United States Patent [19]
`Iwasaki et al. (cid:9)
`
`[11] Patent Number: (cid:9)
`[45] Date of Patent: (cid:9)
`
`4,822,201
`Apr. 18, 1989
`
`[54] COUPLING PIN FOR SUCKER ROD MADE
`OF FIBER-REINFORCED PLASTIC
`MATERIAL
`[75] Inventors: Toshio Iwasaki; Akihiko Katoh;
`Atsuhiko Murao; Mosaics= Tsukada;
`Takashi Nakano; Masora Nasu, all of
`Tokyo, Japan
`[73] Assignee: Nippon Kokan Kabushiki Kaisha,
`Tokyo, Japan
`[21] Appl. No.: 62,765
`Jun. 15, 1987
`[22] Filed: (cid:9)
`Foreign Application Priority Data
`[30] (cid:9)
`Jul. 4, 1986 [JP] (cid:9)
` 61-156215
`Japan (cid:9)
` F16B 11/00
`[51] Int. O. (cid:9)
` 403/268; 403/334
`[52] U.S. Cl. (cid:9)
` 403/266, 267, 268, 334
`[58] Field of Search (cid:9)
`References Cited
`[56] (cid:9)
`U.S. PATENT DOCUMENTS
`4,475,839 10/1984 Strandberg (cid:9)
`
` 403/268 X
`
` 403/268
` 403/266
`
`4,653,953 3/1987 Anderson et al. (cid:9)
`4,662,774 5/1987 Morrow, Jr. (cid:9)
`Primary Examiner—Andrew V. Kundrat
`Attorney, Agent, or Firm—Frishaut Holtz, Goodman &
`Woodward
`ABSTRACT
`[57] (cid:9)
`A sucker rod coupling pM comprises a hole into which
`the sucker rod is to be inserted, and has a plurality of
`annular depressions which surround the inner wall of
`the hole. As viewed crosswise, the annular depressions
`respectively have tapered surface portions arranged in
`series from the open end to the closed end of the cou-
`pling pin hole. The tapered surface portions whose
`cross sections progressively increase toward the closed
`end of the coupling pin hole have their respective
`lengths progressively shortened in relation to the pre-
`ceding tapered portion, toward the closed end of the
`coupling pin hole, and the angle of inclination of the
`respective tapered surface portions progressively in-
`creases toward the closed end of the coupling pin hole.
`
`14 Claims, 4 Drawing Sheets
`
`11
`
`12
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`28 (cid:9)
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`26
`a 2 30 a t
`a 3 (cid:9)
`-.71/114 LOMFAIRWPAtur
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`21 20 19 18 (cid:9)
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`17 16
`
`14 (cid:9)
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`10
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`L.Q3
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`124 (cid:9)
`
`(cid:9) FQ2 J L (cid:9)
`.124 (cid:9)
`124
`
`.Q1
`
`15
`.Q0
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`Petitioners' Exhibit 1007
`John Crane v. Finalrod
`IPR2016-01786
`Page 1 of 8
`
`(cid:9)
`

`
`U.S. Patent
`
`Apr. 18, 1989 (cid:9)
`
`Sheet 1 of 4 (cid:9)
`
`4,822,201
`
`O
`
`cr
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`(0 N
`
`CO
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`Page 2 of 8
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`

`
`U.S. Patent
`
`Apr. 18, 1989
`
`Sheet 2 of 4 (cid:9)
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`4,822,201
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`L= 28. 6MM ,
`
`d= 25.4MM
`
`1.0
`
`44161111141e*Ve.%,
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`
`10 (cid:9)
`
`20
`
`X (mm )
`
`F I G. 2 A
`
`F
`
`X
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`F I G. 2 B
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`Page 3 of 8
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`

`
`U.S. Patent
`
`Apr. 18, 1989 (cid:9)
`
`Sheet 3 of 4 (cid:9)
`
`4,822,201
`
`20
`
`15
`
`0
`I
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`PRESENT
`INVENTION
`
`PRIOR ART
`
`5
`
`10
`
`15
`
`DISPLACEMENT (MM)
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`F I G. 3
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`Page 4 of 8
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`

`
`U.S. Patent
`
`Apr. 18, 1989 (cid:9)
`
`Sheet 4 of 4 (cid:9)
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`4,822,201
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`LL
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`Page 5 of 8
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`

`
`1
`
`4,822,201
`
`COUPLING PIN FOR SUCKER ROD MADE OF
`FIBER-REINFORCED PLASTIC MATERIAL
`
`2
`and rod 10 varies more noticeably in the axial direction.
