power tong hand free sample

Well pipe is made up by supporting a lower pipe section ("joint") in the well and then threading an upper joint onto it by means of a fluid-driven power tongs. The pipe assembly is lowered as new joints are added, down to depths of several miles. Threaded well joint connections, in order to seal properly and to have maximum tensile strength, must be accurately tighted ("made-up" in the trade) to a design torque ("make-up torque") specified by the pipe manufacture. The design torque must not be exceeded, since galling or breakage of the pipe threads may result. This is particularly true with pipe joint materials chosen for considerations other than strength, e.g. corrosion resistance and impermeability. Such materials are not only relatively soft--they can be quite expensive. In one recent case, 1000 joints (each thirty-three feet long) were removed from a well. Every joint had thread damage due to overtorquing and was considered scrap. This was pipe originally costing $2500 per joint. The importance of controlling the torque applied by the power tongs to the pipe can thus be appreciated, and in fact it is a requirement on many jobs that a running record of maximum torque at each joint be kept. (Various systems exist for making torque records during make-up, including applicant"s system described in copending application Ser. Nos. 487,048.Iadd., now U.S. Pat. No. 4,552,041, .Iaddend.and 526,611.Iadd., now abandoned.Iaddend..) Despite the existence of accurate torque recording systems, improper torquing continues to occur. The industry still seeks a system that will positively prevent thread damage from overtorquing.

The crossed thread problem is aggravated by violent or jerky movement of the tongs when power is first applied. The tongs frequently do not work smoothly--and are hard to control--at very low speeds. Also, the snub line, initially slack, tends to snap tight when power is first applied. These conditions make it difficult to control and/or record torque at the instant tongs operation begins, so that thread damage can occur even if a low-level torque limiter is used.

I have found that the above problems can be overcome by substantially increasing the overall gear reduction ratio within the tongs, for example, by a factor of five. The tongs jaw speed is correspondingly reduced, avoiding the problems of irregular start-up. This speed reduction is advantageously combined with a two-stage torque limiter system for (a) preventing the application of substantial torque during the initial phase of makeup and (b) limiting the maximum torque that the tongs can produce at the final makeup stage.

This invention is particularly useful for assembling connections of the type shown in U.S. Pat. No. 3,359,013. This type of connection has one or more annular shoulders associated with each thread, for engaging a corresponding shoulder on the mating piece. The threads themselves, being of a non-interference type, do not provide sealing, which occurs entirely at the contacting shoulders. During assembly, the pipe can be rotated by hand until shoulder contact occurs; thereafter only minor rotation, perhaps one-eighth turn, is needed to fully make up the connection. During this stage the required torque rises rapidly from hand-tight to, for example, 2000 ft. lbs. Comparative charts of torque T vs. turns N for conventional and shouldered threads are shown in FIGS. 3a and 3b. Plainly, the more rapid torque increase rate of the shouldered connection calls for a torque controller having fast response.

Torque is automatically controlled during both tightening stages. In the initial stage, thread damage in the event of cross-threading is prevented by maintaining a very low torque cutoff point. In the final tightening stage, galling and breaking of threads is prevented by slowly turning the pipe 4 and automatically disabling the pipe tongs when a predetermined torque level is reached.

Another object is to enable the operator to control both the maximum obtainable tongs torque and the tongs speed during the final stage of connection makeup.

The preferred embodiment of the invention is illustrated diagrammatically in FIG. 1. The major components are a conventional hydraulic power unit A, a power tongs T driven by fluid from the power unit, a tongs sensor/recorder B and a torque control module C.

The power unit A, as shown in FIG. 1, comprises an internal combustion engine 10, a hydraulic pump 12 driven thereby, a pressure regulator 14 downstream of the pump, and a fluid reservoir 16 upstream of the pump. In operation, the power unit delivers pressurized fluid through high pressure line 20, and receives fluid exhausted by the tongs via return line 22.

The tongs T have both conventional and novel aspects. A conventional body 30 supports rotary jaws 32 adapted to engage the outside diameter of a pipe P. The body houses a gear train, details of which are not shown, including a two- or multi-speed transmission. Tongs of this type are well known. The transmission is manually shifted by means of a gear selector 34, with the ratio between high and low speeds being on the order of 4:1. The tongs are powered by a hydraulic motor 36 driving through two planetary gear reduction units 38 and 40 (FIG. 2) in series, each having about 51/2:1 reduction ratio. Further speed reduction is provided by spur gearing within the tongs body, so that the overall reduction is about 60:1 in high gear and 250:1 in low gear.

