US2223336A - Valve for gas lift pumping apparatus - Google Patents

Description

NOV- 26, 1940- G. A. HATFIELD I VALVE FoRjGAs LIFT PUMPING APPARATUS 2 Sheets-Sheet 1 Filed Nov. 17, 1937J 2 Sheets-Sheet 2 G. A. HATFIELD VALVE FOR GAS LIFT IUMPING APPARATUS Filed Nov. 17, 193'?v .Nom 26, 1940.

Patented Nov. 26, 1940 UNITED STATES `PATENT OFFICE VALVE FOR GAS LIFT PUMPING APPARATUS y Application November 17, 1937, Serial No. 175,015

14 Claims.

This invention relates to gas lift pumping apparatus for lifting a fluid such as oil from a well by the use of gas under pressure. This invention is more particularly directed to an improved type of intermitting gas lift device for lifting such uid which includes an intermitting valve positioned within the Well and controlled by fluid pressure from the surface of the well.

An object yof this invention is to provide an intermitting valve .adapted to be positioned at the bottom of a well and which is operatively sensitive to a single controllable variable.

Another object of this invention is to provide a sensitive remotely controlled intermitting valve for a gas lift which is loperative against a substantially constant resistance and which may be automatically and positively actuated by the degree of pressure of the operating gas substantially independently of the uid formation pressure within the well.

Another object of this invention is to provide a gas lift apparatus including a bottom hole intermitting Valve which is actuated by change in pressure in the actuating gas'supply conduit without the necessity ofemploying a supplementary control system in the well.

Another object of this invention is to provide a valve for a gas lift of positive operating characteristics and which is operative without chattering or floating in the gas stream.

Another object of this invention is to provide a cooperating mechanism for an intermitting bottom hole valve for a gas lift, which cooperative mechanism functions to nullify the objectionable increase or decrease of spring pressure on the valve incident to the change in the degree of compression of a controlling spring, and which control mechanism is operative to determine the spread between the opening and closing pressures of the valve.

Another object of this invention is to provide an intermittlng valve applicable for use in a gas lift system which acts as a gas saver to prevent the loss of operating gas during the interval between its discharge periods and which also is operable during these intervals to permit the well fluid to enter the lift mechanism unimpeded by the pressure of the operating or lifting gas.

Another object of this invention is to provide a gas lift apparatus including a starting valve which is operable not only as a starting valve, but also to clean the gas strainer and gas passage utilized in the regular gas intermittlng cycle.

Other objects and advantages of this invention it is believed will be apparent im. the following detailed description of a preferred embodiment thereof as illustrated in the accompanying drawings.

In the drawings:

Figure 1 is a diagrammatic elevation partly in longitudinal section of an intermitting gas lift device embodying my invention and illustrating the position of the valves during the filling.

Figure 2 is a view similar to Figure 1 showing the position of the valves during Ithe lifting or discharge.

Figure 3 is an enlarged sectional broken elevation of the gas lift apparatus embodying my invention illustrating the intermitting valve in its closed position.

Figure 4 is a sectional elevation View similar to Figure 3 on a reduced scale illustrating the intermitting valve in its open position.

Figure 5 is an end sectional view taken substantially on the line 5-5 of Figure 3.

Figure 6 is a sectional end view taken substantially on the line 6-6 of Figure 3.

Figure 7 is a sectional elevation of the starting valve embodied in my invention illustrating the same in closed position.

Figure 8 is a similar sectional elevation of the starting valve illustrating the same in its open position.

vFigure 9 is a diagrammatic view illustrating the operation of the starting valve mechanism embodied in my invention.

, In the preferred embodiment of my invention as illustrated in the accompanying drawings, I indicates a packing head or other supporting device which is positioned at the surface of the well. The packing head at its lower end is secured to the well casing 3, which extends downwardly into the well bore.

The tubing or discharge conduit 4 is supported in any conventional manner upon the packing head l and in the particular illustration given,- the tubing 4 is shown as supported by means of slips 5 carried by the gland 6 so that the weight of the tubing acts to compress the packing 'l to form a gas-tight seal between the packing head I and the tubing 4. 'I'he tubing 4 extends concentrically within the casing 3 and at its lower end carries the gas lift mechanism preferably at a position within the well below the normal oil level generally indicated` at A. At the extreme lower end of the gas lift device is the oil screen 9 and a standing valve I0.

