Abstract:
A back-up tong is provided with one or more linearly-acting hydraulic cylinders which advance a triangular wedge in order to drive a pipe gripping jaw inwardly into engagement with pipe. A thrust-receiving jaw that is not hydraulically actuated can be adjusted in its fixed position. Springs within the actuated jaw bias it to recoil spontaneously from the pipe upon the retraction of the wedge.

Description:
FIELD OF THE INVENTION 
     This invention relates to oil tools for making and breaking tubular connections used in the oil industry. More particularly it relates to a back-up tong for grasping tubular elements, e.g. pipe, casing or completion tubing in the oil well equipment art. 
     BACKGROUND TO THE INVENTION 
     In oil well drilling equipment the coupling and uncoupling, or so-called “making” and “breaking” of the connection on tubular is usually effected by pipe gripping tongs. The lower pipe section is usually gripped and held against rotation by a “back-up” tong and the upper pipe section is usually gripped and rotated by an upper “break-out” or “make-up” tong. 
     A variety of mechanical arrangements have been employed to advance the jaws within a back-up tong in order for such jaws to engage with and grasp the tubular. In U.S. Pat. No. 4,647,777 three jaws are advanced radially inwardly along linear paths by the direct application of hydraulic pressure to the jaws. In U.S. Pat. No. 4,402,239 a pair of opposed jaws are advanced radially inwardly by hinged linkages connected to a hydraulic cylinder. In U.S. Pat. No. 4,778,742 the jaws are carried on hinged supports and are driven inwardly along arcuate paths by the rotation of the supports under hydraulic pressure. Lastly, in U.S. Pat. No. 4,290,304 a pair of opposed jaws are driven radially inwardly by the rotational advancement of a crescent-shaped wedge carried on a “C”-shaped ring that is turned through gearing linked to a hydraulic motor. 
     In all of the above cases the mechanical systems transmit a force to the jaws that is dependent on the position and shape of the parts, following a single, fixed force-application schedule. While pipe of slight variations in diameter may be accommodated without a change of parts, if pipe of substantially different diameter is to be grasped, major parts must be changed to adjust the schedule by which the force is applied. This is a separate consideration from that of using interchangeable jaws to provide grasping surfaces that accommodate pipes of differing diameters. 
     It is an object of this invention to provide a mechanical layout for tongs that accommodates the use of a wedge or combination of wedges to place a gripping apparatus about a tubular surface and apply a gripping force thereto. The ready inter-changeability not only of jaws but also of intermediate components that govern the schedule by which force is applied to pipe with the advance of the jaws within a tong render the invention convenient and advantageous. 
     The invention in its general form will first be described, and then its implementation in terms of specific embodiments will be detailed with reference to the drawings following hereafter. These embodiments are intended to demonstrate the principle of the invention, and the manner of its implementation. The invention in its broadest and more specific forms will then be further described, and defined, in each of the individual claims which conclude this Specification. 
     SUMMARY OF THE INVENTION 
     According to one aspect of the invention a tong for grasping tubular members is provided that includes: 
     (1) a frame having a central pipe opening with a center region and an entry throat for receiving a tubular member to be grasped; 
     (2) a thrust-receiving jaw carried by a thrust-receiving jaw support that is attached to the frame for fixing the position of the fixed jaw within the pipe opening; 
     (3) a displaceable jaw assembly containing a radially displaceable pipe-engaging jaw mounted at the inner jaw end of a jaw carrier shaft for advancement of the jaw into the pipe opening; 
     (4) a wedge with two face surfaces, one of said face surfaces being positioned against the outer wedge end of the jaw carrier shaft, opposite the jaw end; 
     (5) a thrusting seat coupled to the frame and contacted by the other of the face surfaces of the wedge; and 
     (6) a linear actuator anchored at one end to the frame and aligned at its other end to move the wedge forward between the outer wedge end of the jaw carrier shaft and the thrusting seat for advancement of the displaceable jaw radially towards the center of the pipe opening, 
     whereby activation of said hydraulic actuator for movement of the wedge will advance the jaw carrier shaft and move the displaceable jaw inwardly with respect to the pipe opening to grasp a tubular member contained therein. 
