US2477359A

US2477359A - Expansible chamber motor with oscillating cylinder and piston actuated distributing valve

Info

Publication number: US2477359A
Authority: US
Inventors: Lilburn S Barksdale
Original assignee: Individual
Current assignee: Individual
Priority date: 1945-01-24
Filing date: 1945-01-24
Publication date: 1949-07-26
Anticipated expiration: 1966-07-26

Description

L. S. EXPANSIBLE CHAMBER MOTOR WITH OSCILLATING CYLINDER BARKSDALE July 26, 1949.

AND PISTON ACTUATED DISTRIBUTING VALVE 2 Sheets-Sheet l Filed Jan. 24, 1945 .Il lill; 1 7 www Arron/vsn v July 26, 1949. s. BARKSDALE EXPANSIBLE CHAMBER MOTOR WITH OSCILLATING CY 2,477,359 LINDER AND PISTON ACTUATED DISTHIBUTING VALVE 2 Sheets-Sheet 2 Filed Jan. 24, 1945 www , INVENTOR, gave/v .5. ne/sous,

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Patented July 26, 1949 25477.358 -EXPANSIBLE .CHAMBER AM ojrolt wrm ANDfPisfroN -nd'rU-n'r-ED Discurso-UNG VALVE .filatura jitpwplicationJanuaryj 24, 1945, SerialrNo. 5145274 .u Claims. c1. 1- 2. 1 .-i.64)

invention .relates in .general to oil well .l-pumproperating .mechanism, and -ithe `principal ...obj ects ofttheinvention .are directed -teward the provision of a novel.-and..efectivehydraulictpump jack operating :in conjunction `Jwith tthe A.usual ..walleingbeamlpumplgean `4"Ciertain .aspects .of :the invention are applicable cto .use in H.other .elds, thoweven and rthe inventionushould not .loeeon- `strueri aslimited.solelytooil vv.ell...purnpingd equipment.

`@Thefusuahform otoiLpumping.- equipmentcomprises avertically reciprocating .pump element -iatttheebottom- .ofithe-welt actuatedtfrom .a- .Walk- 2ing beam .at.-the..head of.^the...welli.through .a :long string-hof suckerrods. .:Fcionpumpingunits .ofthe .walking beam :type haver-been mechanically driven through the `agency .of -iaecnank .and reduction wearing, and .the motion produced .thereby is .i characteristically non-.uniform *..throughout the lengthiof .ithe stroke, with equal .up .and vdown .tstrokeispeed. f Another characteristic. ofithetav-l Ietage=mechanically:drivenuin-it.is that itoperates twith:a.relativelymfshortrast stroke.

@It -has .beenttound that .the maximum volumet- -ric pumpaeiciency ...at reduced .power cost, to- :gether with .greatlyreducedcwear .and breakage `of -1. the equipment,.iare...obtained .with:1;long, slow `estrokesief uniform :velocity 4.nrnongtthe.adn/an.- itagesainifavon.otthellongslow strokearetheiollowingz (.1.) `The `smooth,moreuniform :motion i.of'.-.plunger.and rodntendsto` reduce theiorrnation .oieemulsions (-12) rthere.` is.` less tendencyf'ior f gas zglock" within.:the...pump; (3) the plunger travel .necessaty to .maintain production-is yobtained with efeiwerstress .reversals .on ..-sucker.-.rods, reducing "rod breakage andi .pumping rinterruptions; (4) `,-.more.positivenralve aotionlandtbetter filling ,of the @pump onathetupstroke....usually Jesuits; and: .(5) turiaceeeduipment .usually shows less wear .and igreater-wpowerieconomy. i

-imheuseiof a. long,.. slowly-stroke iis-.panticularly izdesirabletin a-reasnhaving.I lowfpressure .oils sands wanti-small` dailytwell. fproductionmhere; in.. order to obtain the maximum amountoffrecovery.- convstantcfluid:levelsfandconstants rates `of :drainage r Y-through.tthe..san'd must be maintained Theioil :shouldme pumped-.atta ratez-.that .will assist in maintaining constant .and .uniforrn drainage Within .1 the. .areservoir.` sand, ...andgg to this end. .the .;pumping rcycle.l should .be adl'llstable-; to suitsthe .characteristics cof :.ethe individual ..wel1. V :.Thus, Wherezthetrate .of drainage. through :fthe formaf-.tion is low, along, slowiupstroke.andtaiastfdownstroke with the rods falling as fast asngravity uwill ipermitlis calledsforfmhereas .with..extremely .tviscousoiL han. appreciable length or2 .timer is. .1.efqui'red-ifor. thepumnplungentocomplete itsreturn fstreketand a moderately-2slowfdownstroke is nec- -essanyinorder-toachievemaximumfproduction .32 with-itstequal unand. .downstrokeispee iarliimly :beregulatedntosuitithe requirements of the .strole inone `direction ,at a .saor-ice in the efficiency lof the strokein the other direction.

