  26  and  27  and reactive jaw  28  are positioned within the bidirectional backup tool  10 . Active jaw  26  is attached to pivot arm  22  by jaw pin  29  and active jaw  27  is attached to pivot arm  23  by jaw pin  30 . Reactive jaw  28  is attached between top and bottom plates  20  and  21 , respectively, by bolts  31  which also space top and bottom plates  20  and  21  apart by the width of flange  32  on reactive jaw  28 . While FIG. 1 depicts the components of backup tool  10  as symmetrical about a center line from left to right, those skilled in the art will appreciate that the components of such a tool may not always be absolutely symmetrical. 
     Pipe  33  is held within active jaws  26  and  27  and reactive jaw  28  by hardened replaceable inserts  34 ,  35  and  36 , respectively, which substantially conform to the outside diameter of the pipe. Inserts  34 ,  35  and  36  have friction surfaces adjacent the pipe to increase the coefficient of friction. These may be teeth, a sandpaper-like finish or other finish for the inserts  34 ,  35  and  36  or a brake-band type material or non-ferrous alloy design to minimize damage to the pipe under full compressive load. Replaceable inserts  34 ,  35  and  36  may, for example, be secured to backup tool  10  in dovetail grooves  26   a  (FIG. 4) or by screws. 
     Conventional backup tools apply gripping force to the pipe through hydraulic rams. However, the counterforce (which is generated by the pipe as torque) tends to open the jaws by compressing the oil in the hydraulic cylinders. The embodiment shown as backup tool  10  eliminates that problem by using a force loading block or wedge block  37  (FIG. 2) with inclined surfaces providing cam-like or ramp faces. The inclined surfaces preferably have inserts  38  and  39 . Inserts  38  and  39  are preferably replaceable and are secured to force loading block  37  by  72  and  73  and  72   a  and  73   a,  respectively. The piston of fluid cylinder  40  is in threaded engagement with force loading block  37 . 
     By actuating fluid cylinder  40  (which may be a hydraulic or air cylinder), force loading block  37  is pulled to the right (in FIG. 2) causing the pivot arms  22  and  23  to pivot around the pivot pins  24  and  25 . Active jaws  26  and  27  of pivot arms  22  and  23  are thus moved into engagement with the pipe  33 . Initially, edges  45  and  46  of force block  37  engage rollers  43  and  44  of pivot arms  22  and  23  which moves active jaws  26  and  27 , respectively, snugly against pipe  33 . Thereafter, cam surfaces on inserts  38  and  39  engage rollers  43  and  44  and pivot arms  22  and  23  rotate about pivot pins  24  and  25 , respectively, applying force through active jaws  26  and  27  against the pipe  33 . The pipe  33  thus abuts reactive jaw  28  in proportion to the pulling force of fluid cylinder  40 . To release the pipe  33 , force block  37  is pushed by fluid cylinder  40  to the left in FIGS. 1 and 2 into the retracted position shown in FIG.  2 . 
     The combination of force loading block  37  and the rollers on pivot arms  22  and  23  comprise a force multiplying device because the force exerted on rollers  43  and  44  by the actuator  40  to move the arms so that the active jaws are brought into gripping engagement with the pipe is substantially less than the force applied to the surface of the pipe. 
     An extension spring  48  is attached to each pivot arm  22  and  23 . Extension spring  48  functions to bias rollers  43  and  44  toward surfaces  45  and so that the pivot arms  22  and  23  to move active jaws  26  and  27  in and out of engagement with pipe  33 . 
     Since the radial force FRT on pipe  33  is very large, all rollers and cam surfaces must withstand the large compressive stresses generated during operation. Hardness of Rockwell C-29 to C70 is required. Rockwell C-37 to C62 is preferred. 
     As shown in FIG. 1 the top and bottom plates  20  and  21  are tied together by plates  100  and  101  which may be welded to both. These bear against legs  102  and  103  rigidly attached to a power tong. Torque may be measured with a pancake fluid cylinder  104  between plate  100  and leg  102  and connected to pressure gauge  105 . 
     In operation, load block  37  is pulled by fluid cylinder  40  from position  47  to the position shown in FIG.  1 . This brings the insert  34  and insert  35  of active jaws  26  and  27 , respectively, snug against the outer surface of pipe  33  abutting reactive jaw  28 . Further pull by fluid cylinder  40  increases the forces applied (denoted as force F 1  on insert  34 , force F 4  on insert  35  and F 5  on insert  36 ) to the surface of pipe  33  to a force predetermined to be sufficient to hold the pipe from rotating. 
     If force F 1  (FIG. 1C) is known, then the force F 3  (FIG. 1D) on roller  43  where it contacts the angular cam section at point  49  can be determined. Force F 2  is determined by multiplying the tangent of the cam angle A times the force F 3 . Two times the force F 2  is used to determine the sizing of fluid cylinder  40 . 
