US3326581A - Well drilling pipe construction and the like - Google Patents

Description

June 20, 1967 LIP FOU WONG 3,326,581

WELL DRILLING PIPE CONSTRUCTION AND THE LIKE Original Filed Oct. 13, 1961 2 SheetsSheet 1 FIG-2 FIG-l FIG-3 INVENTOR. LIP FOU WONG BY m 254% kazzw HIS ATTORNEYS June 20, 1967 FOU ON 3,326,581

WELL DRILLING PIPE CONSTRUCTION AND THE LIKE Original Filed Oct. 13, 1961 2 Sheets-Sheet 2 INVENTOR. LIP FOU WO NG FIG-4 BY Z [W5 xkuzzw HIS ATTORNEYS United States Patent M 2 Claims. (Cl. 235173) This is a continuation of application Ser. No. 144,949, filed Oct. 13, 1961 and now abandoned.

This invention relates generally to well drilling pipe constructions and the like.

More particularly it relates to constructions for use in drilling relatively deep wells such as those that may reach a depth of from several hundred to several thousand feet.

In drilling relatively deep Wells, a plurality of pipe sections, such as thirty feet long, more or less, are serially joined together by tool joints adjacent the top of the well to form a long drill pipe or drill string which is used to drive, naise or lower a drill bit at the lower end of the drill string. A drilling fluid or abrasive mud is circulated down inside the long drill string to the bottom of the well where such fluid is discharged at the bottom of the well through the drill bit. The drill bit bores the well deeper and deeper, with a corresponding lengthening of the drill string by the addition of more pipe sections at the top of the drill string. The drilling fluid picks up the cuttings and carries them upwardly on the outside of the drill string to the top of the well. The drill string may be used to rotate the drill bit directly, or the drilling fluid may be used to rotate the drill bit, :as in turbo drilling, on the hydraulic motor principle.

The circulation of the drilling fluid, or mud downwardly through the drill string to the bottom of the well, and then upwardly outside of the drill string back to the top of the well, involves a relatively large amount of frictional resistance, which requires relatively large power consumption and relatively large capacity pumping equipment.

One of the objects of this invention is to provide a construction in which the frictional resistance to the circulation of the drilling fluid within the drill string is reduced materially in comparison with previous constructions. Because of the large number of tool joints in a deep well pipe string, the reduction of friction loss at each joint by this invention provides a substantial saving in pumping operation and equipment.

Another problem involved in the drilling of relatively deep wells is the weight of the drill string itself, which grows greater and greater as the length of the drill string increases with the increase in the depth of the well. Heretofore steel pipe has been used to produce the drill string, and the weight of the steel drill string become very large and imposes great loads on the equipment used to rotate, raise and lower the drill string.

Another object of this invention is to reduce the weight of the drill stern in comparison with previous drill strings which are made of steel pipe. According to this invention relatively heavy metal joint members, such as steel joint members, and relatively light metal pipe sections, such as aluminum alloy pipe sections are used to provide a lighter drill string.

The frictional resistance to the flow of drilling fluid or abrasive mud is reduced, according to this invention, by the use of pipe sections of uniform internal diameter which are connected with each other by joint members of this invention, which are secured to the ends of the pipe sections. The joint members have an internal flow diameter substantially equal to the internal flow diameter of 3,326,581 Patented June 20, 1967 the pipe sections. The inner flow diameters of the pipe sections and of the joint members are smoothly joined together to form a substantially smooth, constant diameter fluid passageway, with only a relatively narrow, substantially frictionless, inward groove construction between the joint members. This groove construction permits efiicient construction and operation of the threaded engagement of the joint members, so that the joint members may be threadedly engaged at the top of the well with relative ease. The internal flow diameters of the joint construction are gently tapered for relatively short distances adjacent the groove construction in a manner to reduce the formation of eddy currents in the abrasive mud or drilling fluid adjacent such groove construction, to produce a relatively frictionless or laminar flow of the mud past the groove construction. These gently tapered joint constructions prevent the wearing away or cavitation erosion by the eddy currents in the mud which otherwise would particularly wear away the aluminum alloy pipe sections adjacent the down stream side of the joint members.