Supported at the lower end of the tubing l is a cylindrical housing Il which houses and In order that the casing 3 may be utilized in the normal operation of the gas lift embodying my invention as the conduit through which the gas is conducted into the lift device, a packer I2 is provided lbetween the casing 3 and the housing II. 'Ihe packer I2 is preferably an expansible packer of any suitable or desirable construction which is well understood in this art.

In order to conduct the gas'from the casing 3 through the intermitting valve of my invention, a cross-over strainer I5 is provided between the housing II and the tubular member I3 of the intermitting gas valve. In Figures 1 and 2 the intermitting gas valve is diagrammatically 'illustrated at I8 within the tubular member I3.

In order to maintain the valve I8 operative against a substantially constant resistance independent of the pressure of the well or formation fluid within the well, an isolated and closed pressure chamber control device is provided which is of a construction and operation which will hereinafter be fully set forth.

In order -that the particular construction and operation of the gas lift embodying my invention may be more readily understood, the general operation of such device is illustrated in Figures 1 and 2. In Figure 1 the intermitting valve I8 is indicated as closed and the standing valve I 8 as open, Under this condition the oil from the well formation passes through the well screen of the casing 3 and up through the oil screen 9wby the standing valve I8 to ll the housing I I up to the oil level as indicated at A. Near the end of this interval of operation, the surface valve 16 opens admitting gas under pressure to the casing 3 above the packer I2 and against the upper surface of the valve I8 until sufiicient pressure of gas is accumulated above the valve I8 to overcome the constant resistance of the control means provided for the valve I8, at which time the valve I8 opens admitting the gas under pressure into the housing I I through windows 19 in the tubular member I3, at which time the standing valve i9 closes. The thus trapped quantity or slug of oil within the housing I I and tubing 4 is then forced from the well by the pressure of gas operating upwardly to lift the oil and gas out through the tubing 4. Closing of the surface valve 16 is timed to occur just before the slug reaches the surface, so that the actuating gas pressure in the casing 3 quickly bleeds down to closing pressure for the valve I8, as discharge occurs at the surface. After a predetermined period of time has elapsed, the surface valve 16 opens and again admits actuating gas into the casing 3 and the operation is repeated.

The valve I8 is a plunger valve as indicated at 2| and is adapted to control the flow of uid through the tubular member I3 and out through the dischargeport 19 of the tubular member I3. The plunger valve I8 is adapted to seat against a removable seat member 22.

Mounted within the gas passage provided by the tubular member I3 is a gas strainer 23, The plunger valve I8 is fitted to a cylindrical valve sleeve 8. r Y The plungervalve member I8 is threaded to za valve stem 2d upon which valve stem 28 an ad- L justable stop 25 is threaded. AV compression spring 26 is mounted upon the valve stem 28 to engage a collar 21 at its upper end and to engage a xed stop 28 at its lower end. Itwill be obvious that by adjusting the position of the stop 25 along thel valve stem 24 that the initial spring load of the spring 26, acting to hold the valve I8 against its seat 22, may be varied as desired.

'I'he tubular member I3 provides an enclosing housing for the intermitting valve, and at its lower end is secured to a housing 29 within which there is provided a constant pressure chamber 38 in which a spring loaded over-center device 3| is mounted to control, in connection with a bellows 32 and the compression spring 26, the opening and closing pressures for the valve I8. The bellows 32 is secured as indicated at 33 to the lower end of the stem 24. An extension 34 of the stem 24 is likewise secured at 35-to the stem 24 and extends through the bellows 32 concentrically within the housing 29 and is operatively connected with the over-center device 3 I.

The bellows 32 substantially balances out thel uid pressure exerted upon the underside of the valve I8 so that the operation of the valve I8 may be made independent of variations of the well or formation pressure within the well. The Ibellows 32 is at its lower end fixed and sealed against the stationary housing 29. The constant vpressure chamber 30 formed within the bellows and the housing 29 is sealed at its lower end by means of a sealingplug 35a. The chamber 30 is thus hermetically sealed so that the pressure Within the chamber remains constant disregarding the slight changes brought about by changes in temperature and the very slight pressure change caused by the relative movement of the upper end of the bellows` 32. thus provides a constant resistance for the valve I8 under all well conditions. This constant pressure chamber 30 extends from the upper end 33 of the bellows 32 down to the sealing plug 35a at the lower extremity of the housing 29. A porrial restriction to the passage of air.

