US3502353A

US3502353A - Releasing collar

Info

Publication number: US3502353A
Application number: US723779A
Authority: US
Inventors: Erwin Burns
Original assignee: AUDREY S CAT
Current assignee: AUDREY S CAT
Priority date: 1968-04-24
Filing date: 1968-04-24
Publication date: 1970-03-24
Anticipated expiration: 1987-03-24

Description

March 24, 1970- E. BURNS RELEASING COLLAR 2 She'ets-Sheet 1 Filed April 24. 1968 1 if March 24, 1970 E. BURNS 3,502,353

RELEASING COLLAR Filed April 24. 1968 2 Sheets-Sheet 2 United States Patent O 3,502,353 RELEASING COLLAR Erwin Burns, Los Angeles, Calif., assgnor of one-half to Audrey S. Carr, Anaheim, Calif. Filed Apr. 24, 1968, Ser. No. 723,779 Int. Cl. F161 35/00 U.S. Cl. 285-2 15 Claims ABSTRACT OF THE DISCLOSURE An elongate substantially vertical fluid conducting rotary tubing string for use in oil Wells comprising, a plurality of axially aligned, interconnected steel tubing sections of substantially uniform weight and tensile strength, said string being of predetermined length and weight and subjected to varying predetermined deadweight tensile forces which increase uniformly downwardly throughout the longitudinal extent of the string, an elongate, fluid conducting releasing collar with separable upper and lower sections and set releasing means therebetween engaged in the string a predetermined distance below the upper end thereof with its upper and lower sections connected with the opposing lower and upper ends of a predetermined pair of adjacent tubing sections, said set releasing means being set to release the sections of the collar before the cumulative forces of vertical pulling forces applied to the upper end of the string, the deadweight of the portion of the string below the collar and a predetermined maximum of supplemental frictional and holding forces acting on and through the portion of the string below the collar exceeds the tensile limits of the portion of the string above the collar, said upper and lower sections being telescopically engaged for free relative axial shifting, said holding means including one or more shear pins engaged in and extending between the upper and lower sections, said collar further including drive means to prevent relative rotation between the sections and sealing means to prevent the leakage of fluid within the collar outwardly between the sections.

This invention has to do with a novel well tool and is more particularly concerned with a tubing safety joint or releasing collar, the purpose of which is to effect breaking or separation of a string of run-in tubing, in a well structure, at a predetermined point and by the application of predetermined tensile forces in and through the tubing string.

In modern oil well drilling practices, it is common to direct the course of a Well laterally and downwardly relative to the surface site of the well. Such directional drilling results in a well bore which is normal or vertical at its upper end and which turns laterally in a single parabolic curve so that the lower end is downwardly and laterally inclined, or results in a well bore normal at its upper end and which turns laterally outwardly and then downwardly again in a compound curve with its lower end substantially vertical, but radially offset from its upper end.

As a result of the above-noted irregular and oftentimes tortuous courses in which oil wells are established, the strings of tubing and the like which must be run into the wells in the course of completion, production and service, do not hang or depend freely in and through the wells, but lay and bear against the sides of the well bores and ICC are bound or urged into pressure bearing engagement with the bores of the wells when compressive or tensional forces are applied thereto for the purpose of running such strings into or pulling them from their related wells.

The above-noted bearing and binding contact of tubing strings in directionally drilled wells frequently creates drag and frictional resistance on and through the tubing strings which is excessive and which is such that slight, ordinarily acceptable and anticipated binding, packing or freezing of well tools or apparatus on the lower ends of such strings, in the bottoms of the wells, create cumulative frictional and holding forces which exceed the tensile strength of the tubing strings. When such conditions are established and attempts are made to pull such strings from their related wells, the tubing strings break or part. Such breaking or parting of such strings under the above-noted conditions, seldom occurs at or in close proximity to the tools at the lower ends thereof, but normally occurs a substantial distance above the tools and oftentimes several thousands of feet above such tools. After breaking or parting of a tubing string, as noted, it is necessary for the drilling crew to carry out the extremely costly and time-consuming cleaning retrieving operation which consists of cutting and fishing out the leftin tubing and related tool, a piece at a time, and hailing, backscuttling, or otherwise cleaning the bore, as such cutting and fishing operations continue.

In the East Wilmington Oil Field, in the State of California, about twenty-two oil wells are being established or serviced each month. Each month in about live or six of these wells, the tubing string separates as a result of the above-noted conditions and the noted cleaning and retrieving or fishing operations must be performed thereon. The costs of correcting each such failure varies, as a general rule, between $5,000.00 and $30,000.00, with an estimated total cost of approximately $100,000.00 each month in this single oil field.

