US2748873A - Back pressure valve apparatus for automatically filling well conduit strings - Google Patents

Description

June 5, 1956 J. R. BAKER ET AL 2,748,873

BACK PRESSURE VALVE APPARATUS FOR AUTOMATICALLY FILLING WELL CONDUIT STRINGS 2 Sheets-Sheet 1 Filed April 27, 1953 tTZJHN R. BAMEQ, 34 (Yb/41v 1 Mass, v INVENTORS.

ATTQEA/EYS June 5, 1956 J. R. BAKER ET AL BACK PRESSURE VALVE APPARATUS FOR AUTOMATICALLY FILLING WELL CONDUIT STRINGS 2 SheetsSheet 2 Filed April 27, 1953 (fa/4N B. BAKEQ, rToH/v E Muss, JNVENTORS.

mom/M Ar roems Y6 United States Patent BACK PRESSURE VALVE APPARATUS FOR AUTO MATICALLY FILLINGWELL CONDUIT STRINGS John R. Baker, Pasadena, and John F. Muse, Montebello, Califl, assignorsto Baker Oil Tools, Inc., Los Angeles, Calif., acorporation of'California Application April 27, 1953, Serial No. 351,393

13 Claims. (6i. 166-225) The present invention relateswto subsurface well apparatus, and more particularly to apparatus for controlling the passage of fluid into a conduit string, such as a string of casing or drill pipe, as it is lowered in the well bore.

In lowering a. conduit string through the fluid in the well bore, it is desired-to have the well bore fluid flow automatically into the string. Unless controlled, the fluid may overflow the conduit string at its upper end, wetting the surface equipment and personnel, and thereby rendering the site unsafe andunclean for performance of operations. If the conduit string embodies a back pressure valve preventingupward flow of fluid therein, then such valve precludes the flow of'the well bore fluid into the conduit string, necessitating its filling from the top of the'hole, which is a time consuming and costly operation.

Accordingly, it is an object of the present invention to provide improved apparatus to be incorporated in the conduit string, which enables the string to-fill'automatically with the well bore fluid as the string is lowered in the well bore, but which precludes overflow of such fluid at the top of the conduit string.

Another object of the invention is to provide improved apparatus to be incorporated in the conduit stringthat enables the string to fill automatically with the well bore fluid, but which prevents the fluid from rising above a predetermined'level, which is lower than the fluidlevel in the well bore surrounding the conduit string.-

A further object of the invention is to provide improved apparatus of the character indicated, which is also'capable of functioning as a back pressure valve to-prevent upward flow of fluid in the conduit string after the conduit string has been lowered to a desireddepth in the well bore.

Yet a further. object of the invention is toprovide apparatus for controlling the filling of the conduit string, and of acting as a back pressure valve, which is of 'comparatively simple. and compact construction, and which is economical to manufacturev This invention possesses many other advantages, and has other objects which may. be made more. clearly apparent from a consideration of a form in which it may be embodied. This form is. shown in the. drawings accompanying and forming part. of the presentxspecification. It will now be;-described inzdetail, for the: purpose of illustrating the general principles of the. invention; but it is to be. understood that such detailed'description is not to be taken in a limiting sense, since the scope of the invention is best defined by the appended claims.

Referring to the drawings:

Figure 1 is a longitudinal section throughan apparatus embodying the invention, with. the valve mechanism disclosed in closed position;

Fig. 2 isan enlarged fragmentary, longitudinal. section, similar to Fig. 1, with the valve in open position. to permit upward flow of fluid through the apparatus;

Fig. 3 is a cross-section taken along. the.v line 33 on Fig. 2;

Fig.- 4 is a view similarrto Fig. 2, with the parts Of.th;.

2,748,873 Patented June 5, 1956 apparatus in still another position, to permit. downward How of fluid therethrough;

Fig. 5 is a View similar to Fig. 2, with theapparatus in a closed position to function as-aback pressure-valve;

Fig. 6 is-a cross-section taken along the line 66 on Fig. 4.