The constant pressure chamber 39 by loose, guiding fits, these parts offer no mate- The timer valve 16 may be of the usual con- Wardly through the passages 18 in the plunger valve I8, and out into the housing II through` windows 19. 'Ihe passages 18 decrease the discharge port area and thereby limit the velocity of gas iiow through the valve I8 to a point where the velocity pressure drop through the gas conduits 3 and I3 will not be excessive. This construction also increases the effective area of the valve I8 under conditions of high gas velocity so as y.to keep it wide open until the pressure in the member I3 above it drops to closing pressure, and in addition assures the initial full opening of the valve I8. l.

In order to bring the plunger. Valve I8 quickly to its full open position and to compensate for the velocity pressure drop which occurswhen the gas begins to ow through the opening created by the opening of the valve I3, the eective area of the bellows 32 is'made slightly larger than the eiective area of the seat 22. 'This difference between effective areas is, however, maintained small enough so that the formation pressure of the well in the annulus within the tubular member I3 will not materially affect the opening pressure of the valve I8.

It will be obvious that while the constant pressure chamber and construction as hereinabove set forth produces the desired sensitivity for the valve I8, that there results upon opening movement of the valve I8 an increase in force tending to close the valve due to the compression of the spring 26. The longitudinal contraction or compression of the bellows 32, accompanying the opening movement of the valve, tends to compress the air in the chamber and acts similarly to the spring 26 to further increase the upward force on the plunger valve I8 as it moves downwardly to open position. This eect of the spring 28 and bellows 32 is contrary to the desired characteristics of valve sensitivity and I therefore provide a means to counteract this objectionable feature incident to the necessary movement of the bellows 32 and spring 26 and which means also provides for the desired diii'erence in degree of actuating gas pressure at opening and closing of the valve I8. This means I have heretofore referred to as the spring-loaded over-center device 3I. The spring-loaded over-center device 3| is mounted and housed within the constant pressure chamber 38.' 'I'he device 3| includes a pair of cam members 38 which are pivotally mounted on pins 39 carried by the cam holder 41. The cam holder 41 is secured upon the extension 34. The cams 38 are adapted to engage a pair of cam rollers 40, which cam rollers 4|) are pivotally mounted upon pins 4I of a cam roller carrier 42. The cam roller carrier 42 is resiliently supported to move longitudinally of the extension 34 by means of a spring 43, which spring 43 is at its opposite end engaged with an adjustable stop 44 carried by the extension 34.' The stop 44 is mounted upon a thrust bearing 45, the position of which thrust bearing 45 along the extension 34 is made adjustable by means of the nut 46 threaded to the extension 34. 'I'he cam roller carrier 42 is formed with parallel slots in which the cam ro1lers-48 are mounted. The cams 38 are mounted within corresponding slots formed in the `cam holder 41, which is mounted upon the extension 34.

A nut 88 threaded upon the lower end of the extension 34 and held in place by a pin 8| serves to clamp the sleeve 82, cam holder 41, stop member 52, and collar 55 in end-to-end relation against the shoulder 83 formed on the extension 34. Each of these parts so clamped is thereby secured in position upon the extension 34. Hence the cam holder 41 moves with the extension 34 and valve I8.

In order to actuate the cams 38, there is provided within the housingv 28 a stationary yoke 48 which carries an oi-'center actuating pin 43 which is positioned oli-center with respect to the axis of the extension 34.

The cams 38 are provided with notches 50 which form a sliding it with the pin 43 so that when gas pressure acts on the valve I8 to move it downwardly, that is, to open position, the extension 34 will move downwardly with the valve and relatively to the stationary yoke 48 so that the cams 38 will pivot about the pins 39 and fulcrum about the relatively stationary pins 49, and the lower ends of the cams 38 will thereby be caused to move over the crest of the cam rollers 40 from the position as indicated in Figure 3 when the valve I8 is closed to the position-as indicated in Figure 4 when the valve I8 is opened. 'I'he respective slots within which the cam members 38 and the cam rollers 48 are mounted maintain the cam rollers and cams in alignment.

It will be obvious from the foregoing that the action of this "over-center device 3| -is such as to require a greater force to start its motion than is required at any other point during its travel and therefore once the valve I8 starts to move, the resistance offered by the over-center device 3| immediately decreases and the valve I8 will move quickly either to its fully open or to its fully closed position by the action of spring 43. It will be obvious from inspection of Figures 3 and 4 that. as the cams 38 pass over the cam rollers 48 in passing from one position to the other, that the action of this over-center device is equal and opposite during its movements occasioned by both the opening and closing of the valve I8 and that the spring 43 exerts pressure in the same general direction to effect both the quick opening and the quick closing of the valve.

