ACTIVE JAW FOR A POWER TONG

Abstract: An active jaw (27) for a power tong (1) is provided with an upper cam (30) and a lower cam (32) which are shaped so that rotation of the rotary (4) relative to the active jaw (27) in either sense from a first position results in the active jaw (27) being applied to a pipe via a roller (35, 36). The active jaw (27) can be released by reversing the direction of rotation of the rotary (4). A peg may be used to limit movement of the active jaw (27) relative to the rotary (4) to prevent the active jaw (27) being reapplied to the pipe. Pipes of different diameters may be griped by using rollers (35, 36) of different diameters and, optionally, different active jaws (27) shaped to grip the pipe. In a second embodiment a brake band (42) acts on a drum (40) which supports the active jaw (27). When the rotary (4) is started the active jaw (27) is restrained from rotation. This relative movement applies the dies (29) on the active jaw (27) to the pipe. Further rotation of the rotary (4) then overcomes the braking force and the rotary (4), drum (40) and active jaw (27) rotate in unison. An adjustable bolt (50) is provided to prevent the active jaw (27) being reapplied when the rotary (4) is reversed.

Description: This invention relates to a power tong, and to an active jaw for such a power tong. During the construction of an oil or similar well it is necessary to connect successive lengths of pipe. This is achieved by a threaded connection. Conventionally, a tool known as a power tong is used for gripping one length of pipe and rotating it relative to the next to make or break the joint. Known power tongs comprise a body, a rotary rotatably mounted in said body and at least one active jaw which, on rotation of the rotary is cammed against a pipe in the rotary and grips it for rotation with the rotary. In known arrangements the camming action is generated by a cam member which is bolted to the rotary and is shaped so that the active jaw will be cammed against the pipe on rotation of the rotary relative to the active jaw in one sense and will be released on rotation of the rotary relative to the active jaw in the opposite sense. In order to reverse the screwing direction of one known power tong with only one active jaw, the active jaw must be removed and remounted on the opposite side of the rotary. On rotation of the rotary relative to the active jaw in the opposite sense the active jaw is cammed against the pipe by a second cam member. This is a time-consuming process. Furthermore, the power tong must be removed from a pipe to enable the active jaw to be moved. In another known power tong (US-A-3 589 742) two cam members are bolted to the rotary. When the rotary is rotated relative to the active jaw in either direction from a neutral position the active jaw is applied to the pipe. Another problem with known arrangements is that they can only be used in relation to a very limited range of pipe sizes. Outside of this range the jaws do not grip the pipe properly and, as a result, the surface of the pipe becomes damaged. One solution too this problem has been to use different cam members for gripping pipes of different sizes. However, removing and replacing cam members is a time-consuming exercise. Furthermore, the range of pipe sizes which can be gripped satisfactorily cannot be substantially increased by this method. According to the present invention there is provided a power tong having a rotary, an active jaw, means to apply said active jaw to a pipe, and means to inhibit movement of said active jaw relative to said rotary, said means comprising a brake member which carries said active jaw in a manner such that said active jaw is restrained against rotation by said brake member but can move radially of said power tong, and wherein said brake member comprises a drum, part of which is surrounded by a brake band, characterised in that said active jaw is provided with a tongue which extends generally parallel to the rotational axis of said rotary and said drum is provided with a recess to accommodate said tongue. Preferably, said power tong includes a spring to bias the active jaw outwardly. Advantageously, said active jaw is provided with a first cam surface which, in use, urges said active jaw against a pipe when said rotary is rotated in one sense from a first position, and a second cam surface which, in use, urges said active jaw against said pipe when said rotary is rotated in the opposite sense from the first position. Preferably, said first cam surface and said second cam surface comprise part of a first cam. Advantageously, said power tong further comprises a second cam which has a first cam surface and a second cam surface which correspond to the first cam surface and the second cam surface of said first cam and, in use, is vertically spaced therefrom. Preferably, said active jaw further comprises a top plate having a handle for manipulating said active jaw. Advantageously, said active jaw is movably mounted on a first piece which is fast with the rotary. Preferably, a roller is rotatably