The tongs motor 36 is driven by fluid from the power unit, which enters the tongs via inlet line 42 and returns via exhaust line 44. A reversing shunt valve 46 on the tongs connected between the inlet and exhaust lines allows fluid to bypass the motor entirely when the valve is open. The shunt valve, normally open, may be moved to drive the tongs motor in either direction by a manual throttle handle 50 accessible to operator.

Any torque applied to the pipe P by the tongs creates a reaction torque that tends to rotate the tongs around the pipe. This tendency is restrained by a snub line 54 connected between a stationary object and the tongs body along a tangent line as shown. The snub line 54 includes two load transducers in series for monitoring tongs torque. The first transducer 56 is an on-off pneumatic valve having adjustable spring bias. This valve opens when tension corresponding to a preset "hand-tight" torque in the rage of 0-50 ft. lb. is applied. A manual override valve 58 in series with the first transducer 56 provides means by which the operator can disable the hand-tight torque control system, if desired.

An important feature of the invention is the on-off valve 60 mechanically connected via linkage 62 to the gear selector lever 34, such that the valve 60 is open only when the tongs are in their high-speed range, as shown. As a result, the transducer 56 performs its torque limiting function only during the initial, high speed phase .[.of.]. .Iadd.to .Iaddend.tongs operation, and does not interfere with high torque operation during the final stage of makeup.

The snub line 54 also has mounted therein a second load transducer 61 which communicates via conduit 62 with a Bourdon tube 64 supported within the recorder module B. The free end of the Bourdon tube is connected to the stylus 65 of a conventional chart recorder 66 having a spring-driven motor 68. The stylus has a small blade 70 attached thereto capable of interrupting flow of air through a normally open air gap unit 72, which can be moved toward or away from the stylus by means of threaded support 74 to adjust the threshold makeup torque. The air gap unit is supplied with air regulated to a very low pressure, e.g. 5 psi, so as not to affect stylus position. The output signal is amplified and inverted by the pneumatic logic unit 76, details of which are shown in applicant"s copending application Ser. No. 526,611, the disclosure of which is incorporated by reference. The logic unit 76 thus generates a high pressure output in conduit 78--provided the second override valve 80 is open--when the stylus blade 70 enters the air gap as the tongs reach maximum makeup torque. Conduit 78 leads to one input of a two-way check valve 82, the other input of which is from the hand-tight transducer 56. A high pressure at either input is thus delivered via conduit 84 to a second pneumatically actuated shunt valve 86, which when actuated halts tongs operation.

The valve 60, first transducer 56 and shunt valve 86 together provide means for halting tongs operation at a preset hand-tight torque level. Lever 34, linkage 62 and valve 60 function as means for disabling this first means. This general terminology is used in the claims below. The second transducer 61, recording module B and shunt valve 86 comprise means for halting tongs operation at a preset .[.fuel.]. .Iadd.full .Iaddend.makeup torque level.

Turning to the torque control module C, it can be seen that the tongs exhaust line 44 is directly connected to return line 22, while the tongs inlet line 42 is variably regulated as to both pressure and flow rate. Fluid entering the module from supply line 20 first encounters a three-way pneumatically actuated valve 88, whose position is ultimately determined by the position of gear selector lever 34. In high gear, fluid is directed to line 90, which is regulated to very low pressure in the range of 25-200 psi by the adjustable pressure regulator 92, which relieves excess pressure back to the return line 22.

When the tongs are in low gear, and valve 60 blocks delivery of control pressure to valve 88, the supply line 20 is connected to a unregulated high pressure line 94 having therein a manually adjustable flow rate controller 96. This valve enables the operator to control maximum tongs speed during the final makeup stage, without affecting the maximum torque obtainable. The variable restriction 98 shunting supply and return lines 20 and 22, on the other hand, enables the operator to limit the pressure deliverable to the tongs. Maximum tongs torque can thus be limited, providing a measure of redundancy over the automatic control system defined between transducer 61 and shunt valve 86.

