|Publication number||US3405956 A|
|Publication date||Oct 15, 1968|
|Filing date||Mar 22, 1966|
|Priority date||Mar 22, 1966|
|Also published as||DE1299584B|
|Publication number||US 3405956 A, US 3405956A, US-A-3405956, US3405956 A, US3405956A|
|Inventors||Pierce Jr Elwood K|
|Original Assignee||Gray Tool Co|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (11), Referenced by (12), Classifications (6), Legal Events (1)|
|External Links: USPTO, USPTO Assignment, Espacenet|
Oct. 15, 1968 E. K. PIERCE, JR 3,405,956
APPARATUS FOR MECHANICALLY KEYING PARTS TO ONE ANOTHER Filed March 22, 1966 2 Sheets-Sheet 1 l I l /dj IN VEN TOR.
EA woao A, P/'ACAiJA.
Oct. 15, 1968 E. K. PIERCE, JR 3,405,956
APPARATUS FOR MECHANICALLY KEYING PARTS TO ONE ANOTHER Filed March 22, 1966 2 Sheets-Sheet 2 64) mm 68 I if l 24 if 54 INVENTOR.
52 waaoi zeag/e United States Patent 3,405,956 APPARATUS FOR MEEHANICALLY KEYING PARTS TO ONE ANOTHER Elwood K. Pierce, Jr., Houston, Tex., assignor to Gray Tool Company, Houston, Tex., a corporation of Texas Filed Mar. 22, 1966, Ser. No. 536,406 10 Claims. (Cl. 285-90) ABSTRACT OF THE DISCLOSURE An internally grooved, split-ring type hanger retainer which is self-aligned with respect to the hanger to be retained during the locking operation. The ring is initially received in a free, expanded condition in a peripheral groove in a casing head or the like. Means received in the casing head are operable exteriorly thereof to reversibly, forcibly contract the ring into locking engagement with a casing hanger or the like in order to restrain upward movement of the hanger to within a predetermined amount.
The present invention relates to mechanically keying parts to one another and more particularly to adjustable hanger retainer apparatus.
In petroleum well completion technology the use of hold-down means to prevent or at least restrain the upward movement of hung elements, such as casing, tubing and associated hangers with respect to the well head land/or adjacent next-outer casing, casing head hanger seats and the like, has become quite usual, primarily to ensure that seals between well head parts are not interrupted and also to forestall upward movement of hung elements due to surges of subterranean pressure incumbent on such elements.
One type of prior art hold-down means comprises locking screws which threadably extend through side apertures in a well head, each screw having a conical or wedge-like nose portion for engaging in a periphenal groove in a hanger or against a tapered surface on the upper end of the hanger to be held down. An example of this type is shown in the US. patent to Davidson, No. 2,507,246.
Particularly where a head assembly for receiving a plurality of casing and/or tubing hangers is used during the course of drilling and completion of a well, and locking screws of the type just referred to used to hold lower hangers down, the heavy drilling equipment attached to the top of the head tends to drive the locking screws through the tops of the hangers as the surface casing on which the head is mounted moves down under constant drilling vibration.
One means being successfully used to prevent such damage to hangers, yet provide positive hold-down means, is shown in my commonly assigned co-pending US. patent application, Ser. No. 342,440, now Patent No. 3,189,271 filed Jan. 4, 1964. In that instance, a snap ring is received in a peripheral groove in a hanger and held in contracted condition by a tool received axially within the well head bore, until such time as the hanger is properly positioned with respect to a seat in the head, whereupon the tool is manipulated to allow the snap ring to self-expand into locking engagement with an inner peripheral groove in the head.
For various reasons including facilitating the performance of certain work-over techniques, examination to locate the reason for malfunctions, adjustment to meet changed conditions and in temporarily or permanently abandoning wells, it is advantageous to provide for unlocking of such hangers with respect to the heads in which they are received.
Accordingly, it is a primary object of the present in- 3,405,956 Patented Oct. 15, 1968 vention to provide hanger hold-down means having the bearing strength advantages of snap-ring type hold-down means, but which are easily adjustable exteriorly of the well-head both during and subsequent to completion of the Well.
A further object of the invention is the provision of an internally grooved, split-ring type hanger retainer which is self-aligned with respect to the hanger to be retained during the locking operation.