The weight of the drill string is reduced, according to this invention, by using pipe sections made of light metal, such as aluminum alloy and the like, for the production of pipe sections. The pipe sections have joint members semipermanently secured to the ends of the pipe sections. These joint members are made of relatively heavy metal, such as steel and the like. The joint members are secured to the ends of the pipe sections by any suitable semi-permanent construction such as by a combined use of a threaded construction and a heat-shrinking procedure whereby a joint member is firmly secured tat each end of the pipe section.

Accordingly, it is another object of this invention to provide a pipe and joint construction which is of relatively light weight and easy openation.

Another object of this invention is to provide a Well drilling pipe construction and the like having one or more of the features herein disclosed.

Another object of this invention is to provide a method of assembly and/or operation of the well drilling pipe construction and the like having one or more of the features herein disclosed.

Other objects are apparent from this description and/or the accompanying drawings in which:

FIGURE 1 is a diagrammatic view of part of a well with pipe sections in the well and other pipe sections ready to be joined to the drill string and to be lowered into the well.

FIGURE 2 is an enlarged view, partly in elevation and partly in cross-section, of parts of two pipe sections and two joint members joined together.

FIGURE 3 is a view similar to FIGURE 2 but showing the joint members separated.

FIGURE 4 is a view of part of FIGURE 2 further enlarged.

FIGURE 5 is a diagrammatic view of part of FIG- URE 4 in greatly enlarged scale.

FIGURE 6 is a diagrammatic showing of a suitable threading, land telescoping and heat shrinking procedure between the pipe section and the joint members.

A partially drilled well is diagrammatically indicated at 10, in FIGURE 1. The well 10 contains a plurality of pipe sections 12. Another pipe section 12 is shown directly above the well, ready to be attached to the drill string produced by the sections 12 within the well. A plurality of additional pipe sections 12 are shown adjacent the well in readiness to be serially added to the drill string as the depth of the well is increased.

The well 10 may have an outer casing 11 which may extend down in the well any desired distance such as from near the top of the well to the bottom of the well.

A tool joint member 14 is somewhat permanently secured to one end of the pipe section 12. Another tool joint member 16 is semi-permanently secured to the other end of the pipe section 12.At the top of the well, the joint member 14 of the pipe section about to be joined may be threadedly engaged into the joint member 16 of the topmost pipe section 12 of the drill string. The joint members which have been united and are within the well structure are indicated by the numerals 16, 14, to desighate that the joint members have been united by a temporary threaded engagement elsewhere described.

Pipe handling machinery and fluid circulating machinery are also used near the top of the well and are well known and are therefore not illustrated. A crane or derrick construction, not shown, is cap-able of lifting the pipe sections 12 and aligning them with the drill string'of the well. The machinery is also capable of rotating the drill string at the desired speed either directly to rotate the drill bit 18 at drilling speed at the bottom of the well or else to cause turbo drilling action in the drill 18 in those constructions where the drill bit 18 has a hydraulic motor operated by the flow of the drilling fluid through the drill bit to rotate the cutting members of the bit 18.

The drilling fluid or mud is circulated downwardly through the inner flow passageways 20, 22, 24 and 20, FIGURE 2, of the pipe and joint constructions so that it emerges at the drill bit 18 at the bottom of the well. There the drilling fluid picks up the drillings and carries them upwardly outside of the pipe sections 12 and joint members 14 and 16, as indicated by the arrows 26 in FIGURE 1, so that the drilling fluid and the cuttings are discharged through a suitable discharge pipe 28, where the drillings may be separated in a well known manner in the drilling art. The downward flow of the drilling fluid is indicated by the arrows 30, FIGURE 1, and it takes place within the passageways 20, '22, 24 and 20 of FIG- URE 2. t

It is to be noted that each pipe section 12 has one of its joint members 14 at one end and the other of its joint members 16 at the opposite end. However, the joint member of one pipe section 12 threadedly engages the joint member 16 of an adjacent pipe section 12 as is about to be done at the top of the well of FIGURE 1.

Referring now to FIGURES 2 to 5, the pipe section 12 may, if desired, be made of aluminum alloy or any other desired metal.

For convenience, certain words indicating direction, such as upper, lower, etc., are used for convenience in description, but it is to be understood that the members so described may have other directions, as is obvious.