In operation, as a drill string is supported by slips or the like on a rig deck, a new joint is brought into mating contact with the next lower joint, Once the threads are engaged, the tongs operator, having placed the gear selector in high, throws throttle 50, thereby closing shunt valve 46 to apply regulated pressure from line 42 to the tongs motor, which rotates the pipe slowly at about twenty rpm hand tight. Note that compressed air passes through valve 60 to valve 88, which directs all hydraulic fluid flow past low pressure regulator 92, substantially limiting the torque capacity of the tongs. Furthermore, air pressure is supplied to first transducer 56. When the preset threshold snub line load is reached, air passes through transducer 56, override valve 58 and check valve 82 to open the second shunt valve 86 and automatically stop the tongs. In the event of improper thread engagement, this sequence of events disables the tongs before thread damage occurs, regardless of the operator"s attentiveness or reaction time, and corrective action can be taken. It is not necessary, with this system, to count turns of pipe rotation or the like.

Provided the connection is properly run up to hand tight, and the operator can see that the sealing shoulders have come into contact, he then places the gear selector lever in "low", automatically obstructing the high pressure control signal to the second shunt valve 86, which thereupon closes so that tongs operation can be resumed. Simultaneously, the valve 88 reverses position.[.,.]. so that fluid at full pressure is delivered to the tongs. Now developing high torque, the tongs rotate the pipe very slowly--at five rpm or less, and this speed can be regulated by means of valve 96--until the desired makeup torque is reached. At the present cutoff torque level, stylus blade 70 enters the air gap unit, causing logic unit 76 to deliver a high pressure signal to open the second shunt valve 86, thereby automatically halting tongs operation.

The present invention relates to open-head power tongs used in drilling operations, and more particularly, is directed to an improved means of actuating and deactuating the operation of the power tong drive means in response to the opened and closed positions of an access door.

As well known in the drilling industry, power tongs are employed in making-up and breaking-out operations of casings, tubings, rods, pipes and the like. More particularly, power tongs are used to grip and rotate lengths of drill pipe or the like to connect or join several lengths of pipe together to thereby form a drill string in a make-up operation, and in the alternative, to grip and rotate a length of drill pipe to disconnect it from the drill string in a break-out operation.

One type of power tong commonly used today is the open-head tong, such as the one shown and described in U.S. Pat. No. 4,060,014. The open-head tong has a bifrucated frame defining a central opening and a side opening communicating with the central opening for the passing therethrough of a drill pipe or the like. Due to the extreme costs of drilling, open-head tongs have become very popular, in that, they can easily and readily be moved into and out of an operative position when they are needed in the making up and breaking out of drill strings.

In operation, the open-head power tong exerts large rotational torques on the drill pipes, usually the larger the tong, the larger the torque output. Due to these large torque outputs and the resulting forces generated therefrom, the open-head tongs have been provided with an access door that bridges the gap between the bifrucated ends of the tong. The primary purpose of such an access door is to strengthen the tong structure so as to prevent, during the operation of the tong, the bifrucated ends from separating or springing apart, which not only results in damage to the tong, but could also inflict injury to the operating personnel. The access door, in addition to providing structural rigidity to the tong, also provides the operator with safety in bodily protecting him from the rotating pipe gripping and engaging jaws.

Such access doors perform very satisfactorily in providing structural rigidity to the tong and do provide protection to the operators from the rotating components of the tong when the door is properly latched in position during the make-up and break-out operations; however, in an effort to save time, operators have been known to operate the tong with the access door open, and in some instances, the operators have even removed the access door from the tong. Such operator"s carelessness not only causes costly structural damage to the tong, but also results in personal injury to the operator.

In U.S. Pat. No. 2,705,614 there is shown an open-head power tong having an automatic hydraulically powered access door, operably interconnected to the hydraulic cylinders that actuate the jaw gripping mechanism, which must be closed before the jaws can be actuated so as to rotate a drill pipe. Such door interlock mechanism has been specifically designed for the type of tong disclosed and is not readily adaptable to other types of power tongs, such as the one shown in the above-mentioned U.S. Pat. No. 4,060,014. Further, the hydraulic circuitry that is involved with such a powered access door is not only complicated, having expensive components, but is also, costly to maintain and repair. Still further, such door interlock mechanism does not provide adequate safety to an operator, in that, although the operator is protected from the pipe gripping and engaging mechanism when the door is closed, he is also subjected to the risk of having the power operated door being automatically swung into him as it is being closed, thus, creating a potentially dangerous and unsafe condition under which the operator must work.

