US2292375A - Method and apparatus for pumping volatile liquids - Google Patents

Description

Aug. 1l, 1942. o. A. HANSEN 2,292,375

METHOD AND APPARATUS FOR PUMPING VOLATILE LIQUIDS l Filed June 15, 1940 2 Sheets-Sheet 1 @dal mm ATTORNEYS Aug. l1, 1942. o. A. 'HANSEN 2,292,375

METHOD AND APPARATUS Fon PUMPING voLA'rILE LIQUIDS Filed June 15, 1940 2 Sheets-Sheet '2 Patented Aug. 11, 1942 ME'rHoDsAND.APPimA'rUs FOR PUMPING voLA'rILE LIQUIns I' v Odd A. Hansen, Kenmore, N.,Y., assignor to The Linde AirProducts Company, New York, N. Y., a corporation o1' Ollio Application June 15, 1940, serial No. 340,848- (ci. ez-1) N Y 18 Claims. This-invention relatesfto a method and apparatus for pumping avolatile liquid and particusure.

severaly steps andthe relation of one or more of such steps with respect to each of the'others,

and` the apparatus embodying features of con- More specifically, the invention has for its object thev provision of a cycle of pumping steps and apparatus for effecting the same whereby a volatile liquid, such as liquid oxygen, is. in eiect', cooled and then forced out by means of a vreciprocating plunger against a head of pressure in a manner which carries away and excludes the heat that may enter the liquid through conduction, and/or be introduced through friction. Such initial cooling practiced in the invention is here referred to as subcooling, i. e., the bringing of the liquid to a temperature for a given pressure below that of the equilibrium boiling pointl temperature of the liquid for such pressure. .The volatile liquid as a result may be pumped continuously without liability of experiencing the vaporization of the liquid within the pump or the pump becoming gas-bound.

Another object of the invention is to provide a reciprocating pump of the character indicated.

with parts arranged as far as practical to reduce friction and in a manner requiring the use of ,little or no lubricant of a composition that would tend to react with the liquid being pumped; such arrangement dispensing entirely with the use of piston rings, or similar liquid seals. l

Still another object is to provide a pump cylinder and plunger arranged in a manner which employs the principle of counter-movement of liquid and plunger in order to cool the' pump, whereby when the plungeris at the end of the discharge producing stroke, the liquid contacting end of the plunger is reduced in temperature to that of the liquid entering at the next suction stroke, thereby avoiding any ashing into vapor of the liquid being pumped.

Other objects of the invention will in part be obvious and will in part appear hereinafter.

The. invention accordingly comprises the struction, combinations of elements and arrangement of parts which vare adapted to eiect such steps, all as exemplied in the following detailed disclosure, and thescope of the invention will be indicated in the claims.

`For a fuller understanding of the nature 'and objects of the invention reference should be had to the following detailed vdescription taken inv connection 'with the vaccompanying drawings, in which: Fig.` 1 is a view,.partly in section and partly in elevation, showing an larrangement whichv effects the desired subcooling through static pressure and employs a reciprocating pump adapted for pumping the rvolatile liquid, here assumed to be liquid oxygen, in accordance with the invention; 'l v Fig. 2 is a similar view showing a modification `in which subcooling is achieved by means of expanding a portion of the liquid from the storagecontainer, in order to practice subcooling in the pumping cycle of the invention;

Fig. 3 is a similar view showing still another modification employing a subcooling effect;

Fig. 41 isfan enlarged sectional view showing details ofthe pump illustrated in Fig. 3; and

Figs. 5v and 6 show on enlargedscale details of parts employed to achieve antifriction bearings for working elements, such as cross-heads, connecting rods, and the like, employed in. the practice of the invention.A

