Gripping insert and method of gripping a tubular

The present invention generally provides an insert for a clamping device or gripping apparatus for conducting translational forces and/or torque into a moveable object, such as a tubular, casing, liner, pipe, expandable tubular, tubing, drill pipe. In one aspect, the insert comprises a base material and a plurality of gripping elements forming an object gripping surface. Gripping elements are at least partially embedded in the base material. The gripping elements in one embodiment are curved to correspond to an outer circumference of an object to be gripped. In one embodiment, the gripping elements are inclined relative to a longitudinal axis of the insert. In another aspect, the gripping elements may comprise grains or particles of a hardened or super-hard material. The present invention also provides a method of making the insert and using the insert in a gripping apparatus.

BACKGROUND OF THE INVENTION

1. Field of the Invention

Embodiments of the invention relate to an insert for a clamping device or gripping apparatus, which is used in particular in the field of oil and gas exploration, wherein such a clamping device or gripping apparatus conducts translational forces and/or torques into a moveable object. Such a moveable object can be a tubular body, including casing, drill pipe, etc. Lengths or stands are added to or detached from such casing or drill pipe strings, for example, during well drilling.

2. Description of the Related Art

In conventional well completion operations, a wellbore is formed to access hydrocarbon-bearing formations by the use of drilling. To drill within the wellbore to a predetermined depth, a drill string having a cutting structure attached to its lower end is often rotated by a top drive or rotary table. After drilling to a predetermined depth, the drill string and drill bit are removed and a section of casing is lowered into the wellbore.

Often, it is necessary to conduct a pipe handling operation to connect joints of casing to form casing strings which extend to the drilled depth. Pipe handling operations require the connection of casing joints to one another to line the wellbore and to form a barrier to the surrounding wellbore. To threadedly connect the casing joints, the casing string must be suspended above the wellbore so that each casing string is disposed coaxially with a casing string previously disposed within the wellbore. The threaded connection must be made up by a device which imparts torque to one casing joint relative to the others, such as a tong or a top drive. The casing string formed of the casing joints is then lowered into the previously drilled wellbore.

It is common to employ more than one string of casing in a wellbore. In this respect, the well is drilled to a first designated depth with a drill bit on a drill string. The drill string is removed. Sections of casing are connected to one another and lowered into the wellbore using the pipe handling operation described above to form a first string of casing longitudinally fixed in the drilled out portion of the wellbore. Next, the well is drilled to a second designated depth through the first casing string, and a second, smaller diameter string of casing comprising casing sections is hung off of the first string of casing. This process is typically repeated with additional casing strings until the well has been drilled to total depth. In this manner, wellbores are typically formed with two or more strings of casing.

As an alternative to the conventional method, drilling with casing is a method often used to place casing strings within the wellbore. This method involves attaching a cutting structure in the form of a drill bit to the lower end of the same string of casing which will line the wellbore. Drilling with casing is often the preferred method of well completion because only one run-in of the working string into the wellbore is necessary to form and line the wellbore for each casing string.

Drilling with casing is typically accomplished using a top drive powered by a motor because the top drive is capable of performing both functions of imparting torque to the casing string to make up the connection between casing strings during pipe handling operations and of drilling the casing string into the formation. Often, the top drive is connected to a gripping head, which is an external gripping device such as a torque head or an internal gripping device such as a spear. An exemplary torque head is disclosed in U.S. Pat. No. 6,311,792 B1, issued on Nov. 6, 2001 to Scott et al., which is herein incorporated by reference in its entirety. An exemplary spear is disclosed in U.S. patent application Publication No. US 2001/0042625 A1, filed by Appleton on Jul. 30, 2001, which is also incorporated by reference in its entirety. The gripping head has a longitudinal bore therethrough through which fluid may flow and grippingly engages the casing string to serve as a load path to transmit the full torque applied from the top drive to the casing string.

In conventional drilling operations as well as drilling with casing operations, drill strings, pipes, and casings, including corresponding pipes or casings connected during the pipe handling operation, are held, torqued, and/or translated by tongs, spiders, elevators, and gripping heads such as torque heads and spears during different stages of a well completion or other wellbore operation. Spiders and elevators are utilized to grippingly engage tubulars, pipes, drill strings, and/or casing strings above the wellbore. A spider is disposed at the surface of the well or at or in a rig floor when utilizing a drilling rig, while an elevator is suspended by bails above the surface of the well to maintain the tubulars, pipes, drill strings, and/or casing strings above the surface of the well during various operations. The spider is used to maintain a tubular, pipe, drill string, or casing string at the surface of the well and prevent it from slipping further into the drilled-out wellbore.

