Patent Publication Number: US-2004051326-A1

Title: Cam operated jaw force intensifier for gripping a cylindrical member

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
     [0001] The present application claims the benefit of U.S. Provisional Application Serial No. 60/410,239 filed Sep. 12, 2002, entitled Cam Operated Jaw Force Intensifier for Gripping a Cylindrical Member, which is hereby incorporated herein by reference. 
    
    
     
       STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT  
       [0002] Not applicable.  
       BACKGROUND OF THE INVENTION  
       [0003] 1. Field of the Invention  
       [0004] The present invention relates to devices employed for powered rotation of cylindrical or members. More particularly, the present invention relates to gripping jaw assemblies, such as those found in power tongs, back-ups, and wrenches, for applying controlled gripping force and rotational torque to a tubular member such as a drill pipe used in subterranean well applications.  
       [0005] 2. Background of the Invention  
       [0006] Power devices used to attach (“make-up”) and detach (“break-out”) the threaded ends of tubular members such as pipe sections and the like are commonly known as power tongs or wrenches. Such power tongs or wrenches grip the tubular element and rotate it as the end of one element is threaded into the opposing end of an adjacent element or member. A device known as a back-up is typically used in conjunction with power tongs to hold the adjacent tubular element and prevent its rotation. Power tongs and back-ups are quite similar, the major difference being the ability of tongs to rotate the tubular element.  
       [0007] Power tongs and wrenches generally employ a plurality of gripping assemblies, each of which includes a jaw which moves radially toward a tubular element to engage the tubular element. In the case of power tongs and wrenches, the jaw is moved radially into engagement with the tubular element and then rotated concentrically about the axis of the tubular element in order to rotate the element and therefore make-up or break-out the joint. Various mechanisms have been used in the art to actuate the jaws. Power tongs generally include devices that use interconnected gears and camming surfaces, and may include a jaw assembly which completely surrounds the tubular element and constricts concentrically in order to engage the pipe. Wrench devices generally do not completely surround the tubular element, and include independent jaw assemblies wherein the jaw assemblies may be activated by multiple, opposing hydraulic piston-cylinder assemblies.  
       [0008] Damage occurring to the tubular member due to deformation, scoring, slipping, etc., caused by the jaws during make-up and break-out is always a matter of concern. This scoring is of particular concern when the tubulars are manufactured from stainless steel or other costly corrosion-resistant alloys. Undesirable stress and corrosion concentrations may occur in the tubulars in the tears and gouges that are created by the tong or wrench teeth. In addition, to maintain integrity of the threaded connection, it is desirable to reduce the deformation of the pipe caused by the power tongs and wrenches near the location of the threads, thus allowing more compatible meshing of the threads and reducing frictional wear.  
       [0009] Increasing these concerns is the movement in the industry, particularly the well drilling industry, toward the use of new tubular members that have finer threads than those traditionally employed. Finer threads means a smaller thread pitch, making break-out harder to achieve. For these reasons, among others, it is becoming industry standard to use higher torques when making up and breaking out pipe, casing, and other tubular sections. Using the same prior art equipment and methods that have traditionally been used on older pipe may cause severe problems when used on the newer tubulars having finer threads. Therefore, with the newer, finer threaded tubulars, it is necessary to provide gripping equipment that provides enough controlled force to penetrate the pipe material, but not so much so that the pipe is irreversibly damaged.  
       [0010] Gouging, scoring, marring, and tearing of the pipe is typically caused when the jaws of the tong or wrench slip. Slipping may be caused by a number of undesirable conditions which cause concentration of the gripping force applied by the tong or wrench. Generally, there are two sources of slipping: the jaw clamping system and the gripping teeth. First, imperfections and flexibility in the clamping system can cause insufficient contact between gripping teeth of the tong or wrench and the pipe. When the clamping force is applied by the mechanical or hydraulic system to the jaw body, the teeth (typically formed on an insert that is retained in the jaw) engage the pipe material. However, when the torquing force is applied, thereby causing rotation of the pipe sections, a reaction force is created which pushes back on the insert. Due to the continued application of rotational force and the flexibility inherent in the hydraulic, mechanical, and other holding systems, the inserts tend to advance along and move back slightly from the pipe surface. Pin tolerances and hydraulic fluid compressibility contribute to the inherent flexibility in the holding systems. Pipe material flexibility, or elasticity, also contributes to the overall flexibility which tends to cause the inserts to creep back from the pipe. Consequently, the teeth creep back from the pipe material until there is insufficient contact between the gripping teeth and the pipe, causing the jaws to slip and mar or gouge the pipe surface. Because it is difficult to achieve a system where the jaws do not move relative to the pipe material, even in a strictly mechanical system, conventional jaws allow undesirable slipping.  
