US2160863A - High vacuum - Google Patents

High vacuum Download PDF

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Publication number
US2160863A
US2160863A US147514A US14751437A US2160863A US 2160863 A US2160863 A US 2160863A US 147514 A US147514 A US 147514A US 14751437 A US14751437 A US 14751437A US 2160863 A US2160863 A US 2160863A
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United States
Prior art keywords
pump
sorption
gases
casing
conduit
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Expired - Lifetime
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US147514A
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English (en)
Inventor
Kenneth C D Hickman
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Distillation Products Inc
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Distillation Products Inc
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Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J9/00—Apparatus or processes specially adapted for the manufacture, installation, removal, maintenance of electric discharge tubes, discharge lamps, or parts thereof; Recovery of material from discharge tubes or lamps
    • H01J9/38—Exhausting, degassing, filling, or cleaning vessels
    • H01J9/385—Exhausting vessels
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04D—NON-POSITIVE-DISPLACEMENT PUMPS
    • F04D17/00—Radial-flow pumps, e.g. centrifugal pumps; Helico-centrifugal pumps
    • F04D17/08—Centrifugal pumps
    • F04D17/16—Centrifugal pumps for displacing without appreciable compression
    • F04D17/168—Pumps specially adapted to produce a vacuum
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J41/00—Discharge tubes for measuring pressure of introduced gas or for detecting presence of gas; Discharge tubes for evacuation by diffusion of ions
    • H01J41/12—Discharge tubes for evacuating by diffusion of ions, e.g. ion pumps, getter ion pumps

