hydraulic power tong api xq28 us patent manufacturer

This website is using a security service to protect itself from online attacks. The action you just performed triggered the security solution. There are several actions that could trigger this block including submitting a certain word or phrase, a SQL command or malformed data.

This website is using a security service to protect itself from online attacks. The action you just performed triggered the security solution. There are several actions that could trigger this block including submitting a certain word or phrase, a SQL command or malformed data.

This invention relates to the field of devices for rotating tubular members so as to make up or break out threaded joints between tubulars including casing, drill pipe, drill collars and tubing (herein referred to collectively as pipe or tubulars), and in particular to a power tong for the improved handling and efficient automation of such activity.

In applicant"s experience, on conventional rotary rigs, helpers, otherwise known as roughnecks, handle the lower end of the pipe when they are tripping it in or out of the hole. As used herein, the terms pipe and tubular are used interchangeably. The roughnecks also use large wrenches commonly referred to as tongs to screw or unscrew, that is make up or break out pipe. Applicant is aware that there are some other tongs that are so called power tongs, torque wrenches, or iron roughnecks which replace the conventional tongs. The use of prior art conventional tongs is illustrated in FIG. 1a. Other tongs are described in the following prior art descriptions.

In the prior art applicant is aware of U.S. Pat. No. 6,082,225 which issued Feb. 17, 1997 to Richardson for a Power Tong Wrench. Richardson describes a power tong wrench having an open slot to accommodate a range of pipe diameters capable of making and breaking pipe threads and spinning in or out the threads and in which hydraulic power is supplied with a pump disposed within a rotary assembly. The pump is powered through a non-mechanical coupling, taught to be a motor disposed outside the rotary assembly.

In the present invention the rotary hydraulic and electrical systems are powered at all times and in all rotary positions via a serpentine such as a serpentine belt drive, unlike in the Richardson patent in which they are powered only in the home position. In the present invention the pipe can thus be gripped and ungripped repeatedly in any rotary position with no dependence on stored energy and the tong according to the present invention may be more compact because of reduced hydraulic accumulator requirements for energy storage wherein hydraulic accumulators are used for energy storage only to enhance gripping speed.

Applicant is also aware of U.S. Pat. No. 5,167,173 which issued Dec. 1, 1992 to Pietras for a Tong. Pietras describes that tongs are used in the drilling industry for gripping and rotating pipes, Pietras stating that generally pipes are gripped between one or more passive jaws and one or more active jaws which are urged against the pipe. He states that normally the radial position of the jaws is fixed and consequently these jaws and/or their jaw holders must be changed to accommodate pipes of different diameters.

Applicant is also aware of U.S. Pat. No. 6,776,070 which issued Aug. 17, 2004 to Mason et al. for an Iron Roughneck. Mason et al. describes an iron roughneck as including a pair of upper jaws carrying pipe gripping dies for gripping tool joints where the jaws have recesses formed on each side of the pipe gripping dies to receive spinning rollers. By positioning the spinning rollers in the upper jaws at the same level as the pipe gripping dies the spinning rollers are able to engage the pipe closer to the lower jaws and thus can act on the tool joint rather than on the pipe stem. Mason et al. describe that in running a string of drill pipe or other pipe into or out of a well, a combination torque wrench and spinning wrench are often used, referred to as “iron roughnecks”. These devices combine torque and spinning wrenches as for example described in U.S. Pat. Nos. 4,023,449, 4,348,920, and 4,765,401, to Boyadjieff.

In the prior art iron roughnecks, spinning wrenches and torque wrenches are commonly mounted together on a single carriage but are, nevertheless, separate machines with the exception of the Iron Roughnecks of Mason which combines the spinner wrench rollers and torque jaws in a common holder, although they nevertheless, still work independently of each other. When breaking-out, or loosening, connections between two joints of drill pipe, the upper jaw of the torque wrench is used to clamp onto the end portion of an upper joint of pipe, and the lower jaw of the torque wrench clamps onto the end portion of the lower joint of pipe.

Drill pipe manufacturers add threaded components, called “tool joints”, to each end of a joint of drill pipe. They add the threaded tool joints because the metal wall of drill pipe is not thick enough for threads to be cut into them. The tool joints are welded over the end portions of the drill pipe and give the pipe a characteristic bulge at each end. One tool joint, having female, or inside threads, is called a “box”. The tool joint on the other end has male, or outside threads, and is called the “pin”. Disconnection of the pin from the box requires both a high-torque and low angular displacement ‘break’ action to disengage the contact shoulders and a low-torque high-angular displacement ‘spin’ action to screw out the threads. Connection of the pin and box require the reverse sequence. In the make/break action torque is high (10,000-100,000 ft-lb), having a small (30-60 degrees) angular displacement. In the spin action torque is low (1,000-3,000 ft-lb), having a large (3-5 revolutions) angular displacement.

Applicant is further aware of United States Published patent application entitled Power Tong, which was published Apr. 5, 2007 under Publication No. US 2007/0074606 for the application of Halse. Halse discloses a power tong which includes a drive ring and at least one clamping device with the clamping devices arranged to grip a pipe string. A driving mechanism is provided for rotation of the clamping device about the longitudinal axis of the pipe string. The clamping device communicates with a fluid supply via a swivel ring that encircles the drive ring of the driving mechanism. Thus Halse provides for three hundred sixty degree continuous rotation combining a spinner with a torque tong. The Halse power tong does not include a radial opening, the tong having a swivel coupling surrounding the tong for transferring pressurized fluid from an external source to the tong when the tong rotates about the axis of the pipe. Halse states that having a radial opening in a power tong complicates the design of the power tong and weakens the structure surrounding the pipe considerably, stating that as a result, the structure must be up-rated in order to accommodate the relatively large forces being transferred between the power tong and the pipe string. Halse further opines that a relatively complicated mechanical device is required to close the radial opening when the power tong is in use, and in many cases also to transfer forces between the sides of the opening. The Halse tong is not desirable for drilling operations because there is no throat opening to allow the tong to be positioned around the pipe at the operator"s discretion. The pipe must always pass through the tong.

The power tong according to the present invention continuously rotates tubulars for spinning and torquing threaded connections. Continuous rotation is achieved through a rotating jaw (also referred to as a rotor) that has grippers that grip the tubular. Hydraulic and electrical power necessary for actuating the grippers is generated on board the rotor since the continuous rotation does not allow for either hydraulic or electrical external connections. A serpentine member such as a serpentine drive belt system turns the motors of an on-board hydraulic power unit and electric generators which may be AC or DC generators, to supply the grippers with the necessary hydraulic and electrical power.