       [0011] A second source contributing to jaw slippage is the shortcomings inherent in the gripping teeth, which are usually set in rows on jaw inserts. The inserts are typically removable from the jaw assembly so that they may be replaced when they become worn or otherwise ineffective. Generally, assuming the clamping system is able to maintain the teeth in engagement with the pipe material, the ability of the teeth to avoid slipping is a function of the resistance that they provide. Sometimes insert resistance is viewed in terms of the resistance or penetration profile of the insert. This resistance profile represents the contact with the pipe material provided by the gripping faces of a set of insert teeth as viewed from the front of the insert in the horizontal plane in which the teeth lie. For example, evidence of pipe-scoring in tubulars held by conventional teeth inserts clearly shows a teeth profile indicating that resistance is not spread over the entire length of the tooth insert. Such scoring shows raised portions of pipe material corresponding to the spaces between the teeth where no resistance is provided. When sets of insert teeth exhibit resistance profiles with areas of no resistance, such as with conventional teeth, jaw slippage is much more likely to occur.  
       [0012] Therefore, it is desirable for a power tong or wrench to compensate for its inherent flexibility to prevent detrimental scoring or other damage from occurring to the tubular. It is also desirable for the gripping jaw inserts to maintain a sufficient contact area between the teeth and the pipe, and to have a more evenly distributed and fuller resistance profile.  
       BRIEF SUMMARY OF PREFERRED EMBODIMENTS OF THE INVENTION  
       [0013] The embodiments described herein provide a jaw assembly for use in a power tong or wrench for gripping a cylindrical member having a jaw body, a gripping insert, and a rotatable camming member disposed between the jaw body and gripping insert. The rotatable camming member rotates in response to the applied clamping and rotational forces of the power tong or wrench and operates to intensify the force provided by the jaw to the gripping insert which is engaged with the cylindrical member. The intensified force compensates for the mechanical and hydraulic flexibilities inherent in the power tong and wrench assemblies, thereby reducing or eliminating insert “creep-back,” slippage, and damage to the cylindrical member.  
       [0014] The cam operated jaw force intensifier operates without regard to the design of the gripping inserts. Thus, in one embodiment, the gripping inserts may include conventional gripping inserts. In another embodiment, the gripping inserts may comprise the new and improved gripping inserts described herein.  
       [0015] The features and characteristics mentioned above, and others, provided by the various embodiments of this invention will be readily apparent to those skilled in the art upon reading the following detailed description of preferred embodiments, and by referring to the accompanying drawings. 
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0016]FIG. 1 is a top cross-section, partial schematic view of a torque wrench engaged with a tubular member;  
     [0017]FIG. 2A is a top cross-section view of the jaw bodies of FIG. 1 with cammed die inserts engaged with a tubular member;  
     [0018]FIG. 2B is a top cross-section view of the jaw bodies of FIG. 2A including a top locking plate;  
     [0019]FIG. 3A is a top cross-section view of the jaw bodies with cammed die inserts after a rotational torquing force has been applied to the jaw body in the clockwise direction;  
     [0020]FIG. 3B is an enlarged view of a portion of one of the jaw bodies of FIG. 3A;  
     [0021]FIG. 4A is a top cross-section view of the jaw bodies with cammed die inserts after a rotational torquing force has been applied to the jaw body in the counter-clockwise direction;  
     [0022]FIG. 4B is an enlarged view of a portion of one of the jaw bodies of FIG. 4A;  
     [0023]FIG. 5 is a top cross-section view of conventional die insert teeth engaged with a tubular member;  
     [0024]FIG. 6 is a top cross-section view of conventional die insert teeth partially engaged with a tubular member after a rotational torquing force has been applied using prior art devices and methods;  
     [0025]FIG. 7A is a top plan view of a set of prior art die insert teeth;  
     [0026]FIG. 7B is a side plan view of the die insert teeth of FIG. 7A;  
     [0027]FIG. 8A is a top plan view of a set of die insert teeth with rows of teeth offset longitudinally in accordance with one embodiment of the present invention;  
     [0028]FIG. 8B is a side plan view of the die insert teeth of FIG. 8A;  
     [0029]FIG. 9A is a top plan view of a set of die insert teeth offset longitudinally and angled in accordance with another embodiment of the present invention;  
     [0030]FIG. 9B is a side plan view of the die insert teeth of FIG. 9A;  
     [0031]FIG. 9C is an enlarged, top cross-section view of a conventional jaw body including the die insert teeth of FIGS. 9A and B;  
     [0032]FIG. 10A is a top plan view of a set of die insert teeth offset longitudinally in accordance with yet another embodiment of the present invention;  
     [0033]FIG. 10B is a side plan view of the die insert teeth of FIG. 10A;  
     [0034]FIG. 11A is a top plan view of a camming member;  
     [0035]FIG. 11B is a perspective view of the camming member of FIG. 11A;  
     [0036]FIG. 12A is a top plan view of an alternative embodiment of the die insert teeth of FIG. 8A;  
     [0037]FIG. 12B is a side plan view of the die insert teeth of FIG. 12A;  
     [0038]FIG. 13A is a top plan view of an alternative embodiment of the die insert teeth of FIG. 10A;  
     [0039]FIG. 13B is a side plan view of the die insert teeth of FIG. 13A;  
     [0040]FIG. 14A is a top cross-section view of a torque wrench having a conventional jaw body with die inserts;  
     [0041]FIG. 14B is an enlarged, top cross-section view of one of the jaw bodies with die inserts of FIG. 14A;  
     [0042]FIG. 15A is a top cross-section view of a torque wrench having a conventional jaw body including the die inserts of FIGS.  9 A-C;  
     [0043]FIG. 15B is an enlarged, top cross-section view of one of the jaw bodies with die inserts of FIG. 15A. 