- 1 The' pumping of volatile liquids which have boiling point temperatures materially below 273 K. at atmospheric pressure is taught broadly in U. S. Patent to Heylandt, Reissue No. 19,251, and

the exclusion of heat from the working parts is practiced, but since all metal parts have substantial heat conductivities, diiculty is at times ex,- perienced in keeping the pump from becoming fore pump to achieve'a gas-bound. This difficulty, however, is avoided` by the invention of H. E. Thompson, .in whose Letters Patent No. 1,930,731 is taught the use of two pumps arranged to operate in successive stages. Analysis discloses readily that th'e pump,

of the first stage delivers the volatile liquid being pumped to the second stage at a temperature suiiciently below the boiling point temperature corresponding to the pressure of the liquid being delivered, that heat leakage in the second stage is insuflicient to vaporize the liquid. 'I he liquid is thus in eiect subcooled, so that substantially any desired head of pressure may be readily achieved by means of a plunger pump where the liquid being pumped and the plunger are at temperatures below the equilibrium boiling point for the pressure applied; the pump structure being also arranged to conduct relatively little heat into the liquid being pumped.

In the arrangement of pumps taught in the Thompson patent, supra, it is, of course, important to have a connection between the rstand second-stage pumps with a relatively lowvpressure drop and a relatively low heat leakage, as this preserves the eifect o f subcooling introduced by the rst-stage, or fore, pump. Otherwise, the pressure rise provided by the mst-stage, or fore, pump will be neutralized and loss of prime in the second-stage pump will result.

By the presentinvention, the iirst step of the pumping cycle accomplishes the subcooling. This may be achieved in any suitable manner; for example, by elevating the storage container to a height that delivers the liquid to the pump at a pressure equivalent to the desired degree of subcooling; or by delivering the liquid from the storage container to the pump refrigerated during the passage by suitable means, such as by expanding a portion of the liquid while in heat conducting relation with the delivery conduit; or by directly increasing the supply pressure through the use of a fore pump, as taught in the U. S. patent to Thompson, above referred to. 'I'he head of pressure at which the volatile liquid is to be delivered to produce the effect of subcooling is, of course, materially less than the head against which the liquid is finally to be delivered.

As a second pumping step, the liquid under this initial pressure is introduced tothe pumping chamber of a reciprocating pump which has a plunger, devoid of piston rings, working in spaced relation to the side walls of the pump chamber whereby an appreciable clearance space is provided. Such introduction is preferably accomplished through an inlet valve placed so as' to deliver the liquid directly against the end of the reciprocating plunger when at the beginning of the suction stroke.

The next pumping step practiced is, of course, y

the iillng of the pump chamber, the reciprocating plunger being moved during the step to the outermost position at the end of the suction stroke. During this stroke, the liquid is not appreciably heated, but upon the beginning of the next. step the pump plunger is moved back and the exterior surface of the plunger now introduces some heat that has been generated in the plunger through frictional engagement with the packing.

The step thus begun accomplishes the displacement of the liquid from the pump chamber through an outlet valve. is connected to the pump chamber so as to communicate with the clearance space at a point remote from the inlet valve, whereby the liquid displaced does not pass out of the pumping chamber by a simple reversal of the direction of ilow but continues the flow inthe illling direction through the clearance space toward the outlet valve. The ilow of the liquid being displaced and the motion of the piston are seen at once to be in opposite directions and will be hereinafter referred to as the counter-movement of liquid and plunger. Since the clearance space is relatively small when compared with the total volume of the pump chamber, it is evident that the velocity of this counter-movement is relatively Here, this latter valve greatand also that all of the liquid being displaced necessarily over the surface of the incoming pump plunger. This cmmter-movement of liquid and plunger is seen, in consequence, to cool the incoming plunger. Advantage of this fact is taken in the practice of the invention to absorb the heat generated frictionally in the plunger so that when the plunger reaches the end of its displacing stroke it has been cooled to a temperature close to that of the incoming liquid. The size of the clearance space and the rate of displacement are factors which determine the degree of cooling. Accordingly, these factors are so proportioned that the counter-movement of liquid and plunger causes the absorption not only of the heat generated frictionally but also any'heat which passes by conduction down the plunger so that the likelihood of the next introduced liquid hashing into vapor is substantially avoided. The liquid, however, is' partially heated asit :s s through the pump and is then discharged at the desired high head to a receiver or vaporlzer for generating gas for industrial consumption. The practice of the present invention is thus seen to render harmless the heat generated by friction, which is unavoidable, such heat being absorbed by the liquid in passing from the pump.

