Abstract:
A power apparatus and method for making and breaking joints in drill pipe strings in oil wells, in which a single torquing cylinder, that always moves in a single direction while torquing, both makes and breaks the joints. Three levels of jaw elements are employed, the top and bottom jaw levels being identical to each other, all jaw elements being interconnected as by a frame. Other cylinders close the jaws at each level. The apparatus is moved vertically; two levels of jaw elements are employed for making and another combination of two levels is employed for breaking. Special die and cam means are provided to grip the drill pipe. Means are provided to position the jaws in the middle level at the proper location after each use, for different sizes of pipe. Special bearing, pivot and adjustment means are provided in the jaw elements. The jaw elements operate in only one direction, and are self energizing.

Description:
BACKGROUND OF THE INVENTION 
     For making and breaking joints in strings of drill pipe in an oil well, etc., it is still common to employ manually-operated rig tongs, which are large and bulky and difficult to operate and which cannot easily provide controlled torque values. Such rig tongs are dangerous to use, being normally operated by a cable and winch. They are raised and lowered by hand. 
     Where hydraulic tongs have been employed in making and breaking joints in drill pipe strings, they have been excessively heavy, bulky, complex, expensive, or otherwise unsatisfactory in various regards. 
     SUMMARY OF THE INVENTION 
     Three levels of jaws are provided, the jaws in each level being of a type that energize when turned in a predetermined direction so as to have a stronger grip on the pipe when turned in such direction. The jaws in two levels are oriented so as to turn the pipe in one direction, while the jaws on the remaining level are oriented to turn the pipe in the opposite direction. The jaws in the three levels are associated with each other as by a common frame. 
     Fluid-operated means are provided to close the jaws prior to commencement of torquing, so that subsequent torquing will operate effectively to increase the amount of gripping and without sliding of the jaws off the joints in the string of drill pipe. Other fluid-operated means, connected to the frame, are provided to effect the torquing In the preferred embodiment, the last-mentioned fluid-operated means is a single hydraulic cylinder that operates in the same direction for both making and breaking of a joint. 
     The apparatus is self-contained, and is preferably suspended rotatably at a wellhead. 
     Combination die and cam means are provided, and operate automatically in response to positioning of the apparatus on a drill pipe string, and to removal of the apparatus from such string. The die portions are so shaped and pivotally mounted as to properly grip the tool joint in response to both initial die closing and subsequent die energization, the latter being the result of torquing. 
     Means are provided to adapt the apparatus for operation relative to tool joints having a variety of diameters. Such means includes not only adjustable stops, but also means correlated with the stops to determine the position of the jaws, at one of the levels thereof, at the beginning of each operation. Bearing, pivot and adjustment means adapt each set of jaw for different joint diameters, without need for removing or replacing any parts. 
     In accordance with the method, three levels of jaws are provided, the jaws in each level being adapted to rotate a tool joint portion in only a single direction. The method is such that the apparatus is not turned over but is instead only raised and lowered so as to orient different combinations of jaws adjacent the tool joint. Then, the method is such that only two levels of jaws operate on the tool joint to make it or break it. 
     In a preferred embodiment of the method, making of a joint is effected by locking the middle jaws on the bottom portion of a tool joint, and employing the top and middle jaws to turn the top portion of the tool joint clockwise. Breaking of a joint is, in accordance with such preferred embodiment, effected by locking the bottom jaws on the bottom tool joint portion, and employing the middle and bottom levels of jaws to rotate the top portion of the tool joint counterclockwise. 
     FIG. 1 is an isometric view of one side of the present apparatus; 
     FIG. 2 is an isometric view of another side of the present apparatus; 
     FIG. 3 is an isometric view illustrating the three levels of jaws, and associated cylinder and adjustment means, the jaws being shown in closed positions but the pipe being unshown for purposes of clarity; 
     FIG. 4 shows major portions of the apparatus, as viewed from above the top level of jaws, showing in solid lines the positions of parts before making of the joint, and showing in phantom lines the position of parts after making of the joint; 
     FIG. 5 is a view of the same general type as FIG. 4, but taken one level down from that of FIG. 4, namely at a region just above the central level. The parts are shown in solid lines in the positions they have prior to breaking of a joint; they are shown in phantom lines in the positions that they have after such breaking; 
     FIG. 6 is a fragmentary top plan view of one set of die and cam combinations, as related to a portion of a tool joint, the jaws being shown in open condition; 
     FIG. 7 is an exploded isometric view of one die and cam combination; 
     FIG. 8 is a view, partly in horizontal section, illustrating the components of one of the jaws, the jaws being shown closed on a tool joint; 
     FIG. 9 is vertical sectional view on line 9--9 of FIG. 8; 
     FIG. 10 is a schematic view illustrating the conditions of the jaws during making of a joint, the top and middle levels of jaws being closed; 
     FIG. 11 is a schematic view showing the conditions of the jaws during breaking of a tool joint, the middle and bottom levels of jaws being closed; and 
     FIG. 12 is an exploded view showing isometrically the high-strength bearing, pivot and adjustment mechanism for each jaw. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     For convenience, all uses of the words &#34;clockwise&#34; and &#34;counterclockwise&#34; in the present application mean as viewed from above. 