The present invention includes a rotor rotably mounted in or on a rigid structural framework or stator frame. A main drive drives the rotor. The rotor may be supported and held in position by the use of opposed helical pinions/gears which support the rotor vertically and guide bushings which locate it laterally and support it vertically when the torque is low. The grippers, which may be actuated by hydraulic gripper cylinders, maybe held in position by links and guide bushings that can withstand the torque parameters of the tong. The gripper cylinders may be moved in a range of travel by an eccentric. This provides for a tong that can accommodate a large range of pipe diameters (3.5 inch drillpipe to 9-⅝ inch casing or larger). A centralizing linkage ensures that the pipe is gripped concentricly with the tong axis of rotation. The tong does not require a mechanical device to close the radial opening. The on-board power source and rotary control system allow the present invention to have fully independently activated and controlled rotary gripping of the tubular. It is capable of high torque for making and breaking and high speed for spinning, all within one mechanism. One embodiment of the present invention also overcomes the limitation of the spinning wrench engaging the stem area of the drillpipe which over time will cause fatigue in the stem area as the spinning and torquing according to the present invention is accomplished with the same jaw that engages the pipe on the tool joint. The throat of the jaws according to the present invention has an opening of sufficient diameter to accept a tubular. The throat cooperates with the opening to allow the power tong to be selectively positioned around the pipe at the operators" discretion.

FIGS. 18 and 19 are in diagrammatic plan view, a further exemplary embodiment of the nested transmission of the tong, showing the use, by way of example, of two stator sprockets, at least one of which is driven, having a serpentine member therearound and reaved over a pair of rotor sprockets on the throated rotor, the pair of rotor sprockets having a synchronizer therearound, the rotor sprockets driving a coupling mechanism coupling the power transfer from the serpentine member to gripper actuators on the rotor which articulate grippers at the rotor axis of rotation.

FIG. 19ais a partially cut-away section view along line 19 a-19 ain FIG. 19 showing one rotor (satellite) sprocket driving, by way of example, a pump and/or generator part of the power or energy transfer coupling between the serpentine member and the gripper actuators.

As seen in FIGS. 1 and 2, the power tong 6 may include three main sections mounted on a common axis A; namely a main drive section, a rotor, and a back-up jaw. Each of the sections contains actuators, as better described below. The main drive section 10 which provides at least part of a rigid stationary framework or stator frame is located above the rotor 22. The backup jaw 48, located below rotor 22, may also provide part of the stator frame. The rotor 22 rotates relative to the main drive and back-up jaw. Both the rotor and backup jaw clamp their respective sections of pipe. The rotor 22 is rotated by the main drive section 10 independently of the main drive section and backup jaw in the sense that the rotor 22 is self-contained, having on-board hydraulic and electric power generators to power on-board radial clamps or grippers (collectively herein referred to as grippers), and an on-board serpentine secondary power transmission, all configured to allow the insertion and removal of a pipe through a jaw opening from or into the center of the jaw, so that the pipe, when in the center of the jaw may be clamped, torqued, and spun about axis A of rotation of the rotor 22 while the other, oppositely disposed section of pipe is held clamped in the center of the back-up jaw 48.

Main drive section 10 includes primary drives 12, each of which includes rotary drive motors 16, which may for example be hydraulic or electric motors, gear reduction devices 16 a, and belt drives 16 bas better seen in FIG. 2. Motors 16 cooperate with drive pinions 56 to rotate rotor 22 about axis A relative to main drive section 10 and back-up jaw section 24.

As shown in FIGS. 1, 2 and 3 rotor 22 is housed within drive section 10, although this is not intended to be limiting as the rotor may be mounted so as not to be housed within the drive section and still work. The rotor 22 is cylindrical in shape and has an opening slot, which although illustrated as linear may be linear or non-linear, having a throat 38 for passing of a tubular along the slot thereby allowing the tong axis of rotation A to be selectively positioned concentric with pipe 8, provided the rotor 22 is rotated such that its throat 38 is aligned with the front openings 28 and 29 of the main drive section and back-up jaw, respectively. Center 40 of the yoke formed by the jaw and slot corresponds with axis A. The rotary jaw 22 has three gripper cylinders 44 a, 44 b, and 44 carranged radially, with approximately equal angular spacing around axis A, mounted between the two parallel horizontal planes containing rotor gears 30 aand 30 b. The number of gripper actuators, such as gripper cylinders 44 a-44 c, and associated grips or grippers may be more or less in number, so long as a tubular joint may be gripped or clamped at center opening 40.

A serpentine member such as serpentine drive belt 20 is driven by two serpentine drive motors 18, which may for example be hydraulic or electric motors. The serpentine member is mounted around so as to engage stator sprockets mounted on the stator frame. For example the stator sprockets may include drive sprockets 26 awhich are driven by serpentine drive belt 20 to collectively provide a secondary drive powering the grippers on the rotor 22. Drive sprockets 26 arotate serpentine drive belt 20 about idler sprockets 26 mounted to drive section 10. And the serpentine drive belt 20 also engages about rotor sprockets 32 a-32 fmounted on the rotor 22 as better described below. The rotor sprockets 32 aand 32 bmay be two generator drive sprockets. The rotor sprockets 32 cand 32 dmay be two pump drive sprockets. Rotor sprockets 32 eand 32 fmay be two idler sprockets. In the illustrated embodiment, which is not intended to be limiting as other embodiments discussed below would also work, the generator drive sprockets, that is, rotor sprockets 32 aand 32 b, transmit rotary power to generators 34. The pump drive sprockets, that is, rotor sprockets 32 cand 32 d, transmit rotary power to hydraulic pumps 36 by the action of serpentine drive belt 20 engaging the upper groove of rotor sprockets 32 a, 32 b, 32 cand 32 d. A synchronization belt, 28 a, connects the lower portions of the rotor sprockets 32 a-32 f. Thus as the rotor 22 rotates on axis of rotation A, even though serpentine drive belt 20 cannot extend across the throat 38 because such a blockage would restrict selective positioning of the pipe 8 along the slot into the tong, serpentine drive belt 20 wraps in a C-shape around the rotor sprockets 32 a-32 f. Serpentine drive belt 20, driven by drive sprockets 26 a, runs on pulleys 26, and on idler sprockets 26 band 26 cmounted to, so as depend downwardly from, main drive section 10. The extent of the C-shape of serpentine drive belt 20 provides for continual contact between serpentine drive belt 20 and, in this embodiment which is not intended to be limiting, a minimum of three of the rotor sprockets 32 a-32 fas the rotor rotates relative to the main drive section 10. The synchronization belt 28 amounted on the rotor maintains rotation of the individual rotor sprockets as they pass through the serpentine gap 29 seen in FIG. 4, that is, the opening between sprockets 26 band 26 c. Synchronization belt 28 asynchronizes the speed and phase of the rotation of each of the rotor sprockets 32 a-32 fto allow each of them in turn to re-engage the serpentine drive belt 20 after they are rotated across the serpentine gap 29 by the action of the rotor rotating relative to the main drive.