     When resisting rotation of pipe  33 , any counterforce generated by the gripping force FT of inserts  34 ,  35  and  36  (FIG. 1C) against the pipe  33  is applied directly to rollers  43  and  44  and thus against the hard surfaces of force block  37  or inserts  38  and  39 . Compression of the fluid in cylinder  40  is thus minimized and a very rigid clamping arrangement is obtained. The length of insert  38  is sufficient to allow fluid cylinder  40  to force roller  43  in a clockwise direction around pivot pin  24  and roller  44  in a counterclockwise direction around pivot pin  25  with sufficient movement to allow for tolerances in pivot pins  24  and  25 , jaw pins  29  and  30 , and roller pins  50  and  51  and variations in the pipe  33  outside diameter and still maintain in constant force on roller  43  and  44 . The total gripping force applied when rollers  43 ,  44  are in contact with inserts  38 ,  39  is the sum of force F 1 , F 4  and F 5  (designated as force FRT in FIG.  1 C), Force FRT is the force required to overcome the tangential force (FT in FIG. 1C) by a grip factor (FRT÷FT) of about 1.2 to as much as 15 or more. The grip factor varies, of course, depending on insert gripping surface configuration and contact area of the active jaws  26 ,  27  and reactive jaw  28 . This configuration is predetermined to minimize damage to the pipe  33 . The tangential force FT in inch-pounds is determined by multiplying the applied torque from the power tong by twelve (12) and dividing that value by the outside radius of pipe  33 . This value is the force which must be overcome by the grip factor applied to radial force FRT. It will be appreciated that inserts  34 ,  35  and  36  may be different thickness to accommodate the outside diameter of various pipe sizes. Thus several pipe sizes may be handled by the backup tool by changing only the inserts without changing the jaws. The total radial force (FRT) is determined by calculation and is normally three to four times the tangential force (FT) but may be adjusted by trial and error. Rollers  43  and  44  are centered in pivot arms  22  and  23  by roller pins  50  and  51 . 
     Pipe  33  is an elongated cylindrical product such as a hollow joint, tubing, casing, solid bar, drill pipe or other tool used in well drilling, completion and servicing operations. While the tubular product illustrated in FIG. 1 is circular, it should be appreciated that the cross-section of the tubular product may be other than circular. If desired, a mechanical advantage can be realized to reduce the forces of the rollers  43  and  44  on the inserts  38  and  39 , respectively, by reducing the distance between jaw pins  29  and  30  and pivot pins  24  and  25 , respectively, or by increasing the distance between pivot pins  24  and  25  and roller pins  50  and  51 , respectively. 
     The space  52  (FIG. 1) between pivot arm  22  and active jaw  26  may be confined by surfaces  53  and  54 . This space is predetermined to limit the rotation of active jaw  26  with respect to pivot arm  22 . This applies as well to active jaw  27  and any other pivoted jaw arrangements, e.g., the embodiment of FIG.  7 . 
     The entire gripping system indexes on the outer surface of pipe  33 . The active jaws  26  and  27  are pushed against the pipe  33  by pivot arms  22  and  23  when actuated by rollers  43  and  44  moving on surfaces  45  and  46  and inserts  38  and  39  on force loading block  37 . In turn pipe  33  is forced into reactive jaw  28 . Should the pipe  33  be out of round or otherwise not aligned with the inserts  34 ,  35  and  36 , the force loading block  37  can move angularly compensate and assure an even gripping. Angular compensation is possible because the fluid cylinder  40  may pivot on pin  55  so that the force loading block  37  may move as required to assure alignment with pipe  33 . Active jaw  27 , reactive jaw  28  and inserts  35 ,  36  have keyways  56   a  and keys  56  similar to those in active jaw  26  and insert  34 . 
     In FIG. 2 the backup tool  10  is illustrated with the jaws open. Insert  34  is secured to active jaw  26  by a key  56  in a keyway  56   a.  With insert  34  installed, the torque forces are absorbed by the key  56 . Key  56  extends substantially through the length of insert  34  and is retained by bolt  56 A and washer  56 B as shown in FIG.  1 C. 
     FIG. 3 is a sectional view taken through pivot arm  22  and pivot pin  24 . The pivot pin  24  is seated in bushing  64  of pivot arm  22  and secured between upper plate  20  and lower plate  21  bearing on shoulder surfaces  69  and  70  which allows a clearance fit to pivot arm  22 . The pivot pin  24  is secured to the top plate  20  and the bottom plate  21  by retaining plates  65  and  66 . A plurality of bolts  67  secure plate  65  to top plate  20  and plate  66  to lower plate  21  and a plurality of bolts  68  securing upper plate  65  and lower plate  66  to pin  24 . The bore  71  through pin  24  is provided so that the spring supporting mechanism  300  for the bidirectional backup tool  10  (FIG. 1) to be attached to a power tong  310 . A bar  313  through bore  71  with a clearance fit extends through bidirectional backup tool  10 , and a compression spring  316  is secured to that bar by plates  314  and  315  adjusted and retained by nut  317  on threads  318 , so that the backup tool may deflect axially on the pipe as the threaded joints are coupled or decoupled. The top end of bar  313  is pivotally attached by pin  312  to adapter plate  311  welded to or made a part of power tong  310 . Two bars  313  and spring assemblies are used, one on each side of pipe  33 . The suspension system may be any conventional system. 