The adjustment provided for the spring 43 by the adjustment nut 46 enables a variation of the amount of force required for the extension 34 to move the cams 38 over center on the cam rollers 40. The upward force of the extension 34 required to move thev cams 38 from the position shown in Figure 4 to that shown in Figure 3 need not necessarily equal to the downward force required to move the cams 38 in the opposite direction. From Figures 3 and 4 it will be obvious that the shape of the lower ends of the cams 38 could be proportioned to require upward and downward forces of different magnitude.

The operation of this over-center device 3| has three principal functions, namely:

(1) To compensate for the force change'of the spring 26 incident to the movement of the valve I8;

(2) To compensate for a similar force change in the bellows` 32 incident to the movement of the valve I8, and

(3) To provide a further force requirement in addition to that for the compensations above set forth in order to determine the pressure dlierence of the operating gas between the opening and closing of the valve I8.

In the operation of this device it will be noted that the valve I8 opens when the resultant downward force of the gas pressure exceeds the upward force due to the combined eiect of the spring 26 and bellows 32' plus the resistance offered by the over-center device 3l. Similarly the valve I8 does not close until the resultant downward force of the gas pressure is less than the upward force due to the combined eect of the spring 26 and bellows 32 minusfthe resistance offered by the over-center device 3|.

In some wells having low bottom hole formation pressure and requiring a housing II large in diameter but short in length, the pressure in the well and around the valve I8 at the time of opening of the valve may be, for example, only oneiourth of 'the pressure of the actuating gas above the valve I8. Furthermore, the well fluid around the valve I8 may be very light and foamy so as to offer little resistance to the incoming actuating gas. It is to be understood that this condition may occur only at the time of the opening of the valve and does not exist once the fluid has left the housing |I and entered the tubing` 4, for by this time, due to the tubing 4 being of lesser capacity per foot than the housing II, the "s1ug oi. iluid being lifted will have lengthened out and will offer a back pressure in proper proportion to the pressure of the actuating gas.

It can thus be seen that in this instance the pressure and inertia characteristics of the iluid around the valve I8 may influence its action in opening.

While the combination of the over-center device 3| andthe slightly greater effective area of the bellows 32 over that of the valve seat 22 will usually effect instant full opening of the valve, yet in such an extreme case as above outlined, it is desired to provide for a supplementary opening action. Although the structure adapted to provide this supplementary action does not affect the predetermined degree of pressure at which the valve will open or close, it ,does aid in the instant full opening of the valve I8 n once it has started to open. In order to provide for this instant opening of the valve I8 under such adverse and unusual cases as above outlined, there is provided around the valve periphery a restriction 5I which, when the valve I8 starts to open, causes the actuating gas to work over an artificially increased effective diameter until the valve is substantially half way through its travel and can then complete its opening unaided. It will be obvious that the restriction 5I has suilicient passage area to allow for ordinary leakage past the valve `seat 22 without effect.

In order to permit of assembly and replacement of the valve seat 22, it is preferable to provide within the structure an emergency stop 52 which engages shoulder 53 to limit the upward Vmovement of the extension 34. Unlimited movement of the extension 34 would result in injury to the after the well has been allowed to stand idle for some time, or for the purpose of cleaning the cross-over strainer I5, I provide a starting valve 58.. In either of the cases above mentioned, the fluid Within the well may have filled both the tubing 4 and the annulus Within the casing 3 to a height considerably above that reached during normal operation. A further condition where high iluid head may occur in the well is when the application of the gas in one conduit transfers its Well fluid to the other conduit. Since the annulus within the casing 3 is of greater cross-sectional area than the tubing 4, adding the well fluid in the tubing 4 to that standing in the annulus Within the casing 3 raises the uid head a lesser amount than would be the case when the gas pressure is applied in the annulus within the casing 3 and the Well fluid contained therein is added to that in the tubing 4. In addition, When applying gas pressure within the tubing 4`and through the starting valve 58, it is not necessary to lift the well iluid from the chamber formed within the housing II below the strainer I5 as Would be the case if gas pressure were applied! as in the direction of normal operation. Hence it will be obvious that the initial slug can be raised to the surface with a minimum of gas un` der pressure.