Idler sprocket 26 cis spring-mounted by means of resiliently biased tensioner arm 26 dto maintain minimum tension in the serpentine drive belt 20 regardless of the rotational position of the rotor 22. This is advantageous as there is a small variation in the length of the path of the serpentine drive belt 20 as the rotor 22 rotates about axis A.

The serpentine drive belt 20 maybe a toothed synchronous drive belt in order to minimize belt tension requirements. The use of a drive belt having teeth (not shown) allows for small sprocket diameters and avoids dependence on friction which could be compromised by fluid contaminants. The serpentine belt may be double-toothed (that is, have teeth on both sides) or may be single-toothed with the teeth facing inward on the inside portion of the C-shaped loop and facing outward on the outer side portion of the C-shaped loop, where the serpentine drive motors 18 and corresponding drive sprockets 26 aare positioned outside the C-shaped loop.

During operation of tong 6 the secondary drive (drive motors 18) and serpentine drive belt 20 run continuously to deliver power to the on-board pumps and generators by means of the rotor sprockets 32 a-32 d. Rotation of the rotor 22 by the operation of the primary drive acting on the pinions 56 and rotor gears 30 aand 30 bdoes not substantially affect the powering of the on-board accessories (pumps and generators) because drive belt 20 is run at substantially an order of magnitude greater speed than the speed of rotation of rotor 22. The rotation of the rotor only adds or subtracts a small amount of speed to the rotation of the rotor sprockets.

In an alternative embodiment serpentine drive belt 20 may be split into two or more separate ‘C’ sections. A plurality of separate synchronization belts may also be used instead of the single synchronization belt 28 a. Alternatively, a roller chain could be used instead of the serpentine drive belt but likely would add lubrication requirements, would be noisier and would have a shorter life. The number of rotor sprockets may be increased or decreased and the number of pulleys 26, drive sprockets 26 aand idler sprockets may also vary.

Upper rotor gear 30 aand lower rotor gear 30 bare parallel and vertically spaced apart so as to carry therebetween hydraulic pumps 36, generators 34, the rotor hydraulic system, rotor jaw electrical controls and the array of three radially disposed hydraulic gripper cylinders 44 a, 44 b, and 44 c, all of which are mounted between the upper and lower rotor gears 30 aand 30 bfor rotation as part of rotor 22 without the requirement of external power lines or hydraulic lines or the like. Thus all of these actuating accessories, which are not intended to be limiting, may be carried in the rotor 22 and powered via a nested transmission, nested in the sense that the C-shaped synchronization drive loop mounted on the rotor, exemplified by synchronization belt 28 a, is nested within so as to cooperate with the C-shaped serpentine drive loop mounted to the main drive, exemplified by serpentine drive belt 20.

Thus as used herein, a serpentine belt, such as the serpentine belt 20, driving a plurality of stator and rotor sprockets (as herein below defined), and as in the various forms of the stator and rotor sprockets found illustrated in all the figures herein, are herein referred to generically as a form of nested transmission. The nested transmission transfers power from the fixed stage to the rotational stage in a continuous fashion as, sequentially, one element after another of the rotational drive elements on the rotating stage are rotated through and across throat 38 and gap 29 allowing selective access of the tubular 8 to the center opening 40 of the stage.

Other nested transmissions as would be known to one skilled in the art are intended to be included herein so long as the drive from the fixed stage to the rotating stage is substantially continuous as the rotating stage rotates sequentially one after another of the rotatable drive elements mounted on the rotating stage across the opening into the stage which provides selective access of the tubular 8 to center opening 40.

For proper operation of the tong, it is desirable that the gripper actuators such as gripper cylinders 44 a-44 cclamp the tubular 8 substantially at, that is, at or near the rotational center axis of the tong. It can be readily seen that gripping the tubular 8 with a significant offset from the center axis would result in wobble or runout of the tubular when spinning in or out and could result in thread damage, excessive vibration, damage to the machine and inaccurate torque application.

The gripper cylinders are pinned at their outboard end to the rotor gears by means of pins 44 d. Pins 44 dreact the grip cylinder radial clamping force to the rotor gear structure 30. Pins 44 dmay include an eccentric range adjustment system.

Near the inboard end of each gripper cylinder, the lateral force due to the applied torque must be reacted to the rotary gear structure 30, without allowing excessive side loading of the internal working parts of the cylinders. For the side gripper cylinders 44 aand 44 badjacent to the throat 38, this lateral force is reacted by reaction links 44 ewhich pivotally connect the inboard end of the gripper cylinders to the rotor gear structure 30. For the rear gripper cylinder 44 c, the lateral force is reacted by cylindrical guide 44 f.

It will be appreciated that the inboard ends of side gripper cylinders 44 aand 44 bmove in an arc as the gripper cylinders are extended or retracted. For the side gripper cylinders 44 aand 44 b, the geometry of reaction links 44 eis optimized to minimize deviation from the nominal gripper cylinder radial axis over the gripping diameter range to angles typically less than one degree. The gripper cylinders 44 aand 44 bwill however swing significantly from the nominal gripper cylinder radial axis, in the order of five degrees, when they fully retract to clear the throat 38. It is an advantage of the link design that it requires less stroke to clear the throat 38 due to the swing associated with the arc of reaction links 44 e, which ultimately allows a more compact rotor and hence a more compact tong. That is, the combination of the swing in direction C with the retracting stroke in direction D results in less of a stroke length required to clear throat 38 than merely using a retraction stroke without swing. The amount of swing is governed by the radius of arc E associated with rotation of the reaction links 44 eand the length of the required stroke in direction D.

The back-up jaw section 24 as shown in FIGS. 5, 5 a, 6 and 8 is typically mounted to a tong positioning system capable of holding the tong assembly level and enabling vertical and horizontal positioning travel. The tong may be pedestal-mounted on the rig floor, mast-mounted, track-mounted on the rig floor or free hanging from the mast structure. It may also be mounted at an angle for slant drilling application or with the pipe axis horizontal.

