US3053436A - Vacuum pump - Google Patents

Description

Sept. 11, 1962 J. SEDLACSIK, JR

VACUUM PUMP Filed Oct. 2, 1958 mI-m' 2 Sheets-Sheet 1 INVENTOR JOHN SEDLACSIK JR.

Sept. 11, 1962 J. SEDLACSIK, JR

VACUUM PUMP 2 Sheets-Sheet 2 Filed Oct. 2, 1958 HEATER VOLTAGE SOURCE INVENTOR JOHN SEDLACSIK JR.

3,053,436 VAUUM PUMP John Sedlacsilr, In, Garfield, N.J., assignor to Interplanetary Research-Development Corp., Garfield, N.J., a corporation of New Jersey Filed (let. 2, 1958, Ser. No. 764,927 7 Clm'ms. (Cl. 230101) The present invention relates to improved method and means for obtaining high vacua in enclosed receptacles such as bulbs for incandescent lamps, vapor rectifiiers, X-ray tubes, electron discharge devices and the like, and is a continuation-in-part of copending patent application Serial Number 580,245, of John Sedlacsik, Jr., for High Vacuum Pump, which matured into Patent No. 2,855,- 140. Such means are further adapted for use in a variety of high vacuum processes such as vacuum distillation, vacuum dehydration, vacuum coating and the like. More particularly, the invention relates to diffusion and condensation pumps for producing high vacuum and particularly to diffusion pumps which use organic working fluids and especially organic working liquids, such as oil or other hydrocarbons which contain relative volatile substances.

Vacuum pumps have come into wide use in the art of exhausting containers, notably electronic discharge tubes and the like, to pressures of the order of a small fraction of a micron. Basically, such pumps make use of a stream of some vapor flowing through an orifice from a boiler, the orifice being so positioned that the vapor stream entrains gas molecules flowing from a container in which the vacuum is to be produced, and drives these molecules in the direction of a piping system issuing eventually into the atmosphere, the vapor itself being condensed on a properly cooled surface in the path of outflowing of the gases, and then being returned to the boiler for reuse. It is usually most economical to provide the ofl'take piping system with a so-called backing pump of the mechanical type which reduces the pressure at the outlet. from the pump proper. The pump itself is provided with a vapor jet, or a plurality thereof which operate in tandem or series with each other, so that the total pressure rise from the intake to the oiftake comprises a number of steps or stages.

Multi stage diffusion pumps are not in themselves new or novel but I have devised certain features which greatly improve the operation of these prior art pumps in a way which will be fully explained below. i

In this invention, the pump fluid is vaporized by heat and the vapors pass through a chimney in the pump casing to an umbrella jet, or a plurality thereof, associated with,

the chimney which directs the vapors in the reverse direction in the annular space in the pump casing around the chimney so that the gas from the chamber being evacuated is diffused into the stream of vapors leaving the jet.

The diffusion pump of this invention having as its object that of increasing the pumping speed, the inner wall of the high vacuum umbrella jet or jets is made to slope inwardly away from the inner surface of the pump casing. This is accomplished by shaping the chimney so that it has a constricted portion in the vicinity of the umbrella jet,

thus causing the chimney wall to slope inwardly and 3,053,435 Patented Sept. 11, 1962 downwardly away from the jet. This is said to allow the vapors issuing from the jet to expand inwardly toward the center axis of the pump and to take a general downward direction in the pump casing instead of spreading laterally when they leave the jet.

The principal objects of the invention are to provide means for obtaining a vacuum greater than the capacity of an ordinary pump, to employ the usual mechanical pump and to supplement the operation thereof with additional means for securing a higher vacuum, and to provide an apparatus and method whereby the evacuation may be obtained with a maximum efficiency so as to approach as near as possible a perfect vacuum.

A further object of my invention is a pump which has a high pumping speed, will produce high ultimate vacuum, and will work against a comparatively high backing pressure, and also is mechanically rugged and commercially feasible for factory and laboratory applications.

