US2837898A - Differential plunger type liquefied gas pump - Google Patents

Description

June 10, 1958 l P. M. AHLSTRAND 2,837,898

DIFFERENTIAL PLUNGER TYPE LIQUEFIED GAS PUMP Filed July 15, 1953 2 Sheets-Sheet 1 55 P ILLIP M.AHLSTRAND INVENTOR June 10, 1958 j AHLSTRAND 2,837,898

DIFFERENTIAL PLUNGER TYPE LIQUEFIED GAS PUMP I Filed July 15, 1953 2 Sheets-Sheet 2 INVENTOR PHILUP M. AHLSTPAND ATTORNE Unite DIFFERENTIAL PLUNGER TYPE LIQUEFIED GAS PUMP Phillip M. Ahlstrand, Kenmore, N. Y., assignor to Union Carbide Corporation, a corporation of New York Application July 15, 1953, Serial No. 368,099

11 Claims. (Cl. 62- 1) square inch and upwardly and which is efiicient in operation and avoids the difiiculties of gas binding and has other operating advantages.

The pump is adapted to be mounted with its cold operating end immersed in the'liquid in a supply chamber but having other parts and operating connections extending exteriorly of the chamber where suitable packing and sealing means may be provided and kept at a warmer temperature appropriate to their required functions.

A particular feature of the invention is the incorporation of a differential piston or plunger having a larger diameter portion which is hollow and an elongated smaller diameter portion extending therefrom, the larger hollow portion operating in the working chamber of the cylinder being provided with an arrangement of fluid ports, passages and associated valve means of a character whereby the liquid flow is always upward through the pump, the liquid being drawn in at the bottom and discharged at the top of the working chamber. The plunger is in effect, however, double acting and delivers liquid on both strokes. during the down stroke liquid flows upwardly through the lower hollow plunger portion and a proportion thereof is forced out the discharge line, and during the up stroke the liquid above the hollow plunger portion is forced out the discharge line and liquid flows simultaneously into the bottom end of the working chamber below the plunger. By making the cross sectional area of the larger diameter portion of the plunger with respect to the cross sectional area of the smaller diameter plunger portion in a ratio of two to one, the discharge rates for the two strokes are equal. tween the up and down strokes and there is a uniformity of flow and power requirement.

Also particular advantages reside in the ability to obtain faster priming and in the reduction of liability of gas' lock. As the liquid progressively enters the bottom and leaves the top without any reversal of direction of flow, the liquid readily purges any vaporized gas from the pumping chambers which contributes to faster priming and serves to carry off continuously any heat developed such as by plunger friction. The pump, therefore, not only is maintained at a lower uniform temperature but the addition of heat to the surrounding liquid of the supply chamber is avoided. With the flow as described the hollow plunger and its working cylinder assure a substan tially uniform constant temperature and the shrinkage is substantially uniform. This is in contrast to the condition in a normal single acting pump where there may be States Patent The pump load, therefore, is divided equally be- I Nice a considerable temperature variation from the top to the bottom of the plunger and a greater shrinkage occurs at the bottom making it necessary to provide greater clearance in the original assemblyof the plunger in the cylinder.

The pump also embodies an arrangement of self-lubricating liner parts for the cylinder and fiuid bleed glands and conduits which cooperate in reducing friction and generation of heat and wear and aid in maintaining a high efficiency and prolonging the life of the apparatus, and also contribute to the avoidance of gas lock.

The pumping apparatus also embodies a driving mechanism including a speed reducer and crank, connecting rod and cross head drive for two plungers combined and constructed to occupy a small space, to be of light weight, to permit vertical mounting of a drive motor above the pump,

to allow for easy removal and replacement of the pump plungers, and to provide adequate lubrication of the working parts while avoiding a hazard of lubricant contaminating the pump plungers particularly when pumping.

liquid oxygen,

Various other structural and functional features of advantage will be apparent from a more detailed description of a complete embodiment. The invention accordingly comprises the features of construction, combination of elements, and arrangement of parts, which will be exemplified in the construction hereinafter set forth, and the scope of the invention will be indicated in the claims.