i -The .long, constant .velocity stroke ,is alsmedvantageous lin .thefcase of a. -W e1l producing apr preeiablequantities.. of sand, since` it .greatly 1I- Q duces surges and agitation at the Well pumplsuc- .tion, Wh-ich. causes excessive quantities of sand 1tobeidraxvn intothapumnmechanism. hisgexcessive-intake forear-id. results inahindin U M y pump mechanism,..which ,necessitates .a. 1a,h0li0u S .andcostly pullingotthepump.

wThe disadvantages-of themechanical-ly urli/'941 end-offthe downstroke to .permit .the .rods to -stretoh V.outafrorntinertia;forces and thenf-to recover. .but instead, an immediate reversal ci ino.- tion resulting in .il'iighpeakstresses andil'eqlllit breakage .in the rod .string #It-hasvlongtbeen.-realizedthatthe smooth,...uni form action of hydraulic jacks as ideallysuitedtto `.the requirements of ...oil -well .pumpingehut the many attempts'whichthave :heretofore been-,made

- toapply-:themprinciples.of .hydraulic Aoperation to A`pumpingequipment havefiailedto... achieve commercial success because of their complexity,; .ini vltial cost,lack.of counterbalancing, and diiculty of servicing.

A `primary .object of the present invention, thereforef is to -provide a hydraulically operated uwell unit capable of delivering a long,.constant `velocity stroke atany.; desired. speed. so. as. tuv realize" the many advantages obtainablethereby, and having-:independent control. oveclthe. speed ,ot up andidowr-is'troketto.` suit the .individual .requirementsof a particular Well. object has .been achievedv by providing. a simple, :fool-proof .,hydraulicff aok which A operatively connected. to. a eounterweighted walking :.beam in a .manner whereby the v advantageous L .features of both elements are combined. -."I`1hus,a`ny proportion.. of

vthelweight oi the trod. string 'can be .counterl weightedto relieve the hydraulic.- iack oi^ exces- .sive loads, whilefthe s`rnooth, uniform actionof f thai-hydraulic. .j aok is imparted to fthe rod.. string to secure the-.most efficient pumpoperation.

Another object othe invention. is to .provide i al pumping unit f thattwilll bring the Vsuckersroclsto ifi-'he crank-driven beam-pu-mpingmnit, howevor xa-gradual Vstopat the endof. -.the:downstroke`,..re

3 gardless of pumping speed, and pause for any den sired length of time before starting on the upstroke, thereby eliminating rod whip and greatly increasing the service life of the lrods and boxes and also of the surface equipment.

4 24 into the casing head 25 of the well. The

Y polished rod 23 is attached to the usual string of 6 Another object of the invention is to provide a hydraulic pumping unit that is simple andv rugged in construction, positive in operation, extremely portable owing to its lighter weight,V lower in first cost than a mechanically driven unit of comparable capacity and stroke range; and capable of being readily serviced in the eld.

Another object of the invention is to provide sucker rods which are connected? to vai pump piston in the lbottom of the well. The'pump is operated in the Well known manner by oscillating the walking beam I4 to reciprocate the polished rod 23 and sucker rods, the counterweight I 6 serving to cou'nterbalance the weight of the l sucker rods. A bumper post 26 is mounted on the a hydraulic jack and valve gear therefor which Y is particularly adapted to the working conditions under which most oil well pumping equipment operates. This object is attained by connecting the hydraulic jack to a walking beam independently of the operating rod of the weil pump,

which enables repairs or other operations on the pumping equipment to be made without disturbing the hydraulic jack or its associated equipment.

Another'object of the invention is te provide a hydraulic jack embodying means for equalizing the discharge of exhaust fluid so as to eliminate hydraulic hammer in the jack.