The lower enlarged end 32 of any pipe section 12 may have the joint member 14, which is also known as a pin joint member, semi-permanently secured to the end 32. Conveniently this may be accomplished by threading the outer surface of the end 32 and the inner surface of the pin member 14 at 34 and by providing inner and outer lands 36 on the pin 14 and end 32 respectively. The lands 36 are telescoped together. The end portion 32 of the pipe section has an end shoulder 38 which smoothly abuts a radially inwardly extending shoulder 40 in the pin member 14.

An upper or first pipe section 12 may be semi-permanently secured to the first or pin joint member by a threading and heat shrinking procedure in any desired manner. For example, the pin joint member 14 may be heated to a temperature such as 650 F. The pipe section 12 may be cooled by any suitable method such as elsewhere described, and the pin joint member 14 may be quickly threaded over the end portion 32 and may thereafter be cooled for heat shrinking and gripping action.

The internal flow diameter 20 of the first or upper pipe section 12 and the internal flow diameter of the fluidflow passageway 22 of the first or pin joint member 14 are substantially aligned and have equal internal flow diameters or internal cylindrical surfaces which smoothly abut at the shoulders 38 and 40 to form a smooth and uniform flow cylindrical passageway 20, 22.

A second pipe section 12 is shown at the lower parts of FIGURES 2 and 3 which pipe section has a second end portion 42 which may be enlarged if desired, as illustrated. The end portion 42 has a second end shoulder 44. The box joint member 16 has a radially inwardly extending shoulder 46 on said box joint 16 which smoothly and tightly abuts the second end shoulder 44. The second end portion 42 and the box joint member have aligned equal second internal flow diameters or internal cylindrical surfaces 24 and 20 with the smoothly abutting shoulders 44 and 46. The said second internal flow diameters or cylindrical surfaces 24 and 20 are equal to and aligned with the first and previously named internal flow diameters or cylindrical surfaces 20 and 22 at the top of FIGURES 2 and 3.

The joint members 14 and 16 have a threaded engagement 48 with each other. A tight outer shoulder abutment at 50 is provided at one end of the threaded engagement 48 and an inwardly directed groove construction 52 is provided between the joint members 14 and 1-6 at the other end of the threaded engagement 48.

The shoulder abutment 50 is formed by the shoulders I 53 and 54 on joint members 14 and 16. The groove construction 52 is formed mainly by the end or shoulder 72 and shoulder 74 of the joint members 14 and 16.

Referring now more particularly to FIGURES 4 and 5, the inner flow diameters or flow passageways 22 and 24 of the joint members 14 and 16 are gently tapered or circularly frusto-conically shaped for a relatively short distance outwardly toward and adjacent the groove construction 52, as indicated respectively at 60 and 62. This gently tapered circular frustoconical construction at 60 and 62 greatly reduces the eddy turbulence which would otherwise be produced by the groove construction 52, if the gently tapered circular frustoconical construction 60 and 62 were not used, and prevents or greatly retards the cavitation erosion on the down stream side of the groove construction 52 which would otherwise take place in the passageway 24 and 20 directly below the groove construction 52.

The mud flow past the groove construction 52 is substantially a laminar flow of the same substantially frictionless resistance as in the smooth passageways 20, 22, 24 and 20. Further description is elsewhere given.

The tapered engagement 48, FIGURES 2 and 4, is produced by the threaded constructions 64 and 66, FIGURE 3, which engage each other to produce the threaded engagement 48 of FIGURES 2 and 4. The various threads shown in FIGURES 26 are diagrammatically shown. However, they actually may be of any well known detailed construction, such as approved by the American Petroleum Institute.

The notched or grooved construction 52 is provided to permit certain machining requirements which provide easily machined threaded constructions immediately adjacent the ends 68 and 70 of the threaded construction 48, and yet maintain a groove construction with a substantially laminar flow of mud past the groove.

The threaded construction 48 is so made that the shoulders 53 and 54 may come together tightly at the upper end of the threaded engagement 48. However, because of machining consideration, the end 72 of the joint member 14 will not engage the shoulder 74 of the joint member 16 but has a plus or minus tolerance which slightly varies the groove width 52 due to machining tolerances. The machining operations, according to this invention, are so governed that the groove 52 is relatively small or narrow and is made as narrow as is possible while still permitting desirable tolerance. This relatively narrow groove 52 is combined with the gently tapered circular frustoconical portions 60 and 62 to produce the substantially laminar flow of abrasive mud elsewhere described.

