US3912415A - Molecular pump and method therefor - Google Patents

Molecular pump and method therefor Download PDF

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Publication number
US3912415A
US3912415A US453498A US45349874A US3912415A US 3912415 A US3912415 A US 3912415A US 453498 A US453498 A US 453498A US 45349874 A US45349874 A US 45349874A US 3912415 A US3912415 A US 3912415A
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Prior art keywords
molecular pump
stator
helical grooves
additional
pump according
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Expired - Lifetime
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US453498A
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English (en)
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Louis Maurice
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Alcatel CIT SA
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Alcatel CIT SA
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04D—NON-POSITIVE-DISPLACEMENT PUMPS
    • F04D19/00—Axial-flow pumps
    • F04D19/02—Multi-stage pumps
    • F04D19/04—Multi-stage pumps specially adapted to the production of a high vacuum, e.g. molecular pumps
    • F04D19/044—Holweck-type pumps

Definitions

  • ABSTRACT 30 Foreign Application Priority Data Method for constructing molecular pumps and highvacuum molecular pumps improved according to that Mar. 21, 1973 France 73.10183 method, comprising a rotating drum with Slight p y
  • U S Cl 415 415/90 within a stator whose inside face is cylindrical.
  • the [51] F6ld1/36 improvement consists in increasing the number of [58] Fieid "415/71 72 threads formed on the inside face of the stator or the 1 rotor or on both adjacent faces, going from the suction to the discharge.
  • FIG .1 PRIOR ART MOLECULAR PUMP AND METHOD THEREFOR BACKGROUND OF THE INVENTION
  • the present invention concerns a method for manufacturing improved molecular high vacuum pumps having a cylindrical drum, of the multi-thread type, as well as pumps produced according to that method.
  • a molecular pump consisting of a cylindrical drum rotating at high speed with very slight clearance inside a stator having the same axis of symmetry as the drum (Holweck pump) has been known for nearly fifty years, now.
  • a helix whose cross-section decreases from the part subjected to the highest vacuum towards the zone where the vacuum is slighter has been formed on the inside wall of the drum.
  • the pump thus produced industrially is in fact constituted by two half pumps facing each other and actually operating in parallel.
  • the hollowed groove part of the inside face of the stator is a helix having a single thread.
  • the inventor has therefore sought to improve the compression ratio which may be obtained with a molecular vacuum pump having a cylindrical drum of the multi-thread type, capable of giving a satisfactory discharge, for a given active surface, rotation speed and clearance between the rotor and the stator.
  • various measures may be considered, such as, for example, that which consists in reducing the clearance between the rotor and the stator, but these measures, besides the fact that they lead in general to the considerable increasing of the cost of machining, reduce the operational reliability of the pump to a prohibitive extent, the least foreign body, the least expansion of one of its parts or the least mechanical deformation causing seizing, as occurred fifty years ago in the first Holweck pumps.
  • the method and the device developed by the inventor enable, in a cylindrical drum type pump designed for a satisfactory discharge, an increase of the compression ratio without reducing the operational clearance thereof and without appreciably increasing the cost of machining.
  • the object of the invention is a method enabling improvement of the operation of high vacuum molecular pumps having a cylindrical drum, of the multi-thread type, characterized in that the number of threads is increased from the suction part towards the discharge part thereby sub-dividing each of the grooves comprised between two successive threads into several separated channels.
  • the device resulting from the implementing of the above method is therefore a high vacuum molecular pump comprising a cylindrical drum rotating at high speed with slight clearance in a stator whose inside face is cylindrical, comprising, moreover, several helical grooves formed on at least one of two adjacent faces which are parallel to each other, separated by low walls beginning at the inlet of the pump where suction occurs and ending at one of the ends of the drum where discharge occurs, characterized in that over one part of its length, each groove is subdivided into several narrower channels by low walls which are parallel to each other.
  • each gaseous flow passing along helical grooves first into two channels by means of a low central wall, them, further downstream, to subdivide again once or twice each of the channels by means of low walls beginning nearer to the outlet.
  • Simplifications in machining may lead to a reducing of the subdividing of each helical groove to only once, into two or three channels by means of one or two intermediate low walls respectively which are not very long.