An object of my invention is to provide a novel releasing collar adapted to be engaged between predetermined sections or stands of tubing making up a run-in string of tubing, which is such that it will break, separate or part when predetermined tensile forces are exerted through the tubing string and said collar whereby the point of separation of the tubing string in the well can Ibe predetermined and controlled so as to make cleaning and retrieving of tubing and equipment left in the well, easier, quicker and less costly than present practices afford.

Another object of my invention is to provide a releasing collar of the character referred to which is such that it can safely and effectively handle all hydraulic pressures to be encountered without failure or leaking and a structure which is such that it will hold and withstand all normal and anticipated torsional forces to be encountered without twisting, turning or otherwise failing.

Still another object of the present invention is to provide a releasing collar of the character referred to which is such that the axial forces required to cause separation of its relatively separable parts and/or portions can be .easily and quickly varied, as circumstances required and without requiring extensive, costly and time-consuming overhauling and/or modification of the construction.

It is an object of my invention to provide a novel well servicing appartus, including an elongate run-in string made up of a plurality of stands of tubing and engageable in a well to extend from the upper end thereof to the lower end thereof, a well servicing tool at the lower end of the run-in string and one or more releasing collars as provided by this invention between predetermined stands of tubing and adapted to separate and effect parting of the run-in string at predetermined points along its longitudinal extent when the run-in string is subjected to predetermined maximum tensile forces.

An object of the invention is to provide a novel run-in string of tubing for well servicing tools including a plurality of axially aligned, interconnected stands of tubing and one or more collars as provided by this invention engaged between predetermined adjacent tubing stands.

The foregoing and additional objects and features of my invention will be fully understood from the following detailed description of typical preferred forms and applications of my invention, throughout which description reference is made to vthe accompaying drawings, in which:

FIG. 1 is a view of a well structure with a run-in string of tubing engaged therein and having a well servicing tool carried thereby and having my new releasing collars engaged therein;

FIG. 2 is an enlarged detailed sectional view taken as indicated by line 2-2 on FIG. l;

FIG. 3 is a view similar to a portion of FIG. 2 and showing parts in another position;

FIG. 4 is a sectional view taken as indicated by line 4-4 on FIG. 2;

FIG. 5 is a sectional view taken as indicated by line 5 5 on FIG. 3;

FIG. 6 is a sectional view taken as indicated by line 66 on FIG. 2;

FIG. 7 is an enlarged view of a portion of the structure shown in FIG. 6;

FIG. 8 is an elevational view of another form of the invention, with portions broken away to illustrate details of the construction;

FIG. 9 is an isometric view of parts provided in the construction illustrated in FIG. 8; and,

FIG. 10 is an isometric view showing a subassembly of the construction shown in FIG. 8.

In FIG. 1 of the drawings, I illustrate typical well structure W and show a run-in tubing string S engaged therein and carrying a suitable well servicing tool T at its lower end. The string of tubing S is shown provided with two releasing collars R as provided by my invention.

The well structure W illustrated in the drawings is a typical directionally drilled well structure and includes a bore 10 having a straight, vertical upper end portion 11 entering the surface 12 of the earths formation, a straight, vertical lower end portion 13 extending into an oil producing formation 14 below the earths surface 12 and on a vertical axis laterally offset from the upper portion 11 and a downwardly and laterally and, thence, laterally and downwardly compound curved central portion 15 between the upper and lower portions 11 and 13. The well bore is provided with and supported by a casing 16, which casing extends from the top of the bore into the lower portion 13 thereof and is shown terminating adjacent the top of the production formation 14. In the case illustrated, the lower end portion of the bore, below the casing and within the formation 14, is provided with a perforated liner 17 suspended from the lower end of the casing by a liner hanger and packer assembly or tool 18.

The run-in string S is made of a plurality of elongate lengths or stands of uid conducting tubing arranged and connected in end-to-end relationship. The tubing string is considerably less in diametric extent than the inside diameter of the easing and the string is greater in longitudinal extent than the casing. The run-in string S enters the top of the well Casing and extends downwardly and longitudinally therethrough and is provided at its lower end with a servicing tool T. In the case illustrated, the tool T is a gravel packing tool and is employed to distribute and deposit gravel pumped and circulated downwardly through the string S, into the perforated liner 17 and, thence, into the portion of the well bore in the formation 14 about the liner. The gravel pack is indicated by stippling in FIG. 1 of the drawings.

