US2251290A

US2251290A - Bottom hole hydropneumatic power unit

Info

Publication number: US2251290A
Application number: US217173A
Authority: US
Inventors: Warren B Reed
Original assignee: Individual
Current assignee: Individual
Priority date: 1938-07-02
Filing date: 1938-07-02
Publication date: 1941-08-05
Anticipated expiration: 1958-08-05

Description

Aug. 5, 1941. w..B. REED BOTTOM HOLE HYDROPNEUMATIG POWER UNIT Fiied July 2. 1938 2 sheets-sheet 1 W. B. REED BOTTOM HOLE HYDROPNEUMATIC POWER UNIT Aug. 5, 1941.

Filed July 2, 1938 2 Sheets-Sheet 2 Warren @ed 3mm HMM MRM

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Patented lAug. 5, 1941 BOTTOM HOLE NT VOFFICE Warren B. Reed, New Orleans, La. Application July 2, 1938, Serial No. 217,173

Claims.

My invention relates to a means and method of raising liquid from deep wells, and pertains particularly to the operation of a reciprocating power unit suspended in a deep well, connected to an operating and adjacently located bottom hole pump of conventional design.

My means and method of operating same is adapted particularly to pumping oil wells although-it will be obviously applicable to the pumping of other liquids as well.

It is the object of my invention to provide an effective hydro-pneumatic means for reciprocating .a plunger power unit in a deep well in such manner as to eliminate the use of sucker rods from the surface down to the operating power unit and to coniine their use to the connection between the power unit and the bottom hole Dump.

I desire in lieu of a sucker rod string to provide a balanced liquid column in a closed hydraulic system as a medium to transmit pressure piston or plunger within the power unit in such manner as to raise and lower the same under hydro-pneumatic control from the surface.

It is an object of my invention to utilize an independently operated valve unit to periodically connect and release in sequence vfluid volumes under individual pressures thereby effecting a reciprocating movement of the balance fluid co1- umn toactuate the piston of the power unit and its adjacently attached pump.

It is an object of my invention to maintain in a closed hydro-pneumatic system the relative operating pressures of the interacting iiuid volumes by applying power operated pumping means to constantly return the fluid volume used per stroke, from a recovery reservoir to its initial reservoir, restoring thereby the initial volume and pressure.

It is a further object of the invention to recover in the closed hydro-pneumatic system of operation, a maximum portion of the energy expended in lifting the piston of the power unit by utilizing the expansive force of the compressed gas volume in the power unit cylinder to store energy in a recovery reservoir I further desire to provide a process of great flexibility wherein the variation of the length of stroke-the speed ofthe piston plunger and the number of strokes per minute may be changed at will and imposed by a. long rod string.

It is a general object oi my invention to provide means to operate a deep well pump by connecting thereto a reciprocating power unit oper-v ating through a closed hydro-pneumatic system with energy supplied by a power driven pump,

and 'operatively controlled by a power driven value unit resulting in Vnovel iiexibllity and important economies.

In Fig. 1 is shown a sideelevation of the apparatus atV the upper `end of the well, certain parts being broken away for greater clearness.

Fig. 2 is a top plan view of the power installa` tion shown in Fig. 1, the valve member being shown in section.

Figs. 3 and 4 are longitudinal sections of the power unit apparatus in the well connected to conventional oil pump below, Fig. 3 showing the piston in one position and Fig. 4 in the other.

Fig. 5 is-a broken longitudinal section of the upper end of the power unit in the well and showing the provision of air passages in the cylinder head. y

'I'his application is a modiiication of the structure shown in my copending application serial No, 202,440, led April 16th, 1938, wherein the power cylinder is on the surface as distinguished from the present arrangement wherein a somewhat different ylinder is disposed in the well casing.

Referring to the drawings herewith, I have shown a. well in which the walls thereof are sustained in position by the usual well casing I. The lower endof this well stood as being equipped in the usual manner.

increased, without the limitations.`

As this casing is to be used as the oil string, the upper end has a casing head 2 thereon provided with a lateral outlet 2a whereby the liquid being pumped may flow from the casing.

' 'I'he tubing 3 is extended above the casing with which it has a fluid seal and extends downwardly into the well for connection at its lower end with my power operating means. This power unit operating means includes a head or bushing I. to which the rtubing'is connected, said head having an outer housing 5 connected thereon, said housing being also connected atits lower end to a lower head or bushing 4'.