    
    
     NOTATION AND NOMENCLATURE  
     [0044] In the following discussion and in the claims, the terms “including” and “comprising” are used in an open-ended fashion, and thus are to be interpreted to mean “including, but not limited to . . . ”.  
     [0045] The present invention is susceptible to embodiments of different forms. There are shown in the drawings, and herein will be described in detail, specific embodiments of the present invention, including its use as a cam operated jaw force intensifier for gripping a cylindrical member. This exemplary disclosure is provided with the understanding that it is to be considered an exemplification of the principles of the invention, and is not intended to limit the invention to those embodiments that are specifically illustrated and described herein. In particular, various embodiments of the present invention provide a number of different constructions and methods of operation. It is to be fully recognized that the various teachings of the embodiments discussed below may be employed separately or in any suitable combination to produce desired results.  
     [0046] The terms “pipe,” “tubular member,” and the like as used herein shall include tubing and other generally cylindrical objects, such as logs and rods.  
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
     [0047] Referring first to FIG. 1, a torque wrench  10  is shown engaged with tubular member or pipe section  12 . Torque wrench  10  comprises a first jaw assembly  11  and a second jaw assembly  13 , both supported by wrench body  14 . Jaw assembly  11  comprises hydraulic piston cylinder  26 , including jaw engaging portion  28 , hydraulic piston  24 , jaw body or insert holder  40 , cams  60 , and die inserts  50 . Jaw assembly  13  comprises hydraulic piston cylinder  20 , including jaw engaging portion  27 , hydraulic piston  22 , jaw body or insert holder  42 , cams  60 , and die inserts  50 . Wrench  10  is shown having a wrench body  14  supporting two jaw assemblies  11 ,  13  that are circumferentially spaced about pipe  12  such that they oppose each other. However, it should be noted that there may be any number of such jaw assemblies disposed about pipe  12 .  
     [0048] Hydraulic lines  32 ,  34  conduct hydraulic fluid between a hydraulic fluid reservoir (not shown) and piston cylinders  20 ,  26 . Hydraulic lines are formed in or supported on body  14 . Pilot operated check valve  30  controls the flow of hydraulic fluid, and, as shown in FIG. 1, is holding wrench  10  in the closed or gripping position.  
     [0049] Referring now to FIG. 2, jaw bodies  40 ,  42 , die inserts  50 , and cams  60  are shown in the position in which pipe  12  is clamped within jaw bodies  40 ,  42 , and where teeth  52  of die inserts  50  have come into initial engagement with pipe  12 . Teeth  52  are shown slightly penetrating pipe  12 , all at approximately the same depth. Jaw bodies  40 ,  42  include slots or recessed portions  45 . Cams  60  are disposed within slots  45 , and are rotatable about their longitudinal axes, which extend normal to the plane of the paper. Die inserts  50  are disposed within insert cavities  51  of jaw bodies  40 ,  42  and are movable from side to side within cavity  51 . Die inserts  50  include two spaced-apart sets  54 ,  56  of teeth  52 . Jaw bodies  40 ,  42  also have engagement slots  44 ,  46 , respectively, so that jaw bodies  40 ,  42  may slide into and engage jaw engaging portions  27 ,  28  (FIG. 1).  