All of the above gripping apparatus may hold pipes, tubulars, drill strings, or casings by means of jaws disposed in these devices. These jaws may have inserts that are interchangeable and conduct translational forces and/or torques into corresponding moveable objects. Such an insert typically comprises a base material and gripping elements. Each gripping element has an object gripping surface with which it engages the corresponding object in order to lift, shift, or rotate the object. In particular, for rotation of the object, considerable clamping or gripping forces are necessary to transmit torque. The corresponding gripping elements are at least partially embedded in the base material and may be fixed within the base material during vulcanization.

A prior art clamping device includes strip-like gripping elements extending parallel with the longitudinal axis of the object to be gripped. Such inserts are sufficient for lifting or holding corresponding objects. However, if these inserts are used for rotating the object, it is possible that the corresponding gripping elements may tilt away under heavy load produced while transmitting torque to the object. Moreover, such inserts can cause undesired indentations or markings on the surface of the object to be clamped such that this surface undergoes increased corrosion. These indentations and markings are, in particular, caused during starting of the rotation when the clamping power has to be increased to stop relative movement between the jaws and the object being clamped.

Prior art gripping apparatuses cause scarring and/or marking of the object being grippingly engaged when imparting torque to the object. The scarring and/or marking increases damage to the object, thus possibly impairing the effectiveness of the object in the well operations and increasing the incidence of failure of the pipe, e.g., casing or other tubular body, within the wellbore. Additionally, the scarring and/or marking may increase corrosion along the pipe's surfaces.

There is a need, therefore, for an insert for a clamping device with which it is possible to transmit a higher torque, even when having a small gripping area, and leaving fewer indentations or markings on the surface of an object to be clamped. There is also a need for a gripping apparatus which minimizes damage to an object being grippingly engaged, even while maintaining the effectiveness of the frictional engagement with the object, and even while imparting torque to or linearly translating the object.

SUMMARY OF THE INVENTION

The present invention provides an insert for a clamping device for conducting translational forces and/or torque into a moveable object. The object may be a tubular body such as a joint of casing, or it may be a non-tubular object such as a square device. In one embodiment, the insert comprises a base material having a plurality of strip-like gripping elements at least partially embedded into the base material. Each gripping element employs an object gripping surface. The gripping elements are configured to correspond to an outer shape of the object being gripped. The strip-like gripping elements are preferably substantially parallel to one another, and are arranged transverse to a longitudinal axis of the insert. The angle of the gripping elements relative to the longitudinal axis of the insert may be optionally be offset so that the gripping elements are inclined relative to a longitudinal axis of the pipe during gripping.

In another aspect, the present invention provides an insert for a gripping apparatus for conducting translational forces and/or torque into a tubular object. The insert comprises a base material having an arcuate shape, and a gripping surface corresponding to a circumference of the tubular object. A plurality of engagement elements is attached to the gripping surface, the engagement elements capable of grippingly engaging the surface of the tubular object. In one embodiment, the engagement elements comprise grains or particles of a hardened or a super-hard material.

The present invention also provides a method of making an insert for a gripping apparatus. In one aspect, the method comprises providing a base material insertable into a housing within the gripping apparatus; and attaching engagement elements to a gripping surface of the base material. The engagement elements may comprise grains or particles of a hardened or a super-hard material capable of grippingly engaging a tubular object.

The present invention also provides a method of grippingly engaging a tubular body to impart translational forces and/or torque to the tubular body. In one embodiment, the method comprises the steps of providing a base material insertable into a housing within a gripping apparatus; attaching engagement elements to a gripping surface of the base material, the engagement elements comprising grains or particles of hard or super-hard material; inserting the base material with engagement elements attached thereto into the gripping apparatus; and grippingly engaging the tubular body with the gripping surface to impart translational forces or torque into the tubular body.

In a yet further aspect, the present invention involves a gripping apparatus for grippingly engaging a tubular object and imparting torque or translational forces to the tubular object. The apparatus in one arrangement first comprises a housing for an insert. The housing has a cavity therein formed by back and side walls. An insert is disposed within the cavity, the insert comprising a malleable base material having a hardness less than the hardness of steel. Engagement elements are attached to a gripping surface of the base material. The engagement elements may comprise particles or grains of a hard or super-hard material.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

As used below, “clamping device” and “gripping apparatus” both represent apparatus which grippingly engage moveable objects. In addition, the clamping device or gripping apparatus may conduct translational forces and/or torques into the moveable objects. Exemplary clamping devices or gripping apparatus include elevators, spiders, tongs, torque heads, and spears. An example of a clamping device usable with the present invention is described in U.S. Pat. No. 5,451,084, which is incorporated by reference herein in its entirety. Moveable objects include, but are not limited to, tubular bodies, including casing strings, pipes, drill pipes, liners, tubing, expandable tubulars, and other tubulars.