A more general object of the invention is to provide a hanger retainer of the type described which has broad applicability to provide, supplement or substitute for lock-down assemblies for the hanger assemblies shown in the following US. patents: Mueller, 2,157,964, May 9, 1939; Brown, 2,189,575, Feb. 6, 1940; Roye, 2,207,469, July 9, 1940; Yancey, 2,207,471, July 9, 1940; Lemley et al., 2,485,497, Oct. 18, 1949; Crain, 2,586,581, Sept. 18, 1951; Mueller et al., 2,624,413, Jan. '6, 1953; Watts et al., 2,751,235, June 19, 1956; Watts et al., 2,754,134, July 10, 1956; Watts et al., 3,001,803, Sept. 26, 1961; Watts et al., 3,051,513, Aug. 28, 1962, and in the Composite Catalogue of Oil Field Equipment and Services, 1966-67 Edition, Gulf Publishing 00., Houston, Tex., volume 2, page 2065, FIGURE 11; page 2074, FIGURES 35 and 36; page 2075, FIGURES 37 and 38; page 2080, FIG- URES 52 and 53; page 2081, FIGURES 54, 55 and 57; page 2085, FIGURE 63; page 2086, FIGURES 65, 66 and 67 and page 2087, FIGURE 68, these examples intended to be non-limitative illustrations of the scope of applicability of the present invention.
It is an object of the invention to provide an adjusta-ble hanger retainer assembly which includes a contractile ring, initially received in a free, expanded condition in a peripheral groove in a casing head or the like, means received in the casing head and operable exteriorly thereof to reversibly, forcibly contract the ring into locking engagement with a casing hanger or the like in order to restrain upward movement of the hanger to within a predetermined amount.
In a preferred embodiment, the invention provides an adjustable retainer assembly comprising: a first element having means defining a generally cylindrical bore therein; a second element having means defining a generally cylindrically curved surface along a portion of the exterior thereof, said second element portion being received within said bore generally coaxially therewith; means defining a radially inwardly opening peripheral groove in said first element opening into said bore; an elastically contractile expansible substantially C-shaped ring received in said peripheral groove, said groove having greater axial extent than said ring thereby providing for limited axial mobility of said ring with respect to said groove; first securement means defined on said second element cylindrically curved surface and second securement means defined on an inner peripheral surface of said ring, said first and second securement means being coopenatively engageable; said ring being constructed and arranged for mobility between a first position wherein said ring is of greater internal diameter and said first and second securement means are disengaged and a second position wherein said ring is of lesser internal diameter and said first and second securement means are engaged, and ring radially moving means supported on said second element and bearing against said ring, said ring being axially mobile substantially independent of restriction by said moving means; the first and second securement means each comprising threading; the axial extent of said groove being greater than the axial extent of said ring by an amount which is at least slightly greater than the pitch of said threading so that said coacting threads are in the full mating engagement in said 3 second position of said ring; the ring when free fro said moving means having said greater internal diameter, said ring radially moving means being operable to effect elastic forcible contraction of said ring; a radially directed tang on said ring adjacent one end thereof; and means defining a complementary radially directed recess in said first element coincident with said groove and having an axial extent at least equal to said axial extent of said groove, said tang being received in said recess.
These, as well as further objects of the invention, the principles and scope of applicability thereof, will become more clearly apparent during the course of the following detailed discussion related to the embodiments illustrated in'the annexed drawings.
In the drawings:
FIGURE 1 is a side elevation view, with adjacent parts removed, of a Well head employing two hanger retainers according to the present invention. Some well head elements, including the compact casing head casing hangers, parent tubing hanger, wedges and retainer rings are partly broken away to expose details that would otherwise be hidden from view. In the view, the ring compressor and wedge operator screws are shown extending parallel to the viewing plane, somewhat out of angular position, for clarity.
FIGURE 2 is an enlarged fragmentary sectional view taken substantially along line 2-2 of FIGURE 1;
FIGURE 3 is a top plan view of the retainer ring shown in FIGURES 1 and 2;
FIGURE 4 is a fragmentary longitudinal, sectional view of a head, retainer ring and hanger according to the present invention, the retainer ring being in the free, expanded condition thereof, resting in the head inner peripheral groove;
FIGURE 5 is a fragmentary longitudinal sectional view, similar to FIGURE 4, of the ring in a forcibly contracted, hanger retaining condition; and
FIGURE 6 is a fragmentary longitudinal sectional view, similar to FIGURE 5, of a modified embodiment.