When gravel packing a well structure with the means illustrated in the drawings and described above, it is not infrequent that the gravel, as illustrated, migrates back up' and into the casing and becomes so compacted and lodged in the liner and the casing, about the tool and the lower end of the string S, as to freeze and hold the tool and the lower end of the string S in the well structure with such force as will prevent the withdrawal of the string and tool without breaking and parting the run-in string, some place along its longitudinal extent.

More particularly, the holding force of the compacted gravel on and about the tool and string, while not excessive in itself, is cumulative with the deadweight force of the string itself and with the frictional or dragging forces occurring between the string S and the casing, and the cumulative forces are greater and exceed the tensile limits of the tubing making up the string. As a result of the above, it will be apparent that when in a situation such as illustrated and described develops, the tubing string usually parts in the upper portion of the well structure where the cumulative forces are the greatest.

With present practices, when the string S parts or breaks in the manner set forth above, it is necessary that the portion of the string S and the tool T, left in the well, be removed. Such removal is carried out by disassembly of the string S, a stand at a time, where possible, or cutting the string up, and fishing out or retrieving the stands or cutup sections of tubing from the well. When such retrieving operation reaches that zone in the well Where the gravel is packed and is holding the string and tool, the retrieving operation requires Ibailing or circulating the undesired and trouble-causing gravel out of the well and becomes more complicated and costly.

It is well-known to those skilled in the art and will be readily apparent to those with limited knowledge in the art, that a retrieving or fishing operation such as referred to above is extremely costly and troublesome.

It is to be understood that the particular gravel packing operation referred to above, is only illustrative of one well servicing operation in which tools and related tubing strings can and do become stuck or frozen in wells and which results in breaking and separating of tubing strings and requires shing or retrieving operations similar to that operation referred to above.

A major diiculty or problem encountered in the well drilling and servicing art, where the above-noted type of adverse situation develops, is: it cannot be readily determined or controlled at which point a run-in string will break or part. Under present practices, when a tool becomes stuck in a well, the driller simply pulls on the run-in string until it parts and in doing so hopes that it will part in its lowermost portion. As noted above, due to the cumulative nature of the forces coming into play, such hopes or wishes of a driller are seldom granted.

In light of the above, it has lbeen determined that by provision of a suitable and proper releasing means, in the lower end portion of a run-in string, parting of the string at the lower end portion thereof, when that portion of the string and a related tool become stuck or frozen in a well, can be assured and that undesired breaking and parting of the string a substantial distance above the bottom of the well can be prevented.

By providing such a releasing means, the necessity of fishing or retrieving is not eliminated, but is effectively controlled and the possible extent of such operaionls is maintained at predetermined minimal and tolerable eve s.

The releasing collar R that I provide and which is illustrated throughout the drawings is adapted to be engaged in a run-in string S, between adjacent tubing stands to become a part thereof. The collar R is such that it allows for free uninterrupted flow of uid through the string, allows for normal turning of the string and withstands those torsional forces to be encountered. Further, it is such that it will withstand limited predetermined tensile forces in and through the string and will yield and allow for separation or parting of the string when said tensile forces are exceeded.

The collar R is shown as including an upper male section U and a lower female section L. The upper male section U is an elongate vertically extending cylindrical part having a central longitudinal flow passage equal in diametric extent with the flow passage in the tubing stands making up the string S; an upper Ibox portion 21, a central internally threaded upwardly opening box 22 in said `box portion threadedly receiving a pin 23 on the lower end of that stand of tubing 24 related to the upper end of the collar, upper and lower

central portions

25 and 26 and a lower portion 27. The upper central portion 24 is less in diametric extent than the upper box portion 21 and cooperates therewith to dene an annular stop shoulder 28, which shoulder is shown as being downwardly and inwardly inclined.

The portion 24 is of substantial longitudinal extent and is provided with threads 29 about its lower end portion. The threads 29 project radially outward from their related portion of the section U, that is, the minor diameter of the threads 29 is equal or greater than the outside diameter of the portion 25 of the section U.

The lower central portion 26 of the section U is less in diametric extent than the upper central portion 25 and joins the lower externally threaded end portion of the portion 25 to define a downwardly disposed annular stop shoulder 30. The portion 26 is of considerable longitudinal extent and is provided, in its upper portion with at least one and preferably two or more axially spaced radially outwardly opening shear pin receiving grooves 31.

The lower portion of the lower central portion 26 of the section U is provided with a plurality (three) of circumferentially spaced, elongate, longitudinally extending, radially outwardly disposed flats 32, which flats form a part of a modified spline construction for establishing torsional drive means between the sections U and L.