'I'he upper head 4 has an opening therein forming an extension of the tubing, said opening being indicated at 3'. The lower end of said opening 3' is closed by a plug 6. Above the plug are a plurality of outwardly inclined passages 1 leading 'to the space ll within the housing 5.

Within the housing 5 and connected with the plug 4 in position spaced from the housing is Said cylinder is divided into upper and lower sections by means of a stop member 9. Said stop member -has a central axial passage therethrough and a downwardly projecting flange I0 is formed thereon adjacent said passage. The lower end of this cylinder is conof connection lateral openings Il, which lead to the space I I. between the cylinder and the housing. The upper end of thehead I' has a cushcasing may be underioning recess |2 therein to co-operate with the piston which works in said cylinder.

The piston is formed of one or more membersV as I3 and I5, with or without variable space I8 between, secured to the pump rod and fitting closely within the cylinder. I place a small quantity of oil above the piston as shown at I2' for lubrication and to effect a better seal as well as to provide a medium for an hydraulic cushion when the piston extension I3 enters the flange extension III of 'the stop member. The lower piston member I5 has a downwardly extending hub I3 thereon which fits within the recess l2 in the upper end of the cylinder head 4'. The piston rod I4 extends downwardly through the lower head 4 and has a uid tight seal therewith through means of the stumng box a.

Connected with the lower end of the head 4' is the oil pump tubing 2|, said tubingy being provided adjacent its upper end with perforations 2|' through which fluid being pumped may flow into the space within the casing above the packer I9. Within this tubing 2| is a reciprocating oil pump 20 of conventional design, the plunger thereof being attached by a determined length of rod or rods to the piston rod I4 of the power unit. It is intended that where the casing I in the lower end of the well is of sumcient diameter, the assembly of the power unit, oil tubing, packer, and oll pump with rod attachment to the piston rod, be as compact as is feasible. But, when the lower casing or oil string is-of too small a diameter to admit the power unit, said power unit may be suspended higher up in the larger size casing and the oil tubing 2| with packer I9 reciprocating oil pump 20 and sucker rod connection to piston rod |4 be extended to the desired pumping depth.'

It is to be understood that the pressure fluid employed is an incompressible liquid and under ordinary circumstances a good grade of non-gaseous oil will be employed.

Said oil will fill the power unit. The tubing 3 with pipe, valve unit, and connections leading to the two tanks and 2B and connections between them through power pump 4| form a closed fluid filled system.

When the well is 'ready pump and power unit, the determined length of oil tubing 2| with packer I9, oil pump 20 and proper length of sucker rod will be suspended from top of the casing I preparatory to lowering into the hole. Connections are then made to the piston rod I4 and to the lower end of the power unit at 4'. This completed assembly will then be lowered and suspended on casing at the upper end of the power unit.

At this time a small quantity of lubricating oil I3 will be injected into the cylinder space through inlet passage 24 ln the headl 4 (Fig.'5). Following this, the cylinder space upperv and lower sections will be given their predetermined gas pressure through the passage 24 provided therefor in the head 4. This passage will close to prevent escape of the gas under pressure by means of a check valve at its bottom end supplemented by a plug in the top of the passage 24 to eectually seal the gas pressure in the cylinder. This gas pressure-will have forced the piston into its down position so that the entire cylinder is filled.

Oil is now introduced into space 3 filling passages 1 in head 4, space Il and openings Il until the housing space and passages from the botrcr its instalation or tom of the piston Il to the top of space 3 are completely filled.

Tubing 3 is now attached and the completed assembly is lowered by tubing 3 to the proper depth and the packer Il set.

Or, lf desired, the following procedure may be followed, the tubing 2| of determined length equipped with pump seat and with packer thereon, and perforations in the tubing above the packer may llrst be lowered into the well with a detachable device at its top (such as a Jay tool) and the packer set between the tubing and casing. The lowering means will then be detached and the tubing with set packer left in the well.

The power unit filled as above described with oil and gas under pressure and with the oil pump with the desired length of rod connected to the piston rod extending from head 4' may then be lowered into the well, the pump entering the oil tubing and seating and the lower end of the power unit, fitted with proper connection to fit the detachable connection on the ing, meets and connects therewith. This procedure has the advantage of being able to pull and remove the pump for whatever purpose without having to disturb and reset the packer between the tubing and well casing.

