WO2017100913A1 - Torque wrench - Google Patents

Abstract

A torque wrench for making and breaking connection joints between sections of pipe on a well operation rig is configured for use in either vertical or slant operations. The torque wrench includes a concentric bearing between the power tong and the frame. The concentric bearing supports and centralizes the power tong for substantially friction free rotation about well center such that any torque generated in the power tong is reacted only through a torque monitoring coupling, such as including a torque reactor and load cell. The torque wrench also has a thread compensation system that permits the power tong to float relative to the back-up tong as pipes are threaded up or out, while remaining centered.

Description

TORQUE WRENCH

PRIORITY CLAIM

This application claims priority to US 62/269,658 filed December 18, 2015. FIELD

The invention relates to a rig floor torque wrench. BACKGROUND

A torque wrench for the rig floor is sometimes called a power tong apparatus or an iron roughneck.

For wellbore operations such as drilling or servicing, a wellbore operations rig is employed. Such rigs are often called drill rigs, but sometimes they are not used for drilling but instead for wellbore servicing such as workovers, milling, repairs, etc.

Wellbore operations employ pipe strings, sometimes called drill strings but used for both drilling and servicing. The drill string can comprise a bottom hole assembly such as a drill bit attached to sections of drill pipe. As the well is drilled, additional sections of drill pipe are added to the drill string to extend its length until the bottom hole assembly is deep enough to reach a depth of interest. Sections of pipe are joined together using threaded connections on the pipe, often referred to as "pin" and "box", where the pin of one section of pipe is threaded into the box of an adjoining section of pipe. When the drill string is removed from the wellbore, the sections of pipe can be removed from the drill string by unthreading the connections and setting aside a pipe.

To make or break the threaded connection between sections of pipe, a drill floor torque wrench (alternately known as a power tong apparatus or an iron roughneck) can be used to do so. Known designs use a motor with a transmission to operate the power tong mechanism to grip and turn one section of pipe relative to another section of pipe to thread them together (i.e. make a joint) or to separate them (i.e. break a joint).

Torque wrench technology was developed on vertical rigs. With the introduction of slant rigs, some torque wrench features have been noted as limitations.

SUMMARY

In accordance with a broad aspect of the present invention, there is provided a torque wrench for making and breaking connection joints between sections of pipe on a well operation rig, the torque wrench comprising: a back-up tong having first pipe-gripping jaws; a power tong positioned above the back-up tong and having second pipe-gripping jaws in a jaw opening with an entry to the jaw opening, the second pipe-gripping jaws configured to rotate about a center axis relative to the first pipe-gripping jaws; a frame for supporting the power tong above the back-up tong; a torque monitoring coupling to monitor torque through the power tong; and a bearing between the power tong and the frame, the bearing having a bearing surface concentric with the center axis to support and centralize power tong in frame and configured such that torque generated by the power tong is reacted only through the torque monitoring coupling.

In accordance with a broad aspect of the present invention, there is provided a positioning carriage apparatus for a torque wrench, the torque wrench for making and breaking connection joints between sections of pipe on a well operation rig. A torque wrench comprises: i) a back-up tong having first pipe-gripping jaws; ii) a power tong positioned above the back-up tong and having second pipe-gripping jaws in a jaw opening with an entry to the jaw opening, the second pipe-gripping jaws configured to rotate relative to the first pipe-gripping jaws; and iii) a frame for supporting the power tong above the back-up tong. The positioning carriage is for operatively connecting a torque wrench to the well operation rig and comprises at least one of: wherein the positioning carriage is configured to be convertible to connect the torque wrench with the entry facing right or facing left.

It is to be understood that other aspects of the present invention will become readily apparent to those skilled in the art from the following detailed description, wherein various embodiments of the invention are shown and described by way of illustration. As will be realized, the invention is capable for other and different embodiments and its several details are capable of modification in various other respects, all without departing from the spirit and scope of the present invention. Accordingly, the drawings and detailed description are to be regarded as illustrative in nature and not as restrictive.