     [0050] Die inserts  50  also include C-shaped slots  58  extending longitudinally along the face of insert  50  opposite teeth  52 . C-shaped slots  58  are adapted to receive the lobe  66  (see FIGS. 11A, B) of cam  60  such that rotational movement of cam  60  is allowed about its longitudinal axis. Preferably, the contact surfaces between lobe  66  and slot  58  are substantially smooth and uniform so as to allow unimpeded movement between cam  60  and insert  50 . In this case, cam  60  and insert  50  may be supported by means described more fully hereinbelow. Alternatively, the contact surfaces between cam  60  and insert  50  may be adapted so as to connect cam  60  and insert  50  and still allow movement relative to each other, thereby eliminating the need for a support means between insert  50  and any other structure, such as a locking plate as described below. For example, a means for releasably attaching insert  50  and cam  60  may include male, T-shaped tracking edges on either of the contact surfaces which would slide into female grooves on the other surface.  
     [0051] Referring now to FIG. 2B, locking plate  48  is shown. A first plate  48  is shown separated from jaw body  40 , and a second plate  48  engaged with jaw body  42 . Each plate  48  includes apertures  49  which are aligned with slots  41  in jaw body  40  when plate  48  is engaged with body  40 . Attaching means, such as pins or screws (not shown), are inserted into the aligned aperture  49  and slot  41  so as to attach plate  48  to jaw bodies  40 ,  42 . Typically, a locking plate  48  will be attached to both the tops and bottoms of jaw bodies  40 ,  42 . Locking plates  48  prevent cams  60  and inserts  50  from moving longitudinally within slots  45  and cavities  51 , respectively. To further maintain cams  60  within slots  45 , protrusions or pins (not shown) may extend longitudinally from plates  48  into cams  60 . These protrusions or pins may extend partially into cams  60 , or, alternatively, extend the full length of cams  60 . Preferably, the pins would be aligned and parallel with, or coincident with, the longitudinal, central axis of cams  60  so that cams  60  rotate properly within slots  45 . To further maintain inserts  50  within cavities  51 , similar protrusions or pins (not shown) may be supported by plate  48  and extend into inserts  50 . However, because inserts  50  may move side to side within cavity  51 , inserts  50  must provide elongated slots to receive the protrusions or pins, the elongated slots being shaped to allow such movement.  
     [0052] In addition to the above described means of maintaining cams  60  and inserts  50  within slots  45  and cavities  51 , respectively, alternative means may also be employed to achieve the same results. Instead of employing pins or protrusions supported by plates  48  and extending into cams  60  or inserts  50 , cams  60  and inserts  50  may include protrusions extending longitudinally into slots provided in plates  48 . Alternatively, the cavities  51  may be shaped such as to hold inserts  50  in place and thereby also holding cams  60  in place. One way to achieve this would be to angle the side walls of cavities  51  inward toward inserts  50  so as to pinch or engage longitudinal slots in the sides of inserts  50 . However, this would tend to impede the side to side movement of inserts  50  within cavities  51 , and therefore may not be as desirable as the above-described means.  
     [0053] It should be noted that teeth  52  of FIGS.  1 - 4  are generally of the type seen in FIG. 8 (to be described in more detail hereinafter). Conventional teeth, such as the ones shown in FIG. 7, may also be used with wrench  10  and jaw assemblies  11 ,  13 . Thus, the present invention may employ conventional teeth or one of the newly-designed teeth arrangements seen in FIGS.  8 - 10 .  
     [0054] Referring next to FIGS.  3 A- 4 B, jaw bodies  40 ,  42 , die inserts  50 , and cams  60  are shown in adjusted positions (relative to FIG. 2) in response to a rotational torquing force. In FIG. 3A, the rotational torquing force is applied in the clockwise direction (typically for make-up), as shown by arrow  16 . In FIG. 4A, the rotational torquing force is applied in the counter-clockwise direction (typically for break-out), as shown by arrow  18 . After the rotational torquing force has been applied, the teeth sets  54 ,  56  protruding from die inserts  50  become distinguishable from each other by the additional amount of penetration into pipe  12  achieved due to the rotational torquing force. More specifically, as seen in FIGS. 3A and B, the rotational torquing force  16  causes teeth sets  54  to further penetrate pipe  12  relative to teeth sets  56 . In FIGS. 4A and B, the counterclockwise rotational force  18  causes teeth sets  56  to further penetrate pipe  12  relative to teeth sets  54 .  
     [0055] It should also be noted that die insert  50  may be formed as a single piece, where teeth sets  54 ,  56  are an integral part of insert  50 . Alternatively, insert  50  may be formed in separate portions, wherein insert  50  comprises a base portion adapted to receive separately formed teeth inserts  54 ,  56  that are attached to the base portion.  
     [0056] Cams  60  are rotatable within slots  45 , and therefore rotate about their longitudinal axes in response to the rotational torquing forces  16 ,  18 . Thus, cams  60  can be seen rotated slightly in a clockwise direction from their original position in FIG. 3A, and in a counter-clockwise direction from their original position in FIG. 4A.  
