CA1125737A - Power tong - Google Patents
Power tongInfo
- Publication number
- CA1125737A CA1125737A CA344,326A CA344326A CA1125737A CA 1125737 A CA1125737 A CA 1125737A CA 344326 A CA344326 A CA 344326A CA 1125737 A CA1125737 A CA 1125737A
- Authority
- CA
- Canada
- Prior art keywords
- rotary gear
- pipe
- cam surfaces
- circle
- cam
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Landscapes
- Load-Engaging Elements For Cranes (AREA)
- Bending Of Plates, Rods, And Pipes (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
An open-mouth power tong of the type used to make up and break out threaded connections between tubular members is provided herein. It includes a frame, a power driven rotary gear, a pair of pivotally mounted jaws, a cam follower and pipe gripping elements an improved mechanism de-fined by cam surfaces is provided for properly aligning the pipe when it is gripped by the tong so that the pipe may be rotated evenly about its axis.
An open-mouth power tong of the type used to make up and break out threaded connections between tubular members is provided herein. It includes a frame, a power driven rotary gear, a pair of pivotally mounted jaws, a cam follower and pipe gripping elements an improved mechanism de-fined by cam surfaces is provided for properly aligning the pipe when it is gripped by the tong so that the pipe may be rotated evenly about its axis.
Description
~ 573'7 E~C~G OUND O F T~IE INVENTION
1. Field of the Invention The present invention relates to power wrenches and more specifically to power tongs for making up and breakinq out threaded connections between adjoining tubular members.
In particular, the invention relates to a mechanism for bringing the gripping elements of an open mouth power tong into secure and uniform engagement with the pipe so that the pipe may be rotated evenly about its axis.
1. Field of the Invention The present invention relates to power wrenches and more specifically to power tongs for making up and breakinq out threaded connections between adjoining tubular members.
In particular, the invention relates to a mechanism for bringing the gripping elements of an open mouth power tong into secure and uniform engagement with the pipe so that the pipe may be rotated evenly about its axis.
2. Descri~ion of the Prior Art Oil field tubular members, e.g. drill pipe and casing, are employed in sections which are joined together at their ends by threaded connections. Power tongs of the type herein described are utilized to make up and break out these threaded connections by securely gripping one tubular member and ro-tatably driving that member relative to the adjoining member.
Power tongs representative of present practice in the industry are described in U.S. Patent Nos. 2,879,680;
Power tongs representative of present practice in the industry are described in U.S. Patent Nos. 2,879,680;
3,180,186; 3,261,241 and 4,084,453. It has been found that the camming action typically used to bring the gripping elements or dies into contact with the pipe results in fre-quent misalignrnent of the pipe relative to the center of rotation of the tong. That is, the pipe often is not ro-tatably driven about its axis. This misalignment and the resultant vibrations place a severe limitation on the rota-tional speed which may be imparted to the pipe and, in extreme cases, may result in damage to the pipe or tong and a safety hazard to the operator. Thus, there is a need for a power pipe tong having means for securely and uniformly engaging the pipe in such a manner that the pipe may be rotated evenly about its axis.
73~7 ~ n object of a primary aspect of the present invention is the provision of a power tong having means for bringing the gripping e]ements into secure and uniform engagement with the pipe so that the pipe may be rotated evenly about its a~is to prevent dangerous vibrations.
An object of another aspect of th;s ;nvention is the provision of opposed cam surfaces presenting different curvatures in order to com-pensate for t-he different angles at which the cam followers attack their respective cam surfaces during make up and break out operations.
In accordance with one aspect of the present invention a novel open-mouth power tong is provided comprising a frame having a throat at its front; a power-driven rotary gear having a mouth adapted for alignment with the throat, the rotary gear being rotatably mounted on the frame; a pair of pivotally mounted jaws located on opposite sides of the center line of the tong and having their pivot points rearward of the center of rotation of the rotary gear; a cam follower associated with each jaw; pipe gripping elements carried by the jaws; and at least one pair of opposed cam surfaces on the interior surface of the rotary gear, the cam surfaces of the pai}
being cooperatively shaped such that when th-e cam followers are cammed at points along the opposed cam surfaces the jaws are positioned so that a ~0 pipe section gripped therebetween is centered within the rotary gear; at least one pair of opposed cam surfaces comprising a first cam surface de-fined by a portion of a first circ]e having its center on the line X which is perpendicular to the centeriine of the throat and passes through the center of the rotary gear, and a second cam surface defined by a portion of a second circle having a smaller radius than the first circle, with the center of the second circle located at the opposite side of the throat centerline and being offset from line X.
. 4 -i737 By a variant thereof, tlle pair of jaws are pivoted at points symmetrically located about the centerline of the tong and the jaws and their associated pipe gripping elements are substantially the same shape and size, and wherein the opposed cam surfaces are cooperatively shaped such that when the cam followers are cammed at points along the opposed cam surfaces the opposed jaws will have pivoted toward the pipe section through substantially the same angle.
By another variant, the power tong includes two pairs of opposed cam surfaces, a first pair for joint make up and a second pair of joint break out.