     FIG. 4 shows the insert  34  retained in the active jaw  26  by dove tail groove  26   a.  Surfaces  58  and  60  are designed to allow insert  34  to slide radially into the active jaw  26 . The surfaces  57  and  59  of insert  34  engage the surfaces  58  and  60 , respectively, to retain the insert  34  within active jaw  26 . Inserts similar to insert  34  are retained in active jaw  27  and reactive jaw  28 . All the inserts may be changed without removing the jaws. Active jaw  26  secured around jaw pin  29  and is retained by retainer rings  61  and  62 . Jaw pin  29  preferably has bushing  63 . Other mechanical means may be used to retain the inserts within jaws. 
     As shown in FIG. 5 roller  43  is secured by roller pin  50  and retained by retainer ring  50   a.  Roller  43  is mounted in a slot  73  in pivot arm  22 , and roller  43  has a clearance fit within the slot  73 . Roller  44  uses the same arrangement as shown in FIG.  5 . 
     Inserts  38 ,  39  may be changed so that different force angles A (FIG. 1D) may be utilized to either increase or decrease force on the pipe  33 . Optionally, load block  37  may have a projections  75  which slide in grooves  74  along the centerline of pipe  33  to provide additional control of load block  37  during the stroke of fluid cylinder  40 . Although not necessary, load block  37  may have projection  75  on the top or bottom, or both top and bottom. Projection  75  would then have corresponding grooves  74 . Inserts  38  and  39  of load block  37  have a clearance sliding fit between top plate  20  and lower plate  21 . 
     Referring back to FIG. 2, it will be noted that jaw assembly  19  (which is a reactive jaw) may be used in all three gripping jaws; one to pivot arm  22 , one to pivot arm  23 , and one in the throat  19   a  attached to top and bottom plates  20  and  21  as shown in FIG.  2 . This arrangement would be used where equal gripping on the pipe  33  is not an absolute requirement. Any combination of jaw assemblies  14 ,  15 ,  16 ,  17 ,  18 ,  19  or  20 A may be used on any backup tool or power tong. 
     Backup tool  11  shown in FIG. 7 is a modification of backup tool  10 . In backup tool  11  pivot arm  22  and pivot arm  23  are actuated by movement of rollers  43  and  44  in a different manner than backup tool  10 . For example, backup tool  11  has a fluid motor  76  which is used to push force loading block  86  from position  85  toward the pipe and to pull force loading block  37  from position  86   a  away from the pipe  33 . Fluid motor  76  is attached to force loading block  37  using an adapter  95 . The spline  77  of fluid motor  76  engages drive shaft  78  which contains a buttress or acme-type thread  79  engaging threads  94  within the threaded bore  86  toward the pipe  33  so that roller  43  is pushed into engagement position along ramp  88  until roller  43  contacts force block  86  at position  89 . When roller  43  touches force block  86  at position  89 , force block  86  engages and pushes crosshead  93  along surface  91 . Crosshead  93  supports active jaw  99  or other jaw assemblies described herein which is pushed by force block  86  into pipe  33 , forcing pipe  33  into reactive jaws  97  and jaw  98 . The force exerted by threads  79  and the force block  86  against crosshead  93  is predetermined and sufficient to hold the pipe  33  from rotation. When force block  86  is pushed against crosshead  93 , the reactive force through thread  79  is taken by thrust roller bearing  82  which is force against boss  96  on shaft  79 . 
     Top plate  20  is not shown in FIG. 7 for ease of illustration. Body members  92  and  92 A are positioned between top plate  20  and lower plate  21  as an integral part thereof. Crosshead  93  slidingly fits between body or frame members  92  and  92 A. 
     Drive shaft  78  is contained in body or frame member  84 . The fluid motor adapter  95  contains grease seal  81  and a zerk fitting (not shown) is used to inject grease into bearings  82  and  83 . 
     In FIG. 7 the force block  86  is shown in the gripping position  86  and has moved up from position  85  into the actuated gripping position  86   a.  Force block  86  could be actuated by a fluid cylinder pushing force block  86  back and forth rather than the fluid motor  76 . 