BRIEF DESCRIPTION OF THE DRAWINGS

A further, detailed, description of the invention, briefly described above, will follow by reference to the following drawings of specific embodiments of the invention. These drawings depict only typical embodiments of the invention and are therefore not to be considered limiting of its scope. In the drawings:

Figure 1 is a top, rear perspective view of a torque wrench for a rig floor;

Figures 2a and 2b are top, front perspective views of a torque wrench on a carriage and secured to a rig, which Figure 2a showing a slant rig installation and Figure 2b showing a vertical rig installation; Figures 3a and 3b are top, front perspective views of a torque wrench carriage, with Figure 3a showing the carriage in a left side position and Figure 3 b showing the carriage in a right side position;

Figure 4 is a perspective view showing the underside of a torque wrench;

Figure 5a is a schematic top plan view of the torque wrench of Figure 1 with the driver removed and the power tong simplified;

Figure 5b is an enlarged side elevation of a bearing useful in the power tong of Figure 5a;

Figure 6 is a top perspective view of a pipe-centralizing assembly useful with a torque wrench; and

Figures 7a and 7b are bottom plan and bottom perspective views of guard doors for a power tong.

DESCRIPTION OF VARIOUS EMBODIMENTS

The detailed description set forth below in connection with the appended drawings is intended as a description of various embodiments of the present invention and is not intended to represent the only embodiments contemplated by the inventor. The detailed description includes specific details for the purpose of providing a comprehensive understanding of the present invention. However, it will be apparent to those skilled in the art that the present invention may be practiced without these specific details.

A rig floor torque wrench is provided. Referring to Figures 1 and 2, one embodiment of torque wrench apparatus 10 is shown. In some embodiments, apparatus 10 can include positioning carriage 15 and torque wrench 1 1 operatively attached thereto. In some embodiments, positioning carriage 15 can further comprise of a frame 16 and a shuttle 18 slidably mounted on the frame. Frame 16 can further comprise brackets 20 disposed thereon for mounting apparatus 10 to drilling rig 28, as shown in Figure 2.

In some embodiments, torque wrench 1 1 can further comprise power tong 12, back-up tong 14, hydraulic valve bank 22, drive assembly 24, support frame 25 and lifting frame 26. Hydraulic valve bank 22 is for manually controlling the operation of apparatus 10. Support frame 25 supports the torque wrench components 12, 14, 22 and 24 and is configured at least for securing the torque wrench 1 1 to positioning carriage 15, supporting power tong 12 in an adjustable way above back-up tong 14 and supporting the power tong for operation. Lifting frame 26 is disposed on frame 25 above power tong 12 for lifting torque wrench 11.

Referring also to FIGS. 3a, 3b and 4, an embodiment of positioning carriage 15 is shown in more detail. As noted, carriage 15 includes frame 16 and shuttle 18. Shuttle 18 supports torque wrench 1 1. Shuttle 18 includes a base 30 and an arm 32. Base 30 is connected to frame 16. Arm 32 extends out from base 30 and includes a connector 34 at its outboard end. Connector 34 receives a permanent or releasable mating connector 36 on torque wrench 1 1.

In some embodiments, frame 16 can comprise a pair of mounting rails 42 that each carries brackets 20 for securing to the vertical sides the mast on rig 28. The weight of the apparatus 10 is supported on rails 42 and there are sufficient brackets 20 to ensure that rails 42 can be firmly secured, as by use of welding, fasteners (pins, bolts), etc., to the mast. Rails 42 support a horizontal track 44, which supports shuttle 18.

In one embodiment, horizontal track 44 can be vertically moved to move torque wrench 11 to accommodate various wellhead heights. In such embodiment, horizontal track 44 may be axially adjustable along rails 42. In one embodiment for example, frame 16 includes a height adjustment system through which the axial position of track 44 may be selected relative to rails 42. The height adjustment system may include a bearing sleeve 45 installed about each rail and at least on one side, a linear actuator, such as a cylinder 56, screw drive, etc., operatively coupled between sleeve 45 and rail 42. Cylinders 56 are installed on each rail in this illustrated embodiment. Each cylinder 56 may, for example, be connected by a clevis 58 and pin 60 to a base end of its rail and connected at the other end by clevis 62 and pin 64 to sleeve 45.

Track 44 is connected to sleeves 45 by connectors 46 and cylinders 56 can be driven to move track 44 up and down, arrows A, along rails 42, which moves the torque wrench vertically. For example, when cylinders 56 are extended, sleeves 45 can move upwards along their rails 42 thereby raising track 44 and thereby raising torque wrench 1 1. When cylinders 56 retract, sleeves 45 are moved down along their rails 42 thereby lowering the height of track 44 and torque wrench 1 1. Cylinders 56 lock in position when not actuated to lock the vertical position of sleeves 45 along rails 42.