     Referring to FIGS. 1-7, inclusive, the apparatus is illustrated to comprise a strong welded frame 10 having legs 11, the latter being to support the apparatus when not in use. Normally and preferably, when the apparatus is in use it is suspended at the wellhead of an oil well. Suspension is effected by a three-element suspension means 12 that connects at its lower ends to suitable points on frame 10, and that connects at its upper end to an adjustment cylinder 13 carried by a cable-supported hook 14 (FIG. 2). 
     The suspension means 12 is normally so adjusted that the below-described jaw sets lie in horizontal planes, and at a height determined by the adjustment cylinder 13 (for a given positioning of the hook 14). Tilting of the apparatus may be effected by operation of a tilt cylinder 15 that forms one of the three elements of suspension means 12. The other two elements include turnbuckles for leveling purposes. 
     Preferably, the various cylinders 13, 15 and others are hydraulically operated. This is done by means of a source 16 of hydraulic fluid pressure, by various hydraulic lines (not shown), and by controls 17 and 18 (FIG. 1), the controls being associated with control elements that are included in element 16. A gauge 19 indicates the hydraulic fluid pressure. 
     Referring next to FIGS. 2 and 3, particularly the latter, a strong vertical portion of frame 10 is denoted 10a. Mounted in vertically-spaced relationship on frame portion 10a are three sets of jaws. The top set of jaws is numbered 21; the middle set is numbered 22; and the bottom set is numbered 23. In the preferred embodiment, the top and bottom jaws 21, 23 are identical to each other and are oriented identically to each other--the bottom set of jaws being directly below the top set of jaws. The top and bottom jaws being oriented identically, they are adapted to turn a tool joint portion in the same direction. 
     The middle set of jaws, number 22, is reverse oriented relative to the top and bottom sets, being adapted to turn the tool joint portion in the opposite direction. The middle set of jaws is in vertical alignment with the top and bottom sets, at the regions of the middle set that are adjacent the tool joint. 
     In the preferred embodiment, top and bottom jaw sets 21, 23 are fixedly secured to frame portion 10a. Conversely, middle jaw sets 20 is not fixedly associated with frame portion 10a, being instead pivotally related to such frame component so that the middle jaw set 22 may pivot horizontally relative to the frame. The axis of such pivotal motion is caused to be at the axis of rotation of the jaws 22, 23. 
     Also in the preferred embodiment, the pivotal mounting of the middle jaw set 22 on frame portion 10a is not direct but instead through a torquing cylinder 24. Stated more definitely, and referring to FIGS. 2 and 3, the cylinder (body) portion of torquing cylinder 24 is strongly pivotally associated with frame component 10a by pivot means shown at 25, the axis of such pivot means being vertical. The pivot means 25 comprises top and bottom pivot pins 26 that extend downwardly and upwardly through strong horizontal flange portions 27 of frame portion 10a. Such flange portions 27 are immediately above and below the cylindrical body of torquing cylinder 24. As shown in FIG. 5, the pins 26 are sufficiently far from the vertical elements of frame portion 10a that the torquing cylinder may pivot to substantial angles relative to such frame portion. 
     A second strong pivot means 28 is provided, as shown in FIGS. 2 and 3, this being connected to the end of the piston rod 29 of torquing cylinder 24 (the rod being shown in phantom lines in FIGS. 4 and 5). To cooperate with torquing cylinder 24 in holding the middle jaw set 22 in a horizontal plane, the frame 10 includes upper and lower horizontal frame components 10b, 10c and which define a horizontal slot 33 as shown in FIG. 2. A region of the middle set 22 of jaws is disposed slidably in slot 33, sandwiched between upper and lower frame components 10b, 10c, so that the middle jaw set may move horizontally relative to the frame, while remaining in a plane parallel to those of the top and bottom jaw sets 21, 23. 
     There will next be described the top and bottom jaw sets 21, 23. Since (in the preferred embodiment) these jaw sets are identical to each other and are identically oriented, only the top set 21 will be described. The bottom set 23 is given the same reference numbers as those of the top set. 
     Top jaw set 21 (and thus the identical bottom jaw set 23) will first be described generally, as will the middle jaw set 22. Thereafter, the method will be generally described, following which additional major aspects of the jaw sets and method will be described. 
     The top jaw set 21 has a head 36 in which is pivotally mounted, for pivotal movement about a vertical axis, a hook 37. Head 36 is fixedly connected to the upper end of frame portion 10a (FIG. 3). The relationships are such that when the tool joint is initially gripped by the head 36 and hook 37, rotation of the head 36 in a clockwise direction will cause additional energization of the jaws 21 to thereby strongly and effectively grip the tool joint for torquing thereof. 