The apparatus disclosed in the drawings. has been specifically designed as a casing; shoew A to be attached to a string of easing B that is to be lowered throughthe fluid in the well bore. It is to be understood, however, that the apparatus. could be incorporated in an upper part of the casing string, in which event it wouldbe deemed. to be a casing collar, and, for that matter,. it would be incorporated in a string of' drill'pipe, or other conduit string, to be lowered in a well bore- As specifically disclosed, the. apparatus A includes an outer tubular member 10'having anupper threaded'box 11- threadedly secured" to the lower pin end 12 of an ad jacent casing, section B. The tubular memberis also provided with a cementitious plug 13 inseparably united thereto by ribs 14 on the cementitious plug disposed within longitudinally spaced, circumferentialgrooves 15 in the tubular member, the ribs being formed during the casting of the cement plug in the tubular memberi The lower' end' 16 of the plug is rounded, to provide a guiding nose for steering the casing stringpast obstructions or restrictions that might be encountered in the well'bore;

The-tubular member 10 and plug 13- have a central passage-17' extending completely therethrough, whichis' controlled by a valve mechanism that'automatically determines the passage of fluid upwardly into the conduit string B, as the latter is beinglowered in the well bore and which isalso so designed as. topreclude upward flow of fluid in the conduit string after it has been lowered to the desired depth in the well casing: If is preferred'that' the upward How of 'fluid in the'condui't string be controlled to prevent its exceeding a prede termined level, which-is lower than the level of the: fluid in the'well. bore externally of the conduit string;

The. above general mode of.operation:is'accornplished by the specific.apparatusrillustrated;intltetdrawingst- As shown, an elongate: housing. 18-'is.- cast. centrally within the cementitiousplug 13, the housing having ;longitudi:- nally. spacedrexterna'l circumferential grooves1=9:receiving the plug'ribs 2.0, to. inseparably unite the plugand housing'to one another. Thishousing is-provided=with a spider: 21 integral with-its outer wall.22,i the: spider including. a central hub23zsecured: to the outer wall byra plurality of circumferentially spaced generally radia-lribs 24, the spaces? 25 between the ribs-providing; passages for fluid throng-lithe apparatus. The cementitiousplug passage 17 below the housing-1&formsa continuation of. the. passage. 26 therethrough.

A valve-seat-member27 is .supported within =the1hu-b -23=. This member includes a stem 28 extending withinthe hub and havingsa head.29- at its .upper portion Initially, .the valveseat 27 issecuredtothe housing 18, but may bereleased therefromto partake: of longitudinalimovement therein inboth-directions. As disclosed, the stem1'27- is providedwith a peripheral .groove30-r receiving a' split,=.in herently expansiblering 31 extending; outwardly into .an enlarged bore.32 in. the hub23'. However, the bore 324s not sufli'cient infdiameter to. allowthe inherently expana sible ring tomove out of. the peripheral. sternv groovefill.

The split ring-31 is engageablewith a downwardly face ing shoulder 33' in the hub, the ring being maintained'in this position by one or more frangible. devices.3l4, insthe form' of shear pins, that extend. transverselyth'rough the hub 23' and into the ring;.31. Theseshear pinsfi ipres vent downward'movement .of' the valve seat 2.7T with respect' to the hub23, upwardmovement of the valve seat with respect to the hub also being prevented by the shear pins. However, the upward load on the shear pins 34 is relieved by engagement of the split ring 31 with the hub shoulder 33.

When the shear pins 34 are disrupted, in the manner described below, the valve seat 27 is moved downwardly to locate the expansible ring 31 within a further enlarged bore provided in the hub 23, which will allow the ring 31 to expand outwardly completely out of the peripheral stem groove 30, thereby freeing the stem 28 for longitudinal movement in both directions within the hub 23 and housing 18 of the apparatus. Downward move ment of the ring 31 in the enlarged bore 35 is limited and its loss therefrom prevented by a suitable stop device, in the form of a cap 36 threaded onto the lower end of the hub 23 and having an inwardly directed flange portion 37 on which the ring 31 will come to rest. This stop member 36 also functions to secure a retainer sleeve 38 in place, which encompasses the frangible pins 34 for the purpose of preventing their inadvertent displacement from their assembled position within the hub 23 and the split ring 31.