Due to variations in threading machinery, etc., the following variations may take place in the groove 52, the dimensions being given for pipe with a 4 /2 inch outside diameter, and also for pipes in the order of from 2 inches to 6 /2 inches outside diameter of the main body of the pipes 12. The pipes 12 may be in the order of A; inch thickness at their thinnest part and in the order of of an inch at their thickest part. The thickest parts of the joint members 14 and 16 may be 1% inches and the joint members may be in the order of 14%, inches in length plus or minus Ms inch manufacturing tolerance. The other parts of the joint construction may be more or less equal to proportional scale as shown in the drawings, unless otherwise specifically mentioned.

Manufacturing tolerances on the length of the pin member being /3 inch plus or minus, the distance from A to B, FIGURE 5, or the inner width of the groove construction may be in the order of from A; to inch. The distance from A to D may be in the order of A3 inch. The distance from B to C may be in the order of from to inch, with A; being now preferred. The taper at 69 may be in the order of The distance from B to D or the outer width of the groove construction may be in the order of from zero to A inch. The distance from A to E may be in the order of /2 inch. The distance from F to G or width of the taper 62 may be in the order of of an inch and distance from H to I or depth of the main part of groove construction 52 may be in the order of 5 inch. 7

The joint member 16 and pipe 12 may have a threaded engagement at 80 and a telescoping land engagement at 82, FIGURES 2 and 3. The joint member 16 may be semi-permanently secured to the pipe section 12 by heat shrinking and threading procedures elsewhere referred to.

For example, referring to FIGURE 6, either of the joint members 14 and 16 may be threaded and shrunk on to the respective pipe section 12 as shown in FIGURE 6. The joint members 14 and 16 may be made slightly smaller than the cooperating parts of the pipes 12 while both are at the same temperature. A watertight resilient plug 84 is placed at the end of the pipe 12 which is about to engage a joint member. The right end 12A of the pipe 12 is placed at a lower position than the left end 128 of the pipe 12 by a height equal to about the diameter of the pipe 12. A water hose 86 is placed in the pipe 12 in readiness to inject a body of water in the pipe 12 when the heat shrinking procedure is started. The joint member 16 is illustrated, but the procedure is equally applicable to the joint member 14. Either joint member is heated to a temperature of about 650 F. to give it a slightly larger diameter and is quickly threaded and telescoped over the end of the pipe 12 while a body of water is maintained in the end of the pipe 12 by the action of the plug 84. The feeding of cooling water into the pipe 12 maintains a body of water in the pipe sufiicient to maintain the telescoping parts of the pipe 12 at or below 180 F. This prevents loss of temper in the aluminum alloy pipe 12. The body of water is maintained in the right end of pipe 12 because the left end of pipe 12 is higher by one diameter, more or less, than the right end of pipe 12. After the joint member has been telescoped and threaded against the pipe 12, then the joint member 16 or 14 is cooled by a water spray delivered by a spray head 88 in sufficient quantity to cool the joint member 16 or 14. This heat shrinks the joint member on the pipe 12 and semi-permanently attaches joint member to the pipe 12. The plug 84 is then removed. The cooling water may then be drained from the pipes. The left end of the pipe 12 may then have a pin joint member 14 similarl applied thereto, or vice versa.

Several advantages are obtained by the construction of the various parts adjacent the groove 52. For example, the sloping construction of the Wall 74 permits the sweeping out of any dried mud which may have rested on the sloping wall 74 from a previous operation. This mud or 0 drilling fluid dries relatively hard, so that it is difiicult to remove the same. However, the combined grinding and squeezing action of the end wall 72 as it is downwardly threaded into the member 16 grinds or breaks oif any such dried mud and sweeps it out of the joint 52 in a manner much superior to a construction in which the wall 74 would be substantially a right-angled wall parallel to the wall 72. The circular edge G is of greater diameter than the circular edge K and also greater than the diameter of the common general flow surface indicated by the line L in the FIGURE 5.