The diffusion pump is adapted to achieve extremely low vacuum required in numerous industrial processes. The core of the oil diffusion pump is a jet, housed in a sealed casing connected to a vacuum chamber. The jet is in effect a kettle with its own heating unit beneath an oil container at its base. Inside the sealed casing, it is surrounded by air. The oil is heated until it evaporates. The oil vapor molecules pour out through openings at various levels of the jet, strike the air molecules inside the pump casing and drive them into such concentration that they can be readily drawn away by a mechanical pump. Air molecules from the vacuum chamber take their place and are in turn pumped out until the low pressure goal'is reached.

The invention is defined with particularity in the appended claims and preferred embodiments are described in the following specification and shown in the accompanying drawing wherein:

FIGURE 1 is a sectional view representing diagrammatically an apparatus embodying the means and method of this invention;

FIGURE 2 is a modification of FIGURE 1.

FIGURE 3 is a section taken along lines 3-3 of FIG- URE 2.

In the specific embodiment of the invention, the reference numeral 10 indicates the vessel or other container which is tobe evacuated. For purposes of illustration, I have shown the enclosure for a container as being the particular vessel to be evacuated but it is to be understood that the vessel does not form a part of the present invention, the invention being adaptable for the evacuation of any vessel whether for radio, electric or other purposes. Sufiice it to say that the vessel to be evacuated 10 is provided with a neck 12. A coupling member 13 cooperates with the neck 12 to make a gas tight union with a main conduit or intake manifold 14 whereby communication between the vessel 10 and the mechanism about to be described is afforded.

While I have only shown one such vessel 10 as connected to the intake manifold 14, it will be appreciated and understood that as many more may be connected of the pump about to be described.

Numeral designates a vertically disposed cylindrical pump casing of a conventional pump. Same may be made of glass or metal and may be provided with a cooling jacket such as a water jacket 11 therearound having the conventional inlets and outlets such as 11 and 11" for the admission and discharge of the coolant employed.

The pump casing is provided with an integral gas tight base 22 and an integral cover or closure 24 at the upper end thereof by which connection to the chamber to be evacuated is made. The closure is provided with a centrally disposed neck or opening 26 for connection to the intake manifold 14 of the system to be evacuated by means of a coupling member 28.

The pump casing 20 is also provided with an integral discharge or exhaust conduit 30 which connects to a mechanical backing pump generally represented by 32. The backing pump is commonly referred to in the art as a rough pump.

Conduit 30 represents the high pressure low vacuum end of the pump and, as will shortly be observed, the exhausted gases pumped by the vapors are led thereinto and passes therethrough for eventual discharge into the atmosphere.

Numerals 40, 42 and 44 designate cylindrical chimney members which may be made of glass and metal and are mounted one above the other so as to be positioned coaxial with each other and so as to form an internal cylindrical chimney arrangement inside of and concentric with the casing 20.

The chimney arrangement illustrated shows a three stage diffusion pump and the members 40, 42 and 44 form freely demountable mating chinmeys stacked together in pumping relation to form a vapor-conducting means. The member is provided with an enlarged or flared base portion 46 which fits with a clearance within the lower portion of the pump casing 20 so as to form a narrow annular space 48 between the wall of the casing 20 and the member 40 for the flow of condensate in the annular space between the walls.

The lowermost wall of the member 40 is supported upwardly from the base wall 22 by means of spaced foot members 49 so as to provide communication for the oil between the annular space 48 between the wall of the easing 20 and the area within the area defined by the wall of the member 40 all for purposes as will shortly be observed. If desired, the feet above refer-red to may be replaced by notches along the lowermost edge of the member 40 whereby the flow of the pump fluid may be permitted with equally eflective results.

It might be appropriate to explain at this point that any suitable pump fluid, subsequently to be more fully referred to, may be introduced into the bottom of the pump casing through an inlet 21 from a source of supply thereof (not shown).

Member 42 is superimposed over member 40 and is of such dimension at its lowermost diameter by virtue of an annular outwardly flared skirt portion 52, as shown, as to be receivable over the uppermost extremity or peripheral edge of the member 40 in a more or less fixed nesting relation.

When superimposed, as aforesaid, the walls of the members 40 and 42 are held in spaced relation as to each other so as to provide a throat or jet means, subsequently to be referred to. That is to say, the skirts of the adjacent members 40 and 42 provide walls which slope outwardly from top to bottom in spaced relation so that vapors leaving the chimney, as will shortly be observed, may be directed downwardly and outwardly toward the inner surface of the pump casing in the form of an annular jet.

