US2377913A - Pumping apparatus - Google Patents

Description

June 12, 1945.

W. H. WINEMAN PUMPING APPARATUS Filed Sept. 17, 1940 5 Sheets-Sheet 2 A 4 Mow,

June 12, 1945. w. H. WINEMAN YUIEPING APPARATUS 5 Sheets-Sheet 4 Filed Sept. 17, 1940 5227622202 Wade]? 3172226222620.

W 5 w w Jung 12, 1945. w wm 2,377,913

I PUMPING APPARATUS V Fild SeptJ-lfi, 1940 5 Sheets-Sheet 5 Patented June 12, 1945 PUMPING APPARATUS Wade H. Wineman, Michigan City, Ind., assignor to Sullivan Machinery Company, a corporation of Massachusetts Application September 17, 1940, Serial No. 357,155

13 Claims.

This invention relates to pumping apparatus, and more particularly to apparatus for yieldingly supporting a positively actuated member for raising and lowering a sucker rod connected to a pump in an oil well.

In producing an oil well by a pump located near the bottom of the well and driven through a sucker rod connected to a reciprocating device at the surface, there will be a large increase in the load on the rod during each reversal between its downward and upward strokes. This heavy load repeatedly applied to the sucker rod causes a serious reduction in the life of the rod. The power consumed is more than would be necessary to do the useful work, and the available power necessary is greater than that required if the load was reduced. I

It is an object of this invention to provide an improved pumping system. It is another object of this invention toprovide an improved pumpactuating apparatus. It is still another object of this invention to provide an improved beamtype pumping system having means for reducing the peak loads on the sucker rod and on the .pumping system. 1 Still another object of this insystem in which the preferred form of the invention is incorporated.

Fig. 2 is an enlarged vertical sectional view,

partially in elevation, through the beam-supporting structure shown in Fig.1.

Fig. 3 is a vertical sectional view similar to Fig. 2 but showing the parts in different relative positions.

Fig. 4 is a view similar to the lower portion of Fig. 3 but showing a modified form of valve controlled by-pass for-returning fluid to the lower side of the piston.

Fig. 5 is an enlarged detail sectional view showing the valve control for the by-pass of Fig 4.

Fig. 6 is a vertical sectional view through a portion of a. modified form of beam-supporting structure.

Fig. 7 is a cross sectional view taken on the 1 plane of the line 1-1 of Fig. 6.

Fig. 8 is a vertical sectional view, with parts in elevation, showing a further modified form of beam-supporting structure.

Fig. 9 is a fragmentary view similar to Fig. 8 showing parts in different relative positions.

Fig. 10 is an enlarged vertical sectional view through a combined oil and air pump employed with the structure shown in Fig, 8.

Fig, 11 is a vertical sectional view through a still further modified form of beam-supporting structure.

Fig. 12 is a vertical sectional view through a modified form of connection between the supporting structure and the walking beam.

Fig. 13 is a sectional view, with parts broken away, taken on the line [3-43 of Fig. 12.

Fig. 14 is a sectional view taken on the plane of the line I l-I 4 of Fig. 12.

In the illustrative form of the invention shown in Figs. 1, 2 and 3 a beam type pumping apparatus, generally designated I, is connected to a polished rod 2 extending through a casing head 3 of a well and connecting to a sucker rod line (not shown). The pumping apparatus l includes ,a supporting structure, generally designated 4, a walking beam 5, and a driving unit 6 of conventional form connected by a pitman l with the walking beam and driven in any suitable manner.

Referring now more particularly to the supporting structure 4 for the walking beam, it will be noted that an upright cylinder 9 rests upon a lower cylinder head l0 and has a bore ll containing a reciprocable hollow piston l2. Extending upwardly from the piston through a packing 14 in an upper cylinder head 15 is a tube-like 5 piston rod l6 which is closed at its upper end by a wall I1. Threaded onto the upper end of the piston rod is a coupling l8 which receives the threaded end of a cylindrical shaped member journaled at 2| to the walking beam 5 and guided for vertical movement by a sleeve-like member 22 attached to the upper ends of supporting legs 23. A tank 25 containing a gaseous fluid, in this case air, under pressure is connected by a pipe 25 to a passage 21 in the lower cylinder head Hi which opens into a pipe 28 threaded into an open ing in the lower cylinder head and extending upwardly into the piston rod.