The present invention obviates the problems experienced with access doors and disadvantages associated with the prior art door-interlock mechanisms by providing, as one of its principle objects, an improved door-interlock mechanism for an open-head power tong that ensures the access door is in a closed position before the tong can be operated, thereby preventing possible structural damage to the tong from operating the tong with the door open, as well as, preventing personal injury to the operators by protecting them from the various rotating components of the tong.

Another object of the present invention is to provide a door-interlock mechanism for an open-head power tong that is simple in structure and adaptable to all types of open-head power tongs.

Accordingly, the present invention, sets forth in an open-head power tong having an access door mounted on the tong and moveable between opened and closed positions, an improved door-interlock mechanism that includes means for controlling the operation of the tong in response to the opened and closed position of the door. More particularly, the control means preferably includes a pneumatic contact valve interconnected with a pneumatically piloted diverter valve operably associated with the power means of the tong such that the power means is placed in either an operative or inoperative condition in response to respective closed and opened positions of the door. Specifically, the pneumatic contact valve is so positioned in the vicinity of the side opening that the door, in its closed position, engages the contact valve thereby actuating the diverter valve to permit operation of the power means, and when, the door is moved from its closed position out of engagement with the contact valve, the contact valve causes the diverter valve to deactuate the power means, thus stopping the operation thereof.

FIG. 1 is a top plan view of an open-head power tong incorporating the improved door-interlock mechanism of the present invention with the access door being in its closed position in engagement with the contact valve which actuates the diverter valve.

FIG. 2 is a diagrammatic fragmentary view of the power tong showing the side edge portion of the access door with the door latch removed and with the contact valve being in disengagement with the door which is partly open.

Referring to the drawings, and particularly, to FIG. 1, there is shown, for illustration purposes only, an open-head power tong, being generally indicated by the numeral 10, incorporating the principles of the present invention. The tong illustrated in FIG. 1 is of the type shown and described in U.S. Pat. No. 4,060,014, and thus, for the sake of brevity, since the tong itself forms no part of this invention, only a brief description of the tong will follow.

Briefly, as best seen in FIG. 1, the power tong 10 is comprised of a bifrucated frame structure 12 defining a central drill pipe receiving opening, and a side opening that communicates to the central opening for laterally passing a drill pipe therewithin. Rotatably supported within the frame structure 12 is a pipe engaging and gripping means that includes jaws 14 that swing into and out of the central opening for gripping and rotating a drill pipe disposed within the central opening during make-up and break-out operations of a drill string. The pipe engaging and gripping means with its associated jaws 14 are rotatably driven through a suitable drive train (not shown) by power means such as the hydraulic motor 16 which receives fluid under pressure from a suitable hydraulic pump (not shown) and through a hydraulic control valve 17. The valve 17 is conventional, being moveable between three spool positions; one position being such that the fluid drives the motor in a forward clockwise direction, another position being such that the hydraulic fluid drives the motor in a reverse counterclockwise direction, and the third position being a neutral position wherein fluid passes through the valve to the return line that returns the fluid to a reservoir (not shown) for recirculation thereof.

Also supported on the frame structure 12 is an access door 18, adapted to span or bridge the access opening defined between the bifrucated end portions so as to provide structural rigidity to the power tong 10, as well as, to protect the operator from the various moving components, such as the jaws 14. One end of the access door 18 is hinged to an end of one of the frame bifrucations by a pivot pin 20 whereas the free end of the door is provided with a self-latching arm 22 that engages a latch member 24 mounted on the other bifrucation so as to positively latch the door when it is closed. The door and the door latching mechanism are of the type shown and described in a pending U.S. application, bearing U.S. Ser. No. 791,752; filed Apr. 28, 1977; and entitled TONG LOCKING MECHANISM. The door and the latching mechanism forms no part of this invention and thus a further description will not be given.

To ensure that the tong 10 is only operated when the door 18 is closed, closing the access opening, the tong 10 is provided with an interlock mechanism which basically includes a contact valve 26, engageable by the door 18, and a hydraulic diverter valve 28, operably associated with the hydraulic motor 16 so as to permit flow of hydraulic fluid to the motor, or, in the alternative position, to bypass the flow of hydraulic fluid around the motor.