     Stated more definitely, and with particular reference to FIGS. 3, 7, 8 and 9, head 36 has strong plate elements 38 and 39 that are spaced apart so as to receive the shank 41 of hook 21 between them. Elements 38 and 39 are strongly secured to each other by top and bottom head plates 42, 43, these being held in position by bolts 44. 
     Element 38 of the head is strongly connected by struts 46 to the upper end of frame portion 10a (FIGS. 3 and 8). These connections, and all others where bolts or screws are not described, are made by strong welds (not shown). 
     The shank 41 of hook 37 is flat on the top and bottom sides thereof, the upper and lower surfaces of the shank lying in horizontal planes (FIG. 3) and close to 42, 43. The sides of the shank 41, at the portion thereof remote from the hook end 47 (FIG. 8), are portions of the same cylinder and are strongly threaded as indicated at 48. 
     A large diameter, strong nut 50 is threaded onto the threads 48 of shank 41. It has radial handles H to facilitate turning. Nut 50 is not only associated with threads 48 but with a combination pivot and adjustment mechanism 51 described in detail below. The relationships are such that rotation of the nut 50 causes the jaws to open or close to the desired position relative to a particular diameter of tool joint. Furthermore, the mechanism 51 is such that the hook 37 pivots about a predetermined vertical axis relative to head 36. 
     The indicated pivoting of hook 37 relative to head 36 is effected in two ways. Initially, the pivoting is effected by a bite cylinder 52, which is first operated to close the hook 37 on the tool joint so that teeth portions of dies (described below) bite initially on the tool joint. Thereafter, when the head 36 is turned clockwise, due to the connection of struts 46 to frame component 10a as subsequently described, the hook 37 closes further on the tool joint to powerfully grip it for effective making of the tool joint. 
     As shown in FIG. 3, the base end of the body of bite cylinder 52 is connected to a bracket 52b on a strut 46. The piston rod of cylinder 52 (FIGS. 3 and 8) is connected to a U-shaped element 53 the ends of which extend slidably into top and bottom elongate grooves 54 in hook 37. Such grooves 54 are substantially parallel to the shank 41 of such hook. Cylinder 52 and grooves 54 are so oriented as to permit the bite cylinder to effectively pivot hook 37 to desired open or closed positions, without causing binding. 
     The hook end 47 of hook 37 extends away from frame portion 10a, generally parallel to the struts 46. The space between the extreme end of hook end 47 and the opposed region of head 36 is open, so that the jaw set 21 (and 23) may be readily positioned around the tool joint when the entire apparatus is moved toward the tool joint as described subsequently. 
     A typical tool joint is shown schematically in FIGS. 10 and 11, the joint having an upper component 56 threadedly connected to a lower component 57. In a conventional drill pipe string, the upper component is turned clockwise during making of the joint. 
     As shown in FIGS. 10 and 11, the upper and lower jaw sets 21, 23 are alternately closed for actual torquing of the joint The middle jaw set 22, on the other hand, is always closed for such torquing. 
     Proceeding next to the middle set 22 of jaws, and referring particularly to FIG. 3, this is identically constructed to the upper and lower jaw sets 21, 23 except as specifically described. 
     Like the upper and lower sets 21, 23, the middle set 22 opens away from the frame portion 10a, so that all three jaw sets 21-23 are simultaneously mounted on the tool joint 56, 57 when the apparatus is moved toward such joint. Very importantly, however, the middle set 22 of jaws is reverse-oriented relative to the top and bottom sets 21, 23. Thus, the hook end of jaw set 22 extends in a direction diametrically opposite that of the hook ends of jaw set 21, 23. Accordingly, as previously stated, the middle jaw set further energizes and rotates a tool joint component when the middle set is rotated counterclockwise. 
     The components of the middle set 22, except those additional components specifically described, are given the same reference numeral as are the components of upper and lower sets 21, 23, except followed in each instance by the letter &#34;a&#34;. 
     As previously indicated, the middle jaw set is not connected directly to frame portion 10a but instead is pivotally connected by pivot means 28 to the end of the piston rod 29 (FIGS. 4 and 5) of torquing cylinder 24. Stated more specifically, the struts 46a that support head 36a connect to a vertical plate 60 that, in turn, is fixedly connected to a second vertical plate 61 to which are secured upper and lower horizontal plates 62, 63. Extended between horizontal plates 62, 63 is a cylinder 64, such cylinder and the plates 62, 63 being part of the pivot means 28 that effect the strong pivotal connection between the piston rod of cylinder 24 and the middle jaw set 22. 
     General Description of the Method Relative to the Apparatus Portions Thus Far Described 
     Stated generally, the method comprises disposing three vertically-spaced jaw sets, mounted on a common frame, at the wellhead of a well and adjacent a pipe string having threaded joints. The nuts 50 and 50a are rotated to adjust the jaw openings to the proper size for the particular pipe being operated upon. 