Another object of the invention is to provide a low cost and simply automatically operated hydraulic jack unit that is' particularly suitable for operating the old standard end wooden walking beam, thus providing for efficient operation of these units which have been obsoleted by their high power requirements. v

Still a further object of the invention is to provideV a hydraulic jack having a novel and improved valve mechanism Vwhich is positive in its action and which is operated by motion of the piston and rod.

Other objects and advantages of the present invention will become apparent to those skilled in the art after consideration of the following detailed description of the preferred form there- `of,"reference beingv had to the drawings in which:

Fig. 1 is a side elevation of a pumping unit constructed according to the principles of my invention;

Fig. 2 is an enlarged, partially sectioned View through the hydraulic pump jack;

Fig. 3 is a sectional View taken along the line 3-3 in Fig. 2, showing the piston at the bottom vof its stroke;

Fig. 4 is a view similar to Fig. 3, but with the piston at the top of its stroke;

Fig. 5 is an enlarged fragmentary sectional view showing the initial operation in the opening of the Valve; c l

Fig. 6 shows a later stage in the operation of the valve; and Y Fig. 7 shows the valve in its fully open position. In Fig. 1 of thefdrawings, the reference numeral I indicates a supporting platform, upon which is mounted a Samson post I I braced by suitable struts i2. Journaled in bearings I3 at the upper end of the post for oscillatingY movement in a vertical plane is a walking beam I4' having a horse head I at one end and a counterweight I6 at the other end thereof.l The'horse head I5 is attached to the end of the walking beam by vertically spaced pins I1 and I8.and comprises the usual arcuate portion I 9 around which is trained a bridle 2U. The bridle is secured at its upper end to a saddle 2| and is secured by a clamp 22 to the upper end of a polished rod 23 Whcihextends through suitable packing Cil platform III and is positioned to catch the coun- Y terbalance I6 in the event of breakage of the -sucker rod line, thereby preventing damage to the equipment mounted on the platform.

The lwalking beam I4 is oscillated by means of a hydraulic jack which is indicated in its entirety by the reference-numeral 30. vThe jack comprises a cylinder 3I having a head or base casting 32 attached to one end thereof, and a cap 33 at the other end. A piston 34 is slidably disposed within theY cylinder 3l, -and attached to the piston is a tubular piston rod 35 which extends slidably through the cap 33. A packing nut Y is threaded into the end of the cap 33 and compresses packing material 4I to seal the piston rods against leakage. i

Mounted on the upper end of the piston rod 35 is a fitting 42 which is apertured to receive aV sleeve bearing 43. Extending through the sleeve bearing 43 and journaled for rotation therein is a pin 44 which is secured by suitable brackets 45 to the walking beam I4 at a point spaced outwardly from its axis of rotation.

The hydraulic jack 30 is supported at its'lower end on trunnions which project laterally from opposite sides of the base casting 32 and are `ournaled in bearing blocks 5IV bolted to `the platform I0. Fluid for operating the jack is introduced into the cylinder and exhausted therefrom through the trunnions, and to this end the base casting32 is provided with Yducts or

passageways

52 and 53 which communicate with the interior of theV cylinder and extend axially through the trunnions. The

passageways

52, 53 pass through the walls of the trunnions at their top surfaces and communicate with corresponding openings 54 inthe bearing blocks 5I,` said openings 54 being threaded at 55 to receive inlet and '

outlet pipes

55 and 51, respectively. Ring seals 69 prevent leakage of the hydraulic 'uid while permitting relative rotation between the trunnions and their bearing blocks. This arrangement of the

passageways

52, 53 opening radially through the peripheral surfaces of the trunnions 50 eliminates side thrust against the shoulder 46 which would otherwisebe produced if the passageways opened axially through ends of the trunnions, and provides a construction that is hydraulically balanced about the centerline of the cylinder 30.