  • central suction pumps have been constructed comprising, on either side of a central suction volume, multiple grooves with reverse pitches on each side of the central suction, each of them being subdivided in the vicinity of the end of the drum into several channels.
  • Such a device operates as a device formed by two half-pumps operating in parallel and enables the discharge to be increased.
  • FIG. 1 is a diagrammatic view of a multi-thread cylindrical drum device substantially according to the known art
  • FIG. 2 shows the developed view of one of the grooves of the stator according to one embodiment of the invention
  • FIG. 3 shows a developed view of one of the grooves of the stator according to another embodiment of the invention.
  • FIG. 1 showing diagrammatically the essential parts of a cylindrical drum molecular pump
  • a simple multi-thread pump comprises a stator l and a cylindrical rotor 2 whose axis of rotation 3 merges with the geometrical axis of the stator.
  • the upper part of the drawing shows the suction side of the pump, the discharged gaseous flux leaving through the bottom part of the drawing.
  • the threads have been traced on the cylindrical stator.
  • the inlets of the multiple grooves 4, 5, 6, 7, 8, 9, l0, and 11 appear in the thickness of the stator l.
  • a low wall appears between the grooves.
  • the low walls, such as 12 and 13 form, on the cylindrical inside face of the stator, helixes limiting, in the stator, eight parallel helical grooves. The depth of the grooves decreases from the inlet to the discharge.
  • FIG. 2 shows a developed illustration of the trace formed on the stator of the pump.
  • the left-hand low wall in FIG. 2 being, for example, the low wall 12 in FIG. 1 and the right-hand low wall being the low wall 13, the gap between the two low walls being constituted by the groove 9.
  • a low central wall 15 dividing the helical groove 9 into two channels 16 and 17 is provided in the region where the compression ratio rises substantially, starting from the first third of the length of the thread for example, a low central wall 12 dividing the helical groove 9 into two channels 16 and 17.
  • the reduction of the leakages thus obtained is already spectacular and the compression ratio of the pump is improved in great proportions. It may, however, be an even greater advantage to again subdivide the channels 16 and 17 by means of two low walls 18 and 19 which are shorter to make four channels 20, 21, 22, and 23 appear at the outlet, whereas at the inlet, there was only one helical groove 9.
  • FIG. 3 shows another embodiment also according to the invention in which the helical groove comprised between the low walls 12 and 13 has been subdivided substantially at the third of the length of the thread into three channels 24, 25 and 26 by means of two intermediate low walls 27 and 28 having the same length.
  • low walls such as 27 and 28 have been arranged between low walls such as 12' and 13 exclusively in the vicinity of the discharge, thus limiting channels such as 24, 25 and 26, which are short.
  • a method for improving the operation of a high vacuum molecular pump of the multi-thread type comprising increasing the number of threads at a discharge portion of a multi-thread high vacuum molecular pump by forming at least one low wall between two successive threads, said at least one low wall being parallel to said two threads and being formed with a length shorter than the length of the groove between said two threads, thereby subdividing respective grooves formed between two successive threads into at least two additional channels at the discharge portion.
  • a high vacuum molecular pump comprising:
  • a plurality of helical grooves provided at a surface of at least one of the stator and rotor, said surface facing the other of the stator and rotor, said plurality of helical grooves being formed by a plurality of parallel walls extending from a suction inlet means to a discharge outlet means, and
  • At least one additional wall provided between successive ones of said plurality of parallel walls for subdividing each of said plurality of helical grooves in the vicinity of said discharge outlet means, said at least one additional wall having a length shorter than the length of each of said plurality of helical grooves.
  • a molecular pump according to claim 8 wherein two further additional walls are provided to subdivide each of said two channels into two further channels, said two further additional walls each being shorter in length than said one additional wall.
  • a molecular pump according to claim 4 wherein two additional walls are provided between successive ones of said plurality of parallel walls to subdivide each of said plurality of helical grooves into three channels, said two additional walls each having a rectangular cross-section.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Non-Positive Displacement Air Blowers (AREA)
  • Applications Or Details Of Rotary Compressors (AREA)
US453498A 1973-03-21 1974-03-21 Molecular pump and method therefor Expired - Lifetime US3912415A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
FR7310183A FR2222886A5 (xx) 1973-03-21 1973-03-21