Definitions

  • This invention pertains to improvements in the production of high vacua and high vacuum pumps.
  • the well known Cenco Hyvac pump with a capacity of 100 cc. per second has an efflciency at the fly wheel of about .0038% at a pressure'of .01 mm., or taking the losses of the 1 horse power (200 watts) motor into consideration, an efliciency of, say,
  • An alternative method of producing high vacua is a condensation pump.
  • a pump of this type consuming 200 watts and having a capacity of 50 liters per second has an efficiency of .5% at .01 mm., and at the moderately high vacuum of 10 mm. the efficiency is only .005%.
  • This latter type of pump also has the disadvantage that pumping fluids of appreciable vapor pressure must be used.
  • This invention has for its object to overcome the above diiliculties of high vacuum production. Another object is to provide improved methods and apparatus for producing high vacua. Another object is to provide a high vacuum pump which does not require a liquid or vaporous opcrating fluid and which requires but little energy for operation. A further object is to provide a high vacuum pump which will enable the production of very high vacua and which operates on the principle of adsorption or absorption of gases.
  • the sorp- 10 'tion surfaces may be in the form of a drum, wheel, band, disc or any surface which can be alternately charged and discharged.
  • the drum, band or disc etc. may be composed of a material which has adsorptive or absorptive properties, or may be 15 constructed of a material which actsas a support for substances having such gas sorptive properties.
  • the discharge of the gases on the high pressure side of a pump can be effected in a number of ways, such as ionization caused by contact 20 with a high tension-electrode, or by heating such as by radiation, by high frequency heating, by electronic bombardment from a glowing filament, etc.
  • the term sorption or sorption surface will be used 25 as a generic term including both absorption and adsorption.
  • Figs. 1, 2, 3, and 4 are elevations in section of pumps having different types of sorption elements and illustrate various methods for discharging gases from the sorption surface.
  • Fig. 5 is an elevation in section of a pump having a disc -shaped sorption surface employing electrical resistance heating for discharge of gases.
  • Fig. 6 is a horizontal section of the apparatus shown in Fig. 5.
  • Fig. '7 is an elevation in section of a pump having a sorption surface made up of strands of sorbing material and illustrates the position of the sorption element during the sorption of gases.
  • Fig. 8 is an elevation in section of the same 941- 5 paratus shown in Fig. '7 and shows the position of the sorption element during discharge of the sorbed gases.
  • Fig. 9 is an elevation in section of a pump having a stationary sorption surface, and;
  • Fig. 10 is a vertical section on. line Ill-III of Fig. 9.
  • reference numeral l designates a cylindrical or drum shaped pump casing provided with conduit 2 which connects with the chamber to be evacuated and conduit 3 which connects to the backing pump and, which therefore, represents the low vacuum side of the pump assembly.
  • Reference numeral 4 designates a drum rotatably mounted upon a centrally located shaft 5. About the periphery of drum 4 is mounted a plurality of bristle-like appendages 6 which are constructed of material having sorption properties. for gases.
  • Reference numeral I designates a high voltage electrode so located that it comes into contact with bristles 5 when drum 4 is rotated and in that manner causes heating and electrical discharge of sorbed gases.
  • drum 4 is caused to rotate at any suitable speed depending upon the desired rate of evacuation and the backing pump connected to conduit 3 is put into operation. Gases diffusing from the chamber to be evacuatedinto conduit 2 are sorbed upon the surfaces of bristles 6 and are carried from the point of sorption to the high pressure side of the pump and are discharged by the electrode 1 and removed from the system through conduit 3.
  • reference numerals I, 2, and 3 designate a pump housing and conduits arranged in the same manner as described in connection with Fig. 1.
  • a rigid circular band I5 is centrally located within the housing I and is rotatably mounted upon rollers l6, one of which is driven.
  • Band I5 is constructed of a metal having sorptive propertiessuch as tungsten or molybdenum, or its surface is coated with a material, such as silica gel, alumina, active carbon or other material having such an action.
  • Numeral I I designates a discharge device which comprises a metal coil looped about the band l5 and which is connected to a high frequency cur-g rent by connecting wires l8.
  • gas diffusing from the chamber to be evacuated is sorbed onto the surface of. rotating band 15 and is conveyed to the high pressure side of the pump where the band is heated by device I! and the gases caused to be discharged. Gases are removed from conduit 3 by a backing pump connected thereto.
  • reference numeral 25 designates a pump housing provided with intake and withdrawal conduits 2 and 3 respectively.
  • Reference numerals 26 and 21 designate drum shaped members rotatably mounted on shafts 28 and 29 in such manner that the-surfaces are in light contact or in close proximity to each other. shafts 28 and 29 respectively and are connected together by lead wire 32.
  • Numeral 33 designates a filament extending in the same direction as the surface of the drums 26 and 21 and which is connected to lead wires 34 and 35.
  • drums 26 and 21 are caused to rotate in the ,di-
  • conduit 3 is connected to a backing pump.
  • Wires 34 and are connected to a low voltage supply suflicient to heat filament 33 to incandescence.
  • Lead wires 32 and 35 are connected to a high voltage supply. Since a relatively high vacuum exists during all stages of operation, the filament 33 is not damaged. Due to the high difference in potential between drums 26 and 21 and filament 33 electronic bombardment of the surfaces of the drums near the filament takes place, which results in heating and discharge of gases sorbed thereon. Discharged gases are removed thro gh conduit 3 by the backing pump.
  • reference numeral 50 designates a conduit of square or rectangular cross section in Brushes 30 and 3! make contact with plate ")6 provided which is mounted an endless band 5
  • Numeral 56 designates a heated filament or glow lamp and 51 a reflector.
  • conduit 50 is connected at the leftto the receptacle to be evacuated and'at the right to a backing pump which is put into operation. Filament 56 is heated and band 5
  • numeral 10 designates a shallow or squat, closed cylinder which serves as the pump casing. Intake and withdrawal conduits 2 and 3 are connected. at diametrically opposite sides of casing 10.
  • Numeral H designates a disc which is rotatably mounted upon shaft 12 which is driven by gear 13. The disc is preferably constructed of metal having gas sorptive properties, and a surface which has such properties as well as the ability to conduct electricity.
  • Numerals 14 and 15 designate electrodes or brushes which contact with shaft 12 and the surface -of disc II respectively. During operation disc H is caused to rotate, by energy applied to gear 13. A low voltage high amperage current is applied to brushes 14 and 15 which causes the surface of the disc near the brush 75 to become heated. Gases from the receptacle being evacuated are sorbed on the surface of the disc exposed at conduit 2 and are caused to be discharged at the withdrawal conduit 3 by that area.
  • numerals 2 and 3 designate the high and-low vacuum sides of. the pump.
  • Numeral 90 designates a shield which has the form of a half-sphere and is rotatably mounted at approximately the center of curvature upon shaft 9
  • Numeral 93 designates a plurality of strands'of electrical conducting material which also has the ability to sorb gases and which is preferably of large surface area. These strands are connected to a low voltage source of current in a conventional manner, so that current can be passed there through in order to heat them when desired.
  • a pump having a stationary sorption surface and a rotating discharge device.
  • numeral I05 designates a corrugated, cylindrical pump casing having the high and low vacuum ends 2 and 3 respectively.
  • An approximately elliptical with horizontal projections I01 and I08 is rotatably mounted upon shaft I09 which is in turn supported in the center of the casing by spider supports-H0 and Ill.
  • Baflies H2 and 3 are fixed to plate I06 at a point corresponding to the center of corrugations I and H5 as illustrated.
  • Numeral H6 designates a lagged electrical heating plate which is corrugated in the same manneras casing I05 and which covers only a portionof the circumference of the casing.
  • the plate is mounted upon rings H1 and H8 so that it is in close proximity to the surface of the casing-I05, but slightly out of contact therewith. Rings III and H8 are mounted in and supported by rolls H9 one or more of which are driven.
