US2768840A - Tubing system for fluid operated pumps - Google Patents

Description

c. J. COBERLY TUBING SYSTEM Foa mum OPERATED PUMPS oct. 3o, 19.56

3 Sheets-Sheev 1 Original Filed July l, 1946 Oct. 30, 1956 C. 1 oBERLY 2,768,840

TUBING SYSTEM FOR FLUID OPERATED PUMPS Original Filed July l, 1946 3 Sheets-Shea?. 2

Oct. 30, 1956 c. J. coax-:RLY 2,768,840

TUBING SYSTEM FOR FLUID OPERATED PUMPS i Original Filed July-l, 1946 3 Sheets-Sheet 3- Unted States Patent `Op 'IUllNG SYSTEM FR FLUID OPERATED PUMPS Clarence J. Coberly, Los Angeles, Calif., assignor, by mcsne assignments, to Kobe, Inc., Huntington Park, Caiif., a corporation of California Original application July 1, 1946, Serial No. 680,679,

now Patent No. 2,593,729, dated April 22, 1952. Di- ;idtidzand this application January 27, 1949, Serial No.

7 Claims. (Cl. 284-1) The present invention relates in general to a tubing system and, since the invention is particularly applicable to a closed tubing system for fluid operated well pumps, it will be considered in such connection herein for purposes of illustration. This application is a division of my co-pending application Serial No. 680,679, tiled July 1, 1946, now Patent No. 2,593,729.

In a conventional iluid operated well pump system, operating uid is supplied to the pump under relatively high pressure through a power tubing extending downwardly in the well. As is well known in the art, such operating uid is alternatively directed by a suitable valve mechanisrn in the pump to opposite ends of a motor piston which is coupled by a piston rod to the piston of a displacement pump. Such application of operating fluid to the motor piston results in reciprocation of the motor and pump pistons so that the latter pumps well fluid from the well, such well Huid normally being conveyed upwardly to the. surface by a production tubing. In such a pump it is conventional practice to discharge the spent operating iluid from the motor cylinder into the column of pumped well liuid, or production fluid, so that the two fluids are intermixed and conveyed upwardly together through the production tubing.

As the operating fluid supplied to the pump must be clean, to prevent abrasion of the moving parts, fresh operating uid must be continuously supplied to the system. The continuous provision of such fresh operating fluid requires considerable equipment, normally in the form of settling tanks or iilters, all of which is expensive.

My aforesaid co-pending application discloses an arrangement wherein such operating tluid, instead of being mixed with the production fluid as mentioned above, is separately conveyed back to the surface of the ground for storage and re-use to actuate the fluid operated pump. With such an arrangement there is relatively little loss of operating fluid, and, consequently, the equipment provided to supply fresh operating fluid to the system need have only a relatively small capacity and can be relatively cheap and economical. As hereinbefore suggested, the present invention is particularly susceptible of application to a closed tubing system for incorporation in such an arrangement and will be considered in connection therewith for convenience.

in general, a primary object of this invention is to provide such a tubing system which includes a power tubing having separate passages for the operating iluid under pressure supplied to the pump and for the spent operating iluid discharged thereby.

Another object is to provide such a power tubing which is compact and which may be broken down readily into joints or sections for convenience in handling.

Still another object of the invention is to provide a double-walled tubing system in which the inner and outer walls are spaced apart but rigidly joined together so that they may be easily handled as a joint or section assembly.

Another object ot the invention is to provide a cou- 2,768,840 Patented Oct. 30, 1956 pling for such double-walled tubing joints, such as to form tluid-tight connections between the inner and outer tubings, respectively, of adjacent joints of the tubing.

A further object of my invention is to supply a coupling for stands of such double-walled tubing joints such as to form fluid-tight connections and such as to retain in each stand of the tubing, as it is broken from the stand below, any operating fluid contained therein, This prevents loss ot' operating iiuid and avoids what is known in the industry as a wet pulling job as the tubing system is withdrawn from the well. l prefer to accomplish this by providing suitable valves in each coupling such as to close both the inner and outer tubings as the coupling is broken, which is also an object of the invention.