     [0057] Referring now to FIG. 11, a cam  60  is shown isolated from jaw bodies  40 ,  42 . Cam  60  of FIG. 11A comprises an elongated base portion  62  which curves into legs  64 . Legs  64  provide for jaw camming surfaces  65 . Extending from base  62  is lobe  66 . Lobe  66  provides for insert camming surface  67 . Cam  60  is rotatable about its longitudinal axis  68 . The width W 1  is the width of base portion  62  while width W 2  is the width of lobe  66 . W 2  is wider than W 1  as shown in FIG. 11A. Although FIGS.  1 - 4  show cams  60  in accordance with the enlarged cams of FIG. 11, it should be understood that cams  60  may be any shape such that there are two camming surfaces, with one being in contact with jaw bodies  40 ,  42  and one being in contact with inserts  50 .  
     [0058] Before operation of torque wrench  10  is described, reference is made to FIGS. 5 and 6. In FIG. 5, conventional tooth set  164  is shown engaging pipe  12 . Force  15  is applied to wrench  10  normal to pipe  15  so that teeth  162  engage and penetrate pipe  12 . This provides the gripping action required to later rotate pipe  12 . Subsequently, as seen in FIG. 6, rotational torquing force  16  is applied to wrench  10  and transferred to tooth set  164  and teeth  162 . As seen in FIG. 6, flexibility in the hydraulic and mechanical systems used to apply the forces  15 ,  16 , increased reaction forces caused by pipe  12 , and inadequate resistance to slippage by teeth  162  combine to cause teeth  162  to move back from pipe  12  in prior art gripping devices. Arrow  21  shows that teeth  162  retreat from pipe  12  while arrow  23  shows that teeth  162  move laterally with respect to pipe  12 , thereby creating gaps  165  between teeth  162  and pipe  12 . When the contact area between teeth  162  and pipe  12  is critically reduced, the teeth slip out of their previously formed grooves  167 , causing the entire wrench  10  to slip. As mentioned before, this type of slipping scores and damages pipe  12 , which is undesirable and is common with prior art power tongs, wrenches, and die inserts.  
     [0059] Referring again to FIGS.  1 - 4 , and additionally to FIG. 11, the operation of torque wrench  10  will now be described. When die inserts  50  are not engaged with pipe  12 , wrench  10  is in the open position. To maintain the open position, pilot operated check valve  30  directs high pressure hydraulic fluid into piston cylinders  20 ,  26  through hydraulic fluid line  32 . To close wrench  10  and engage pipe  12 , pilot operated check valve  30  redirects high pressure hydraulic fluid through line  34 , thereby causing piston cylinders  20 ,  26  to move toward pipe  12 . Once the appropriate amount of clamping force has been applied, the components of wrench  10  assume the positions as shown in FIG. 2. It should be noted that the operation of torque wrench  10  may vary according to the physical system used, such as cam-operated mechanical arms or leveraged, self-locking mechanical arms.  
     [0060] Once wrench  10  has engaged pipe  12 , wrench  10  may be used to either make-up or break-out sections of pipe  12 . Make-up or break-out is done by imparting a rotational force to wrench  10  using a torquing device (not shown). In FIG. 3A, a clockwise force  16  has been applied, typically used during pipe make-up. Force  16  causes jaw bodies  40 ,  42  to rotate clockwise. Because die inserts  50  are held in place by teeth  54 ,  56 , cams  60  rotate clockwise until leading inserts  50   a  come into contact with the inner side of cavity  51  and trailing inserts  50   b  come into contact with the outer side of cavity  51 . At this point, the combination of clamping force  15  and rotational force  16  (previously shown in FIGS. 5 and 6) causes leading teeth  54  of inserts  50  to penetrate further into pipe  12  than trailing teeth  56 . The increased penetration by teeth  54  and the flexibility of the hydraulic and mechanical systems of wrench  10  make the “creep-back” phenomenon explained with reference to FIG. 6 likely, yet undesirable. However, due to the specially designed cams  60  as previously described and shown in FIG. 11, this phenomenon can be avoided without regard to the type or design of the inserts and/or teeth. Due to their special shape and their ability to rotate within slots  45 , cams  60  are able to redirect portions of the forces applied to insert  50  in such a way as to oppose the unwanted movement of insert  50  (as represented by the arrows  21 ,  23  in FIG. 6). Rotation of wrench  10  activates cams  60 , whereby the mechanical force created by the movement and positioning of cams  60  enhances the force provided by the hydraulics of the clamping system. Consequently, cams  60  compensate for the flexibility in the holding systems and pipe material by mechanically intensifying the gripping force. Thus, even after force  16  has been applied, teeth  52  remain substantially engaged with pipe  12  as seen in FIG. 5 and “creep-back” is eliminated or reduced substantially.  