`When, therefore, sucker rod 10 is drawn out of elon-
`gated hole 4, a strong frictional force is generated at the
`second taper section as counted back from the open end
`of elongated hole 4, frequently causing sucker rod 10 to
`break at said second taper section.
`The present invention has been developed in view of
`the above-mentioned circumstances, and is intended to
`provide a sucker rod coupling pin the design of which
`resolves the aforementioned difficulties.
`
`SUMMARY OF THE INVENTION
`To attain the above-mentioned object, this invention
`provides a sucker rod coupling pin, wherein a plurality
`of annular tapered depressions are formed around the
`inner wall of an elongated blind hole into which a
`sucker rod is to be inserted, and the angle of inclination
`of the respective annular depressions grows progres-
`sively greater toward the closed end of the elongated
`blind hole, while, at the same time, the length of these
`depressions becomes successively shorter.
`Thus, a sucker rod coupling pin embodying the pres-
`ent invention offers the advantages in that a uniform
`frictional pressure is generated between the coupling
`pin and the sucker rod provided with a hardened resin
`layer, and a uniform axially directed stress can be ap-
`plied to the sucker rod and resin layer.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`FIG. 1 is a longitudinal sectional view of a coupling
`pin embodying the present invention, into which a
`sucker rod is inserted;
`FIG. 2A indicates lengthwise and crosswise acting
`stresses applied to an annular depression which sur-
`rounds the inner wall of a coupling pin-receiving hole
`of the sucker rod, and whose cross section is tapered;
`FIG. 2B shows the various points at which the mag-
`nitudes of the stresses given in FIG. 2A were deter-
`mined;
`FIG. 3 diagramatically indicates the results of a ten-
`sile test, namely, the displacement and load is compared
`with the results obtained with respect to the prior art
`sucker rod coupling pin; and
`FIG. 4 illustrates the conventional metal coupling pin
`into which a sucker rod is inserted.
`
`DESCRIPTION OF THE EMBODIMENT
`A sucker rod coupling pin prepared from fiber-rein-
`forced plastics material will now be described, with
`reference to FIG. 1. The inner wall of hole 14 of cou-
`pling pin 12 embodying the present invention, into
`which sucker rod 10 is to be inserted, comprises a plu-
`rality of annular depressions 26, 28, 30. Outermost annu-
`lar inner wall portion 15 of hole 14 has a flat cross sec-
`tion. The first tapered cross section section surface
`portion 16 of the first annular depression 26 adjacent
`surface portion 15 progressively increases in diameter
`toward the closed end of hole 14. The second tapered
`cross section surface portion 17 of the first annular
`depression 26, on the other hand, progressively de-
`creases in diameter toward the closed end of hole 14.
`The smallest diameter of the tapered cross section of
`annular depression 26 is the same as the diameter of
`outermost annular surface portion. Tapered surfaces 18,
`19, 20, 21 defining the second and third annular depres-
`sions 28, 30, in the inner wall of hole 14 are arranged in
`the same order as mentioned above, in such a manner
`
`5
`
`10
`
`15
`
`20
`
`BACKGROUND OF THE INVENTION (cid:9)
`This invention relates to a sucker rod coupling pin
`prepared from fiber-reinforced plastics material.