By another aspect of this invention, an improvement is provided in a power tong of the type having a frame with a pipe-receiving throat, a rotary gear mounted on the frame, means for rotatably driving the rotary gear, cam means on the inner surface of the rotary gear comprising two pairs of opposed cam surfaces, a pair of pivotally mounted jaws carrying dies for biting into the exterior of the pipe, and a cam follower associated with each jaw for riding on the cam surfaces and urging the dies into bit-ing engagement with a pipe section, improved cam means wherein each pair of opposed cam surfaces comprises first and second diametrically opposed 2~ cam surfaces, said first opposed cam surface being defined by a portion of a first circle having its center on the line X which is perpendicular to the centerline of the throat and passed through the center of the rotary gear, and the second opposed cam surface being defined by a portion of a second circle having a smaller radius than the first circle, with the cen-ter of the second circle located at the opposite side of the throat center-line and being offset from line X.
By another aspect of this invention a rotary gear is provided for use in a power tong of the type having opposed jaws pivotaliy mounted ~ t~
' ~
- for being brought into gripping engagement with a pipe s2ction by o?er;tion ~- 5 -57~'7 of cam followers adapted to ride on cam surfaces on the in~erior surface of a rotary gear, said rotary gear comprising: means for being rotatably driven about a central gear a~is by a suitable drive train; a central open-ing for housing a pipe section being gripped for rotation, said opening dcfining a rotary gear interior surface; an aperture for al-ignil-g w;th t:he [open-]mouth of the tong during p;pe loading and ullload~ g and at ltast one pair of diametrically opposed cam surfaces on the interior surrace of the rotary gear, the first opposed cam surface being defined by a portion of a first circle having its center on the line X which is perpendicular to the center].ine of the tllroat and passed through tihe center of the ro-: tary gear, and the second opposed cam surface being defined by a portion of a second circle having a sma].ler rad;us than the first circle, with the center of the second circle located at the opposite side of the throat centerline and being offset from li.ne X.
-In the accompanying drawings, a -.
r~737 DF~ I ~ r DFSC~ I r I I r~ OF THE DRAWINGS
Figure 1 is a perspective view of an open-mouth power tong constructed in accordance with the present invention.
Figure 2 is a plan view of the pipe-gripping assembly of the tong of the present invention, i.e., the jaws, jaw rollers, gripping dies, and interior surface of the rotary gear, with the jaw~ spread apart in a neutral position to receive a pipe.
Figure 3 is a view similar to Figure ~ showing the pipe securely held by the pipe-gripping assembly with the axis of the pipe at the center of the rotary gear.
Figure 4 is a view similar to Figure 2 showing a typical prior art pipe-gripping assembly.
Figure 5 is a view of the prior art assembly shown in Figure 4 with the pipe gripped off-center.
Figure 6 is a view of a pipe-gripping assembly of the present invention showing enlarged jaws used for gripping : pipe of relatively small diameter.
:
i` . , . ~.~ ~S';~;37 DETAILED DESCRIPTION OF q`HE PREFERRED EMBODIMENT
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ . _ _ , Referring to the drawings and in particular to Figure 1, there is shown in perspective an open-mouth power tong 10 conseructed in accordance with the present invention. Tong 10 includes a frame 12 comprising upper and lower surfaces con-nected by sidewalls. The upper and lower surfaces further include upper and lower cage plates 1~, 16 ~hich pivotally support the jaws as explained below. Frame 12 defines a frontal throat 18 for receiving the pipe sections. When a pipe section is centrally located within the frame during operation, throat 18 is closed off by means of pivotally mounted door members 20, 22 in the manner well known in the art.
The pipe-gripping assembly will now be described with reference to Figures 1-3. A rotary gear 30 is mounted within frame 12 for rotation relative to the frame. Rotary gear t 30 includes gear teeth (not shown3 on its outer periphery so that it may be driven in the manner well known in the ' art, for example, by means of a plurality of of pinion sears (not shown).Th~ pi~ion qear~,- in turn~ ~y be ~uitably dr~ en by an hydraulic drive train as shown, for example, in U.S.
patent no. 2,879,680. The inner surface of the rotary qear 30 includes cam means comprising curved cam surfaces 70, 71, 72, 73 for urging the pipe-gripping elements into contact t with the pipe~ In the illustrated embodiment, the pipe-yripping ele~ents comprise dies 36, 37, 38, 39 mounted on a pair of pivotally mounted ~aws 4~, 46. The jaws are urged toward the pipe by means of ca~ followers comprising jaw _7_ i , . . . .
;!
5~7;~'7 rollers 50, 52 which are rotatably mounted on the jaws by pins 56, 58. Rollers 50, 52 ride on the cam surfaces 70, 71, 72, 73 on the interior of the rotary gear 30.
It will be noted that the jaws are pivotally mounted a~ points P, P' toward the rear of the tong and that the rear dies 36, 38 are near the pivot points so that when a pipe section, for example, pipe section 59, is inserted in the tong, its rearward motion is stopped by dies 36, 38 as shown in Figure 2. The front dies 37, 39 are positioned forward of line X (Figure 2) which is the horizontal line that passes through the axis of rotary gear 30 and is perpendicular to the centerline, CL, of the throat. Thus, when the jaws are urged toward the pipe to the gripping position illustrated in Figure 3, the front dies 37, 39 tend to urge the pipe somewhat rearwardly so that the pipe is gripped both forward and behind line X on both sides of the tong. Stated differently, the dies preferably grip the pipe in each of the four quadrants de-fined by lines X and CL. The rear dies 36, 38 are only slightly displaced during the gripping operation due to their proximity to the jaw pivot points P, P'. However, during the camming operation the angular attitude of rear dies 36, 38 changes substantially so tht the dies contact the pipe at the correct biting angle.