When the drilling fluid flows downwardly, as indicated by the arrow 30, FIGURE 4, the flow stream in the passage 22 is slightly slowed as it passes the gradual and gentle expansion of taper 60. Any turbulence in the groove 52 which would have been caused by an abrupt or rightangled corner at H in FIGURE 5 is materially reduced by the taper 60. Likewise, at the circular edge G, the slight eddy action produced in groove 52 fans inwardly gently toward the center of the flow stream, but returns to the tapered wall 62 without any sharp impinging action, so that the eddy currents are greatly reduced in grinding power and are prevented from producing any cavitation erosion within the steel passage 24 and particularly within the adjacent parts of the aluminum wall 42 which surround the passage 20 adjacent the downstream side of the groove 52.

Previous groove constructions between joint members have been in the order of from one to one and a quarter inches in width, whereas the groove construction of this invention is from /s to inches in width, which combined with the short tapered surfaces 60 and 62 greatly reduces the eddy current eifects, as has been observed in test models.

A sharp corner at F, in FIGURE 5, in combination with a wide groove at 52 would cause backfeeding action of the eddy currents on the downstream side of the groove which would produce high cavitation erosion on the adjacent downstream inner surfaces 24 and 20, FIGURE 5.

The erosion on the steel surface 24 is not as severe as that on the aluminum alloy surface 20, because the Brinnell hardness of aluminum is less than that of steel. Hence this invention is particularly advantageous in connection with aluminum alloy pipe drill strings. This inventron permits the use of light weight aluminum pipe in deep well pipe strings where excess weight in the pipe string is very undesirable.

The ends 32 and 42 of pipes 12 may be work hardened bv hammering, rolling and the like for added strength. These pipes may be made of aluminum alloy 2014-T6 or 7075-16. The steel of the joint members may be SAE- 4140 steel or the like.

Since the aluminum pipe sections 12 generally are in the order of 30 feet long and the steel tool joints 14, 16

P are relatively short, a very material weight reduction is obtained by the use of aluminum in the long pipe sectrons 12, while relatively strong and hard joints are provided.

The uniform inner fiow diameters 20, 22 and 24 in the mam parts of the drill string, the smooth inner joints at 38, 40 and 44 and 46 and the relatively short and gentle tapers 60 and 62 adjacent the narrow groove construction :52 materially reduce the frictional loss in the fluid within the drill string and prevent undue eddy currents and erosion cavitation by the abrasive fluid in the joint members and particularly in the upper ends 42 of the aluminum pipes 12 which are on the down stream side of the groove construction 52.

A new light weight and erosion proof pipe string construction has been provided by this invention which is particularly useful in connection with deep well drilling operations.

While the form of the invention now preferred has been disclosed as required by statute, other forms may be used,

all coming within the scope of the claimed subject matter which follows.

I claim: v

1. In combination: a first pipe section made of aluminum alloy and including a first end portion with a first end shoulder; a tool pin joint member made of steel shrunk on said first end portion and including a radially inwardly extending shoulder on said joint member smoothly and tightly abutting said first end shoulder on said first end portion, said first end portion and pin joint member having aligned equal first internal flow cylindrical surfaces with smoothly abutting shoulders; a second pipe section made of aluminum alloy and including a second end portion with a second end shoulder; a tool box joint member made of steel shrunk on said second end portion and including a radially inwardly extending shoulder on said box joint member smoothly and tightly abutting said second end shoulder, said second end portion and box joint member having aligned equal second internal flow cylindrical surfaces with smoothly abutting shoulders, said second internal flow cylindrical surfaces being equal to and aligned with said first internal flow cylindrical surfaces, said joint members having a threaded engagement with each other with a tight outer shoulder abutment at one end of said threaded engagement and with an inwardly directed groove construction between said joint members at the other end of said threaded engagement, the main inner flow cylindrical surfaces of said joint members being equal and the remaining minor internal flow surfaces of said joint members having gently and smoothly tapered inner joint member circular frustoconical surfaces at a relatively small angle with respect to said cylindrical surfaces for a relatively short distance outwardly toward and adjacent said groove construction the side walls of said groove construction forming relatively large angles with respect to said cylindrical surfaces and in which one of said joint-members is a downstream joint member and the other of said joint members is an upstream joint member, and in which the length of the frustoconical surface of said upstream joint member is less and forms a slightly greater small angle with respect to said cylindrical surfaces than the angle formed by the inner frustoconical surface of said downstream member, the side walls of said groove construction including a relatively wide fiat end wall on said upstream joint member and adjacent said threaded engagement, and a continuous slanting frustoconical wall at the bottom of said groove construction on said downstream joint member, and in which said shorter distance is in the order of A5 inch and said slightly greater small angle is in the order of with respect to the longitudinal axis of said joint members and in which said other short distance is in the order of /2 inch and said other small angle produces a width of taper of of an inch from said main inner cylindrical surface and in which said flat end wall is substantially perpendicular to said cylindrical surfaces and in which said continuous slanting frustoconical wall is downwardly directed, and in which the outer width of said groove construction is in the order of /s", and in which said groove construction is immediately adjacent said threaded engagement.