The inlet pipe 56 is connected to thedischarge port of a pump 6I which is mounted on a suitable bracket 62 on the platform I0 and whichV is driven by an electric motor 63 or other suitable source of power. Fluid is supplied to the pump through a pipe 64 from a reservoir tank causes Vthesprl'ng |05 to be compressec'lV until a suiiicient spring load is obtained to overcome the `detent balls 80 and cause them to ride up on cam slope 19 to land 8|. Theskirt or piston section 15 on valve membery 1| prevents the bore 12"from being opened and .the pressure ,in cylinder 3| relieved until the. detent balls are completely up on the land 8| and spring |05 is compressed sufliciently to complete the tripping action. At this point, the valve member 1| cracks open, asV shown in Fig. 6, and pressure in the cylinder is relieved, causing the piston 34 to come to a stop. Energy stored in the deflected spring |05 then acts on the actuating rod 95, moving the latter kup sufciently to raise the valve member to its fully open position (see Fig. 7). As the bottom edge of the land 8| passes above the centerline of the detent balls 00, the latter advance against the inclined cam face 82, camming said face upwardly and so aiding the spring |05 in opening the valve member and thereafter yieldingly holding it open. The square shoulder 84 on valve member 1| limits the upward travel of valve in case of excessiveV load on spring |05. .t

With the valve 1| in its fully opened position, pressure in the cylinder 3| drops substantially to zero, and the piston 34 is pushed down to the bottom of the cylinder by the unbalanced portion of the weight of the sucker rods.

As the piston 34 approaches the bottom of the cylinder, piston washer V|06 engages the upper end of` tubular? member 96, forcing it down to close valve 99 and then pushing the valve member 1| down untilY the skirt 15 enters bore 12. During this portion of the closing movement of the valve member 1|, the detent balls 8| are forced back into their holes by the cam face 82. As skirt 15 approaches bore 12, the fluid flow becomes increasingly restricted between the valve 1| and valve seat 13, thus causing the fluid pressure to build up in cylinder 3|, while the pressure at the lower end of valve 1| is substantially reduced, since the lower end of valve bore12 is now cut oil from pressure fluid through tubular l member 96 by the valve closure at 99, and is open to return not 'only via duct 9| but also around the valve' 1| to passageway 53. The hydraulic vpressure acting on the top of Vtlre'valve member 1| forces the latterV down to its fully seated position, with the detent balls 00 [bearing against cam surface 19. The jack is now in condition to begin the next working stroke.

The passage 9| and orifice adjusting screw 92 are provided for the purpose of slowly and controllably discharging the fluid trapped below thefvalve plunger 1| `during the downward travel of the latter from its fully open position atY least until'its skirt portion 15 has substantially entered bore 12, therebycushioning or damping the said downward travel of said valve plunger 1|. The purpose of this damping action is to slow the piston 34 to a gradual stop, regardless of its downward speed, and to provide a"dwell period at the bottom of the piston stroke, said dwell period being controllable bythe adjusting screw 92 which governs resistance to flow of the fluid which must be displaced from the bottom of the bore 12 in order to allow the'valve 1| to seat.V When Valve 1| does seat, its lower piston portion 83 has closed the passageway 9|, so that pressure iluid laterintroduced to the bottom of bore 12 via tubing 96 will not immediately escape.

It will be seen from the foregoing Vthat 'the flow offluid through tl'ie"'exhaust` duct' system is intermittentglandthat the column of fluid is subject to abrupt acceleration and deceleration which tends to produce hydraulic hammer in the system. In order to prevent the. occurrence of such hydraulic hammer, I have provided a tube ||0 which isV arranged alongsidethe cylinder 3| and extends from one end thereof to the other. The top end of tube 0 is inserted into a suitable projection on cap 33 and communicates with a passage I l2 which opens into the top of the cylinder. The bottom end of tube ||0 is inserted into a projection ||3.on base casting 32 and communicatesr with a passage ||4 which opens intov the outlet duct 53. The purpose of the tube ||0is to smooth out the ow of Vfluid through the outlet duct 53 by discharging fluid from the top of the cylinder on the upstroke of piston 34, during which period the Valve member 1| is closed and there would otherwise be no flow of fluid through the outlet duct. On the downstroke of the piston, the volume of fluid passing through the open valve 10 is the combined volume displaced by the piston on its'downward travel together with the volume entering the cylinder from the pump 6| through inlet duct 52, and the tube ||0 provides means for carrying a portion of this combined volume of fluid upto the top end of the cylinder to fill the void left by the downwardly moving piston 34. Thus, it is seen that the volume of fluid discharged through the outlet duct 53 on the up and downstroke of the piston is equalized to a considerable extent, eliminating the tendencyfor hydraulic hammer.

