US2465590A - Vacuum pump - Google Patents

Description

March 29, 1949.

Filed May 11, 1945 FIG. 2.

K. C. D. HICKMAN VACUUM PUMP 2 SheetsSheet 1 FIG.1.

KENNETH C.D.HICKMAN INVENTOR 107 BYW/M A '[TORNEYS March 29, 1949. D, ICK AN 2,465,590

VACUUM PUMP Filed May 11, 1945 2 Sheets-Sheet 2 mom SYSTEM 7 TO BE EVACUA TED FIG. 5. 146

KENNETH C. D.HICKMAN INVENTOR BYW M ATTORNEYS Patented Mar. 29,1949

VACUUM PUMP Kenneth C. D. Hickman, Rochester, N. Y., as

signor to Distillation Products. Inc., Rochester, N. Y., a corporation of Delaware Application May 11, 1945, Serial No. 593,129

7 Claims. (Cl. 230-101) This invention relates to improved multi-stage jet vacuum pumps of the fractionating type.

Fractionating muIti-stage jet vacuum pumps are known in the prior art; see, for instance, Hickman 2 080,421, May 18, 1937, Hickman 2,153.189, April 4, 1939, and Hickman and Kuipers United States patent application 443,732, filed May 20, 1942 (now Patent 2 379,436, July 3, 1945). Such pumps are provided with a plurality of boiler compartments connected to different jet nozzles and are adapted to use an organic fluid, and during operation to fractionate the organc liquid in the different boilers and arrange the components so that the low vapor pressure components exert their pumping action toward the low pressure side of the pump and the high vapor pressure components toward the high pressure side of the pump. I have noticed that the level of the liquid in the different boilers of such pumps as well as of multi-stage multi-boiler pumps in general is subject to great variation during operation. Thus, the boiler compartments are under different pressures and the liquid may, therefore, surge from one boiler into another resulting in an over supply of liquid in some boilers while other boiler compartments may have too little liquid. or may even boil dry. Obviously this has an undesirable effect on the pumping action.

This invention has for its object to overcome the foregoing dimculties. Another object is to provide improved multi-boier, jet vacuum pumps in which the liquid is maintained during operation at an approximately uniform or constant level. Another object is to prevent surging of liquid during operation of multi-stage jet vacurm pumps. A further object is to improve the operation of multi-jet vacuum pumps. A still further object is to improve the state of the art. Other objects will appear hereinafter.

These and other objects are accomplished by my invention which includes a multi-stage jet vacuum pump provided wih a plurality of boilers and with means for controlling the supply of working liquid to the boilers whereby surging and/ or unsatisfactory distribution of the liquid is avoided.

In the following description I have illustrated several of the preferred embodiments of my invention but it is to be understood that these are set forth for the purpose of illustration and not in limitation thereof.

In the accompany ng drawings wherein like numbers refer to l'ke parts,-I have illustrated several embodiments of my invention wherein:

Fig. 1 is a vertical section of a multi-stage jet vacuum pump of the condensation type provided with means for mainta ning a uniform level of liquid in each of the boiler compartments;

Fig. 2 is a fragmentary enlargement of the pump shown in Fig. 1 illustrating the construc--* by conduit 66.

tion of the means for maintaining a uniform level;

1 Fig. 3 is a fragmentary vertical section of a modification of the apparatus illustrated in Fig. l and Fig. 4 is a vertical section of a multi-stage jet vacuum pump operating on the principle of an ejector and provided with means for maintaining a uniform level in the individual boilers.

Fig. 5 is a, vertical section of a. multi-stage ejector pump provided with adjustable means for controlling the level and supply of pump fluid.