The diameter of the pipe 28 is such that there inner surface of the hollow piston rod, an annular space 29 through which gaseous fluid, conducted from the tank through pipe 26, passage 2'! and pipe 23, may pass into the hollow'piston !2. In order to seal the gaseous fluid within the tank and its connected passages, and to lubricate the walls of the cylinder bore, there is provided within the lower portion of the cylinder bore a liquid of such a volume that the .space within the hollow piston is not quite filled when the piston rests upon the lower cylinder head. As th piston moves upwardly in the cylinder bore the level of the liquid drops, since it then occupies space that had previously been occupied by the walls ofthe piston, but the length of the bore is such that even when the piston engages the upper cylinder head the lower end of the piston'extends below the surface of the liquid a substantial distance and the seal is maintained. Means areprovided for cushioning the piston 12 as it moves toward the lower cylinder head, and this means comprises an upwardlyprojecting portion 30 formed on the lower cylinder head and having a slopingsurface 3| which forms -an annular space -between the projecting portion and the .cylinder 'walL-of smaller radial dimension ..at its @lower end. A flange 32 formed around: the lowerendof thepiston is received in the annular-spacezand partially entraps liquid tocushion the piston as it moves towardthelower cylinder head.

Breathing means are provided for the upper end of the cylinder bore andinclude .a' connection 34 communicating with the bore .ata point spaced from the upper end ofthe cylinder-so that a space is provided in the'upper end of the here after the connection 34 is passed, within which fluid may becompressedto cushion'upward movements of the piston. The connection .34opens into a reservoir 35 connected bya hose-.3$to a chamber 3'! in the lower-endof the cylindrical shapedmember 20. The chamber.3l communicatesthrough a baffled passage 38 withalargerrchamber 39 communicating with atmosphere through openings 40 atits upper end whenthepiston' is in its normal raised position. A connection 42 connects the reservoir 35 withthe upper-end of'the-oylinder bore and is-pro-videdwith a valve-:43 which permits fluid flow toward the cylinder-bore, therebypreventing the-creation of a vacuum in the cylinder as the piston-moves downwardly in thespace above the connect on '34, but thevalve '43 prevents any flow-of 'fluid-away1fromthe cylinder bore.

.It will-be noted that-the gaseouspressure "in the tank and its connected spaces-willact.against the upper surfaceof the liquid-and againstthe lower surfaces of the'upper end wall of',the piston and the wall I"! closing the upper end of the piston rod to urge the piston'inan upward direction. The gaseous pressure will be such duringnormal operation of the pump that the p ston willlse held in a raised position even with peak loads on the walkingbeam. The pressure against the surface of the liquid will cause the 'liquidto beforced gradually. between the 1 walls of the: pistonandthe cylinder to thespace in the bore-above theapiston. Means is provided for returningthe-l'quid and a small amount of air with it-from the upper to the lower side of thepiston when thepressure in the upper end of the cylinder .bore exceeds that in the lower. end, and this means comprises a valve cage 44 threaded into aniopening-in-the-upper wall of the piston and supporting a springpressed ball valve 45 which controls commun cation between a passage 46 opening into the upperpart of the cylinder bore and a passage opening into a pipe 41 which extends downwardly below the surface of the liquid to provide a seal for the valve. To prevent the pressure in the cylinder beneath the piston from becoming too great, there may be provided a suitable relief valve, not shown, which opens to vent air from the tank 25 and its connected system when the pressure exceeds the desired maximum value. If the pump is shut down for a considerable time' all the liquid in the cylinder may eventually be forced to the upper side .ofthe piston, and part of it may flow through the connection 34 to the reservoir 35 and through thehose36 to the chambers 31 and 39. In order to return the liquid to the lower end of the cylinder bore where it may perform its intended functions there is provided a connection 49 opening into the cylinder bore at a point slightly above the piston whenthe latter is in its lowermost position and communicating with a passage 50 formed in the lower cylinder head and opening intoithelower end of the cylinder bore. .A manually qcontrolled throttle valve *5! controls the flowof fluid through-connection-49. In order that theliquid may flow freely vfrornthe'upper to the lower portion of the cylinder'bore, the tank 25 andits-connected system should-be vented to atmosphere by any suitable 1 means. After the liquid has passed into the lower portion ofthe cylinder, the valve, 5 I and theventing means-are closed,: and the tank is repressuredby delivering air-to it from any'outside-source.