In either procedure, tubing 3 is now ready to be filled with the pressure liquid from the surface to the power unit. In order that the air or gas in the tubing may be eliminated, I employ a movable piston or go devil 23 which will precede the oil as it is pumped downwardly through the tubing 3. The air or gas in the tubing below said piston or go devil as it travels downward will be vented outwardly through the passage 24 shown in Fig, 5 and the piston 23 will finally seal on the plug 6 and close the passage 24'. There is an outwardly opening valve in this passage which will also prevent any fluid from entering from the outside. The oil filled tubing 3 above the piston or plug 23 is now ln contact with the oil in the lled power head to the bottom of pistonv I5 in the cylinder. At the upper end of tubing 3 connections are made with the oil filled pipes and connections of the surface operating apparatus, effecting a completely closed fluid system.

It is obvious that a reciprocating movement of the piston in the power unit will cause the same movement of the attached plunger'of the oil pump 20 to perform the pumping operation, and liquid thus pumped by said plunger will pass through the tubing 2| and openings 2|' to the interior of the casing or oil string above the packer I9 and will thus rise and flow outwardly at the surface through the lateral passage 2a.

Asvthe power piston I3 approaches the upper end of its stroke the flange I0 upon the stop member 9 will engage within the upper oil filled end of the piston and serve to limit the travel of the piston and hydraulically cushioning the stop. It will be understood that the gas pressure of determined amount within the cylinder above the piston will be compressed as the piston rises,`

and will be such as to exert a back pressure against the piston which will tend to stop the piston before it engages the stop member 3, said stop, however, will hydraulically cushion the stroke of the piston in case it travels above its calculated distance.

'When the piston reaches the upper end of its stroke it will be held in that position temporarily in accordance with the operating structure top of the tub which will now be described.. after which the weight of the attached pump connection and the expansion of the compressed gas above the piston will drive it to the lower end of the stroke.

At the end of the down stroke. theoil filled re- /cess I2 in lower head 4' will receive the extension I8l of piston I5 to function as an hydraulic cushion should the back pressure from recovery tank 28 be insuiiicient to fully stop the descent of the piston. 'I'he piston will be held in this down stroke position until the next operating cycle begins. y

My surface apparatus includes a pair of tanks or containers 25 and 26. I'I'he tank 2l is called the power reservoir and the tank 26 the recovery reservoir. Each of said tanks has its interior partly filled with the operating liquid, said liquid being indicated as 21 in Fig. 1. The upper portion of each container is filled with gas or air'under a determined individual pressure. Each tank has a laterally extending pipe thereon controlled by means of a hand valve 28 to be used when charging the tanks with air or gas under pressure. From the power reservoir 25 a pipe 29 is extended toward the power unit for 'connection beyond the valve unit at 30 with the pipe 22 connecting with the tubing 3. A similar pipe 3| connects the reservoir 26 with said pipe 22. This pipe 22 may be only a few feet as when the installation is at the derrick side or it may be at any economic distance as in the case of central control.

In the two pipes 29 and 3| I have placed a valve unit including a housing 32 with a passage 33 connected with the pipe 3| and a similar passage 34 connected with the pipe 29. A valve member 35 of the rotating type extends across the housing 32 and has an opening 36 to be brought into registration with the passage 33 and an opening 31 to be brought into registration with the passage 34. These two openings 36 and 31 form two valves at right angles to each other so that when one valve is open the other will be closed. Said valve member 35 is shown with extended rod 38 which may be operated by a motor 39 through a gear reduction means 40. 'I'hrough this operating means the valve member is caused to rotate with a uniform, continuous and slow speed, adjustable at will, and it times and controls the number of strokes per minute of the power unit.

'I'he valve unit controls the power unit operation, its timing per stroke and number of strokes per minute, it is power driven and actuated independently of any other function of the process.

'Ihe valve uni-t is so operated that one valve opens and closes at a uniform speed with a closed interval of determined length before the other valve opens and then closes with the same uniformity, followed by a closedinterval. These closed intervals may be of the same length or the intervals may be varied by design of the valve opening so Ithat at the top of the stroke the interval may be short and at the bottom of the stroke it may have a longer period.

The particular valve unit shown is only one of many designs which may be used to control the pressure liquid as employed in my invention.

The valves may be slide valve type, piston valve, rotary valve, or other variation and the valves may be actuated by Varied power means without departing from the principles of my invention.

Beside the continuously operating valve unit I have placed two hand operating valves 29' and 3|' in the pipes 29 and 3| respectively. 'I'hese two valves are of the throttling type and are not only for the convenience of closing the pipe connections to the reservoir-s but primarily for the purpose of regulating at will the iiow of iluid therethrough.