     To permit the access of pipe to the pipe opening, an entry throat with a gate is provided. The thrust-receiving jaw may be carried by a hinged jaw support connected to the frame which serves as a gate. The hinged jaw support may be swung so as to allow the thrust-receiving jaw to retire and expose the entry throat for pipe to be placed within the pipe opening. With pipe in position within the pipe opening the hinged jaw support may be swung to close the entry throat and position the thrust-receiving jaw so that it is directed towards the pipe or other tubular member that is to be grasped. The hinged jaw support is latched in place during pipe engagement. 
     The thrust-receiving jaw may be permanently fixed against radial displacement towards and away from the pipe opening. Or it may be adjustable as to its location in order to permit it to occupy a series of fixed positions with respect to the pipe opening. Such adjustable locations may be used to accommodate various ranges of pipes. 
     The thrust-receiving jaw is preferably adjustable in its radial position with respect to the pipe opening by a screw type adjustable jaw positioning means carried within the hinged jaw support. The jaw positioning means will normally be adjusted so that when the thrust-receiving jaw contacts the pipe, the pipe is approximately centered about the center line of the pipe opening. In this manner, a range of pipe diameters can be accommodated. 
     As a further feature, the jaw assembly and linear actuator may be rendered repositionable with respect to the frame to permit the accommodation of a larger range of pipe sizes. 
     The jaw of the displaceable jaw assembly may also be interchangeable to permit substitution of jaws dimensioned to engage with pipes of differing diameters. Further, the wedge may be interchangeable to control the schedule of force being applied by the jaw to pipe. 
     The jaw assembly includes a jaw carrier shaft that is constrained by guide surfaces carried by the frame to allow the jaw to advance radially towards and away from the pipe opening. The jaw assembly preferably includes means by which the jaw will spontaneously retreat, out of the pipe opening, when the wedge is caused to withdraw under the reverse action of the linear actuator. To provide resilience, a spring means operates to bias the jaw outwardly, away from the pipe opening, to the limit of its marginally permitted displacement with respect to the jaw assembly. This function may be provided through a spring located internally within the jaw carrier shaft. While the prior art has employed a spring attached externally to the jaw and mounted to the outer frame, this new arrangement of the invention avoids exposing the spring to the outside environment, and reduces interference with the operation of the tong. 
     The jaw assembly and its associated actuator may be displaceable within the body of the tong to allow the tong to accommodate an exceptionally broad range of tubular diameters. 
     The linear actuator may be in the form of a hydraulic cylinder. Or it may be in the form of a motor and worm gear drive or other equivalent performing apparatus. 
     The tong of the invention may have a single displaceable jaw or multiple displaceable jaws. When a single jaw is employed, the thrust-receiving jaw may be positioned at the inner side of the pipe opening, facing the throat, and the displaceable jaw may be carried by the hinged jaw support that swings in place across the throat. 
     Each displaceable jaw will have an associated wedge. However, multiple wedges may be advanced by a single linear actuator. 
     Normally, a single wedge will be driven by a single linear actuator. However, the wedging action may be arranged to arise through the use of multiple wedges in series. In this case, a single linear actuator can cause two displaceable jaws to advance. The actuator achieves this by advancing a primary wedge which has two primary, wedging, thrust surfaces. Two secondary wedges, each driving a jaw carrier shaft, are then advanced by contact with one of the primary wedging thrust surfaces. The secondary wedges in such cases may have differing angles of inclination, giving rise to differing force schedules for the jaws which they advance. 
     An advantage of the invention is that the wedge which drives the advancement of the jaw may be interchanged with an alternate wedge to adjust the mechanical advantage that they provide. This provides a means of controlling the schedule of compressional radial force that the jaws apply to the well pipe as they advance radial inward. 
     The wedges of the invention may be triangular in shape, with flat surfaces. Alternately, compound surfaces having regions of differing angles of inclination may be provided. This allows the force schedule to change as the wedges advance with respect to the thrusting end of the jaw carrier shaft. 
    
    
     The foregoing summarizes the principal features of the invention and some of its optional aspects. The invention may be further understood by the description of the preferred embodiments, in conjunction with the drawings, which now follow. 