Referring now to the drawings, and particularly to Fig. 1, Il denotes a storage container having an insulating. envelope Il' and adapted for holding a supply of the liquid to be pumped. Such container is here disposed at an elevation, in order to provide a gravity produced pressure to achieve the desired subcooling effect on the liquid being delivered to an inlet valve, shown generally at Il, at one end of a pump cylinder I2. This cylinder is arranged to have a reciprocating plunger, as shown at I3, working therein. The plunger is driven by any suitable means which may be mechanically coupled for imparting a periodic straight-line motion and utilizes substantially a minimum of lubricated parts. Accordingly, thel outer end of the plunger is shown connected to a transversely slotted crosshead Il that is actuated by means of a crank-pin I5 on a rotatably mounted disk I I; the latter being power-driven from any convenient source of power, for example, an electric motor I1.

Both the pump cylinder and the connections conveying liquid thereto are preferably thermally insulated, the presence of such insulation being indicated by broken lines in the drawings, the inlet connectionsbeing shown as provided with a liquid control valve i8. 'I'he pump chamber is shown at 2l within the cylinder I2 and is indicated as having a diameter in excess of that of the plunger in order to provide a clearance space thereabout (the clearance space being shown with greatly exaggerated dimensions for the purpose of cleamess of illustration inthe drawings). 'I'he outlet valve is shown diagrammatically at 2| located at the top of cylinder I2 to assist gas escape, the valve communicating with the space 2l through the cylinder wall at a point remote from the inlet valve il so that the incoming plunger may force the liquid displaced from the chamber 20 past .the end of the plunger through the clearance space without reversing the direction of flow, and then out through the valve 2l; this motion of liquid and plunger being the countermovement referred to above. From the valve 2l an outlet conduit 22 having a check valve 22 therein leads to a vaporizing coil 23. Thislatter may be connected to a service line 24 preferably initially or otherwise,a priming connection 26 isl provided, 'whichis insulated andy may with `ad vantage be connected to'theoutlet conduit 22 aty a point intermediate its connectionV to valve 2lvIn this form of the invention, the pump cylin-` der is shown provided with a packing space about the pump plunger in the end through which the plunger enters. A packing gland, shown generally at 29, is employed to close this space' and hold the packing, 'as shown at 28, `in place. The packing here employed is preferably of special construction, and where liquid oxygen is being pumped is of va character which avoids the use of a hydrocarbon or other liquid lubricant which may react with the liquid oxygen to form dangerous or objectionable compounds. A preferred form of packing'comprises one or more ring-like bodies of a suitable compressed material, such as shredded asbestos, lubricated with a solid lubricant in commin-utedl form, such as flake'graphite, as described in copending application, Serial No. 341,126, led June 18, 1940, in the name of J. F. Patterson.

In operation, the liquid delivered to the pump inlet valve, in this form of the invention, flows from the storage container I while under a' gravity head of pressure sufficient to effect the subcooling of the liquid to a desired degree. The motor at I1 rotates the disk I6 and causes the plunger I3 to reciprocate in the chamber 2l);

may with advantage lalso be iin-f atw2000 p. s. i. gauge,'for consumption in a conLv sumers distributing'l system' 'or vuse in industrial"r processes. 1- i* In Fig. 2,5a -modicationfis shown for achieve ing the effect of 'subco'oling -bymea'nsof the ex pansion of a portion of the liquid Withdrawn from a liquid" container which,` when'expanded--and` cooled', is passed in heat exchanging relation with the liquidsupplied to the pump. Any suitabley arrangement '-of this i character may be employed,

f for example, that' taught in U."S.` patent' to A valve 2-1 is also provided inthe De Motte, No. 2,033,094. yTo 'this end-, av conv tainer is shown, provided with a heat insulat-t ing envelope -3I and a liquid supply connection 32; A liquid withdrawal connection 33,having a T-connection r34 therein 'and a control valve at 35 i'sprovided leading to a pump cylinder 36 that has an outlet valve 31 located in the same manner, with reference to the cylinder clearance space, as shown at 2i in Fig. 1`. An outlet conduit 38 leads to a vaporizer 23', which may be similar to that at 23, and has an associated Agas distributing system for supplying gas to consumers. 'i

, A priming connection 40 for the cylinder 36 l. is also shown leading from a point in the outlet trolled by means of a valve, shown at 4I.