Other objects and advantages will appear from the following specication and the drawings, which are for the purpose of illustration only, and in which:

Fig. l is a vertical View, partly in section, of the upper end of my tubing system installed in a well;

Fig. 2 is a downward continuation of Fig, l, showing the lower end of my tubing system installed in the well;

Fig. 3 is a diagrammatic view of the surface equipment, reduced in size relative to the scale of Figs. 1 and 2;

Fig. 4 is an enlarged vertical sectional view of the standing coupling of my invention;

Fig. 5 is a cross-sectional view taken on the line 5 5 of Fig. 4;

Fig. 6 is an enlarged vertical sectional view of the tubing coupling of my invention;

Fig. 7 is a cross-sectional view taken on the line 7-7 of Fig. 6;

Fig. 8 is an enlarged longitudinal sectional view taken through the special elbow-type coupling of the invention;

Fig. 9 is an enlarged longitudinal sectional view taken through a special separation fitting of the invention;

Fig. l0 is a cross-sectional view taken on the line 10-10 of Fig. 9;

Fig. l1 is an enlarged vertical sectional view taken through the upper end of my modified form of uid operated well pump, showing the double-walled tubing connected thereto;

Fig. 12 is a cross-sectional view taken on the line 1212 of Fig. ll;

Fig. 13 is a cross-sectional view taken on the line 13-13 of Fig. 11; and

Fig. 14 is a cross-sectional view taken on the line Referring to Figs. l and 2, the drawings show a Conventional well casing 15 set in a well, and having a production tubing 16 extending downwardly thereinto, the lower end of the production tubing being provided with a pump seat 17 on which is seated a lluid operated pump 18. To the upper end of the pump 18 is aixed a special inlet fitting 1.9 by which the pump is connected to a power tubing 20 of the invention, which power tubing extends upwardly through the production tubing` The power tubing 20 is formed of a plurality of axially aligned tubing sections 22, 22a, and 2217, commonly re ferred to in the oil industry as tubing joints. For convenience of description, only three of such tubing sections are shown, the tubing sections 22 and 22a being connected together by a tubing coupling 23, and the tubing sections 22a and 22b being connected together by a` nected together by tubing couplings like the tubingV coupling 23. The tubing sections 22, 22a, and 22h are generally similar in construction, and parts of the sections 22a and 22b which are'similar to parts of the section 22 will be referred to by similar numerals as refer to the parts of the tubing section 22, but with the sutlixes a and b added thereto respectively.

The upper end of the production tubing 16 is coupled in a conventional manner to a standard casing head 25 which is provided with a discharge nipple 25 disposed so as to convey pumped well fluid from the production tubing to a point of disposal or use (not shown). The upper end of the casing head 2S may be provided with conventional slips 27, if desired, to additionally support the power tubing. Connected to the upper end of the vertical portion of the power tubing 20 is a special elbow titting 29, which directs the power tubing horizontally therefrom to a separation fitting 30, shown in Fig. 3. To the separation fitting 30 is connected a spent power fluid line 31 which is adapted to convey spent power fluid from the fitting 3i? to a collection tank 32 which is connected at its bottom by means f a flow line 33 to a high pressure pump 3d, preferably of the triplex type, which is adapted to convey power fluid from the collection tank to the separation fitting Sil by a discharge line 35. As will be understood, the pump 34 is disposed on the surface of the ground, and may be of any type desired which is adapted to supply power fluid to the line 3S under pressure sufficient to operate the fluid operated pump 13, as is generally well known in the art. As will also be noted in the embodiment illustrated the collection tank 32 is disposed substantially above the pump 34 so that power fluid can flow by gravity under some inlet pressure from the collection tank to the pump. Obviously, means other than gravity may be provided for this purpose if desired.

Referring to Fig. ll, the fluid operated pump 18 is provided with the inlet fitting 19 at its upper end, having a central bore 44 adapted to receive operating fluid from the power tubing Zfland to convey it to the fluid operated pump to actuate the same. The inlet fitting 19 is also provided with a plurality of circumfeientially spaced longitudinal passages 45 which communicate with the upper end of the fitting and with an annular groove 46 formed in the bore of the fitting. As will be understood by those skilled in the art, the annular groove 46 is adapted. to cooperate through suitable valve mechanism (not shown) to convey spent operating fluid from the motor cylinder of the iluid operated pump 18 to the longitudinal passages 45 so that the same may be discharged upwardly therethrough and into the power tubing Ztl.