The recovery reservoir and the power reservoir are connectedl to a power driven pump 4|.A An outlet pipe 42 from lthe recovery'reservoir 26 is connected to the inlet side or suction of said pump. In the pipe 42 is placed a check valve 43 allowing the passage of liquid i'n the direction of the arrow. Between the pump 4| and the power reservoir 25 is the pump discharge pipe 44 having therein a check valve 45 opening in the direction of the reservoir.

The pump 4|, of proper volume and pressure capacity, is shown operated from the power shaft 46 of the electric motor 41. Said motor is governed through a rheostat and control switch 48 operated by pressure from the power reservoir 25 through a connecting pipe 49. It will be understood that changing pressure in the reservoir 25 will regulate the motor speed withinset limits and will further actuate a switch in the control chamber 48 to start and stop the motor when the pressure rises above or falls below established limits. In this manner the amount of liquid pumped can be controlled. This type of regulator is part of the motor equipment and can be purchased in the market. If gas, gasoline or Diesel type 'engine be used as motive power the regulation thereof will be controlled by changing pressures in power reservoir 25 through means of diaphragm regulators.

A further regulation of the oil volume and consequent relative pressure in the two tanks is eifected through a pipe 53 connecting the two tanks below the oil levels therein. In connecting pipe 53 is placed a hand operated valvev54 to open or close the connection. Around, and bypassing, this valve 54 is a connecting pipe 55 having therein an automatic pressure regulating relief valve 56. Valve 54 may be opened to facilitate the passing of oil from one tank to the other, and when the relative quantities are adjusted valve 54 will be closed. The relief valve will be adjusted to operate at a determined pressure at which it will open and permit the flow of liquid from the power -tank to the lower pressure recovery tank, closing when the pressure in the power tank falls below the desired amount. With this means of control, the pump may continuously operate above the required capacity and the surplus be automatically returned to the recovery tank. Pressure gauges 52 and 52' are shown connected on each side of the relief valve 56 to indicate the pressures in the two tanks respectively.

vSupply of oil for the surface apparatus is introduced through the inlet pipe 50 having thereon a handoperatedvalve 5|. The closed,oillledsystem is without air pockets and is self contained and without losses therefrom except by accident, when additions can be made through valve 5 To introduce the individual pressure volumes into the power and recovery reservoirs, valves 29' land 3|' are closed and through valve 28 air or gas is injected into the power reservoir 25 of an initial pressure PI and confined therein by the uid volume This pressure P| is of such determined amount as to lift the piston in the power unit with its initial volume and pressure CI plus an amount to insure a determined velocity of upward piston travel with its weight of rod connections and its oil load on the attached pump plunger. This throttling the orifice, limiting and pressure PI will then be confined in tank between check valve 45, and the closed valve 28'.

In like manner an initial pressure RI is introduced into the recovery tank 25. This pressure is of such an amount as to equalize the expansion force of pressure C l on the down travel of piston, plus the net gravity pull due to the weight of the rods and oil plunger, plus an amount to cushion and stop the down travel of the piston at such point in the cylinder as may be desired. This pressure is confined from the closed valve 3|', the recovery reservoir 26 and pump 4l to check valve 45. A

In the power unit cylinder an initial pressure Cl is introduced before lowering into the Well, as has been described. This pressure is of such amount as to equalize the weight of the oil pressure column, plus an amount which when being compressed by the upstroke is sufficient to cushion and stop the piston at the length of stroke calculated. This pressure is exerted on top of piston l3-l5 and thereby extended to the oil in space Il, passages 1, oil column in tubing 3 to the valve unit and closed valves 29' and 3l'. These three determined individual air pressures are of such relation and difference that by operating the valve unit which puts them into consecutive motion and the power driven pump which continuously restores the volume and the pressure in the power reservoir the system functions as designed.

With the initial confined pneumatic pressures as described, the detail of a complete cycle will be as follows:

Valves 29 and 3|' being opened, a part revolution of valve member would open valve 31 (with valve 35 closed). The pressure PI of the power reservoir would then extend through the balanced oil pressure column in tubing 3 to the power unit, forcing the piston therein to its up position, lifting the load on the piston rod, (the weight of the rods and the oil load on the pump plunger), and compressing the initial air pressure Cl in the cylinder chamber 8 to a resulting increased pressure C2. During this upstroke a volume of oil V'l has filled the power unit cylinder from the head 4 to the piston in the up position.