  • An electromagnet I20 is mounted upon the heating pad at a position opposite projection I01 which is constructed oi magnetic material. Casing I05 is rigidly supported in the position shown so that when pulleys H9 are actuated the heating plate H6 and magnet I20 revolve about the casing without coming into contact with its surface.
  • the high vacuum end 2 of the pump is connected to the receptacle, to be evacuated and the low vacuum end 3 to the backing pump.
  • the backing pump is put into operation and gas is sucked from the receptacle into the casing and passes through the openings between casing I05 and plates H2 and H3 and projection I08 and thence into the backing pump.
  • Plate H6 is then heated and driving pulley H9 actuated. Due to the attraction between magnet I20 and projection I01, plate I05 and baffles H2 and H3 rotate and are always in the same relative positionto heating plate H5 as illustrated in Fig. 9. Since the inside surface of easing I05 is constructed of material having good sorptive' properties, gases diffusing into it be come sorbed thereon.
  • the main casing of the apparatus illustrated in Figs. 9 and 10 may be a smooth cylinder instead of corrugated.
  • the corrugated surface is preferable however since it decreases the amount of diffusion back into the high vacuum end of the pump.
  • Rotation of the pump elements can be accomplished by a number of methods other than by an external shaft provided witha packing gland.
  • a telechron motor connected to the shaft to be rotated can be placed inside the pump casing, or an induction motor with a field outside the casing may be used.
  • Another method similar to that of Fig. 9 is to employ an external rotating magnet with an armature inside the casing.
  • Various methods for discharging the gases from the sorption surface can be employed and it will be apparent that those illustrated with one particular design of pump can be used with pumps of the other types illustrated.
  • Several sorption pumps can of course be used in series.
  • smooth sorption surfaces are suitable, I prefer to employ those having rough surfaces.
  • a rough surface is meant one which presents large differences in surface elevation as compared to the size of gas molecules. Such surfaces may appear to be substantially smooth All polished surfaces contain molecular crevices, while rough: surfaces have relatively enormous ravines lined with mo lecular crevices. Since practically no surface is smooth in this sense it is more a matter of expediency as to which should be used.
  • a large variety of materials other than those mentioned can be employed as construction materials for the sorption surfaces.
  • the material used should not of. course be one which has a higher vapor pressure than the degree of vacuum which is to be obtained.
  • Materials such as mica, glass, metal salts, metals such as copper, iron, nickel, platinum, platinum black, palladium, cellulose and its derivatives such as cellulose acetate and other esters and ethers, resin plastics, etc. have sorptive employed for this purpose.
  • mate rials having an extremely large surface area such as activated carbon, silica gel, alumina, silicates such as zeolites etc. are advantageous and can be formed or coated upon the pump surfaces in anydesired manner.
  • the sorbing material When the sorbing material is in the form of fabric or bristles it can be semi-conducting so that the high tension discharge can leak through them down to the boss onto which they are fastened. This can be accomplished by impregnation with salts or other conducting or semi-conducting material.
  • Cellulose derivative fibers, hogs bristles, felt, vegetable flber, wood, etc. are examples of suitable construction materials of this nature.
  • the; sorption surface may be constructed of, or-contain. a material which has a particular ailini-ty for the gas.
  • a mercury condensation pump is to be used as a backing pump for the sorption pump it would be advantageous to use a sorption surface having an aflinity for mercury vapor as well as for gases. would be suitable in such a situation.
  • Mercury molecules would amalgamate with the gold surface and on being heated to red heat would be action and may be A sorption pump having gold surfaces.
  • sorption pumps with a backing pump, since they will not operate under normal or slightly reduced pressures. It is desirable that a backing pump capable of giving a low pressure he used.
  • the sorption pump can operate at pressures as high as 1 mm. when sorption surfaces are used which are coated with a material having special ailinity for selected molecular species. Backing pressures of about .1 mm. and below increase the pumping speed, the most useful range being below about .01 mm. such as .001 mm. and downward. Since the sorption pumps operate best at pressures where the resistance to gas flow is relatively great, the clearances between the sorption surface and the pump casing need not be close.
  • a clearance of about 1 mm. is required with an absorption pump designed to operate at about .1 mm. and downward, while a larger sized pump operating at 10- mm. on large volumes of gas can have a clearance of 1 cm. or more.
  • the clearance should be large enough to allow passage of gas during the preliminary exhaustion at higher pressures and small enough so that molecules cannot pass by without suffering many collisions with the sorption surface.
  • the speed of rotation of the sorptionsurface depends upon the size of the pump, the speed of evacuation desired and the pressure under which it is operating. Obviously the rate of evacuation is proportional to the rate of rotation of the pump clement. Speeds of one to ten thousand revolutions per minute are suitable for all usual purposes although slower or higher speeds may be desirable with certain types of pump construction or under particular conditions.
  • the sorption pumps disclosed enable a rapid and eflicient removal of gases and are particularly advantageous whenit is desired to produce vacua of a very high degree. Lower pressures can be obtained than with. condensation pumps due to the fact that there is no volatilizable material employed and the problem of vapor pressure of pumping fluids is entirely eliminated. Since the rotating members of the pump-can be delicately mounted and are not of great weight, the energy required to rotate them even athigh speeds is very low, being only a fraction of that required to produce a vapor stream of the liquid pumping fluid in a condensation pump.
  • the process of producing a high vacuum which comprises producing a relatively high vacuum in the system to be evacuated by conventional pumping methods as by the operation of a backing pump, causing a surface having the property of adsorbing gases to move from the chamber to be evacuated to a point communicating with the intake of the conventional backing pump, sorbing gases on the adsorption surfaceat a point communicating with the chamber to be evacuated and then treating the adsorption surface to cause the gases to be discharged in the vicinity of the backing pump intake.
  • Pumping apparatus for producing a high vacuum in a closed receptacle which comprises in combination, a backing pump for maintaining the receptacle at a pressure of .1 mm. or less, an enclosed sorption surface, a conduit communicating with the receptacle which is to be evacuated and with the sorption surface, means for repeatedly exposing the sorption surface from a position communicating with the receptacle to be evacuated to a position in open communication with the intake of the backing pump, heating means for discharging gases from the sorption surface at the position adjacent the intake of the backing pump, means for preventing discharged gases from passing back into the receptacle, and a conduit through which discharged gases can be removed by the backing pump from the place at which they were discharged.
  • Pumping apparatus for producing a high vacuum in a closed receptacle which comprises in combination, a backing pump for maintaining the receptacle at a pressure of .1 mm. or less, an enclosed sorption surface, a conduit communicating with the receptacle which is to be evacuated and with the sorption surface, a second conduit communicating withthe sorption surface and the intake of the backing pump, means for discharging gas from the sorption surface at a position communicating with the intake of the backing pump, and means for moving the sorption surface from a position communicating with the receptacle to be evacuated to a position in communication with the intake of the backing pump.
  • Pumping apparatus for producing a high vacuum in a clased receptacle which comprises in combination a backing pump -for maintaining the receptacle at a relatively low pressure, an enclosed endless sorption surface, a conduit com municating with the receptacle to be evacuated and with one side of the sorption surface, a second conduit communicating with the approximately opposite side of the sorption surface, heating means for discharging gases from the sorption surface and with the intake of the backing pump .at a point communicating with the second conduit and means for causing the endless sorption surface to continuously pass between the two positions at which it communicates with these two conduits.