The periphery 39 of the head portion 29 of the valve member or seat 27 has a substantially lesser diameter than the inside diameter of the housing wall 40 to provide ample annular passage space for the flow of fluid therebetween. This head 29 is adapted to be engaged by another valve member to prevent passage of fluid therebetween, or the two parts may move longitudinally with respect to each other out of engagement to permit such passage of fluid. As disclosed, a valve head 41 is enclosed within a sealing member 42, made of rubber or rubberlike material. This sealing member is slidable along the cylindrical wall 40 of the housing above a stop shoulder 43 formed by an inwardly projecting flange portion of the housing 18. The sealing member 42 has an inner portion 44 adapted to sealingly engage the periphery 39 of the valve head 29. For the purpose of preventing leakage between the sealing member 42 and the cylindrical wall 40 of the housing, its lower portion may be formed as a downwardly directed lip seal 45. Similarly, the inner portion of the sealing member is formed as a lip 46 adapted to seal against the periphery 39 of the valve head. Thus, fluid from below acting on the sealing member 42 will tend to urge the inner and outer lips 46, against the periphery 39 of the valve head and the cylindrical wall 40, to prevent leakage therebetween.

The valve head is encased within the rubber or rubberlike member 42 and has an inner surface 47 tapering in an upward and inward direction which is covered by the rubber sealing material. This latter portion of the rubber seal is adapted to be engaged by a companion tapered seating surface 48 on the valve head member 29, in order to prevent fluid leakage therebetween. Thus, when the valve head member 29 is engaged by the rubber sealing material 42 on the upper valve head 41, there is a simultaneous engagement of the sealing material against the periphery 39 of the valve head 29, and also against its upper tapered surface 48.

The valve head 41 and the sealing material 42 are urged in a downward direction into engagement with the valve seat head 29 by a spring-like member, which is disclosed in the drawings as being provided by a rubber sleeve 49. This rubber sleeve 49 may be integral with the sealing material 42 disposed around the metallic valve head 41 itself. The sealing material also extends around the periphery of the head 41 and terminates in an upwardly directed lip seal 50 adapted to engage the wall 40 of the housing. The upper portion of the rubber spring 1 49 engages an outwardly directed flange 51 piloted within the upper end of the housing 18, and bearing against the upper portion of the cementitious plug 13. This flange 51 merges into a depending sleeve portion 52 disposed within the rubber spring 49. The upper end of the rubber 49 is communicable with the passage 17 through the plug 13 through one or a plurality of ports 53 extending through the flange 51.

The rubber sleeve 49 is generally cylindrical in shape, with its inner wall engaging the periphery of the depending sleeve 52 and its upper end engageable with the flange 51. When not compressed to any substantial extent, the outer surface 54 of the rubber sleeve is spaced inwardly away from the wall of the housing 18, providing the annular space 55 disclosed in Fig. 1. As shown in that figure, the rubber is under some compression, so as to exert a certain spring force maintaining the upper head 41 downwardly in engagement with the seat 27, and preventing thereby any fluid from flowing around the valve seat head 29 and up into the conduit string sections B above the shoe A. When the valve seat 27 is released and moves in a downward direction, as described hereinbelow, following disruption of the shear pins 34, then the valve head 41 and the rubber spring member 49 may slide downwardly until the lower portion of the seal 45 engages the housing flange shoulder 43.

The parts are at first disposed in the manner illustrated in Fig. 1, in which the rubber spring 49 is under some compression, to maintain the valve head 41 in firm sealing engagement with the upper portion 29 of the valve seat 27. In this position, the inherently expansible slip ring 31 is disposed within the stern groove 30, and the frangible pins 34 are intact. The casing shoe A is secured to an adjacent casing section B, and the casing string then lowered through the fluid in the well bore. The hydrostatic head of fluid externally of the casing string is acting over the lower area R of the valve head 41, tending to shift it in an upward direction against the compressive force exerted by the rubber spring 49, the area R being defined between the periphery 39 of the valve seat and the cylindrical wall 40 of the housing. The hydrostatic head of fluid increases as the conduit string B is lowered in the well bore until it overcomes the compressive force of the spring 49, shifting the valve head 41 upwardly against the force of this spring, foreshortening the latter, and expanding it outwardly toward the housing wall, as permitted by the initial annular clearance space 55 provided between the exterior of the rubber spring 49 and the housing wall. Before the rubber spring has been compressed fully into engagement with the housing wall, the valve head seal 46 has been shifted substantially above the valve seat 29. which then allows the fluid to flow around the valve seat 29, and on through the upper portion of the plug passage 17 into the conduit string sections thereabove (Fig. 2). As the fluid in the conduit string rises, the pressure of such fluid is acting on the rubber spring member 49 through the ports 53, until the combined forces of the internal hydrostatic fluid and the rubber spring are suflicient to counterbalance the external hydrostatic head, whereupon the rubber spring 49 is effective to shift the valve head 41 back to its initial closed position shown in Fig. 1, to close it.