Now turning to FIG. 3 which schematically represents the various operating components as well as the hydraulic and pneumatic circuitry associated therewith, the operation of the door interlock will be further described. First, it should be noted that both the hydraulic source and the pneumatic source are fully operating with respective fluids being under pressure in inlet lines, the access door 18 being closed, engaged with the actuating arm of the contact valve 26, the piloted diverter valve 28 being detented so as to pass the flow of hydraulic fluid around the motor 16, and with the hydraulic spool control valve 17 being in its neutral position such that fluid passes directly therethrough to the reservoir tank via inlet line 34, passageway 36, return line 38. Thus, as the spool valve 17 is shifted to its forward drive position, hydraulic fluid passes from the inlet line 34, through passageway 40, to line 42, through passageway 44 (of diverter valve 28), to line 46 which directs fluid into the left-hand side of the motor 16, and then via lines 48,49 to passageway 50 of valve 18 which is internally connected to the hydraulic return line 38. If the spool valve 17 is shifted in an opposite direction so as to reverse the direction of the motor 16, fluid flows via line 34, through passageway 52 to line 49 and line 48 to the right side of the motor 16, and then returns via lines 46, passageway 44, line 42 to passageway 54 which is internally connected to return line 38. It can be thus seen that when pressure is applied on the diverter valve 28, it is so positioned to pass hydraulic fluid either to one or the other sides of the motor 16 to thereby drive the rotating components of the tong 10 in either forward or reverse directions depending on the forward or reverse positions of the control valve 17. However, when the pneumatic pressure is relieved from the diverter valve 28, the internal spring forces the valve to the right, thus changing the flow path of the hydraulic fluid so as to bypass the motor 16. In such pressure relief position of the diverter valve 28, the fluid flow path is via lines 49,58, passageway 56 and line 42, thereby bypassing the flow of fluid to the motor 16. Since the flow of fluid through line 46 is blocked, no fluid passes to the motor 16, thus rendering it inoperative.

It can be understood from the foregoing that the described interlock-mechanism controls the operation of the hydraulic motor 16, and thus the operation of the tong 10, in response to the open and closed positions of the access door 18, such that the tong 10 can only be operated with the access door 18 in its closed position, and thereby eliminating the possibility of structural damage to the tong from operating same with the door open, as well as, providing safety to the operator from exposure to the various operating components of the tong.

Tong Line Pull Gauges and Tong Torque Gauges both tell the operator the amount of torque being applied to oilfield tongs; however, they perform this necessary task differently.  Although they both measure the force applied to the pipe in make up and break out situations, how they measure this force is what makes these two gauges different.  Knowing which tong gaugewill work best for your application and employees is all important in selecting a tong gauge.

The biggest difference between these two gauges is how and what they measure.  A tong line pull gauge measures true force (force/pounds), so what you see on the gauge is exactly what’s being applied to the pipe.  Basically, it’s the what-you-see-is-what-you-get gauge.  A tong torque gauge, on the other hand, measures the force that is being applied to the load cell and reads this force in foot/pounds. A more detailed explanation of both gauges follows.

A tong line pull gauge is universal.  As long as the tong is a manual tong, a tong line pull gauge will fit on any hydraulic tong system.  No matter what the tong’s handle length, a tong line pull gauge will measure force/pounds.  The advantage to these gauges is that because they are universal, they can be used on any manual tong system. For example, you have two tongs, one with a 48 inch handle, and one with a 36 inch handle. You can use a tong line pull gauge with each tong, either the 48 inch handle or 36 inch handle, and measure the force pounds being applied to the drill pipe.  Having this gauge on hand can be very useful when you have to move from different manual tong systems with different handle lengths. These systems, consisting of gauge, hose, and load cell, are great for the driller who wants to measure force/pounds on a variety of manual tongs.

Handle lengths are measured from the center of the tong to the end of the handle.  If this measurement is in inches, it will need to be converted to feet in order to find max torque.

Once you have the max torque needed and the handle length in feet, you can complete the formula.  The example below shows the formula in action.  If you want to measure the maximum torque of 18,000 foot/pounds and you have a handle length of 34 inches, the calculations will look like this:

In this instance, when trying to determine foot/pounds and the reading he needs on the gauge, the driller will need to multiply 2.83 by the reading on the gauge (in this instance 6360.42) to make sure he’s reaching the torque required. Alternately, the drilling can use the maximum torque required, divide it by the handle length to determine what the optimal reading will be.