Reference should be had to the following detailed description taken in connection with the accompanying drawings in which:

Fig. 1 is a vertical cross sectional view of a reciprocative piston pump including particularly the working parts thereof;

Fig. 2 is a detail enlarged cross sectional view of the lower end thereof showing a modified valve arrangement in the piston;

Fig. 3 is a fragmentary enlarged view taken on the line 3-3 of Fig. 1 showing particularly the discharge port;

Fig. 4 is a view looking upwardly from the bottom of Fig. 1;

Fig. 5 is a view in elevation of a complete combination showing a pair of the pumps mounted in a supply chamber and having a common operating means;

Fig. 6 is a similar view looking from the right in Fig. 5 with the shell of the supply sump broken away; and

Fig. 7 is a fragmentary cross sectional view of one of the anti-friction bearing bushings for a pump cross head.

Referring to Fig. l, the pump there shown includes a long pump cylinder or barrel 1% which is shown as made in a single continuous sleeve but which if desired may be made in two or more sections suitably joined together. The pump is of the immersion type and adapted tobe suspended in a sump as shown in Figures 5 and 6 and for that purpose the upper end of the pump cylinder is provided with a suitable supporting means which may comprise a plate 12 having an opening therein for receiving the pump barrel which has a flange 13 abutting the plate. The plate 12 and pump barrel 10 are secured together as by the application of welding at 14. The plate 12 is adapted to be supported on the top of the supply container in which the pump is immersed as will be described later. larly within the lower working chamber 15 thereof is a differential piston or plunger in having a lower portion of considerable length and of larger diameter 16a and an upper long portion of. lesser diameter 16b which also serves as a piston rod adapted to be connected to a suitable operating means.

The cylinder, both as to the working chamber part forv the lower plunger portion 16a and the upper part in which operates the plunger member 1612, is provided with Operative within the cylinder and particu diametral clearance may be, for example, about .003 to .005 inch. The upper sleeve sections 18, in effect, serve as guide bushings for the plunger member 16b. Preferably the liner sleeves or bushings are made initially in sections as shown and assembled in the pump cylinder and line-reamed in place. The outer end of the cylinder is provided with suitable packing for the plunger rod which may advantageously be of the type in general disclosed inthe patent to Patterson, No. 2,292,543. As shown in the drawings, the packing means includes a metal disk 20 screwed into the end of the cylinder sleeve ltlb abutting against the carbon sleeves. Located above disk 29 are a series of packing rings 21, three being shown, each comprised of graphite impregnated woven asbestos and desirably a small amount of loose graphite may be inserted between the rings. Above the rings 21 is a metal sleeve 22 having therein a cylindrical guide sleeve 23 similar in composition to that of the liners 17 and 18. The assembly is compressed into sealing engagement by an outer nut 24 threaded over external threads on the upper end of the, cylinder section 1%. The upper end of the pump, including particularly the packing means just described, is commonly referred to as the warm end of the pump and it is exposed exteriorly of the liquid supply container in which the lower end of the pump, referred to as the cold end, is immersed.

The lower end of the cylinder is provided with a closure means in which are embodied the suction or intake valve means, the closure including a plate 36 having a reduced diametral portion received within the lower end of the cylinder section 1611 and a flange portion seated on a shoulder in the lower end of the cylinder. The plate is held in position by a bottom annular member 31 threaded into internal threads in the bottom of the cylinder barrel, the annular member 31 having a central opening flared downwardly and outwardly for the free entry of liquid. The suction valve means may vary as to form but as specifically shown it includes five valve members 33 arranged symmetrically around the center point of plate 30 each having an upper conical head seated in a complementary opening in the upper surface of the plate, and each valve member 33 being provided with fluted guides for maintaining their position in the openings through the plate 30. The upward movement of the individual valve members is limited by a common stop means 34 comprising one or more circular disk spring plates secured on the upper end of a boss 36 by means of a set screw 37. In place of the cone type valves shown there may be employed a small ball type. Also, of course, a single valve instead of the multiple valve arrangement would serve the purpose, but the multiple valves have the advantage of obtaining larger flow with smaller pressure drop because the small valves are lighter than an equivalent single valve.