The.mode of operation of the apparatus described :will .be readily understood from what has been said. Air issuppliedto the tank -25 until .a pressure is built up -within it and..-its connected system whichisrsufficient to raise the piston 12 and the walking beam :5.and.hold.the piston out .ofcontact with the lower .cylinder head -.l0..ev.en when peaklloads .arecarriedby the walkingbeam. oAsthewalking beam. isdriven by theunit '6 to reciprocate the rod 2 and drive the pump there will be a peakv load on the system. soon .after the unit 'Bstarts operating on the walking beam to reverse the direction of travelof the rod'Z from adownwardto an upward stroke, and the piston -I2'wi11 'be'forced to a low point inthecylinder bore I I. The load will continueto remain'heavy during'the'early portion-of the upward stroke, but, as the drive of the walking beam by the power unit 6 slows down, the load on the walking beam will be reduced and the piston l2 will be'moved upwardly by the compressed air actingon the lower surface of the upper end wall of the'piston and on the lower surface of the wall 11 closing the: end

35, hose 36, chambers.3'ljiand 3fiiandopenings 40 toatmosphere until-'thepistonvcovers the end of connection 34; then air and liquid above the piston will be entrapped and, due to the inertia. of the upwardlyv moving parts, a pressure will 'be 101111131112) intherspaceabove-the piston which is greater than that below the piston; the ball valve 44 will be moved from its seat andtheiliquid with some air will be 'forcedthrough; pipe 1 41- to the lower-"side of the piston. Some of the liquid 7 .above the'piston will :enter connection 34 and will arrive at the top of its stroke in the cylinder 9 at the "same time the driving unit 6 reaches the point where it discontinues its driving of the walking beam to effect an upward movement of the rod 2. The piston will then remain in its uppermost position until the unit 6 operates againon the walking beam toreverse the travel of the rod 'Zlfrom a downward toan upward stroke.

Becauseof the yielding in the supporting structure for thewalking beam, the peak loads which are encountered in the conventional beam pumping mechanism are avoided. There is obtained with the yieldable structure not only a great reduction in the rod loads, but also a substantial reduction in the stress ran e in the rod, and a of the piston; then compressed air will escape from beneath the piston until the pressure is re duced and the piston moves down into the liquid again. Even though an appreciable amount of liquid may have been forced into the reservoir and some ofthe compressed air may have escaped fromunder the piston, the apparatus maybe restored to its normal operating condition by simply operating the pumping apparatus for a short time. The intermittent application and release of the load on the walking beam causes the piston to reciprocate, and each time the piston moves upwardly some of the liquid above it will be forced past the valve 44 to the lower end of the cylinder. After all the liquid has been returned to the lower side of the piston there will be a small amount of air forced by the valve M on each up-stroke of the piston, which will build up the pressure in the tank 25 and its connected passages until released by asuitable safety valve.

If the pumping apparatus remains shut down long enough the liquid'will pass above the piston to the. reservoir 35 and may flow through the hose 36 to the chambers 31 and 39; then the air pressure below the piston may be so reduced that the piston will not be moved sufiiciently to restore the system during pumping operation. To restore the system when this condition exists the pressure remaining in the tank 25 is vented to atmosphere, the valve is opened to drain the liquid through connection 49 into the lower end of the, cylinder bore, and then the valve 5! is closed and the tank is repressured.

