US3431744A - Pump for liquefied gases - Google Patents

Description

March 11 1969 R. VEILEX ETAL PUMP FOR LIQUEFIED GASES Filed Oct. 4. 1966 INVENTOR5 ROBERT VEILEX PIERRE PARQUET BY @Me AGENT United States Patent O M 3,431,744 PUMP FOR LIQUEFIED GASES Robert Veilex, Paris, and Pierre Parquet, Rueil-Malmaison, France, assignors to North American Philips Company Inc., New York, N.Y., a corporation of Delaware Filed Oct. 4, 1966, Ser. No. 584,139 Claims priority, application France, Oct. 11, 1965,

34,515 Us. Cl. 62-55 7 Claims Int. ci. F171) 7/02; Fzsd 17/00 ABSTRACT F THE DISCLOSURE chamber, and an envelope housing surrounding an upper part of the pump outside the container, with provision for vapor of the liquefied g-as to fiow from the container and the second chamber into the envelope to further cool the pump.

It is known that liquefied gases are used on a large scale in industry, more particularly in the vacuum technique, for example for collecting, i.e. condensing, vapours of unwanted substances or, in a more ygeneral sense, of gases having a condensation temperature which is higher than that of the boiling point of the liquefied gas used as a coolant.

It is more advantageous to make this liquefied gas circulate in channels which are in contact with surfaces to be cooled, than having to store it in insulated vessels, the contents of which have to be supervised and renewed. For this purpose use is made of pumps which have been matched to the particular conditions of very low temperatures and easy evaporation of the liquids to be pumped.

In such pumps the liquid being pumped may partly evaporate due to the heat produced by friction between the piston and the cylinder, the heat supplied by conduction by the pump itself from its parts which contact the surroundings, and the heat which may be produced by compression of the liquid as it is flowing through the channels, The resulting gases interfere with satisfactory operation of the pump.

In known em'bodiments of pumps for liquefied gases the aim is, on the one hand, lto limit the evaporation of. the liquid and, on the other hand, to facilitate the -removal of the gases produced by evaporation. To this end, use is made of either direct means such as the presence of an amount of clearance between the piston and the cylinder, which clearance limits the frictional heat and permits escapement of the vapour, or indirect means such as the use of an auxiliary member which places the liquid in the whole sysem under a certain pressure, resulting in a reduced evaporation thereof.

The pump for liquefied gases according to the invention h-as been designed for the direct feeding of a device with a cooling agent circulaing in it for collecting vapours or other devices intended to obtain or maintain very low temperatures from bottles containing liquefied gas which are sold commercially. The pump and its method of circulating liquefied gas according to the invention is distinguished from known pumps by a plurality of features which considerably limit the losses of liquid.

3,431,744 Patented Mar. 11, 1969 ICC The pump for liquefied gas, which gas is contained in a vessel, comprises a piston which is connected to a reciprocatable piston rod and which is housed with very small clearance in a pump body or housing which may be immersed in rthe liquefied gas and in which a valve system permits the g-as to be supplied into the pump body and pressed out of it and, according to the invention, it is characterized in that the pump includes two chambers which co-axially surround each other and the said piston rod, the first of which chamber communicates a one end with the pump body and at its other end with -an outlet which may be connected to a circulation system for the liquefied gas present outside the pump, and the second of which has, at one end, at least one aperture through which it communicates with the-said vessel and has, at its oher end, an inlet which may likewise be connected to the circulation system present outside the pump and also an outlet which is situated above the inlet and empties into the atmosphere.

It is thus ensured that the liquid, after having been supplied to the first chamber, flows on without any appreciable pressure being required therefor. In the pump according to the invention, amounts of evaporated liquid may be removed due to the presence of the outlet of the second chamber, without any clearance between the piston and the cylinder being required. Such clearance would considerably decrease the efficiency of the pump.

Before flowing through the circulation system present outside the pump, the liquid fiows through the first chamber which is cooled by liquid flowing back from said system into the second chamber. This prevents the liquid present in the first chamber from being evaporated as the result of heat of conduction coming from without. This double-chamber construction also reduces the conduction of heat to the liquid in the container.

It is known that whatever precautions are taken thermally to insulate the various parts of such a pump from the surroundings, it is impossible to prevent the pumped liquid from partly evaporating and directly escaping through the seals of the pump to the exterior. It is therefore important to reduce as far as possible the number of seals required for such a pump. The pump according to the invention has two seals which bound a chamber in which the vapours of the liquid being pumped may be partly collected and heated so that in this chamber a certain pressure above atmospheric pressure arises which reduces the loss of vapour leaking to the exterior.