Tong torque gauges can be used on manual tongs or power tongs, but the handle length must never change because these gauges are not universal.  A tong torque gauge is calibrated to a specific tong handle length and thus reads in foot/pounds instead of force/pounds.  The advantage to the gauge readings being foot/pounds is that the driller does not have to convert the gauge measurement in order to know the foot pounds being imposed on the drill string. By doing the math beforehand, the driller will avoid any miscalculations that could cause possible twistoffs.  The calculations are completed when the system is calibrated, taking the worry out of the driller’s hands and making the measurement of torque easier in the field. These systems, consisting of gauge, hose, and load cell, are great for the driller who wants to measure foot pounds without calculations in the field.

This is a real resume for a Tong Operator in Dayton, Minnesota with experience working for such companies as Valley Paving, Weatherford International, Quality Green Llc. This is one of the hundreds of Tong Operator resumes available on our site for free. Use these resumes as templates to get help creating the best Tong Operator resume.

A two-speed Hydra-Shift® motor coupled with a two-speed gear train provides (4) torque levels and (4) RPM speeds. Easily shift the hydraulic motor in low speed to high speed without stopping the tong or tublar rotation, saving rig time.

A patented door locking system (US Patent 6,279,426) for Eckel tongs that allows for latchless locking of the tong door. The tong door swings easily open and closed and locks when torque

is applied to the tong. When safety is important this locking mechanism combined with our safety door interlock provides unparalleled safety while speeding up the turn around time between connections. The Radial Door Lock is patented protected in the following countries: Canada, Germany, Norway, United Kingdom, and the United States.

The field proven Tri-Grip® Backup features a three head design that encompasses the tubular that applies an evenly distributed gripping force. The Tri-Grip®Backup provides exceptional gripping capabilities with either Eckel True Grit® dies or Pyramid Fine Tooth dies. The hydraulic backup is suspended at an adjustable level below the power tong by means of three hanger legs and allowing the backup to remain stationary while the power tong moves vertically to compensate for thread travel of the connection.

The present invention relates to tools used in the oil and gas drilling industry, such as power tongs, to grip and apply torque to drill pipe and other tubular members. More particularly, the present invention relates to the jaw members of the power tong and an improved structure for such jaw members.

The use of power tongs to make up and break apart threaded connections on drill pipe and similar tubulars is well known in the oil and gas industry. Typically the power tong will have at least two jaw members which ride on cam surfaces in order to bring the jaws into and out of contact with the tubular. An example of this camming mechanism is shown in U.S. Pat. No. 5,435,213 to David A. Buck, which is incorporated by reference herein. The jaw members themselves have also been the subject of inventive effort as evidenced by U.S. Pat. Nos. 4,709,599, 4,649,777 and U.S. application Ser. No. 08/805,442, filed on Feb. 25, 1997, all to David A. Buck and all incorporated by reference herein. The jaw members typically will have roughened or knurled gripping surface which will allow the jaw members to superficially penetrate or "bite" into the outer surface of a tubular and thereby securely grip the tubular.

Generally, the jaw members are mounted between upper and lower cage plates which may rotate within the body of the power tongs. The jaw members mounting in the cage plates allows the jaw members may move radially toward and away from the tubular in order to selectively engage and disengage the tubular. As explained in more detail below, this radial movement is effected by rollers on the jaw members traveling along cam surfaces positioned on a ring gear. Applying torque to the ring gear will urge the rollers or cam followers of the jaw members up the cam surfaces so that the jaw members close on the tubular. The power tong is structured so that initial rotation of the ring gear causes the jaw members to exert radial force on the tubular, but the jaw members do not initially transfer torque to the tubular. However, continued rotation of the ring gear will begin to impart both an increasing radial force and torque to the tubular.

Therefore the present invention provides an improved power tong jaw having a jaw body with a roller aperture formed therein. A jaw roller is positioned in said roller aperture by some type of retaining surface, such as a roller pin. Additionally, a friction reducing surface is formed between the jaw roller and the jaw pin. In one embodiment, this friction reducing surface comprises a plurality of needle bearings.

FIG. 1 is a top view of a conventional power tong with the cover plate and upper cage plated removed in order to show the power tong"s main internal components.