In Figs. 4 andv 5 there is shown a construction similar to that of Figs. 2 and 3 except for the means for conducting fluid from the upper tothe lower'side of piston l2. Threaded into the upper cylinder head [5 is a valve cage 53 having a portion 54 extending down into the cylinder bore I! and received within a well 55 formed in the upper surface of the piston I2 when the latter ismovedto the upper end of the cylinder bore.

against a manually adjustable abutment 58 to prevent normally the flow of fluid from the cylinder bore through a passage 59 to a chamber 68 formed in the valve cage and through a connec tion 62 opening into the cylinder bore near its lower end. During operation of the pumping system any liquid escaping to the upper side of piston I2 flows into the well 55 and is forced through'the passage 59, past the valve 56 to the chamber 60 whereit is conducted through connection 62 to the cylinder bore beneath the piston. By adjusting the abutment 58 the valve 56 may be controlled to open at pressures within a range which varies with the strength of spring 5i. Figures 6 and 7 show a cylinder-and piston arrangement in which a cylinder 64 is providedwith an opening 65 at its upper end for receiving a hollow piston 65, and a packing 61 is pressed into fluid sealing engagement with the piston by a cap 68 suitably secured to the top of the cylinder. Formed in the cylinder is a bore 69 somewhat larger in diameter than the opening 65 and extending from the lower side of the opening to a lower cylinder head 10. A flange ll formed around the lower end of the piston is slidably received in the bore 69 and is receivable. as explained in the description of Figs. 2 and 3, in an annular space between a projection 12 on the cylinder head and the walls of the bore to partially entrap liquid and cushion the piston Grooves M are formed in the walls of. the bore 59 and extend between points spaced a short distance from each end of the bore so that liquid maypass freely between the upper and lower sides of the flange except as it is moved toward either cylinder head at the end of the piston strokes. It will be noted that the upper ends of the grooves have inclined surfaces 15 which provide gradually reducing escape passages for the liquid above the flange as the piston approaches the upper end of its stroke, and thus effect a cushioning of the piston. The cylinder 64 is filled with a liquid to a point, such that its level is always above the upper end of the bore 69 and insuresthe filling of the space above the flange to provide the necessary cushioning action. A suitable gas under pressure is supplied to the space within the hollow piston above'the liquid from a connection 26' connected through passage 21' and pipe 28'.

The operation of this modification of the invention is the same as that shown in Figs. 1 to ,3 except that the upward strokes of the piston are cushioned by partially entrapping liquid in a space above a flange formed on the piston. Since the liquid and the gaseous fluid are always sealed against escape, it is not necessary that means he provided for restoring the system to normal operating conditions.

In the modification of the invention shown in Figs. 8, 9 and 10, a cylinder 18 is supported in a vertical position by legs 19 and receives in its bore .a sleeve-like piston 8| closed-at its upper end and having. pivotally attached thereto, at 82, a walking beam, 83. The cylinder bore is closed at its lower end by a wall and contain; a liquid for sealing air under pressure within a space at the upper end of the sleeve-like piston. Any liquid passing between the walls of the piston and cylinder enters an annular grooved? formed in the walls of the cylinder bore at its upper end and is conducted through a connection 88 to a tank 89. A pump, generally designated 9!], is provided for pumping liquid from a hoses! con- A ball valve 56 is urged by a spring 51 acting nectedtothe tank 89,;arid1or pumping: air taken from the atmosphere througha filter 92, into the-cylinder bore through -a connection 94.