It will be understood however, that, if desired, the

members 40 and 42 may be held in spaced relation by other means, such as spacer strips or spiders, all to the end that the members are held in the desired spaced relation so as to provide the downwardly and outwardly projecting annular throat or jet.

Member 44 is similarly superimposed over member 42 and is held relative thereto by the outwardly flared edge 54 of the member 44 which nests over the upper peripheral edge of the member 42, as illustrated. A cap 54 having a lowermost outwardly flared skirt 56 is receivable on the top of the chimney member 44 and is maintained in the nested position illustrated.

If desired, the chimney assembly may be positioned concentric with and centrally of the casing 20 by means of a spider member 58 which is secured to the inner wall of the casing 20 and to which the cap 54' is anchored centrally thereof by any suitable means.

Conceivably, a vertically disposed tie rod (not shown) may be positioned along the central axis of the chimney arrangement between the spider member 58 and the base 22 for purposes of holding the components chimney arrangement in a rigidly fixed position relative to the easing 20.

By such superimposition of chimney components umbrella shaped jet nozzles 60, 62 and 64 respectively are formed between the members 40 and 42, the members 42 and 44 and the members 44 and 54, substantially as shown. The nozzles are adapted to pump in series when furnished with the actuating vapors of a pump fluid, all as will subsequently be observed.

The chimney members 40, 42 and 44 are each provided at the tops thereof with annular rows of openings 66, 68 and 70 respectively which open outwardly into the jet nozzles 60, 62 and 64 respectively provided between the spaced portions of the adjacent chimney members whereby egress of the pump fluid vapors is permitted.

A mechanical or electrical heating means generally represented by numeral is provided below the base 22 of the pump. The heating unit may be of any conventional type, too well known to necessitate a detailed description in this specification.

The member 80 is adapted to heat the body of pump fluid represented by 82 in the base or bottom portion of the casing 20, sometimes referred to as the boiler of the pump, to a temperature sufficient to cause a copious offflow of vapor. The vapor, represented by arrows "(1 passes upwardly into the chimneys 40, 42 and 44 passing through the openings 66, 68 and 70 respectively and into the jet nozzles 60, 62 and 64 respectively.

The general mode of operation of the pump structure follows: The pumping fluid which may be of any suitable material described in the art as useable in diflusion pumps is heated and the resulting vapor flows up from the surface of the fluid through the respective cylinders 40, 42 and 44.

As aforesaid, the upper ends of the cylinders are designed so as to cooperate with the vapors by admitting same through the openings whereby streams of vapor flow outwardly into the annular spaces or throats or jet nozzles surrounding said cylinders.

The structure is designed to fractionally distill the fluid in the bottom of the casing chamber and more or less selectively supply the different fractions to the different jet nozzles so that only the most phlegmatic constituents are admitted into the uppermost areas of the chimney arrangement, the more volatile constituents being directed to the lower stage jet nozzles.

The vapors, upon reaching the openings, are passed into the jet nozzles and are projected downwardly. They are thus reversed in their direction of travel and are projected outwardly as high velocity streams as represented by arrows b.

Said streams have the capacity of pumping in tandem or series entrained gases represented by the arrows c" coming into the member 20 through the conduit 14 from the body 10.

That is, the principal component of velocity of the vapor molecules is substantially parallel to the axes of the cylinders whereby the vapor molecules impart a similar velocity to any gases which they entrain.

As aforesaid, the gas molecules so entering the chamber of the casing are entrained by the downwardly directed vapor irom the jet nozzles and are impelled toward the next jet.

The vapors condense upon the cooled casing wall releasing the gas molecules which are then entrained toward the exhaust port by the next jet, the condensate draining down the inner surface of the casing wall through the annular space 48 and back to the boiler.

Though I have shown a water jacket 11 as providing the cooling means around the casing 20, the pump fluid may be otherwise condensed on the walls of the casing 20 as by air or other mechanical cooling means, all as may be desired. The pump fluid flows by gravity downwardly between the casing 20 and the members 44, 42 and 40 and thence back into the body of the pump fluid 82.

