CA1327825C - Track-supported cage plates for power tongs - Google Patents

Abstract

A power tong is provided with a support for the cage plate assembly which is comprised of a rail and track combination. Preferably the rail is a circular ring formed on the outside of the tong body and the track is a groove formed on the inside surfaces of the cage plates. The preferred material for the rail is a high-impact, abrasion resistant, low-friction elastoplastic polymeric material, more preferably, polyurethane.

Description

Title 132782~
Track-Supported Cage Plates for Power Tongs Fleld of the Invention This invention relates to power tongs used to ma~e up 05 or ~reak threaded sections of pipe or casirlg used in the oil drilling art. More particularly this invention relates to an improved ~eans for supporting and centralizing the cage plate assembly within a power tong.
Back~round to the Invention Power tongs are used in the oil well drilling industry to rotate drilling pipe or tubing or casingJ hereinafter referred to collectively as "pipe". Power tongs operate by clamping pipe between jaws that are then rotated by means of force applied through a split or "C"-shaped rotary gear. The jaws that grasp the pipe are free to pivot on jaw pins that are fixed at their outside ends in cage plates. The cage plates absorb some ofthe spreading force of the jaws that occurs when the pipe is clamped. Both the upper and lower cage plates are of'a general "C" shapéd configuration, and together with the jaws and their respective jaw pins may be said to comprise a "cage plate assembly".
The cage plate assembly may optionally be supported either on the rotary gear, which is supported, in turn, by the tong body, or may be supported directly on the body of the tong. In both cases, the cage plate assembly will ~: :~- ; :

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- 2 -rotate with the jaws when pipe is being threaded together or threaded apart.
If mounted on the tong body~ the cage plate assembly must be slidingly supported by the tong bocly throughout 05 continuous rot~tion with respect to the tong hody. If mounted on the rotary gear, the cage plate assembly will rotate with the rotary gear (rather than in respect to the rotary gear), once the pipe has been engaged. But if the cage plate assembly is supported on the rotary gear, it nevertheless rotates slightly with respect to the rotary gear when the jaws are being engaged. In either case, the support means for the cage plate must both accommodate a rotary motion and also be contained vertically and horizontally within the body of the tong and/or rotary gearJ while being rotated.
Cage plate assemblies have been supported in the past against radial displacement within power tongs by rollers called herein "cage-bearings". These cage-bearings have been mounted on vertical shafts attached either to the tong body or to the cage plates. In one example of the priur art exemplified by U.S. Patent No. 4,~66~450 to Farr et al the cage bearings run in a horizontal race formed in the interior side surfaces of the cage plates. Such races have therefore been formed on the underside surface of the upper cage plate~
and the upper side surface of the lower cage plate. Cage-bearing rollers have been correspondingly mounted on -the upper and lower surfaces of the tong hody or rotary ~ear~ depending ".~

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_ 3 _ ~327823 upon which part the cage plate asse~bly is being carried.
~ hile the cage~bearings constrain the cage plate assemhly against radial displacement, this assembly is also required to be constrained against vertical displacement.
05 This has been accomplished in the past either by a ~etal-to~
metal contact between the inner surfaces of the cage plates and the upper and lower surfaces of the tong body or rotary gear; or by means of support bearings mounted on horizontal a~iis, as depicted in United States Patent No. 4,266J450.
Examples of other prior art references showing means for supporting a cage plate assembly include:
U.S. Patent 4,060,014 to Turner Jr.
U.S. Patent 3,550,485 to Dic~mann U.S. Patent 4~485,695 to Heilhecker U.S. Patent 4J334,444 to Carstensen The patent to Turner shows a cage plate that i5 supported on a rotary gear through arcuate brake shoes. Such shoes are inherently highly frictional.
Dickmann shows a cage plate assembly carried hy rollers that incorporates seal rings (46). Such seal rings are not indicated, however, as having any support function.
Heilhec~er proposes to use a sold ring of phenolic ~aterial to support the rotary gear. However, as this patent is directed to a spinner , it is not intended -to develop and apply a high torque to pipe. Accordingly, the housing : , : :: :, :: ~ , ;: : :: .