The pump'90 comprises a cylinderblock #95 attached, as by bolts 95, to 'aiportion formed on and extending transversely from the'upper end of the piston. Formed in thecylinder block are stepped bores 91 and 98 'openinginto each other, and the larger bore opens through the top of' the cylinder block. A piston I having portionsIflI and I02 receivable, respectively, inthe bores 91 and 98 is connected by a link I03 to the walkin beam to be driven thereby.The hose 9I opens into a passage I05 controlled by a ball valve I06 and opening into the lower end ofthebore 91. 'A passage I01 in the cylinder block connects thelower ends of the cylinder bores 91 and 98 and is-controlled'by a ball valve I09. A passage III) connects the lower end of the cylinder bore 98 to the air filter 92 under the control of a ball valve III and to the connection 94 under the control of a ball valve I I2. During rocking motion of the walking beam the pump 90 will be operated to pump air continuously from the atmosphere to the cylinder bore and. to pump with'it any liquid that may have escaped to the tank 89. As the pressure in the cylinder bore increases withthe addition of air from the atmosphere the piston is'raised, and in order to permit the pressure in the cylinder bow to be released after the piston has been raised apredetermined distance, there is provided a conduit I I4 connecting th cylinder bore at a point slightly above the level of the liquid, withthe groove 81. In the top of the tank 89 is a vent II5 providing for'the escape of air that enters the tank from groove 81 through connection 88.

The mode of operation of this modification of the invention will-be clearly apparent from the description given. Liquid may be placed either in the cylinder bore or the tank 89, and then if the pressure in the cylinder is insufficient to support the pumping apparatus the walking beam may be operated without a load until the desired pressure has been built up by the supply of air from pump 90. A load may then be connected to the walking beam and, as thebeam. is driven, the pump returns to the cylinder any liquid escaping between the cylinder and piston walls to the tank 89 and supplies air from the atmosphere to build up the pressure in the cylinder bore until the piston moves above the lower end of conduit I I4 and vents the bore through groove 81, connection 88 and vent H5 in the top of tank 89.

In Fig. 11 there isshown a modificationsimilar to that of Figs. 8 to 10. The cylinder H6 in this modification, however, is supported'by a cross member II1 attached to the 1egs'l9 at points below their tops, and reciprocably supported by the cylinder is a piston IIH having extending from its upper end a piston-rod II9 reciprocably guided by a sleeve-shaped member I attached to the upper end of thelegs 19. The Walking beam 83 is pivotally mounted at I2I on a member I22 suitably attached to the upper end of the piston rod. A coil spring I23 surrounds the piston rod and is supported by an adjustable member I24 in :a position to abutithe lower 'endof the sleeve I20 and cushion the piston at the ends of its upward strokes. A'pump I 26; like that shown in Fig. 10, is connected to-a member I21 attached to and extending laterally from the lower end of the cylinder. A link I28 is pivotally connected to the piston-of the pump I2Bandto.a bell crank arm I29 whichispivotally mounted on: a'member I30 attached to the cross. member. 1. 'A-roid I3I is connected to the 'bellcrankzarmand has-a sliding connection with a member I32 pivotally connected to thewalking beam. .As'the beam is driven, the sliding connectionbetween member I32-a'nd rod I3I permits vertical movementof the beam, but transmits a rocking motion to therbell crank arm which drives thepump piston through link I28. In operation of the pump, air :and liquid are pumped,.respectively, from the atmosphere and-tank I33 through a conduit I34 opening into the lower end of the cylinder bore. Liquid'escaping between the walls of the cylinder and-piston. entersa groove I36and is conducted by a conduit I31 to the tank. On predetermined upward movementiof the piston II8, pressure fluid escapes through a. pipe connection I38, the groove I36, conduit I31 and to atmosphere through a vent I39 in the top of tank I33.

'In Figures 12, 13 and 14 there is shown amodified form of guiding structure for guiding the reciprocatory movements of the piston rod I6. In this structure the piston rodis threaded at its upper end into an opening in a plate I40 attached, as by bolts I4I, to a crosshead I42. The legs of the supporting structure 4 are bent to form parallel upper portions I44, and connected to each of these portions, as by rivets, is a guide member I45 that reciprocably engagesthe-crosshead I42 as shown in Fig. 14. Supported by the crosshead is a pivot pin I46 that pivotally supports a member I41 to which the walking beam-5 is attached. Formed in the crosshead is a chamber I48 that is connected to atmosphere at its upper end at points adjacent each guide member I 45 by vent ports I49. The hose'36 communicates with the chamber I48 at its lower end. During operation of the pump, aircarrying liquid in the form of mist is forced throughthe hose38 to the chamber I 48and is vented to atmosphere through the ports I 49. Partof the liquid condenses as it passes through the vent ports, and

lubricates the guide members. When the pumping system is shut down thechamber I48 acts as a storage chamberforliquid escaping through the hose 36.