FIG. 1is a side elevational view of a first embodiment of an insert1.FIG. 2is a downward cross-sectional view of four inserts1arranged around a tubular object. The insert1is configured to apply frictional force against a corresponding moveable object, such as the tubular object2inFIG. 2. The insert1is designed to operate within a jaw of a clamping device or gripping apparatus (not shown), such as a tong, spider, gripping head, or elevator. One or more inserts1as shown inFIG. 1are utilized around the object2in connection with a gripping apparatus. When using multiple inserts1, the inserts1are preferably arranged in a circular manner to surround the object2, and the inserts1may be stacked upon one another as desired. The different inserts1may be arranged within an adaptor or the like with two or more of these inserts1arranged around the object2and with as many of such groups of two or more inserts1stacked above each other as necessary. For example, four inserts1may be utilized as shown inFIG. 2.

FIG. 3is an enlarged section view ofFIG. 1. Features of the insert1are more clearly seen inFIG. 3. As can be seen inFIGS. 1 and 3, the insert1employs a plurality of gripping elements4disposed along a base material3. The base material3is fabricated from a material that has a certain elasticity. Examples include a soft metal such as aluminum, and an elastomeric lining such as a rubber matrix. In the arrangement ofFIGS. 1 and 3, the gripping elements are strip-like in configuration, and are embedded within the base material3. Thus, the plurality of strip-like gripping elements serve as “gripping bars”4. These gripping elements4are preferably constructed of a hard material and are preferably of a metal material with an object gripping surface5(seeFIGS. 4 and 6) protruding from the base material3in the direction of the object2to be held (seeFIG. 2). The base material3and gripping elements4together form an engagement surface5for engaging the circumference18of an object, such as the tubular ofFIG. 2. The engagement surface5may be flush with the surface of the base material3or may even be arranged partially or completely within the base material3.

The plurality of gripping elements4are preferably curved or rounded so that the curvature of the gripping elements4substantially corresponds to the curvature of the circumference of the object2, such as the tubular object shown inFIG. 2. Preferably, the different gripping elements4are arranged substantially parallel to each other (seeFIGS. 1 and 3) and preferably with a constant distance between neighboring gripping elements4. In one embodiment, the gripping elements4are arranged at an angle8(seeFIG. 4) of approximately 90° with respect to the longitudinal axis of the insert1. In this way, the gripping elements are also oriented transverse to a longitudinal axis7of the object2(seeFIG. 2) being gripped.

In the arrangement ofFIGS. 1 and 3, the insert1includes an insert housing19. The housing has a back wall22, side walls23and24, and top and bottom walls28and29. By these walls22,23,24,28, and29, a concave cavity20is formed in which base material3is insertable. First and second ends26,27of each gripping element4are supported by the side walls23,24of the housing19such that the forces introduced into the gripping element4by transferring torque to an object, e.g., tubular body2, are distributed in a lengthwise direction17(seeFIGS. 5 and 6) relative to the gripping element4. By the corresponding curvature of the gripping elements4relative to the curvature of the object2, and also by the elasticity of the base member3, a substantially full surface-to-surface contact between the object gripping surface5and the outer surface or circumference of object2is rendered possible, even if the surface to be engaged deviates from, for example, a cylindrical shape, or even if the surface to be engaged has unevenness of curvature, i.e., is “out of round.”

To prevent displacement of the gripping element4in a lengthwise direction as much as possible, ribs25are optionally arranged on an inner surface21of the back wall22of the insert1. The ribs25preferably extend perpendicular to the lengthwise direction of the gripping elements4and parallel to the longitudinal axis7of object2.

The base material3is held in the cavity20at its upper and lower ends by the top and bottom walls28and29of the insert housing19These walls28and29are preferably releasably attached to the back wall22of the insert housing19. The depth of cavity20is preferably generally smaller than the thickness of the base material3such that the base material3protrudes from the cavity20in the direction of the object2, at least with its gripping elements4. By this relation of depth and thickness, any contact of walls23,24,28, and29with the outer surface of object2is avoided.

Referring again toFIG. 2,FIG. 2provides a downward cross-sectional view of four inserts1arranged around a tubular object2with longitudinal axis7. The inserts1with the corresponding gripping elements4(seeFIG. 1) are shown in full surface-to-surface contact with circumference18or outer surface of object2. The surface-to-surface contact does not have to be full, but may merely be substantial enough to effectively grippingly engage the object2, so that the insert1possesses the ability to provide torque and/or translational force to the object2. It is also possible to arrange more than two inserts1around object2. In one embodiment, only three inserts1are used.