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assembly for the jaws is said to rotate on a solid brass ring which, like phenolic, is no-t a low-friction material. These materials are not intended to be so~ in this reference. This is shown by the alternate suggestion that asbestos may be 05 substituted fo~ the phenolic. Further~ these materials do not have a high abrasion resistance.
The patent to Carstensen discloses head plates -that are supported on circumferential bearing pads. No reference is made as to the material proposed as suitable for such pads.
The rotary gear in this reference is supported vertically by aluminum-bronze bearing bloc~s. However, the rotary gear is also located horizontally by a series of roller bearings.
Accordingly, the referenced bearing blocks were not considered suitable for carrying horizontal loads. ~-It may be desirable to have an efficient low-friction means for supporting the cage plate assembly that permits the easy rotation of the assembly under high vertical loads for the following possible reason. The weigh* of a power tong as it is being brought up to a pipe is supported on a "hanger".
Usually the hanger has a spring portion tha-t allows the tong to be moved slightly up or down. Once the tong is clamped to the pipe the hanger should ideally continue to carry the full weight of the tong. But as the pipe is being threaded the jaws are displaced either upwards or downwards by the travel af the threads. This tends to cant the tong slightly. The .- : : : :, .-:, . . :: .

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canting force so created must be transferred from the jaws, which are rotating, to the tong body through -the cage plate assembly and therefore through the vertical support means between the assembly and the tong body, or rotary gear, within 05 which it is turning.
The support system for cage plates may also be subject to high transverse or lateral forces. While piye is being torqued the tong bDdy is restrained frorn rotating about the pipe by a drag line. The force developed in the drag line can reach many thousands of pounds. It is thought that a corresponding and balancing force is developed at the pipe and transmitted to the -tong body through the jaws and cage plate assembly. The support system for the cage plate assemblies would therefore also absorb this force.
The use of the older metal-to-metal and friction-developing supports is inefficient as it absorbs torque under load. Thls was recognized in U.S. Patent 4,266,450. It is therefore desirable to both support a cage plate under high loads, and to minimize the friction developed when the cage plate assembly is being rotated under the stress of a high lateral and canting forces.
Both the ca~e-bearings and support rollers as utilized todate have been subject to high rates of wear. Wear has been found to occur both in the bearings for such rollers and in the races within which they run. An alternate means ~ :, : :, .
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for supporting the cage plate assembly which would be more durable while providing law-friction support would therefore ~ -be highly desirable.
Summary of the Invention 05 According to the invention in its broadest sense, a cage plate assembly for a power tong is supported and constrained against radial and vertical displacement within a tong by a support system utilizing a track and circular rail combination wherein the rail is composed of a high density, high impact and abrasion resistant, low-friction elastoplastic polymeric material. The track is formed by a groove within either the inside surface of the cage plate or withln the outside surface of the tong body or rotary gear element upon which the cage plate assembly is supported,, and the r~il is attached to the complimentary surface on the cage plate, tong body or rotary gear so as to interfit with the trac~.
In a preferred c~nfiguration for the invention the cage plate assembly is provided with tracks on the inside surfaces of the upper and lower cage plates and upper and lower rails are constituted by rings of complimentary dimensions to the trac~, which rings are fastened respectively to the upper and lower surfaces of the tong body.
By a further feature of the invention the material of the ring is preferentially composed of urethane rubber on its ~riction bearing surfaces.