To achieve the subcooling eiect, a second connection 43 is led 01T from the T-connection at V34 and provided with an expansion va1ve'44, the

expanded gas` material beingpassedin countercurrent fashion through the heat exchanger 45.

which may comprise a. jacket as shown surround ing a portion of theconduit 33. Thelexpanded. 'gas material from the heat exchanger 45 pass s into'a coil 4B disposed about the container 30 and "thence through a heat exchanger 41 into a turbine pump 48 which discharges through la conpriming-being achieved, when starting, by opening valve 21. When the plunger is moved from the position when its inner end is at the extreme left in chamber 20, the suction stroke begins and liquid rushes in through the inlet valve to ll the chamber 20; any gas initially generated passing to the gas space in container I0 by Way of connection 26. The packing at 28 prevents any` liquid leakage, and, at the end of the suction stroke, the plunger is caused to reverse its direction and to begin a liquid displacing stroke by moving from right to left. This motion of the plunger produces the counter-movement of liquid through the clearance space in the chamber 20. As soon as primed, the valve 21 is closed land the ensuing discharge stroke, i. e., the stroke from right to left in the drawings, forces the liquid out through the valve 2l. The liquid rushing past the incoming plunger cools the same so that substantially all heat at a temperature higher than that of the liquid is extracted therefrom by the time the plunger has reached the end of its in- The liquid, partially nection 49 into the gas space of the container 30.

In operation, this modified form of pumping system is started by -opening the liquid supply valve 35 and the priming valve 4I and starting the plunger in pump cylinder 3G to operate. The suction stroke beginswhen the plunger is moved from left to right in the drawings, any gas initially generated-nding escape through the connection 40 into the gasspace of container 30. As soon :as priming .is'co'mpleted, the valve 4I is closed.

passed through -the heat exchanger 45, where,

because of its lower temperature, heat is extracted from vthe liquid passing through the conduit 33. The expanded gas material is withdrawn, continuously or intermittently as desired, by the turbine pump 48.. Valve 44 is maintained open during the operation of the pump in order to effect continuously the subcooling of the liquid supplied to the pump through the conduit 33.

In Fig. 3, another modification is shown, in

'plunger pump having a pump cylinder 55.

which a storage container 5l has an insulating jacket 50' and a liquid withdrawal connection 5l leading to the inlet of a fore pump 52, which is preferably of the turbine t-ype and has a rotary element for the pumping of the volatile liquid. While substantially any suitable turbine type pump may be employed at 52, the rotary pump disclosed in my copending application, Serial No. 345,308, led July 13, 1940, is advantageous. The rotary pump has a discharge connection 53 leading to an inlet valve 5I of a 'second-stage pump which is here shown as a vertical tghpe e vertically arranged cylinder not only permits the liquid withdrawal valve 51 to be at a higher elevation than the inletvalve whereby a highly positive action for withdrawing the gas from the clearance space within the pump cylinder is achieved, but also permits liquid remaining in the pump to be out of contact with the packing employed, since the inlet or cold end of the pump is lowermost.

An outlet conduit 58 leads from the valve 51 to a liquid receiver comprising vaporizer 23" that supplies an associated gas distributing system. A priming connection 6l leading from the gas space of container 59 has branches 5l and 50" leading respectively to the outlet connections of the rstand second-stage pumps. Branch il" is controlled by a vvalve 39 while branch il' is controlled by a valve 59.