FIG. 1 is a top view of a prior art power tong 1 such as disclosed in U.S. Pat. No. 5,435,213 to David A. Buck, which is incorporated by reference herein. FIG. 1 illustrates tong 1 with the top cover plate and top cage plate removed exposing to view ring gear 5, lower cage plate 7 and jaw members 10. Jaw members 10 are positioned between lower cage plate 7 and an upper cage plate (not shown). Jaw members 10 are also positioned in slots which are formed in the upper and lower cage plates such that jaw members 10 may move radially toward and away from tubular 8. As seen in FIG. 2, conventional jaw member 10 will have a jaw body 11 and a die 14 which will provide the surface actually engaging the tubular 8. Die 14 will attach to the front of jaw body 11 and be held in place when die clips 15 are attached to jaw body 11 by way of conventional screws (not shown) engaging clip apertures 16. The rear of jaw body 11 will have a roller aperture (not seen in FIG. 2, but similar aperture 23 seen in FIG. 4) which receives roller 12 such that roller 12 may be pivotally held in place by jaw pin 13. As suggested by FIG. 1, jaw member 10 is positioned in power tong 1 such that jaw roller 12 may engage cam surfaces 4 and 6. Ring gear 5 is mounted in the body 2 of power tong 1 on ring gear rollers 3 such that ring gear 5 may rotate relative to both the tong body 2 and the cage plates. Relative movement between ring gear 5 and the cage plates causes rollers 12 of jaw members 10 to ride onto positive cam surface 6 or neutral cam surface 4 and engage or disengage tubular 8. FIG. 1 illustrates the relative movement between cage plate 7 and ring gear 5 as having moved jaw members 10 on to positive cam surface 6 and into engagement with tubular 8. Generally a friction causing brake band (not shown) will hold the cage plates stationary as ring gear 5 begins its initial rotation. This allows jaw members 10 to ride onto positive cam surface 6 and engage tubular 8 without torque being applied to jaw members 10 and hence without torque being applied to tubular 8. As jaw members 10 travel further on cam surface 6, jaw members 10 tend to become, in effect, wedged between tubular 8 and cam surface 6. This produces the radial load on tubular 8 and imparts torque to the cage plates through jaw members 10. Continued rotation of ring gear 5 will eventually generate sufficient torque for the cage plates to overcome the frictional resistance of the brake band. At this point, the cage plates and ring gear 5 rotate together and torque will begin to be applied to tubular 8. The continued rotation of ring gear 5 not only supplies torque to jaw members 10, but also produces additional radial force against tubular 8. In order to prevent slipping between tubular 8 and jaw members 10, it is important that the radial force be sufficient to securely grip tubular 8 prior to significant torque being applied to jaw members 10. When tubular 8 is a comparatively small tubular, preventing slippage becomes even more difficult since small tubulars present less surface area to be gripped. Therefore it is advantageous to eliminate any unnecessary frictional forces that tend to prevent torque from producing a corresponding radial load on jaw members 10. As mentioned above, one source of friction are the rollers 12 of jaw members 10. Therefore the present invention provides a jaw member that substantially reduces the frictional forces caused by rollers 12.

FIGS. 7-10 illustrate further alternate embodiments wherein roller retaining surface 35 comprises a structure other than a jaw pin 36. FIG. 7 shows a jaw member 20 having a jaw body 21 and a roller aperture 23 with open sidewalls 47. Roller aperture 23 is sized to have a diameter just slightly larger than jaw roller 22. Therefore when jaw roller 22 is inserted in jaw aperture 23, jaw roller 22 will be able to rotate within jaw aperture 23. Since roller aperture 23 does not completely inclose jaw roller 22, a section of jaw roller 22 will extend beyond open sidewalls 47 such that jaw roller 22 will be able to contact the cam surface of the power tongs. As seen in FIG. 7, sidewalls 47 will form in this embodiment the retaining surface 35 which holds jaw roller 22 within roller aperture 23. The inner walls of roller aperture 23 will form a contacting surface 46 against which jaw roller 22 will rotate. In this embodiment, a friction reducing surface 31, such as the Teflon® materials described above, is formed on jaw roller 22 such that jaw roller 22 may rotate against contacting surface 46 with a reduced frictional resistance. Alternatively, the friction reducing surface 31 could be formed on contacting surface 46 or even on both jaw roller 22 and contacting surface 46. Jaw member 20 will also include retainer plates 45 which will secure jaw roller 22 from vertical movement in roller aperture 23. The bearing structure shown in FIG. 7 is generally referred to in the art as a "journal bearing".