The portion of the plunger 16a of enlarged diameter is made hollow and is adapted to permit upward flow of liquid therethrough by having an open lower end, and fluid passages 40 at the upper end. Flow in the opposite direction, however, is prevented by means of a check valve located within the interior of the plunger, which in the specific embodiment shown is located at substantiallythe bottom end of the plunger. The construction in Figure 1 includes a ball 41 having a seat provided by the inlet fitting 42 threaded into the bottom end of the plunger. The ball is movable vertically in a sleeve 43 which may have longitudinal internal guide ribs 43a for the ball. A flexible bumper limits the upward movement of the ball comprising a skeleton disk 44 urged downwardly by a spring 45.

In addition to the effect of gravity, the ball check valve may also be urged to its seat by a suitable light spring. Such a spring is shown in the somewhat modified arrangement of Fig. 2. The spring 46 is mounted within a cage 47 inserted in the enlarged bore at the bottom end of the plunger and held therein by the snap ring 48. The outer nut 49 has fingers 49a extending within the cage 47 and serving as guides for the ball 41. In this construction the bottom carbon liner sleeve abuts against a ring 50 held in place by a snap ring 500.

The outlet duct 51 (Fig. l) is arranged to communicate with the port 52 through the cylinder wall and carbon sleeve 17 by any suitable connection which in the particular construction shown comprises a flanged pipe end 51a clamped against a flattened portion of the barrel by the ring halves 53 and 53a clamped together by bolts 54 (Fig. 3).

As shown, a fluid collecting gland and bleed vent is provided midway of the working chamber. This comprises a brass lantern gland 55 inserted between opposed ends of two sections of the carbon sleeve liners 17 and a coupling 56 threaded through an opening in the cylinder barrel providing a conduit communicating with the fluid collecting space in the lantern gland 55. The opening through the coupling 56 is adapted to communicate with the liquid space in the tank in which the pump is suspended. The gland 55 is adapted to vent leakage from either the upper or lower pumping chamber, and particularly is adapted to prevent leakage from the upper pumping chamber from gas binding the lower pumping chamber.

A similar gland and bleed or vent arrangement is provided at the guide bushings 18 for the plunger rod 161') comprising a lantern gland 57 inserted between sections of the carbon guide bushings. Any suitable outlet may be provided for the gland passages comprising in the construction disclosed a conduit 58 in the plate 12 communicating with a pipe 59 opening into the supply chamber in which the pump is mounted. The gland 57 is particularly adapted to vent upward leakage from the upper pumping chamber and prevent it from contacting the packing means.

Figs. 5 and 6 show an application of the pump comprising in this case two such pumps operated from a common operating means and forming therefore a duplex pump. As shown in these figures, two pump cylinders 10 are suspended in a tank 70 forming a supply container and fore chamber for the liquefied gas which in turn may be supplied from a main container through a suitable supply connection 71. The liquid is preferably delivered through pipe 71 under at least a slight head pressure which may be provided by having the main supply source somewhat elevated from container 70. The liquid level in container 70 is maintained at the point shown by an outlet pipe 72 leading to the gas phase space of the main container. The proportions between the pump and container may vary and likewise the specific location of the pump cylinder except that the working chamber at least of the pump should be completely submerged in the liquid.

The liquid pumped may be, for example, liquid oxygen, nitrogen or argon and accordingly it is at a very low temperature, but may be substantially at atmospheric pressure. However, it is desirable that the liquid at the suction valve be in a slightly sub-cooled state at least 2 or 3 below the boiling point for the pressure existing at that point. The container is, of course, heat insulated as indicated at 73, by means which should be of a highly ethcient type.

The pump cylinders are suspended in the container 70 by means of the attached plates 12 the rim portions of which are seated upon the edges of openings in top plate of the container 7% and held down by means of upper plates 81, clamped to the top plate 80 by screws 82. The pump discharge pipes 84 and 85 are shown as extending through the respective plates 12 through the medium of suitable coupling means and lead, as indicated at 84a and 85a respectively, to a common filter 86 having an outlet 87. A pipe connection at 88 may be utilized for the attachment of any desired element such as a safety valve or pressure gage.