Shuttle 18 is secured on horizontal track 44 and is configured to support torque wrench 11. In some embodiments, shuttle 18 can be horizontally moved to move torque wrench 11 horizontally, for example into and out of alignment with well center WC in front of mast 28a. In such embodiment, shuttle 18 may be moveable along track 44. In one embodiment for example, frame 16 includes a horizontal adjustment system through which the lateral position of shuttle 18 may be selected relative to track 44. The horizontal adjustment system may include a linear bearing 65a, 65b installed between shuttle 18 and track 44. The linear bearing includes an elongate bearing track 65a on track 44 and a bushing 65b on the shuttle. In the illustrated embodiment, there are actually two parallel linear bearings 65a, 65b. Bushings 65b can ride along tracks 65a. The horizontal adjustment system may further include at least one linear actuator, such as a cylinder 66, screw drive, etc., operatively coupled between shuttle 18 and track 44.

Cylinder 66 can be driven to move shuttle 18 side-to-side, arrow B, along track 44, which moves the torque wrench horizontally into and out of alignment with well center WC. For example, when cylinder 66 is extended, shuttle 18, and thereby torque wrench 11 , is moved along track 44 out to the side away from well center and when cylinder 66 is retracted, shuttle 18, and thereby torque wrench 1 1 , is moved along track 44 towards the mast and into alignment with well center where it can be employed to make up or break out connections. Cylinder 66 locks in position when not actuated to lock the position of shuttle 18 along track 44. There may be a cover over the track to shield and protect the cylinder 66 and the linear transducer. In this embodiment, the cover is in the area in between mounting connections 46a, 46b.

Thus, while carriage 15 secures the torque wrench securely to the mast 28a of a rig, it permits flexibility in the position of the torque wrench 1 1 to accommodate well site conditions and to move the torque wrench 1 1 into and out of an operational position. With the height and horizontal adjustment systems described, these positional adjustments can be made remotely by actuating the cylinders or manually through hydraulic valve bank 22.

Carriage 15 also, in some embodiments, is configured to permit installation on either a slant rig or a vertical rig. Carriage 15 described above, uses non-pivotal, rigid connections and cannot pivot. In particular, carriage 15 avoids the use of swing arms and, as such, is not significantly affected by installation on a slant. In addition, the bearing surfaces of sleeves 45 and linear bearings 65a, 65b are cylindrical, which work well both in slant and in vertical configurations.

Also or alternately, carriage 15, in some embodiments, is configured to permit installation of the torque wrench for operation on either side of well center. For example, some rigs, such as vertical rigs are intended to operate with the torque wrench acting on the right side and other rigs, such as slant rigs are intended to operate with the torque wrench on the left side. With reference to a comparison between Figures 3a and 3b, carriage 15 in the illustrated embodiment is convertible between a left side configuration as shown in Figure 3 a and a right side configuration as shown in Figure 3b.

In one embodiment, shuttle 18 can accept connection of the torque wrench in either a right side- facing or a left side-facing orientation. In another embodiment, connector 34 of shuttle 18 is configured to accept connection of the torque wrench in either a right side-facing or a left side- facing orientation. In one such embodiment, shuttle 18 is configured to support the torque wrench in one configuration, for example, facing right, and is configured to be flipped over to support the torque wrench in the other configuration, for example, facing left. For example, note how surface 32a of arm 32 is facing up in Figure 3a and that surface is facing down in Figure 3b. Connector 34 of shuttle 18 may be configured to be ambidextrous to support the torque wrench above (i.e. with respect to gravity) the shuttle, when shuttle 18 is facing either up or down (i.e. when surface 32a is facing up or down). Connector 34 in one embodiment is formed as a pivot tube with a bore 50 and a detent 52 around a mouth of the bore. Torque wrench 11 can comprise a centering pin 132 having v-shaped profile 134 disposed thereon, profile 134 can be configured to match the profile of detent 52. Therefore, when pin 132 is pivotally secured in bore 50, profile 134 can fit in detent 52 and a resulting interlock can act as means to center torque wrench 1 1 in a desired orientation with respect to carriage 15. Thus to be ambidextrous, connector 34 could be formed to swivel such that bore 50 and detent 52 can be rotated relative to arm 32 to always point up. Alternately, as shown, connector 34 can include an opening to bore 50 and a detent 52 on both its upper and lower surfaces.