     [0061] To illustrate further, upon clamping, the pressure in a wrench or clamp system may be approximately 3,000 psi, for example. Once torquing occurs, the pressure in the system may increase approximately 1,000 psi, from 3,000 to 4,000 psi, due to the mechanical push-back force represented by arrow  21  in FIG. 6. Cams  60  compensate for push-back force  21  and the increased pressure to ensure that teeth  52  do not move out of engagement with pipe material  12 . Cams  60  assist wrench  10  in achieving the benefit of increased teeth penetration force, and thereby maintaining teeth engagement. Preventing teeth “creep-back” decreases slippage, thereby reducing the likelihood of detrimental gouging, scoring, or marring of the pipe surface.  
     [0062] For break-out of pipe sections, a force  18  may be applied as seen in FIG. 4A. Operation of wrench  10  is the same as previously described with make-up, except that the movements of cams  60 , inserts  50 , etc. are opposite of those described above. Because cams  60  may rotate within slots  45 , they are equally adapted to maintaining the stability of inserts  50  during break-out as during make-up.  
     [0063] Generally, there are two conventional types of clamping systems: a camming system with tongs, where the cam and camming surface are an integral part of the movement used to bring the die inserts into contact with the pipe surface, and a jaw system, where camming surfaces are not typically used. Several embodiments of the present invention combine features of these two, whereby a hydraulic jaw/piston-cylinder system closes the system and the cams hold the teeth inserts in engagement with the pipe material. Instead of initiating the camming mechanism to advance the die inserts toward the pipe surface, the hydraulic piston-cylinder system is used to advance the inserts while the camming mechanism only moves in reaction to the rotational torquing forces in order to hold the teeth steady within the penetrated pipe material. The embodiments described herein combine elements of each system to advance the capabilities presently found in wrench systems such that the “creep-back” problem is eliminated.  
     [0064] Referring to FIGS. 7 through 10, sets of insert teeth are shown in various arrangements. FIG. 7A illustrates a conventional insert  70  having chisel-shaped insert teeth  72 . Insert teeth may be any number of shapes, such as pyramidal or polygonal, with the entire insert typically machined from steel. Shown in FIG. 7A are chisel-shaped teeth  72  having first gripping faces  73 , second gripping faces  75 , and side faces  77 ,  79 . Teeth  72  are formed in rows  74  with valleys or gaps  78  in between each tooth  72  as formed by the sloping sides faces  77 ,  79 . Insert  70  includes four rows  74  having twenty teeth  72  each, although set  70  may have any number of rows  74  and any number of teeth  72 . Furthermore, conventional insert  70  has a longitudinal axis X and perpendicular axis Y. Rows  74  run parallel to longitudinal axis X. Teeth  72  also form columns  71  parallel to axis Y, meaning that teeth  72  and gaps- 78  are substantially aligned in the Y direction. Because gaps  78  are aligned, the resistance provided by conventional insert  70  can generally be represented as resistance profile  76 .  
     [0065] Width a shown in resistance profile  76  generally represents the shear width of each tooth  72 , which can also be expressed as the length of the crest of each tooth  72 . Because valleys  78  are aligned in the Y direction, the effective resistance length of conventional insert  70  is width a multiplied by the total number of teeth in row  74 . When the width a of each tooth  72  is multiplied by the total number of teeth in row  74 , it can be shown that the effective resistance length of conventional insert  70  is approximately 50% of the total length of insert  70 .  
     [0066] For exemplary purposes, assume width a is 0.150 inches, the number of teeth  72  in each row  74  is twenty, and the total length of the insert is approximately 6.000 inches. In this case, the effective resistance length of insert  70  is 0.150×20=3.000 inches, which is approximately 50% of the length of insert  70 .  
     [0067] Referring now to FIG. 8A, insert  80  is shown and comprises teeth  82  having first gripping faces  83 , second gripping faces  85 , and side faces  87 ,  89 . Teeth  82  are formed in rows  84  with spaces  88  in between each tooth  82  as formed by the sloping side faces  87 ,  89 . Again, insert  80  may have any number of teeth  82  and rows  84 , as can be seen in FIGS. 12A and B wherein teeth  122  of insert  120  lie in numerous rows  124 . Referring again to FIG. 8A, teeth  82  in rows  84  lie in the plane defined by longitudinal axis X and perpendicular axis Y. However, unlike insert  70  of FIG. 7A, set  80  has rows  84  which have teeth  82  that are offset in the longitudinal direction from the teeth of each adjacent row  84 . Thus, teeth  82  no longer form uninterrupted columns in the Y direction. Thus, in insert  80 , teeth  82  in a given row and in a given position relative to the X axis may be said to be offset or staggered from the teeth  82  in each adjacent row  84 . Likewise, in insert  80 , gaps  88  in a given row  84  are no longer aligned in the Y direction with gaps  88  in each adjacent row.  