The expansion by the transfer of this volume Vl from power reservoir to power unit cylinder has reduced the pressure of Pi to P2 and increased the pressure of Cl to C2 and the piston comes to rest when P2 and C2 are equal. The pressure P2 is now extended from the power reservoir through valve unit, pipe 22, tubing 3, to the piston in its up position in the power unit cylinder.

The valve unit 31 is then closed with the pressure P2 on the power reservoir side and the pressure C2 on the other side. A further movement of the valve member 35 opens valve 36 (valve 31 remains closed) and permits the down stroke actuated by the down pull of the net weight of the pump rod and the expanding pressure C2 to CI above the piston, forcing the oil volume Vl below the piston up through tubing 3 and pipe 22, valve 36, pipe 3i into the recovery reservoir 25 and compressing its initial pressure RI by the amount of oil VI to its increased pressure R2. This increasing compression of RI to R2 during the down progress of the piston tends to retard the down velocity of the piston and the pressure of R2 is so determined that the piston is air cushioned and stopped at a determined point, relieving or supplementing the hydraulic cushioning at the bottom of the stroke. At the end of 75 the down stroke the pressure CI equals R2 and extends from the piston through tubing 3 the valve unit into the recovery tank until valve 35 in valve unit is closed when this pressure R2 is separated. We then have the cylinder with its initial pressure CI balancing the oil column in tubing 3 and the recovery reservoir with its added volume Vl and increased pressure R2 power reservoir with reduced pressure P2 and the oil volume reduced by VI.

It is now the function of the power driven pump 4I to pump oil volume VI at pressure R2 from recovery reservoir into the power reservoir, returning to it the oil volume Vl to raise its pressure P2 back to the initial pressure Pl.

This detail analysis with the modification that the power driven pump action is continuous described one complete cycle.

The energy consumed, expressed in terms of horsepower, by the power driven pump would be represented by the formula, number of cycles or strokes times the gallons per stroke, times the difference in pounds pressure between P2 and R2 divided by 1714.

No. strokesX gals. per strokeX (P2- R2) 1714 -No. H. P.

It is obvious that the bottom hole power unit differs from the surface power unit, shown in my copending application, primarily by its being suspended in the well adjacent the oil pump and the substitution of a balanced oil column as operating medium in place of a sucker rod string. In the surface unit, the energy output is to lift the weight of the rod string plus the oil load, the energy recovery being due to the descending weight of the rod string. In the bottom hole unit, the energy output is to compress by the length of stroke in the power unit cylinder a gas volume under pressure, equivalent to raising the weight of the oil column and also to lift the oil load. The energy recovery is due to the downstroke expansion of pressure in the power cylinder. It will be noted that the friction of the long rod string up and down is also eliminated.

The continuity of the reciprocating action of the power unit is due to the constant operation of the valve unit, opening and closing one valve and in sequence opening and closing the other, cycle after cycle. The gradual opening of the valve orice with causing gradual acceleration and gradual stopping together with the air cushioning at the top and bottom of each stroke is of n vel and great advantage in the corresponding travel of the pump plunger, giving the best efficiency to the lifting and lling action of the pump. The speed of the piston travel during each stroke is further controlled by the throttling valves between the tanks and the valve unit, regulating the rate of travel of the piston up and down to correspond to the interval of the valve unit valves opening and closing.

Itis understood that my apparatus and method will operate in the same manner regardless of the length of the pipe leading to the well or the depth of the well, allowance being made, of course, for the oil friction in the line. Also, in the adjusting of the length of the stroke of the piston it will be obvious that this may be varied by the pneumatic pressure above the piston in the cylinder 8 calculated at the time of installation and by the pneumatic pressure in the recovery tank which may be regulated at will, during and the' the gradual closing thereof,'

operation, and stop the piston on its downward stroke at any desired point.

It is evident that the power unit cylinder may be of any practical length desired, its piston stroke being limited only by the operating stroke of the reciprocating oil pump to which it may be connected.

It is also evident that due to the use of a balanced oil transmission column the number of strokes per minute may be increased beyond usual practice as the speed of operation is not controlled or connedto the travel limitations of a loaded sucker rod string with its stretch, friction and other limitations.

The compressed air or gas for the various pressure volumes in the power unit cylinder and the two tanks may be obtained from a portable or installed compressor or, from cylinders of commercial compressed air or neutral gas, such is nitrogen, both readily obtained. One cylinder or lmore may be kept connected after installation for adjusting purposes.