As set forth above, the present invention relates pri-marily to improved means for bringing the dies into a grip-ping relation with the pipe in such a manner that the pipe is centered at the center of the rotary gear, thereby assur-ing relatively even and safe rotation of the pipe during make up and break out operations.
~F
f' , ., ~5737 The improvement of the present invention will be more readily understood after first analyzing a pipe grippin~ assem-bly of the prior art as illustrated in Figures 4 and 5.
According to the illustrated prior art practice, the cam sur-faces on the interior of the rotary gear 30' comprise opposed cam surface pairs 60, 62 and 61, 630 Cam surfaces 60 and 63 form portions of a circle having its center at point C on line X. Cam surfaces 61 and 62 form portions of a circle having its center at point C' on line X. The radii of the four cam arcs are equal; therefore, the curvature of the opposed pair of cams operating in any make up or break out operation will be equal. As discussed above, with the use of the symmetric pipe-gripping assembly illustrated in Figure 4, the jaws 44', 46' must be urged toward the pipe evenly in order for the pipe to be centered as it is gripped. Stated differently, when the pipe is gripped the jaws must have been rotated the same angular amount around their respective pivot points. However, as shown in Figure 5, when the pipe is gripped according to the illustrated prior art practice, the axis of the pipe is not at the center of the rotary gear. This occurs because the opposing jaw rollers 5~', 52' are urged toward the pipe at different rates due to the fact that the opposed cam surfaces, e.g., cam surfaces 60 and 62, are acting on their respective jaw rollers at different "angles of attackn. This phenomenon may be best understood by visualizing the movement of the opposed cam surfaces, e.g. cam surfaces 60 and 62, during a typical make up operation. As the operation begins, the jaw rollers 50', 52' are positioned within the neutral recesses on the opposite sides of the rotary gear. As the rotary gear _g_ ~ - `
~1~57~'7 begins to move, for example in a clockwise direction to the pipe-engaging position illustrated in Figure 5, ca~ surface 60 moves closer to the pivot point P of its respective jaw while cam surface 62 ~ove~ away from the pivot point P' of its jaw, thereby causing the rollers to act on different effec-tive cam pitches. Therefore, the jaw rollers 50', 52' are urged toward the pipe at different rates since the effective pitches of the cam surfaces are different. During a subsequent break out operation, the other pair of opposed cam surfaces, i.e. cam surfaces 61 and 63, will act in a similar manner such that the pipe will be gripped in an off-center manner.
The amount of angular motion of jaws 44', 46' is shown in Figure S where the initial positions of the centers of the jaw rollers 50', 52' are shown as cross marks. As illustrated, jaw 44' ~oves through an angle Y about its pivot point P while jaw 46' moves through an angle Z about its pivot point P'.
Since angle Y is somewhat greater than angle Z, pipe 59 is gripped in the slightly off-center position shown in Figure 5, where reference character M represents the center of rota-tion of the rotary gear 30 and N represents the axis of the pipe. As explained below, a primary object of the present in-vention is to assure that points M and N more nearly coincide.
According to the apparatus of present invention illus-trated in Figures 2 ancl 3, the opposing cam surface pairs, i.e. pairs 70, 72 and 71, 73, are not of equal curvature. As best shown in Figure 2, cam surfaces 70 and 73 define portions of circles having equal radii R2 with their centers at points A, A' on line X. Cam surfaces 71, 72 define portions of circles having equal radii R3 with their curvatures at points r~~-/
B, ~' which are offset from line X. In the illustrated embodiment, the radii R3 are slightly less than the radii R2.
In a particular embodiment of a rotary gear for use on a 7-5/8 inch tong, the nominal radius R4 of the rotary gear is 6-3/8 inches~ R2 is 5.2S inches and R3 i5 5.06 inches with points B, B' being offset from line X at a distance of approximately 0.40 inch.
The operation of the illustrated pipe-gripping assembly can be best appreciated with reference to Figures 2 and 3.
In Figure 2 the jaw rollers 50, 52 rest in the neutral re-cesses as the pipe is received by the tong and moved into contact with the back dies 36, 38. As the rotary gear is rotated in a clockwise direction to the pipe-gripping position shown in Figure 3, jaw rollers 50, 52 ride along their respec-tive cam surfaces 71, 73 to urge the dies into gripping con-tact with the pipe. Because cam surface 71 is moving toward the pivot point P of its respective jaw 44, the camming effect of this cam surface would be somewhat less than that of its opposed cam surface if the two cam surfaces were identical.
However, as illustrated in Figures 2 and 3, cam surface 71 has a greater curvature than cam surface 73 so that jaw rollers 50, 52 ride along cams of equal effective pitch thereby enabling jaw 44 to approach the gripping position of Figure 3 at the same rate as jaw 46.
As shown in Figure 3, when moving from the neutral posi-tion to the engaged position, both jaw rollers 50, 52 move through an angle U, thereby causing the center of rotation of the rotary gear, M, to lie on the axis of the pipe, N.