In FIGURE 1, the unitary casing head 10 is shown flanged at 12, 14 for mounting on the upper ends of outer casing 16, 18, for instance by welding at 20. A longitudinal throughbore 22 is formed through the easing head and is provided with an upwardly facing, frustoconical annular seat 24 near the lower end thereof. In the embodiment shown, on two levels above the seat 24, the head 10 is provided with a plurality of radially directed side outlets 26 that communicate the throughbore 22 with the exterior of the head. Just below the two levels of side outlets, the head 10 is provided with radially directed annular protrusions 28 for mounting ring compressor screws. Preferably, several protrusions 28 are provided on each level, for instance three or more equi-angularly spaced from one another.
Above the upper level of protrusions 28, and in the same plane as the upper level of side outlets 26, the head 10 is shown provided with Wedge receiving ports 30, one of for instance four, being shown. The head 10 in the illustrated embodiment terminates in a radially directed annular flange 32 having vertical bolt holes 34 equi-angularly spaced around it to provide for the securement and sealing of a blowout preventor stack (not shown) to the head via bolts (not shown) and an A.P.I. ring received in the groove 36 during intermediate stages of the drilling of the well, and for mounting a tubing bonnet and various conventional surmounting Christmas tree parts during completion. As should be apparent other securement and sealing means than the bolted flange and A.P.I. ring just described could be substituted, the deflectable lip sealing ring and clamp assemblies of the US. patents to Watts 2,766,829, 2,766,998, 2,766,999, 3,181,901, 3,216,746 and 3,231,297 being particularly useful in such an environment.
As shown in FIGURE 1, the flange 32 has a plurality, for instance 16, equi-angularly spaced, radially directed threaded openings 38 therethrough for receiving means for locking a parent tubing hanger in place.
Having reference to FIGURES 1-5, it should be noticed that the protrusions 28 have bores 40 which intersect the head 10 throughbore at their radially inner ends and respectively terminate in a lower internal peripheral groove 42 and an upper internal peripheral groove 44. Each groove 42, 44 extends 360 degrees about the head throughbore in the embodiment shown and has a radially outwardly directed slot 46 whose purpose will be more fully described hereinafter. A split C ring 48, 50 is received in each groove 42, 44 by compressing the ring, placing it in the throughbore 22 and allowing it to expand. Preferably, the radial depth of the grooves 42, 44 and free internal diameter of the rings 48, 50 when positioned as shown in FIGURE 4, is such that the rings do not protrude so significantly into the full opening of the throughbore 22 that equipment can damage them, be damaged by them or become snagged by them. Each retainer ring 48, 50 at one end thereof, has an integral, radially outwardly directed tang 52 configured to fit in the slot 46 in its respective groove 42, 44 in order to prevent rotation of the ring and reduce the number of ring compressor screws effectively needed to force radial contraction of the rings 48, 50. It should now be noticed that the grooves 42, 44 are internally threaded at 54 and have a smooth radially outer surface 56.
The ring compressor screw receiving bores 40 are counterbored at 58 leading to the radially outer extents of the bores 40 and internally threaded at 60 adjacent the bore radially inner extent and at 62 adjacent the counter-bore radially outer extent. Each ring compressor screw 64 comprises an elongated rod having a substantially flat inner end 66, an enlarged axially short exteriorly threaded region 68 adjacent the end 66, a short region 70 of reduced diameter defining an annular radially inwardly facing shoulder 72, and non-circular means 74 near the radially outer end for receiving a screw turning tool. Each screw 64 is threadably advanceable and retractable in its bore 40 via interengagement at 60, 68 and supported and sealed in its bore 40 by hydraulic packing or the like 76 received between annular washerlike elements 78 that serve as packing retainers and bearings, the innermost abutting the shoulder 72 and shoulder 80 defined at the radially inner extent of the respective counterbore 58. The elements 76, 78 are retairgd by a packing gland nut 82 threadably received at After the head 10 has been mounted on the outer casings as shown in FIGURE 1, drilling to prepare for the next inner casing string 84 is conducted through the head 10 throughbore 22. When sufiicient hole has been made, the casing string 84 is made up and run int-o the hole. A casing hanger 86 is secured to the upper end of the last section for instance by circumferential welding at 83 and lowered into the head throughbore using a lowering nipple (not shown) removably secured to the hanger 86 internal threads 90. In the embodiment of FIGURES l-5; the hanger 86 has a downwardly facing, upwardly enlarging annular shoulder 92 by which it is supported on the casing head seat 24. Above the shoulder 92, the