Pumped gases pass into conduit 31} and are removed from the system by the backing pump 32, connected therewith.

The umbrella like arrangement of the jet nozzles offers throat areas between the adjacent walls of the members 40, 42, 44 and 54- as shown whereby the working vapor expands when it reaches the expanding portion of the jet nozzles, all to the end that greater pumping velocity is obtained. That is to say, expansion of the working vapor does not ensue until the same reaches the throats of the umbrella like jet nozzles, at which time expansion takes place in a beneficial manner, degree and direction.

Within the casing 20 and disposed centrally thereof above the chimney arrangement, I position an annular discharge grid 100 which is held in fixed position relative to the Wall of the casing 20 by means of insulated member 1112. The grid is provided with a suitable lead wire 104 connected thereto at 106 by means of which a positive potential may be supplied thereto from a source (not shown). The lead wire 104 passes from the exterior of the casing 21) through a suitable sealing means to the interior thereof in a manner commonly employed in lamp and bulb work.

Another annular grid ring 110 is disposed within the casing 20 and surrounds the member an of the chimney. Same is supported relative to the wall of the casing 20 by means of insulated members 112.

Said grid 110 is provided with a suitable lead wire 114 connected thereto at 116 by means of which a negative potential may be impressed thereon from a source (not shown).

It will be here understood that, if desired, a negative potential may be impressed upon the grid 1% and a positive may be impressed upon the grid 111B.

Either alternating or direct current may be employed. If desired, the electrical charges may be pul-sated.

When it is desired to obtain the evacuation of a vessel, the initial evacuation may be first obtained by operating the oil pump and the final evacuation may be obtained by continuing to operate the oil pump and by simultaneously therewith establishing the electrical potential between the grids 100 and 110.

I have determined that by carrying on the operation in this manner and by this means an increased and improved high evacuation of the vessel is obtained.

Said increased evacuation rests upon the fact that the charging of the grids causes electrons to be emitted, which electrons are given a certain velocity by the positive (or negative) charge impressed. Said electrons are attracted toward the oppositely charged grid and as they do, they are caused to collide with the gas molecules and to ionize them. That is, they leave the molecules with a positive charge. These positive molecules operate in the intensely electrified field and are attracted toward the grid with a considerable velocity due both to their mass and to the high impressed charge. The great number of molecules moving toward the plate at the same time draws more gas from the vessel to be evacuated and thus obtain a higher vacuum therein.

By such ionization of the oil particles, an improved fine spray i provided all to the end that the exhausting process of the member 10 through the intake manifold is greatly improved.

A modification of the invention is presented in FIGURE 2, showing an arrangement wherein the overall function is substantially the same as that shown in FIGURE 1.

The modified pump 120 is shown having a pump casing 122 with intake and exhaust conduits 124 and 126 respectively. The intake conduit is coupled to the vessel 128 which is representative of the vessel or device to be evacuated. The exhaust conduit 126 connects the pump casing 122 through a backing pump 130 so that the vapor stream entrains gas molecules flowing from the container in which the vacuum is to be produced, and drives such molecules in a direction toward the exhaust conduit and the backing pump so that the molecules eventually enter the atmosphere as heretofore described in conjunction with the apparatus represented in FIGURE 1.