mounted on said first piece for engaging said first and second cam surfaces. Advantageously, means are provided to limit movement of the active jaw relative to the rotary. Preferably, said means to limit movement of the active jaw relative to the rotary comprises a bolt mounted in or on said brake member and which can be moved to project into an opening in said rotary, relative movement between said rotary and said active jaw being limited by engagement of said bolt with an extremity of said opening. The present invention also provides an active jaw for a power tong in accordance with the invention, characterized in that said active jaw is provided with a tongue which, in use, extends generally parallel to said pipe and can be accommodated within a recess in the brake member. For a better understanding of the invention reference will now be made, by way of example, to the accompanying drawings, in which: Figure 1 is a plan view of one embodiment of a power tong incorporating an active jaw in accordance with the invention; Figure 2 is a section taken on line II-II of Figure 1; and Figure 3 is an exploded view showing some of the parts of the embodiment shown in Figures 1 and 2. Referring to the drawings there is shown the front end of a power tong which is generally identified by reference numeral 1. The power tong 1 comprises a body 2 having an opening 3 through which a pipe can be introduced into the pipe receiving recess of a rotary 4. The rotary 4 is rotatably supported in the body 2 by a plurality of rollers 5-14 and can be rotated by a hydraulic motor (not shown) acting through a gear train including gear wheels 15 and 16 which act on a toothed member 17 which extends around the periphery of the rotary 4 with the exception of the pipe receiving recess therein. A jaw assembly 18 is mounted on the rotary 4 and is secured thereto by four bolts 19, 20, 21, 22. The jaw assembly 18 comprises a first piece 23, a second piece 24 and a third piece 25. The second and third pieces 24 and 25 are pivotally mounted on bolts 22 and 19 and can be pivoted to a closed position as shown. The third piece 25 carries a passive jaw 26 which is slidably mounted on the third piece 25 within the confines of a slot 127. The first piece 23 carries an active jaw which is generally identified by reference numeral 27. The active jaw 27 comprises a recess 28 containing a die 29. As better shown in Figure 2, the active jaw 27 is provided with an upper cam 30 and a lower cam 31. Both the upper cam 30 and the lower cam 31 are provided with corresponding first and second cam surfaces. As shown in Figure 1, the upper cam 30 has a first cam surface 32 and a second cam surface 33. A pin 34 extends through the first piece 23 into the top of the rotary 4 and supports two rollers 35 and 36. The pin 34 is prevented from rotating by a grub screw 37. Referring to Figures 2 and 3, the bottom of the active jaw 27 is provided with a tongue 38 which fits snugly in a recess 39 in a drum 40. The drum 40 has a skirt 41 which is surrounded by a brake band 42 which is secured fast to the body 2 of the power tong. The die 29 is secured to the active jaw 27 by a bolt 43 and the unit thus formed is biased towards rollers 35 and 36 by a strong spring 44 which is mounted in a groove 45 in the drum 40. The groove 45 has a circumferential portion 46 and two upwardly extending portions 47 and 48 which can best be seen in Figure 3. In use, the rotary 4 is first rotated until its pipe receiving recess (not shown) is aligned with the opening 3 in the body 2. The second and third pieces 24 and 25 are then swung open so that the power tong 1 can be manoeuvred into position in which the pipe to be rotated is in the centre of the rotary 4. The third and second pieces 25 and 24 are then swung to their closed position as shown in Figure 1. Hydraulic fluid is then admitted to the hydraulic motor to commence rotation of the rotary 4 in one sense, for example anti-clockwise as viewed in Figure 1, via toothed member 17. Since first piece 23 is bolted to rotary 4 it also rotates anti-clockwise. However, drum 40, and consequently active jaw 27, are constrained against rotation by brake band 42. As first piece 23 rotates relative to active jaw 27 the rollers 35 and 36 move along second cam surface 33 which, in this embodiment, has a pronounced angle. As this happens the die 29 moves inwardly and securely grips the pipe. As the rotary 4 moved further anti-clockwise the force exerted by the rollers 35 and 36 on the second cam surface 33 of the active jaw 27 is sufficient to overcome the force applied by the brake band 42 and the rotary 4, jaw assembly 18 and drum 40 rotate in unison. When the rotary 4 is turned clockwise the pipe is released. However, to prevent the die 29 on the active jaw 27 being driven back into engagement with the pipe the skirt 41 of the drum is provided with a bore 49. A bolt 50 is slidably mounted in bore 49 and can be slid along the bore 49 by a knob 51 which projects through a slot 52. The ends of the bolt 50 are provided with flats 53 and 54 and, in the present case, flat 53 