In practice, the flats 32 can extend laterally uninterrupted to converge with the outer cylindrical surface of the portion 26 of the section U or can, as illustrated in FIG. 7 of the drawings, be in the nature of very shallow and very wide longitudinally extending flat bottomed grooves in the exterior of the section U, and such that they dene, in addition to the outwardly disposed ats 32, laterally spaced, laterally inwardly disposed opposing shoulders 33, at each side of the flats. The lower end portion 27 of the section U is less in diametric extent than the lower central portion 26 and continues or extends downwardly therefrom. The portion 27 is of reduced diameter to facilitate establishment of the flats 32 and is such that the plane of the ats are substantially tangential with the exterior of said portion 27. The portion 27 terminates at a at downwardly disposed bottom end 34 and is provided with a plurality of axially spaced, radially outwardly opening sealing ring receiving grooves 35 throughout its longitudinal extent.

From the foregoing, it will be apparent that the upper section of my collar R is an extremely simple, easy and economical to manufacture part and is such that it lends itself to being made extremely rugged and durable.

The lower female section L of my collar R is an elongate, cylindrical, vertically extending part having a lower pin portion 40l with a central longitudinal ow passage 41, a central portion 42 and an upper portion 43.

The lower pin portion 40 is externally threaded and is adapted to be engaged in an internally threaded box 44 in the upper end of a related tool or stand of drill pipe 45 occurring below the collar R.

The flow passage 41 is the same in diametric extent as the ow passage 20 in the upper section U.

The central portion 42 corresponds in outside diameter with the box portion 21 of the section U and is of considerable longitudinal extent.

The upper portion 43 is less in diametric extent than the central portion 42 and is equal or slightly greater in diametric extent than the major diameter of the threads 29 on the upper central portion 25 of the section U. The portion 43 defines an annular, upwardly disposed stop shoulder 46. The upper end portion 43 defines a flat, axially upwardly disposed upper end 47 on the section L.

The section L is provided with a first, enlarged, upper bore 50 corresponding in diameter and in longitudinal extent with and slidably receives the lower central portion 26 of the upper section U, and a lower, secondary bore 51 continuing downwardly from the upper primary bore 50 corresponding in diametric and longitudinal extent with and slidably receiving the portion 27 of the section U.

The upper portion 43 of the section L is slightly greater in longitudinal extent than that portion of the lower central portion 26 of the section U in which the shear pin grooves 31 occur and normally overlies the shear pin grooves. The portion 43 is provided with a number of axially spaced, annular rows of circumferentially spaced, axially extending shear pin-receiving openings 55, equal in number with the number of grooves 31 in the section U and in common radial planes with the grooves 31 so that the inner ends of the openings 55 are in register and communicate with the grooves 3.1.

The openings 55 of each row of openings are circumferentially offset from the openings in the other row or rows of openings 55 so that the several openings 55 of the several rows of openings are circumferentially offset from each other and none of said openings are in vertical alignment with respect to the longitudinal axis of the construction.

The upper portion of the central portion 42 of the section L is provided with a plurality (three) of elongate, longitudinally extending, radially inwardly and outwardly opening slots 56 corresponding in circumferential placement and longitudinal extent with the ats 32 on the lower central portion 26 of the section U and in which elongated flat engaging keys or blocks 57 are arranged and The blocks 57 are equal or slightly less in lateral extent than the flats 32 and have at, radially inwardly disposed bearing surfaces 58 which establish at, sliding bearing engagement on related ats 32 of the section U, when the construction is assembled and as clearly illustrated in the drawings.

The blocks 57 are fixed in the openings 56 by welding 58.

In addition to the foregoing, the construction we provide includes sealing rings, such as O-rings, 59 engaged in the ring grooves 35 in the section U to normally seal in the lower bore of the section L; shear pins 60 in all or a predetermined number less than all of the openings 55 in the section L and entering the grooves 31 in the sectlon U, and a shear pin retaining sleeve carried by the section U and engaging the section L and the pins 60 carried thereby.

The shear pins 60 are simple, cylindrical, elongate metal shear pins corresponding in diametric extent with the diameter of the openings 55 and the lateral extent of the grooves 31 and corresponding in longitudinal extent with the combined longitudinal extent of the openings 55 and depth of the grooves 31. The pins 60 are slidably engaged in and through the openings, from the exterior of the section L and into engagement in the grooves 31.