The liquid being pumped evaporates in part as it flows through the circulation system present outside the pump and as it cools the walls contacted by it. After having flowed through the system, the liquid and the vapour are collected again. The liquid portion returns to the container Ifilled with liquefied gas through the second of the above-mentioned double chamber. The evaporate-d portion is led through the second outlet, which is situated at a suitable height, into a closed insulated chamber which surrounds the greater part of the section of the pump present outside the container with liquid. The cold vapour cools this section of the pump, thus reducing the temperature gradient between the parts of the pump located inside and outside the container and hence also reducing the losses due to heat of conduction to the interior. Such a construction also affords the advantage that this cold gas which has been produced by evaporation is very dry, resulting in cooling being obtained without the formation of ice on this part of the pump.

The metal used for the structure of the pump naturally has a thickness which is as small as possible in order to inhibit thermal conduction, but this thickness must vary with the mechanical forces occurring in the various sections. The metal must be strictly neutral relative to the 3 liquids being pumped. A stainless steel of the kind sold commercially under the name 18/8, which contains about 18% of chromium and 8% of nickel and has a thermal conductivity which is one of the lowest among the metals usually employed, may advantageously be used for this purpose.

A pump according to the invention may function without any lubrication of the parts contacting the liquid gas so that it is possible to use any arbitrary gas.

In order that the invention may be readily carried into effect, it will now be described in detail, by way of example, with reference to the accompanying diagrammatic drawing showing an embodiment of a pump which is very convenient in use since it can simply be immersed in bottles for liquid gas which are sold commercially.

FIGURE 1 shows a longitudinal section of a pump for liquefied gas which is partly immersed in liquefied gas present in an insulated container.

FIGURE 2 is a sectional view -on a larger scale of a section of the pump of FIGURE l.

FIGURE 3 is also a sectional view on a larger scale of the double chamber for the leaving and returning liquids and illustrates the manner in which the various tubular Iparts forming the pump are connected together.

To facilitate the description, the pump in the figures is subdivided into five sections indicated by I, II, III, IV and V.

FIGURE 1 shows that the pump having a housing of which the lower end is partly immersed in liquefied gas contained in an ordinary insulated bottle or container 2.

Section I (See also FIGURE 2) The lower part of the pump which is present in the liquefied gas comprises a piston 3 connected to a piston rod 18 and formed by the body of a ball type valve 3a having ducts 3b. The piston 3 is adapted to reciprocate in a cylinder 4 having a length which corresponds to the stroke of piston 3. The cylinder 4 is bounded at the bottom by another ball type valve 5 which is fixed in the cylinder by contraction.

Section II A stainless steel tube 6 of a comparatively small wall thickness, which constitutes the outer envelope of the pump, is fixed on cylinder 4 by contraction. The further component parts of the pump are mounted in tube 6, the separations between the various sections of the pump being obtained by separating rings provided at different levels. Thus, at the separation between sections II and III, the tube 6 is fixed by contraction on the outer surface of a ring 7 placed in the pump body at a height such that it projects above the level of the liquefied gas when the bottle 2 is completely filled. The contracted connection is obtained, for example, by driving the metal of tube 6 by means of a pressure roller M into a re-entrant part 7a of the ring 7 (see FIGURE 3).

Section Ill The ring 7 has a thinner part 8 (see the detail in FIG- URE 3) on which a tube 9 likewise of a comparatively small wall thickness is fixed by contraction, the tube 9 being secured at its upper end, likewise by contraction, on a thinner part 10 of a ring 11 which is identical with the ring 7. The tubes 9 and 6, the latter of which is again fixed on the outer surface of ring 11 via a groove and a re-entrant part, bound two co-axial chambers. The outer chamber which lies between the tubes 6 and 9 has near the ring 11, an inlet 12 which is soldered on the tube 6 and which may be connected to a circulation system (not shown) located outside the pump. The tube 6 in section III is provided with holes one of which, indicated by 13, is provided in the upper part above the inlet 12 and on which an outlet is soldered, whereas the other holes 14 and 15 are provided in the lower part.

Section IV The tube 6 which is secured, on the one hand, to the ring 11 and on the other to a ring 16 which constitutes a bearing and is provided with a stuffing box for the sealing round about the piston rod 18 forms another chamber on which an outlet 17 is soldered which is intended to be connected to the circulation system present outside the pump.

Section V This section comprises a chamber which is formed by the tube 6 around the piston rod 18 and which is closed at the top by a sealing bearing 19.

The piston rod 18 which transmits a reciprocating movement to the piston 3 is driven by an electric motor with transmission shown diagrammatically at 20.