projects outwardly from the bore 49 into a slot (not shown) in the rotary 4. When the rotary 4 rotates clockwise it moves relative to the drum 40 until the flat 53 engages the end of the slot. This corresponds to rollers 35 and 36 contacting the centre of the active jaw 27. In order to reverse the direction of rotation of the pipe the bolt 50 is slid until the flat 54 projects from the other end of the bore 49 into a second slot (not shown) in the rotary 4. The second slot does not inhibit the die 29 being driven into gripping and rotating engagement with the pipe. It does, however, limit relative movement between the active jaw 27 and the rollers 35, 36 when the direction of rotation of rotary 4 is reversed. Whilst the arrangement disclosed will work satisfactorily over a range of pipe sizes it will not apply sufficient pressure to adequately grip small diameter pipes. In order to accommodate such pipes the passive jaw 26, active jaw 27 and the rollers 35 and 36 are first removed. Larger diameter rollers are then installed and appropriately shaped active and passive jaws fitted. It will be noted that the point of contact between the larger diameter roller and the active jaw is closer to the centre of the power tony. This is highly desirable. Various modifications to the arrangements described are envisaged. Thus, whereas the preferred embodiment has been described in combination with a jaw assembly 18 which is mounted ON rotary 4, jaws in accordance with the invention can also be used with conventional tongs in which the jaws are mounted IN the rotary. Furthermore, the active jaw 27 shown in Figures 1, 2 and 3 could be provided with a top plate and handle to facilitate extraction of the die 29 from a soft pipe. The slot (not shown) in the drum 40 could also comprise a recess, hole or other form of opening if desired.

Claims: A power tong having a rotary (4), an active jaw (27), means (35) to apply said active jaw (27) to a pipe, and means (40, 42) to inhibit movement of said active jaw (27) relative to said rotary (4), said means (40, 42) comprising a brake member (40) which carries said active jaw (27) in a manner such that said active jaw (27) is restrained against rotation by said brake member (40) but can move radially of said power tong and wherein said brake member (40) comprises a drum, part of which is surrounded by a brake band (42), characterised in that said active jaw (27) is provided with a tongue (38) which extends generally parallel to the rotational axis of said rotary (4) and said drum (40) is provided with a recess (39) to accommodate said tongue (38). A power tong as claimed in Claim 1, including a spring (44) to bias the active jaw (27) outwardly. A power tong as claimed in Claim 1 or 2, characterised in that said active jaw (27) is provided with a first cam surface (32) which, in use, urges said active jaw (27) against a pipe when said rotary (4) is rotated in one sense from a first position, and a second cam surface (33) which, in use, urges said active jaw (27) against said pipe when said rotary (4) is rotated in the opposite sense from the first position. A power tong as claimed in Claim 3, characterised in that said first cam surface (32) and said second cam surface (33) comprise part of a first cam (30). A power tong as claimed in Claim 4, characterised in that it further comprises a second cam (31) which has a first cam surface and a second cam surface which correspond to the first cam surface (32) and the second cam surface (33) of said first cam (30) and, in use, is vertically spaced therefrom. A power tong as claimed in any preceding claim, characterised in that said active jaw (27) further comprises a top plate (39) having a handle (41) for manipulating said active jaw (27). A power tong as claimed in Claim 5, characterised In that said active jaw (27) is movably mounted on a first piece (23) which is fast with the rotary (4). A power tong as claimed in Claim 7, characterised in that a roller (35) is rotatably mounted on said first piece (23) for engaging said first and second cam surfaces (32, 33). A power tong as claimed in Claim 7 or 8, characterised in that means are provided to limit movement of the active jaw (27) relative to the rotary (4). A power tong as claimed in Claim 9, characterised in that said means to limit movement of the active jaw (27) relative to the rotary (4) comprises a bolt (50) mounted in or on said brake member (40) and which can be moved to project into an opening in said rotary (4), relative movement between said rotary (4) and said active jaw (27) being limited by engagement of said bolt (50) with an extremity of said opening. An active jaw for a power tong as claimed in any preceding Claim, characterized in that said active jaw is provided with a tongue (38) which, in use, extends generally parallel to said pipe and can be accommodated within a recess in the brake member (40).

Inventors: SCHULZE-BECKINGHAUSEN, JOERG, ERICH, Schulze-Beckinghausen, Jörg, Erich
Applicants: WEATHERFORD-PETCO, INC.
Application year: 1989
Main classification: E21B19
IPC codes: E21B19