The back-up jaw section 24 includes a parallel spaced apart array of planar jaw frames and in particular an upper backup jaw plate 48 aand a lower backup jaw plate 48 b. Backup jaw plates 48 aand 48 bmay be maintained in their parallel spaced apart aspect by structural members 48 c. Thread compensator cylinders 50 actuate so as to extend bolts 46 on rods 50 ain direction F so as to selectively adjust the vertical spacing between the rotor section 23 and the backup jaw section 24. Thus with the cylindrical threaded joint 8 aof tubular 8 held within cylinders 52 a-52 cin the backup jaw section 24 (that is with joint 8 aheld lower than shown in FIG. 3 so as to be clamped between the cylinders 52 a-52 cof the back-up jaw section 24), and as seen in FIG. 1 with threaded tapered female end or box opening upwardly in the joint 8 aheld within cylinders 52 a-52 c, as the rotor 22 is rotated relative to the fixed back-up jaw section 24 so as to rotate the box relative to the opposed facing pin, the rotor 22 and back-up jaw 48 may be drawn towards one another by the retraction of rods 50 ainto thread compensator cylinders 50 in direction F or alternately, separated from on another by the extension of rods 50 afrom cylinders 50. This action serves to compensate for the axial thread advance of the tubular as it is screwed in or out and avoids excessive axial forces on the tubular threads. The combined upward force exerted by thread compensator is controlled via the hydraulic pressure to approximately equal the weight of the upper tubular. Thus a further advantage of the invention is a reduction of tubular thread wear because the threads are “unweighted” when spinning in or out. The spacing between the back-up jaw plates 48 aand 48 bdefines a cavity in which is mounted the array of hydraulic gripper cylinders 52 a, 52 band 52 cpositioned radially about axis A and in approximately equal angular spacing. Hydraulic cylinders 52 a-52 care disposed radially inward in an arrangement corresponding to that of cylinders 44 a-44 cso that the operative ends of the cylinders 52 a-52 cwhich may be selectively actuated telescopically into the center opening 40 of the yoke so as to clamp therein a tubular 8 and in particular a lower portion of a tubular joint while an upper portion of the tubular joint is clamped within cylinders 44 a-44 cand rotated in rotary jaw section 23 in direction B about axis of rotation A relative to the fixed main drive section 10 and back-up jaw section 24.

The drive pinions 56, a minimum two but ideally four, are arranged circumferentially around the rotor 22 and intermesh and engage helical teeth with corresponding rotor gear teeth on the outer circumference of rotor gears 30 aand 30 bso that as drive pinions 56 are driven by main drive hydraulic motors 16 via gear reduction devices 16 arotor gears 30 aand 30 bare simultaneously rotatably driven (in either direction) about axis of rotation A. Pinions 56 and the corresponding rotor gear teeth are helical. Each drive pinion 56 has its rotational axis parallel to axis A and consists of an upper pinion 56 aand a lower pinion 56 b. The helix angles of the upper rotor gear 30 aand lower rotor gear 30 bare equal and opposite to ensure proper meshing torque splitting between top and bottom rotor gears. The rotor 22 is mounted within a-frame 60, wherein frame 60 may be a frame or housing. The primary drives 12 and driver 18 are mounted on top of frame 60, and back-up jaw section 24 is mounted beneath frame 60.

In the preferred embodiment, as seen in FIG. 10, the rotor hydraulic system 53 is a dual (high/low) pressure system or infinitely variable pressure system which produces high pressures (in the order of 10,000 psi) necessary for adequately gripping large and heavy-duty tubulars and for applying make-up or break-out torque, and lower pressures (2500 psi or less) to avoid crushing smaller or lighter-duty tubulars. Hydraulic pumps 36, rotationally driven as described above, are fixed-displacement, gear or variable displacement piston pumps. In the idle state, hydraulic pumps 36 charge one or more gas-filled accumulators 55 mounted in or on rotor 22 to store energy to enable rapid extension of the gripper cylinders 44 a-44 c. In this way, very fast gripping speeds may be achieved while keeping the power transmitted by the serpentine drive belt 20 drive low. That is, although the power supplied via the serpentine drive belt is small, the rotor hydraulic system must be able to intermittently supply a relatively large flowrate at low pressure for rapid advance of the gripper cylinders until they contact the tubular and also supply a low flowrate at very high pressure, in the order of 10,000 psi, to adequately grip the tubular for torquing operations.

In the schematic of the preferred rotor hydraulic system 53 of FIG. 10, system 53 has one or two gear or piston pumps 36 of relatively small capacity, within the power limitations of the serpentine drive belt. When there is no gripping demand, the pumps charge one or more gas-filled accumulators 55 to store energy for intermittent peak demands. The accumulators are optional, for the benefit of advance speed. The system is workable without accumulators provided the pumps are variable displacement. A load-sensing circuit with or without regenerative advance may also be used as would be understood by someone skilled in the art. A directional control valve 63 directs hydraulic pressure to the gripper cylinders. The directional control valve is solenoid-actuated with the solenoids controlled by the rotor control system. There are two flow paths from the directional control valve 63 to the extend side of the gripper cylinders. The first is the rapid-advance flow path which directs a large flowrate, in the order of thirty-five gallons per minute, from the pump(s) 36 and accumulator(s) 55 to the gripper cylinders at relatively low pressure, in the order of 2500 psi, for rapid extension of the gripper cylinders until they contact the tubular 8. The second is the high-pressure path in which pressure is regulated by a proportional pressure control valve 64 which is controlled by the rotary jaw control system of FIG. 11. The regulated pressure is supplied to an intensifier 65 which boosts the pressure by a factor in the order of 4:1 to supply high pressure, in the order of 10,000 psi, to the gripper cylinders. A check valve 66 prevents the high pressure fluid from flowing back into the rapid-advance low pressure flow path. The directional control valve 63 can also be solenoid actuated to direct fluid to the rod side of the gripper cylinders for retraction.

The use of high grip pressures, in the order of 10,000 psi, allows the use of compact gripper cylinders which results in a compact tong. By using the intensifier 65 to build the high grip pressure, no high pressure control valves are required.

When torquing, the control system monitors the applied torque and controls the grip pressure via proportional pressure control valve 64 at an appropriate level to avoid slippage of the tubular 8 clamped in the three gripper cylinders. The grip pressure is adaptive according to applied torque which avoids both slippage caused by inadequate pressure and crushing of the tubular 8 caused by excessive pressure.

It can be seen that in spite of the small input power, the hydraulic system can intermittently supply large flowrates for rapid grip cylinder advance and high pressures for high-torque operations. The system can regulate the grip pressure, adapting to the applied torque, for optimum gripping performance.

The rotor control system seen in FIG. 11 activates and de-activates the gripper cylinders at the operator"s discretion, regulates grip pressure and monitors system function without any power supply or control wires from or to the fixed part of the tong, because the rotor is fully rotatable and the open throat of the yoke precludes the use of any slip rings which are commonly used to transmit electrical power and control signals to a rotating element.