The pump operating means includes a drive mechanism located in the housing 91 supported on plate 80. A rotary drive shaft 92 is mounted in ball bearings 93 and 94 and extends upwardly from the casing through a suitable oil seal 95 for the application of a suitable power drive to the outer end. A worm 96 on the shaft 92 meshes with a worm gear 97 secured on a crankshaft which extends transversely of the housing 91 and through the side walls, being mounted in tapered roller bearings and provided with an oil seal at each end not shown. Mounted on the external ends of the shaft are crank disks 98 and 99 provided with crank pins 100 and 101 respectively received in the upper ends of the respective pitmans 102 each pivotally connected at its lower end to a crosshead 103 slidably mounted on spaced guides 104. The crossheads 103 preferably have anti-friction bearing bushings for accurate sliding support on the guides 104. These bushings may be of the type indicated in the fragmentary cross sectional view of Figure 7 comprising generally a bearing cage 105 having balls 106 running in axial grooves connected at each end with return grooves, and having sealing means 107 at each end. Bearings of such type are well known and the present invention is not concerned with the specific details thereof. The matter of importance is the provision of free sliding movement and the presence of a minimum of lubricant. The bearings at each end of the pitmans 102 also preferably are of the ball or roller bearing anti-friction type. For example, the lower end of the pitrnan is shown as having a transverse pin with its laterally extending portions journalled in needle type roller bearings mounted in the crosshead. The provision of anti-friction bearings for the driving parts to the plunger ro-ds externally of the housing 91 which type of bearings require but a thin film of grease for lubrication avoids the falling of lubricant on the plungers which is particularly important where liquid oxygen is being pumped. The upper ends of the piston rods 16!; are connected to the corresponding crosshead 103 by suitable coupling means which may comprise e. g..a screw 117 extending from the end of the piston rod and threaded into the center of the crosshead. The pitmans 102 may hev made readily removable and the arrangement in general is such that the cylinders may be removed from the apparatus without the necessity of removing the gear casing 91. Although the crank pins are shown at 180 relation for clearness of illustration, they may advantageously be at 90. v

The lower half of the housing 91 forms an oil reservoir and since it is completely closed, and since the crankshaft extends through the housing walls at a point substantially above the oil level in the housing, all danger of lubricant dropping on the pump plungers is avoided. The internal bearings and gearing are lubricated preferably by pumping oil from the reservoir to the upper part of the worm shaft 92. While the oil pump could be located advantageously in the reservoir, it is here shown at 110 secured to the side wall of the housing 91 adjacent worm shaft 92. The pump110 is of the positive displacement type and is driven by a pair of bevel gears 111 and 112, one of which is mounted on the worm shaft and the other the reservoir and the tubing, an extended surface cooler may be interposed in the tube 114.

The'manner in which the pump functions and the flow of the liquid therethrough upon reciprocation of the plunger will be readily understood by reference to Fig. 1. Upon the upstroke from the position shown, liquid is drawn into the lower end of the working barrel below the plunger from the surrounding supply. The spaces within and above the larger plunger portion 16a will, during normal operation, be full of liquid and the liquid above the larger diameter portion will be forced out the discharge opening 52 upon the upstroke. Upon the return downstroke the inlet valves close and ball check valve 41 opens and liquid flows upwardly through the larger plunger portion 16a and a definite proportion of the liquid above the check valve is forced out the discharge opening 52. The proportion of liquid discharged will depend upon the ratio of the cross sectional area of the circle formed by the plunger portion 16a to the cross sectional area of the upper plunger portion or rod 16b. Preferably these areas are made in the ratio of two to one which results in equal discharge rates for the two strokes and a more uniform flow and power requirement.