Publications (1)

Publication Number Publication Date
US3912415A true US3912415A (en) 1975-10-14

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ID=9116654

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US453498A Expired - Lifetime US3912415A (en) 1973-03-21 1974-03-21 Molecular pump and method therefor

Country Status (10)

Country Link
US (1) US3912415A (xx)
JP (1) JPS49128306A (xx)
BE (1) BE812288A (xx)
CH (1) CH579219A5 (xx)
DE (1) DE2411247C2 (xx)
FR (1) FR2222886A5 (xx)
GB (1) GB1459933A (xx)
IT (1) IT1014568B (xx)
NL (1) NL7403784A (xx)
SU (1) SU667162A3 (xx)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4708586A (en) * 1985-08-14 1987-11-24 Rikagaku Kenkyusho Thread groove type vacuum pump
US5383550A (en) * 1992-12-09 1995-01-24 Ciba-Geigy Corporation Contact lens case

Families Citing this family (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
NL8105614A (nl) * 1981-12-14 1983-07-01 Ultra Centrifuge Nederland Nv Hoog-vacuum moleculair pomp.
JPS6238899A (ja) * 1985-08-14 1987-02-19 Osaka Shinku Kiki Seisakusho:Kk ねじ溝式真空ポンプ
JPS6351195U (xx) * 1986-09-20 1988-04-06
GB2585936A (en) * 2019-07-25 2021-01-27 Edwards Ltd Drag pump
EP4194700A1 (de) * 2023-04-18 2023-06-14 Pfeiffer Vacuum Technology AG Vakuumpumpe mit einer holweck-pumpstufe mit veränderlicher holweck-geometrie

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1492846A (en) * 1922-05-11 1924-05-06 Mullard Radio Valve Co Ltd Vacuum pump
US3697190A (en) * 1970-11-03 1972-10-10 Walter D Haentjens Truncated conical drag pump
US3802794A (en) * 1971-04-17 1974-04-09 Dornier Ag Molecular pump comprising a pump cylinder equipped with a thread

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR536278A (fr) * 1921-06-01 1922-04-29 Pompe hélicoïdale pour vides élevés
FR1293546A (fr) * 1961-02-09 1962-05-18 Alsacienne Constr Meca Perfectionnements aux pompes moléculaires rotatives

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1492846A (en) * 1922-05-11 1924-05-06 Mullard Radio Valve Co Ltd Vacuum pump
US3697190A (en) * 1970-11-03 1972-10-10 Walter D Haentjens Truncated conical drag pump
US3802794A (en) * 1971-04-17 1974-04-09 Dornier Ag Molecular pump comprising a pump cylinder equipped with a thread

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4708586A (en) * 1985-08-14 1987-11-24 Rikagaku Kenkyusho Thread groove type vacuum pump
US5383550A (en) * 1992-12-09 1995-01-24 Ciba-Geigy Corporation Contact lens case

Also Published As

Publication number Publication date
BE812288A (fr) 1974-09-16
NL7403784A (xx) 1974-09-24
SU667162A3 (ru) 1979-06-05
DE2411247C2 (de) 1983-03-24
GB1459933A (en) 1976-12-31
IT1014568B (it) 1977-04-30
FR2222886A5 (xx) 1974-10-18
CH579219A5 (xx) 1976-08-31
JPS49128306A (xx) 1974-12-09
DE2411247A1 (de) 1974-09-26

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