     FIG. 8 shows an alternate structure for causing arms  22  and  23  to pivot outward and force engagement of the active jaws  26  and  27  on the pipe  33 . The tool illustrated in FIG. 8 uses a toggle arrangement  12  wherein a traveler toggle block  106  is shown in the retracted position and in the load position  110  (dotted lines). Toggle link  107  is connected at one end to toggle block  106  by pin  108  and connected to pivot arm  22  by pin  109 . Toggle link  107  is shown in the retracted position and as in the actuated gripping position  112  (dotted lines). Toggle block  106  in conjunction with toggle link  107  comprise a toggle joint. 
     Full gripping force is applied by virtue of force F 5  which may be applied by a screw thread as in FIG. 7 or by a fluid cylinder which pushes or pulls it from left to right as in FIG.  1 . When toggle block is pulled to the right it is stopped by frame members  114  and  115 . Frame members  114 ,  115  are permanently attached to the top and bottom plates  20  and  21  with toggle  107   a  forming angle B which is anywhere from one (1) to perhaps fifteen (15) degrees. After force F 4  is determined in the same manner as force F 3  in FIG. 1D, then force F 5  (which is the force required to be applied to shaft  113  by the fluid motor or fluid cylinder  76 ) is determined by multiplying the tangent of angle B times the force F 4  times two. The fluid cylinder size of fluid motor screw arrangement, if used, can then be determined. 
     The combination of the toggle block  106  and toggle links  107  also constitutes a force multiplying device. The force applied by the jaws to pipe  33  is substantially greater than the force to pull toggle block to gripping position. 
     FIG. 9 illustrates a modification of backup tool  10  wherein load block  130 , which is similar to load block  37 , is actuated by fluid motor  117  which pulls load block  130  to actuate pivot arms  22  and  23 . The forces involved in pulling the load block  130  to put the desired force against rollers  43  and  44  is calculated the same as disclosed in connection with backup tool  10  (FIG.  1 ). Fluid motor  117  is attached to adapter  118  which contains roller bearing  122  and grease seal  124 . The flange  121  on shaft  119  bears against thrust bearing  120 . Grease is retained by grease seal  123  and zerk fittings (not shown) are provided to grease bearing  120 . The threaded portion  128  of shaft  119  is buttress-type or acme-type thread. 
     Fluid motor  117  turns threaded portion  128  of shaft  119  in mating thread  129  inside load block  130  to pull load  130  into the actuated position. The other end of shaft  119  contains a bearing  125 , a retainer ring  126  and a grease seal  127  with means (not shown) to grease the bearing. This is housed within a portion of the body  9  of the backup tool  10  which connects top plate  20  and bottom plate  21  as described in connection with FIG.  1 . Backup tool  13  may use any of the jaw configurations backup tool  10  would use. 
     FIG. 10 shows a jaw assembly  14  which contains a jaw base  131  bolted to pivot arm  22  by bolt  132 . Dowel  133  is pressed into jaw base  131  and loosely fits into hole  140  in jaw segments  130 . The loose fit of dowel  133  in hole  140  allows jaw segment  130  to roll slightly either on a flat face of jaw base  131  or on a curvature slightly larger than the outside radius of jaw segment  130 . This allows some small alignment with pipe  33  outside diameter to make up for irregularly shaped cross section on pipe  33 . Insert  34  is retained within jaw segment  130  by mechanical means. One arrangement of jaw assembly  14  which may be used is shown in FIG.  10 . Jaw segment  130  is loosely retained by clip  134  which fits over the projection  136  from jaw segment  130  and projection  137  from jaw base  131  and is secured by bolts  135 . Being loosely retained, jaw segment  130  may rotate slightly on surfaces  139  or  138  (FIG.  9 ). This arrangement secures jaw segment  130  top and bottom. 
     FIG. 11 shows a jaw assembly  15  which is designed not only to adjust to the pipe outer surface, but also to align itself axially with the pipe  33 . In jaw assembly  15  the jaw base  143   a  is rotatably associated with jaw segment  141  by steel ball  142  which is contained within hemispherical recess  146  in jaw segment  141  and hemispherical recess  147  within jaw base  143 . It is necessary in machining hemispherical recesses to have relief hole  144  and relief hole  145 . Here again, jaw segment  141  is retained in the same manner as jaw assembly  14  in FIG.  10 . Ball  142  bears both radial and torque loads. Means for applying lubricant to ball  142  are provided (not shown). In some cases, it may be desired that ball  142  be permanently secured to either jaw segment  141  or jaw base  143  so that the wear is only on one part. 