`Until now, any device used in the drilling of an oil
`well has been fabricated exclusively from steel. This
`practice is accompanied with the drawback that steel is
`a heavy material and is, moreover, very susceptible to
`corrosion. In recent times, the quality of fiber-rein-
`forced plastics material has greatly improved. This
`material is lightweight and is highly corrosion-proof,
`and thus has come to be more widely used for manufac-
`turing parts of oil well-drilling equipment.
`When a deep oil well is drilled, the parts are used in
`the form of a number of connected units. A coupling
`type sucker rod is usually fabricated by fitting a metal
`pin to the rod end. The pins are joined together by a
`threaded coupling.
`However, the threaded coupling has, in the past,
`presented difficulties with regard to mechanical
`strength when used to effect the connection of metal
`pins to the sucker rod. Consequently, various devices 25
`have been proposed to resolve these difficulties. One of
`the proposed processes, which consists of threading the
`outer wall of the rod itself, tends to cut up reinforcing
`fiber, resulting in an unacceptable decline in the me-
`chanical strength of the coupling. At present, therefore, 30
`a friction type coupling dispensing with threading is
`being developed.
`In this connection, metal coupling pin 1 will now be
`described with reference to FIG. 4. This coupling pin 1
`comprises a coupling member 2 which is provided with 35
`elongated hole 4 into which sucker rod 10 is inserted.
`Threaded section 3 is formed on the peripheral portion
`of coupling. member 2 at the closed end of coupling
`member 2 to be engaged with external coupling means
`(not shown). Until now, a metal coupling member 2 has 40
`been employed. Three annular grooves are so formed as
`to surround the inner wall of coupling member 2. As
`viewed crosswise, the three annular grooves each have
`two tapered surface portions. Tapered surface portions
`7, lying nearer to the closed end of hole 4, have a 45
`sharply rising plane, toward the open end of hold 4.
`Tapered surface portions 6, positioned remote from the
`closed end of hole 4, have a plane inclining gradually
`downward toward the open end of hole 4. Upward and
`downward inclining surfaces 7 and 6 are alternately 50
`arranged three times. Annular surface portion 5, sur-
`rounding the inner periphery of the open end of hole 4,
`has a long flat plane and is spaced from the outer surface
`of rod 10.
`Resin 30 is placed in elongated hole 4, and rod 10 is 55
`forced thereinto. The resin is then allowed to harden,
`tightly gripping rod 10. A rod-pulling force is transmit-
`ted by means of the above-mentioned tapered depres-
`sions defined by surfaces 6, 7, with the aid of friction
`between the resin and the surfaces 6, 7. (cid:9)
`The outer diameter of coupling member 2 progres-
`sively decreases toward the open end of elongated hole
`4, thereby preventing an excessive force from being
`applied to sucker rod 10 if it happens to become
`warped. However, the proposed coupling pin 1 of FIG. 65
`4 has the drawbacks in that since the length 1 of the
`tapered surfaces 6 and taper angle a thereof have the
`same value, contact pressure between coupling pin 1
`
`60
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`Page 6 of 8
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`

`
`3
`that the tapered cross sections of these depressions 28,
`30 are patterned like those of the aforementioned first
`annular depressions 26. Annular innermost surface por-
`tion 22 adjacent to tapered surface 21, having a flat
`cross section, has the same inner diameter as the afore- 5
`said annular outermost surface portion 15. The junction
`between the tapered surfaces 17, 18, and also the junc-
`tion between the tapered surfaces 19, 20, are chamfered
`to prevent the junctions from presenting a sharp edge.
`As seen in FIG. 1, tapered surfaces 16, 18, 20 face the 10
`closed end of hole 4, and tapered surfaces 17, 19, 21 face
`the open end of hole 4.
`The outer diameter of a coupling pin 12 according to
`the present invention, progressively decreases from first
`annular depression 26, whose cross section is tapered 15
`toward outermost annular surface portion 15, and cou-
`pling pin 12 has a cylindrical section at the open end. In
`this case, length Hof surface portion 16, length 12 of
`surface portion 18, and length 13 of surface portion 20
`have a relationship 11 >12 >13. Angle al of surface 20
`portion 16, angle a2 of surface portion 18, and angle a3
`of surface portion 20 have a relationship al <a2 <a3.