The portion of the pump which is located outside the container 2 is insulated by a space 21 filled with heatinsulating material. For example, a polyamide is used for the walls of space 21 and a sponge polystyrene as the filling. The lower surface of space 21, which forms the supporting surface of the pump on the neck of the container, comprises an insulating ring 22 of which the edges contacting the tube 6 are bevelled as shown at 23 so that the heat-exchange between the tube 6 and the ring 22 remains limited.

The pump operates in the following manner: after having passed the complex of valves 3 and 5, the liquid in section II rises in the chamber bounded by tube 6 and piston rod 18 and in section III in the chamber bounded by tube 9 and piston rod 18. The liquid then leaves the pump through the outlet tube 17 after having passed the ring 11. Subsequently the liquid and gaseous media return through the inlet tube 12 to the pump from the circulation system present outside the pump. The liquid medium passes the chamber located between the tubes 6 and 9 in section III to be collected through the apertures 14 and 15 in the container 2. The cold gaseous medium escapes through the outlet 13 and fiows through the space 21 from which it escapes into the atmosphere.

Section IV of the pump contains fluid medium and a little gaseous medium which has been produced, for example, due to internal frictions. It is impossible to prevent said gaseous medium from penetrating the chamber of section V through the bearing 16. Part of this chamber contacts with the surroundings. If the bearing 19 seals said chamber sufficiently, a pressure slightly above atmospheric pressure will be built up in it due to the heating 0f the gaseous medium, resulting in renewed flowing in of said gaseous medium being inhibited to a considerable extent, so that the latter escapes through the outlet 17.

Of the two seals used in the pump the one, that of the bearing 16, operates in a cooled atmosphere and the other, that of the bearing 19 operates at a temperature which is substantially equal to room temperature. Owing to these different conditions polytetrafiuoroethylene may advantageously be used for the first seal and neoprene for the second seal. Neoprene provides a better seal than polytetrafiuoroethylene, but in the conditions here obtained the presence of the superpressure chamber weakens the imperfectnesses of the latter.

What is claimed is:

1. In a pump apparatus for circulating a fluid such as liquefied gas between a container and a system outside the container, the pump when upright including a housing which has a lower end immersible into the fluid in the container and defines by its inner walls a passage for said iiuid and for a piston driven reciprocally by a piston rod, the improvement in combination therewith comprising a sleeve mounted within the housing between the passage walls and the piston rod, thereby defining an outer chamber between said walls and the sleeve and an inner chamber between said sleeve and the rod, the outer chamber having an inlet and an outlet respectively in communication with said system and with the containers interior, the

inner chamber having an inlet and an outlet respectively in communication with the housings lower end for receivi ing liquefied gas therethrough from the container and with said system, the outer chamber having a supplementary outlet through which vapor of said liquefied gas in said outer chamber is fiowable to the atmosphere, the inner and outer chambers prevented from direct intercommunication.

2. Apparatus as defined in claim 1, wherein the piston fits closely within the inner chamber, thereby minimizing leakage of liquefied gas between the piston and housing.

3. Apparatus as defined in claim 1, wherein the liquefied gas entering and traversing the outer chamber cools the sleeve, the adjacent inner chamber, and the piston rod therein.

4. Apparatus as defined in claim 1, wherein the housing further comprises a third chamber through which the piston rod moves, this third chamber having one end defining a seal separating the third and inner chambers and a remote end separating the third chamber from the atmosphere.

5. Apparatus as defined in claim 1, wherein the container has an upper part through which an upper portion of the pump housing extends, the apparatus further comprising an insulated envelope secured to the containers upper part and surrounding said upper portion of the pump.

6. Apparatus as defined in claim 5, wherein the supplementary outlet of the outer chamber communicates with said envelope, whereby vapor from said outer charnber cools said upper portion of the pump.

7. Apparatus as defined in claim 1, wherein an intermediate part of said inner chamber is bounded at each end by a ring having a central aperture with clearance for passage therethrough of the piston rod and liquefied gas.

References Cited UNITED STATES PATENTS 2,018,144 10/1935 Mesinger 103-153 X 2,439,957 4/ 1948 Anderson 62-55 X 2,837,898 6/ 1958 Ahlstrand 62-55 X 2,855,859 10/1958 Petzold 62-55 X 3,145,629 8/1964 Gottzmann 103-153 X 3,181,473 5/1965 Duron 103-153 X 3,220,202 11/ 1965 Gottzmann 103-153 3,299,828 1/ 1967 Josephian 103-153 WILLIAM L. FREEH, Primary Examiner.

U.S. C1. X.R. 103--178

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