`` i ~5737 The common practice in the art is to provide a single tong which may be used for a wide range of drill pipe and casing diameters. In order to achieve this flexibility, each tong is provided with a different pair of jaws for each size pipe to be gripped. Figure 6 illustrates the same power tong gripping assembly as shown in Figures 2 and 3 except that jaws 44, g6 have been replaced with substantially larger jaws 144, 146 having dies 136, 137, 138, 139 which are adapted to grip a smaller pipe 160. The rotary gear 30 is the same.
The jaws are made interchangeable by removal of the jaw re- -tention bolts at pivot points P and P'. According to the present invention, each pair of jaws, e.g. jaws 144, 146, are preferably constructed such that their dies will grip the pipe for which they are designed with the jaw rollers at approximately the same point on the cam surfaces. Thus, it can be seen that the improved cam surface configurations of the present invention provide the stated advantages for any size jaw used in the tong.
It will be appreciated that the positions of the jaw rollers on the cam surfaces when the pipe is gripped will vary where the pipe is either undersized or oversized. How-ever, within reasonable pipe diameter tolerances, the cam surfaces are long enough so that even undersized or oversized pipe will be qripped with the jaw rollers somewhere along the cam surfaces. Therefore, the gripping may occur with the jaw rollers at any point along some discrete length, fcr example, a length on the order of 2 to 3 inches. As used herein, the term "cam surface~ refers to that discrete length along which the gripping camming action may be expected to `~ o o ~ ll 25'737 .
take place. The adjacent regions on the interior of the rotary gear ~ay be curved or otherwise shaped to smoothly bring the cam follow~r(jaw rollers) to the cam surfaces, but the term cam surface~ refers only to that length along which gripping camming action occurs between the cam followers and the interior surface of the rotary gear. It is desired that the opposing jaws 44, 46 be displaced equally (i.e. moved through equal rotational angles about points P, P') whenever the jaw rollers are positioned anywhere along the cam sur-faces. It can be seen that for any chosen shape of a cam surface used on rotary gear 30, there is a unique configura-tion for its opposing cam surface that will assure that the opposing jaws move toward the pipe at the same rate. The foregoing statement applies to the usual situation where there is symmetry about line CL, i.e. where the jaw sizes and shapes are the same, the dies the same and the pivot points P, P' are located in mirror positions relative to line CL. Where there is not precise symmetry about line CL, there is, nevertheless, a unique configuration for the opposing cam surface that will give the advantages of the present invention. But the configuration will be different from the situation where there is symmetry.
It will be appreciated that the precise cam arrangements illustrated in Figures 2 and 3 are illustrative only. Other cam configurations may be devised. What is important is that the opposing cam surfaces be cooperatively shaped such that when tbe cam followers (jaw rollers) are at any two given points along the opposing cam surfaces, the opposed jaws will have moved to positions such that a pipe gripped therebetween ~5737 will be centered within the rotary gear. In the usual case where there is symmetry about line CL, the jaws will have moved through the same rotational angle about their respective points at any time the jaw rollers are on the cam surfaces.
While the present invention has been disclosed in con-nection with illustrative embodiments, numerous modifications may be made without departing from the spirit or scope of the invention.
....
73~7 ~ n object of a primary aspect of the present invention is the provision of a power tong having means for bringing the gripping e]ements into secure and uniform engagement with the pipe so that the pipe may be rotated evenly about its a~is to prevent dangerous vibrations.
An object of another aspect of th;s ;nvention is the provision of opposed cam surfaces presenting different curvatures in order to com-pensate for t-he different angles at which the cam followers attack their respective cam surfaces during make up and break out operations.
In accordance with one aspect of the present invention a novel open-mouth power tong is provided comprising a frame having a throat at its front; a power-driven rotary gear having a mouth adapted for alignment with the throat, the rotary gear being rotatably mounted on the frame; a pair of pivotally mounted jaws located on opposite sides of the center line of the tong and having their pivot points rearward of the center of rotation of the rotary gear; a cam follower associated with each jaw; pipe gripping elements carried by the jaws; and at least one pair of opposed cam surfaces on the interior surface of the rotary gear, the cam surfaces of the pai}
being cooperatively shaped such that when th-e cam followers are cammed at points along the opposed cam surfaces the jaws are positioned so that a ~0 pipe section gripped therebetween is centered within the rotary gear; at least one pair of opposed cam surfaces comprising a first cam surface de-fined by a portion of a first circ]e having its center on the line X which is perpendicular to the centeriine of the throat and passes through the center of the rotary gear, and a second cam surface defined by a portion of a second circle having a smaller radius than the first circle, with the center of the second circle located at the opposite side of the throat centerline and being offset from line X.
. 4 -i737 By a variant thereof, tlle pair of jaws are pivoted at points symmetrically located about the centerline of the tong and the jaws and their associated pipe gripping elements are substantially the same shape and size, and wherein the opposed cam surfaces are cooperatively shaped such that when the cam followers are cammed at points along the opposed cam surfaces the opposed jaws will have pivoted toward the pipe section through substantially the same angle.
By another variant, the power tong includes two pairs of opposed cam surfaces, a first pair for joint make up and a second pair of joint break out.