. The hydraulic jack shown and described here-l in is simple and rugged in construction, and the action of the valve 10 is positive. The construction is such that it is readily disassembled in the field, and the absence of small or delicate parts requiring precise adjustment eliminatesV one of the principal sources of trouble experienced with hydraulic pump jacks.

When it is necessary to pull the'string of rods or tubing from the well, the pump jack is eX- tended to the top of its stroke and stopped in this position.` The lower pin I8 connecting the horse head I5 to the walking beam |4 is' then withdrawn, and the horse head allowed to swing down about the pivot pin |1. In this position of the horse head, there is ample clearance for working on the rods and tubing without further dismantling of the pumping rig.

The speed of the upstroke is controlled by the delivery of the rotary pump which supplies the pressure fluid. This pump is directly connected to the power source, thereby eliminating the fire hazard of slipping V belts and the power lost through a V belt drive or other speed reduction means, and the output of the pump is regulated byan adjusting screw (not shown) on the bottom of the mounting flange. The pump is also provided with an Yoverload device whereby the delivery automatically becomes zero when the operating pressure exceeds a given value, as in the case of the well pump sanding up. The downstroke speed is controlled by the amount of counterbalance, Vand is regulated by increasing or decreasing the counterweight I6 on the walking beam. Thus, for a fast downstroke, the amount of counterbalance is decreased, while for a slow downstroke the amount'of counterbalance isi increased.

. While I have shown and described with some particularity the specific details of Vthe preferred form of my invention, it is to be understood that off rotation` thereof, a` source-of fiu-idpressure, Ainlet duct means-for carrying fluid from sa-id-L pressure-` sourceto oneend ofv saidcylinder'` through one ofr said trunnions, including a passage openingthrough the` peripheralwallofthe trunn-ion, discharge duct means-for carryingexl'iaus-ti fluid through the other ofsaidl trunnions` including,- a passage openingthrough the peripheral wall of the-trunnion, and valve means operative to close said: dischargel duct means duringtheworking `stroke of-r the pistonand toopensaid discharge duct meansduring-thereturn-stroke of' the piston.

2.` A Well pumping rig comprising-r` a counter*- `weighted Walking-beamsupported for oscillatory movement in;` a verticali* plane, means connectingsaid walkingbeamV to the` operatingrod'4 ofthe pump, ahydraulic-jack` comprising` a cylinder; a pist-on slidablyarrangedl within` the cylinder, and al pistonfrod connected tothe piston and togsaid walking beamat apoint spacedT outwardlyfrom the a-Xis ofi rotation thereof, asource of fluid pressure, inletl duct-means connecting-said source offpressure Withthel bottom endof said' cylinder,A

outlet duct means also-connected to said bottomend'- of the cylinder, valve-means-operative-to n close said outlet duct meansd-uring-the working stroke of the pistony andfto-lopen` the-same-during the-return stroke ofF the piston, and passage means connecting-the-top.end-rot said cylinder with-said outlet: duct meanswhereby` on the Working-stroke of the piston uidf 'displaced from said top end'- o fthe cylinder is` discharged into said outletduct means and' onv the return stroke ofthe pistona portionoftheconf-iloined'-` fluid' displaced from the bottom end ot' thecylinder-togetherwith the ilu-id; delivered by saidl inlet ductmeans` from said pressure source is conveyed'tothe-top of the-cylinder, the balance ofsaid fluidbeing discharged-throughsaid; outlet duct means.

3. A hydraulic jack of-'the type adapted to, deliver apower stroke` in one direction only, saidj'ack comprisinga cylinder having a headl atone end thereof, a piston slidable- Within said cylinder and having a pistonrodL connected thereto, inlet duct .means i communicating with the head end Qf said cylinder and= adaptedi for connection tc asource of uid pressure, valve means including a `closed-end cylindrical bore in saidJV cylinderhead'J havingits,l axis paralleli tov the axisof I the cylinder, a valve member slidablewithinsaid bore between open; and closed positions, outlet ductmeans communicatingwith? said bore, said valve member being shaped intermediate its ends to provide a pathfor theflow of fluidi ffrcmsaid-A cylinderto-said outlet ductmeans. when the;yalvemembcr` is open position, a. passagewayv extending-` throug-h said` valve member from. one'end to the other, a valveactuatng rodi disposed within said passageway and having limited movement with respect there-- l0 to, said" actuatingrodfunctioningas a valve to close` said-passageway when in its lowermost position and-to open said-passageway when in its uppermost position, means on saidI piston operative to engage saidl actuating rod as the piston approaches the top off its stroke and to carry said rod" w-th it to the endy ofl the piston stroke, the initialmovement oi saidactuating rod acting to open saidpassageway in` the valve member to equalize the pressures on both ends thereof and continuedmovement ofthe actuating rod' acting to raise said valve member, to Qpenposition, and means-for holding said valve member open during the return strokeof-the piston.