The retaining sleeve 70 is an elongate sleeve corresponding in longitudinal extent with the upper central portion 25 of the section U and corresponds in inside diametric extent with the outside diameter of the upper portion 43 of the section L. The Sleeve is provided with internal threads 71 in its lower portion to cooperatively engage the threads 29 on the section U.

With the structure and the relationship of parts thus provided, it will be apparent that the sleeve 70` can lbe shifted from a normal down position where it overlies the upper portion 42 of the section L and holds the shear pins captive in the openings 55 and grooves 31, to an up position, as shown in FIG. 3 of the drawings where the openings S and pins 60 are uncovered and accessible so as to facilitate easy and convenient engagement of the pins 60 in the construction.

When the sleeve 70 is in its normal or down position, it is held and retained in that position adjacent the shoulder 46 by the threads 29-71.

It is to be noted that the seal established between the sections U and L by the sealing rings 59 and which prevents leakage of drilling uid from within the structure (in the passable fluid course between the sections) occurs downstream of the slots 56 in which the blocks 57 are arranged, downstream of the shear pin openings 5S and downstream of the sleeve 70. Accordingly, each and all of the parts and portions of the construction which might be adversely affected by the presence of drilling fluid or the iuid pressures within the construction, are downstream from the sealing means between the sections and are unaffected thereby.

lt is to be further noted that, rather than providing a single shear pin, I provide a multiplicity of shear pin receiving openings of a common size and in which any desired number of shear pins can be engaged. With such -a combination and relationship of parts, the tensile holding force afforded by the collar can be varied as circumstances require without modifying the construction or without having to maintain a supply of shear pins of different strength, which would be required if a single shear pin construction was provided and the holding strength of the construction had to be changed.

Another very important feature found in the provision of a multiplicity of shear pins resides in the fact that the shearing forces are divided up and distributed about the tool at a multiplicity of different points and are not sufficient at any one point to cause collapsing, tearing or scarring of the collar sections, as would be the case in a single shear pin construction.

Circumferential spacing of the shear pin opening in each annular row of openings from the openings in adjacent rows of openings further enhances the abovenoted features of dividing and distribution of forces.

In operation, the structure R is assembled and arranged in the string of tubing S in the manner illustrated in FIG. 2 of the drawings.

When and if excessive tension is applied to the string, the upper section U shifts upwardly relative to the lower section L, shearing the pins 60 and allowing for free axial separation of the sections and the portion of the string S occurring above and below the collar.

Following such release of the collar, the upper section U, with its directly related portion of the string S, is removed or pulled from the well in a conventional manner and the lower section L and its directly related portion of the string S and/or tool can be freed for easy removal by backscuttling, hailing or otherwise removing the gravel, or the like, which freezes or holds it in the well and then pulling it from the well. lf necessary, the portion of the string left in the well can be' cut up and fished from the well.

In either event, the location of the break and the amount of tubing left in the well is predetermined and so that the extent of the retrieving and/or fishing operation, which must be performed, is predetermined and maintained to tolerable and economically feasible levels.

In FIGS. 8, 9 and 10 of the drawings, I illustrate a modified form of the invention, wherein a captive ring with circumferentially spaced shear pin receiving openings 101 is engaged in the groove 31 in the upper part of the lower central portion 26 of the upper section Uf'. The ring 100 is rotatably engaged in the groove 31 and the openings 101 therein are spaced axially and circumferentially spaced to register with the shear pin opening 55 in the upper portion 43 of the section L.

In practice, the ring 100 is made up of two semicircular half sections, as shown in FIG. 9. The half sections are arranged in the `groove 31 and are suitably welded together, as at 102.

With the above structure, it will be apparent that the ring 100 is held captive in the groove 31 and is slidable therein for rotative movement relative to the upper section U.

The openings 55 in the section L' and the openings 101 in the ring 100 secure their related ends of the shear pins 60 snugly.

With the above construction, the radial inner end portions, as well as the radial outer end portions of the shear pins 60 are held captive and in such a manner that they are not permitted or allowed to distort, cold flow and prematurely tear when subjected to major, but less than yielding shearing forces.

In the rst form the invention, the inner end portions of the pins 60 are not held captive about their circumferential opposite sides in the grooves 31 and are free to cold flow, distort and tear in such a manner as to become weakened, if and when they are subjected to major, but less than designed yielding shearing forces.

The ring 100 in the modified form of the invention can be provided with any desired number of openings 101, which openings can be spaced axially and circumferentially of the rings in any predetermined pattern and to cooperate with the pattern of opening 55 in the section L.

The modified form of my invention illustrated and described above is the most desirable and preferred form and carrying out of the invention.