As seen in FIG. 11, one or two generators 34 are driven by the serpentine belt drive 20. They supply power, preferably 24 volts DC, to a programmable logic controller (PLC) 70, a radio communication link 71 and a number of sensors 73.

The radio communication link 71, which may advantageously be a Bluetooth™ device, communicates wirelessly with a similar radio communication link 72 mounted on the stationary section of the tong. The two radio communication links, 71 and 72, act as a wireless communication bridge between the main tong control system 74 and the rotor PLC 70.

The rotor PLC 70, as directed by the main tong control PLC 74, controls the output solenoids on directional control valve 63 to extend and retract the gripper cylinders 44 a-44 cand the proportional pressure control valve 64 to control the grip pressure. It also receives feedback from sensors 73 on the rotor for such parameters as (possibly including but not limited to) grip pressure, hydraulic pump pressures, grip position and hydraulic oil temperature.

For make-up of casing or some specialized drillpipes, the make-up torque specification can be much lower and the torque tolerance range smaller such that a more accurate means of torque measurement is desired, without inaccuracies due to drive friction and hydraulic motor efficiency.

In the present invention, the rotor 22, frame 60, and primary drives 12 are rotationally independent of the backup jaw section 24. As shown in FIG. 6 the rotor 22 is axially supported by the thread compensator cylinders 50 which are mounted with spherical bushings 82 at both ends so that they do not react any torque between the frame 60 and the back-up jaw section 24.

Frame torque is reacted to the backup jaw section 24 via two reaction beams 83 mounted in the backup jaw section 24 and with their top ends connected to the frame 60 via spherical bearings 84. The reaction beams 83 are free to slide vertically relative to the backup jaw section 24 in guide bushings 84 to allow for thread advance compensation travel. Guide bushings 84 restrain the reaction beams 83 laterally so that they are effectively cantilevered upward from the backup jaw section 24. The torque of the rotary jaw frame 60 is reacted at the top of the reaction beams 83.

When breaking out (unscrewing) drilling tubulars, it is often difficult to identify the axial location of the split where the two tool joints meet. It is imperative that the tong be positioned such that the split is located in the axial gap between the rotor grippers and the back-up jaw grippers. If either the rotor or the backup jaw grips across the split, the tool joint and the tong may be damaged and time will be wasted because the connection will not break out.

As shown in FIGS. 15 and 16, the actual face seam 200 between the mating connection shoulder faces 201 is only marginally visible when the connection is made up and it may be further obscured by drilling fluid. There is typically a shoulder bevel 202 adjacent to each shoulder face 201. The shoulder bevel 202 is typically machined at a 45 degree angle and has a radial dimension typically 2 to 6 mm. The two adjoining shoulder bevels 202 combine to form a connection split bevel V-groove 203. The connection split bevel V-groove 203 is usually sufficiently visible to identify the split axial location for placement of manual tongs in conventional drilling operations. But for a mechanized tong with its operator positioned several feet away from the pipe, it may be difficult to see. Furthermore, the tong may obscure the operator"s direct view of the split location. Time will be wasted in identifying the split location, traveling to it and verifying that the split is correctly located in the axial gap between the rotary and back-up jaws.

It can be seen that a reliable automated system to detect the location of the connection split would improve speed and efficiency of a mechanized tong and is mandatory for fully-automated tong operations.

A tandem configuration may be employed. That is, the optical tubular caliper can be accomplished with a pair of single point beam sensors positioned approximately 180 degrees apart, with each beam projected radially inward toward the tubular at the same elevation. Each sensor measures the radial distance to the pipe surface. The control system computes the sum of these distances. The difference between a fixed offset value and the computed sum represents the diameter of the tubular, approximately independent of the position of the tubular in the opening. The system can quickly and accurately measure the diameter of any tubular passing through the single point beams and transmit the diameter measurement to the tong control system. Furthermore, as the tong travels axially along the pipe, the tong control system can relate a series of such diameter measurements to the corresponding tong elevations as measured via the control system instrumentation described elsewhere. A diameter profile along the length can thus be created, effectively a virtual diameter versus axial position plot. The control system can compare this diameter profile to the known characteristic of the connection split bevel V-groove 203. When such a profile match is identified, the connection split is located and the corresponding tong elevation is recorded. The tong then travels the contact axial offset distance between the light band 705 axial mounting position and the desired split position between the rotary and back-up jaw grippers.

As would be known to one skilled in the art, an optical caliper system that uses a light source projecting a sheet or thin band of light instead of single point light sources may also be employed. A receiving unit senses or monitors the dimensional characteristics associated with any portion of the light which is blocked by the target object such as tool joint 8 located between the light source or sources and the receiving or sensing units. Thus, as with the use of single point light sources, the sheet or band light sources may also accurately measure the diameter of a cylindrical target object such as a tool joint 8 without any physical contact.

The control system is programmed to tune out irrelevant variations in the measured outside diameter, such as at the tool joint upset steps. It will also filter out diametral noise associated with surface irregularities such as hardbanding, tong marks or wear grooves.

It can be seen that the system can quickly and accurately locate the axial position of the connection split on the tool joint and works obtrusively and reliably, with no direct contact with the pipe. The detection system has no moving parts.

As mentioned above, the power tong according to the present invention may be mounted in many ways on the drilling rig structure, or it may also be free-hanging from a cable. The mounting method ideally allows the tong to be accurately positioned around the tubular 8 at a large range of elevations, retracts a substantial distance from well center for clearance for other well operations, parks in a small area to minimize space usage on the drilling rig floor, keeps the tong level and allows the tong to be positioned to work at multiple locations such as the mousehole which may not be in the same plane as well center and the tong park location. The mounting system could be capable of rapid movement between working and idle positions but with smooth, stable motions. It should allow the operator to command horizontal or vertical movements or a combination.

Numerous tong or wrench mounting mechanisms exist in the industry. Most are Cartesian (horizontal/vertical) manipulators employing tracks, slides or parallelogram linkages for each motion axis. These mechanisms are simple to control because they directly actuate on the horizontal and vertical axes but they typically have a small range of motion which limits tong functionality and restricts mounting location on the drill floor. They have a large parked footprint which consumes scarce rig floor space and interferes with other well operations. And they have little or no capability to react torque applied to the tong or wrench by a top drive in the rig.

Thus in one preferred embodiment, a tong is preferably mounted on a manipulator 99 as shown in FIGS. 12aand 12b. A slewing base 100 is mounted to the drilling rig floor. A hydraulic slewing motor 101, via a gear reduction, can turn the slewing base up to three hundred and sixty degrees about the vertical axis. The internal bearings of the slewing base can support the weight and overturning moments of the manipulator structure and the tong. Slewing motor 101 may alternatively be electric, pneumatic or manually actuated.