As a result of this invention, it will be noted that an improved yielding supporting structure -for a walking beam has been provided. It will further be noted that there has been provided with the supporting structure an improved'means for building up the yielding force automatically to a value sufficient to support the walking beam and its loads, and for maintaining the force at the necessary values. It will further be evident that there is obtained a sealing and-a lubrication What I claim as new and desire to secure'by' Letters Patent is:

1. A yieldable supporting structure adapted for association with a well pumping apparatus of the kind embodying a walking beam, comprising," in combination, means adapted to yieldingly-sup- 'port a walking beam and includinga cylinder containing a reciprocatory piston, means: for connecting said piston to the walking beam, passage means for connecting a substantial volume of air under pressure exceeding atmospheric in communication. with the lower end of said cylinder, means for venting said cylinder to atmosphere at a point spaced from its upper end,said piston moving upwardly under the action of the air pressure when the load on the walking beam is reduced, effecting a closure of said venting means and an increase in pressure at the, upperjend of said cylinder, and valve controlled passage means for delivering fluid from the .upper to'the lower end of said cylinder when the pressure Tat its munication with the lower end of said cylinder,

-a vent opening into said cylinder at a" point spaced from its upper end for connecting said cylinder to atmosphere, said piston moving upwardly under the action of the air pressure when the load on the walking beam is reduced, covering said vent and compressing air within :the upper portion of said cylinder, and valve controlled passage means for delivering fluid-from the upper to the lower end of said cylinder when the pressure within the upper end exceeds 'the pressure in the lower end. Y a

3. A yieldable supporting structure adapted for association with a well pumping apparatus of the kind embodying a walking beam, comprising, in combination, means adapted to yieldingly support a walking beam and including a cylinder containing a reciprocatory hollow piston open at its lower end, means for connecting said piston to the walking beam, passage means for connecting a substantial volume of air underpressure exceeding atmospheric in communication with the interior of said hollow piston, the lower portion of said cylinder and said piston cooperating to form a chamber space adapted to contain a volume of liquid for continuously sealingfthe lower end of said piston against the escape of air from within the latter, means including a piston controlled vent passage for connecting the upper end of said cylinder to atmosphere, said piston moving upwardly on reduction of loadon the walking beam and effecting closure of said vent passage and an increase in pressure at theupper end of said cylinder, and valve controlled passage means for delivering fluid from the upper to the lower end ofsaid cylinderwhen the pressure at its upper end exceeds the pressure at its lower end. i I

4. A yieldable supporting structure adapted for association with a well pumping apparatus of the kind embodying a walking beam, comprising, in combination, means adapted to 'yieldingly support a walking beam and including a cylinder containing a reciprocatory hollow piston open at its lower end, means for connecting said piston to the walking beam, passage means for connect ing a substantial volume of air under pressure exceeding atmospheric in c'ommunication with the interior of said hollow piston, the lowerportion of said cylinder and said piston} cooperating to form a chamber space adapted to contain a .volume of liquid for continuously sealing the lower end of said piston against the escape of air from within the latter, means including a vent port opening into said cylinder at a point spaced from its upper end for venting the upper portion of said cylinder to atmosphere, said piston ,movinggupwardly under the action of the air ,pressurewhen the load on the walking beam is reduced, covering said vent port and compressing air, in the upperend of said cylinder, and valve "controlled passage, means connecting the upper and lower ends of said cylinder for delivering fluid, fromgthe upper to the lower endof said cylinder when thepressure at its upper end exceeds the. pressure at its lower end.