From the foregoing description, it is evident that the level to which the well bore fluid can rise in the conduit string will always be less than the external fluid level by a height that corresponds to the compressive force exerted by the rubber spring 49. For that reason, the fluid will be prevented from overflowing the conduit string at the top of the hole, and will result in the maintenance of the working site in a dry and safe condition.

As the conduit string is lowered in the well bore in intermittent fashion, due to the necessity for stopping the descent and adding additional sections at the top of the well bore, the valve member 41 will be shifted intermittently in an upward direction to open position, and then downwardly to closed position as the fluid level within the conduit string rises.

has been lowered in the well arms-gees bore to the desired depth, the automatic filling device need no longer be used, and it is also desired to placethe apparatus in condition to allow downward pumping of fluid through the conduit string B and out through its shoe A. The conduit string is then filled with fluidto its upper end and pressure applied to the internal fluid. This pressure will act in a downward direction over the crosssectional area of the valve seat 27 and of the valve head member 41, and, if increased sufliciently, will eventually overcome the shear value of the pins 34, moving the valve seat 27 and the upper valve head 41 and spring member 49in a downward direction as a unit, the valve head 41 and spring 49 being limited in its descent within the housing by engagement of the seal' 45 with the housing shoulder 43. The valve seat, however, is able to continue its downward movement to the point limited by engagement of the valve head 29 with the spider ribs 24. Before the valve seat 27 engages the spider ribs, however, the ring 31 will be disposed in the enlarged hub bore 35, andwill inherently expand outwardly completely out of the-valve stem groove 30, thereby freeing itself fully from the valve stem 28 and allowing the latter to reciprocate in the hub 23.

As pointed out above, the downward movement of the valve seat member 27 is limited by engagement of its head 29 with the spider ribs 24. With the parts in this position, as shown in Fig. 4, fluid may be pumped in a downward direction through the casing string B, flowing through the depending sleeve 52 and the rubber spring member 49 and the head 41 securedthereto, and then passing around the upper valve seat head 29 and through the passages 25 between the ribs 24 for continued downward movement through the housing 18 and outof the casing shoe A. In the event that fluid tends to move in a reverse direction back into the conduit string, the velocity of such fluid will lift the valve seat 27 upwardly into engagement with the companion head 41 and the seal 42 on the latter, the entire assembly moving, up.- wardly as a unit until the rubber springmember 49 is again foreshortened and fully compressed between'the depending sleeve 52 and the wall of thehousing 18, which then precludes further upward movement of the valve seat 27, as shown in Fig. 5. Accordingly, the valve seat member 27 is now capable of functioning as a backv pressure valve, its ability to move upwardly to the extent indicated not being prevented by the ring 31 and en-. gagement of the latter with the hub shoulder 33, since the ring has been completely freed from-- thestem groove 30 and will remain in its lower position. resting upon the stop flange 37. In the event that fluidi is again to be pumped down and out of the conduit string,-the valveseat member 27 will again be shifted to the lower position shown in Fig. 4, the valve head 41 being prevented from following it to its full extent by engagement of'its lower seal 45 with the housing shoulder 43.

It is, accordingly, apparent that an apparatus has been provided which prevents the conduit string fromover flowing at the top of the hole, by maintaining the fluid level at a predetermined point lower than the fluid level around the conduit string. The diflerence in levels is determined by the force exerted by the rubber spring 49-, this spring preferably being made of rubber, rather than of the usual metallic helical variety, since it is desired to make all parts of readily drillable material, in the event it is later desired to drill out the entire internal portion of the casing shoe A. The releasable connection 31, 34 between the valve seat 27 and the hub 23 insures that the shear pins 34 will not prevent free reciprocation of the valve stem 28 within the hub, after the shear pins are disrupted. If the shear pins were attached directly to the stem 28, then disruption of the former might provide a burr, or other protuberance, that might catch on the valve stem and prevent its upward movement to its fully closed position, as shown in Fig. 5, which is indispensable to the functioning of the device as a back pressure valve. By virtue of the construction described, an automatic fill-up valveand'the-back'pressure valve are embodied in one mechanism, which enables the apparatus to be made comparatively short, thereby reducing the quantity of materials and labor required, and the cost of the equipment.