The tong is pivotally mounted at the end of boom 103. The angle of the tong relative to boom 103 is controlled by linear actuator(s) 106. The inclination of the tong is monitored by angle sensor 109.

The actuators 104, 105 and 106 can be single or paired and are preferably hydraulic cylinders but could be screw actuators drive by electric or hydraulic motors or any other form of linear actuators. Alternatively, rotary actuators at the pivot axes could be used.

Angle sensors 107, 108 and 109 are preferably inclination sensors rigidly mounted to the structure which measure the angular displacement from a gravitational reference. Shaft-driven angle transducers could also be used. Position feedback could also be achieved using linear displacement transducers in or adjacent to actuators 104, 105 and 106.

Various possible tong positions are selectively positioned between the extended operating position illustrated in FIG. 12aand the parked position of FIG. 12b. It can be seen that the manipulator 99 provides a large range of motion but can park the tong 6 with a small footprint.

The booms have significant lateral and torsional stiffness. This is advantageous over prior systems because the structure can react torque applied to the tong by a top drive in the rig, such as for back-up of drilling connection make-up. The tong can also apply torque to make up a bit restrained in the rig"s rotary table.

Manipulator 99 may be fully functional with manual controls for each of the four output actuators (slewing motor 101 and linear actuators 104, 105 and 106). However, it preferably has a control system as described below in which horizontal and vertical rates of tong travel are controlled in direct proportion to horizontal and vertical velocity commands by the operator and the tong is automatically kept level. The control system may also include the capability of optimized travel, including acceleration and deceleration control, to pre-defined locations.

The tong"s vertical and radial positions (relative to the slewing base) at any time are computed by the programmable logic control (PLC) 112 geometric constants and the boom 102 and 103 angles measured by angle sensors 107 and 108. The slewing orientation is measured preferably by an encoder 110 on the slewing drive. The tong"s three-dimensional position is therefore monitored at all times.

The preferred operators control console has a single 3-axis joystick 111 for control of the manipulator. The x-axis of joystick 111 controls the horizontal motions of the tong, the y-axis of the joystick 111 controls the vertical motions of the tong and the z-axis (handle twist) of the joystick controls the slewing motions of the assembly. The joystick commands may be discrete ON/OFF but are preferably analog/proportional on the x and y axes for finer control.

Horizontal motion of the tong requires movement of both boom 102 and boom 103, accomplished via linear actuators 104 and 105. The required output velocity signals to each of linear actuators 104 and 105 are computed in the PLC 112 in order to achieve the desired horizontal command velocity from the x-axis of joystick 111.

Similarly, vertical motion of the tong requires movement of both boom 102 and boom 103, accomplished via linear actuators 104 and 105. The required output velocity signals to each of linear actuators 104 and 105 are computed in the PLC 112 in order to achieve the desired vertical command velocity from the y-axis of joystick 111.

A feedback loop may optionally be employed in which, for each motion axis (horizontal/vertical) the actual velocity (rate of change of position over time) is periodically compared to the joystick velocity command and any necessary adjustment made. This feedback is particularly useful when the operator commands pure horizontal or pure vertical motion at the joystick. If the operator commands a pure vertical motion, for example, any inadvertent deviation from the vertical axis will be detected and adjustments made to the velocity signals to linear actuators 104 and 105 to tune it back to a pure vertical motion.

The control system may also have capability for automated travel to pre-defined locations such as well center, mousehole and parked position. When the operator commands automated travel to a desired pre-defined target location, the control system control acceleration, travel velocity, deceleration and landing speed for both horizontal and vertical axes to achieve optimum travel to the target, with minimum elapsed time and smooth, controlled motion.

The alternative embodiments of FIGS. 18 and 19, which are not intended to be limiting, but which are, rather, intended to exemplify that the serpentine drive and the separate synchronization by a synchronizer, which allows the free unencumbered rotation of the rotor without blocking of the rotor"s throat, may be accomplished using various geometric arrangements of serpentine drive and synchronization as part of a nested transmission which may for example employ a plurality of drive and idler sprockets.

In particular, in FIG. 18, serpentine drive belt 20′ is driven by at least one serpentine drive motor which may for example be at least one hydraulic motor. The serpentine drive motor drives at least one drive sprocket 26 a′ which, as before, provide a secondary drive via a plurality of rotor or satellite sprockets 32′ on rotor 22, and also drives a synchronizer between sprockets 32′ and a coupling such as pumps or generators, or a mechanical mechanism powering gripper actuators and corresponding grippers 44′, or directly acting on grippers 44′, on the rotor 22. As illustrated by way of example, a first drive stator sprocket 26 a′ rotates serpentine drive belt 20′ about a second stator sprocket which may be a second drive sprocket 26 a′ or an idler sprocket 26′ mounted to drive section 10. A tensioner 27 such as a tensioning idler sprocket, which may be considered a third stator sprocket, may be mounted to frame 60 so as to be resiliently biased against serpentine drive belt 20′ to tension the drive belt. A pair of satellite or rotor sprockets 32′ are mounted on the rotor 22. As seen in FIG. 18, the first and second stator sprockets are mounted on substantially opposite sides of the rotor. As the term is used herein, the first and second stator sprockets are arrayed substantially around the rotor. Third, fourth, etc stator sprockets would thus not have to be on one side or the other of the rotor, but would form part of the array of stator sprockets arrayed substantially around the rotor.

As rotor 22 rotates, sequentially at least one satellite sprocket 32′ will detach from engagement with drive belt 20′ and rotate across the gap between sprockets 26 a′ and 26′. As that sprocket crosses the gap it is disengaged from drive belt 20′, during which time at least one remaining rotor sprocket remains engaged with drive belt 20′. All sprockets 32′ continue to rotate synchronously as driven simultaneously by synchronization belt 28 a′ The process repeats in succession for each rotor sprocket 32′ as each of the rotor sprockets 32′ passes across the gap between sprockets 26′ and 26 a′.

The rotor sprockets 32′ drive for example one or more on-board generators and/or one or more on-board hydraulic pumps (not shown in FIGS. 18 and 19). Synchronization belt 28 a′ may connect the lower or upper portions of the rotor sprockets 32′, with the serpentine drive belt 20′ then connecting the upper or lower portions of the rotor sprockets 32′ respectively. Thus as rotor 22 rotates about axis of rotation A even though serpentine drive belt 20′ cannot extend across the opening throat 38 because such a blockage would restrict selective positioning of the pipe 8 along the slot into the tong, serpentine drive belt 20′ wraps around or reaves so as to remain at all times in contact with at least one of rotor sprockets 32′. Drive sprockets 26 a′ are mounted to, so as to for example depend downwardly from, main drive section 10. As seen in FIG. 18a, the deflection of serpentine drive belt 20′ by the rotation of rotor sprockets 32′ provides for continual contact between serpentine drive belt 20′ and a minimum of one of the rotor sprockets as the rotor 22 rotates relative to the main drive section 10, wherein the deflection of serpentine drive belt 20′ tensions the portion of drive belt 20′ where it contacts tensioner 27. Upon return of the rotor sprockets to the position of FIG. 18, tensioner 27 takes up the slack in the drive belt 20′.