The pump cylinder 55 is here shown as mounted in a supporting frame or casing 5l -that retains an insulating envelope about the pump; the pump cylinder 5B having working therein a plunger 62 and' a packing sleeve 63 through which the plunger protrudes. Here the plunger li2 is coupled mechanically at its outer end to means supplying power for reciprocatingly driving the same. The coupling employed preferably involves substantially a minimum of lubricated parts. To this end, a so-called "Watt linkage" is indicated and shown generally at 19. Such linkage comprises a floating link `|I that has its midpoint pinned or otherwise articulated to the upper end of plunger 62. This iioating link has one end pivotally attached to one end of a second link 12 that has its other end pivotally attached to a stationary part 6l of casing 6|. To the otherend of floating link 1I there is pivotally attached a walking beam 13 that is fulcrumed to another stationary part 55 of casing 5l. The beam 13 has an arm 13' extending beyond the casing 5l and has pivotally attached thereto a connected rod 14 that is coupled to a crank 'I5 on a shaft 15 that is provided with a driving wheel or pulley 11. This latter is advantageously connected to be driven from an electric motor 18 through a belt-drive 19.

While the pump cylinder here employed may be a single element, such as a casting, it is advantageously made of separate elements. An arrangement of this character particularly adapted for vertical working, as shown in Fig. 3, is illustrated on an enlarged scale in 4.

In the arrangement of Fig. 4, Il denotes a cylindrical elementwhich is adapted to provide theworking portion of the pump chamber. The cylinder 80 has attached at its top a second element 8| which closes the upper end of the pump chamberand has attached at its top a third element 82 comprising a hollow sleeve for the packing for the plunger 52. The elements Il! and 8| are here shown as secured together by threaded joints.

The pump chamber thus provided is here closed by means of a block-like element 9| attached at the lower end .and serving as a head for the cylinder 90. This block is counterbored and channeled to connect with a liquid supply conduit, such as shown at 53, the channel in the block being formed with an offset portion that has a valve seat at its junction with the initial portion. A gravity seating valve element 95 is arranged to rit on such seat and open under the impact of incoming liquid. The offset portion of the channel leads to the space in the counterbored portion of block 94 which is under the plunger i2 when in its lowermost position.

The clearance space between the plunger and inner wall of cylinder leads upwardly to an outlet connection 86 at the upper end of the pump chamber. The connection 96 leads into a casing element which has therein a valve seat controlled'by a valve 91. The pump outlet connection 58 leads from the casing element to a liquid receiving device at 23". A gland follower 99 closes the upper end of the packing sleeve and is adapted to hold packing rings, as shown at 99, in place. g

In operation, this form of the invention accomplishes the subcooling effect by means of the rst-stage or fore pump 52 which requires but a relatively small headof pressure on the liquid to start it. Starting is, of course, effected by opening the priming valve 59. When primed the valve 59 is closed, by which time liquid is being delivered to the inlet of the second-stage pump under a substantial head of pressure, for example, 50 to l'l0 p. s. i. gauge.

'I'he second-stage pump is set operating by starting motor 19.. To prime the pump at 56, the valve at 39 is opened. It is seen that when plunger 62 is moved upwardly a suction stroke is executed and liquid under the head of pressure supplied by the pump 52 flows through conduit 53 into the pump chamber and into the clearance space between the plunger 62 and the wall of the cylinder. When the pump is primed, the valve 39 is closed so that a downward movement of plunger 62 forces liquid to flow out through the conduit 58. The discharged liquid from this plunger pump is at a. relatively high head of pressure, for example, 2000 p. s. i. gauge.

The driving connections for reciprocating the plungers of pumps in accordance with the invention make use of substantially a minimum of lubricated parts. To this end, antfriction bearings are employed where working parts engage. Such a bearing is preferably inserted between the crank-pin l5 and the sides of the slot in crosshead Il. While ball bearings, and other types of antifriction bearings, may be employed here, a so-called needlebearing is preferred by reason of the negligible amount of lubricant required by it while being kept in proper working order. Such needle bearing is shown on enlarged scale in Figs. 5 and 6.

In Figs. 5 and 6, a needle bearing isshown on crank-pin I5. 'I'his bearing may have any convenient form, that shown comprising an annular channel or cage element 90 arranged to have its bottom fit over the pin I5. Such bearings are advantageous by reason of their relatively small size for a given load capacity. The channel has upset sides 9| which engage with the conical ends of a plurality of relatively small needle-like roller members r92. The surfaces of these needles provide rolling surfaces that engage with the sides of the slot in cross-head Il. Substantially no lubrication for such bearing, other than that introduced in the factory assembly, is required.