Referring to Figs. 1 and 2, numeral [0 designates a cylindrical casing provided with an integral base plate l2 and a flange l4 adapted to be connected in a gas-tight manner to the system to be evacuated (not shown). Numerals l8, l8 and designate concentric cylinders which rest upon the base plate l2 at the lower extremity, and which are provided with caps 22, 24 and 26 respectively which cooperate therewith to form jet nozzles 28. 30 and respectively. Numeral 34 designates openings through which vapors pass into the throat of jet nozzles 28, 20 and 32. Cylinder I8 is provided at the base with an outwardly flared portion 36 and a collar 38 which serves to make contact with the inside wall of easing l0 and space the cylinders l6, l8 and 20 in a position concentric therewith. Collar 38 is provided with a plurality of openings 40 for liquid to flow from the upper walls of IO into boiler 42 by way of openings 44 in the lower edge of cylinder l6. Numeral 45 designates an electrical heating unit mounted upon the base pate l2. Referring especially to Fig. 2, numeral 45 designates a float which is integral with arm 48 which is hinged at 50. To the float is attached a curved arm 52 which passes through a valve opening 54 which is closed or opened by valve seat 56 actuated by the float 46. Numeral 58 designates a similar float which actuates .valve 60 and serves to open or close valve opening '82. Numeral 54 designates a cylindrical reservoir which is connected to the space between cylnders l0 and [6 The upper portion of reservoir 64 is formed into a narrow cylindrical chimney -68 which protrudes into high-pressure arm 10 of the pump and is concentric therewith so as to form an ejector pump in cooperation with the walls of 10. Numeral 12 designates a pump fluid which assumes the approximate level shown when the pump is operated but which fills the reservoir to approximately the level indicated by the dotted line 14 when the pump is not in operation.

Referring to Fig. 3, numeral designates an annular gutter mounted upon the inside'wall of casing l0. Numeral 82 designates a conduit connecting the gutter 80 with the lower part of reservoir 64. Gutter 80 serves to collect liquid and deliver it to reservoir 64 where it is boiled and 3. fractionated and then the boiled liquid delivered to the boiler compartment 42 by way of conduit 66 lReferring to Fig. 4 'numeral 90 designates an ejector diffuser tube having a circular cross section provided with " et nozzles 92, 94 and 96. Numeral 98 designates a flange mounted upon the intake end of the ejector pump which is adapted to be connected to the system to b evacuated (not shown). Numeral I designates a conduit connected to the .high-pressure end of the diffuser tube which leads to the atmosphere or to a backing pump'(not shown) Numerals I02, I04 and I06 designate boilers connected respectively to jet nozzles 92. 94 and 95 by conduits H0, H2 and H4 respective y. Numeral II6 desi nates a float which actuates valve II8 of boiler I02 and numeral I20 designates a float which actuates valve I 22 of boi er I04. Numeral I24 designates a conduit conveying liquid collecting in the hi h-pressure end of the diffuser tube to the intake of pump I26. Numeral I28 de ignates a conduit conveying liquid from the exhaust pump I25 to the boiler I06. Numeral I01 designates heaters for the boilers.

Referring to Fig. numerals I40, I42 and I44 designate a purality of ejector pumps connected in series, the low pressure end I46 of pump I40 being connected to the system to be evacuated, (not shown) and the hi h pressure end I48 of pump I44 being connected by conduit I50 to a fore pump (not shown). The high pressure end of pump I40 is connected to the low pressure. or intake end of pump I42 by conduit I52 and the high pressure end of pump I42 is connected to the intake, or low pressure, end of pump I 44 by conduit I54.

Pumps I40, I42 and I44 are actuated by vapors delivered respectively to jet nozzles I56, I58 and I 50. Pump fluid issuing from these nozzles entrains gases and forces them into the high pressure end of each of the pumps in known manner. The pump fluid is condensed on the air cooled walls of the diffuser tubes of each of the pumps and flows by ravity into the high pressure ends of each of the pumps. The pump fluid then drains from each of the pumps into conduit I62, pumps I42 and I44 being provided with liquid traps I64 and I66. respective y. which prevent passage of gases backwards into the previous pumpin the series. Numeral I68 designates a gear pump which forces the working fluid flowing from the high pressure ends of each of the pumps through heat exchange coil I10 and thence into boiler- I12. which is heated by heater "4 and which supplies actuating vapors to je nozze I50 by way of conduit I16.