hanger 86 has a generally cylindrical exterior surface 94 peripherally grooved to receive hydraulic packing rings 96 which seal against the cylindrical bore 22. An integral, axially upwardly directed annular extension 98 of the hanger 86 is provided with exterior threads 100 complementary to the retainer ring internal threads, but of somewhat greater axial extent. Above the threads 100, the extension 98 is ported at 102 radially adjacent the lower level of side outlets 26 to provide communication through the side outlets 26 and ports 102 with the bore 184 of the casing string 84. The extension 98 is provided with a substantially fiat upper end 106. After the casing hanger 86 has been landed with respect to the head 10, the hanger external threads 100 are adjacent but radially spaced from the retainer ring 48 internal threads 54 as shown in FIGURE 4. Next the ring compressor screws 64 abutting the smooth rear face of the retainer ring 48 are threaded inwardly forcing radial contraction of the ring 48 to the condition depicted in FIGURE 5 wherein the threads 54 and 1% are interengaged. Preferably, damage to the threads 54 and 109 is prevented and proper engagement ensured by using coarse threading, for instance about one-half thread per inch and by making each retainer ring receiving groove 42, 44 of slightly greater height than the pitch of the threads. In addition, alignment is aided in the FIGURES 1-5 embodiment by cutting the threads 54, 190 in a non-spiral i.e. circumferential, annular fashion. By comparing FIG- URES 4 and 5, it should be apparent that these provisions insure self alignment of the retainer ring as it is being forcibly contracted. It should also be noticed that because the ring receiving groove 42 is of greateh axial extent than the ring 48 and because the ring 48 smooth radially outer surface is only abutted by the smooth noses of the ring compressor screws, the ring 48 can more axially to effect alignment during forced contraction thereof (compare FIGURES 4 and 5), and thereafter a limited amount of axial movement of the ring 48 casing string 84 and easing hanger 36 can take place, such movement being limited in axial extent to the magnitude of the difference between the axial height of the groove 42 and the axial height of the ring 48 since the ring upper and lower surfaces 107, 168 are partly radially coextensive with the groove 42 even when the ring is forcibly contracted to the FIGURE 5 position thereof.
In the embodiment shown in FIGURES 1-5, such limited axial movement does not disturb the sealing between tne hanger 86 and head throughbore 22 since this sealing is between cylindrical surfaces as described above.
After the casing string 84 and hanger 86 have been run and the ring 48 forcibly contracted, drilling through the casing string 84 bore is commenced in preparation for running the next inner casing. (The various casings can be cemented after being run using conventional techniques.) When sufficient hold has been made, the next inner casing string 169 is made up and run into the hole. A casing hanger 110 is secured to the upper end of the last section for instance by circumferential welding at 112 and lowered into the head throughbore 22 using a lowering bushing (not shown) removably secured to the hanger 113 internal threads at 114. In the embodiment of FIGURES 15, the hanger 110 has an annular, downwardly facing lower shoulder 116 by which it is supported on the upper end of the hanger 86 extension. The hanger 110 is provided with exterior threads 117, and hydraulic packing rings 120 substantially equivalent to the threads 100 and rings 96. Using the procedure outlined above, the retainer ring 58, which is substantially identical to the ring 48 is brought from a position corresponding to that shown in FIGURE 4 to one corresponding to that shown in FIGURE 5.
After conducting further conventional down-hole well completion operations that will be apparent to those skilled in petroleum well technology, the well head is further made up by installing a parent tubing hanger 118, the particular example shown being equipped for receiving two tubing hangers (not shown) side by side for supporting two tubin strings, for instance to allow production from separate zones in the well to be segregated as is well known in the art. The parent hanger 118 is shown supported on the fiat supporting surfaces 121 of wedges 122 of the type exhaustively described in my commonly assigned co-pending application Ser. No. 260,- 372, now Patent No. 3,248,132, filed Feb. 25, 1963 and is shown held down by conventional set screws received in a circumferential groove 124. Near the upper end of the head 10 throughbore 22, a flared sealing surface 126 is formed and against which the sealing ring possessing flared lip 128 of the parent hanger 118 seals. No substantial weight of the parent hanger 118 is borne by the 6 surface 126, almost the entire support being provided by the wedges 122 at 121. After the blowout preventer stack (not shown) has been removed from the upper end of the head 10, a conventional tubing bonnet can be secured to the head 10 upper end and usual Christmas tree elements emplaced.