In one embodiment, track 44, shuttle 18, and possibly entire frame 16, are configured to permit operation in either the right hand or the left hand configuration simply by flipping over track 44 and shuttle 18, and possibly the entire carriage, while the parts remain connected.

In such an embodiment, connectors 46a, 46b between track 44 and sleeves 45 may be releasable such as including removable fasteners such as pins, bolts and/or clamps, which permit track 44 to be removed from the sleeves. A symmetrical bolt pattern may be employed, wherein connectors 46a, 46b may be symmetrical top to bottom which permit the track to be flipped and reconnected with the connectors connected upside down on the opposite sleeves. For example, in the left hand configuration, connector 46a is connected to the left hand side sleeve 45 and connector 46b is connected to the right hand side sleeve 45. To convert the carriage to a right hand configuration, connectors 46a, 46b are released to remove track 44 from it connection to sleeves 45, the track can be flipped to move shuttle from the front, left to the front right and the track can be reconnected to sleeves 45 with connector 46b connected to the left hand side sleeve 45 and connector 46a connected to the right hand side sleeve 45. Height and horizontal adjustment systems work the same regardless of orientation. The use of two linear bearings 65 and cylindrical bearing surfaces facilitate operation of horizontal adjustment system regardless of orientation. In this embodiment, rails 42 can remain connected to the mast during the reconfiguration. In some embodiments, to further facilitate reconfiguration between left and right side installation, hydraulic valve bank 22 is also ambidextrous. For example, the valve bank box can mount to a symmetrical bolt pattern on the bottom of the tong and switch spots with the electrical box. While the valves of valve bank 22 can be operated remotely, switching makes the valve handles more accessible.

In addition or apart from the carriage and its ability to reconfigure torque wrench apparatus 10 between left and right side operation, in some embodiments torque wrench 11 has one or more other features that facilitate operation in a slant orientation.

In one embodiment, torque wrench 11 may include a thread compensation system that works on both vertical and slant rigs. In operation, to make up or break out joints, tongs 12, 14 are positioned with their central axis C aligned with well center WC to engage and apply torque to drill pipes passing along well center. Back-up tong 14 clamps and holds the bottom pipe and power tong 12 clamps and spins the upper pipe to cause them to thread or unthread. During this operation, power tong 12 must remain supported and centered above back-up tong 14 but must be free move down or up relative to the back-up tong as the upper pipe threads into or out of, respectively, the bottom pipe.

A thread compensation system supports power tong 12 above and aligned with the center point of back-up tong 14 while permitting the power tong to move up or down relative to back-up tong as driven by the movement of the threaded connection. The thread compensation system is isolated from gravitational effects, such that it can operate identically either vertically, when the center axis C through tongs 12, 14 is vertical, or in slant, when the center axis C through tongs 12, 14 is off- vertical (i.e. slanted).

Thread compensation system may include a guide that permits vertical movement of power tong 12 relative to back-up tong 14, but holds power tong 12 in axial alignment with back-up tong 14. For example, torque wrench 11 may include a pair of parallel linear bearings 68, each including a rail 68a and a bushing sleeve 68b, between power tong 12 and back-up tong 14. The linear bearings hold the power tong against twisting, or being pulled by gravity, out of alignment with the back-up tong but the linear bearings also permit movement of the power tong along the bearings towards and away from the back-up tong.

In one embodiment, support frame 25 includes the linear bearings 68, specifically rails 68a, positioned on a column 69. Column 69 is rigidly connected to the housing of the back-up tong 14. Rails 68a are coupled rigidly to the column above back up tong. A frame 70 of the power tong is coupled to rails 68a by bushing sleeves 68b. In particular, while column 69 and rails 68a pass up through an opening in frame 70, the housing is connected to the column only through the interaction of sleeves 68b on rails 68a. In the illustrated embodiment, power tong 12 is supported by frame 70. Frame 70 is U-shaped including side arms 70a extending from end 70b. Arms 70a and end 70b surround an inner area in which power tong 12 is positioned.