The flow of liquid through the pump is in effect in a continuoussingle direction entering at the bottom and flowing upwardly and out at the top on both strokes,

and heat generated by plunger friction is continuously carried off in the discharged liquid. The arrangement including the vent means reduces the heat transfer from the outer packing means to a minimum and avoids adequately the phenomenon of gas lock and conversely enables the packing to be maintained sufiiciently warm to ensure a good seal and avoid excessive friction and wear. 1

Since certain changes may be made in the above construction and different embodiments of the invention could be made without departing from the scope thereof, it is intended that all matter contained in the above description or shown in the accompanying drawing shall be interpreted as illustrative and not in a limitingsense:

I claim:

1. In a reciprocative plunger pump the combination of a cylinder and a differential plunger of stepped diam eter reciprocative therein the respective lengths of the plunger portions of smaller and larger diameter being longer than the pumping stroke, said cylinder having walls defining a working chamber in Which the inner plunger portion of larger diameter is operative and a portion of means through the wall of said working chamber posiof which is mounted on the end of a pump drive shaft tioned at a point substantially midway of the length of said working chamber so that said vent remains covered by the plunger portion of larger diameter during operation for venting gas material tending to flow between the plungerportion and the working chamber wall toward the lower part of the working chamber.

2. In a reciprccative plunger pump for delivering low temperature liquefied gases the combination of a pump cylinder, a diiferential plunger reciprocative therein having aninner larger diameter portion operative in the cylinder chamber and a smaller diameter portion operative in an extension of the cylinder having'a correspondingly reduced bore, said larger diameter plunger portion having .a length which is longer than the pump-' ing stroke and at least as long as one-half the length of said cylinder chamber, inlet valve means communicating with said cylinder chamber at the inner end thereof, an outlet connection atthe opposite end of said cylinder chamber, said enlarged portion of the plunger having a longitudinal fluid passage therethrough and a valve means therein adapted to permit the flow of fluid from the inner end of the cylinder chamber to the outer end thereof but prevent reverse flow.

3. In a double acting difierential plunger reciprocative pump for delivering low temperature liquefied gases the combination of a cylinder and a plunger having an inner portion of larger diameter and a connected portion of lesser diameter, said cylinder having a working chamber in which the inner plunger portion of larger diameter is operative and a portion of reduced bore conforming to and adapted to receive the plunger portion of lesser diameter, said larger diameter plunger portion having a length which is longer than the pumping stroke and at least as long as one-half the length of said working chamber, a fluid discharge opening leading from said working chamber at the end adjacent said reduced bore portion, inlet valve means communicating with the opposite end of said working chamber, said plunger portion of larger diameter having a longitudinal fluid flow passage therethrough, and a check valve therein adapted to permit the flow of fluid therethrough in the direction only from said opposite end of the Working chamber, the cross sectional area of said larger plunger portion with respect to that of said portion of lesser diameter being substantially in the ratio of two to one whereby the fluid delivered through said discharge opening is substantially the same for forward and reverse strokes of the plunger.

4. In an apparatus for supplying highly volatile liquefled gas, a supply chamber for the liquid, an immersion pump including a cylinder mounted in said chamber, a differential plunger of stepped diameter reciprocative in said cylinder, connections for operating said plunger extending outwardly from one end of said cylinder to the exterior of said supply chamber the opposite inner end of said cylinder being at a lower level in said chamber, said cylinder including a working chamber in which the larger diameter plunger portion is reciprocative, and said cylinder having an upper extension of smaller bore in which the plunger portion of smaller diameter is reciprocative, a liquid discharge conduit extending from the upper end of said working chamber to exteriorly of said supply chamber, an inlet valve means at the lower end of said working chamber for controlling the admission of liquid from said supply chamber, said plunger having a longitudinal liquid flow passage connecting the upper and lower ends of said working chamber, and a check valve therein permitting liquid flow in the upper direction only. 7 a

5. In a fluid pump having a cylinder and a plunger reciprocative therein, an end closure for one end of said cylinder comprising a plate having a cylindrical portion fitting in'the end of said cylinder and a flange portion engaging with a shoulder on said cylnder end, means for clamping said flange against the shoulder, a plurality of valve openings extending through said plate and valves therefor each valve comprising a head portion movable outwardly into engagement with a seat in the plate and having a guide portion slidable in its corresponding opening.