As shown in Fig. 1l, the lowermost tubing section 22 inciudes an outer 'tubing member 48 and an inner tubing member i9 concentrically disposed within the outer tubing member and spaced therefrom so as to provide an annular longitudinal space 50. The outer and inner tubing members 4S and 49 respectively, are rigidly retained in spaced relation, as shown, by two or more spacer bars Si disposed therebetween and welded or otherwise rigidly secured to the tubing members. Also, as shown in Fig. 11, the lower ends of the tubing members 48 and 49 are provided with conical seating faces 52 and 53, respectively, which are adapted to seat on and respectively form fluid-tight engagement with conical seats 54 and 55, provided on the upper end of an insert member 56. The insert member 56 is provided with a central bore 57 which is axially aligned with the inner tubing member 49 and with the central bore 44 of the inlet fitting 19 so as t0 provide fluid communication therebetween. The insert member 56 also has a plurality of circumferentially spaced longitudinal passages 53 which provide fluid cornmunication between the annular longitudinal space Si? of the power tubing 20 and the longitudinal passages 45 of the inlet fitting 19. The upper end of the inlet fitting 19 is provided with external threads adapted to receive internal threads of a coupling member 60, the upper end of which is internally threaded at 61 onto external threads 62 formed on the outer tubing member 4S. lt is to be noted that the outer tubing member 48 is provided with a straight tubular portion 63 below the threads e2, which portion is adapted to engage an annular resilient O-ring 6d carried in an annular groove 65 in the coupling member 69, so as to form a fluid-tight seal between the coupling member and the outer tubing member.

As shown in Fig. 6, the upper end of the tubing section 22 is identical in construction with the lower end, just described, but is reversed in position, providing conical seating faces 52 and 53 on the outer and inner tubing members 48 and 49, respectively, which seating faces engage in fluid-tight relation with mating conical seats 67 and 68, respectively, formed on an insert member 69. rthe insert member 69 is provided at its upper end with similar conical seats, which similarly engage conical seating faces 52a and 53a formed on the lower end ot the next succeeding tubing section 22a. The tubing sections 22 and 22a, with the insert member 69 therebetween, inthe position illustrated in Fig. 6, are adapted 'to be rigidly clamped together by the tubing coupling 23 which is threaded to the outer tubing member lfd of the tubing section 22 and to the outer tubing member 53a of the tubing section 22a. The coupling 23 is provided with a pair of spaced annular grooves tl and 7i, containing resilient O- rings 72 and 73, respectively, which engage in fluid-tight relation to the lower and upper ends of the tubing sections 22a and 22A, respectively. The insert member 69 is provided with a central bore 74 which is axially aligned with the bores of the inner tubing members i9 and @a so as to provide fluid communication therebetween, and is provided with circumferentially spaced longitudinal passages 75 which provide fluid communication between the annular space 5@ and the annular space 50a, As will also be noted, the upper end of the tubing section 22 is also provided with spacer bars 51a, which are similar to the spacer bars 51 shown in Figs. ll and 14, and the tubing section 22o is similarly provided with spacer bars at each of the ends thereof.

As best shown in Fig. 4, the tubing sections 22a and 221: are rigidly connected together by the valved coupling 24. The tubing sections 22, 22a, and 22o have substatitially identical constructions, with the exception that the upper end of the tubing section 22a is provided with u transverse valve-actuating bar 77' Welded or otherwise secured in the inner tubing member @a thereof for a purpose to be described hereinafter. 'Ehe valves coupling 24 includes an outer tubular coupling member 78 which is generally similar to the tubular coupling 23 but is somewhat longer, similarly being provided with annular fings '79 and 3i) adapted to form fluid-tight seals with the lower and upper ends of the tubing sections 22h and 22a', respectively. Also, the central part of the coupling member 73 is provided with an annular channel S1 and an inwardly projecting annular shoulder 82 providing an outer valve seat 85. As will be noted, the shoulder 232 projects into the bore S4 of the coupling member 73.

Housed within the outer tubular coupling member f3 is a valve assembly 86 provided with upper and lower heads 87 and 88, respectively, the upper head having a plurality of circumferentially spaced longitudinal passages 89 adapted to communicate with the annular space Siti; of the tubing section 22b, and the lower head being similarly provided with a plurality of longitudinal passages 9d adapted to communicate with the annular space 50a of the tubing section 22a. As illustrated, the valve assembly 86 is generally tubular in form, providing a central longitudinal passage 91 therethrough and having an external annular projection 92 providing an outer conical valve face 93 adapted to seat on the outer valve seat 83, and having an inner annular projection 94 providing an inner annular valve seat 95. Adapted to seat on the inner annular valve seat 95 is in an inner valve member 97, of the poppet type, having avalve stem 98 supported for vertical movement relative to the inner valve seat 95 by crossbars 99 and 100 secured in or formed integrally with the valve assembly 86. The valve assembly 86 is also provided at its upper and lower ends with seating faces 101 and 102, respectively, which are adapted to be engaged by the lower end of the tubing section 22b and the upper end of the tubing section 22a, respectively, in fluid-tight engagement. The operation of the valve coupling 24 will be described hereinafter.