Having described only typical preferred forms and applications of my invention, I do not wish to be limited or restricted to the specific details herein Set forth, but wish to reserve to myself any modifications and/ or variations thereof that may appear to those skilled in the art.

Having described my invention, I claim:

1. A releasing collar engageable with and between upper and lower, adjacent, axially aligned stands of tubing in a fluid conducting tubing string including, an elongate, cylindrical, vertically extending, upper section with a central, longitudinal ow passage, upper connecting means at its upper end to connect with the upper stand of tubing, threads about the exterior of the section and spaced above the lower end thereof, an annular, radially outwardly opening channel spaced below the threads, a plurality of circumferentially spaced, elongate, axially extending, radially outwardly facing flats below the channel and annular, radially outwardly disposed sealing means about the exterior of the said upper section below said flats, an elongate cylindrical, vertically extending lower section with a central longitudinal ow passage, lower connecting means at its lower end to connect with the lower stand of tubing, a central bore slidably receiving the lower portion of the upper section and cooperatively engaged by said sealing means, a plurality of circumferentially spaced blocks with fiat, radially inwardly disposed bearing faces carried by the lower section and normally establishing flat, sliding bearing engagement on the flats, circumferentially spaced, radially extending shear pin openings in said lower section about the blocks and in a common radial plane with said channel, elongate radially extending shear pins engaged in the shear pin openings and extending radially inwardly into the channel and a retaining sleeve engaged with the threads on the upper section to be carried thereby and engaged about the lower section to overlie said openings and stop radial outward shifting of said shear pins.

2. A structure as set forth in claim 1 wherein the lower end portion of the upper section which carries the sealing means is less in diameter than the portion thereof in which said flats are established and the planes of said tlats are substantially tangential with the outer periphery of said lower end portion, said bore having upper and lower portions, said lower portion corresponding in axial and diametric extent with the lower portion of the lower end portion of the upper section and said upper po-rtion corresponding in diametric extent with the upper portion of the bore.

3. A structure as set forth in claim 1 wherein the lower end portion of the upper section which carries the sealing means is less in diameter than the portion thereof in which said ats are established and the planes of said flats are substantially tangential with the outer periphery of said lower end portion, said bore having upper and lower portions, said lower portion corresponding in axial and diametric extent with the lower portion of the lower end portion of the upper section and said upper portion corresponding in diametric extent with the upper portion of the bore, said blocks being engaged in radial slots in the lower section to engage the ats and xed in said slots by welding.

4. A structure as set forth in claim 1 wherein, the upper section has an upper end portion in which said upper connecting means is arranged, an elongate upper intermediate portion of reduced diameter and having said threads about the lower end portion thereof, a lower intermediate portion of less diametric extent than the upper intermediate portion and in which said channel and flats are established and a lower end portion which carries said sealing means, said bore having a lower portion corresponding in diametric and longitudinal extent with the lower end portion of the upper section, and an upper portion corresponding in diametric and longitudinal extent with the lower intermediate portion, the minor diameter of the threads being substantially equal to the diameter of the upper intermediate portion, the outside diameter of the upper end portion of the lower section being substantially equal to the major diameter of the threads, said retaining sleeve having an upper threaded portion to engage the threads and a lower skirt portion slidably engageable with and about the said upper portion of the lower section, said sleeve being substantially equal in longitudinal extent with the upper intermediate portion.

5. A structure as set forth in claim 1 wherein, the upper section has an upper end portion in which said upper connecting means is arranged, an elongate upper intermediate portion of reduced diameter and having said threads about the lower end portion thereof, a lower intermediate portion of less diametric extent than the upper intermediate portion and in which said channel and flats are established and a lower end portion which carries said sealing means, said bore having a lower portion corresponding in diametric and longitudinal extent with the lower end portion of the upper section, and an upper portion corresponding in diametric and longitudinal extent with the lower intermediate portion, the minor diameter of the threads being substantially equal to the diameter of the upper intermediate portion, the outside diameter of the upper end portion of the lower section being substantially equal to the major diameter of the threads, said retaining sleeve having an upper threaded portion to engage the threads and a lower skirt portion slidably engageable with and about the said upper portion of the lower section, said sleeve being substantially equal in longitudinal extent with the upper intermediate portion, said ats occurring on planes substantially tangential with the periphery of the lower end portion of the upper section whereby the lower end portion of the upper section can move freely by the blocks upon axial shifting of the sections.