2. In combination: a first named pipe section having a first named end portion with a first named end shoulder; a pin joint member secured on said first named end portion with a radially inwardly extending shoulder on said joint member smoothly and tightly abutting said first named end shoulder, said first named end portion and pin joint member having aligned equal firstnamed internal cylindrical surfaces with smoothly abutting shoulders; a second named pipe section having a second named end portion with a second named end shoulder; a box joint member secured on said second named end portion with a radially inwardly extending shoulder on said box joint member smoothly and tightly abutting said second named end shoulder, said second named end portion and box joint member having aligned equal second named internal cylindrical surfaces with smoothly abutting shoulders, said second named internal cylindrical surfaces being equal to and aligned with said first named internal cylindrical surfaces, said joint members having a threaded engagement with each other with a tight outer shoulder abutment at one end of said threaded engagement and with an inwardly directed groove construction between said joint members at the other end of said threaded engagement, with the side walls of said groove forming relatively large angles with respect to said first and second internal cylindrical surfaces the main internal cylindrical surfaces of said joint members being equal and the remaining minor internal flow surfaces of said joint members having gently and smoothly tapered inner joint circular conical surfaces for a relatively short distance outwardly toward and adjacent said groove construction at relatively small angles with respect to said internal cylindrical surfaces and in which said box joint member is a downstream joint member and the pin member is an upstream joint member, and in which the conical surface of said pin joint member extends a shorter distance and at a slightly greater small angle than the downstream conical surface of said box joint member, the side walls of said groove construction including a relatively wide upper flat end wall on said upstream joint member and adjacent said threaded engagement, and a continuous slanting frustoconical wall at the bottom of said groove construction on said downstream joint member, and wherein the length of said taper in said pin joint member is in the order of /s inch, and the length of said taper in said box joint member is in the order of /2 inch, and in which the relatively small angle of the taper of said pin joint member is in the order of 10 with respect to said internal cylindrical surfaces of said joint members and in which the relatively small angle of the taper of said box joint member produces a width of taper of of an inch from said internal cylindrical surfaces of said joint members and in which said flat end wall is substantially perpendicular to said cylindrical surfaces, and in which said continuous slanting frustoconical wall is downwardly directed, and in which the outer width of said groove construction is in the order of /s", and in which said groove construction is immediately adjacent said threaded engagement.

References Cited UNITED STATES PATENTS 2,062,407 12/ 1936 Eaton 285-27 X 2,450,453 10/1948 Boehm 285334 X 2,505,747 4/1950 Willke 285-334 X 2,532,632 12/1950 MacArthur 285333 X 2,992,021 7/1961 Nay 285334 3,126,214 3/1964 Wong et al 285333 X CARL W. TOMLIN, Primary Examiner.

THOMAS F, CALLAGHAN, Examiner.

Claims (1)