Additionally, the thread compensation system includes a linear actuator such as a hydraulic cylinder 72 that holds power tong 12 in a spaced position above back-up tong 14 but allows some controlled movement of the power tong along bearings 68 toward and away from back-up tong 14. In particular, cylinder 72 meters movement of power tong 12 along bearings 68 and bearings 68 ensure that movement between power tong and the back-up tong is not restricted except through action of cylinder 72. Cylinder 72 has one end secured via a mounting site on frame 70 and its opposite end secured on the housing of the back-up tong. To make up a joint, cylinder 72 is powered to move the power tong up to the desired spacing, and then the hydraulic system reduces the pressure differential across the cylinder so that the power tong is held in place by a combination of cylinder 72 and the friction in bearings 68 without falling down or moving up. As the thread advances, the excess pressure created in cylinder 72 is relieved, thereby not biasing the movement of the power tong. After the joint is completed, cylinder 72 will return the power tong to the desired spacing. To break out a joint, cylinder 72 brings the power tong down to the desired spacing, then changes pressure to balance the weight of the tong without moving it up, allowing the joint to naturally pull power tong up as the unthreading moves the upper pipe upwardly. By action of cylinder 72, power tong 12 floats above the back-up tong when threading and unthreading. Friction in bearings 68 may be quite significant, but can be accounted for hydraulically.

While springs are sometimes used for thread compensation, a linear actuator such as cylinder 72 is much more efficient and useful. Springs cannot provide the required force and travel without being orders of magnitude larger than the space required for the cylinder. Springs provide differing forces as the thread advances, the hydraulic system provides constant force as the thread advances. Springs are difficult to move around to set the spacing between the power tong and back-up tong, but the hydraulic system facilitates a spacing modification.

With this configuration, power tong 12 can move upwards or downwards relative to back-up tong 14, depending on whether torque wrench 10 is being operated in a "break-out mode" or a "make-up mode."

Column 69 can include stoppers 73 to set the lower limit of travel of the power tong toward the back-up tong. Stoppers 73 are positionally selectable for example by placement into an aperture along a track 73 b on column and defines the lowest possible position of the power tong since the power tong cannot pass the stoppers. This ensures that cylinder 72 need not bottom out at the lowest position and that tong 12 can remain spaced from tong 14 without relying on maintenance of a pressure balance in cylinder 72.

Power tong 12 includes jaws in a jaw opening 151 defined by a housing 12a and a drive system for moving the jaws radially in and out and rotationally within the housing. The housing is supported on frame 70. During use, torque wrench 11 is moved to position the jaw opening of the power tong around a pipe to be gripped and rotated. The jaw opening has a center axis C about which the jaws are positioned. Center axis C extends from top to bottom of the power tong. When a pipe is gripped and rotated, it is concentric relative to center axis C. As will be appreciated by a person skilled in the art, it is often necessary when using the power tong to measure the torque applied to a pipe disposed in jaw opening 151 and being acted on by power tong 12. As such, power tong 12 can include torque monitoring coupling such as a torque reactor 148 and a load cell 146, operatively coupled to a programmable logic controller or other monitoring electronics (not shown) as well known to those skilled in the art to measure the torque applied to pipe when disposed in jaw opening 151 and acted on by the jaws of the power tong 12.

All torque must be reacted through back-up tong 14 at reaction point 147 to torque reactor 148 and load cell 146 in order to properly measure the torque applied to the pipe through tong 12. If used in a slant operation, components of a prior art tong may tend to fall sideways, out of center and catch on a lateral surface, thereby failing to properly transfer torque to the torque reactor and the load cell. In this embodiment, to facilitate operations torque wrench 11 includes bearings 160 between the power tong housing and frame 70. Bearings 160 each have an arc-shaped bearing surface 161a with the arc defined along the surface. The arc defined by each bearing surface 161a is centered on, in other words configured concentrically relative to, center axis C of the power tong. While not all bearing surfaces are the same diametric distance from axis C, bearing surfaces 161a are each concentric relative to center axis C and guide and cradle power tong 12 for rotation centered on axis C. Bearings 160 further include planar bearing surfaces 161b to maintain the plane of housing 12a in a plane orthogonal to center axis C. Bearings 160 support the jaws of the power tong to rotate about center axis C, while power tong 12 remains substantially in a plane orthogonal to, and substantially centered on, axis C. Bearings 160, therefore, support and centralize power tong 12 within frame 70 in a substantially frictionless manner such that all torque is reacted through torque reactor 148 and load cell 146. Housing 12a substantially floats on bearings 160 within frame 70, while jaw opening remains stationary without moving center axis C relative to frame 70.