5, A yieldable supporting structure adapted for association withawell pumping apparatus of the kind embodying a walking beam, comprising,

at its lower end, means fo r connecting said piston to the walkingbeam, the lower portion of said cylinder and said piston cooperatingtoform a chamber space adaptedtocontain avolume of liquid for continuously sealing the lower, end of said piston against the escape of air frbm within the latter but insuificient to fill the space within said piston when the latter isin its lowermost position, means including a conduit opening through the lower end of said cylinder and extendingabove the level of said liquidfor connecting the space within said piston above the liquid to asubstantial volume of air under pressure exceeding atmospheric, means including a piston controlled vent passage for connecting the upper end of said cylinder: to atmosphere, said piston moving upwardly under the action of the air pressure when the load on thewalking beam is reduced and, on a predetermined upward movement of said piston, closing said vent pase sage and compressingfluid within the. upper end of said cylinder, and valve controlled passage -means for delivering-fluid from the upper to the lower end of said cylinder when thepressure at itsaupper end exceeds the pressure at its lower end. I 1

6. A yieldable supporting structure. adapted fdr association/with a" well pumping. apparatus of the kind embodying a walking beam,l comprising, in combinatiommeans adapted to yieldingly support a. walking beam and including a cylinder containing, areciprocatory hollow piston open at its lower end, means forcon'necting said piston to the" walkingbeam, means for connecting the interior of said piston in communication with a volume of air under pressure exceeding atmospheric, thelower portion of said cylinder and said piston cooperating to form a chamber space adapted to contain a volume'of-liquid for continuouslyfsealing thelower end of said piston against the escape of air from within'the latter, means for cushioning said piston as the latter moves toward the lower end of said cylinder, saidcushioning means including a radially extending flange formed around the lower end of said piston and aspace of decreasing cross sectional area at'the lower end of said cylinder within which said flange movesand partially entraps liquid, means for venting the upper end of said cylinder to atmosphere, said a piston moving upwardly under the action of the air pressure when the loadonthe walking beam "is reduced,

cutting off communication of'said venting means with said cylinder after predetermined: movement and compressing fluid within theupper; end ofthe latter, and valve controlled passage;..means for deliveringfiuid from theupperrto the .lower end of said cylinder when the pressure within its upper end exceeds the pressure within its lower end.

7; A yieldable supporting structure adapted for association with a well pumping apparatus of the kind embodying a walking beam, comprising in combination, means adapted to yieldingly support a walking beamand including a cylinder containing a reciprocatory hollow piston open at its lower end, means for connectingsaid piston to the walking beam, the lower portion of said cylinder and said piston cooperating'to form a-chamber spac adapted to containa volume of liquid for continuouslysealing the lower end of said Piston against the escape of air from within the latter but insuflicient to fillthe space within said piston when the latter is in-its lowermost position, means including. a conduitopening through the lower end of said-cylinder and extendin above the level of said liquid forconnecting the interior of said piston in communication with a volume of air under pressure exceeding atmospheric, and means for venting the-upper end of said cylinder.

8, A yieldable supporting structure adapted for association with a well pumping apparatus of the kind embodying a-walkingbeam, comprising, in combinatiommeansadapted toyieldingly support a walking beam and including a cylinder containing a reciprocatoryhollowpiston open at its lower end, means for connecting the piston to a walking beam, the lower portion of said cylinder andsaid piston'cooperating to form a chamber space adapted to contain a volume of liquid for sealing thelowerend-'of-said piston against the escape of pressure fluid from within the latter during normal reciprocation in said cylinder, said hollow piston providing a space above said liquid for storinga: gaseous fluid under pressure, means including a-reservoir open to. atmosphere and communicating with the upper portion of saidcylinder at a point spaced from its upper end .for collecting. liquid escaping upwardly past said piston, said piston moving upwardly. on .reduction' of load .on .the

walking beam, cutting ofi communication with 1 said reservoir and trapping liquid within. the upper portion of said cylinder, and .Valve'controlled passage mean for deliveringliquidfrom the upper to the lower end of said cylinder when the liquid trapped within the upper end i subjected to pressure by the upward movement of. said piston.