By another aspect of this invention, an improvement is provided in a power tong of the type having a frame with a pipe-receiving throat, a rotary gear mounted on the frame, means for rotatably driving the rotary gear, cam means on the inner surface of the rotary gear comprising two pairs of opposed cam surfaces, a pair of pivotally mounted jaws carrying dies for biting into the exterior of the pipe, and a cam follower associated with each jaw for riding on the cam surfaces and urging the dies into bit-ing engagement with a pipe section, improved cam means wherein each pair of opposed cam surfaces comprises first and second diametrically opposed 2~ cam surfaces, said first opposed cam surface being defined by a portion of a first circle having its center on the line X which is perpendicular to the centerline of the throat and passed through the center of the rotary gear, and the second opposed cam surface being defined by a portion of a second circle having a smaller radius than the first circle, with the cen-ter of the second circle located at the opposite side of the throat center-line and being offset from line X.
By another aspect of this invention a rotary gear is provided for use in a power tong of the type having opposed jaws pivotaliy mounted ~ t~
' ~
- for being brought into gripping engagement with a pipe s2ction by o?er;tion ~- 5 -57~'7 of cam followers adapted to ride on cam surfaces on the in~erior surface of a rotary gear, said rotary gear comprising: means for being rotatably driven about a central gear a~is by a suitable drive train; a central open-ing for housing a pipe section being gripped for rotation, said opening dcfining a rotary gear interior surface; an aperture for al-ignil-g w;th t:he [open-]mouth of the tong during p;pe loading and ullload~ g and at ltast one pair of diametrically opposed cam surfaces on the interior surrace of the rotary gear, the first opposed cam surface being defined by a portion of a first circle having its center on the line X which is perpendicular to the center].ine of the tllroat and passed through tihe center of the ro-: tary gear, and the second opposed cam surface being defined by a portion of a second circle having a sma].ler rad;us than the first circle, with the center of the second circle located at the opposite side of the throat centerline and being offset from li.ne X.
-In the accompanying drawings, a -.
r~737 DF~ I ~ r DFSC~ I r I I r~ OF THE DRAWINGS
Figure 1 is a perspective view of an open-mouth power tong constructed in accordance with the present invention.
Figure 2 is a plan view of the pipe-gripping assembly of the tong of the present invention, i.e., the jaws, jaw rollers, gripping dies, and interior surface of the rotary gear, with the jaw~ spread apart in a neutral position to receive a pipe.
Figure 3 is a view similar to Figure ~ showing the pipe securely held by the pipe-gripping assembly with the axis of the pipe at the center of the rotary gear.
Figure 4 is a view similar to Figure 2 showing a typical prior art pipe-gripping assembly.
Figure 5 is a view of the prior art assembly shown in Figure 4 with the pipe gripped off-center.
Figure 6 is a view of a pipe-gripping assembly of the present invention showing enlarged jaws used for gripping : pipe of relatively small diameter.
:
i` . , . ~.~ ~S';~;37 DETAILED DESCRIPTION OF q`HE PREFERRED EMBODIMENT
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ . _ _ , Referring to the drawings and in particular to Figure 1, there is shown in perspective an open-mouth power tong 10 conseructed in accordance with the present invention. Tong 10 includes a frame 12 comprising upper and lower surfaces con-nected by sidewalls. The upper and lower surfaces further include upper and lower cage plates 1~, 16 ~hich pivotally support the jaws as explained below. Frame 12 defines a frontal throat 18 for receiving the pipe sections. When a pipe section is centrally located within the frame during operation, throat 18 is closed off by means of pivotally mounted door members 20, 22 in the manner well known in the art.
The pipe-gripping assembly will now be described with reference to Figures 1-3. A rotary gear 30 is mounted within frame 12 for rotation relative to the frame. Rotary gear t 30 includes gear teeth (not shown3 on its outer periphery so that it may be driven in the manner well known in the ' art, for example, by means of a plurality of of pinion sears (not shown).Th~ pi~ion qear~,- in turn~ ~y be ~uitably dr~ en by an hydraulic drive train as shown, for example, in U.S.
patent no. 2,879,680. The inner surface of the rotary qear 30 includes cam means comprising curved cam surfaces 70, 71, 72, 73 for urging the pipe-gripping elements into contact t with the pipe~ In the illustrated embodiment, the pipe-yripping ele~ents comprise dies 36, 37, 38, 39 mounted on a pair of pivotally mounted ~aws 4~, 46. The jaws are urged toward the pipe by means of ca~ followers comprising jaw _7_ i , . . . .
;!
5~7;~'7 rollers 50, 52 which are rotatably mounted on the jaws by pins 56, 58. Rollers 50, 52 ride on the cam surfaces 70, 71, 72, 73 on the interior of the rotary gear 30.
It will be noted that the jaws are pivotally mounted a~ points P, P' toward the rear of the tong and that the rear dies 36, 38 are near the pivot points so that when a pipe section, for example, pipe section 59, is inserted in the tong, its rearward motion is stopped by dies 36, 38 as shown in Figure 2. The front dies 37, 39 are positioned forward of line X (Figure 2) which is the horizontal line that passes through the axis of rotary gear 30 and is perpendicular to the centerline, CL, of the throat. Thus, when the jaws are urged toward the pipe to the gripping position illustrated in Figure 3, the front dies 37, 39 tend to urge the pipe somewhat rearwardly so that the pipe is gripped both forward and behind line X on both sides of the tong. Stated differently, the dies preferably grip the pipe in each of the four quadrants de-fined by lines X and CL. The rear dies 36, 38 are only slightly displaced during the gripping operation due to their proximity to the jaw pivot points P, P'. However, during the camming operation the angular attitude of rear dies 36, 38 changes substantially so tht the dies contact the pipe at the correct biting angle.