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  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Compressors, Vaccum Pumps And Other Relevant Systems (AREA)
  • Vaporization, Distillation, Condensation, Sublimation, And Cold Traps (AREA)
  • Solid-Sorbent Or Filter-Aiding Compositions (AREA)
US147514A 1936-07-06 1937-06-10 High vacuum Expired - Lifetime US2160863A (en)

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Application Number Priority Date Filing Date Title
GB18762/36A GB482884A (en) 1936-07-06 1936-07-06 Improved process and apparatus for producing high vacuum

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Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2636664A (en) * 1949-01-28 1953-04-28 Hertzler Elmer Afton High vacuum pumping method, apparatus, and techniques
US2757840A (en) * 1952-07-18 1956-08-07 Leitz Ernst Gmbh Method of and apparatus for evacuating vessels
US2808980A (en) * 1953-09-23 1957-10-08 Westinghouse Electric Corp Electrical vacuum pump
US2893624A (en) * 1956-04-05 1959-07-07 Nat Res Corp High vacuum
US3210915A (en) * 1961-03-29 1965-10-12 Bendix Balzers Vacuum Inc Sorption pump for pumping off gases and vapors
CN116318133A (zh) * 2023-03-07 2023-06-23 中国科学院上海天文台 一种具有加热吸附泵的氢原子频标

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS6419198A (en) * 1987-07-15 1989-01-23 Hitachi Ltd Vacuum pump

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2636664A (en) * 1949-01-28 1953-04-28 Hertzler Elmer Afton High vacuum pumping method, apparatus, and techniques
US2757840A (en) * 1952-07-18 1956-08-07 Leitz Ernst Gmbh Method of and apparatus for evacuating vessels
US2808980A (en) * 1953-09-23 1957-10-08 Westinghouse Electric Corp Electrical vacuum pump
US2893624A (en) * 1956-04-05 1959-07-07 Nat Res Corp High vacuum
US3210915A (en) * 1961-03-29 1965-10-12 Bendix Balzers Vacuum Inc Sorption pump for pumping off gases and vapors
CN116318133A (zh) * 2023-03-07 2023-06-23 中国科学院上海天文台 一种具有加热吸附泵的氢原子频标

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NL45601C (en(2012))
GB482884A (en) 1938-04-06

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