4. A; hydraulicjack--ofthe type adapted to delivera power stroke in one direction only, said jack comprising a cylinder having a head at, onev endthereof-,- a piston slidable with-in4 said cylinderand having-- a pistonrod connected thereto, inlet duc-tmeans communicating with the head endofsaid cylinder and adapted for connection to aseurce-oiuid pressure, valve means including a cylindrical bore in said` cylinder head,lsaid bore having-a seat at its upper end, a valve member sli'dable within saidbore between open and closed positions, saidI valvemember having a face at its-upper end adaptedto bear downwardly on said-seat and a downwardlyY extending cylindrical` ski-rt portion arranged below saidiace, outlet duct means communicating with said bore, springbiaseddeten-t means for yieldingly holding4 saidv valve member in either openorclosed position, andvalV-e actuating means, Operable by movement of saidpiston dur-ing the end portion oiY its power str-oke to-shift saidvalve member to open position, said actuating means including a spring which is deflected by theforce required tov overcome said detent means inmoving said- Valve member-to a position intermediate said open and closed positions, said skirt functioning to c lose sa-idl boreand maintainoperatingpressure withinthe cylinder until said'- detent means has been overcome, said spring thereafter; supplying actuating forcetomove said Valve member the balance-oi? the distanceto-its fully opened position.

52 A well-pumping rig` comprising a supporting platform, a counterweightedwalking beam suppor-ted on said platform for-rocking movement in avertical plane; mea-ns connecting said walking-- beam to the operating rod Qi the pump, a hydraulic jackconnected to said Walking beam at a point spaced outwardly from` the pivot axis thereol'saidj ack having a pair o f laterally extendingtrunn-ions journaled on said supporting platform; a source of iluid pressure, inlet duct means for carrying fluid from said pressure source to saidjackthrough one of saidtrunnions, including a passage opening through the peripheral' wallofsaid` trunnion, discharge duct means for carrying exhaust iluiol` through the other of said trunnions includ-ing a passage opening tlirouglfiA the peripheral wall of the trunnion, and valvemeans--operative-to control the flow of flu-idf throughsaidy duct to actuate saidjack.

6-. A well-pumping rig comprising a counterweighted'K walking beam supported for oscillatory movement in a vertical plane, means connecting said walking beam' to the operating rod of tha pump, a hydraulic jack comprisinga cylinder, a piston slidably arranged within the cylinder, and a piston rod connected to the piston and to said walk-ing beam at a point spaced outwardly `from the axis ofV rotation thereof, a source ofluid pressure; inlet duct means connecting said source of' 'F5 pressure at the bottom fend of said cylinder, outlet duct means also connected to said bottom end of the cylinder, valve means operative to close said outlet duct means during the working stroke of the piston and-to open the same during the return stroke of the piston, and means for diverting part of the displaced fluid from the bottom end of the cylinder to the top end thereof during the return stroke of the piston and for discharging said diverted fluid from the top of said cylinder-into said outlet duct means during the power stroke of the piston. 7. A hydraulic jack comprising a cylinder and a piston slidable therein, a valve including a body having a cylindrical valve bore, pressure uid inlet means communicating with one end of said valve bore and also with one end of said cylinder, said one end of said valve bore having an out.- wardlyV facing valve seat therearound, a valveY plunger slidable in said bore between open and closed positions, said valve plunger having at one end a poppet valve element adapted to seat on said valve seat in said closed position, and having inwardly of said poppet valve element a piston element, and inwardly of said piston element a reduced section to permit pressure fluid flow into and longitudinally of said bore when said valve plunger is in said open position, iluid outlet means communicating withV said bore at a point spaced longitudinally thereof from said one end, and so located as to receive said fluid flow, yieldable spring-biased means for initially resisting movement of said valve plunger from said closed position to a position intermediate said closedand open positions, and valve actuating means interconnected between said piston and said valve plunger operable to move said valve plunger from closed to open position by movement of said piston during an end portion of its power stroke, said actuating means including a spring deflected during said end portion of said power stroke to establish an increasing force applied to said valve plunger to gradually overcome saidV spring-biased means and thereby move said valve plunger from said closed to said intermediate posi-n tion, and thereafter to quickly move said valve plunger on to said open position, said piston ele-- ment being of a length to maintain said valve bore closed during said travel of said valve plunger between said closed and intermediate positions but to separate from said valveY bore in said open position of said valve plunger.