     SUMMARY OF THE FIGURES 
     FIG. 1 is a schematic perspective view of the back-up tong of the invention with a top cover plate removed and the pipe receiving throat open; 
     FIG. 2 is an exploded perspective view of the key parts of FIG. 1 taken from a second perspective with the throat closed and with the displaceable jaw assembly and linear actuator separated from the tong body; 
     FIG. 3 is a perspective view of the parts of the jaw assembly of FIG. 2; 
     FIG. 4 is an exploded perspective view of a jaw and carrier shaft, including the spring biasing components; 
     FIG. 5 is a horizontal cross-sectional plan view taken through FIG. 4 when assembled; 
     FIG. 6 is a vertical cross-sectional side view taken through FIG. 4 with the jaw carrier shaft advanced as when tubular is being engaged; 
     FIG. 7 is a vertical cross-sectional view as in FIG. 6 when the jaw carrier shaft has retired from engagement with tubular; 
     FIG. 8 is a plan view of two jaw assemblies of the tong positioned at two different locations with respect to the lower plate of the tong to engage 20 inch and 8⅝ inch diameter pipe respectively; 
     FIGS. 9 and 10 are plan views of the tong with the jaws engaged and retracted using wedges with multiple contact surface slopes. 
     FIGS. 11 and 12 are a detailed plan views of the thrust-receiving jaw and hinged support, showing the thrust-receiving jaw position adjustment mechanism in retired configuration and advanced positions respectively; 
     FIG. 13 is a plan view of the throat of a tong having a wedge-driven displaceable jaw present in the gate that closes the throat; and 
     FIG. 14 is a schematic plan view of a tong layout that allows two linear actuators to drive four displaceable jaws. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     In FIG. 1 is a tong  1  with dual displaceable jaws  9  has a frame  2  which includes an outer frame wall  7  and upper cover plate  17  and a lower floor plate  16 . Various upright spacer walls (not shown) may extending between the lower plate  16  and upper plate  17  to stiffen the frame  2 . An optional box beam  58  beneath the lower plate  16  may be present to accommodate lifting forks on a fork lift. 
     The displaceable jaws  9  are carried by jaw carrier shafts  10  of box-beam form and are positioned around the pipe opening  3 . The jaws  9  and their jaw carrier shafts  10  are all carried between upper and lower jaw assembly cover plates  19   a,    19   b,  creating as an integral unit a displaceable jaw assembly  8  that can be bolted to the upper and lower plates  16 , 17  at various locations. 
     Each hydraulic cylinder  36  is anchored to the frame  2  at one end and bears against a wedge  11  at its other end. The wedge  11  passes into the displaceable jaw assembly  8  between the wedge end  14  of the jaw carrier shaft  10  and a thrust seat  15  contained within the jaw assembly  8 . 
     The pipe opening  3  is accessed through throat  4  which can be closed-of by the thrust-receiving jaw  5  on its hinged support  6 . A hydraulic cylinder latch  18  locks the support  6  in its closed position, as shown in FIG.  2 . 
     In FIG. 2 the thrust-receiving jaw  5  is carried by a hinged support  6  which serves as a gate for the throat  4 . This thrust-receiving jaw  5  is adjustable in its position through means of a threaded shaft  59  shown with the thrust-receiving jaw  5  in retracted and advanced positions respectively in FIGS. 11 and 12. The threaded shaft  59  is shown engaged with a threaded coupling  20  within the thrust-receiving jaw support  6 , carrying the thrust-receiving jaw  5  with it as the threaded shaft  59  is rotated. 
     FIG. 3 shows a detail of the jaw assembly  8  with the jaw carrier shaft  10  contained by guide walls  21 . The guide walls  21  are rigidly fixed to the jaw assembly cover plates  19   a,    19   b  which are, in turn fixed to the frame  2  through bolt holes  22 . 
     Included within the displaceable jaw assembly  8  is the triangular wedge  11  which has a bearing surface  12  which contacts with the wedge end  14  of the jaw carrier shaft  10  remote from the displaceable jaw  9 . The other side  13  of the wedge  11  contacts a wedge rail that serves as a thrusting seat  15  that is fixed between the jaw assembly cover plates  19   a,    19   b.    