InFIG. 4, a second embodiment of the invention is illustrated. In this embodiment, the gripping elements4are arranged at an angle8different than 90° with respect to longitudinal axis7of the insert1. The angle8may be in the range of, for example, about 50° to 130°, about 70° to 110°, or about 85° to 95°.

In another embodiment of a gripping element, shown by the dotted line inFIG. 4at “16,” the gripping element may have a wave-like curvature such that the gripping element16is substantially sinusoidal in lengthwise direction17.

FIGS. 5 to 7illustrate different embodiments of the gripping element4. InFIGS. 5 and 6A, teeth11,12are used as gripping elements9, while inFIG. 7, grains or particles10are used as gripping elements9. InFIG. 5, a top view of a gripping element30is shown. In this arrangement, the gripping element is not curved, as in other embodiments, but is essentially linear. Alternatively, the gripping element30may represent an arcuate gripping element prior to forging or reshaping. The gripping element has a plurality of teeth11,12on the object gripping surface5. The exemplary teeth11,12are arranged linearly. Optionally, the linearly arranged teeth11and12may be staggered so that a row of teeth11are at a different angle of orientation to a row of teeth12(seeFIG. 6B). In this way, the teeth11,12are interlaced with respect to each other.

The different teeth11,12may have the same depth13according to the illustrated embodiment. Also, leading and trailing edges14,15of the teeth11,12, may have the same angles with respect to lengthwise direction17, as illustrated. In the alternative, the depth may be different between pairs of teeth11,12or between a group of three, four, or more consecutive teeth11,12, with such groups or pairs repeating in lengthwise direction17. The same is true for the angles of leading and trailing faces14,15of the teeth11,12, which may alternate within repeating groups.

By casting or forging, the original gripping element30ofFIG. 5can be reshaped to form the curved gripping element4ofFIG. 6A. The gripping element4may have a curvature selected to substantially conform to the corresponding curvature of housing19and/or an object to be gripped, such as object2ofFIG. 2. In the embodiment shown inFIG. 6, the gripping element4has a constant radius of curvature. The arrangement of the teeth11,12is shown inFIG. 6Aas the same arrangement shown inFIG. 5, but the teeth11,12may be arranged at different angles with respect to each other as mentioned above and shown inFIG. 6B. The curved gripping element4with first and second ends26,27is then partially or completely embedded in base material3by vulcanization or similar process, and then the insert1with the plurality of gripping elements4is inserted in cavity20(seeFIGS. 1 and 3).

InFIG. 7, an additional embodiment of the gripping element4is partly illustrated, wherein instead of fabricating teeth11,12, grains or particles10are used as engagement elements9. These grains or particles are at least partially embedded in the object gripping surface5of gripping element4and will engage the outer surface of the object2(seeFIG. 2) for transferring torque and/or translational force thereto.

According to the embodiments of the invention shown and described above with respect toFIGS. 1–7, an insert1is provided for a clamping device or gripping apparatus (not shown) comprising one or more gripping elements,30that are arcuate or curved, corresponding to the outer shape of the object2to be gripped. The gripping elements4may be inclined, at least slightly, relative to a longitudinal axis7of the insert1. Due to the curvature of the gripping elements, there is a close surface-to-surface contact between the object gripping surface9and the outer surface18of the object2. This curvature and the inclined arrangement of the gripping elements relative to the longitudinal axis7of the insert1allow transfer of high torques and/or translational forces to the moveable object2with a reduced gripping area, while reducing indentations or markings.

The inclination of the gripping elements4relative to the insert1can be realized by arranging the gripping elements4relative to the longitudinal axis7of the object2at an angle8in the range of about 50° –130°. In such a way, the gripping elements4surround the object2like a helix. If transmitting higher torque to the object2, the angle8may be smaller and is preferably in the range of about 70° –110°. Generally, the highest torque can transferred to the object2or tubular if this angle8is about 90°. However, the angle8also depends on the relative arrangement of, for example, teeth11,12with respect to the gripping element4. The teeth11,12may have blade-like tips that extend relative to the lengthwise direction of the gripping element4at an angle8different than 90° or less than 90°. In such a case, it may be advantageous to arrange, for example, the gripping elements4relative to the object2at an angle8of about 100° or an angle of less than 100° in case those blade-like tips are arranged relative to the gripping element4at an angle8of about 80° or an angle of less than 80°. However, a variety of angles8may be used in this respect and the combination just outlined may be particularly suitable but the invention is not limited to such combinations.

According to an embodiment of the present invention, the different gripping elements4,30of one insert1are displaced with respect to each other in the lengthwise direction of the gripping elements4,30. According to another embodiment of the present invention, the angle of inclination is different from one gripping element4,30to the other or for different groups of gripping elements4,30. To simplify the design and to reduce costs, the gripping elements4may be arranged parallel to each other.