Referring to Fig. 8 of the drawings, the elbow fitting 2S includes a vertical tubular portion 104 which is adapted to threadedly receive the upper end of the outer tubing member 13b of the tubing section 22b, and is provided with a horizontal tubular portion 105 adapted to threadedly receive one end of a tubing section 22C. The elbow fitting is provided with central bores 106 and 107 which intersect to form a central passage therethrough, and is provided with drilled passages 108 and 109 which communicate through drill ports 110 of an insert member 111 with the annular longitudinal space 50h of the tubing section 22b. The passages 108 and 109 also communicate through ports 112 of an insert member 113 with an annular longitudinal space 50c of the horizontal tubing section 22C. Similarly, the central bore 106 communicates through a bore 114 in the insert member 111 with the bore of the inner tubing member 4912, and the central bore 107 communicates through a bore 115 of the insert member 113 with the bore of the inner tubular member 49C of the horizontal tubing section 22e. The elbow fitting 29 is provided with conical seats 116 and 117 against which the insert members 111 and 113, respectively, seat to form fluid-tight engagement with the elbow fitting. Similarly, the insert members 111 and 113 seat against conical seats 118 and 119 of the inner tubing members 9b and 49e, respectively, to form huid-tight engagement therewith. In this form of construction, however, the elbow fitting 29 is cut away at 120 and 121 so that no duid-tight fit is made between the insert members 111 and 113 and the outer tubing members 48b and 48C, respectively, the seal between such outer tubing members and the elbow fitting being provided by O- rings 122 and 123. As will be understood, the elbow fitting 29 secures the tubing sections 22B and 22C together so as to provide a pair of fluid paths therebetween.

Referring to Figs. 9 and 10 of the drawings, the separation fitting 30 provides a connection between the horizontal tubing section 22e and the spent power fluid line 31 and the discharge line 35. The fitting 30 is provided with a central bore 125 and a counterbore 126 providing an internally threaded tubular extension 127 adapted to ttedly receive the end of the horizontal tubing section 22C. Provided in the tubular extension 127 is an annular groove 128 containing an O-ring 129 adapted to forml a tiuid-tight seal between the periphery of the tubing section 22C and the fitting 30. Between the bore 125 and the counterbore 126 is a conical seat 130 against which an insert member 131 seats in iiuid-tight relation. The insert member 131 is provided with an annular cut-away portion 132 and with circumferentially spaced longitudinal ports 133 which communicate with the annular longitudinal space 50c of the tubing section 22C. The cut-away portion 132 also communicates through a radial port 135 with a fitting 136 welded or otherwise secured to the end of the spent power fluid line 31 and detachably connected to the separation fitting 30, as by screws 137. The central bore 12S likewise communicates through a radial port 138 with a fitting 139, similar to the fitting 136, and welded or otherwise secured to the end of the discharge line 35.

iIn operation, as will be understood, the power tubing is first filled with operating uid. As will be understood from Fig. 9, such operating fluid, under substantial pressure, passes into the separation fitting 30 from the discharge line 35, through the insert member 131, and into the inner tubing member 49C of the tubing section 22e, from whence it continues through the elbow fitting 29 and downwardly through the inner tubing members of the power tubing 20 to the inlet fitting 19 of the Huid operated pump 18. Such operating fluid under pressure is used, as is well known in the art, to actuate the fluid operated pump 18, and subsequently is conveyed as spent operative fluid at relatively low pressure upwardly through the longitudinal passages 45 of the inlet fitting 19 to enter the annular longitudinal space 50 of the power tubing 20, through which it is conveyed upwardly through the various fittings and couplings to the separation fitting 30, outwardly through the radial port 135 thereof into the spent power liuid line 31 from which it flows to the collection tank 32.