     [0068] Although the shear width of each individual tooth  82  in insert  80  remains the same as that of each individual tooth  72  in insert  70  of FIG. 7, the new resistance profile  86  of FIG. 8A shows an effective resistance length that extends approximately the entire length of insert  80 , and can be represented by the dimension c. Resistance profile  86  represents the contact with the pipe material provided by the gripping faces  83 ,  85  as viewed from the front or rear of insert  80  in the plane defined by axes X and Y. The oscillating resistance profile  76  of insert  70  of FIG. 7A reflects the fact that gaps  78  in insert  70  are all aligned in the Y direction, and thus do not provide resistance between each width a of teeth  72 . Resistance profile  86  of insert  80 , however, reflects that each gap  88  is substantially aligned in the Y direction with a tooth  82  in each adjacent row  84 , whereby the several rows  84  of insert  80  provide slipping resistance across approximately the entire length of insert  80 . It should be noted that FIG. 8A shows each row  84  is offset by approximately one-half of a tooth  82  width from each adjacent row  84 , meaning that the tooth  82  of every other row  84  is aligned. However, each row  84  may be offset from each adjacent row  84  by something more or less than one-half of a tooth  82  width, but preferably only in such a way that the resistance profile  86  is created.  
     [0069] The new resistance profile  86  shown in FIG. 8A shows a new effective resistance length c which spans the entire length of the insert  80 . Using the same exemplary dimensions discussed previously, the effective resistance length of insert  80  is approximately 6.000 inches, a two-fold increase over the effective resistance length of insert  70  of FIG. 7A. This increased resistance length provides more effective resistance to insert slippage, especially in applications with smaller diameter pipes. Thus, while conventional insert  70  can be employed with the wrenches, jaws, and other clamping devices of FIGS.  1 - 4 B,  9 C, and  14 A- 15 B, improved performance is achieved with use of insert  80  and other inserts that provide greater effective resistance to slippage than does conventional insert  70 .  
     [0070] It is very difficult to manufacture the shifted or offset teeth, such as the ones described above and shown in FIG. 8A, especially when using traditional machining methods. However, investment casting techniques may be used to cast the die inserts, such as inserts  80 . The die inserts  80  (and all other inserts described herein) may be cast from steel and polished, thereby achieving similar quality and finish as with machined inserts, but in a more efficient manner considering the improved tooth design.  
     [0071] As seen in FIGS. 7 and 8, the teeth  72 ,  82  are chisel-shaped with spaces  78 ,  88  between them. The spaces  78 ,  88  allow penetrated pipe material to move, i.e., to be displaced to an area of less resistance. With a solid edge, i.e., a single tooth that extends i.e., length of the insert in the X direction without any spaces such as spaces  78 ,  88 , penetration of the teeth into the pipe material is limited because of a lack of space to accommodate the displaced pipe material. Thus, even though an effective resistance length approaching 100% of the entire length of the insert (100% resistance profile) is desirable, such as can be achieved with a single tooth that extends the length of the insert in the X direction, a single tooth solid edge is undesirable because the proper amount of pipe material penetration cannot be achieved. As a result of the offset design of FIG. 8A, a resistance profile similar to that of a solid edge (100% resistance profile) may be achieved while maintaining spaces  88  for pipe material displacement. While insert  70  of FIG. 7A has spaces  78 , insert  70  only has an approximately 50% resistance profile.  
     [0072] Referring now to FIG. 9, another embodiment of the present invention is shown. FIG. 9A shows that insert  90  comprises teeth  92  having first gripping faces  93 , second gripping faces  95 , and side faces  97 ,  99 . Teeth  92  are formed in rows  94  with spaces  98  in between each tooth  92  formed by the sloping side faces  97 ,  99 . Again, insert  90  may have any number of teeth  92  and rows  94 . The resistance profile  96  of this embodiment is similar to resistance profile  86  of FIG. 8A, with its dimension represented by the dimension e. However, unlike teeth  82  in FIG. 8, teeth  92  are angled relative to the Z axis of FIG. 9B. Referring still to FIG. 9B, it can be seen that the area of face  93  of teeth  92  is smaller than the area of face  95 , causing chisel-shaped tooth  92  to be canted toward or angled toward gripping face  93 .  