Certain other features of the. cylinder construction not specifically involved in the subject matter claimed herein are disclosed and claimed in my copending application, Serial No. 340,849, filed June 15, 1940.

Since certain changes in carrying out the above method and in the constructions set forth, which embody the invention, may be made without departing from its scope, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.v

Having described my invention, what' I claim as new and desire to secure by Letters Patent is:

1. The method of pumping a volatile liquid having a boiling point temperature not higher than 233 K. at atmospheric pressure against a relatively high head of pressure, which comprises bringing the liquid to be pumped into a state having a temperature which is below its equilibrium boiling point temperature corresponding to its pressure, introducing the liquid in said state at the suction end of a plunger pump in which an appreciable clearance space is provided between plunger and pump chamber wall, and displacing the introduced liquid from the pump by countermovement of liquid and plunger, whereby the liquid during the whole of said displacing step same.

2. The method of pumping a volatile liquid having a boiling point temperature materially less than 273 K. at atmospheric pressure against a relatively high head of pressure, which comprises bringing the liquid to be pumped into a state having a temperature which is below its equilibrium boiling point temperature corresponding to its pressure, introducing the liquid in said state at the suction end of a plunger pump in which an appreciable clearance space is provided between plunger and pump chamber wall, displacing the introduced liquid from the pump by counter-movement of liquid and plunger, and proportioning the rate f displacement and size of said-clearance space in a manner such as to cool the pump plunger when displacing liquid to a temperature such that incoming liquid is not ilashed into vapor.

3.`The method of pumping a volatile liquid having a boiling point temperature not higher than 233 K. at atmospheric pressure against a relativelyv high head of pressure, which comprises providing a liquid supply in a container arranged to give an initial pressure head less than said high head to whichthe liquid is intended to be pumped but equivalent to an appreciable degree of subcooling, supplying said subcooled liquid at the suction end of a reciprocating pump chamber which has a plunger spaced from the side walls of the chamber to provide an appreciable clearance space, priming said pump by venting to said container and displacing said liquid when introduced from said chamber by counter-movement of liquid and plunger.

4. The method of pumping-a volatile liquid having a boiling point temperature materially less than 273 K. at atmospheric pressure against a relatively high head of pressure', which comprises building an initial pressure head less than said high head in the liquid intended to be pumped to a value equivalent to an appreciable degree of subcooling, introducing said subcooled liquid at the suction end of a reciprocating pump chamber which has a plunger spaced from the side walls of the chamber to provide an appreciable clearance space, displacing said introduced liquid from said chamber by the counter-movement of liquid and plunger, and proportioning the rate of displacement to the size of the clearance space so that the counter moving liquid cools said plunger to a temperature which avoids flashing the knext introduced liquid into vapor.

5. The method of pumping a volatile liquid having a boiling point temperature materially less than 273 K. at atmospheric pressure against a relatively high head of pressure, which comprises vinitially elevating the pressure of the liquid supplied in a first-stage pump to a value for a state whose temperature is below its equilibrium boiling point temperature corresponding to its pressure, introducing said liquid at said elevated pressure at the suction end of a secondstage plunger pump in which an appreciable clearance space is provided between plunger and pump chamber wall, displacing said introduced liquid from said chamber by counter-movement of liquid and plunger, and proportioning the rate of displacement to the size of the clearance space so that the counter moving liquid cools said plunger to a temperature which avoidsA ashing the next introduced liquid into vapor.