A neck 131 formed in the upper end of the vessel terminates in a sealer 132 which engages the electrode stem 133 to provide a hermetic seal therebetween. The upper end of the stem is shown connected to a high voltage source 134 and to ground 135, shown by symbol. The lower end of the electrode stem terminates in a cupshaped discharge electrode 136 having sharp edges or teeth 137. A ring electrode 138 is annular in shape and has a positioning stem {139 secured to one portion of the ring and extending into a recess 140 so that the recess will have a tendency to restrain movement of the ring 138. The ring electrode stem extends radially from the annular ring electrode opposite the positioning stem 141, which stem is secured to the pump casing 122 to hold the ring electrode in a plane normal to the axis of the pump casing 122. A chimney stack 142 has three cylindrical portions each axially aligned with the other and communicating with one another. The three cylindrical portions embrace a chimney lower portion 144, a chimney intermediate portion 146 and a chimney upper portion 1% With the three portions being of different diameters and being progressively larger in diameter from the top down. Each of the chimney portions have respectively an upper skirt 150, an intermediate skirt 152 and a lower skirt 154 with each of said skirts terminating in an outwardly flared edge 156, 158 and 160, respectively. Each of the skirts are connected to the respective upper portion of its chimney, with said upper portions each having a plurality of openings or ports 162, 164 and 166 formed therein with the upper skirt having a closed top or wall 168. The lower chimney has a lower cylindrical portion thereof spaced from the pump casing 122 and sealed therewith by an annular portion 170. The base portion of the sealer connecting the lower chimney with the easing has an annular base portion 172, with one portion of said base portion communicating with the inlet area of the exhaust conduit 1 26 while an opposite area of the base portion communicates with the return condensing passage means 174. The lower portion of the condensing passage 174 communicates with the base of the casing terminating in the flared base 176 of the pump casing The flared base has a heating unit 178 positioned therein with opposite ends thereof connected to terminals 179 and 181 which terminals are in turn connected to a source of voltage to provide electrical energy for energizing the heating unit. A pump fluid .182 is disposed in the lower area of the flared base 176 with the level of the pump fluid terminating approximately even with the lower area of the condensing passage 174.

A cooling jacket 186 is shown disposed above the casing 122 and functions in much the same manner as does the cooling or water jacket 11 shown in FIGURE 1. The

position of the cooling jacket 186 in relation to the skirt elements is merely representative and it may extend higher or lower than that shown to provide optimum efliciency in the condensing functioning of the multi-stage diflusion point. While a representative cooling jacket is shown, it is to be understood that other cooling means may be provided and the particular cooling jacket may be en tirely eliminated. The necessity of a cooling jacket and its characteristic will be determined by the desired results of the pump.

The inside diameter of the electrode ring 138 is preferably at least as large as the inside diameter of the cylindrical lower skirt 154. The aperture or diameter of the electrode is axially aligned with the lower skirt and positioned to be normally out of the path of the jet stream emitted from the lower annular jet nozzle which is provided by the lower skirt in conjunction with the lower chimney portion, said chimney portion being internally of and spaced from said ring electrode.

The operation of the device shown in FIGURE 2 is similar, in general, to that of the device shown in FIG- URE 1. One important diflerence is that with a device as shown in FIGURE 2, the condensate collects on the annular base portion 172 which is at substantially the lower level of the exhaust conduit 126 where it engages the lower chimney portion. The side of the annular base portion opposite to that of the exhaust conduit emerges into the inner or lower surface area of the condensate passage means 174 which communicates with the oil container area of the casing containing the pump fluid 132.

In the operation of the device shown in FIGURE 2, when the liquid or oil is heated until it evaporates, the heated oil vapor molecules rise through the various chimney portions of the chimney stack and pour out through the openings such as 162, 164 and 166 and flow downwardly to emerge through their respective annular jet nozzles. The oil vapor molecules strike the air molecules inside the pump casing and drive the latter so that they can be readily drawn downwardly by the mechanical pump action. Air molecules from the vacuum chamber take the place of those forced downwardly and are in turn pumped out of the pump casing. The condensate of the oil vapors collects on the annular base portion 172 and flows through the condensate return passage 174 and into the flared base 176 in the reservoir with the other fluid to be heated by the heating unit 178.

The multi-stage diffusion pump of FIGURE 3 provides a discrete return passage for the condensate from the jet nozzles directly to one area of the liquid reservoir. This is an arrangement different from that shown in FIGURE 1, wherein all of the fluid including the air from the nozzle 123 emerges through the same passage adjacent the electrode 110 in an annular arrangement. The arrangement in FIGURE 2 provides for separation of the oil vapor from the exhaust fluid flow or air, on opposed sides of the multi-stage jet nozzle evacuation device.

The upper electrode of the device shown in FIGURE 2 is disposed immediately above the upper chimney portion and is aligned so that the annular set of teeth is disposed substantially axially with the jet nozzle of the upper chimney portion. The annular nozzles are all positioned so that there will be three distinct annular jet streams each having a diflerent diameter nozzle, with all nozzles aligned to provide mutual assistance of the remaining jet streams in providing electrostatic motivation of the particles for increasing the evacuation of the system by employing the devices of the present invention.