If the surface of the object2to be engaged deviates from a regular shape or has, for example, unevenness in curvature, the base material3can have an elasticity which permits compensation for deviations or unevenness of curvature. An example of such a base material3with an elasticity is an elastomeric lining or rubber matrix. By using such a base material3with elasticity, it is possible to ensure there is a consistent engagement between the gripping surface5,9and the surface of the object2or tubular. In one embodiment, the gripping surface5,9of the gripping element4,30is flush with the surface of the base material3. In another embodiment, the gripping surface5,9protrudes from this surface to the object2.

Gripping elements4,30that are easily arrangeable within the base material3and which are also of simple and inexpensive designs are blade or bar-like with engagement elements9on the gripping surface5, as shown inFIG. 7. In some instances, it may be advantageous to form the engagement elements9of a harder material than the rest of the gripping elements4,30. One possibility in this respect is engagement elements9which are grain or particle-like10and are made of at least one material selected from the group comprising: titanium, diamond, glass, ceramics, corundum, or quartz. These grains or particles10can be embedded in the object gripping surface5,9and may partially protrude above this surface5,9thereof.

Because the base material3is elastic, it is also possible that the curvature of the gripping element4,30is initially different than the curvature of the outer surface18of the object2. The different curvatures are then adapted to each other by the elasticity of the base material3such that at least substantially full surface-to-surface contact between object gripping surface5,9and outer surface18of the object2is obtained. It is, of course, also possible that the curvature of the gripping element4,30is complementary to the curvature of the object2. The gripping elements4,30may have a constant radius of curvature wherein they are shaped like a circle, or in the alternative, the radius of curvature may change along a lengthwise direction of the gripping element4,30or in a circumferential direction of the object2. In this manner the elasticity of the base material3compensates for misalignments, and the insert1can, in some instances, be designed to initially be misaligned but to then place additional force on a certain area of the object2or tubular as the elastic base material3is reformed during the gripping operation.

Instead of grains or particles10as engagement elements9, it is also possible to use a plurality of teeth11,12on the object gripping surface5. To simplify the design of such engagement elements9, all teeth11,12may have the same depth13and same angles of leading and trailing faces14,15.

To hold the object2in more than one plane corresponding to the extension of the gripping element4, the teeth11,12may be interlaced. One possibility is that every second tooth11,12is interlaced with respect to the other teeth11,12or that in a group of three teeth11,12, the second and third teeth11,12are interlaced with respect to the first tooth11,12and are also interlaced relative to each other. Of course, there are more possible combinations of interlaced teeth11,12.

Another design possibility to permit clamping the object2in more than one plane corresponding to the lengthwise direction of the insert1is to provide a gripping element16with a wave-like curvature in its lengthwise direction, as discussed above. Such a wave-like curvature is, for example, sinusoidal. The wave-like curvatures of neighboring gripping elements4may thus be in phase or out of phase.

To simplify the arrangement of the inserts1within corresponding jaws (not shown) of the clamping device (not shown) and to facilitate the gripping of an object2such as a tubular body, each insert1may only partially surround the object2such that two, three, or more inserts1are arranged around the object2for holding the object2along its circumference18. If the insert1comprises the housing19for releasably holding the base material3with gripping elements4, the housing19can be fixed to corresponding jaws of tongs, spiders, elevators, torque heads, and spears, and also may be exchanged for replacement.

Because the gripping elements4are preferably arcuate-shaped, as described above, the housing19is also preferably an arcuate member with a cavity20formed in its inner surface for receiving the base material3having gripping elements4. Curvature of the arcuate member or housing19preferably corresponds to the curvature of the gripping elements4.

To securely hold the different gripping elements4and the base member3, the cavity20is limited by the back wall22and side walls23,24, wherein a plurality of ribs25protruding toward the base member3are arranged on the back wall22. The ribs25can be arranged perpendicular to the gripping elements4or may at least be inclined with respect to the lengthwise direction of the gripping elements4.

According to an aspect of the invention, the forces introduced into the gripping elements4are mainly distributed in their lengthwise direction. To support the gripping elements4and to allow transmission of high force, the side walls23,24may be employed as supports for first and second ends26,27of each gripping element4. To surround the cavity20and to further support base material3and gripping elements4, the housing19may further comprise top and bottom walls28,29limiting the cavity20, and the top and bottom walls28,29may be releasably fixed to the back wall22.

According to a particular arrangement of the gripping elements4, the gripping elements4of the present invention may be cast and/or forged out of an essentially linear gripping element30to obtain its curvature. The transformation may be accomplished by hot or cold forging, for example. The original gripping element30may have a simple design and may be inexpensive.