     To form a joint, the top pipe section is rotated (spun up), as by a spinning tool, until only final tightening is required. Then, the present apparatus is adjusted to such a vertical position that the top jaw set 21 is adjacent the upper component 56 of the tool joint (FIG. 10). The middle jaw set 22 is--because of the amount of spacing between the vertically-spaced wrenches--then adjacent the lower component 57 of the tool joint. The lower jaw set 23 is then normally below the tool joint, being then adjacent the pipe itself. 
     The upper and middle jaw sets 21, 22 are then closed on the pipe, following which the upper jaw set is rotated to make the joint. Thereafter, the upper and middle jaw sets are opened so as to release the thus made joint. 
     To break (or loosen) a joint prior to unthreading thereof (as by spinning out by use of a conventional spinning tool), the apparatus is moved vertically to the position of FIG. 11. Middle jaw set 22 is then adjacent the upper component 56 of the joint; lower jaw set 23 is adjacent the lower joint component 57; and upper jaw set 21 usually is above the joint. 
     The middle and lower jaw sets 22, 23 are then closed as shown in FIG. 11. The middle jaw set 22 is then rotated counterclockwise to break or loosen the joint. 
     The method comprises providing the upper, middle and lower jaw sets in vertically spaced relationship and connected together in a self-contained tool. The upper and lower jaw sets 21, 23 are fixed to a common frame. 
     The middle jaw set 22 is not fixed to the frame but instead pivotally associated therewith, the relationships being such that the middle jaw set may pivot horizontally relative to the frame and, at other times, the frame may pivot horizontally relative to the middle jaw set. In the preferred form, such relative pivoting is effected by a torquing cylinder connected between the frame and the middle jaw set. 
     To make a joint, after spinning up of the upper pipe section, the tool is caused to be at the vertical and horizontal positions, shown in FIG. 10. Furthermore, the tool is suspended at the wellhead, as from the rig hook shown in FIG. 2. 
     The upper and middle jaw sets 21 and 22 are then closed. Because jaw set 22 is closed on the lower joint component 57, they cannot move in that the pipe string already in the well tends strongly to prevent such movement. Thus, when the torquing cylinder 24 is operated, the middle jaw set 22 remains stationary and the entire remainder of the tool rotates about a vertical axis. The direction of rotation is caused to be such as to make the joint between tool joint sections 56, 57. Jaws 21, 22 are then opened, and the tool resumes its original position. 
     It is to be noted that the entire tool can thus be rotated because it is suspended in a relatively freely rotatable manner, at least through the small angle required for making of the joint. 
     To break the joint, the tool is positioned in the orientation shown in FIG. 11, and middle and bottom jaw sets 22, 23 are closed. Because bottom jaw set 23 is fixedly associated with the frame of the tool, operation of the torquing cylinder does not rotate the tool but instead rotates only the upper tool joint component 56. The direction of rotation is such as to break the joint. Jaw sets 22, 23 are then opened. 
     Stated more definitely, the jaw sets are caused to be of a type which energize in response to rotation in a particular direction. Upper and lower jaw sets 23 are oriented in the same way, while middle jaw set 22 is reverse-oriented Stated more definitely, the upper and lower jaw sets are so oriented as to tend to rotate the pipe clockwise while the middle jaw set 22 is oriented to rotate the pipe counterclockwise. 
     Making of a joint is indicated in FIG. 4, in which the parts are shown with the jaws closed on the tool joint. The before-making position is shown in solid lines, the torquing cylinder 24 being in its retracted condition. To make the joint, torquing cylinder 24 is operated to the extended position shown in phantom line in FIG. 4. Because the middle jaw set 22 is locked to the lower joint component 57, such extension causes the entire tool to rotate clockwise and, therefore, the upper jaw set rotates with it to make the joint. The jaws are then opened. 
     It is to be noted that the lower jaw set 23 does not interfere with rotation of the tool, because it is at all times open, during the making operation, as shown in FIG. 10. 
     Breaking of a joint is shown in FIG. 5, which is to be considered in conjunction with FIG. 11. The tool is raised to the FIG. 11 position, and the middle and lower jaw sets 22, 23 are closed, respectively, on the upper and lower tool joint sections 56, 57. (Jaw set 21 is not closed.) This is done while the torquing cylinder 24 is in its retracted condition shown in solid lines in FIG. 5. 
     Then, the torquing cylinder is again extended, to the phantom line position, as it was during the making operation described relative to FIG. 4, but this time the tool does not rotate. Instead, the tool is locked on the stationary lower joint component 57 by jaw set 23. Only the middle jaw set 22 rotates. The cylinder extension causes counterclockwise rotation of the middle jaw set 22, thus breaking the tool joint. The jaws are then opened. 