It is also to be noted that the operation of the power driven pump is continuous at almost a fixed load and uniform speed with consequent high eiilciency for lboth the pump and motive power and with minimum wear.

What is claimed as new is:

1. A pump unit comprising, a well casing, a cylinder in said casing, a housing about said cylinder, a head in the upper end of said housing, a

' recess in said housing head, an air vent through said head opening outwardly, a tubing extending to the surface and connecting at its lower end to said recess in said housing head, passages from said recess to said housing, a head in the lower end of said housing, said heads closing the ends of said cylinder openings above said head from said housing to the lower end of said cylinder, a piston in said cylinder, a piston rod on said piston extending through said lower head, a tubing below said lower head, a pump plunger in said last mentioned tubing, a sucker rod connecting said plunger to said piston rod in said tubing, a packer about said tubing in the well casing, discharge outlets` in said .tubing above said packer, and

means to raise'and lower said piston at periodic intervals.

2. A deep well reciprocating pump comprising, a well casing, a power unit suspended in the well casing, said power unit comprising a cylinder, a housing spaced about said cylinder, an upper head in said housing closing said cylinder, a downwardly closed recess in said head, a tubing extending from the surface and connected at its lower end to the recess in said head, an outwardly closing vent passage from the recess in said head. a fluid to flll said tubing, a moving piston to be moved ahead of said fluid in filling said tubing to expel the air or gas therein through said vent passage, said piston formed to seat in said recess to inwardly close said vent passage, uid passages in said head leading from said recess to said housing space, a lower head in said housing also closing the lower end of said cylinder, openings into said cylinder from said housing space above Vsaid lower head, iiuid extending from said cylinder through said openings and housing space into the passages Vconnecting to the iluid in said tubing, a piston in said cylinder, a piston rod extending downwardlythrough said head. a tubing attached to said lower head and extendingv downwardly, a reciprocating pump in said tubing, a

` ing sealing with the well pump to said piston rod, a packer about said tubcasing, discharge outlets in said tubing above said packer, and pressure means to reciprocate said fluid column periodically to raise and lower said piston and said attached pump.v

3. In a power unit suspended in a well and st tached to reciprocate a deep well pump, a cylinder, a spaced housing surrounding said cylinder, heads at each end connecting said cylinder and housing, a piston in said cylinder, a lower extension thereon, a rod thereon extending through the lower head, a pump barrel, a plunger secured vto said rod and reciprocable in said barrel, a tubing from the surface connecting through the upper head of said power unit to said housing, a balanced pressure uid lling said tubing, a passage from said housing to the under side of the piston in said cylinder, a pneumatic pressure chamber within said cylinder above said piston to contain fluid to effect said balance, a stop member in said cylinder separating the piston travel section from the upper pneumatic chamber thereof, an opening through said stop member to connect the two sections of said cylinder, a downward extension on said stop member forming a recess to receive an upward extension on said piston, fluid carried on said piston to furnish cushioning means and limit the upward travelof said piston, a recess in the lower head of said cylinder to receive the extension on the under side of said piston, liquid means to cushion the downward travel of said piston, surface control means to periodically apply fiuid under higher pneumatic pressure to said balanced fluid column to raise and then release same thereby reciprocating the said piston with its rod connections between the said cushioning limits in said cylinders.

4. In a well pump of the character described, a power cylinder, upper and lower heads thereon, a housing spaced outside said cylinder and connected with said heads, a tubing connected with said upper head, passages in said upper head from said tubing to said housing, a vent passage from the lower end of said tubing through said upper head to the outside of said housing, an outwardly opening check valve in said vent passage. a pistonlike element fitting within said tubing and adapted to be forced by liquid pressure through said tubing to close said vent passage, a piston operating in said cylinder, there being an opening from said housing to the lower end of said cylinder to conduct pressure fluid from said tubing to the cylinder below said piston, and a load engaging rod on said piston.

5. In a well pumping device, a well casing, a cylinder therein, a piston working in said cylinder, heads at each end of said cylinder, a tubing connected with a recess in the uppermost cylinder head. means to force liquid downwardly in said tubing, a housing spaced from said cylinder and connected with said heads, liquid passages from said housing to the lower end of vsaid cylinder; passages from said recess to the interior of said housing, a vent passage from said recess through the upper end of said upper head, a check valve in said vent passage, and a freely moving piston-like member movable downwardly in 'said tubing to close said vent for the purpose described.

WARREN B. REED.