According to another aspect of the invention shown inFIGS. 8–11, engagement elements160are attached to a gripping surface150of a curved, malleable substrate103to form a gripping member150for insertion into a gripping apparatus. The resulting gripping member150has frictional characteristics to allow it to effectively grippingly engage an object such as a tubular, casing, liner, expandable tubular, pipe, or drill pipe (not shown) in order to provide torque to the object, with minimal damage to the object on the surface which is gripped. The flexible substrate103is preferably a metal with lower hardness than steel, so that the engagement elements allow metal-to-metal contact with the object2with decreased abrasiveness to the object.

In an alternative embodiment of the present invention shown inFIGS. 8–9, an insert101includes an insert housing119with a back wall122, side walls123and124, and top and bottom walls128and129, as shown inFIG. 8. A cavity120is formed by the walls122,123,124,128, and129, into which a gripping member150is insertable (see alsoFIG. 9). The top and bottom walls128and129of the insert housing119may be releasably fixed to the back wall122to facilitate replacement of the gripping member150when desired or needed. The gripping member150includes a base material103and engagement elements160thereon (seeFIG. 9). The cavity120is preferably less in depth than the thickness of the base material103so that the base material103protrudes from the cavity120in the direction of an object102which is to be grippingly engaged (seeFIG. 11) by the gripping member150, as contact of the walls123,124,128, and129with the outer surface of the object102is generally undesirable.

The base material103of the gripping member150is constructed of a flexible substrate, preferably a malleable metal of lower hardness than steel. Most preferably, the base material103is made of aluminum, but the base material103may also be made of copper or brass alloy or a combination of any of the metals. The base material103constructed of a malleable metal is elastic enough to allow it to conform to the object102to be gripped by the gripping member150, thus permitting compensation for deviations or unevenness of curvature in the object102to be engaged by the gripping member150and providing metal-to-metal contact between the base material103and the object102being grippingly engaged. The object102to be held by the gripping member150may include, but is not limited to, casing, liners, tubing, pipe, drill pipe, expandable tubulars, or other tubulars.

FIG. 9shows a downward, cross-sectional view along line9—9ofFIG. 8of the gripping member150. Referring primarily toFIG. 9, the base material103is curved into an arc which corresponds to the curvature of the outer surface of the object102. The curvature of the base material103may be accomplished by, for example, casting or forging. The base material103may be essentially linear before the casting or forging into the arcuate shape. Because of the malleability of the base material103, the curvature of an inner surface161of the base material103may be adapted to the curvature of the outer surface of the object102to be grippingly engaged by the gripping member150if the curvatures are initially different from one another, as shown inFIG. 11. If the object102to be grippingly engaged deviates from a cylindrical shape or has unevenness of curvature, the base material103malleability nonetheless permits gripping engagement of the object102. In this manner, essentially complete metal-to-metal contact may be obtained between the inner surface161of the base material103and the outer surface of the object102.

To aid in preventing vertical or horizontal displacement of the gripping member150relative to the insert housing119(seeFIG. 8), ribs125may be arranged on an inner surface of the cavity120on the back wall122, and ribs (not shown) which are at least substantially perpendicular to the ribs125may be arranged on an outer surface121(seeFIG. 9) of the base material103. Any other method of retaining the gripping member150within the cavity120is contemplated for use with the present invention.

As shown inFIGS. 8 and 9, engagement elements160are attached to the inner surface161of the base material103, the inner surface161being the surface of the base material103directly contacting the object102, or the gripping surface, in use. The engagement elements160may protrude outward toward the object102from the inner surface161of the base material103or may be substantially flush with the inner surface161of the base material103. The engagement elements160may be grains, particles, fragments, or chips of a hard or super-hard material, which may include, although is not limited to, diamond dust, particles of silicon, zircon, tungsten carbide, carborundum, and mixtures thereof; cubic boron nitride, diamond, glass, ceramic, corundum, and quartz particles or grains, and mixtures thereof; thermally stable product; titanium; and polycrystalline diamond composite or natural diamond. The preferred super-hard material for use in the engagement elements160is diamond dust. The engagement elements160may be any hard or super-hard material known to those skilled in the art, including any combination of the above-listed materials.

In one embodiment, a substrate of tape is provided to support diamond dust as the gripping element. A layer of copper is applied to the tape, followed by an application of the diamond dust. The tape is then affixed to a base material, such as by use of an adhesive. The base material may be either an elastomeric material or a malleable metal.FIG. 12provides a perspective view of such a substrate of tape210. A “cutaway” view is seen of a portion of tape210that includes a layer of copper212, followed by a layer of diamond dust214. An insert using the diamond dust214may be formed, in one aspect, by providing a substrate of tape210, applying a layer of copper212to the tape, applying diamond dust214over the copper layer212, and then affixing the tape onto the base material (not shown inFIG. 12).