While bearings 160 may be combined in fewer semi-circular bearings, in this embodiment four bearings 160 are employed, with two bearings being installed between each frame sidearm 70a and the power tong housing outer edge. Bearings 160 are roller bearings. Bearing surfaces 161a, 161b of each bearing 160 are secured to tong housing 12a. Bearing rollers 162a, 162b, commonly called cam follower bearings, for each bearing surface are mounted on sidearms 70a and extend out to contact and bear against surfaces 161a and 161b. In the illustrated embodiment, surfaces 161b are formed between flanges 163 a that are vertically supported on plates 163b secured to the power tong housing perimeter edge. The outer edges of the flanges 163 a are shaped to define the arc-shaped surfaces 161a.

Thus, through bearings 160, power tong 12 is supported to freely rotate on an arc about center axis C of tong 12. The torque wrench may be oriented on the rig such that center axis C is alignable with well center. Bearings 160 do not react torque such that all torque through power tong 12 is reacted at cell 146. This tong support system operates regardless of the vertical orientation of the power tong, whether its plane is horizontal as on a vertical rig or whether its plane is slanted such as when torque wrench 11 is installed on a slant rig. When torque wrench is employed in vertical operations, the weight of tong jaws and housing 12a may be supported through bearing surface 161b and rollers 162b. When torque wrench is employed in slant operations, the weight of tong jaws and housing 12a may be supported through a combination of bearing surfaces 161a, 161b and rollers 162a, 162b.

An additional problem with transfer of torque wrenches to slant rig operations is with respect to the presentation of a pipe to the torque wrench. Because the pipe is presented at an angle, aligned with well center WC, an end of the pipe, if unsupported can sag and be pulled by gravity out of alignment with well center. It is difficult to line up a pipe, in this condition with the torque wrench 1 1. To further facilitate use of torque wrench 11 on a slant rig, it may include pipe-centering assembly 170 mountable above power tong 12. Centering assembly 170 includes a structure 171 for securing onto frame 25 and heads 172 on the structure. Structure 171 mounts in a fixed position on frame 25 such that heads 172 are diametrically opposed about axis C, which is the center axis of tongs 12, 14. Heads 172 are moveable to move a pipe being handled into a position aligned (i.e. substantially coaxial) with axis C.

Each head includes a base 173, a paddle 174 pivotally connected to the base via a pivot point 175 which permits the paddle to move in and out relative to axis C, guide fingers 176 on the free end of each paddle, a driver 177 to move the paddles 174 about their pivot points. Heads 172 are configured such that paddles move symmetrically relative to axis C. While the driver may be any of a motor, a linear actuator, etc. and may be one for each paddle, in the illustrated embodiment, there is only one driver 177, herein a cylinder 177a, with a link 177b secured between the paddles 174 to synchronize the pivotal movement. Actuation of the cylinder, such as by hydraulics, moves the paddle to which it is attached and link 177b causes the paddles on both heads to move together to automatically center.

Guide fingers 176 are profiled to handle multiple sizes of pipe. For example, guide fingers 176 on each paddle may have a V-shaped opening between two fingers 176a that converge at their connected end to paddle 174.

In operation, paddles 174 are opened by driver to move fingers 176 away from center, where they are ready to have a pipe is moved down towards and into the■ area A between the fingers 176. Once a pipe is in area A, driver 177 can be actuated to move paddles 174 towards axis C. This action drives the fingers 176 to approach the pipe from opposite sides, which closes the fingers 176 around the pipe. If pipe is not already positioned in alignment along axis C, fingers 176 lift and direct the pipe along the axis. Being aligned by pipe-centering assembly 170, the pipe is ready to be stabbed into power tong jaw opening 151 along center axis C.

In some embodiments, power tong 12 can further comprise guard doors 182 pivotally secured near jaw opening 151 that can be configured to open to receive a section of pipe, and to close when the pipe is within jaw opening 151 as safety means to protect personnel from the rotating components of power tong 12 when in operation. Jaw opening 151 is U-shaped with an open side that defines the entry to the opening. Guard doors 182 are each connected through a pivot pin 181 to power tong 12 and each include a front end 182a. Front ends 182a normally close across the entry of jaw opening 151 but the doors can be pivoted about their pins 183 to retract from the entry. Guard doors 182 are joined by a link 183 and a biasing member 184, such as a spring. Biasing member 184 biases guard doors 182 into a position with front ends 182a closed across opening 182. Link 183 balances the weight of guard doors 182 and synchronizes movement of the doors, which is particularly useful when the torque wrench is used in slant to prevent the doors from falling towards the low side. Link 183 and biasing member 184 extend between doors 182 through the structure of power tong, behind and outside of opening 151, opposite the entry such that they do not pass through the opening.