     One aspect of the method comprises initially closing the single-direction jaws by bite cylinders such as cylinders 52 and 52a. Such cylinders achieve the initial gripping, when combined with die means set forth below, while the hook-and-head combination of the jaws achieves final gripping in response to rotation or attempted rotation of a pipe section. Each of the preferred jaw sets will operate in only a single direction relative to the pipe, in the preferred embodiment. 
     In the preferred embodiment of the method, the operation of the single torquing cylinder in the same direction causes making of a joint when a joint is being made, and causes breaking of a joint when a joint is being broken. In the preferred form, this single direction is the one which causes the cylinder to extend. 
     Description of Die and Cam Means 
     Referring to FIGS. 6-9, inclusive, there are shown die and cam means adapted (1) to effectively grip tool joint after tool joint without damaging it, (2) to be usable with different diameters of tool joints within a predetermined wide range, and (3) to open and close automatically as the apparatus is moved off and on a string of pipe. 
     The cam and die elements on opposite sides of the tool joint are mirror images of each other; therefore, they are given the same reference numerals. 
     The strong element 39 of head 36, and the hook end 47 of hook 37, are provided with opposed recesses the walls 65 of which are generally semicylindrical (FIG. 7). Each such recess rotatably receives a die segment 66 that is also generally semicylindrical. As shown in FIGS. 7 and 9, each die segment 66 has a central portion 67 the diameter and height of which correspond to that of the wall 65 into which the die segment fits. Furthermore, each die segment has upper and lower flange portions 68 that fit above and below the element 39 or the hook end 47. The head plates 42, 43 are cut back to prevent interference with flange portions 68. 
     Removably mounted in each die segment 66 is a die insert 69 having a multiplicity of elongate vertical teeth 71 (FIG. 7). Each die insert 69 is held in its associated die segment 66 in dovetail relationship, and is prevented from moving vertically by edge portions of cam plates described below. 
     In the preferred form, the crests of the teeth of each die do not lie in a plane but instead lie along the surface of a vertically-disposed imaginary cylinder. Such imaginary cylinder has a diameter somewhat larger than that of the largest diameter of tool joint relative to which the present apparatus is adapted to operate. Where (for example) the largest diameter of tool joint is 7 inches, the imaginary cylinder has a diameter of 73/8 inches. Horizontal cam plates 73 are mounted above and below each die segment 66, as by screws 74. Each cam plate has an arcuate slot 75 therein, the slot having the same center (vertical axis) as that of the associated semicylindrical wall 65. A screw 76 extends through each slot 75 and is threaded into the associated plate 42, 43 (and element 39) or hook end 47. The slot walls cooperate with the screws 76 in maintaining die segments 66 seated rotatably in their associated recesses, with the generally semicylindrical walls 65 adjacent the corresponding walls of central portions 67. 
     The cam plates 73 have edge portions 77 that cooperate with the tool joint 56 (and 57) in cam and cam-follower relationship. Thus, as shown in FIGS. 6 and 7, edge portions 77 are relatively straight adjacent the outer regions of die inserts 69, and incline forwardly (outwardly) from the regions of the forwardmost teeth 71. At regions relatively remote from the die inserts, the edges 77 are rounded to facilitate mounting of the present tool onto a drill string. 
     FIG. 6 shows the cam and die apparatus in the positions assumed when the tool is being moved off a pipe string. This occurs when the various bite cylinders 52 are in their retracted conditions, the jaws being open. 
     FIG. 8 shows the positions of the parts after tool joint 56, 57 is centered--by stop means described below--between the die segments 66, and after the cylinders 52 have been operated to extended condition to initially close the jaws. 
     The parts are so constructed, and the nuts 50 so set, that when the jaws are thus initially closed as shown in FIG. 8, the central portions of the die inserts 69 are in engagement with substantially diametrically opposite regions of tool joint 56, 57. The die inserts automatically center on the pipe. 
     After the joint has been made or broken, the cylinders 52 are operated to their retracted conditions so as to open the jaws. The present apparatus is then moved off of the tool joint 56, 57, the parts then coming into the position of FIG. 6 before the apparatus is completely away from the tool joint. 
     As the apparatus moves from the FIG. 8 position to the FIG. 6 position, the die segments 66 are caused to pivot in opposite directions such that the inner regions thereof (those regions relatively adjacent shank 41 of the hook) are relatively close together as shown in FIG. 6. Stated otherwise, the left die segment 66 shown in FIG. 6 pivots clockwise while the apparatus is moved off the tool joint, while the right die segment shown therein then moves counterclockwise. The inner die portions (those nearest shank 41) are then relatively close to each other, in position to engage and be moved apart by a tool joint 56, 57 when the apparatus is again mounted onto a tool joint. 