     FIGS. 12 and 13 show jaw assembly  16 . Assembly  16  provides radial alignment with irregular pipe shapes by virtue of jaw segment  148  rocking on flat surface  154  or concave surface  155  which is slightly larger than outside radius of jaw segment  148 . The jaw segment  148  is loosely retained radially by clip  150  which overlaps the lug  151  on jaw segment  148 . Torque loads are retained in one direction by projection  152  on jaw base  149  and in the opposite direction by projection  153  in jaw base  149 . These engage lug  151  which is attached to jaw segment  148 . Jaw base  149  is connected to pivot arm  22  in the same manner as shown in FIGS. 10 and 11. The retaining means would be on the top and bottom of jaw segment  148 . 
     FIGS. 14 and 15 show a jaw assembly  17 . Jaw segment  156  is rotatably mounted to jaw base  157  by a cylindrical dowel  158  which fits into semi-cylindrical groove  163  in the jaw segment  156  and semi-cylindrical groove  164  in jaw base  157 . This allows radial movement to align with pipe  33  during the gripping process. Jaw segment  156  is loosely retained by clips  162  which fit over projection  160  from jaw segment  156  and projection  161  from jaw base  157 . Clips  162  are held in place by bolts  135 . The dowel pin  158  absorbs both compressive loads and torque sheer loads developed by the gripping system. Lubrication means (not shown) is provided to dowel pin  158 . 
     FIG. 16 illustrates a jaw assembly  500  which will work for both open and closed throat power tong gripping systems. This assembly includes a drive gear  527  driven by roller chain or gear teeth with bearings  770  between drive gear  527  and a suitable conventional housing  771  driven by one or two fluid motors (not shown) as described in U.S. Pat. No. 5,172,613. 
     Drag ring  528  rotates concentric with drive gear  527 . Drag ring  528  provides resistance in both rotary directions. 
     Cam roller  531  rolls along cam surface  535  when drive gear  527  is rotated clockwise to bring jaw  533  to pipe  536 . Replaceable friction inserts  534  lie between pipe  536  and jaw  533  to handle different pipe sizes. Likewise, cam roller  531  rolls along cam surface  543  when driven in the opposite direction. 
     The jaw  533  and insert  534  are the same arrangement as jaw assembly  18  in FIGS. 2 and 4 and pivot about pin  532 . Jaw link  530  and  530 A (on far side of drag ring  528 ) and cam roller  531  also pivot on jaw pin  532 . The opposite ends of jaw links  530  and  530 A pivot on pin  529  near side and  529 A far side of drag ring  528 . Leg  544  on either or both jaw links  530  and  530 A operate with spring  545  to urge jaw assembly  500  to a retracted position where cam roller  531  is urged into recess  546 . Recess  546  may be of irregular shape to accommodate cam roller  531  in the retracted position. 
     In designing the cam geometry shown in FIG. 16 for proper grip on pipe  536  the following steps are followed: 
     First: As shown in FIG. 16B the total gripping force FRT is determined by taking the smallest pipe diameter  536  to be torqued. Pipe tangential force FTP is calculated as the maximum torque selected divided by the radius  542  of pipe  536 . 
     Second: A gripping factor between 1.2 and 15 is selected which will not allow the jaw assemblies to slip on the pipe under torque loads. For example, a grip factor of four works well on 2⅜ inch O.D. pipe for a selected torque 5,000 foot pounds with proper tooth pattern (explained later). This means that FTP times 4 equals FRT the total radial force required in this case to grip the pipe. (Grip factor is FRT÷FTP). 
     Third: A torque force factor FT is calculated as the selected torque in inch pounds divided by the distance from the point cam roller  531  touches cam surface  535  to center point  540 . 
     Fourth: To find force angle C, the tangent of FT divided by FRT gives the force angle C. in degrees. This angle will be between 1 degree and 15 degrees. Usually a force angle C. of 4 to 6 degrees works well depending on pipe size, selected torque and tooth pattern. 
     Fifth: To design a cam surface L 1  with a selected force angle C., construct a right triangle where the hypotenuse equals L 1  and the side opposite angle C. is designated H 2 . Solving this triangle, force angle C=sine (H 2 /L 1 ). 
     Sixth: Divide FRT by the number of cam surfaces to determine the radial force FR for each jaw assembly. These are called “active jaws”. 
     The optimum number of cam surfaces and jaw assemblies is three, although this quantity may vary. 
     Jaws which do not apply gripping force from cam surfaces are called “reactive jaws.” Any combination of active jaws and reactive jaws may be utilized. 
     In FIG. 16 a rigid jaw where the jaw links are integral with the jaw (not shown) may be used where a pivoted jaw is not wanted. This rigid jaw would have replaceable inserts  534  also. 
     FIG. 16A shows a drive gear  527  with three cam surfaces  551 ,  552  and  553  as described in FIG.  16 . This drive gear allows three active jaw assemblies  500  and an open face tong where pipe is inserted from the side through opening  548 . This opening  548  does not exist in a closed face tong where pipe is inserted axially through the cam ring. (Drag ring  528  not shown). 