The inventors claim:

1. In well apparatus: a tubular member having means thereon for securing said member to a conduit string to be lowered in a well bore; a first valve member in said tubular member; a second valve member insaid tubular member and having a passage-therethrough; spring means engaging and urging said second valve'member downwardly into engagement with said first valve member to prevent fluid flow therebetween from a point below said first valve member into said passage; said second valve member being movable upwardly away from said first valve member to permit upward flow of fluid into said passage; and means releasably and rigidly attaching said first-valve memberto said tubular member to prevent downward movement of said first valve member within said tubular member, said releasable means being releasable to allow downward movement of said first valve member away from said second valve member to allow fluid flow therebetween.

2; In well apparatus: a tubular member having means thereon for securing saidmember to a conduit string to belowered in 'a well bore; a first valvemember in said tubular member; a second valve member in said tubular member and having a passage therethrough; spring means engaging and urging said second valve member d0wnwardly into engagement with said first valve member to prevent fluid flow therebetween from a point below said firstvalve member into said passage; and frangible means releasably and rigid-1y attaching said first valve'member to said tubular member to prevent downward movement of'said first valve member in said tubular member, said frangible means being disruptable hydraulically by fluid pressure acting-downwardly on said first valve member to enable said first valve member to move downwardly in said tubular member away from said second valve member;

3. In well apparatus: a tubular member having means thereon for securing said member to a conduit string to be lowered in a'well bore; a first valve member in said tubular member; a second valve member in said tubular member and having a passage therethrough; spring means engaging'and urging said second valve member downwardly into engagement with said first valve member to prevent fluid flow therebetween from a point below said first valve member into said passage; said second valve member being movable upwardly away from said first" valve member to permit upward flow of fluid into said passage; means releasably and rigidly attaching said first valve member to said tubular member to prevent downward movement of said' first valve member within said tubular member, said releasable means being released to allow downward movement of said first and second valve members; and stop means in said tubular member engageable with said second valve member to limit downward movement of said second valve member in said tubular member and allow said first valve member to move downwardly away from said second valve member.

4. In well apparatus: a tubular member having means thereon for securing said member to a conduit string to be lowered in a well bore; a first valve member having an upper head and a stern depending from said head; a second valve member in said tubular member and having a passage therethrough; spring means engaging and urging said second valve member downwardly into engagement with said head to prevent fluid flow therebetween from a point below said first valve member into said passage; said second valve member being movable upwardlyaway from saidfirst valve member to permit upward flow of fluid into said passage; and means releasably and rigidly attaching said stem to said tubular member to prevent downward movement of said first valve member in said tubular member, said releasable means being released to allow downward movement of said head away from said second valve member to allow fluid to flow therebetween.

5. In well apparatus: a tubular member having means thereon for securing said member to a conduit string to be lowered in a well bore; a first valve member having an upper head and a stem depending from said head; a second valve member in said tubular member; spring means engaging and urging said second valve member downwardly into engagement with said head to prevent fluid passage therebetween; said stem having a groove therein; and an inherently expansible ring in said groove; frangible means securing said ring to said tubular member and disruptable by fluid pressure acting downwardly on said head to enable downward movement of said first valve member away from said second valve member and also downward movement of said ring to a position permitting said ring to expand out of said groove.

6. In well apparatus: a tubular member having means thereon for securing said member to a conduit string to be lowered in a well bore; a first valve member having an upper head and a stem portion depending from said head; said tubular member having a guide portion receiving said stem portion; a second valve member in said tubular member; spring means engaging and urging said second valve member downwardly into engagement with said head to prevent fluid passage therebetween; one of said portions having a groove therein; a laterally movable ring in said groove; frangible means securing said ring to said other portion and being disruptable by fluid pressure acting downwardly on said head to enable downward movement of said first valve member away from said second valve member and also downward movement of said ring to a position permitting said ring to move laterally out of said groove.

7. In well apparatus: tubular means adapted to be secured in a conduit string to be lowered in a well bore; a first valve member in said tubular means; a second valve member in said tubular means; spring means engaging and urging said second valve member downwardly into engagement with said first valve member to prevent fluid passage therebetween; means releasably securing said first valve member to said tubular means to prevent upward and downward movement of said first valve member in said tubular means; said second valve member being movable upwardly against the force exerted by said spring means out of engagement with said first valve member prior to release of said releasable securing means; release of said releasable means allowing downward movement of said first valve member away from said second valve member and also upward movement of said first valve member in engagement with said second valve member against the force of said spring means.

8. In well apparatus as defined in claim 7; wherein said spring means comprises a rubber member adapted to be compressed between said tubular means and second valve member.