FIGS. 8-10 illustrate still another variation of jaw member 20. This embodiment is similar to that of FIG. 7 in that it includes a jaw body 21, jaw roller 22, roller aperture 23 and retainer plates 45. However, the embodiment of FIG. 8 differs in that the friction reducing surface is formed by recirculating ball bearing system 49. Recirculating ball bearing system 49 will further comprise ball bearings 50 (shown removed from jaw member 20 in FIG. 8) and recirculating channel 51 which is formed on the aperture wall 54 of jaw aperture 23. Recirculating channel 51 is a continuous channel further comprising shallow bearing groove 52 and deep bearing groove 53. Shallow bearing groove 52 transitions into deep bearing groove 53 at curved sections 55 of recirculating channel 51. While only part of recirculating channel 51 is seen in the figures, it will be understood that the part of recirculating channel 51 hidden from view is symmetrical with that shown. As best seen in FIG. 10, deep bearing groove 53 will be cut far enough into aperture wall 54 that ball bearings 50 traveling therein will not pertrude beyond aperture wall 54 and cannot contact a jaw roller 22 positioned in aperture 23. On the other hand, shallow bearing groove 52 will be cut deep enough into aperture wall 54 to retained ball bearings 50, but will still be shallow enough to allow ball bearings 50 to pertrude beyond aperture wall 54 and contact a jaw roller 22.

In operation, a jaw roller 22 will be positioned in roller aperture 23 of the jaw member 20 illustrated in FIGS. 8-10. When roller 22 moves along the cam surface of the power tongs, it will rotate causing the ball bearings 50 in the shallow bearing groove 52 to move along the length of shallow bearing groove 52. As ball bearings 50 enter into curved section 55, circulating channel 51 will transition into deep bearing groove 53. It is preferable that ball bearings 50 move below the surface of aperture wall 54 prior to beginning movement in a vertical direction in curved section 55. Otherwise ball bearings 50 will not be able to roll horizontally and will present a less efficient friction reducing surface. Ball bearings 50 will circulate in the sense that jaw roller 22 is forcibly rolling ball bearings 50 toward one end of shallow bearing groove 52. As ball bearings 50 exit that end of shallow bearing groove 52 and enter in deep bearing groove 53, these ball bearings 50 will force ball bearings 50 in their front to travel along deep bearing groove 53 and enter shallow bearing groove 52 at its opposite end. In this manner, the rotation of jaw member 22 will cause a continuous circulation of ball bearings 50 between shallow bearing groove 52 and deep bearing groove 53.

Nor is the scope of the present invention limited to the specific embodiments illustrated above. Friction reducing surface 31 is intended to include all manner of mechanisms for reducing friction between jaw pin 36 and jaw roller 22. For example, if a proper seal is placed between jaw pin 36 and jaw roller 22, it is envisioned that a viscous liquid could serve as a friction reducing surface 31. All such modifications are considered within the scope of the present invention. Furthermore, those skilled in the art will recognize the significant advantages gained by reducing the friction forces acting on the jaw members of a power tong. For example, applicant has found that the present invention requires significantly less torque to achieve the same radial load as compared to prior art jaws. Applicant achieved these results by employing the present invention in a power tong similar to that disclosed in U.S. Pat. application Ser. No. 08/806,074 to David A. Buck, which is incorporated by reference herein. The power tong in question was a 51/2 inch model tool (i.e., capable of gripping tubulars up to 51/2 inches in diameter) and the test was performed on a 31/2 inch tubular. When the prior art jaw assembly having no friction reducing surface was used in the power tong, a radial load of 40,000 lbs was transmitted to the tubular after the power tong had generate 4000 ft-lbs of torque on the tubular. By contrast, when a jaw as seen in FIG. 3 was used under the same conditions, a radial load of 40,000 lbs was transmitted to the tubular by the power tong generating only 1200 ft-lbs of torque. By way of explanation, it will be understood that it is the friction of the brake band which causes the radial loads given above to significantly exceed the torque loads. The torque load represents the amount of torque transferred to the tubular. However, no torque load is placed on the tubular until after the power tong generates enough torque to exceed the frictional resistance of the brake band. On the other hand, the radial load is being placed on the tubular as soon as the jaw members engage the tubular. This radial load increases on the tubular before the frictional resistance of the brake band is overcome and the radial load continues to increase after the bake band is overcome. Therefore, typically the radial load is relatively large as compared to the torque load placed on the tubular.