     When another joint is to be made or broken, the apparatus is moved onto such other joint, which usually initially comes into contact with one or the other of the vertically-aligned sets of cam plates 73, at rounded regions thereof. The present apparatus is then moved further toward the tool joint, until the tool joint seats on the stop means described below. Then, the bite cylinders 52 are extended to cause initial biting of the teeth 71 into the tool joint surface. The dies automatically center as above stated. 
     When the tool joint is one that is relatively small in diameter, only relatively central ones of the teeth 71 engage and bite the tool joint surfaces. This is satisfactory because less torque is required to break or make a relatively small-diameter tool joint than is required to make or break a relatively large-diameter tool joint. When the tool joint is relatively large in diameter, so that all or substantially all of the teeth 71 engage and bite into the tool joint surfaces, more teeth are engaged with the tool joint to transmit the additional torque needed for relatively large-diameter tool joints. 
     As above stated, the diameter of the imaginary cylinder containing the crests of teeth 71 is caused to be somewhat larger than the diameter of the largest-diameter tool joint to be made or broken by the present apparatus. This is in order that there will be an initial stress concentration at those teeth which initially engage the tool joint, when the bite cylinders are extended, causing such teeth to bite into the tool joint with high stress concentration and thus prevent slippage. As the pressure increases, as the result of torquing and consequent pivoting of the hooks, the teeth bite in more and more but not so much as to damage the tool joint. 
     When the apparatus is moved onto a tool joint, the tool joint initially engages the inner regions of the die segments, those nearest shank 41, which are then in the general pivoted position of FIG. 6. Such engagement causes the inner regions of the die segments to pivot in opposite directions (counterclockwise relative to the left segment in FIG. 6, clockwise relative to the right segment therein) before the below-described stop means is engaged. 
     The diameters and centers of the die segments 66 are such that torquing of the jaw sets causes increased energization thereof for more firm biting of the teeth 71 into the tool joint surfaces, but without crushing or damaging the tool joints. The center of the generally semicylindrioal surface of the central portion 67 of each die segment 66 is located somewhat into the wall of the tool joint 56, 57. For example, and referring to FIG. 8, the center of the central portion 67 shown at the right is caused to be slightly to the left of teeth 71 of such right die segment 66. Similarly, the center of the left die segment 66 (FIG. 8) is caused to be somewhat to the right of the teeth of such left die segment. This relationship causes the dies to self energize, to bite into the tool joint during torquing, instead of rolling off the tool joint. 
     Apparatus and Method for Positioning Different Diameters of Tool Joints in Proper Relationship to the Dies, and for Positioning the Middle Jaw Set 22 in Proper Rotated Position Prior to Commencement of a Make or Break Operation 
     Referring to FIGS. 3 and 5, two generally L-shaped cranks 78 are provided, the illustrated cranks being above and below the middle jaw set 22. Cranks 78 are connected, at corresponding positions, to upper and lower ends of a vertical shaft 79. Such shaft is pivotally mounted at its ends on ears 81 that are secured to the frame 10 of the apparatus. 
     An actuation crank 82 is also connected to the shaft 79, the outer end of such crank 82 being pivotally associated with a linkage 83 and thus with a nut 84. Nut 84 receives a threaded shaft 86 on the outer end of which is mounted a knob or handle 87. 
     The nut 84 is welded to a bracket 88 secured to frame 10. Shaft 86 does not connect to such bracket 88 except at the nut 84. The end of shaft 86 is rotatably associated (but without permitting relative axial movement) with a bracket 89 that is pivotally connected to the linkage 83. 
     With the described construction, rotation of handle 87 causes pivoting of shaft 79 and thus adjusts forwardly or rearwardly the end faces 91 of cranks 78. These end faces 91 act as stops that engage the tool joint 56, 57. For any size of tool joint in the operating range for the particular tool (for example, a range of 3.5 inch 0.D. to 7 inch 0.D.), the handle 87 is turned to such position that end faces 91 will cause the tool joint to be centered in the jaws 21-23. 
     To adjust the apparatus for different diameters of tool joints, the handle 87 is turned as described. Furthermore, the various nuts 50 are turned to open or close each set of jaws 21-23, as described subsequently, to accommodate the different joint diameters. 
     There will next be described the means and method for causing the middle jaw set 22 to be in the desired position prior to the beginning of each make or break operation. The means for accomplishing this result are correlated to the adjustable stop means described above. 
     There is provided on the shaft 79 a third crank, numbered 92, that is pivotally connected through a link 93 to a pivotal stop 94. The stop 94 is pivotally connected, at 96, to a bracket 97 on frame 10 (FIG. 5). The link 93 is adjustable in length, being formed of two components that overlap each other and are secured together by bolts 98 extending through a longitudinal slot 99 (FIG. 5). 
