US2680358A - Flexible conduit for high-pressure fluid - Google Patents

Description

Patented June 8, 1954 FLEXIBLE CONDUIT FOR HIGH-PRESSURE FLUID John A. Zublin, Los Angeles, Calif.

Application May 14, 1952, Serial No. 287,663

2 Claims.

The present invention relates to an assembly for providing a flexible conduit for the conveying of high pressure fluids and through the medium of which assembly a positive drive may be effected.

More specifically, the invention contemplates the provision of a flexible drill string section adapted to be interposed between a normally substantially rigid rotary drill string and a drill bit.

It is still a further and more specific object and purpose of the invention to provide a tubular, rotary drill string section through the medium of which a rotary bit may be positively driven while permitting flexing of the drill string section in all directions.

It is a more specific purpose and object of the invention to provide a rotary, flexible drill string section made up of a multiplicity of units with universal couplings therebetween so arranged as to permit each unit to partake of limited angular movement in all directions with respect to the next adjacent unit while positively transmitting rotary motion through all of said units.

It is a still further purpose and object of the invention to provide a multiple unit, relatively flexible, rotary drill string section for the conveyance of high pressure drilling fluid with minimum frictional resistance to relative angular movement of the units making up the rotary drill string section.

Further and more specific objects of the invention will become apparent as the description proceeds which will be given in conjunction with the accompanying drawings, wherein Figure 1 is a view in side elevation illustrating the invention,

Figure 2 is a detailed cross-sectional view taken through the center of Figure 1 at right angles thereto,

Figure 3 is a detailed cross-sectional view on the line 33 of Figure 2,

Figure 4 is a detailed cross-sectional view on the line 4-5 of Figure 2, and

Figure 5 is an enlarged cross-sectional view illustrating the structural details of a permissible variant of one of the universal couplings embraced in the flexible drill string section of the present invention.

Referring to Figure 1, the flexible drill string section is illustrated as made up of units It, I I and !2. It will be understood that the intermediate unit 5 I may be multiplied to any desired extent to provide a flexible, rotary drill string section of predetermined desired length. All intermediate units will be identical and conform to the construction of section ll.

The adjacent ends of juxtaposed units have intermeshing teeth. For example, the sub section It has the teeth 13 which are adapted to fit between and interengage teeth M at the upper end of the unit ll The lower end of the unit I l is provided with similar teeth l5 that engage between complementary teeth IG at the upper end of the unit l2. It will be observed that the teeth l5 at the lower end of the unit H are circumferentially displaced with respect to the teeth M at the upper end of the unit I l as indicated at a, Figure 1. This is to insure that the various points of interconnection will not lie in the same vertical planes. The sub unit it is provided with a threaded pin Il adapted to be received in the lower end of the lowermost section of a substantially rigid, rotary drill string. The lower unit l2 thatwill be seen by reference to Figure 2 is provided with an interiorly threaded recess 18 for threadedly receiving the shank of a rotary bit. When the shank of the rotary bit has been threaded into the recess [8 of the lower unit i2 and the threaded pin H has been mounted at the lower end of a normally rigid, rotary drill string, the entire unit may be rotated from the surface of the well to positively drive the bit carried at the lower end of the assembly.

Referring to Figure 2, it will be observed that the unit I! embraces an upper member i9 and a lower member 20 threadedly interengaged at 2! and secured by the weld 22. The upper member i9 is provided with a central channel extending from end to end thereof and of variable diameter for purposes to be hereinafter described. The lower member 20 is also provided with a tubular channel of special construction. The curved surface 23 and the curved surface 24 of the member 29 together provide an outer socket Within which the outer ball 25 is received. The ball 25 has a tubular extension 25 that extends well below the lower end of the member 29 to provide means for attachment to the next adjacent unit such as 12. The arrangement is such that the unit i2 may partake of movement in any direction with respect to unit II and the ball 25 with its socket 23, 24 providing a universal coupling. Ball 25 and tubular extension 26 thereof provide a central channel for the passage of drilling fluid. Interiorly of the hollow ball 25 there is provided a frusto-conical surface 21 which constitutes an annular seat for the inner ball 28. The inner ball 23 and the outer ball 25 have a common center 29. The spherical surface of the inner ball 28 contacts the frusto-conical seat 2? only over a very limited surface. The inner ball 28 is provided with a tubular extension 3 8 wholly within the channel extending through the upper member I9 of the unit it. The tubular extension 39 of the ball 23 is provided with the outwardly projecting annular flange 3i and there is compressed between this flange 3! and the shoulder 32 in the channel of member l9 a resilient ring 33 which constantly resiliently urges the ball 28 downwardlywith its spherical surface forced into contact with the frustoconical seat 2'! on the interior of the outer ball 25.