If for any reason, it becomes desirable to free the hangers 86 and/ or it is only necessary to thread outwardly the respective ring compressor screws sufficiently to allow the respective ring 48, 50 to self expand into its groove 42, 44.
A modified embodiment is depicted in FIGURE 6 wherein the casing head 10' throughbore 22 primary sealing surface 130 is frusto-conical rather than cylindrically curved. Accordingly, it is necessary to hold the hanger 86' complementarily curved sealing surface 132 and seals 134 down against the sealing surface 130. This is accomplished by providing buttress threading 54', on the split retainer ring 48' and hanger 86 respectively. As the ring 48 is forced from a condition comparing to that of the ring in FIGURE 4 to one comparing to that of the ring in FIGURE 5, the ring 48' is forced to rise in its groove and if turned in sufiiciently will abut the groove upper surface a shown, the downward wedging action of buttress threads and the fact that the compressor screws positively prevent the ring from expanding so long as they are turned in ensures that the seal at 130434 will not be unintentionally disturbed. In other material respects the construction shown in FIGURE 6 is identical to that of FIGURES 15.
As With the FIGURES 1-5 embodiment wherein V threads 54, 100 are shown, the buttress threads 54, 100 can be spiralled as an alternative to being non-spiralled, circumferential as shown. Self-alignment of the threads 54, 100 and 54, 100 when the threads are of the spiral type can be facilitated by interposing a soft rubber ring between the bottom of the respective retainer ring and the lower surface of the respective groove in order to support the respective ring, when in a free, expanded condition, spaced axially intermediate its groove so that the ring can move either upwardly or downwardly in order to properly align with the complementary casing hanger grooves.
It should be apparent that the relative vertical sliding between .the ring compressor screw noses and the retainer ring radially outer surface which usually occurs as the screws are threaded in and the ring begins to self align with the casing hanger threading, does not necessitate that the screw noses not be secured in any manner to the ring. For nstance, the screw noses could be upset or enlarged relative to the shanks and the noses received in undercut keyways in the ring outer surface so as to allow relative vertical movement of the screws and rings as well as radial expansion and contraction of the ring. In addition, such provisions would adapt the adjustable ring retainer to being of the normally contracted forcibly expansible type, since threading the screws out would cause expansion of the ring. But it should be clear that the spareness of the preferred embodiments shown in the drawing represent clear manufacturing and operational advantages over such a modification since many machining steps are avoided and there is less difficulty and opportunity for erroneous procedure in installing the preferred rings and ring compressor screws.
From the discussion throughout this specification, it should be apparent that the invention also has application outside petroleum well completion technology, and that within the well completion field the adjustable hanger retainer is applicable, not only in locking casing hangers in place, but also in adjustably, terminably locking other Well head and down hole elements, for instance tubing hangers, parent tubing hangers, casing head bowl protectors, subs, test hangers, and the like in place, with or without provision for limited relative axial movement (compare FIG- URES 5 and 6).
In addition, it should now be apparent that the invention as disclosed hereinabove efiiciently accomplishes each of the objects of the invention and that the embodiments described clearly illustrate the principles of the invention. Because the embodiments can be considerably modified without departing from these principles or failing to accomplish these objects, the present invention should be understood as encompassing all such modifications as are within the spirit and scope of the following claims.
1. An adjustable retainer assembly comprising: a first element having means defining a generally cylindrical bore therein; a second element having means defining a generally cylindrically curved surface along a portion of the exterior thereof, said second element portion being received within said bore generally coaxially therewith; means defining a radially inwardly opening peripheral groove in said first element opening into said bore; an elastically contractile expansible substantially C-shaped ring received in said peripheral groove, said groove having greater axial extent than said ring thereby providing for limited axial mobility of said ring with respect to said groove; first securement means defined on said second element cylindrically curved surface and second securement means defined on an inner peripheral surface of said ring, said first and second securement means being c0operatively engageable; said ring being constructed and arranged for mobility between a first position wherein said ring is of greater internal diameter and said first and second securement means are disengaged and a second position wherein said ring is of lesser internal diameter and said first and second securement means are engaged, and ring radially moving means supported on said second element and bearing against said ring, said ring being axially mobile substantially independent of restriction by said moving means; the first and second securement means each comprising threading; the axial extent of said groove being greater than the axial extent of said ring by an amount which is at least slightly greater than the pitch of said threading so that said coacting threads are in the full mating engagement in said second position of said ring; the ring when free from said moving means having said greater internal diameter, said ring radially moving means being operable to effect elastic forcible contraction of said ring; a radially directed tang on said ring adjacent one end thereof; and means defining a complementary radially directed recess in said first element coincident with said groove and having an axial extent at least equal to said axial extent of said groove, said tang being received in said recess.