Tensioner 27 may be an idler sprocket, which may be spring-mounted or otherwise have a resilient biasing means to maintain minimum required tension in the serpentine drive belt 20′ regardless of the rotational position of rotor 22. This is advantageous as there is a small variation in the length of the path of the serpentine drive belt 20′ as rotor 22 rotates about axis A. Alternatively, other stator sprockets or rotor sprockets may be resiliently biased to maintain tension in the serpentine drive belt 20′.

Although in the illustrations, the synchronizer of the rotor sprockets 32′ is shown as a belt, one skilled in the art would appreciate that other forms of synchronization would also work and are intended to fall within the intended meaning of the word synchronizer. For example a synchronizer may also include the use of gears, a flexible shaft, a rigid shaft with right-angle gearboxes, a hydraulic or other fluid system to synchronize the movement of the rotor sprockets.

The forms of coupling are also not intended to be limited to only those illustrated or discussed elsewhere herein, as for example the coupling may include a mechanical coupling or linkage between the rotor sprockets and grippers. For example, the rotor sprockets may directly or indirectly drive worm gear reducers which drive screws which grip pipe 8, in which case the serpentine, such as drive belt 20′, would operate to directly cause the screws to clamp or unclamp the tubular. The screws when tightening on to a tubular would, for example, be turned until they come to a stop against the tubular joint, at which time the serpentine would stop turning as the serpentine drive stalls and thereafter would turn to match the rotation of the rotor in either direction to maintain approximately constant tension on the serpentine drive belt.

As seen in FIG. 19a, rotor 22, the rotor sprockets 32′, and one or more energy coupling 45 may be mounted within a rotary jaw frame 47 on, for example, bushings 49. Energy couplings 45 couple the energy being transmitted from the serpentine to the rotor sprockets 32′, and couples the energy to the grippers 44′ or gripper actuators (which in turn actuate the grippers). As stated above, energy couplings 45 may include pumps, generators, or mechanical drives such as direct mechanical linkages, but may also include the use of energy storage such as, without intending to be limiting, gas accumulators, batteries, capacitors, flywheels, which may then power actuation of the grippers when needed.

The serpentine drive belt 20 or 20′ although illustrated as a belt, is intended to include within the meaning of the word serpentine, and as would be known to one skilled in the art, any suitable flexible member, for instance, a belt or chain or cable, with or without teeth to engage the stator and rotor sprockets, or other flexible or deformable member for transferring mechanical energy from the stator sprockets to the rotor sprockets.

The grip or grippers 44 or 44′ may, although discussed and illustrated herein as being hydraulically actuated, include as within the intended meaning of the word grip or gripper; mechanical, fluid such as hydraulic, or electric actuation, with the corresponding actuators including such as screws, pistons, wedges, eccentrics or cams.

The reference herein to sprockets such as the stator or rotor sprockets may, as would be known to one skilled in the art, include, and are intended to include the use of pulleys, sheaves, wheels, etc.

The present invention relates to an oil field apparatus or tool, and more particularly relates to an improved power tong. Even more particularly, the present invention related to an improved power tong providing jaw assemblies which are rotationally mounted within the respective jaw carriages and are powered by hydraulic cylinders. Even more particularly, extending jaw chambers are provided which allow the hydraulic cylinders to be moved between left and right positions which combined with an inverting of the respective jaw assembly different rotational directions to each jaw assembly.

In the oil field and in oil/gas drilling, there is often utilized a "power tong" for making up and breaking up sections of drill pipe, casing, or other like piping assemblies which are generally made up into strings from a plurality of joints. Many of these power tongs are in use which quickly make or break the desired connection using power supplied by an electric or hydraulic motor, for example. In general, power tongs of this type have clutch, drag or brake assembly which transforms rotary power through a gear reduction system into gripping power through a cam mechanism, thus allowing the pipe to be gripped at the joint and the desired torque applied. Power tongs of this type are known.

In U.S. Pat. No. 2,862,690 issued to James C. Masou, which provides for a power driven device for rotating piping or casing utilizing a series of endless belt in the rotating of the pipes.

In U.S. Pat. No. 3,793,913 issued to Carl A. Wilms, there is provided a power tong for making up and breaking up pipe adapted with a reverse stop means.

In U.S. Pat. No. 3,144,794 issued to J. L. Foster entitled "Power Driven Sucker Rod Wrench," relates to a power actuated sucker rod tong or wrench, and more particularly to a wrench mechanism for connecting and disconnecting the screw threaded joints of pump rods.

U.S. Pat. No. 4,084,453 issued to E. L. Eckel, entitled "Power Tong" includes a power tong which has a frame and pipe gripping mechanism associated with a throat at one end of the frame wherein power is transmitted to the pipe gripping mechanism from a power unit through a drive train.

U.S. Pat. No. 3,541,897 issued to H. D. Horton entitled "Power Tubing Tongs," wherein is included an external housing having a bull gear assembly disposed for the major circumferential difference thereby with the external housing being adapted to receive a removable internal jaw section therein.

U.S. Pat. No. 3,892,148 issued to Mark H. Wiley, entitled "Adjustable Power Spinning Tongs" provides an apparatus which involves a power spinning tong of the type having rollers which grip the pipe and some of its rollers are rotatable to drive the pipe rotatively, the rollers being revolvable on lever arms that can be opened to allow the tong to be applied to and removed from the pipe.

U.S. Pat. No. 4,005,621 issued to J. W. Turner, Jr. and Russell A. McLaughlin entitled "Drilling Tong," which utilizes an open head tong of the type utilized to handle large diameter work pieces, such as drill pipe and casing for oil field application and including means to adjustably engage peripheral portions of such work pieces.

U.S. Pat. No. 4,060,014 issued to John W. Turner, Jr. entitled "Power Tong" provides for an open head power tong for use in making up and breaking up joints of varying diameter such as drill pipe joints which provides for bidirectional operation with the tong housing remaining in the same position.