FIGURE 3 shows the condensate return passage as having a unitary discrete passageway for returning the condensate to the heating unit pump fluid area in contradistinction to the multipurpose passageway between the electrode ring and the chimney 40.

From the foregoing, it wlll be seen that the method of improving the vacuum of a system includes, initially, providing some form of fluid flow through a diffuser or pump chamber. The oil or other liquid or fluid is heated and caused to flow through jet nozzles in a direction for entrainment with the aeroform fluid in motion in the system. The entrainment of the aeroform fluid with the vaporized liquid flowing through the jet nozzles increases the fluid flow to provide a jet stream of increased velocity. The vapors are condensed and the condensate is restored to its source. A high voltage source connected to a pair of electrodes charges particles of the jet stream. The polarity of the electrodes are such that the moving particles electrostatically charged move in the direction of the air stream to further increase the velocity thereof.

The present invention provides a method for mechanically and electrostatically increasing the velocity of fluid flow for improving the vacuum in the system by introducing ionizable gases in a jet stream and electrostatically charging particles in the jet stream and causing them to speed the movement of the jet stream to ultimately improve the overall vacuum.

While several embodiments of the invention have been illustrated and described in detail, it is to be expressly understood that the invention is not limited thereto. Various changes may also be made in the design and arrangement of the parts without departing from the spirit and scope of the invention as the same will now be understood by those skilled in the art.

What is claimed as new and desired to be secured by Letters Patent of the United States is:

l. The method of increasing the degree of evacuation of a system comprising, providing fluid flow of aeroform fluid in the system, creating vapor and directing same to entrain said aeroform fluid and generate a jet stream of increased velocity, and electrostatically charging particles of said jet stream to facilitate movement thereof in a direction and of a velocity to further increase the velocity of said jet stream, whereby the pressure is decreased and the vacuum of the system is improved.

2. The method of increasing the degree of evacuation of a system comprising, providing fluid flow of aeroform fluid in the system, heating a liquid and creating vapor directed to entrain said aeroform fluid and increase its rate of movement to generate a jet stream of increased velocity, and electrostatically charging particles of said jet stream to facilitate movement thereof in a direction to further increase the velocity of said jet stream and improve the vacuum of the system.

3. The method of increasing the degree of evacuation of a system comprising, providing fluid flow of aeroform fluid in the system, heating a fluid to create vapor and directing same to entrain said aeroform fluid and generate a jet stream of increased velocity, condensing the vapor and removing same from said jet stream, and electrostatically charging particles of said entrained aeroform fluid to facilitate movement thereof in a direction to increase the velocity of said jet stream and improve the vacuum of the system.

4. The method of improving the vacuum of a system comprising, providing fluid flow of aeroform fluid in the system, heating a liquid to create vapor and directing same to entrain said aeroform fluid and generate a jet stream of increased velocity, condensing the vapor from the jet stream and restoring the condensate to its source for recycling, and electrostatically charging particles iOf said jet stream to facilitate movement thereof in a direction and of a velocity to further increase its velocity, whereby the vacuum of the system is improved.

5. The method of improving the vacuum of a system as set forth in claim 4, and wherein the electrostatically charged particles are polarized to permit movement thereof only in one direction.

6. The method of improving the vacuum of a system comprising, providing a primary air stream of aeroform fluid for evacuating the system, and simultaneously mechanically and electrostatically increasing the velocity of the air stream, whereby the pressure of the system is decreased and the vacuum of the system is improved.

7. The method of improving the vacuum of a system which employs a high velocity jet stream comprising, introducing ionizable gases for entrainment in said jet stream, electrostatically charging said ionizable gases in said jet stream with a given polarity and efiecting movement of said gases in a predetermined direction, said movement of said charged gases increasing the velocity of said high velocity jet stream to thereby decrease the pressure and improve the vacuum of the system.

References Cited in the file of this patent UNITED STATES PATENTS Ehret Oct. 16, 1928 Van der Pool May 14, 1929 Morse June 10, 1941 Hickman Mar. 21, 1950 Lawrance et a1 May 24, 1955 Alpert Oct. 8, 1957 Sedlacsik Oct. 7, 1958

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