6. Apparatus for pumping a volatile liquid having a boiling point temperature not higher than 233 K. at atmospheric pressure against a relatively high head of pressure, comprising the combination with a source supplying such liquid, of

means communicating with said source and prol viding .an initial head of pressure equivalent to an appreciable degree v of subcooling, a-pump having a cylinder with its suction endin communication with saidpressure providingmeangf afi ,plunger working in said cylinder arranged clear the inner wall of said cylinderand provide an appreciable clearane'space,l thereingfajdischarge connection vcommunicating 'with said clearance space at a point remotefrom saidsuction end and adjacent theen'd .of v the suction stroke, and means for actuating said plunger. 5

7. Apparatus for pumping a volatile liquid having a boilingpoint temperature materially*lessA than 273.K. at atmospheric pressure againsta relatively high headof pressure; comprising the combination with a source supplyingv such liquid,vv of means communicating with said source 'andproviding an initial head` of pressure equivalent to an vappreciable degree of subcooling, apump having a. cylinder with its suction end in communication with said pressure providing means, a plunger Working in saidjcylinder arranged to clear the inner :wall of the cylinder and provide `an appreciable clearance space therein, a.v discharge connection communicating with said clearance space at a point remote from said suction end, and means for actuating said plunger and'imparting straight-line reciprocating motion thereto; said last-named means being arranged to operate at a rate proportioned both to the size .of the plunger and to the size of said clearance named means being constructed of articulated elements havingantifriction bearings that require relativelylittle lubrication interposed between engaging parts. f.

9. Apparatus for pumping a volatile liquid having a boilingl point temperature materially less than 273 .K.` at atmospheric pressure against a relatively high head of pressure, comprising the combination with a source supplying v such liquid, of means communicating with` said source and providing an initial head ofpressu're equivalent to anappreciable degree of subcocling, a pump having ,va cylinder with its suction end in communication, with said pressure providing means, a plunger working in said cylinder arranged to clear theI inner Wall of the cylinder andv provide an appreciable clearance space therein, a discharge connection communicating with said clearance space at a point remote from said suction end, and means for actuating said plunger and imparting` straight-line reciprocating motion thereto; said last-fnam'ed means lbeing a Watt linkage and comprising a iloating link attached to said plunger, a supporting link for said floating link, a walking beam attached to said floating link and power applying means coupled to said walking beam. y

10. Apparatus for pumping a volatile liquid having a boiling point temperature materially less than 273 K. at atmospheric pressure against a relatively high head of pressure, comprising the combination with a source supplying such liquid, of a ii-rst-stagejrotary pump communieating with said source and arranged to discharge liquid with ahead ofA pressure equivalent to a desireddegree of subcooling, a second-stage pump' having a cylinder and a valve controlled inlet at its suction end connected to receive the subcocled discharge from said Afirst-stage pump, a plunger working in said cylinder and arranged to clear the inner wall of said cylinder and provide an appreciable. clearance space therein, a valve controlled discharge connection leading from said clearancespace at an'elevated point which is remote from said suction end, and means for actuating said plunger and imparting straight-line reciprocating motion thereto.

11. Apparatus for pumping a volatile liquid having a boiling point temperature materially less than 273 K. at atmospheric pressure against a relatively high head of pressure, comprising the combination with a source supplying such liquid, of a rst-stage rotary pump `communicating with said source and arranged to discharge liquid with a head of pressure-equivalent toa desired degree of subcooling, a second-stage pump having a cylinder and a valve controlled inlet at its suction end connected to receive the subcocled discharge from said rst-stage pump, a plunger Working in said cylinder and arranged to clear the inner wall of said cylinder and provide an appreciable clearance space therein, a

valve controlled discharge connection leading from said clearance space at an elevated point which is remote from said suction end, and means i'or actuating said plunger and imparting straight-line reciprocating motion thereto; said clearance space, the size or the plunger and the rate of actuation being respectively proportioned in a manner such that the counter-movement of-liquid and plunger operates to cool the latter to a temperature not substantially greater than that of the subcocled liquid.

12. Apparatus for'pumping a volatile liquid having a boiling point temperature materially less than 273 K. at atmospheric pressure against a relatively high head of pressure, comprising the combination with a source supplying such liquid, of a iirst-stage rotary pump communieating with said sourcev and arranged to discharge liquid with a head of pressure equivalent to a desired degree of subcooling, a vertically mounted'second-stage pump having a cylinder provided -with a valve controlled inlet at its lower end which is connected to receive the subcocled discharge from said first-stage pump, a

plunger working in said cylinder. and arranged to clear the inner wall oi' said cylinder and provide an' appreciable clearance space therein, a valve controlled discharge connection leading from the upper end of said clearance space, and Vmeans for actuating said plunger including a Watt linkage `whereby a straight-line reciprocating motion is imparted to said plunger.