As set forth above, the present invention relates pri-marily to improved means for bringing the dies into a grip-ping relation with the pipe in such a manner that the pipe is centered at the center of the rotary gear, thereby assur-ing relatively even and safe rotation of the pipe during make up and break out operations.
~F
f' , ., ~5737 The improvement of the present invention will be more readily understood after first analyzing a pipe grippin~ assem-bly of the prior art as illustrated in Figures 4 and 5.
According to the illustrated prior art practice, the cam sur-faces on the interior of the rotary gear 30' comprise opposed cam surface pairs 60, 62 and 61, 630 Cam surfaces 60 and 63 form portions of a circle having its center at point C on line X. Cam surfaces 61 and 62 form portions of a circle having its center at point C' on line X. The radii of the four cam arcs are equal; therefore, the curvature of the opposed pair of cams operating in any make up or break out operation will be equal. As discussed above, with the use of the symmetric pipe-gripping assembly illustrated in Figure 4, the jaws 44', 46' must be urged toward the pipe evenly in order for the pipe to be centered as it is gripped. Stated differently, when the pipe is gripped the jaws must have been rotated the same angular amount around their respective pivot points. However, as shown in Figure 5, when the pipe is gripped according to the illustrated prior art practice, the axis of the pipe is not at the center of the rotary gear. This occurs because the opposing jaw rollers 5~', 52' are urged toward the pipe at different rates due to the fact that the opposed cam surfaces, e.g., cam surfaces 60 and 62, are acting on their respective jaw rollers at different "angles of attackn. This phenomenon may be best understood by visualizing the movement of the opposed cam surfaces, e.g. cam surfaces 60 and 62, during a typical make up operation. As the operation begins, the jaw rollers 50', 52' are positioned within the neutral recesses on the opposite sides of the rotary gear. As the rotary gear _g_ ~ - `
~1~57~'7 begins to move, for example in a clockwise direction to the pipe-engaging position illustrated in Figure 5, ca~ surface 60 moves closer to the pivot point P of its respective jaw while cam surface 62 ~ove~ away from the pivot point P' of its jaw, thereby causing the rollers to act on different effec-tive cam pitches. Therefore, the jaw rollers 50', 52' are urged toward the pipe at different rates since the effective pitches of the cam surfaces are different. During a subsequent break out operation, the other pair of opposed cam surfaces, i.e. cam surfaces 61 and 63, will act in a similar manner such that the pipe will be gripped in an off-center manner.
The amount of angular motion of jaws 44', 46' is shown in Figure S where the initial positions of the centers of the jaw rollers 50', 52' are shown as cross marks. As illustrated, jaw 44' ~oves through an angle Y about its pivot point P while jaw 46' moves through an angle Z about its pivot point P'.
Since angle Y is somewhat greater than angle Z, pipe 59 is gripped in the slightly off-center position shown in Figure 5, where reference character M represents the center of rota-tion of the rotary gear 30 and N represents the axis of the pipe. As explained below, a primary object of the present in-vention is to assure that points M and N more nearly coincide.
According to the apparatus of present invention illus-trated in Figures 2 ancl 3, the opposing cam surface pairs, i.e. pairs 70, 72 and 71, 73, are not of equal curvature. As best shown in Figure 2, cam surfaces 70 and 73 define portions of circles having equal radii R2 with their centers at points A, A' on line X. Cam surfaces 71, 72 define portions of circles having equal radii R3 with their curvatures at points r~~-/
B, ~' which are offset from line X. In the illustrated embodiment, the radii R3 are slightly less than the radii R2.
In a particular embodiment of a rotary gear for use on a 7-5/8 inch tong, the nominal radius R4 of the rotary gear is 6-3/8 inches~ R2 is 5.2S inches and R3 i5 5.06 inches with points B, B' being offset from line X at a distance of approximately 0.40 inch.
The operation of the illustrated pipe-gripping assembly can be best appreciated with reference to Figures 2 and 3.
In Figure 2 the jaw rollers 50, 52 rest in the neutral re-cesses as the pipe is received by the tong and moved into contact with the back dies 36, 38. As the rotary gear is rotated in a clockwise direction to the pipe-gripping position shown in Figure 3, jaw rollers 50, 52 ride along their respec-tive cam surfaces 71, 73 to urge the dies into gripping con-tact with the pipe. Because cam surface 71 is moving toward the pivot point P of its respective jaw 44, the camming effect of this cam surface would be somewhat less than that of its opposed cam surface if the two cam surfaces were identical.
However, as illustrated in Figures 2 and 3, cam surface 71 has a greater curvature than cam surface 73 so that jaw rollers 50, 52 ride along cams of equal effective pitch thereby enabling jaw 44 to approach the gripping position of Figure 3 at the same rate as jaw 46.
As shown in Figure 3, when moving from the neutral posi-tion to the engaged position, both jaw rollers 50, 52 move through an angle U, thereby causing the center of rotation of the rotary gear, M, to lie on the axis of the pipe, N.
`` i ~5737 The common practice in the art is to provide a single tong which may be used for a wide range of drill pipe and casing diameters. In order to achieve this flexibility, each tong is provided with a different pair of jaws for each size pipe to be gripped. Figure 6 illustrates the same power tong gripping assembly as shown in Figures 2 and 3 except that jaws 44, g6 have been replaced with substantially larger jaws 144, 146 having dies 136, 137, 138, 139 which are adapted to grip a smaller pipe 160. The rotary gear 30 is the same.