6. In an immersion liquid pump having a cylinder and a plunger reciprocative therein with an inner end of said cylinder adapted to be located at a lower level in a liquid supply chamber than the outer end thereof, an operative connection to said plunger at the outer end, a closure plate for the cylinder inner end, a plurality of liquid inlet openings extending through said plate and a valve for each opening having a seat in said plate and movable upwardly to open position and a stop means suspended over the valves for limiting the open position.

7; In an immersion differential plunger pump for delivering highly volatile liquefied gas and having a cold end mounted within a supply tank thereof and a warm end extending from the tank, a cylinder having a Working chamber located at said cold end at a level below said warm end, a diflerential plunger having stepped larger and smaller diameter portions the larger diameter portion of said plunger being operative in said chamber with the smaller diameter portion extending outwardly therefrom, a guide sleeve means connected to said cylinder having a bore within which said smaller diameter portion has a sliding fit, a fluid outlet means communicating with said working chamber at the end adjacent said guide sleeve means, fluid inlet means for said chamber, a bleed port means in said guide sleeve means intermediate the ends connected to bleed escaping fluid back into the tank, and packing for said smaller diameter plunger portion located outwardly of said sleeve means at said warm end.

8. In an immersion reciprocative plunger pump for delivering highly volatile liquefied gas, a cylinder having a working chamber and an elongated sleeve portion extending therefrom adapted to be mounted within a supply tank of such liquid, a plunger operative in said working chamber having a long connecting rod extending outwardly through said sleeve, the outer end of such rod being adapted for connection to means for reciprocating said plunger, outer packing means for the connecting rod, said sleeve portion being lined with successive cylindrical sections of solid self-lubricating material the bore thereof being of a size to provide a sliding fit for said connecting rod, and a fluid collecting gland located between the opposed ends of a pair of said sections and having a bleed outlet adapted to lead to the interior of the supply tank.

9. In an immersion reciprocative plunger pump for delivering highly volatile liquefied gas and having a cold end mounted within a supply tank thereof and a warm end extending from the tank, a cylinder having a working chamber located at said cold end at a level below said Warm end, a plunger operative in said chamber, an elongated operative rod connection extending outwardly from said plunger, a sleeve connected to said cylinder through which said rod extends, a liner means for said sleeve comprising successive cylindrical sections of bonded carbon provided with a bore within which said rod has a sliding fit, a fluid collecting gland inserted between a pair of opposed ends of successive sections and having a fluid bleed port means connected thereto, and packing for said rod connection located outwardly of said gland at said warm end. 7

10. In an immersion reciprocative plunger pump for delivering highly volatile liquefied gas, a cylinder having a working chamber portion adapted to be mounted Within a supply tank of such liquid and an elongated sleeve portion extending therefrom, a differential plunger having an inner long portion of larger diameter operative in said working chamber and a long portion of smaller diameter extending outwardly through said sleeve, the outer end of the long portion being adapted for connection to means for reciprocating said differential plunger, said Working chamber portion being lined with successive cylindrical sections of solid self-lubricating material the bore thereof being of a size to provide a sliding fit for the corresponding plunger portion, and a fluid collecting gland located between the opposed ends of a pair of said sections and having a bleed outlet adapted to lead to the interior of the tank the relation and proportions being such that the gland is at all times between the ends of the plunger portion of larger diameter during its reciprocation.

ll. An apparatus according to claim 4 in which the plunger portion of larger diameter has a length longer than the pumping stroke and which includes a vent through the wall of said working chamber located so that said vent is constantly covered by said plunger during its working stroke, said vent being adapted to prevent fluid leakage along the plunger from the upper to the lower portion of the pumping chamber.

References Cited in the file of this patent UNITED STATES PATENTS 10 Hall et a1. Nov. 23, Green Jan. 3, Okada Sept. 15, Okada May 17, Lee Dec. 16, Harlow June 9, Dana Aug. 11, Hansen Aug. 11, Warner Nov. 24, Drake Aug. 24, Ashton Nov. 14,

Hansen Nov. 28,

Anderson Apr. 20, Bonnaud Apr. 12, Riede Jan. 17, Lahoda Dec. 25,

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