When it is desired to remove, or pull, the power tubing 20 from the Well, it is desirable, frequently, that little of the power uid contained therein be discharged into the production tubing 16. This may readily be accomplished with the special power tubing 20, illustrated, due to the provision of the valve coupling 24. The connection between the tubing sections 22b and 22e is first broken, at the elbow fitting 29, and then the power tubing 20 is raised until the slips 27 engage the tubing section 22a just below the valve coupling 24. The tubing section 22a is then retained stationary by the slips 27, and the power tubing section thereabove is rotated together with the Valve coupling 24 so as to unscrew the outer tubular coupling member 78 from the upper end of the tubular section 22a. As the coupling member 78 is unscrewed from the tubing section 22a it moves upwardly relative thereto, the valve assembly 86 remaining seated, temporarily, on the upper end of the tubing section 22a since its upper head 87 is freely slidable in coupling 24. Such upward movement of the coupling mem-ber 78 relative to the valve assembly 86 is continued until the valve face 93 engages the valve seat 83 in fluid-tight engagement so that upon subsequent upward movement of the coupling member. 78 the valve assembly 86 moves upwardly therewith and the power fiuid in the annular space around the valve assembly will be held against loss past the face 93. During such subsequent upward movement of the coupling member 78, as will be apparent, the valve assembly 86 is also raised therewith so as to break the engagement of the valve assembly with the upper end of the tubing section 22a. Continued upward movement of the valve assembly 86 causes the inner annular valve seat 95 to engage the inner valve member 97 in fiuid-tight engagement, which retains thereabove all of the operating fluid contained in the section 22b. Aft-er the inner valve member is thus closed, continued upward movement of the coupling member 78breaks the connection between the O-ring and the upper end of the outer tubing member 48a which, up to that time, has maintained a Huid-tight seal between the coupling member and the tubing section 22a, and the coupling member is then disengaged from the tubing section 22a therebelow. Thus, substantially all operating fluid in the tubing section 22b is retained therein by the valve coupling 24, and the tubular section 22b and any tubing sections thereabove connected thereto may be stacked in the vicinity of the well in a vertical position without losing any of the power fluid therefrom.

When the power tubing 20 is reassembled so as to run the fluid operated pump 18 back into the well, the operation is reversed, as will be understood. in this operation, obviously, the outer tubing coupling member 78 is moved down over the upper end of the tubing section 22a until the O-ring 80 forms a fluid-tight seal therebetween. Upon continued lowering of the coupling member 78, the valve actuating bar 77 engages the lower end of the valve stem 98 to move the inner valve member 97 off its seat 95 so as to again open communication between the inner tubing members 49a and 49h. Continued downward movement of the coupling member 78 permits the valve assembly 86 to seat on the upper end of the tubing section 22a and to break connection between the. conical valve face 93 of the valve assembly and the valve seat S3, so as to reopen communication between the annular spaces 50a and Sub. The coupling member 78 is then further screwed onto the tubing section 22a until its seating faces lili and 102 form fluid-tight engagement with the lower end of the tubing section 22h and the upper end of the tubing section 22a, respectively, so that sealing is not entirely dependent upon the O-rings 7 9 and Sti.

It will be apparent from the foregoing that l have provided a tubing system and fittings therefor which may be used particularly advantageously in such a closed operating iiuid system. Although I have shown and described a preferred embodiment of the invention, it will be apparent that modification thereof may be made without departing from the spirit of the invention, and, consequently, l do not intend to be limited to the specific form illustrated, but desire to be afforded the full scope of the following claims.

I claim as my invention:

l. In a tubing system, the combination of: a first tubing section including concentric first inner and outer tubular members which are spaced apart radially to provide a first annular space therebetween and which are provided with rst inner and outer annular seats, respectively, at one end of said first tubing section, said first tubing section including means intermediate its ends and extending between said first inner and outer tubular members for rigidly connecting same together in radially spaced relation; a second tubing section including concentric second inner and outer tubular members which are spaced apart radially to provide a second annular space therebetween and which are provided with second inner and outer annular seats, respectively, at one end of said second tubing section, said second tubing section including means intermediate its ends and extending between said second inner and outer tubular members for rigidly connecting same together in radially spaced relation; an insert member clamped between said first inner and outer annular seats and said second inner and outer annular seats, said insert member having an inner passage means therethrough providing fluid communication between said first and second inner tubular members and having an outer passage means therethrough providing fiuid communication between said first and second annular spaces; a coupling threaded onto said first and second outer tubular members only for so clamping said insert member; inner valve means in said inner passage means for opening said inner passage means as said'coupling is threadedly connected to said second outer tubular member and for closing said inner passage means as said coupling is threadedly disconnected from said second outer tubular member; and outer valve means in said outer passage means for opening said outer passage means as said coupling is threadedly connected to said second outer tubular member and for closing said outer passage means as said coupling is threadedly disconnected from said second outer tubular member.