The high pressure fluid which moves through the upwardly projecting tubular extension 39 of the inner ball 28 and thence through the tubular extension 26 of the outer ball 25 is effectively prevented from leakage by two important expedients; first, the spherical surface of the ball 28 is constantly resiliently urged against the frusto-conical seat 21 and, secondly, low pressure areas in the direction of flow or" the high pressure fluid are created at those points in the assembly at which leakage might most likely be expected to occur. It will be observed that the channel through the interior of the upper member IQ of unit H is of reduced cross section in the direction of flow of fluid as indicated at 34, whereas the extreme upper end of the tubular extension 30 of the inner ball 28 is flared outwardly as indicated at 35 so that as fluid moves downwardly through member I?) and into the tubular extension 33 of the inner ball 28 a Venturi action is created at the upper end of the .tubular extension 38 of ball 28 and a low pressure area or zone results which inhibits leakage downwardly around the upper end of the tubular extension 30 and the resilient ring 33. The same action occurs at the point where fluid moves into the upper end of the tubular extension 38 from the inner channel of the threaded stem 1'! indicated at 36 in Figure 2.

It will also be observed that the inner channel 31 of the tubular extension 36 of the outer ball 25 is of substantially greater diameter than the inner channel of the tubular extension 30 of the inner ball 28. It follows that as fluid moves under pressure downwardly from the interior of the inner ball 28 into the inner channel 3? of the tubular extension 26 of the outer ball 25 a further Venturi action is created forming a low pressure area or zone just below the point of contact between the inner ball 28 and the frustoconical seat 27, which line of contact is indicated at X in Figure 5. The low pressure zone thus created at the upper end of the tubular extension 30 and immediately below the inner ball 28 tends to prevent any leakage of the high pressure fluid from the inner channel through which it flows and therefore prevents contact of high pressure fluid with the outer ball 25 and the socket surfaces 23 and 24. With this construction no great pressure need be maintained between the surface of the ball 25 and the socket surfaces 23 and 24 whereby little frictional resistance to angular movement of ball 25 with respect to surfaces 23 and 24 is encountered.

Inasmuch as the contact area between the inner ball 28 and the frusto-conioal seat 27 is practically linear and of limited extent, little resistance to relative movement of the inner ball 28 over the frusto-conical seat is encountered, even though a liquid-tight cell is maintained at this point of the structure.

In all angular positions of the units making up the flexible drill string section of the present invention the inter-engaging teeth such as l3 and id and I5 and i6 impart a positive driving action from end to end of the flexible drill string section.

To insure a firm interlock between units the lower end of the tubular extension 26 of the outer ball 25 is exteriorly threaded as indicated at 31 to be threadedly received in the socket of the juxtaposed member of the next unit such as the member 22 of unit H. A transverse hole may be drilled through the structure as indicated more specifically at 38 of Figure 4 and a locking pin 39 welded in place therein so as to firmly interlock the units of the flexible drill string section.

The expression inner ball as used herein is intended to embrace permissible variants such as shown in Figure 5 where the contact surface of the inner ball is spherical and concentric with the outer ball.

From the foregoing it will be observed that I have provided an assembly for a flexible drill string section that permits the conveyance of the high pressure drilling fluid without leakage and without requiring the exertion of excessive pressure over large contacting surfaces such as to inhibit easy angular movement of juxtaposed units of the flexible drill string section.

Having thus described my invention, what I claim is:

1. A pressure fluid conducting assembly comprising first and second generally tubular units interconnected in end to end relationship by a universal joint structure, said universal joint structure comprising an outer socket in the first of said units, an outer ball on the end of the sec 0nd of said units and positioned in said socket, an annular seat within said outer ball, an inner ball 3 within said outer ball and seating on said annular seat, a tubular extension on said inner ball telescoping into said first tubular unit, there being a fluid passageway extending longitudinally through said tubular units, through said outer and inner balls and through said tubular extensicn, an annular flange on the exterior of said tubular extension, an annular shoulder on the interior of said first tubular unit, and a cylindrical resilient packing member sealingly engaging the exterior surface of said tubular extension and the interior surface of said first tubular-unit to prevent fluid leakage between said tubular extension and said first tubular unit, said packing member being longitudinally compressed between said shoulder and said flange to urge said inner ball into seating engagement with said annular seat and said packing member.

2. A fluid conducting assembly as defined by claim 1 in which said first and second tubular units have loosely interengaging teeth at their adjacent ends to permittransmission of torque from one to the other of the units.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 149,842 Deeds Apr. 21, 1874 1,018,143 Vissering Feb. 20, 1912 1,611,467 Lonsdale Dec. 21, 1926 1,772,547 Keese et al. Aug. 12, 1930 1,827,432 Hundemer Oct. 13, 1,931

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