     To provide a means of retraction for the jaws  9  from pipe  30 , the wedge end  14  of the jaw carrier shaft  10  may contain a spring seat  23  fixed to the jaw carrier shaft  10  and contacted by spring  24 . The spring  24 , extending through a bore in the jaw carrier shaft  10 , bears at its other end against a spring bushing  25  which in turn bears against a pin  26  that is free to move within a slot  27  in the jaw carrier shaft  10 . This pin  26  is, however, fixed in holes  58  in the inner top and bottom cover and floor plates  19   a,    19   b  which are, in turn, affixed by pins  28  to the top  16  and bottom  17  plates of the frame  2  through plate holes  31 , 32 . 
     As shown in FIGS. 5 and 7, the spring  24  thrusts off of the pin  25  against the spring seat  23 , biasing the jaw carrier shaft  10  to retract to the limit. When the wedge  11  is engaged, the spring  24  is compressed (FIG. 6) as the pin  25  is allowed to travel down the slot  27  until the jaw  9  engages the pipe  30 . When the wedge  11  is retracted the spring  24  retracts the jaw  9  to free the pipe  30  from engagement by the jaw  9 . 
     By shifting the position of the thrust-receiving jaw  5  and allowing for the travel of the displaceable jaws  9  a range of pipe diameters, e.g. from 5.8 inches to 7.0, inches can be accommodated without the necessity of changing the jaws  5 , 9 . When pipe  30  outside of this range is to be grasped, the jaws  5 , 9 , and wedges  11  may be changed to accommodate the new pipe diameters. 
     One displaceable jaw assembly  8  is shown separated from the tong  1  in FIG. 2, along with its associated linear actuator  36 . By reason of this modular construction, this jaw assembly  8  can assume multiple positions within the tong  1 , accommodating an extended range of tubular members. 
     As shown in FIG. 8, the jaw assemblies  8  may be shifted on the floor plate  16  between inner  31  and outer  32  attachment holes in the floor plate  16  along with the actuator  36  to provide further flexibility. As depicted in FIG. 8 the left assembly  8   a  is positioned to accommodate  20  inch pipe  15  and the right assembly  8   b  is positioned to accommodate 8⅝ inch pipe  15 A. 
     FIGS. 9 and 10 show a tong provided with wedges  37  that have multiple slopes  38 ,  39  or inclines on the wedge bearing surface that contacts the jaw carrier shaft  10 . This will permit the schedule of force applied by the jaws  9  to vary with their degree of advancement towards pipe  30  in opening  3 . In particular, an initial steeper slope  38  may provide a rapid-advancement positioning phase; and a second shallower sloped portion  39  may operate in the high torque grasping phase. 
     FIG. 13 shows a tong with a single displaceable jaw  40 . This jaw is carried on a box shaft  41  that contains a threaded screw  49  for adjusting the advancement of the jaw  40  with respect to the shaft  41 . The shaft  41 , which is rectangular and hollow has a wedge  42  pierced through it laterally. This wedge  42  may be split to provide a balanced thrust. One face  43  of the wedge  42  bears against thrust posts  44 . The other inclined face  45  of the wedge  42  bears against an edge or edges of the shaft  41 . 
     The wedge  42  is advanced by a linear actuator  46  that also penetrates through a locking plate  47  on the hinged support  50  to serve additional as a latch. A fixed rear jaw  48  receives pipe  30  in the pipe opening  3 . 
     In FIG. 14 two linear actuators  61 , 62  anchored to the floor plate  16  of he tong drive two primary wedges  63 , 654 , each of which has two primary wedging thrust surfaces  65 . Two pairs of secondary wedges  66 , 67  are respectively driven off of these respective primary wedges  63 , 64 . On one side the secondary wedges  66  are advanced by the associated primary wedge  64  between their respective thrust seats  68 , 69  and jaw carrier shafts  60 , 61 . The opposing jaws  74 , 5  serve as thrust receiving jaw means. Again, secondary wedges  66 , 67  may have differing angles of inclination of their jaw advancement surfaces  72 , 73  to provide different force schedules to their respective jaws. 
     CONCLUSION 
     The foregoing has constituted a description of specific embodiments showing how the invention may be applied and put into use. These embodiments are only exemplary. The invention in its broadest, and more specific aspects, is further described and defined in the claims which now follow. 
     These claims, and the language used therein, are to be understood in terms of the variants of the invention which have been described. They are not to be restricted to such variants, but are to be read as covering the full scope of the invention as is implicit within the invention and the disclosure that has been provided herein.