1. IN COMBINATION: A FIRST PIPE SECTION MADE OF ALUMINUM ALLOY AND INCLUDING A FIRST END PORTION WITH A FIRST END SHOULDER; A TOOL PIN JOINT MEMBER MADE OF STEEL SHRUNK ON SAID FIRST END PORTION AND INCLUDING A RADIALLY INWARDLY EXTENDING SHOULDER ON SAID JOINT MEMBER SMOOTHLY AND TIGHTLY ABUTTING SAID FIRST END SHOULDER ON SAID FIRST END PORTION, SAID FIRST END PORTION AND PIN JOINT MEMBER HAVING ALIGNED EQUAL FIRST INTERNAL FLOW CYLINDRICAL SURFACES WITH SMOOTHLY ABUTTING SHOULDERS; A SECOND PIPE SECTION MADE OF ALUMINUM ALLOY AND INCLUDING A SECOND END PORTION WITH A SECOND END SHOULDER; A TOOL BOX JOINT MEMBER MADE OF STEEL SHRUNK ON SAID SECOND END PORTION AND INCLUDING A RADIALLY INWARDLY EXTENDING SHOULDER ON SAID BOX JOINT MEMBER SMOOTHLY AND TIGHTLY ABUTTING SAID SECOND END SHOULDER, SAID SECOND END PORTION AND BOX JOINT MEMBER HAVING ALIGNED EQUAL SECOND INTERNAL FLOW CYLINDRICAL SURFACES WITH SMOOTHLY ABUTTING SHOULDERS, SAID SECOND INTERNAL FLOW CYLINDRICAL SURFACES BEING EQUAL TO AND ALIGNED WITH SAID FIRST INTERNAL FLOW CYLINDRICAL SURFACES, SAID JOINT MEMBERS HAVING A THREADED ENGAGEMENT WITH EACH OTHER WITH A TIGHT OUTER SHOULDER ABUTMENT AT ONE END OF SAID THREADED ENGAGEMENT AND WITH AN INWARDLY DIRECTED GROOVE CONSTRUCTION BETWEEN SAID JOINT MEMBERS AT THE OTHER END OF SAID TRHREADED ENGAGEMENT, THE MAIN INNER FLOW CYLINDRICAL SURFACES OF SAID JOINT MEMBERS BEING EQUAL AND THE REMAINING MINOR INTERNAL FLOW SURFACES OF SAID JOINT MEMBERS HAVING GENTLY AND SMOOTHLY TAPERED INNER JOINT MEMBER CIRCULAR FRUSTOCONICAL SURFACES AT A RELATIVELY SMALL ANGLE WITH RESPECT TO SAID CYLINDRICAL SURFACES FOR A RELATIVELY SHORT DISTANCE OUTWARDLY TOWARD AND ADJACENT SAID GROOVE CONSTRUCTION THE SIDE WALLS OF SAID GROOVE CONSTRUCTION FORMING RELATIVELY LARGE ANGLES WITH RESPECT TO SAID CYLINDRICAL SURFACES AND IN WHICH ONE OF SAID JOINT MEMBERS IS A DOWNSTREAM JOINT MEMBER AND THE OTHER OF SAID JOINT MEMBERS IS AN UPSTREAM JOINT MEMBER, AND IN WHICH THE LENGTH OF THE FRUSTOCONICAL SURFACE OF SAID UPSTREAM JOINT MEMBER IS LESS AND FORMS A SLIGHTLY GREATER SMALL ANGLE WITH RESPECT TO SAID CYLINDRICAL SURFACES THAN THE ANGLE WITH RESPECT TO SAID CYLINDRICAL SURFACE OF SAID DOWNSTREAM MEMBER, THE SIDE WALLS OF SAID GROOVE CONSTRUCTION INCLUDING A RELATIVELY WIDE FLAT END WALL ON SAID UPSTREAM JOINT MEMBER AND ADJACENT SAID THREADED ENGAGEMENT, AND A CONTINUOUS SLANTING FRUSTOCONICAL WALL AT THE BOTTOM OF SAID GROOVE CONSTRUCTION ON SAID DOWNSTREAM JOINT MEMBER, AND IN WHICH SAID SHORTER DISTANCE IS IN THE ORDER OF 1/6 INCH AND SAID SLIGHTLY GREATER SMALL ANGLE IS IN THE ORDER OF 10* WITH RESPECT TO THE LONGITUDINAL AXIS OF SAID JOINT MEMBERS AND IN WHICH SAID OTHER SHORT DISTANCE IS IN THE ORDER OF 1/2 INCH AND SAID OTHER SMALL ANGLE PRODUCES A WIDTH OF TAPER OF 1/16 OF AN INCH FROM SAID MAIN INNER CYLINDRICAL SURFACE AND IN WHICH SAID FLAT END WALL IS SUBSTANTIALLY PERPENDICULAR TO SAID CYLINDRICAL SURFACES AND IN WHICH SAID CONTINUOUS SLANTING FRUSTOCONICAL WALL IS DOWNWARDLY DIRECTED, AND IN WHICH THE OUTER WIDTH OF SAID GROOVE CONSTRUCTION IS IN THE ORDER OF 1/8", AND IN WHICH SAID GROOVE CONSTRUCTION IS IMMEDIATELY ADJACENT SAID THREADED ENGAGEMENT.

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