9. A yieldable supporting structure adapted for association with a well pumping apparatus'of the kind embodying a walking beam, comprising, in combination, a cylinder, a hollow piston open at its lower end reciprocable within'saidcylinder and having a piston rod pivotally connected when in use to a walking beam, means forslidably guiding said piston rod, a chamber within said piston rod, means for normally venting said chamber to atmosphere at points in said piston rod above said guiding. means, passage means connecting said chamber in communication with the upper portion. of saidcylinder, and.v means for connecting the space within said hollow piston in communication with a volume of air under pressure exceeding atmospheric, the lower portion of said cylinder and said piston cooperating to form a chamber space adapted: to contain a.

volume of lubricating liquid for sealing the air within said hollow Piston, the lubricating liquid being forced gadually past said piston by air pressure to the upper portion of said cylinder. where it is carried by air escaping through said venting means to eiiect a lubrication of said piston rod.

10. A yieldable supporting structure adapted for association with a well pumping apparatus of the kind embodying a walking beam; comprising, in combination, a cylinder, a hollow pistonopen at its lower-end reciprocable within said cylinder and having a piston rod pivotally connected when in use to a walking beam, means for slidably guiding said piston rod, a chamber within said piston rod, means for normally venting said chamber'to atmosphere atpoints. above said guiding means, passage means connecting said chamber in communication with said cylinder at a point spaced from the upper end of'the latter, means for connecting the space within said hollow piston in communication withv a volume ofair under pressure exceedingatmospheric, the lower portion of said cylinder and said piston'cooperatin to form a chamber space adapted to contain a volume of liquid for sealing the air within said hollow piston, said piston movin upwardly under the action of the air pressure when the load on the walking beam is reduced, cutting off communication between said cylinder and said passage means and compressing air within the upper portion of said cylinder, and valve controlled passage means opening through the upperv end of said cylinder and communicating with the latter adjacent its lower end for delivering fluid from the upper to the lower end of said cylinder whenthe pressure at its upper end exceeds the pressure at its lower end.

11. A yieldable supporting structure adapted for association with a well pumping apparatus of the kind embodying a walking beam, comprising, in combination, a cylinder, a piston reciprocable within said cylinder and having a piston .rod pivotally connected when in use to a walking beam, means including a vent port opening into said cylinder at a point spaced from its upper end'for normally venting the upper portion of said cylinder freely to atmosphere, means including a valve opening toward said cylinder for connecting the. upper end of the latter to atmosphere, means for connecting thezlower portion of said cylinder in communication with a volume of air under pressure exceeding atmospheric, said piston moving upwardly under the actionof. air pressure when the load on the walking beam is reduced, overrunning said vent port and compressing air within the upper portion of said cylinder, and valve controlled passage means carried by said piston for delivering fluid from the upper to thelower end of said cylinder when the pressure at'its upper end exceeds the pressure atits lower end.

12. A yieldable supporting structure adapted for association with a well pumping apparatus of the kind embodying a walking beam, comprising, in combination, a cylinder, a piston reciprocablewithin said cylinder and having a piston rod pivotally connected when in use to a walking beam, means including a vent port opening into said cylinder at a point spaced from its upper end for normally venting the upper portion of said lcylinder freely to atmosphere, means including a valve opening toward said cylinder for connecting the upper end of the latter to atmosphere, means for connecting the lower portion of said cylinder in communication with a volume of air under pressure exceedingatmospheric, said piston moving upwardly under the action of air pressure when the load on the walking beam is reduced, overrunning said vent port and compressing air within the upper portion of said cylinder, and means including valve controlled passage means opening through the upper end of said cylinder and communicating with the latter adjacent its lower end for delivering fluid from the upper to the lower end of the cylinder when the pressure at its upper end exceeds the pressure at its lower end.

13. A yieldable supporting structure adapted for association with a well pumping apparatus of the kind embodying a walking beam, comprising, in combination, relatively reciprocable cylinder and piston elements, means for connecting one of said elements to a walking beam, means for connecting one end of said cylinder in communication with a volume of air under pressure exceeding atmospheric whereby the element connected to the walking beam is yieldably supported, means including a port opening into said cylinder at a point spaced from the other end of the latter for venting the other end of said cylinder to atmosphere, said element connected to

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