The starting valve 58 includes a plug 59 which is threaded to the collar 60 at the upper end of the tubular member I3. The plug 59 is formed with a gas passage 6I. The upper end of the plug 59 is provided to form a guideway 62 for the stem 63 of a plunger valve 64. Secured to the plug 59 is a sleeve 65 which is closed at its upper end and formed below its upper end to provide a gas strainer 66. Mounted within the sleeve 65 is a valve seat 61 against which the plunger valve 64 seats. Interposed between the plug 59 and the valve plunger 64 is a spring 68 normally acting upwardly to maintain the plunger valve 64 upon its seat 61.

Referring to Figure 9, it will be seen that the openings 56, 51 of the packing head I are provided with valves 69 and 10 mounted within the gas conduits 1I, through which the gas is conducted to the openings 56 and 51. Conduits 12 extend upwardly and connect to a cross 13 mounted in the tubing 4. The tubing 4 is provided with a valve 14 above the cross 13. Mounted in the conduits 12 are control valves 15.

In this structure as thus described, when the well fluid has accumulated within the Well to an abnormal height, or when it is desired to clean the strainer I5, gas under pressure is admitted into the tubing 4 from its upper end by proper manipulation of the valves 69, 10, 14 and 15. 'Ihe pressure of this gas is sumcient to open the starting valve 58, thereby forcing the Well fluid above it into and through the cross-over strainer I5, and up through the annulus within the casing 3 and out the valved opening 51. As soon as the first slug of well fluid reaches the surface and passes out the outlet 51, valve connections at the head ofthe` well are reversed to admit the gas into the casing 3 through the valve 10, at which time the valve 58 closes and the regular intermitting cycle is commenced.

It will be obvious from the foregoingvthat by 'locating the starting valve 58 in the position indicated, that there is provided a method and means by which the gas strainer I5 may be cleaned as hereinabove set forth.

The expression over-center as utilized in the specication and in the claims designates a device which may be of the snap-action character and wherein the valve actuating element includes an operating or snap-action means which, when passing overor off-center is operable to mntain the actuating device in the off-center position. Thus'the over-center device is a device having the operating characteristics in this specic illustration asv dened in this speciication.

Having fully described my invention, it is to be understood that I do not wish to b'e limited to the details herein set forth, but my invention is of the full scope of the appendedclaims.

I claim:

l. A valve assembly of the character described comprising in combination a housing having an opening therein, a valve member mounted within the housing and adapted to close the opening, means Within the housing including a resilient means acting along a certain axis to yieldably urge said valve member toward its closed position upon the valve member being moved adjacent its closed position, said resilient means acting in the same direction along the same axis to maintain the valve member in its open position upon said valve member being moved adjacent its open position.

2. A valve assembly of the character described comprising in combination a housing having an opening therein, a valve member mounted within the housing and adapted to close the opening, means carried by the housing and adapted to urge the valve member toward the closed position, additional means within the housing including a spring means acting along a certain axis to yieldably urge said valve member toward its closed position upon the valve member being moved adjacent its closed position, said spring means acting in the same direction along the same axis to maintain the valve member in its open position upon said valve member being moved adjacent its open position.

3. A valve assembly of the character described comprising lin combination a housing having an opening therein, a valve member mounted within the housing and adapted to close said opening, said valve being movable to open position, an element adapted for oscillatory movement and being operatively connected with the valve member, means operatively associated with said oscillatory element including a resilient means acting along a certain axis, said resilient means being adapted to yieldably maintain said valve member in its closed position upon the valve member being moved to its closed position, said resilient means acting in the same direction along the same axis to yieldably maintain the valve member in its open position upon the valve member being moved to its open position.

4. In a device of the class described, the combination of a housing having an opening therein, a valve member mounted within the housing .and

adapted to close the opening, resilient means carried by the housing and adapted to urge the valve member toward the closed position, an element operatively connected with said valve member and adapted to have an oscillatory movement relative to a certain axis, additional means including a spring operatively associated with said element and acting yieldably to rotate it about said axis in one direction when the valve member is adjacent its closed position, said additional means also acting yieldably to rotate said element about saidaxis in a counter direction when the valve member is adjacent its open position, the axis of said spring and the direction of force applied by said spring remaining 'unchanged for all operative positions of said valve member.

5. A valve assembly'of the character described, comprising in combination a housing having a valve seat secured therein, a valve member mounted Within the housing and adapted to engage the seat to form a seal, spring means carried by the housing and adapted to urge the valve member toward said seat, 4additional means within the housing including a resilient means acting along a certain axis to yieldably urge said valve member into engagement with said seat upon the valve member being moved to its seatengaging position,` said resilient means acting along the same axis to maintain the valve membermin a retrieved position upon the valve member being retrieved from said seat.