U.S. Pat. No. 3,021,739 issued to J. F. Grundmann entitled "Hydraulically Controled and Operated Power Tong," which includes a rotatably mounted head portion having an opening in which a cylindrical member may be positioned coincident with the axis of rotation of the head portion and there is a power means operable to rotate said head portion, said gripping members being actuatable into gripping engagement and out of gripping engagment.

U.S. Pat. No. 2,741,460 issued to R. I. Gardner entitled "Power Tongs and Control System Therefor," which provides for a power wrench including a housing which provides an annular stator, an annular rotor carrying a suitable pipe gripping structure being disposed within the annular stator and being rotatable about the axis thereof.

U.S. Pat. No. 2,703,221 issued to R. I. Gardner entitled "Power Tong," which is essentially the same apparatus as the previous patent to the same inventor.

Most prior art devices as is evidenced from the prior arts patents cited are extremely complex in construction and are difficult and/or impossible to replace in the field should the need arise. Further, they are generally constructed so that there are numerous moving parts and are drive train apparatus, gears, etc. which the use of oil field work require immediate attention should a breakdown occur which indeed does happen very often.

The present invention provides an improved power tong apparatus which would comprise a housing having a U-shaped vertical slot with a vertical axis which would normally be occupied by a pair of pipe lengths to be assembled or disassembled as in oil field work. The apparatus would also have a pair of jaw assemblies which would be movably mounted on a housing and adapted with a pair of oppositely oriented hydraulic cylinders which would be connected respectively to the pair of jaw assemblies and produce opposite rotational motion of each. Each jaw assembly would be powered during the operation by one of said cylinders to a first pipe gripping position and thereafter to a second pipe rotating position. In the embodiment, the pair of jaw assemblies would be cylindrical and are mounted within the cylindrical recesses provided respectively in the upper and lower portions of the housing. A pair of upper laterally extending chambers and a pair of lower laterally extending chambers would further comprise the housing.

Therefore, it is an object of the present invention to provide an improved power tong apparatus which is adapted for receiving pipe lengths for assembling and disassembling.

It is further an object of the present invention to provide a power tong which would be adapted with oppositely oriented hydraulic cylinders being connected to a pair of jaw assemblies and producing opposite rotational motion of each, therefore enabling assemblage and disassemblage of pipe lengths.

It is a further object of the present invention to provide a power tong where the pair of jaw assemblies are cylindrical and mounted within cylindrical recesses respectively in the upper and lower portions of the housing.

It is another object of the present invention to provide a power tong which is of simplified construction for hydraulically driven jaws for assembling and disassembling sections of pipe in the oil field industry.

FIG. 1 is an exploded perspective view of the power tong apparatus of the preferred embodiment of the apparatus of the present invention illustrating the body, hydraulic cylinder an anchor plate portions thereof;

FIG. 4 is a top view of the jaw assembly portion of the preferred embodiment of the apparatus of the present invention with a section of drill pipe being schematically illustrated;

FIG. 6 is a detailed perspective view of the movable jaw and jaw carriage portions of the preferred embodiment of the apparatus of the present invention;

FIG. 8 is a phantom front view of the preferred embodiment of the apparatus of the present invention illustrating the housing in phantom lines, and the upper and lower jaw assembly portions while gripping two connected joints of drill pipes;

FIG. 1 best shows the preferred embodiment of the apparatus of the present invention as generally comprising housing 12, to which are attached in the preferred embodiment a pair of hydraulic cylinders 60 attached respectively to anchor plates 33-36 at one end portion thereof and to jaw assemblies 40 as will be described in more fully hereinafter. Housing 12 provides an upper 21 and a lower 22 jaw assembly carriage which are recesses provided respectively in the upper and lower portions of body 12 and which movably house respectively a jaw assembly 40 during operation. Cover plates 30, 31 are affixed by bolting, for example, using bolts B after each jaw assembly 40 has been placed into its respective jaw assembly carriage 21, 22.

FIGS. 7-12 best illustrate the particular construction of housing 12. Each housing 12 provides a vertically extending U-shaped recess 20 which allows the entrance of a length or a pair of joints of drill pipe 63, 64 there into.

Body 12 provides also four laterally extending chambers 13-16, each chamber providing its respective inner chamber bore 23-26. Chamber bores 23-26 communicate respectively with U-shaped slot 20 on the interior portion of housing 12 and are open externally. At such external openings, a plurality of anchor plates 33-36 are provided to correspond with the four laterally extending chambers 13-16. In the drawings, four anchor plates 33, 34, 35 and 36 are provided which bolt, for example, respectively to chambers 13-16 as can be seen in the drawings. In FIG. 1, anchor plates 33-34 are shown in an exploded view each providing bolts B as well as peripheral openings in each anchor plate through which bolts B will be inserted upon assembly. Receptive threaded sockets would be provided by milling such female threaded sockets into the respective chambers 13-16 so that bolts B could be tapped directly into each respective chamber and fasten the respective anchor plate 33-36 to the respective laterally extending chamber 13-16. It should be understood at this point, that each anchor plate 33-36 will be called upon to act as an anchor for a hydraulic cylinder 60 which will bear respectively against an anchor plate 33-36 and jaw assembly 40 to generate the necessary compressive force to operate power tong 10 and to take apart and put together joints of drill pipe as schematically shown in FIG. 8 by arrows 66.

Each anchor plate 33-36 provides a pair of brackets which will allow one end portion of hydraulic cylinder 60 to be attached thereto by pinning, for example, as shown in FIG. 1. In FIG. 7, a pair of brackets can be seen provided with each anchor plate 33-36 with such pairs of brackets being designated by the numerals 43-46 in FIG. 7.

The front portion of housing 12 provides handles LH and RH which handles aide in the manipulation of housing 12 when it is supported, for example, by a crane, or lift or the like. Handles LH, RH would merely be for lateraly movement of body 12 and not for its support. A suitable crane or the like would be required to support housing 12 during operation.

FIG. 12 also illustrates hydraulic line receiving ports 73-76, which accommodate the hydraulic lines 17 (shown in FIG. 1) into the power tong assembly for operation of the hydraulic cylinder 60.

FIGS. 4-6 show with particularity the construction of jaw assembly 40. It should be appreciated that two jaw assemblies will be required, an upper jaw assembly and a lower jaw assembly each designated in the drawing as 40. These jaw assemblies will be mounted respectively at the upper and lower portion of housing 12 respectively in upper jaw assembly carriage 21 and lower jaw assembly carriage 22. Carriage 21 in the preferred embodiment is comprised of a lower annular support surface 210 and a generally cylindrical side wall 212. Once the respective jaw assembly 40 is placed in its assembly carriage 21, 22 it rests as best seen in FIG. 1 upon surface 210 being surrounded by side wall 212. Cover plate 30 would then be bolted in position by the