Front ends 182a are each formed with substantially flat face 182a' between a recessed inner corner 182a" and a protruding outer corner 182a'". When the guard doors 182 are closed, the inner corners 182a" come together at a central point and their recessed positioning forms an inwardly notched (i.e. V-shaped) open area in front of faces 182a'. Each guard door is configured such that a vector, arrow Vp, in plane with face 182a' passes inside the pivot axis and a vector, arrow VN, normal to face 182a' passes outside the pivot axis. As such, contact of soft materials, such as a worker's body part (arm, leg), against doors 182 tend to create in plane forces, through friction, which urges doors to remain shut and, in fact, urges corners 182a" into greater contact. However, contact of hard cylindrical materials, such as a pipe, against doors 182 tend to create normalized forces against face 182a', which causes doors to pivot open. A normal force against one door cause the doors to both open.

The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to those embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein, but is to be accorded the full scope consistent with the claims, wherein reference to an element in the singular, such as by use of the article "a" or "an" is not intended to mean "one and only one" unless specifically so stated, but rather "one or more". All structural and functional equivalents to the elements of the various embodiments described throughout the disclosure that are known or later come to be known to those of ordinary skill in the art are intended to be encompassed by the elements of the claims. Moreover, nothing disclosed herein is intended to be dedicated to the public regardless of whether such disclosure is explicitly recited in the claims. No claim element is to be construed under the provisions of 35 USC 1 12, sixth paragraph, unless the element is expressly recited using the phrase "means for" or "step for".

Claims

Claims:

1. A torque wrench for making and breaking connection joints between sections of pipe on a well operation rig, the torque wrench comprising:

a back-up tong having first pipe-gripping jaws;

a power tong positioned above the back-up tong and having second pipe-gripping jaws in a jaw opening with an entry to the jaw opening, the second pipe-gripping jaws configured to rotate about a center axis relative to the first pipe-gripping jaws;

a frame for supporting the power tong above the back-up tong;

a torque monitoring coupling to monitor torque through the power tong; and a bearing between the power tong and the frame, the bearing having a bearing surface concentric with the center axis to support and centralize power tong in frame and configured such that torque generated by the power tong is reacted only through the torque monitoring coupling.

2. The torque wrench of claim 1 wherein the bearing configures the power tong for mounting in a slant orientation.

3. The torque wrench of claim 1 wherein the frame is U-shaped with a base end, a first arm extending from the base end and a second arm extending from the base end and the bearing includes a first plurality of individual bearings between the first arm and the power tong and a second plurality of individual bearings between the second arm and the power tong.

4. The torque wrench of claim 1 further comprising a second bearing between the power tong and the frame, the second bearing having a second bearing surface orthogonal to the center axis.

5. The torque wrench of claim 1 further comprising a thread compensation system including a guide configured to guide vertical movement of the power tong relative to back-up tong, while the center axis of power tong remains in axial alignment with a main axis of the back-up tong.

6. The torque wrench of claim 5 wherein the guide comprises a pair of parallel linear bearings between the frame and the back-up tong, the linear bearings configured to hold the frame against twisting or being pulled by gravity, out of alignment with the back-up tong.

7. The torque wrench of claim 5 wherein the thread compensation system further comprises a linear actuator configured to hold the power tong in a spaced position above the backup tong and configured to allow controlled movement of the power tong along the guide toward and away from the back-up tong.

8. The torque wrench of claim 1 further comprising guard doors pivotally connected over the entry and configured to pivot in unison.

9. The torque wrench of claim 1 further comprising a pipe-centering assembly above the power tong.

10. The torque wrench of claim 1 further comprising a positioning carriage for operatively connecting the torque wrench to the well operation rig, the positioning carriage configured to be convertible to connect the torque wrench with the entry facing right or facing left.

1 1. The torque wrench of claim 10 wherein the positioning carriage includes linear bearings configured for movement of the torque wrench into and out of alignment with well center.