6. In a pressure actuated valve of the class described, the combination of a housing having an opening therein, a valve member mounted Within the housing and adapted to close the opening, conduit means adapted to supply gas under pressure to said housing for urging said valve member to open position, a spring adapted to urge the valve member toward its closed position against the pressure of the gas, means within the housing adapted to yieldably urge said valve member toward its closed position upon the valve member being moved adjacent its closed position, and acting to maintainsaid valve member in its open position upon said valve member being moved adjacent its open position, said means also acting to counteract the force change of said spring incident to movement of the valve member from one position to the other, and said means further acting to control the diierence between the degree oi gas pressure at which the valve will open and the degree of gas pressure at which the valve will close.

7. A valve assembly of the character described, comprising in combination a stationary member having an opening provided therein for the passage of a fluid under pressure, a movable member mounted within the stationary member and adapted to close the opening, an expansible chamber operatively associated with said members, and means confined within said expansible chamber acting to yieldably urge said movable member toward its closed position upon the movable member being moved adjacent its closed position, said means also act/ing to yieldably urge said' movable member toward its open position upon the movable member being moved adjacent its open position.

8. A valve assembly of the character described, comprising in combination a stationary member having an opening therein; a movable member mounted within the stationary member and adapted to close the opening, means normally acting to urge said movable member toward its closed position, an expansible chamberoperatively associated with said members, and additional means conned within said expansible chamber acting to yieldably urge said movable member toward its closed position upon the movable member being moved adjacent to its closed position, said additional means also acting to yieldably urge said movable member toward its open position upon the movable member beingn means forming a substantially constant pressure chamber within said housing including a bellows disposed axially of said housing and having one end sealed with said housing and the other end sealed with said valve member, said valve member being adapted to move to its open position against the action of said resilient means upon the pressure dili'erential between said conduit and said chamber reaching a predetermined magnitude.

10. In a device of the class described, the combination of, a housing adapted to be positioned in a well bore, valve means in said housing comprising an opening and a valve member adapted to close the opening, conduit means communieating with said opening and adapted to contain a uid under pressure for urging said valve member to open position, means forming a substantially constant pressure chamber within said housing including a bellows disposed axially of saidhousing and having one end sealed with said housing and the other end sealed with said valve member, whereby said valve member may be moved from open position to closed position and Vvice versa -by the degree of pressure in said conduit. f

11. In a device of the class described, the combination of, a housing adapted to be positioned in a well bore, valve means in said housing comprising an opening and a valve member adapted l acting to yieldably urge said valve member toto close the opening, conduit vmeans communiward its closed position upon the valve member being moved adjacent its closed position, said means also acting to yieldably urge `said valve member toward its open position upon the valve memberA beingl moved adjacent its open position.

12. In a device of the class described, thecombination of, a housing adapted to be positioned in a well bore, a valve seat in said housing, a plunger slidably mounted axially of said housing and adapted to engage said seat to form a fluid seal, a depending extension secured to said plunger, conduit means communicating with said housing above said valve seat and .adapted to contain gas under pressure for urging said plunger to open position, means forming'a substantially constant pressure chamber within said housing below said valve seat, said means including a bellows disposed axially of said housing and having its lower end sealed with said housing and its upper end sealed with said extension, the effective diameter of the fluid seal being substantially equal to the eiective diameter of the bellows, whereby said valve plunger may be actuated by the degree of pressure in said conduit substantially independently of formation pressure within the well bore.

13. In a device of the class described, the combination of a housing having a valve seat therein, a valve slidably mounted within the housing and adapted to contact the' seat to form a seal, said valve having a valve stem attached thereto extending axially of the housing, means associated with the Valve stem and the housing adapted to resist axial movement of the valve in either direction, said means including a spring carried on said valve stem and extending axially of said housing.

14. In a device of the class described, the combination of a housing having a valve seat therein, a valve slidably mounted within the housing and adapted to contact the seat to form a seal,

said valve having a valve stem attached thereto extending axially of the housing, means associated with the valve stem and the housing adapted to resist movement of the valve away from said seat, said means including a cam pivotally secured with respect to said valve stem, cooperating elements on said cam `and said housing acting to impart pivotal movement to said cam upon axial movement of the valve and valve stem away from said seat, and means including a spring supported on said valve stem adapted to resist pivotal movement of the cam.

GEORGE A. HATFIELD.

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