Numeral I'I8 designates an overflow conduit which is slideably mounted in gas-tight, packed gland I80, overflow li uid contained therein being forced by pump I82 through heat exchange coil I84 and thence through conduit I86 into boiler I88, which is heated by heater I90 and which supplies working vapor to jet nozzle I58 by way of conduit I92. Numeral I94 designates a slideably mounted overflow conduit which de- Boiler 200 is provided with a nozzle I56 by way of conduit 204. Numeral 20B designates a conduit connecting boiler 200 to an auxiliary boiler or purifier 208 which is provided with heater 2I0. The upper part of purifier 208 4 is connected to the upper part of boiler 209 by conduit 2I2.

In operating the apparatus illustrated in Figs. 1 and2, flange I4 is connected to the system to be evacuated and the backing pump is connected to the high-pressure side I0 in the usual manner and heating element 45 is put into operation. The mixed organic liquid 42 which may be a petroleum fraction, a diphthalic acid ester, etc., is thus vaporized and the vapors rise through vertical concentric tubes I8 and 20. Vapors pass through openings 34 and issue as high velocity jets through nozzles 28, 30 and 32. Gases diffusing from the system to be evacuated are entrained in-these high velocity jets and are forced downward into the high-pressure side arm I0. Reservoir I2 is likewise heated and the high velocity stream of vapors passes upward through 68 and entrains the gases from the lower portion of the pump casing I0 and forces them upwards into the high-pressure arm I0. The spent pump fluid is condensed on the walls of I0 and I0 and flows downward through opening 40 in collar 38 and thence through opening 44 into boiler 42. Some of this liquid also flows through conduit 66 into .boiler I2, where there is continual purification by vaporization with return of the useful components by condensation in the side arm 10. The liquid in the base of the pump flows in sequence from one concentric cylinder into the other. Thus, the liquid in the boiler 42 flows through valve 54 into the next boier compartment. The liquid then flows through valve 02 into the center .boiler compartment. As the liquid passes from one boiler compartment to the other it is fractionated and the lighterportion is distilled off and issues as vapor through the working jet of that particular boiler.

Valves 54 and 62 eifectively control the level of the liquid in the boilers and if properly positioned will maintain the level uniform in each of the boilers. comes depleted the float valve will sink, opening the valve and permitting additional liquid to flow therein. The height of the floats can be varied so that the level of liquid in the boilers will be the same or different, depending on the conditions desired. The level of the li uid in each boiler is thus maintained constant whereas in previous constructions it varied considerably, as explained above.

The operation of the modification shown in Fig. 3 is much the same as above described. However, gutter collects all of the spent pump fiuid and delivers it into reservoir 64 where it is first partially fractionated and is then returned to the boilers of the pump by way of conduit 65.

In operating the apparatus of Fig. 4, flange 98 is connected to the system to be evacuated and conduit I00 is connected to the atmosphere or to a backing pump, as the case may be. Reservoirs I02, I04 and I06 are filled with a suitable pump fluid, preferably a petroleum fraction, which should be of higher vapor pressure than that used in Fig. 1, as is explained in the above-mentioned Hickman and Kuipers' application. Boilers I 02,

I04 and I06 are then heated -by burners I01 to As the liquid in one boiler bea etc., may be used, if desired. and .this liquid condensate is withdrawn by pump I26 through conduit I24 and forced into boiler I06. As the level of liquid in boiler I04 is lowered float valve I22 is opened to permit additional liquid to flow therein.

into operation. Pumps I68, I82 and I96 are actu ated. Pump fluid in boiler I12 is vaporized and the vapors pass upwardly through conduit I16 and issue as a high veloc ty stream from jet nozzle I60. Gases in conduit I50 are entrained in this stream and are forced into the high pressure end I48 of the pump. The pump fluid vapors are condensed on the diffuser walls and flow by gravity through trap I66 and into conduit I62. Vapors from boiler I88 pass upwardly through'conduit I92 and issue as a high velocity stream from jet nozzle I58. Gases in conduit I52 are entra ned in this stream and are forced into conduit I54 and thence into pump I04, as previously described.

Spent pump fluid from pump I42 drains by gravity into trap I64 and flows into conduit I62. Similarly, vapors generated in boiler 200 issue as a pumping stream from jet nozzle I56 and entrain gases from the system to be evacuated and force them into conduit I62. Spent pump fluid is condensed and flows by gravity into conduit I 62.