2. A tubing system according to claim l wherein said inner valve means includes an inner valve seat on said insert member and includes an inner valve carried by and movable relative to said insert member and seatable on said inner valve seat7 and wherein said outer valve means includes an outer valve seat on said coupling and an outer valve carried by said insert member and seatable on said outer valve seat.

3. A tubing system according to claim 2 wherein said inner valve is of the poppet type and is provided with a stem engageable with an actuating element carried by said second inner tubular member.

4. ln a tubing system, the combination of: a first tubing section including concentric first inner and outer tubular members which are spaced apart radially to provide a first annular space therebetween and which are provided with first inner and outer annular seats, respectively, at one end of said first tubing section, said first tubing section including means intermediate its ends and extending between said first inner and outer tubular members for rigidly connecting same together in radially spaced relation; a second tubing section including concentric second inner and outer tubular members which are spaced apart radially to provide a second annular space therebetween and which are provided with second inner and outer annular seats, respectively, at one end of said second tubing section, said second tubing section including means intermediate its ends and extending betweensaid second inner and outer tubular members for rigidly connecting same together in radially spaced relation; an insert member clamped between said first inner and outer annular seats and said second inner and outer annular seats, said insert member having an inner passage means therethrough providing fluid communication between said first and second inner tubular members and having an outer passage means therethrough providing fluid communication between said first and second annular spaces; a coupling threaded onto said first and second outer tubular members only for so clamping said insert member; an inner valve means in said inner passage means and including an inner valve seat on said insert member and an inner valve seatable on said inner valve seat, said inner valve means also including an actuating element carried by said second tubing section for holding said inner valve off said inner valve seat when said insert member is clamped between said first inner and outer annular seats and said second inner and outer annular seats by said coupling; an outer valve means in said outer passage means and including an outer valve seat on said coupling and an outer valve on said insert member, said outer valve being spaced from said outer valve seat when said insert member is clamped between said first inner and outer annular seats and said second inner and outer annular seats by said coupling; and an annular sealing element disposed between and engageable with said second outer tubular member and said coupling, said annular sealing element being spaced from said second outer annular seat, when said insert member is clamped between said first inner and outer annular seats and said second inner and outer annular seats by said coupling, a distance greater than the distances which said inner and outer valves are spaced from their respective seats when said insert member is so clamped.

5. In a tubing system, aligned tubing sections each comprising rigidly connected radially spaced inner and outer tubes defining isolated inner and outer flow paths, an, insert abutting adjacent ends of at least said inner tubes in sealing relation thereto, a coupling threaded to adjacent ends of said outer tubes and clamping said insert between said tubing sections, an opening through said insert providing communication between said inner flow paths, a valve seat in said opening, a valve engageable with said seat, means carried by the inner tube of one of said sections for holding said valve ofi said seat when said insert is clamped between said tubing sections, an outer passageway providing communication between said outer flow paths, said outer passageway being defined at least in part by radially opposed portions of said insert and said coupling, said insert being axially slideable in said coupling, said portion of said coupling also defining a valve seat, and a valve element fixed on said portion of said insert movable into sealing relation with said valve seat upon axial movement of said insert in said coupling in a direction toward said one section.

6. A tubing system as defined in claim 5 wherein said insert is provided with axially spaced portions slideably engaging said coupling to be guided thereby into abutting engagement with said tubes.

7. A tubing system as defined in claim 5 including-an O-ring seal between each of said outer tubes and said coupling inwardly of the threaded connections therebetween.

(References on following page) UNITED STATES PATENTS Ellis May 8, 1906 Benckenstein Aug. 19, 1924 Steele Dee. 30, 1924 5 Peabody Jan. 13, 1925 Zimansky Aug. 18, 1925 10 Y Peabody May 10, 1927 Rieker et a1. May 16, 1933 Kitchel et al. Mar. 23, 1937 Battermann Apr. 4, 1939 Jones May 9, 1944 Parsons July 12, 1949 Frost et al. Jan. 17, 1950

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