2. The assembly of claim 1 wherein the first element comprises a casing head and said second element comprises a casing hanger.
3. The assembly of claim 2 further comprising means defining an upwardly facing seat on said casing head within said bore; means defining a downwardly facing shoulder on said casing hanger, said shoulder abutting said seat thereby supporting said hanger on said head; and sealing means received between said casing head bore and said casing hanger cylindrically curved surface, said sealing means extending circumferentially of said casing head and easing hanger and providing a fluid tight seal therebetween.
4. The assembly of claim 3 wherein the first and second securement means each comprise buttress threads;
where-in said sealing means comprise means defining an 8 frusto-conically curved surface upwardly away from said casing head frusto-conically curved surface.
5. The assembly of claim 2 further comprising a casing string secured to and depending from said casing hanger; a second casing hanger received within said bore and supported on the first-mentioned casing hanger; a second casing string secured to and depending from said second casing hanger through said first casing hanger and into said first casing string; said second casing hanger having means defining a generally cylindrically curved surface along a portion of the exterior thereof, said second casing hanger portion being received within said bore generally coaxially therewith; means defining a second radially inwardly opening peripheral groove in the casing head opening into said bore; a second elastically contractile-expansible substantially C-shaped ring received in said second peripheral groove, said second groove having a greater axial extent than said second ring thereby providing for limited axial mobility of said second ring with respect to said groove; third securement means defined on said second casing hanger cylindrically curved surface and fourth securement means defined on an inner peripheral surface of said second ring, said third and fourth securement means being cooperatively engageable; said second ring being constructed and arranged for mobility between a first position wherein said second ring is of greater internal diameter and said third and fourth securement means are disengaged and a second position wherein said second ring is of lesser internal diameter and said third and fourth securement means are engaged; and second ring radially moving means supported on said casing head and bearing against said second ring, said second ring being axially mobile substantially independent of restriction by said second ring radially moving means.
6. The assembly of claim 1 wherein the threading is non-spiral, circumferential threading.
7. The assembly of claim 1 wherein the threading comprises spiral threads.
8. The assembly of claim 1 wherein the ring radially moving means comprises a plurality of radially directed radially inner ends thereof with said groove; and an ports through said first element communicating at the elongated element movably mounted in each of said ports for advancement and retraction therein.
9. The assembly of claim 8 wherein the elongated elements are threadably received in the respective ports and have outer ends which protrude exteriorly of said first element; turning tool receiving means being formed on said element outer ends.
10. The assembly of claim 3 wherein said casing head is mounted and supported on the upper end of a surface casing received in the earth whereby said ring is prevented from damaging said casing hanger during subsequent drilling operations which vibrate said surface casing due to the limited axial mobility of said ring.
References Cited UNITED STATES PATENTS 1,211,387 1/1917 Beck 285--34 1,899,922 3/1933 Black 28530S X 1,978,991 10/1934 Dailey et a1. 285-305 X 2,104,180 1/1938 Barker 285-321 2,438,1-07 3/1940 Babbitt 285-32l 2,994,381 8/ 1961 Brown 28534 X 3,168,337 2/1965 Johnson et al. 285- X 3,288,222 11/1966 Urbanosky 166--135 X 3,326,580 6/1967 Munier et al 285-321 X 3,071,188 1/1963 Raulins 285322 FOREIGN PATENTS 730,339 5/ 1955 Great Britain.
CARL W. TOMLIN, Primary Examiner.
D. W. AROLA, Assistant Examiner.
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|U.S. Classification||285/90, 285/321|
|International Classification||E21B33/03, E21B33/04|
|Sep 27, 1982||AS||Assignment|
Owner name: GRAY TOOL COMPANY, 7135 ARDMORE ST. HOUSTON, TEX.
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST.;ASSIGNOR:COMBUSTION ENGINEERING, INC.;REEL/FRAME:004051/0937
Effective date: 19820926