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_ 7 _ 1327 By a further feature of the invention said rail is composed of a ridged metal core~ clad over its friction-~-l bearing surfaces with a high i~pact and abrasion resistant,

3 low friction elastoplastic polymeric material.
~ 05 These and further features of the invention will be :! apparent from the description of the preferred embodiment which now follows.
Summary of _e Drawinas Figure 1 is an exploded view of tong parts incorporating a cage plate assembly that is supported on the -tong bady, in accordance with the invention;
Figure 2 is a broken cross-sec-tion of the parts of Figure 1, once assembled;
Figure 3 is an exploded view of tong parts ~ 15 incorporating a cage plate assembly that is supported on the '; rotary gear, in accordance with the invention;
Figure ~ is a cross-section of the parts of Figure 3, once assembled.
Figure 5 is a cross-section of an alternate grooved rail~ in accordance with the inventor.

In Figure 1 portions of a power tong are depicted in exploded views. The tong body 1 is composed of sheet s-teel that has been shaped and drilled. A rotary gear 2 which fits within the tong body 1 is provided with the usual camming surfaces 3 which cause the tong jaws ~not shown) to close and clamp onto pipe. The outer circumference of the rotary gear 2 has gear teeth 4 through ~hich torque is transmitted to force the rotary gear 2 to turn.

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The upper plate 5 of the -tong body 1 is, as well, cut from sheet metal wi-th a circular opening 6 in the center through which piye will pass around the edge of the opening 5.
Mounted on the upper surface of the upper plate 5 is a 05 rail element 7 in the form of a ring~ in accordanc.e with the invention. This rail is bolted to the upper tong plate 5 through countersunk holes 8.
Above the upper tong plate 5 is depicted the top cage plate 9 of the cage plate assembly. For sim~lification of the drawings the entire assemble is not shown. However, the pivot pins 10 in the form of bolts which hold the jaws, as welL as a sample spacer bolt 11 and sleeve 12 which hold the upper and lower cage plates together, is shown.
Formed on the underside of the top cage plate 9 is the track 13 in the form of a groove within which the rail 7 interfits, once the parts are assembledA
The track 13 and rail 7 are depicted as rectangular in cross-section, and this is the preferred shape. However, they may have other cross-sectional shapes so long as such shapes interfit and the cage plates are adequately supported. The interfit need not be close. It is sufficient if there is a close fit between at least cne surface that provides vertical support, and one surface that provides horizontal support.
Where there is a close fit around all of the inside surfaces of the track, allcwing for thermal e~pansion and distortional effects, the weight loads will be distributed over , - : : ~ :.:,.............. - :
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9 ~32782~
larger surfaces, producing a reduced rate of wear.
Figure 2 shows an enlarged cross sectional view of details of the track~rail support system of the invention.
The outer wall 14 of the tong body 1 encases the rotary gear 2 05 whose support means is not shown in this figure. The top and bottom cage plates 9, 9a respectively, overlie and underlie the tong body 1. The rail 7 is bolted to the tong body 1 by bolts 16 that are set in cDuntersunk holes ~ in the rail 7.
Two forms of rails 7,7a are shown in Figure 2. The first track 7 is a solid track made of high impact and abrasion resistant, low friction elastoplastic poly~eric material. The preferred material is urethane rubber such as that sold by Uniroyal Chemical under the trade mark ADIPRENG, : but other acceptable materials are polyu~ethan polymers haYing a duro hardness of 75-85, nylon, and the material sole under the trade name HYTRAL. The second rail 7a is of composi-te structure, having an inner metal ring 17 and an outer polymeric sheath 18.
The purpose of providing a composite rail 7a is to ~0 increase both the strength of the rail 7a and its ability to conduc-t heat away from the frictional surfaces. Accordingly, the metal ring 17 may be made of any material, such as aluminum or bronze, that meet these cri-teria. Steel is, however, likely to be the preferred material.
The foregoing description has depicted a case where the cage plate.~ 9,9a are supported on the tong body 1. The alternati~e where the cage plates 9,9a are supported on the , i, !." :.. ..
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1 o --,f rotary gear 2 is shown in Figures 3 and 4.
In Figure 3 the rail 15 is fas-tened to the top cage plate 9 on its underside. The ring gear 2, which underlies the top plate 5 of the tong body l, ls provided with top and 05 bottom tracks. 19, 19a in the form of grooves. Th~se tracks l9,19a are of a shape and size which will receive the under ~i rail 15. Again this rail 15 is composed of material as ,~
described above. and fastened to the cage platf~ 9 is a similar, or equivalent manner.
The cage plate 9 overlaps the top tong plate 5 in this arrange~ent along its outer edge 20 and a notch 21 is provided so that the cage plate 9 may nest within the upper tong plate f 5. The rail 15 then protrudes, on assembly, into the track 19. As previously, this arrangement is symmetrically reflected on the underside of the tong, as well.
Figure 4 shows a sectional view of the componen-ts of Figure 3, when assembled. In this case the rotary gear 2 is shown as provided with a rotary roller assembly 21 with upper and lower roller bearings 22,22a. These rollers carry the ro-tary gear on the shoulders 23 of the teeth 2~ of the rotary gear 2 and on the outer circumferential bearing surfaces 25,25a.
The upper and lower rails 7,7a may be in either of the alternate forms as described with respect to Figure 2.
However, as the cage plate assembly in Figure 4 will turn only . . . .