The engagement elements160are shown inFIGS. 8–10as substantially sphere-shaped. In the alternative, the engagement elements160may be cube-shaped, rectangular in shape, or of any other shape capable of grippingly engaging the object102when the object102is placed in contact with the engagement elements160, as described below. The engagement elements160may be uniformly dispersed on the base material103or randomly dispersed, to form any pattern which allows effective gripping engagement of the object102. Likewise, any number of engagement elements160which allow effective gripping engagement of the object102may be utilized.

Several methods of attaching the engagement elements160to the inner surface161of the base material103are contemplated. A first method involves welding the engagement elements160onto the inner surface161of the base material103, then spray fusing, or flame spraying, a binding material around the engagement elements160. The initial welding of the engagement elements160temporarily holds the engagement elements160to the inner surface161prior to the application of the binder material through spray fusing. The temporary attachment of the engagement elements160by welding allows the engagement elements160to be located in a specific pattern on the base material103, the pattern subsequently maintainable through the binder process of spray fusing. Spray fusing involves applying a binding material around the engagement elements160to provide a permanent binding medium for the engagement elements160to the inner surface161of the base material103. This method is suitable for use with engagement elements160that are hard materials, such as tungsten carbide, as these engagement elements160are electrically conductive and capable of spot welding.

With respect to super-hard materials such as diamond dust, which generally are not electrical conductors (but are electrical insulators), an additional step prior to the welding may be accomplished if the desired method is welding. The additional step may involve combining the engagement elements160with an electrically conductive component to facilitate the welding. After combining the engagement elements160with the electrically conductive component, the welding of the electrically conductive component may be accomplished by spot welding using electrical resistance techniques known to persons skilled in the art. The electrically conductive component may be a coating on the surface of the engagement elements160to be attached to the inner surface161, including, but not limited to, nickel, copper, brass, or chromium-based alloy, and the electrically conductive component may be applied to the engagement elements160via electroplating. The electrically conductive component may alternatively be a metallic substrate having locating means for holding the super-hard materials in place during the spray fusing process. As shown inFIG. 10, the electrically conductive component may also be a mesh framework175, preferably made of metal, used to locate the engagement elements160until they are permanently anchored by the application of the binder material through spray fusing.

In another embodiment, the electrically conductive component may be used to attach the engagement elements160to the inner surface161by heating within an oven. In a particular embodiment, the base material103is aluminum, the engagement elements160are diamond dust, and the electrically conductive component is brass. A layer of brass is placed on the inner surface161, then the engagement elements160are placed on the inner surface161and heated in an oven at, for example 2200–2800° F.

In initially fixing the material to the inner surface161before spray fusing, a high-temperature adhesive may be utilized instead of welding or heating within an oven. Before applying the engagement elements160to the inner surface161, the high-temperature adhesive is preferably applied to the engagement elements160using a syringe, but in the alternative, the hard or super-hard material may be coated with the high-temperature adhesive prior to affixing the hard or super-hard material to the inner surface161. As an alternate method of using the adhesive to attach the engagement elements160to the inner surface161, the high temperature adhesive may be applied or coated, for example through brushing, onto the inner surface161, and the engagement elements160may be subsequently applied to the adhesive-coated inner surface161. After attaching the engagement elements160to the inner surface161with the high-temperature adhesive, spray fusing with a binder material may be utilized to permanently anchor the engagement elements160to the inner surface161. The high-temperature adhesive may be alumina-based. Preferably, the high-temperature adhesive has the consistency of paint or paste and is a curing adhesive.

In an alternate method of attaching the engagement elements160, in the form of small shaped particles, to the inner surface161, the engagement elements160may be held within a mesh framework175, as shown inFIG. 10. The mesh framework175may be fixed to the inner surface161through use of a high-temperature adhesive having characteristics as described above. Alternatively, the mesh framework175may be made of a suitable alloy that allows it to be readily spot welded to the inner surface161. The engagement elements160are held in location in the mesh framework175by the aid of a corresponding geometry to the mesh spaces. It is also contemplated to coat the engagement elements160with an electrically conductive component (see above) prior to insertion within the mesh framework175to more securely fix the engagement elements160to the mesh framework175for subsequent spray fusing of the binder material. The mesh framework175advantageously maintains suitable spacing between the engagement elements160. In a further embodiment, the mesh framework175may be placed over the top or on the outside of the engagement elements160and then removed after the spray fusing process has taken place.