6. A structure as set forth in claim 1 which includes radially outwardly opening channels in the upper section in axial spaced relationship with the first-mentioned channel and said lower section includes annular rows of circumferentially spaced radial openings in common planes with the channels, the openings in each row of openings being circumferentially offset from the openings in the other rows of openings, and shear pins engaged in selected openings in the rows of openings, said shear pins being of uniform shear and establishing uniform sliding bearing engagement in the holes and in the channels whereby the holding force afforded by the several pins is cumulative.

7. A structure as set forth in claim l wherein, the upper section has an upper end portion in which said upper connecting means is arranged, an elongate upper intermediate portion of reduced diameter and having said threads about the lower end portion thereof, -a lower intermediate portion of less diametric extent than the upper intermediate portion and in which said channel and llats are established and a lower end portion which carries said sealing means, said bore having a lower portion corresponding in diametric and longitudinal extent with the lower end portion of the upper section, and an upper portion corresponding in diametric and longitudinal extent with the lower intermediate portion, the minor diameter of the threads being substantially equal to the diameter of the upper intermediate portion, the ouside diameter of the upper end portion of the lower section being substantially equal to the major diameter of the threads, said retaining sleeve having an upper threaded portion to engage the threads and a lower skirt portion slidably engageable with and about the said upper portion of the lower section, said sleeve being substantially equal in longitudinal extent with the upper intermediate portion, said structure having radially outwardly opening channels in the upper section in axial spaced relationship with the firstmentioned channel and said lower section including annular rows of circumferentially spaced radial openings in a common plane with the channels, the openings in each row of openings being circumferentially offset from the openings in the other rows of openings, and shear pins engaged in selected openings in the rows of openings, said shear pins being of uniform shear and establishing uniform sliding bearing engagement in the holes and in the channels whereby the holding force afforded by the several pins is cumulative.

8. A structure as set forth in claim 1 wherein, said sealing means includes a plurality of axially spaced, radially outwardly opening grooves in the upper section and sealing rings engaged and sealing in the grooves and engaging and sealing in the bore.

9. A structure as set forth in claim 1 wherein, the upper section has an upper end portion in which said upper connecting means is arranged, an elongate upper intermediate portion of reduced diameter and having said threads about the lower end portion thereof, a lower intermediate portion of less diametric extent than the upper intermediate portion and in which said channel and flats are established and a lower end portion which carries said sealing means, said bore having a lower portion corresponding in diametric and longitudinal extent with the lower end portion of the upper section, and an upper portion corresponding in diametric and longitudinal extent with the lower intermediate portion, the minor diameter of the threads being substantially equal to the diameter of the upper intermediate portion, the outside diameter of the upper end portion of the lower section being substantially equal to the major diameter of the threads, said retaining sleeve having an upper threaded portion to engage the threads and a lower skirt portion slidably engageable with and about the said upper portion of the lower section, said sleeve being substantially equal in longitudinal extent with the upper intermediate portion, said structure having radially outwardly opening channels in the upper section in axial spaced relationship with the first-mentioned channel and said lower section including an annular row of circumferentially spaced radial openings in a common plane with each channel, the openings in each row of openings being circumferentially offset from the openings in the other rows of openings, and shear pins engaged in selected openings in the rows of openings, said shear pins being of uniform shear and establishing uniform sliding bearing engagement in the holes and in the channels whereby the holding force afforded by the several pins is cumulative, said sealing means including a plurality of axially spaced, radially outwardly opening grooves in the upper section and sealing rings engaged and sealing in the grooves and engaging and sealing in the bore.

10. A structure as set forth in claim 1 wherein, the upper section has an upper end portion in which said upper connecting means is arranged, an elongate upper intermediate portion of reduced diameter and having said threads about the lower end portion thereof, a lower intermediate portion of less diametric extent than the upper intermediate portion and in which said channel and flats are establishing and a lower end portion which carries said sealing means, said bore having a lower portion corresponding in diametric and longitudinal extent with the lower end portion of the upper section, and an upper portion corresponding in diametric and longitudinal extent with the lower intermediate portion, the minor diameter of the threads being substantially equal to the diameter of the upper intermediate portion, the outside diameter of the upper end portion of the lower section being substantially equal to the major diameter of the threads, said retaining sleeve having an upper threaded portion to engage the threads and a lower skirt portion slidably engageable with and about the said upper portion of the lower section, said sleeve being substantially equal in longitudinal extent with the upper intermediate portion, said flats occurring on planes tangential or spaced radially outward of the periphery of the lower end portion of the upper section whereby the lower end portion of the upper section can move freely by the blocks upon axial shifting of the section, said blocks being engaged in radial slots in the lower section to engage the ats and fixed in said slots by welding, said structure having radially outwardly opening channels in the upper section in axial spaced relationship with the first-mentioned channel and said lower section including annular rows of circumferentially spaced radial openings in common planes with the channels, the openings in each row of openings being circumferentially offset from the openings in the other rows of openings, and shear pins engaged in selected openings in the rows of openings, said shear pins being of uniform shear and establishing uniform sliding bearing engagement in the holes and in the channels whereby the holding force afforded by the several pins is cumulative, said sealing means including a plurality of axially spaced, radially outwardly openings grooves in the upper section and sealing rings engaged and sealing in the grooves and engaging and sealing in the bore.

