~ 16'7025 ~ACKG~OUND OF THE INVENTION
In well drilling operations, a power tong is used to grip and rotate lengths of pipes, rods or other axially elongated bodies for the purpose of connecting together or disconnecting threaded end sections of such bodies. In the usual case, the tong is of the open-headed type having a housing with a central opening and an outward-open passageway or throat which permits the tong to be positioned around a pipe joint without the necessity of lowering the tong over a length of pipe.
When the tong is operated, pipe-gripping means (often referred to as jaws) are caused to revolve around the aforesaid central opening, these jaws causing the pipe or axially elongated obiect being gripped thereby to axially rotate. Looking at the gripping action of the jaws in more detail, most tongs accomplish the grip by means of a rotor which forces a cam which is attached to the jaw frame to lock into position against a cam surface along the inside surface of the rotor. The action of the cam against the cam surface forces the jaw radially or pivotally radially inward causing a die assembly to engage the pipe. The smaller the cam angle the greater the gripping force produced; however, reduced cam angles can often lead to forces which will deform the pipe. In prior tongs, many attempts to reduce the cam angle have failed because it was not possible to effectively limit the camming angle reduction. Since the range of variance of 0 2 ~
the cam angle which can be practically used is small, jaw assemblies have very limited ranges of pipe radii that they can be used upon. Accordingly, an object of the present invention is to provide a jaw assembly and a power tong incorporating the same with a primary and a secondary camming function which permits a reduced angle for the primary camming function; thereby increasing grip and decreasing slippage.
Another object of this invention is to provide a jaw assembly and a power tong incorporating the same which allows the cam angle of the primary camming function to be reduced, however, limiting the reduction and preventing damage to pipe or similar axially elongated objects.
Yet another object of this invention is to provide a jaw assembly and a power tong incorporating the same which allows the jaw assembly to be used for a greater range of pipes or similar cylindrical objects, therefore saving time and money from unneeded changes in equipment mandated by different pipe sizes.
These together with other objects and advantages of the invention will become more apparent upon reading the undergoing specification and claims.
SUMMARY OF THE INVENTION
The jaw assembly provided in accordance with the present invention in a power tong provides a dual camming action by providing a second camming action caused 6 ~025 by relative movement between the die assembly and the jaw frame, thereby reducing the primary cam angle and increasing gripping force. The jaw assembly also increases the range of a given pair of jaws in a tong assembly. The inventive jaw assembly and resultant power tong will mainly be described in a preferred embodiment of jaw assemblies with the cam follower being rotatably mounted to the rear of the jaw frame and the jaw ~rame being pivotally mounted to the drag assembly (sometimes referred to as a drag drum, carrier member, drag plate or plate member), however, this invention also covers a power tong where the jaw frame is slidably mounted in radial interstices of the drag assembly. This new invention may also be used when the cam follower is rigidly or rotatably connected to a lever arm which is pivotally connected to the rear of the jaw frame and the same lever arm is pivotally connected to the drag assembly.
The basic parts of this invention are a jaw frame, a die assembly slidably mounted to the jaw frame and a cam follower means. The die assembly preferably is mounted to the front portion of the jaw frame which is the side closest to the cylindrical object to be rotated, and the cam follower means is preferably connected to the rear portion of the jaw frame. On a rotary power tong the gripping force applied to the pipe is developed by the cam follower cooperating with a cam surface portion of the power tong to impart a primary camming action of the jaw frame into and out of engagement with an axially elongated body. With this inventi.on the jaw of a power tong works as previously described; however, we add to this a second camming action caused by the relative motion between the die assembly and the jaw frame.
The above and other objects and features of the invention will become apparent in the following detailed description of several preferred embodiments of the invention taken in connection with the accompanying lQ drawings which are part of the specification and in which:
figure 1 is a plan view partially in section, o~ the jaw assembly of one preferred embodiment of the invention;
Figures 2 and 3 show operation of the tong illustrated in Figure 7;
Figure 4 shows an alternative embodiment of the invention wherein the cam follower means includes a lever arm pivotally connected to the rear portion of the jaw frame;
2Q Figure 5 shows an alternative embodiment of the invention in which a jaw assembly is slidably mounted in radial interstices of the drag assembly;
Figure 6 is a plan view of a die assembly of the instant invention;
Figure 7 is a plan view of a tong incorporating a preferred embodiment of the inventive jaw assembly.
With reference now to the drawings with particular attention to Figures 1, 6 and 7. Figure 1 in detail shows construction of the jaw assembly itself. The jaw assembly 1 is mainly comprised of three basic parts.
The parts are the jaw frame 2, the die assembly 17, and the cam follower means 18. The front portion of the jaw frame 2 is that portion which is orientated towards the axially elongated body 26 to be rotated. The jaw frame 2 is made up of a main body portion 19 and spaced apart upper and lower side portions 20. The side portions 20 form between themselves a groove 43 which the die assembly 17 mounts within as will later be described. The side portions 20 also have a crescent shaped slot 15 wherein the concave surfaces of the slot are directed towards the axially elongated body 26 to be rotated.
The die assembly 17 mainly comprises three basic parts. The main part of the die assembly 17 is the die holder 3. The die holder 3 is retained within the upper and lower side portions 20 by virtue of a pin 7 which connects with the die holder 3 and is retained within the crescent shaped slot 15. The portion of the die holder 3 which always rides within the groove 43 formed from upper and lower side portions 20 is called the tongue 10. The preferred embodiment has a groove 43 formed by the upper and lower side portions 20. The upper and lower side portions 20 of the preferred embodiment are substantially in the form of a plate and are positioned ~ 16702~
parallel to each other to form the groove 43; however, the groove 43 could be formed by machining an offset directly on the jaw frame 2 itself or the upper and lower side portions 20 could be made to be converging while the die holder tongue 10 could be made with a taper which fits within the tapered groove 43 formed by the modified upper and lower side portions 20. The second part of the die assembly 17 is the die insert 6 which makes direct contact with the cylindrical or axially elongated body 26. The die inserts 6 in the preferred embodiment fit into a slot 21 made in the die holder 3. The third part of the die assembly 17 is the washer head screw 9 which retains the die insert 6 within the die holder 3. If one desired the die inserts 6 can be eliminated and the die teeth 44 can be machined directly out of the die holder 3, however, die inserts 6 allow the die teeth 44 to be replaced without changing the die holder 3. It is also possible to have detachable die inserts 6 without having the slots 21 formed on the die holder 3.
The die assembly 17 is maintained in a neutral position by a biasing means. For example, Figure 1 shows a coil spring 8 captured between the jaw frame 2 and the die assembly 17 as the biasing means. In a preferred embodiment two springs 8 are used in order to urge the die assembly 17 to a neutral position from either direction, however, only one is illustrated in Figure 1.
To limit the relative motion between the die assembly 17 and the die holder 3 stopping means are utilized. Since the stopping means limit relative motion, it also limits the decrease in cam angle therefore preventing damage to the axially elongated body 26. In Figure 1 the stopping means comprises the tongue 10 making contact with the jaw frame landing 16.
In the preferred embodiment the die assembly 17 is slidably mounted in a circular curvature surface of contact 5. Although other surfaces may work a circular curvature surface of contact 5 will allow continuous line contact between the die assembly 17 and jaw frame 2. The preferred embodiment also has a circular curvature surface of contact 5 with a radius which is smaller than the radius of the axially elongated body 26 to be rotated.
The focus of the circular surface of contact 5 is located in such a point that when the jaw assembly 17 is engaged upon the pipe relative motion between the die assembly 17 and the ja~ frame 2 generates a camming action which moves 2Q the die assembly 17 radially inward with respect to the axially elongated body 26 being gripped during rotation in either rotary direction. As stated before the radius of the circular surface of contact 5 is smaller than the radius of the axially elongated body 26. When the jaw assembly 1 becomes engaged upon the axially elongated body 26 friction between thè axially elongated body 26 and the die insert 6 causes the die assembly 17 to become fixed.
- 11~7~25 As the jaw frame 2 continues to move in either rotary direction relative motion between the jaw frame 2 and die assembly 17 forces the die assembly 17 towards the axial center of the cylindrical body 26 to be rotated if the focus of the circular surface of contact 5 is located as described (see also Figures 2 and 3). The camming action caused by the relative motion between the die assembly 17 and jaw frame 2 ~referred to as the second camming action when the jaw assembly 1 is placed in a tong) decreases the cam angle and increases the grip. Since grip is increased the jaw assembly 1 can be used for a greater range of axially elongated bodies 26.
The third major element of the jaw assembly 1 is the cam follower means 18. The cam follower means of the preferred embodiment is a circular cam surface contact member 4, such as a roller rotatably mounted to the rear portion of the jaw assembly 2.
Although the preferred embodiment has a cam surface contact member 4 which is rotatably mounted a cam surface contact member 4 rigidly mounted may be used and also the cam surface contact member 4 can be noncircular.
In Figure 1 roller pin 12 is used to mount the cam surface contact member 4 to the rear portion of the jaw frame 2.
Figure 7 shows power tong 22 incorporating the inventlve jaw assemblies. The housing 23 has an opening called a throat 24. Covering the throat 24 is a latch 25 which opens to allow the tong 22 to be placed around the 1 16702~
axially elongated body 260 The latch 25 is then closed to assure safety during operation. Opposite the latch 25 the housing 23 contains drive means for turning the rotor 27.
The drive means may be at any of several types; however, drive means shown in Figure 7 comprises a hydraulic motor 28 through a gear train (not shown) rotating two pinion gears 29 and 30. The pinion gears 29 and 30 mesh with the gear teeth 31 on the outer periphery of the annular rotor 27. The spacing between the pinion gears 29 and 30 insures that the rotor 27 will continue to rotate whenever an opening or throat 47 of the annular rotor 27 is positioned adjacent one of the pinion gears 29 and 300 The annular rotor 27 is carried by the housing 23 and is rotatable relative to the housing 23 about an axis generally perpendicular to the opposite sides of the housing 23. On the inner periphery of the rotor 27 on diametrically-opposite sides are cam surfaces 32~ The cam surfaces 32 may include a neutral surface position 33 allowing the jaw assemblies to open outward for insertion of the tong 22 around the axially elongated body 26. The rotor throat 47 can be aligned with the throat 24 of the housing 2~.
The drag assembly 34 (sometimes called a drag drum or carrier member) is comprised of two generally annular plate members 34A and 34B (hereafter referred to as 34) connected in a parallel fashion and is rotatably mounted within the housing 23 along the same axis of rotation of the rotor 27. The drag assembly 34 also has a throat or opening 48 to align with the throat 47 in the rotor 27 to allow insertion of the axially _g_ .
elongated body 2G. Although the preferred embodiment comprises two plate members bolted together in a sandwich or parallel fashion, one substantial disc shaped member could be used.
In a preferred embodiment the jaw assembly 1 is sandwiched between the two plate members and is pivotally connected to both plate members with a bolt which fits in an aperture 11.
In the alternate embodiment as shown in Figure 4 a drag assembly 35 is pivotally connected to a lever arm 36 and the lever arm 36 is also pivotally connected to a jaw assembly 37. In the alternative embodiment shown in Figure 5 a jaw assembly 38 is placed within radial interstice 39 of a drag assembly 40. As shown in Figure 5 the radial interstice is formed by two wall pieces 41 parallel to each other, attached perpendicular to the plane defined by the plate members and sandwiched between the plate members forming a box or radial interstice for the jaw assembly 38 to be slidably mounted into~
Further regarding operation of the tong 22, in Figure 2 we see the rotor 27 has been rotated in a clockwise direction through cooperation among the gear teeth 31 and the pinion gears 29 and 30, thus causing the cam surface 32 to push against the cam surface contact member 4. As the cam surface contact member 4 becomes locked against the cam surface 32 the ~aw frame 2 is pivotally pushed radially inward engaging the die inserts 6 of the die assembly 17. As the rotor 27 continues to rotate in a clockwise direction relative motion between the jaw frame 2 and the die assembly 17 occurs and the die assembly ` -10-1 ~7~2~
17 moves in a counterclockwise direction relative to the jaw frame 2 causin~ a second camming action. The second camming action is limited by ~he tongue 10 hitting the landing 16.
As the rotor 27 continues to turn with the jaw frame 2 and die assembly 17 engaged a friction means 42 is released or overcome a~lowing the drag assembly 34 to rotate with the jaw assembly 1, axially elongated body 26 and rotor 27.
The preferred embodiment shown in Figure 4 works in the same manner as the aforementioned preferred embodiment except that a cam surface contact member 45 pushes the lever arm 36 which then pushes the jaw frame 37 pivotally inward.
The preferred embodiment shown in Figure 5 works in the same manner as the preferred embodiment described previously except that a cam surface 46 contact member pushes the jaw frame 38 radially inward instead of pivotally inward as in the other preferred embodiment.
Although the invention has been shown in connection with specific embodiments, it will be readily apparent to those skilled in the art that various changes in form and arrangement of parts may be made to suit requirements without departing from the spirit and scope of this invention.