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marginally with respect to the rotary gear 2. while the jaws are engaging, and not at all thereafter, heating considerations are not a problem in this configuration.
Figure 5 shows an alternate embodimen-t for the rail 05 which is comprised in the invention. In this embodiment the rail, which is seen in cross-section along the right side of the ring 23, through a bolt hole 8, has a series of grooves 24 formed in its outside surfaces. Such grooves ~4 occupy up to approximately 40-50% of the outer surfaces of the ring 23.
Their purpose i5 to retain grease ~not shown~ while at the same time provide sufficient supporting surfaces to carry the cage plate assembly.
The cross-sectional shape of the grooves 24 is optional: they may be rectangular or semi-circular. They need not even by precisely concentric~ although this is convenient for purposes of manufacture. They may either be ~achined into the material of the ring 23 or cast therein during original molding.
The inclusion of such grooves is also believed to significantly contribute to life of the bearing rings by providing a depository for bits of dirt that would otherwise abrade the bearing surfaces.
The foregoing has constituted a descrip-tion of preferred embodiments of the invention which are intended to ~5 be exemplary. The invention in its broadest and more particular aspects is further described and defined in the claims which now follow.

Claims (8)

WE CLAIM:

1. In a power tong having a main body, a rotary gear mounted within said body and a cage plate assembly with upper and lower cage plate portions, which assembly is supported on either said tong body or rotary gear, the improvement comprising a circular inter-fitting track and rail combination wherein one of said track or rail elements is disposed on the outer upper and lower surfaces of said tong body or rotary gear, and the complementary element to said track or rail element is disposed on the inner surfaces of said cage plate assembly so as to constrain said cage plate assembly against radial or vertical displacement while permitting circular rotation.

2. A power tong as in Claim 1 wherein said rail is composed of high-impact, abrasion resistant, low-friction elastoplastic polymeric material.

3. A power tong as in Claim 2 wherein said rail is composed of polyurethane.

4. A power tong as in Claim 3 wherein said rail has a Shore hardness of 75-85.

5. A power tong as in Claim 1 wherein said cage plate assembly is provided with upper and lower tracks, disposed on the inner surfaces respectively of said upper and lower cage plates, and said tong body is provided with said rails on the upper and lower outer surfaces of the tong body.

6. A power tong as in Claim 1 wherein said cage plate assembly is provided with upper and lower rails, disposed on the inner surfaces respectively of said upper and lower cage plates, and said rotary gear is provided with said tracks on the upper and lower outer surfaces of the rotary year.

7. A power tong as in Claim 1 wherein said rail is provided with grooves formed within the outer surface of said rail, which grooves are adapted to retain grease and abrasive particles during operation of the power tong.

8. A power tong as in Claim 1 wherein said rail is comprised of a rigid metal core clad over its friction bearing surfaces with a high-impact and abrasion resistant, low-friction elastoplastic polymeric material.