     When drive gear  527  is rotated in either direction all jaw assemblies  500  are brought to the pipe simultaneously and the drive gear  527  applies radial force to the pipe. Spring  545  returns jaws assemblies  500  to the retracted position when opening  548  and drag ring  527  are aligned to receive the pipe  536  through opening  548 . 
     Angles  549  and  550  to center line of each cam surface each maybe from zero degrees to 55 degrees depending on clearance within the tong to receive pipe  536 . 15 degrees to 35 degrees works best in most cases. 
     Jaw assemblies  500  and cam surfaces  551  and  552  may be active jaws and the throat jaw in cam position  553  may be a reactive jaw. Drag ring  528  may be restrained by conventional brake bands or hydraulic drag means as described in U.S. Pat. No. 5,172,613. 
     FIGS. 17,  17 A,  17 B and  18  illustrate a backup tool  22 A which is capable of gripping many sizes of pipe between tubular  166  and tubular  165  (illustrated in broken lines). Backup tool  22 A has a unique gripping system comprising jaw assembly  20 A which provides a gripping force in proportion to the applied torque to tubular  166  and intermediate diameters up to tubular  165 . Backup tool  22 A has a frame or body  171  with a projection arm  174  which is supported from the tong bracket or support  175  and arm  174  has a shaft  177  on which roller  176  rotates. The shaft  177  has a flange  178  which retains roller  176  on shaft  177 . 
     Once installed, the backup tool  22 A grips in one direction. Accordingly, to permit backup tool to grip in the opposite direction, the backup tool  22 A is pulled away from support  175  so that roller  176  on shaft  177  seats in support  175 . Backup tool  22 A is then rotated 180° and pushed back into the support  175  for gripping in the opposite direction. Flange  178  keeps the tool from being pulled completely through support  175 . It will be appreciated by those skilled in the art that any type of support from the power tong can be utilized so long as arm  174  may be held in one position and move 180° to the opposite direction. 
     Jaw assembly  20 A has jaw member  167  attached by pivot pin  168  to pivot cranks or arms  169  and  169   a.  Jaw assembly  20 A is actuated by pivot arms  169  and  169   a  between pivot pin  168  in the jaw member  167  and pivot  170  in the frame or body  171 . Pivot arms extend out to pin  210  and  210   c  which are, respectively, at one end of fluid cylinder  173  on top and fluid cylinder  173 A on bottom. The opposite ends of cylinders  173  and  173 A are attached to body  171  to pins  210   a  and  210   b.  Sometimes only one fluid cylinder may be sufficient. In FIG. 17B, jaw assembly  20 A is shown in the retracted position  180  and the retracted position of pin  210  is shown as  179 . When jaw assembly  20 A is retracted as shown by position  180  and pin  179 , fluid cylinders  173  and  173 A are pulled to position illustrated in FIG.  17 B. This allows one of the pipe sizes from tubular  166  to tubular  165  access to the throat  23 A of the backup tool  22 A. 
     In operation, tubular  166  or tubular  165 , or any size in between, is placed in throat  23 A as shown in FIGS. 17 and 17A. The jaw segment  209  is rotatably mounted in the jaw support  188 . The radius of jaw segment  209  to jaw support  188  is equal to or less than the radius of the smallest diameter pipe to be used as with a larger radius it would tend to slip with the smaller size of pipe. To set the backup tool  22 A for operation, the jaw support or pivot arms or cranks  169  and  169   a  are positioned approximately as shown in FIG. 17 and a dowel pin  172   a  is dropped into hole  172  at the point where the cylinders  173  and  174 A push pivot arms  169  and  169   a  into engagement with dowel pin  172   a.  Angle  208  is predetermined such that when the preload of cylinders  173  and  173   a  are placed on pivot arms  169  and  169   a,  respectively, and it has been found that angle  208  may be between 2 and 25 degrees and preferably between 10 and 15 degrees and pivot arms  169  and  169   a  are forced to rotate around pin  170  counterclockwise and restrained by pin  172   a.    
     Acme or buttress threaded shaft  200  is turned by crank  201  in the threaded portion  211  of body  171  which rotates shaft extension  203  retained by pin  204  in the groove shown with the jaw base  188 . The load between the threaded shaft  200  and the jaw base  188  bears on surface  207 . Crank  201  is turned, translating jaw base  188  towards jaw member  167  until the proper size pipe is snug between large inserts  190  and  193  or small inserts  191  and  192  in jaw segment  209  and large inserts  181  or  184  or small inserts  182  and  183  in jaw member  167 , respectively. 
     When either the large or small inserts are firmly compressed against the pipe  166 ,  165  or the size in between, the lock nut  202  is secured on shaft  200  abutting body  171  so that the position is maintained. At this point, fluid cylinders  173  and  173   a  are retracted, releasing pin  172   a  so that the pivot arms  169  and  169   a  and jaw assembly  20 A are fully operational. Angle  208  on pivot arm  169  is determined to provide the proper preload since the cylinders  173  and  173   a  do not provide the fill gripping force but only preload. As the pipe tends to rotate clockwise with the applied torque from the power tong near and above the backup tool  22 A, pivot arm  169  tends to rotate counterclockwise reducing angle  208  which increases the force of jaw member  167  on the pipe begin gripped. To eliminate over-travel, surface  224  of jaw member  167  is designed to stop against surface  225  on the body  171  where angle  208  approaches zero degrees. 
     Jaw assembly  20 A as shown has four inserts  181 ,  182 ,  183  and  184  for gripping the pipe and jaw assembly  21 A as shown has four inserts  190 ,  191 ,  192  and  193  for gripping the pipe. Each of these inserts is cylindrical on the portion away from the pipe and has teeth on the portion engaging the pipe. For gripping several small sizes of pipe, inserts  182 ,  183 ,  191  and  192  are engaged (see FIG.  17 A). For gripping larger sizes of pipe inserts  181  and  184  are utilized as well as inserts  190  and  193 . The radii to the tips of the teeth of inserts  182 ,  183 ,  191  and  192  are approximately the same as the outside radius of the smallest tubing to be gripped within the small size range. The radii to the tips of the teeth of inserts  181 ,  184  and  190  and  193  conform to the smallest pipe to be gripped within the large size range. 
     Cylindrical gripping inserts  181 ,  182 ,  183  and  184  are retained by a plate  185  secured by bolts  186  and  187  to jaw member  167 . Likewise, cylindrical gripping inserts  190 ,  191 ,  192  and  193  are retained by plate  194  secured by bolts  195  and  196  which bear against the jaw base  188  on each side of the two flat sides of threaded screw  206 . 
     Referring to FIG. 18, the jaw segment  209  is retained within the jaw base  188  by top and bottom projections  194 A from cap  194  which extends into a groove  194 B in jaw base  188  loosely fitting to retain jaw segment  209  in operational integrity with the jaw base  188 . 
     FIG. 19 shows generally cylindrical gripping die  181  with teeth  254  and a cylindrical body  181   a  which fits into cylindrical surface  258 . This arrangement is illustrative of the dies in jaws  167  and  209 . The dies are relatively loose fit because of the corrosion involved in the operation of power tongs and backup tools. Threaded portion  256  (one or more holes in cylindrical die  181 ) is placed over a roll pin  257  to limit rotation. The teeth  254  are in the shape of an arc  255 , equivalent to the smallest diameter pipe O.D. to be gripped by this particular die. The teeth match the smallest diameter so that when larger diameters are used in the same die, the points which touch the pipe outside diameter are shown as teeth  259  and  260 . This prevents the tendency for pipe  165  to roll out of the cylindrical die  181 . Threaded portion  256  serves as a means of holding the cylindrical die  181  in a fixture of machining the teeth  254 . Referring to FIG. 18, cylindrical die  181 , as well as the plurality of cylindrical dies, is held in position by cylindrical boss  261  at each end of die  181  concentric with the diameter of die  181  and the other cylindrical dies. These two bosses  261  fit in loosely fitted holds  264  in top and bottom plates  185  if both are used. This is the same to hold all the cylindrical dies in jaw  167  and jaw  209 . Roll pins  257  are embedded in jaw  167  to limit movement of the cylindrical dies  181 ,  182 ,  183  and  184 . Roll pin  257  will hit either side of tapped hole  256  so that the pivoting of the cylindrical dies with the controlled. This is the same arrangement for all dies in jaw  209 . 
     An alternate jaw  25 A is shown in FIG.  20 . Jaw  212  has four flat surface recesses  220  in which arcuate backs of inserts  218 ,  215 ,  216 , and  219  rock on the flat surface of recesses  220  to assure alignment with different pipe diameters. The operation of jaw assembly  25 A is the same as assembly  20 A. Any combination of cylindrical tooth dies and flat tooth dies may be utilized as desired. The pivot arm  169  is shown on the near side of body  171  and the far side at arm  169   a  is connected by pin  170 . Likewise, pin  168  through jaw  167  is through both pivot arms  169  and  169   a.    
     As best seen in FIG. 20 inserts  215 ,  216 ,  218  and  219  are loosely retained within recesses  200  by dovetail bevels  222 ,  223  by plates  185  and  194  as seen in FIG.  17 . Pivot arms  169  and  169   a  would attach to pin  213  similar to the arrangement in jaw assembly  20 A. 