8. A hydraulic jack comprising a cylinder and a piston slidable therein, a valve including a body having a cylindrical valve bore, uid inlet means communicating with one end ofrsaid valve bore and also with one end of said cylinder, a valve plunger slidable in said bore between open and closed positions, said valve plunger having a piston element movable into and out of said one end of said bore, and having inwardly of said piston element a reduced section to permit liquid flow longitudinally of the bore when said valve plunger is in said open position, fluid outlet means communicating with said bore at a point spaced longitudinally thereof from said one end and so located as to receive said liquid flow, yieldable spring-biased means for initially resisting movement ofsaid valve plunger from said closed position to a position intermediate said closed and open positions, and valve actuating means interconnected betwen said piston and said valveY plunger'operableto move said valve plunger from closed to open position by movement of said piston during an end portion of its power stroke, said actuating means including a spring deected during` said end portion of said power Vstroke to establishan increasing force applied to said valve plunger to gradually overcome said spring-biased means and thereby move said valve plunger from' said closed to said intermediate position, and thereafter to quickly move said valve plunger on to open position, said piston element being of a length to maintain said valve bore closed during said travelof said valve plunger between said closed and intermediate positions but to separate from said valve bore in said open position of said valve plunger.

9. A hydraulic jack comprising a cylinder and a piston slidable therein, a valve including a body havingl a cylindrical valve bore, fluid inlet means communicating Iwith one end of said valve bore and also with one end o'f said cylinder, said one end of said valve bore having an outwardly facing valve seat therearound, a valve plunger slidable in said bore between open and closed positions, said valve plunger having at one end a poppet valve element adapted to seat on said valve seat in said closed position, and having inwardly of said poppet valve element a reduced section to permit liquid flow longitudinally of the bore when said valve plunger is in said open position, fluid outlet means communicating with said bore at a point spaced longitudinally thereof from said one end and so located as to receive said liquid flow, yieldable spring-biased means for initially resisting movement of said valve plunger from closed position toward open position, and valve actuating `means interconnected between said piston and said valve plunger to move said valve plunger from said closed position to said open position by'movement of saidpiston during an end portion of its power stroke, said actuating means including a spring deflected during said end portion of said power stroke to create a force applied to said valve-plunger to overcome said spring-biased means and thereafter to move said valve plunger to said open position.

10. A hydraulic jack comprising a cylinder, a piston slidable within said cylinderand having a :central opening formed therein, a tubular piston rod attached -to said piston in communication with said opening, liuid inlet means for supplying fluid under pressure to an end of said cylinder, fluid outlet means for exhausting fluid from said end of said cylinder, a control valve disposed ccaxial with said cylinder between said fluid inlet and fuid outlet means and movable between open and closed positions, yieldable spring-actuated means VYfor initially resisting movement of said valve from closed to open position, an actuating rod connected to said valve and extending lengthwise of said cylinder through said tubular piston rod, a projection on the end of said rod distant from said valve, and a spring carried by said .piston Yand engagea-ble with said projection during an end portion of the power stroke of the piston, said spring being deflected during said end portion of said Apower stroke to create a force applied to said valve to overcome the resistance of said spring means and thereafter to move said valve quickly to open. position.

11. The subjectwmatter of claim 7, including also a pressure fluid passageway between the pressure uid inlet means and the other end of said valve bore, anda valve controlling said passage- -way movable between closed and open positions by said valve actuating means near the end of the power stroke of the piston.