     [0073] Although the resistance profile  96  is similar to that of the embodiment in FIG. 8A, the embodiment in FIG. 9 will produce the most actual resistance to slipping when gripping face  93  is the leading face on the leading insert  90  when a rotational torque has been applied, i.e., when the rotational force acting upon insert  90  is substantially in the same direction as the direction that gripping face  93  faces. For example, referring to FIG. 9C, the die inserts  90   a  and  90   b  are positioned such that gripping faces  93  of insert  90   a  face away from gripping faces  93  of insert  90   b . In this arrangement, teeth  92  of inserts  90   a  and  90   b  may be described as being canted in opposite directions, and as extending opposite or away from one another. Positioning inserts  90   a, b  this way will produce the greatest actual resistance to slipping, which is significant because the combination clamping and rotational forces acting upon die inserts  90   a, b  will bear substantially on the die insert  90   a  when a clockwise rotational force (make-up) is being applied by wrench  10 , or die insert  90   b  when a counter-clockwise (break-out) rotational force is being applied by wrench  10 . Thus, whether wrench  10  is being used for make-up, as in FIG. 3, or break-out, as in FIG. 4, the leading sides of die inserts  90   a, b  will always have a substantial number of gripping faces  93  facing the same general direction as the rotational torque. Once again, teeth  92  in each row  94  are staggered or offset with respect to teeth  92  in at least one (and preferably both) adjacent rows  94 .  
     [0074] Referring next to FIG. 10, yet another embodiment of the present invention is shown. Insert  100  comprises teeth  102  having first gripping faces  103 , second gripping faces  105 , and side faces  107 ,  109 . Teeth  102  are formed in rows  104  with spaces  108  in between each tooth  102  formed by the sloping side faces  107 ,  109 . FIGS. 13A and B show that rows  104  may be formed in any quantity, such as rows  134  of insert  130 . The resistance profile for this embodiment will look substantially similar to the resistance profile  86  of FIG. 8A. Furthermore, the side view of FIG. 10B is also substantially similar to the side view seen in FIG. 8B. Also, similar to spaces  88  in FIG. 8A which are not aligned in the Y direction with spaces  88  in immediately adjacent rows  84 , spaces  108  are not aligned in the Y direction with spaces  108  in immediately adjacent rows  104 . However, each space  88  is independently aligned in the Y direction whereas each space  108  is positioned diagonally relative to the axis Y. This design forms diagonal rows  101  of aligned spaces  108  and may be manufactured using the investment casting technology used in manufacturing the previous embodiments, but is particularly suited for ease of manufacture when machining. Thus, in insert  100 , teeth  102  in each row  104  is offset a given measure in the X direction from teeth  102  in the immediately adjacent row  104 , but the amount of offset is less than the length of a tooth  102 . In this arrangement, spaces.  108  in a given row are offset a given measure in the X direction from the spaces  108  in the immediately adjacent rows  104 . That given measure is chosen such that the terminal edges of spaces  108  in a first row contact the terminal edges of spaces  108  in each immediately adjacent row. Rows  101  may be formed at an angle relative to the Y axis of between approximately 10 and 45°.  
     [0075] It should be noted that the teeth in any of the embodiments in FIGS.  8 - 10  may be designed in any shape, and multiple shapes may be present within any set of teeth on an insert. It is important, however, that the gaps and spaces between the teeth be present because, as mentioned before, a solid edge is undesirable.  
     [0076] The cam operated jaw force intensifier of the present invention makes it possible to use even conventional teeth inserts, such as insert  70  of FIG. 7A, with less slippage and damage to the pipe, although the new teeth arrangements described and shown in FIGS.  8 - 10  are preferred for still greater improvement. Referring to FIGS. 14A and B, conventional jaw body  142  is shown having dies inserts  146 . Inserts  146  may include conventional teeth inserts, such as insert  70  of FIG. 7A, although the new teeth arrangements described and shown in FIGS.  8 - 10  are preferred for reducing or eliminating slippage and damage to the pipe even without the use of the cam operated jaw force intensifier of FIGS.  1 - 4 . Similarly, FIGS. 15A and B show conventional jaw body  152  having die inserts  156 ,  158 . FIGS. 15A and B show more particularly how die inserts  158 , which may be conventional inserts  70  of FIG. 7A or the improved inserts of FIGS.  8 - 10 , may be used in conjunction with dies inserts  156 , which may be any of the improved designs of FIGS.  8 - 10  but are particularly shown as the design of FIGS.  9 A-C.  
     [0077] The above discussion is meant to be illustrative of the principles and various embodiments of the present invention. While the preferred embodiment of the invention and its method of use have been shown and described, modifications thereof can be made by one skilled in the art without departing from the spirit and teachings of the invention. The embodiments described herein are exemplary only, and are not limiting. Many variations and modifications of the invention and apparatus and methods disclosed herein are possible and are within the scope of the invention. Accordingly, the scope of protection is not limited by the description set out above, but is only limited by the claims which follow, that scope including all equivalents of the subject matter of the claims.