The condensed and cooled pump fluid in conduit I62 is forced by pump I68 through heat exchange coil IIU where heat'contained in liquid flowing through conduit I84 is p cked up and used to preheat the liquid in coil I10. This preheated liquid then flows into boiler I12. Over flow pipe I18 is adusted to maintain the desired constant level of liquid in boiler I12. Liquid overflowing is forced by pump I82 through heat exchange coil I84 and thence into boiler I88. The more volatile constituents in the pump fluid have been removed in boiler I12 and the intermediate vapor pressure constituents are volatilized in boiler I88 and are used in jet nozzle I58. Over- 1 flow conduit I94 is adjusted to maintain the desired level in I88. Liquid overflowing is forced by pump I96 into boiler 200 where the lowest vapor pressure constituents are vaporized and are used in jet nozzle I56. Pumps I82 and I96 not only serve to transfer liquid from one boiler to another, as described, but also prevent passage of liquid in a reverse direction, which might otherwise take place with variations in pressure.

Pump fluids usually contain or generate nonvolatilizable or heavy products and these are segregated and retained in purifier 208. Thus, the liquid in 200 flows through conduit 206 into conduit 208, where it is heated by heater 2I0. Vapors thus generated pass through conduit 2I2' into boiler 200. Non-volatilized matter remains and collects in purifier 208.

supplied to the various boilers as described. With such a pump it would improve the pumping action in many'cases to use a lower temperature in the boiler supplying vapors to the lowest pressure jet and higher temperatures in the boilers supplying the jets working against higher pressures.

What I claim is:

1. A multi-iet vacuum pump adapted. to employ an organic liquid and in operation to fractionate the organic liquid by flowing it in sequence through a plurality of boilers arranged to distribute the components of the liquid in such manner that the low vapor pressure components exert their pumping action toward a low pressure pumping zone of the pump and the high vapor pressure components exert their pumping act on toward a high pressure pumping zone of the pump, the normal flow of said organic liquid through said boilers being from a higher pressure pumping zone to a lower pressure pumping zone, said pump including a plurality of boilers, liquid passageways interconnecting said boilers in series, and flow-controlling means associated with at least one of said boilers and comprising-valve means adapted and arranged to open and close a liquid passageway from said boiler, a float in said boiler, and a connecting member secured respectively to said float and said valve means and constructed and arranged to close said valve means upon upward movement of said float and to open said valve means upon downward movement of said float in response to changes in the sure pumping zone of the pump and the high condensation ganic fluids. Thus a multi boiler jet pump could a and the working fluid would be controlled and vapor pressure components exert their pumping action toward a high pressure pumping. zone of the pump, the normal flow of said organic liquid through said boilers being from a higher pressure pumping zone to a lower pressure pumping zone. said pump including a plurality of boilers. liquid passageways interconnecting said boilers in series, a valve in at least one of said liquid passageways interconnecting a boiler in a higher pressure pumping zone with a boiler in a lower pressure pumping zone. said valve being adapted and arranged to move from a position permitting flow of liquid through said passageway to a closed position, an actuating float disposed in one of said boilers interconnected by said passageway, a rigid connecting arm secured respectively to said float and said valve and constructed and arranged to close said valve upon upward move ment of said float and to open said valve upon downward movement of said float in response to changes in the liquid level in said boiler, and guide means for said floatlimiting lateral movement thereof.

3. A multi-jet vacuum pump adapted to employ an organic liquid and in operation to fractionate the organic liquid by flowing it in sequence through a plurality of boilers arranged to distribute the components of the liquid in such manner that the low vapor pressure components exert their pumping action toward a low pressure pumping zone of the pump and the high vapor pressure components exert their pumping action toward a high pressure pumping zone of the pump,the normal flow of said organic liquid 7 through said boilers being from a higher pressure pumping zone to a lower pressure pumping zone, said pump including a plurality of boilers, liquid passageways interconnecting said boilers in series, a valve in at least one of said liquid passageways interconnecting a boiler in a higher pressure pumping zone with a boiler in a lower pressure pumping zone, said valve being adapted and arranged to move from a position permitting flow of liquid through said passageway to a. closed position, an actuating float disposed in said boiler in said lower pressure pumping zone, a, rigid arm connecting said float and said valve constructed and arranged to open said valve upon downward movement of said float and to close said valve upon upward movement of said float in response to changes in the liquid level in said boiler, and guide means for said float limiting lateral movement thereof.