`As in the conventional sucker rod coupling pin, resin 30
`is placed in coupling hole 4, and the stress exerted by
`the inserted sucker rod is sustained by the hardening of 25
`the surrounding resin.
`The breaking of a fiber-reinforced plastics (abbrevi-
`ated as "FRP") sucker rod occurs mainly when an axi-
`ally acting stress is applied to a composite mass consist-
`ing of a FRP sucker rod and the surrounding resin. 30
`Referring to the tapered cross section of an annular
`depression shown in FIG. 2B, stress am is applied to the
`tapered section in the axial direction, and stress o-t is
`applied to the tapered section in the crosswise direction.
`The magnitude distribution of these two types of stress 35
`is indicated in the graph shown in FIG. 2A, in such a
`manner that it corresponds to an equivalent location of
`the tapered cross section shown in FIG. 2B. If taper
`angle a is reduced, a maximum axial stress a-n will
`decrease, ensuring an increase in breakage strength. 40
`However, this results in a drawback in that sucker rod
`10 tends to fall out of hole 4 of metal pin 2. Therefore,
`it is important to establish a proper balance between an
`axially acting stress and a diametrically acting stress.
`The contact pressure of the coupling acting on the 45
`periphery of the sucker rod suddenly rises at that point
`at which the diameter of the metal pin is increased to a
`certain constant level. The contact pressure increases
`slightly toward the closed end of the sucker rod-receiv-
`ing hole. Consequently, the prior art metal pin, wherein 50
`a plurality of tapered portions have the same angle and
`length, is accompanied with the drawback that the
`sucker rod breaks readily at the inlet to the second
`tapered portion, at which a stress applied from the sur-
`rounding region increases sharply. (cid:9)
`Therefore, the sucker rod coupling pin according to
`the present invention is characterized that the angle of
`inclination increases toward the closed end of the
`sucker rod-receiving hole, thereby reducing the stress
`exerted by the metal pin against the periphery of the 60
`sucker rod, and decreasing the diametrically acting
`metal pin stress. Now let it be assumed that the tapered
`portions have the same length. Then, that tapered por-
`tion which has a greater taper angle undergoes a greater
`axial stress, and breakage will most likely take place at 65
`the tapered portion positioned near the closed end of
`the sucker rod-receiving hole. The present invention
`offers the advantage that since the length of the tapered
`
`55
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`4,822,201
`
`4
`portion decreases as the taper angle increases, the axial
`stress is more uniform in magnitude.
`Tensile strength tests were carried out to ascertain
`the above-mentioned advantages of the present inven-
`tion, in comparison with the prior art metal coupling
`pin. The sucker rod diameter measured 22 mm in both
`the conventional and the present coupling pin systems.
`In the prior art (FIG. 4), angle of inclination a mea-
`sured about 4°, and taper length 1 measured 25.4 mm
`throughout the samples. In contrast, in a preferred em-
`bodiment of the sucker rod coupling pin of the present
`invention (FIG. 1), the angles of inclination al, a2, and
`a3 respectively measure 4°, 5°, and 6°, and the taper
`lengths 11, 12, and 13 respectively measure 30, 27, and 25
`mm. 10, 14, and 15 respectively measure 20, 5, and 10
`mm. FIG. 3 showing tensile load displacements shows
`that such a sucker rod coupling pin embodying the
`present invention has a tensile strength about 20%
`greater than the prior art device.