     A vertical pin 101 is secured firmly to the upper head plate 42a of middle jaw set 22. Pin 101 extends upwardly to the elevation of pivotal stop 94, the latter being a horizontal plate having a relatively sharply concave edge 102 (FIG. 5) on the side thereof relatively adjacent the pin 101. A helical tension spring 103 is connected between the middle jaw set 22 and the frame 10, such spring being directed to bias the middle jaw set to a position at which pin 101 engages the concave edge 102 of stop 94. Stated more specifically, spring 103 is connected to the outer end of the body of cylinder 52a of the middle jaw set, as shown in FIG. 3. 
     During the above-described portion of the method by which a tool joint is made, the middle jaw set 22 is locked in position and the frame 10 is moved clockwise. When the frame thus moves clockwise, the stop 94 pivots away from the then-stationary pin 101. Conversely, when a joint is broken, the frame is held stationary by the lower jaw set 23 while the middle jaw set 22 is pivoted counterclockwise, so that the pin 101 moves away from the then-stationary stop 94. In either case, the spring 103 is stretched and subsequently pivots the middle jaw set 22 relative to the frame until the pin 101 comes to a soft landing on the curved edge 102 of stop 94. 
     The landing is &#34;soft&#34; because the helical tension spring operates while the torquing cylinder 24 is being retracted hydraulically, it (and all cylinders described herein) being double-acting. Such retracting causes the parts to shift from the phantom-line positions in FIGS. 4 and 5 to the solid-line positions therein. Retraction of cylinder 24 is effected, in each instance, after the joint has been made or broken, and after the bite cylinders 52 have been retracted to their jaw-open positions. The stop 94 is adjusted conjointly with adjustment of end faces 91 as described above, by turning the handle 87 to rotate shaft 79. The various cranks and links are proportioned and adjusted, (it being remembered that the link 93 is adjustable in length by first loosening and then tightening the bolts 98 (FIG. 5), in such manner that the middle jaw set 22 will be in the correct pivoted position relative to the upper and lower jaw sets 21 and 23 for each diameter of tool joint. 
     Thus, to change the apparatus for operation on a different diameter tool joint than that relative to which previous operations had been occurring, the handle 87 is turned in order to shift stop 94 in the appropriate direction for the different joint diameter Furthermore, the three nuts 50 and 50a are turned on their threaded shanks 41 to open or close the jaw sets to the proper setting for the new diameter of tool joint. Marks may be provided on the shanks 41 and on the stop 94 to aid in these adjustment operations. 
     The heads 36 of top and bottom jaw sets 21, 23 are fixed in position, in vertical alignment. Thus, the hook 37a of the middle jaw set 22 is caused, at its teeth, to be directly between and in line with the teeth of the top and bottom heads 36. It is the head 36a, of the middle jaw set 22, that is adjusted in position so as to accommodate different joint diameters. Stated otherwise, once the jaw openings are correct for the particular joint diameter, as determined by nuts 50 and 50a, the described stop and pin mechanism 94, 101, etc., is so set that when the pin 101 engages the stop 94, the teeth of the head 36a of the middle jaw set are directly in line with the teeth of the top and bottom hooks 37. 
     Description of the Pivot and Adjustment Means and Method for Associating Nuts 50 With Hook Shanks 41 and Heads 36 in Precision Manner 
     Again, the pivot and adjustment portion of only the upper jaw set 21 will be described, it being understood that the lower jaw set 23 has the same elements identically numbered. Also, the middle jaw set 22 has the same elements, also identically numbered except that the letter &#34;a&#34; follows each numeral. 
     Referring to FIGS. 8 and 12, nut 50 has a strong collar 106 partially telescoped thereover and welded fixedly thereto, at the nut end relatively adjacent head 36. A bearing ring 107 is strongly pivotally connected to head 36. Such bearing ring has an outer diameter corresponding to that of nut 50; the outer cylindrical surface of bearing ring 107 fits slidably within collar 106 as shown in FIG. 8. 
     The bearing ring 107 has an annular groove 108 formed externally thereof. The annular groove 108 is disposed radially-inwardly of, and receives, pins 109 that extend radially-inwardly through the protruding end of collar 106. The pins are circumferentially spaced about collar 106, and their inner ends prevent the combination nut 50 and collar 106 from moving axially relative to bearing ring 107. On the other hand, rotation of the combination nut 50 and collar 106 causes the shank 41 and thus all of hook 37 to move axially relative to the head 36, the direction of movement depending upon the direction of rotation of the nut and collar. 
     Bearing ring 107 is strongly welded to a cylinder 111 that is rotatably mounted in vertical relationship in the top and bottom plates 42, 43 of head 36. Cylinder 111 has a relatively large-diameter main body 112 coaxially rigidly associated with upper and lower necks 113. 
     Body 112 of cylinder 111 is sufficiently long to extend between the outer surfaces of head plates 42 and 43. It does so through semicylindrical-walled openings 114 formed in such head plates at the edges thereof adjacent nut 50, and between the strong elements 38, 39 (FIG. 8). 