9. In well apparatus: tubular means adapted to be secured in a conduit string to be lowered in a well bore; a first valve member in said tubular means; a second valve member in said tubular means; spring means engaging and urging said second valve member downwardly into engagement with said first valve member to prevent fluid passage therebetween; means releasably securing said first valve member to said tubular means to prevent upward and downward movement of said first valve member in said tubular means; said second valve member being movable upwardly against the force exerted by said spring means out of engagement with said first valve member prior to release of said releasable securing means; release of said releasable means allowing downward movement of said first and second valve members; stop means in said tubular means engageable with said second valve member to limit downward movement of said second valve member in said tubular means and allow said first valve member to move downwardly away from said second valve member; release of said releasable means allowing upward movement of said first valve member while engaging said second valve member and with said second valve member moving upwardly against the force of said spring means.

10. In well apparatus: tubular means adapted to be secured in a conduit string to be lowered in a well bore; a first valve member in said tubular means; a second valve member in said tubular means; spring means engaging and urging said second valve member downwardly into engagement with said first valve member to prevent fluid passage therebetwecn; frangible means releasably securing said first valve member to said tubular means to prevent downward movement of said first valve member in said tubular means; said second valve member being movable upwardly against the force exerted by said spring means out of engagement with said first valve member prior to release of said frangible means; release of said frangible means allowing downward movement of said first and second valve members; stop means in said tubular means engageable with said second valve member to limit downward movement of said second valve member in said tubular means and allow said first valve member to move downwardly away from said second valve member; release of said frangible means also allowing upward movement of said first valve member while engaging said second valve member and with said second valve member moving upwardly against the force of said spring means.

11. In well apparatus: a tubular member having means thereon for securing said member to a conduit string to be lowered in a well bore; said tubular member having a valve housing secured therein; a first valve member movable longitudinally in said housing; a second valve member in said housing; spring means engaging and urging said second valve member downwardly into engagement with said first valve member to prevent fluid passage therebetween; frangible means releasably securing said first valve member to said housing to prevent upward and downward movement of said first valve member in said housing; said second valve member being movable upwardly against the force exerted by said spring means out of engagement with said first valve member prior to release of said frangible means; release of said frangible means allowing downward movement of said first and second valve members in said housing; said housing having a flange secured thereto engageable by said second valve member to limit downward movement of said second valve member in said housing and allow said first valve member to move downwardly away from said second valve member; release of said frangible means also allowing upward movement of said first valve member while engaging said second valve member and with said second valve member moving upwardly against the force of said spring means.

12. In well apparatus: a tubular member having means thereon for securing said member to a conduit string to be lowered in a well bore; a housing secured in said tubular member; said housing having a central hub therein secured to said housing by a plurality of circumferentially spaced radial ribs; a first valve member having an upper head and a stem depending from said head and extending into said hub; a second valve member in said housing; spring means engaging and urging said second valve member downwardly into engagement with said head to prevent fluid passage therebetween; frangible means releasably securing said stem to said hub to prevent upward and downward movement of said first valve member in said housing; said second valve member being movable upwardly against the force exerted by said spring means out of engagement with said head prior to release of said frangible means; release of said frangible means allowing downward movement of said first and second valve members in said housing; said housing having an inwardly directed flange engageable by said second valve member to limit downward movement of said second valve member in said housing and allow said head to move downwardly away from said second valve member; release of said frangible means also allowing upward movement of said first valve member while said head engages said second valve member and with said second valve member moving upwardly against the force of said spring means.

13. In well apparatus: a tubular member having means thereon for securing said member to a conduit string to be lowered in a well bore; a first valve member in said tubular member; a second valve member in said tubular member and having a passage therethrough; spring means engaging and urging said second valve member downwardly into engagement with said first valve member to prevent fluid flow therethrough from a point below said first valve member into said passage; and means releasably and rigidly attaching said first valve member to said tubular member to prevent both upward and downward movement of said first valve member within said tubular member, said second valve member being movable upwardly away from said first valve member to permit upward flow of fluid into said passage, said releasable means being releasable to allow downward movement of said first valve member away from said second valve member to allow fluid flow therebetween.

References Cited in the file of this patent UNITED STATES PATENTS 1,740,420 Friedman Dec. 17, 1929 2,155,601 Johnson Apr. 25, 1939 2,526,197 Cannon et a1. Oct. 17, 1950 2,661,763 Renick Dec. 8, 1953

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