`What is claimed is:
`1. A coupling pin for use with a sucker rod, and
`which is made from fiber-reinforced plastics material,
`comprising:
`an elongated hole in said coupling pin, one end of
`which is closed, and the other end of which is open
`for the insertion of a sucker rod in said elongated
`hole; and
`a plurality of annular depressions in the inner wall of
`said elongated hole, said annular depressions being
`arranged in a series from the open end to the closed
`end of said elongated hole, and, as viewed cross-
`wise, said annular depressions each including a first
`tapered, substantially straight, surface portion hav-
`ing a given angle of inclination, the angle of inclina-
`tion of said tapered portions of each of said annular
`depressions being such that the diameter of the
`respective annular depression increases toward
`said closed end of said elongated hole;
`at least one of said first tapered surface portions being
`longer in length than a preceding first tapered sur-
`face portion, said preceding tapered surface por-
`tion being located more toward said closed end of
`said elongated hole than said at least one first ta-
`pered surface portion; and
`said first tapered surface portions progressively in-
`creasing in angle of inclination as their location
`varies from said open end to said closed end of said
`elongated hole.
`2. The coupling pin according to claim 1, wherein:
`there are provided first, second and third annular
`depressions in said inner wall of said elongated
`hole;
`and, as viewed crosswise, said first, second and third
`annular depressions each have two tapered surface
`portions which comprise said first tapered surface
`portion and a second tapered surface portion, said
`first tapered surface portions of each annular de-
`pression facing said closed end of said elongated
`hole and said second tapered surface portions of
`each annular depression facing said open end of
`said elongated hole;
`said second tapered surface portions facing said
`closed end of said elongated hole each having a
`larger angle of inclination than that of said first
`tapered surface portions facing said open end of
`said elongated hole; and
`
`Page 7 of 8
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`

`
`5
`said first, second, and third annular depressions are
`arranged in this order, as counted from said open
`end to said closed end of said elongated hole.
`3. The coupling pin according to claim 2, wherein:
`said first tapered surface portions of said first, second 5
`and third annular depressions, have respective
`lengths, in the axial direction of said elongated
`hole, which progressively decrease from said open
`end toward said closed end of said elongated hole,
`and which lengths respectively measure about 30, 10
`27, and 25 mm; and
`the angles of inclination of said first tapered surface
`portions of said first, second and third annular
`depressions measure approximately 4°, 5°, and 6°,
`respectively. (cid:9)
`4. The coupling pin according to claim 3, wherein
`said elongated hole has a cylindrical portion between
`said open end and a first of said annular depressions.
`5. The coupling pin according to claim 4, wherein
`said cylindrical portion has an inner diameter which is 20
`larger than the outer diameter of a sucker rod to be
`inserted therein.
`6. The coupling pin according to claim 5, wherein
`said annular depressions are immediately adjacent each
`other such that a first tapered surface of one of said 25
`annular depressions meets a second tapered surface of
`the adjacent annular depression to define a junction
`therebetween.
`7. The coupling pin according to claim 6, wherein
`said junction defines a surface portion having substan- 30
`
`15
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`4,822,201
`
`6
`tially the same inner diameter as said cylindrical portion
`of said elongated hole.
`8. The coupling pin according to claim 6, wherein
`said junctions are chamfered.
`9. The coupling pin according to claim 1, wherein
`said annular depressions are immediately adjacent each
`other such that a first tapered surface of one of said
`annular depressions meets a second tapered surface of
`the adjacent annular depression to define a junction
`therebetween.
`10. The coupling pin according to claim 9, wherein
`said junctions are chamfered.
`11. The coupling pin according to claim 5, wherein
`said elongated hole has a further cylindrical portion
`between said closed end and an adjacent annular de-
`pression, said further cylindrical portion having sub-
`stantially the same inner diameter as said first-men-
`tioned cylindrical portion.
`12. The coupling pin according to claim 1, wherein
`said elongated hole has a cylindrical portion between
`said open end and a first of said annular depressions.
`13. The coupling pin according to claim 12, wherein
`said elongated hole has a further cylindrical portion
`between said closed end and an adjacent annular de-
`pression.
`14. The coupling pin according to claim 13, wherein
`said cylindrical portions have substantially the same
`inner diameter.
`
`35
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`40
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`45
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`50
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`55
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`60
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`Page 8 of 8