     To maintain the cylinder 111 in semicylindrical-walled openings 114, upper and lower C-rings 116 are secured by screws to the upper and lower head plates. Each C-ring has an inner diameter only slightly larger than that of the necks 113 of cylinder 111. Since the C-rings extend for more than 180 degrees, they prevent the cylinder 111 from moving away from the head plates. At the same time, the C-rings prevent upward and downward movement of the cylinder 111. 
     The bearing ring 107, which is also an adjustment ring in that it cooperates in determining the shank positions of the hook element, is spaced sufficiently far from the head plates 42, 43 and other head elements that bearing ring 107 may pivot about a vertical axis through a predetermined angle. This predetermined angle is sufficiently large to accommodate any angular position that shank 41 is pivoted to due to operation of bite cylinders 52 and/or due to operation of torquing cylinder 24. 
     The openings 114 and the cylinder 111 are not centered relative to bearing ring 107 but instead are located to one side thereof, as shown in FIGS. 8 and 12, such side being the one on the opposite side of shank 41 from hook end 47. Furthermore, the main body 112 of cylinder 111 is carved out at one side so that, as viewed in FIG. 12, the cylinder body 112 appears generally U-shaped. The side positioning, and the carving out are such that the shank 41 of hook 37 may be and is extended through and adjacent cylinder body 112, and between the strong elements 38 and 39. 
     Furthermore, the nut 50 is threaded onto the threads 48 of shank 41, and the bearing ring 107 fits closely around the threads 48 thereof. Accordingly, the described apparatus causes there to be, for any adjusted position of shank 41 relative to the head 36, a precisely-located vertical pivot axis for hook 37. Such precise pivot axis is at the center of cylinder 111. 
     The cylinder 111 has grease fittings and passages G at its upper and lower portions, as shown in FIG. 12. The passages communicate with external grease grooves. 
     The described mechanism, accordingly, not only causes the hook 21 to move inwardly and outwardly to various precise desired settings, but causes such mechanism to pivot about a precise vertical axis for any hook setting. Accordingly, and because of the above-described die elements 66 and other elements, the present jaw apparatus will operate effectively on tool joint after tool joint, with little or no problem of slipping In addition, the described apparatus provides a very strong bearing relationship by which the strong powerful forces present in the hook 37 are effectively transmitted to the head plates 42, 43 in large-area bearing relationship, for maximized strength and wear resistance. 
     BRIEF SUMMARY OF METHOD 
     The tool is adjusted for the particular diameter of tool joint, as described above, and is mounted on the tool joint as described above. 
     To make a joint, jaw sets 21, 22 and 23 are put in the positions shown in FIG. 10. Upper and middle bite cylinders 52, 52a are operated to extend themselves and thus close jaw sets 21 and 22, so that they bite on the upper and lower tool joint components 56, 57. Then (FIG. 4), torquing cylinder 24 is extended to rotate the entire tool except for jaw set 22. The jaw sets energize, as described. 
     As the joint becomes tighter and tighter, the hydraulic pressure in torquing cylinder 24 builds up to a pre-set point that is adapted to achieve the correct predetermined desired degree of &#34;make&#34; torque on the joint. Then, a bypass valve opens that bleeds the pressure from torquing cylinder 24. The jaw sets 21, 22 accordingly deenergize. Then, the bite cylinders 52, 52 of the upper and middle jaw sets are operated to retract themselves and thus open the jaws. Then, torquing cylinder 24 is operated to retract itself until it bottoms out. The middle jaw set is simultaneously pivoted to its original position by spring 103. The retracting cylinder 24 is caused to bottom out just before pin 101 hits stop 94, so that final pivoting of jaw set 22 is caused solely by spring 103, such final movement continuing until elements 101 and 94 engage with each other. 
     To break a joint, the parts are moved to the FIG. 11 positions as described above. Bite cylinder 52a, 52 of middle and bottom jaw sets 22, 23 are operated to extend themselves and cause biting onto joint components 56, 57. Torquing cylinder 24 is operated in the same direction as before--in a direction to extend itself (FIG. 5) and pivot jaw set 22 while the rest of the tool is stationary. The jaw sets 22, 23 energize. The hydraulic pressure delivered to cylinder 54 is caused to be sufficient to break the tool joint. The cylinder 24 is extended until it substantially bottoms out. Then, cylinder 24 is bled of pressure, so that jaw sets 22, 23 deenergize. The bite cylinders 52a, 52 of the middle and lower jaw sets are operated to retract themselves and open the jaws. 
     Then, cylinder 24 is operated to retract itself, and this in combination with spring 103 move the middle jaw set back to start position Again, the spring by itself performs the last part of this motion, until pin 101 and stop 94 engage. 
     In the appended claims, the &#34;first string&#34; and &#34;second string&#34; may be the same string--at one time being connected and at another time disconnected. 
     The foregoing detailed description is to be clearly understood as given by way of illustration and example only, the spirit and scope of this invention being limited solely by the appended claims.