     Another embodiment of backup tool is illustrated in FIGS. 21,  22  and  23 . Bidirectional backup tool  10 A comprises a frame or body  9  formed by spaced top and bottom plates  20  and  21 . Pivot arms  22  and  23  are pivotally secured to the body  9  by pivot pins  24  and  25 , respectively. The above description in connection with FIG. 3 applies to the manner in which the pivoting pins are attached to top plate  20  and lower plate  21  and to pivot arms  22  and  23 . Active jaws  26 ,  27  and reactive jaw  28  are positioned within the bidirectional backup tool  10 A with active pivoted jaw  26  attached to pivot arm  22 A by jaw pin  29 . Active pivoted jaw  27  is attached to pivot arm  23 A by jaw pin  30 . The rest of assembly  10 A is the same as assembly  10  except FIGS. 5 and 6 would not apply. Assembly  10 A could also be actuated by fluid motor per assembly  11 . 
     The embodiment of FIGS. 21 and 22 comprises a force roller assembly  400  with replaceable rollers  401  and  402  which engage inclined or arcuate cam surfaces  404  and  403  on arms  22 A and  23 A which establishes a cam-like or ramp face. By actuating fluid cylinder  50  (the rod of which is threaded into roller assembly  400 ), roller assembly  400  is pulled to the right, causing the pivot arms  22 A and  23 A to pivot around the pivot pins  24  and  25  so that active pivoted jaws  26  and  27  of pivot arms  22 A and  23 A are moved into engagement with pipe  33 . Initially, hardened rollers  401  and  402  of roller assembly  400  engage hardened cam surfaces  403  and  404  of pivot arms  22 A and  23 A which moves active jaws  26  and  27 , respectively, snugly against pipe  33 . Then cam surfaces  403  and  404  engage rollers  402  and  401  and pivot arms  22 A and  23 A rotate about pivot pins  24  and  25 . Cam surfaces  403  and  404  may be replaceable hardened inserts attached to arms  22 A and  23 A. 
     The embodiment of FIGS. 21,  22  and  23  may be actuated as described for FIGS. 7 and 9. The pivoting arms  22 A and  23 A applies force through active jaws  26  and  27  against the pipe  33  abutting reactive jaw  28  in proportion to the amount of force applied by fluid cylinder  40 . To release the pipe  33 , roller assembly  400  is pushed by fluid cylinder  40  to the left into the retracted position  47 . By an extension spring  48  attached to pivot arms  22 A and  23 A, rollers  401  and  402  are biased to engage surface  404  and  403 . This enables the pivot arms  22 A and  23 A to work active jaws  26   27  in and out of engagement with pipe  33  abutting reactive jaw  28 . All other aspects of FIGS. 21 and 22 are same as FIGS. 1,  1 A,  1 B, and  1 C. 
     The combination of the rollers  401  and  402  and arcuate cam surfaces  403  and  404  also comprise a force multiplying device. Once again, this is because the force applied to pipe  33  is substantially greater than the force required to pull the rollers along the arcuate cam surfaces into a gripping position. 
     FIG. 23 is a schematic drawing showing the curved cam  403  and arm  22 A which pivots about pin  24 . The required torque  412  is determined from the predetermined gripping force F 1  on jaw  26  multiplied by the distance from jaw pin  29  and arm pivot  24 . 
     Arm  22 A position  410  with roller position  402  a distance  405  from pin  24  is the position with pipe  33  at its largest acceptable diameter. Arm  22 A position  412  with roller portion  402 A a distance  406  from pin  24  is the position with pipe  33  at its smallest acceptable diameter. 
     To convert actuator  40  or  76  pull force  409  to torque  412 , force  410  in roller position  402  is determined by dividing torque (in lbs) by distance  405 . Since we now know force  409  and force  410  we can determine angle  407 , the tangent of which equals force  409  divided by force  410 . 
     This procedure is done for several increments of distance between distance  405  and  406 . The served calculated angels between angle  407  and  408  can be plotted to determine the curved cam surface  403  which will provide the same force F 1  on jaw  26  regardless of position of roller  402  between distance  405  and  406 . This is true of the cam surface  404  on arm  23 A and cam roller  401 . 
     It is important that due to large stresses created between rollers  401  and  402  on cam surfaces  403  and  404  these components should be a steel heat treated to Rockwell 15 to 76 on the “C.” scale. Rockwell C-37 to C64 is an acceptable hardness range. 
     Although the invention has been described in conjunction with specific forms thereof, many alternatives, modifications and variations will be apparent to those skilled in the art in light of the foregoing disclosure. Accordingly, this description is to be construed as illustrative only and is for the purpose of teaching those skilled in the art the manner of carrying out the invention. It is to be understood that the forms of the invention herewith shown and described are to be taken as the presently preferred embodiments. Various changes may be made in the shape, size and arrangement of parts. For example, equivalent elements or materials may be substituted for those illustrated and describe herein, parts may be reversed, and certain features of the invention may be utilized independently of the use of the other features, all as would be apparent to one skilled in the art after having the benefit of this description of the invention.