12. The subject matter oaf claim '7, including also a pressure. fluid passageway between the pressure iluid inlet means and the other end of said valve bore, and a valve controlling said passageway movable between closed and open positions by said valve actuating means near the end of the power stroke of the piston, and closed by the piston during the return stroke olf the piston.

13. The subject matter of claim 7, including also a pressure fluid passageway between the pres sure fluid inlet means and the other end of said valve bore, a valve controlling said passageway movable between closed and open positions by said. valve actuating means near the end of the power stroke of the piston, and closed by the piston during an end portion oi the return stroke of the piston, and a restricted fluid discharge passageway between a point near said other end of said valve bore and said iiuid outlet means, said valve plunger including a piston portion which uncovers said last mentioned passageway in said e open yposition of said valve plunger, and closes said passageway as said valve plunger moves into its said closed position.

14. The subject matter of claim 7, including also a pressure fluid passageway extending through the valve lplunger between the pressure fluid inlet means and the other end of said valve bore, and a valve controlling said passageway movable between closed and open positions by said valve actuating means near the end of the power stroke `of the piston.

15. The subject matter of claim 7, including also a pressure iluid passageway extending through the valve plunger between the pressure fluid inlet means and the other end of said valve bore, a valve controlling said passageway movable between closed and open positions by said valve actuating means near the end of the power stroke of the piston, and closed by the piston dur-- ing an end portion oli the return stroke of the piston, and a restricted fluid discharge passageway between a point near said other end of said valve bore and said iiuid outlet means, said valve plunger including a piston portion which uncovnl ers said lastmentoned passageway in said operi position of said valve plunger, and closes said passageway as said valve plunger moves into its said closed position.

16. A hydraulic jack comprising a cylinder and a piston slidable therein, a valve including a body having a cylindrical valve bore, pressure fluid inlet means communicating with one end of said valve bore and also with one end of said cylinder, said one end of said valve bore having an outwardly facing valve seat therearound, a valve plunger slidable in said bore between open and closed positions, said valve plunger having at one end a poppet valve element adapted to seat on said valve seat in said closed position, and having inwardly of said poppet valve element a piston element, and inwardly of said piston element a reduced section to permit pressure iiuid flow into and longitudinally of said bore when said valve plunger is in said open position, fluid outlet means communicating with said bore at a point spaced longitudinally thereof from said one end and so located as to receive said fluid flow, valve actuating means interconnected between said piston and said valve plunger operable to move said valve plunger from closed to open position by movement of said piston during an end portion of its power stroke, said piston portion of said valve plunger being of a length to maintain said valve bore closed during a portion of the travel of said valve plunger from closed to open position, a pressure fluid passageway between the pressure fluid inlet means and the other end of said valve bore, and a valve controlling said passageway movable between closed and open positions by said valve actuating means near the end of the power stroke of the piston.

17. A hydraulic jack comprising a cylinder and a piston slidable therein, a valve including a body having a cylindrical valve bore, pressure fluid inlet means communicating with one end of said valve bore and also with one end of said cylinder, said one end of said valve bore having an outwardly facing valve seat therearound, a valve plunger slidable in said bore between open and closed positions, said valve plunger having at one end a poppet valve element adapted to seat on said valve seat in said closed position, and having inwardly of said poppet valve element a piston element, and inwardly of said piston element a reduced section to permit pressure fluid iiow into and longitudinally of said bore when said valve plunger is in said open position, fluid outlet means communicating with said bore at a point spaced longitudinally thereof from said one end and so located as to receive said fluid flow, valve actuating means interconnected between said piston and said valve plunger operable to move said valve plunger from closed to open position by movement of said piston during an end portion oi its power stroke, said piston portion of said valve plunger being of a length to maintain said valve bore closed during a portion of the travel of said valve plunger from closed to open position, a pressure iiuid passageway between the pressure fluid inlet means and the other end of said valve bore, a valve controlling said passageway movable between closed and open positions by said valve actuating means near the end of the power stroke of the piston, and closed by the piston during an end portion of the return stroke of the piston, and a restricted iiuid discharge passageway between a point near said other end of said valve bore and said iiuid outlet means, said valve plunger including a piston portion which uncovers said last mentioned passageway in said open position of said valve plunger, and closes said passageway as said valve plunger moves into its said closed position.

LILBURN S. BARKSDALE,

REFERENCES CITED The following reference-s are of record in the file of this patent:

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