4. A multi-jet vacuum pump adapted to empoy an organic liquid and in operation to fractionate the organic liquid by flowing it in sequence through a plurality of boilers arranged to distribute the components of the liquid in such manner that the low vapor pressure components exert their pumping action toward a low pressure pumping zone of the pump and the high vapor pressure components exert their pumping action toward a high pressure pumping zone of the pump, the normal flow of said organic liquid through said boilers being from a higher pressure pumping zone to a lower pressure pumping zone, said pump including at least three boilers, liquid passageways interconnecting said boilers in series, flow-controlling means associated with at least one said boiler which is positioned between a boiler in a higher pressure pumping zone and a boiler in a lower pressure pumping zone and interconnected with said other boilers by said liquid passageways, said flow-controlling means comprising a valve positioned in one of said liquid passageways from said first-named boiler and movable from a closed position to an open position, an actuating float positioned in said firstnamed boiler, a rigid arm connecting said valve and said float constructed and arranged to move said valve toward said closed position upon upward movement of said float and toward said open position upon downward movement of said float in response to changes in the liquid level in said boiler, and guide means for said float limiting lateral movement thereof.

5. A multi-jet vacuum pump adapted to employ an organic liquid and in operation to fractionate the organic liquid by flowing it in sequence through a plurality of boilers arranged to distribute the components of the liquid in such manner that the loW vapor pressure components exert their pumping act-ion toward a low pressure pumping zone of the pump and the high vapor pressure comp nents exert their pumping acton toward a h gh pressure pumping zone of the pump, the normal flow of said organic liquid through said boilers being from a higher pressure pumping zone to a lower pressure pumping zone. said pump including at least three boilers. liquid passageways interconnecting said boilers in series, flow-contro ing means associated with at least one said bo ler which is positioned between a boilerin a higher pressure pumping zone and a boiler in a lower pressure pumping zone, said flowcontrolling means comprising a valve in the liqud passageway connecting said first-named boiler with said boiler in said higher pressure comprising a rigid guide arm secured to said float and pivotally secured to a wall of said boiler above said liquidpassageway.

6. A multi-jet vacuum pump adapted to employ an organic liquid and in operation to fractionate the organic liquid by flowing it in sequence through a plurality of boilers arranged to distribute the components of the liquid in such manner that the low vapor pressure components exert their pumping action toward a low pressure pumping zone of the pump and the high vapor pressure components exert their pumping action toward a high pressure pumping zone of the pump, the normal flow of said organic liquid through said boilers being from a higher pressure pumping zone to a lower pressure pumping zone,

o said pump including at least three boilers, liquid constructed to close said valve upon upward movement of said float and to open said valve upon downward movement of said float in respouse to changes in the liquid level in said boiler,

and a guide arm rigidly secured at one end to said float and pivotally secured at the other end to a side wall of the boiler.

7. In a multi-jet fractionating diffusion vacuum pump of the type adapted to employ an organic pumping liquid, a plurality of boilers, liquid passageways connecting said boi ers in series and opening into each said boiler in a zone thereof lower than the normal level of pumping liquid in said boiler, surge-controlling means for at least one of said boilers constructed and arranged to prevent objectionable surging of pumping liquid throughout said boilers, said surgecontrolling means comprising a valve in one said passageway opening into said boiler and movable from a closed position to an open position. a liquid actuated float disposed in said boiler, a rigid arm connecting said valve and said float, said arm being of suflicient length to maintain said valve in the open position when the liquid level in said boiler is normal, and a guide arm secured at one end to said float and pivotally secured to a wall of said boiler to limit lateral movement of said float while permitting vertical movement thereof in response to changes in the liquid level in said boiler.

KENNETH C, D. HICKMAN.

REFERENCES CITED The following references are of record in the

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