An additional method may be utilized to obtain the gripping member150ofFIGS. 8–9which involves attaching hard or super-hard materials in the form of engagement elements160to the inner surface161by brazing. Generally, brazing involves soldering the super-hard materials to the base material103using a hard solder with a high melting point. Other methods of attaching the engagement elements160to the inner surface161include, but are not limited to, flame-spraying ceramic at the engagement elements160(preferably when the engagement elements160are diamond dust) while the engagement elements160are located on the inner surface161(preferably aluminum), as well as fixing the engagement elements160to the inner surface161merely by welding, shrink-fitting, or electroplating, which methods are known by those skilled in the art, without the spray fusing thereafter as described above.

Referring again toFIGS. 8–9, another method for attaching the engagement elements160to the inner surface161is powdered metallurgy or sintering, which is a process generally known to those skilled in the art. Sintering involves placing the engagement elements160(preferably diamond dust), which may be powdered, into a mold in the ultimately desired locations. Next, the metal base material103, in powdered form, is packed into the mold above the engagement elements160. Pressure and heat is applied to the mixture, causing diffusionary bonding between the metal materials. The gripping member150results, wherein the engagement elements160are located on the inner surface161usually in a similar pattern to the initial pattern placed into the mold. The advantage of sintering is that even when the pattern of engagement elements160on the inner surface161is non-homogeneous, the constituents stay generally in place through the process.

In a yet further alternate method for attaching the engagement elements160to the inner surface161, a jet may be utilized to blow gases at very high speeds towards the inner surface161, and the engagement elements160may be introduced into the gas stream. Typically, a speed in the region of Mach 2 is used. The kinetic energy of the procedure is converted to thermal energy which welds the engagement elements160to the inner surface161.

An alternate method for attaching the engagement elements160to the inner surface161involves placing the engagement elements160within a mold and thereafter pouring the material used to make the base material103, e.g. aluminum, in molten form into the mold, so that the engagement elements160are set in the base material103upon cooling.

The present invention is not limited to the order in which the steps of affixing the engagement elements160to the inner surface161and inserting the gripping member150into the housing119and the gripping apparatus (not shown) are performed. The engagement elements160may be attached to the inner surface161prior to insertion of the gripping member150into the gripping apparatus. It is equally contemplated that the engagement elements160may be attached to the inner surface161after the insert101(or the insert1) is located within the gripping apparatus.

In use, the gripping member150is formed by attaching the engagement elements160to a surface of the base material103which will be used to grippingly engage the object102. InFIGS. 8–11, the inner surface161is used to grippingly engage the object102; however, it is contemplated for use with a spear or similar gripping apparatus to place the engagement elements160onto the outer surface121of the base material103. The engagement elements160may be attached to the base material103by any of the methods described above. Then, the gripping member150is made into an arcuate shape so that it will fit within the cavity120by the methods described above. These two steps may be performed in opposite order also, so that the engagement elements160are attached to the base material103after its formation into an arcuate shape.

Next, the gripping member150is inserted into the cavity120. A previous gripping member may thus be rapidly replaced by inserting the gripping member150into the insert housing119and the gripping apparatus. Next, the object102is inserted into the gripping apparatus, and the gripping apparatus grippingly engages and may rotate and/or translate the object102in the usual manner, depending upon the type of gripping apparatus utilized.

In all of the above embodiments, the inserts1,101may be utilized in any gripping apparatus, including a tong, spider, elevator, or a gripping head such as a torque head or spear. When using the inserts1,101in a spear, the engagement elements160would not be on the inner surface161of the base material103, but on the outer surface121, as a spear grips from the inside of the tubular body. The cavity20,120in the insert housing19,119would similarly face outward rather than inward in the spear or similar gripping apparatus.

In any of the above embodiments, any number of inserts1,101may be inserted in the gripping apparatus or clamping device for placement around the object2,102to simplify the arrangement of the inserts1,101and to facilitate gripping of the object2,102. The inserts1,101allow for easy replacement in tongs, spiders, elevators, gripping heads, and other apparatus when the need for exchange of the inserts1,101arises. In this manner, two, three, or more inserts1,101may form a generally circular hole through which the object2,102may be inserted. Each insert1,101only partially surrounds the gripped object2,102so that multiple inserts1,101are arranged around the object2,102for holding it along its circumference (seeFIGS. 2 and 11). Within the gripping apparatus, one or more inserts1may be combined with one or more inserts101to envelope the object2,102. Furthermore, the inserts1,101are not limited to forming a circular pattern within the gripping apparatus, but may also form a rectangular or square pattern to grip a rectangular pipe, for example, or may form any other shape. In use within a gripping apparatus, any of the above embodiments may be arranged within an adaptor to form a generally circular hole for object2,102insertion. The inserts1,101may also be stacked on top of one another longitudinally along a length of a tubular body to increase gripping power.