The jaws are made interchangeable by removal of the jaw re- -tention bolts at pivot points P and P'. According to the present invention, each pair of jaws, e.g. jaws 144, 146, are preferably constructed such that their dies will grip the pipe for which they are designed with the jaw rollers at approximately the same point on the cam surfaces. Thus, it can be seen that the improved cam surface configurations of the present invention provide the stated advantages for any size jaw used in the tong.
It will be appreciated that the positions of the jaw rollers on the cam surfaces when the pipe is gripped will vary where the pipe is either undersized or oversized. How-ever, within reasonable pipe diameter tolerances, the cam surfaces are long enough so that even undersized or oversized pipe will be qripped with the jaw rollers somewhere along the cam surfaces. Therefore, the gripping may occur with the jaw rollers at any point along some discrete length, fcr example, a length on the order of 2 to 3 inches. As used herein, the term "cam surface~ refers to that discrete length along which the gripping camming action may be expected to `~ o o ~ ll 25'737 .
take place. The adjacent regions on the interior of the rotary gear ~ay be curved or otherwise shaped to smoothly bring the cam follow~r(jaw rollers) to the cam surfaces, but the term cam surface~ refers only to that length along which gripping camming action occurs between the cam followers and the interior surface of the rotary gear. It is desired that the opposing jaws 44, 46 be displaced equally (i.e. moved through equal rotational angles about points P, P') whenever the jaw rollers are positioned anywhere along the cam sur-faces. It can be seen that for any chosen shape of a cam surface used on rotary gear 30, there is a unique configura-tion for its opposing cam surface that will assure that the opposing jaws move toward the pipe at the same rate. The foregoing statement applies to the usual situation where there is symmetry about line CL, i.e. where the jaw sizes and shapes are the same, the dies the same and the pivot points P, P' are located in mirror positions relative to line CL. Where there is not precise symmetry about line CL, there is, nevertheless, a unique configuration for the opposing cam surface that will give the advantages of the present invention. But the configuration will be different from the situation where there is symmetry.
It will be appreciated that the precise cam arrangements illustrated in Figures 2 and 3 are illustrative only. Other cam configurations may be devised. What is important is that the opposing cam surfaces be cooperatively shaped such that when tbe cam followers (jaw rollers) are at any two given points along the opposing cam surfaces, the opposed jaws will have moved to positions such that a pipe gripped therebetween ~5737 will be centered within the rotary gear. In the usual case where there is symmetry about line CL, the jaws will have moved through the same rotational angle about their respective points at any time the jaw rollers are on the cam surfaces.
While the present invention has been disclosed in con-nection with illustrative embodiments, numerous modifications may be made without departing from the spirit or scope of the invention.
....
Claims (5)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. An open-mouth power tong comprising:
a frame having a throat at its front;
a power-driven rotary gear having a mouth adapted for alignment with the throat, said rotary gear being rotatably mounted on the frame;
a pair of pivotally mounted jaws located on opposite sides of the center line of the tong and having their pivot points rear-ward of the center of rotation of the rotary gear;
a cam follower associated with each jaw;
pipe gripping elements carried by the jaws;
and at least one pair of opposed cam surfaces on the interior surface of the rotary gear, the cam surfaces of the pair being co-operatively shaped such that when the cam followers are cammed at points along the opposed cam surfaces the jaws are posi-tioned so that a pipe section gripped therebetween is centered within the rotary gear;
said at least one pair of opposed cam surfaces comprising a first cam surface defined by a portion of a first circle having its center on the line X which is perpendicular to the centerline of the throat and passed through the center of the rotary gear, and a second cam surface defined by a portion of a second circle having a smaller radius than the first circle, with the center of the second circle located at the opposite side of the throat centerline and being offset from line X.
a frame having a throat at its front;
a power-driven rotary gear having a mouth adapted for alignment with the throat, said rotary gear being rotatably mounted on the frame;
a pair of pivotally mounted jaws located on opposite sides of the center line of the tong and having their pivot points rear-ward of the center of rotation of the rotary gear;
a cam follower associated with each jaw;
pipe gripping elements carried by the jaws;
and at least one pair of opposed cam surfaces on the interior surface of the rotary gear, the cam surfaces of the pair being co-operatively shaped such that when the cam followers are cammed at points along the opposed cam surfaces the jaws are posi-tioned so that a pipe section gripped therebetween is centered within the rotary gear;
said at least one pair of opposed cam surfaces comprising a first cam surface defined by a portion of a first circle having its center on the line X which is perpendicular to the centerline of the throat and passed through the center of the rotary gear, and a second cam surface defined by a portion of a second circle having a smaller radius than the first circle, with the center of the second circle located at the opposite side of the throat centerline and being offset from line X.
2. A power tong as claimed in claim 1 wherein said pair of jaws are pivoted at points symmetrically located about the centerline of the tong and the jaws and their associated pipe gripping elements are substantially the same shape and size, and wherein the opposed cam surfaces are cooperative-ly shaped such that when the cam followers are cammed at points along the opposed cam surfaces the opposed jaws will have pivoted toward the pipe sec-tion through substantially the same angle.