13. Apparatus for pumping a volatile liquid having a boiling point temperature materially less than 273 K. at atmospheric pressure against a relatively high head of pressure, comprising the combination withfa container for supplying such liquid, of a first-stage pump disposed below said container a distance providing a desired head of pressure and arranged to discharge liquid at an elevated pressure providing a desired degree of subcooling, a second-stage reciprocating pump connected to receive the discharge from said firststage pump, priming connections for said pumps, each having control valves and leading from the outlets of said pumps respectively to the gas space in said container, and a liquid receiving device connected to receive the dischargefrom said reciprocating pump at a relatively high pressure.

14. Apparatus for pumping a volatile liquid having a boiling point temperature materially less than 273 K. at atmospheric pressure against a relatively high head of pressure, comprising the combination .with a container for supplying such liquid, of a. first-stage pump disposed below said container a distance providing a desired head of pressure and arranged to withdraw liquid from a point relatively close'to the bottom of said container, a second-stage reciprocating pump connected to receive theA discharge from said rst-stage pump, priming connections for each of said pumps, each having a control valve and each leading from the outlets of said pumps relatively to a common gas` space in said container, a receiving system including a liquid vaporizer, and a conduit leading from the outlet of said second-stage pump to said system and provided with a check valve.

15. Apparatus for pumping a volatile liquid having a boiling point temperature materially less than 273 K. at atmospheric pressure against a relatively high head of pressure, comprising the combination with a container for supplying such liquid, of a first-stage turbine pump disposed below said container a distance providing a desired head of pressure and arranged to withdraw from a point relatively close to the bottom of said container, a second-stage reciprocating pump connected to receive the discharge from said firststage turbine pump, a receiving system including a liquid vaporizer, a conduit leading from the outlet of said second-stage pump and provided with a check valve, and priming connections for each of said 'pumps comprising valved conduits communicating respectively with the outlets of said first-stage pump and said second-stage pump and leading from. a common portion to the gas space of said container.

16. Apparatus for pumping a volatile liquid having a boiling point temperature materially less than 273 K. at atmospheric pressure against a relatively high head of pressure, comprising the combination with a heat insulated container for holding a supply of such liquid, of a vertically arranged reciprocating pump having its cold end liquid and plunger, said pump and container being relatively arranged to provide a desired initial head of pressure, an outlet connection leading from said pump to a place of use, and a valved priming connection associated with said outlet and communicating with the gas space of said container.

17. Apparatus for pumping a volatile liquid having a boiling point temperature materially less than 273 K. at atmospheric pressure against a holding a supply of such liquid, of a first-stage pump communicating with said container at a point relatively close to the bottom of the same, a vertically arranged reciprocating second-stage pump having its inlet connected to the discharge of said first-stage pump and disposed with its cold end lowermost and provided with a plunger arranged to displace the withdrawn liquid by the counter-movement of liquid and plunger, an outlet connection leading from said second-stage pump to a consuming system, and priming connections for each of said pumps, each having a control valve and leading to the gas space of said container from the outlet connections of each of said pumps.

18. Apparatus forv pumping a volatile liquid having a boiling point temperature materially less than 273 K. at atmospheric pressure against a relatively high head of pressure, comprising the combination with a container for supplying such liquid, of a first-stage rotary pump disposed below and communicating with said container in a manner adapted to withdraw liquid from a point relatively close to the bottom thereof and with a desired degree of subcooling, a second-stage reciprocating pump having an inlet connection sufficiently short to avoid substantial heat leakage and of sufficient diameter to avoid a substantial `pressure drop connected to receive the discharge from said rst-stage rotary pump, priming conpumps to the gas space of said container, a liquid receiving and vaporizing device connected to the discharge of said reciprocating pump, and a cylinder filling device connected to receive the material in the gas phase discharged from said vaporizing device.

ODD A. HANSEN.

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