11. A structure as set forth in claim 1 which includes an annular captive ring engaged in said channel for relative rotation therein and having openings registered with the openings in the lower section and slidably receiving the pins.

12. A structure as set forth in claim 1 wherein the lower end portion of the upper section which carries the sealing means is less in diameter than the portion thereof in which said ats are established and the planes of said flats are substantially tangential with the outer periphery of said lower end portion, said bore having upper and lower portions, said lower portion corresponding in axial and diametric extent with the lower portion of the lower end portion of the upper section and said upper portion corresponding in diametric extent with the upper portion of the bore, an annular captive ring engaged in said channel for relative rotation therein and having openings registered with the openings in the lower section and slidably receiving the pins.

13. A structure as set forth in claim 1 wherein the lower end portion of the upper section which carries the sealing means is less in diameter than the portion thereof in which said flats are established and the planes of said flats are substantially tangential with the outer periphery of said lower end portion, said bore having upper and lower portions, said lower portion corresponding in axial and diametric extent with the lower portion of the lower end portion of the upper section and said upper portion corresponding in diametric extent with the upper portion of the bore, said blocks being engaged in radial slots in the lower section to engage the ats and xedV in said slots by welding, an annular captive ring engaged in said channel for relative rotation therein and having openings registered with the openings in the lower section and slidably receiving the pins.

14. A structure as set forth in claim 1 wherein the upper section has an upper end portion in which said upper connecting means is arranged, an elongate upper intermediate portion of reduced diameter and having said threads about the lower end portion thereof, a lower intermediate portion of less diametric extent than the upper intermediate portion and in which said channel and flats are established and a lower end portion which carries said sealing means, said bore having a lower portion corresponding in diametric and longitudinal extent with the lower end portion of the upper section, and an upper portion corresponding in diametric and longitudinal extent with the lower intermediate portion, the minor diameter of the threads being substantially equal to the diameter of the upper intermediate portion, the outside diameter of the upper end portion of the lower section being substantially equal to the major diameter of the threads, said retaining sleeve having an upper threaded portion to engage the threads and a lower skirt portion slidably engageable with and about the said upper portion of the lower section, said sleeve being substantially equal in longitudinal extent with the upper intermediate portion, an annular captive ring engaged in said channel for relative rotation therein and having openings registered with the openings in the lower section and slidably receiving the pms.

15. A structure as set forth in claim 1 wherein, the upper section has an upper end portion in Iwhich said upper connecting means is arranged, an elongate upper intermediate portion of reduced diameter and having said threads about the lower end portion thereof, a lower intermediate portion of less diametric extent than the upper intermediate portion and in which said channel and flats are established and a lower end portion which carries said sealing means, said bore having a lower portion corresponding in diametric and longitudinal extent with the lower end portion of the upper section, and an upper portion corresponding in diametric and longitudinal extent with the lower intermediate portion, the minor diameter of the threads being substantially equal to the diameter of the upper intermediate portion, the outside diameter of the upper end portion of the lower section being substantially equal to the major diameter of the threads, said retaining sleeve having an upper threaded portion to engage the threads and a lower skirt portion slidably engageable with and about the said upper portion of the lower section, said sleeve being substantially equal in longitudinal extent with 'the upper intermediate portion, said ats occurring on planes substantially tangential with the periphery of the lower end portion of the upper section can move freely by the blocks upon axial shifting of the sections, an annular captive ring engaged in said channel for relative rotation therein and having openings registered with the openings in the lower section and slidably receiving the pins.

(References on following page) 13 14 References Cited FOREIGN PATENTS 121,739 3/1958 U.S.S.R.

UNITED STATES PATENTS Reed 285-2 REINALDO P. MACHADO, Primary Examiner Dardelet 287--125 Claypool et a1 285 3 5 D. W. AROLA, Asslstant Exammer Clark 285-2 U.S. C1. X.R.

Treese 285-2 285-330, 351, 286