3. A power tong as claimed in claim 1 including two pairs of opposed cam surfaces, a first pair for joint make up and a second pair for joint break out.
4. In a power tong of the type having a frame with a pipe-re-ceiving throat, a rotary gear mounted on the frame, means for rotatably driv-ing the rotary gear, cam means on the inner surface of said rotary gear com-prising two pairs of opposed cam surfaces, a pair of pivotally mounted jaws carrying dies for biting into the exterior of the pipe, and a cam follower associated with each jaw for riding on said cam surfaces and urging the dies into biting engagement with a pipe section, improved cam means wherein each pair of opposed cam surfaces comprises first and second diametrically opposed cam surfaces, said first opposed cam surface being defined by a portion of a first circle having its center on the line X which is perpendicular to the centerline of the throat and passed through the center of the rotary gear, and said second opposed cam surface being defined by a portion of a second circle having a smaller radius than the first circle, with the center of the second circle located at the opposite side of the throat centerline and being offset from line X.
5. A rotary gear for use in a power tong of the type having opposed jaws pivotally mounted for being brought into gripping engagement with a pipe section by operation of cam followers adapted to ride on cam surfaces on the interior surface of a rotary gear, said rotary gear com-prising:
means for being rotatably driven about a central gear axis by a a suitable drive train;
a central opening for housing a pipe section being gripped for rotation, said opening defining a rotary gear interior sur-face;
an aperture for aligning with the [open-]mouth of the tong during pipe loading and unloading;
and at least one pair of diametrically opposed cam surfaces on the interior surface of the rotary gear, said first opposed cam surface being defined by a portion of a first circle having its center on the line X which is per-pendicular to the centerline of the throat and passed through the center of the rotary gear, and said second opposed cam surface being defined by a portion of a second circle having a smaller radius than the first circle, with the center of the second circle located at the opposite side of the throat centerline and being offset from line X.
means for being rotatably driven about a central gear axis by a a suitable drive train;
a central opening for housing a pipe section being gripped for rotation, said opening defining a rotary gear interior sur-face;
an aperture for aligning with the [open-]mouth of the tong during pipe loading and unloading;
and at least one pair of diametrically opposed cam surfaces on the interior surface of the rotary gear, said first opposed cam surface being defined by a portion of a first circle having its center on the line X which is per-pendicular to the centerline of the throat and passed through the center of the rotary gear, and said second opposed cam surface being defined by a portion of a second circle having a smaller radius than the first circle, with the center of the second circle located at the opposite side of the throat centerline and being offset from line X.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US690579A | 1979-01-26 | 1979-01-26 | |
| US006,905 | 1979-01-26 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1125737A true CA1125737A (en) | 1982-06-15 |
Family
ID=21723196
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA344,326A Expired CA1125737A (en) | 1979-01-26 | 1980-01-24 | Power tong |
Country Status (2)
| Country | Link |
|---|---|
| JP (1) | JPS5839629B2 (en) |
| CA (1) | CA1125737A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5144868A (en) * | 1990-05-08 | 1992-09-08 | Feigel Kurt R Jr | Power tongs |
-
1979
- 1979-10-30 JP JP13940379A patent/JPS5839629B2/en not_active Expired
-
1980
- 1980-01-24 CA CA344,326A patent/CA1125737A/en not_active Expired
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5144868A (en) * | 1990-05-08 | 1992-09-08 | Feigel Kurt R Jr | Power tongs |
Also Published As
| Publication number | Publication date |
|---|---|
| JPS55101378A (en) | 1980-08-02 |
| JPS5839629B2 (en) | 1983-08-31 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| US4084453A (en) | Power tongs | |
| US4445402A (en) | Power tong and back-up tong assembly | |
| US4350062A (en) | Power tong | |
| US4404876A (en) | Power tongs | |
| DE69115391T2 (en) | Device for applying a torque to a tubular element | |
| CA2366116C (en) | Tong | |
| EP0960255B1 (en) | Jaw unit for use in a power tong | |
| US4437363A (en) | Dual camming action jaw assembly and power tong | |
| EP0374533A1 (en) | Active jaw for a power tong | |
| EP1899573B1 (en) | Power tong device | |
| CA1126720A (en) | Power tong | |
| US4632618A (en) | Feed storage for drill rods for a long-hole drilling apparatus | |
| CA2004015C (en) | Assembly for use in a tong, a belt holder and a belt anchor assembly provided with such a belt holder | |
| US4089240A (en) | Power tongs | |
| US6065372A (en) | Power wrench for drill pipe | |
| CA1125737A (en) | Power tong | |
| JPH10128457A (en) | Device for deforming bar shaped member | |
| US4326435A (en) | Hydraulic power tong | |
| CN215701362U (en) | Groove steel pipe connection insertion tool | |
| NO157873B (en) | ROER TANG. | |
| FI81885B (en) | GRIPSAXANORDNING FOER GRIPNING OCH ROTERING. SIIRRETTY ALKUPAEIVAE-FOERSKJUTET DATUM PL 14 ç 19.10.87. | |
| EP0040231B1 (en) | Pipe wrench | |
| CA1088918A (en) | Power tong drive mechanism | |
| JPH0673973A (en) | Device for mounting joint having thread groove for assembling pipe | |
| SU1266969A1 (en) | Arrangement for deflecting the jet from gushing well |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |