EP0884480A2 - Vakuumpumpe - Google Patents

Vakuumpumpe Download PDF

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Publication number
EP0884480A2
EP0884480A2 EP97202409A EP97202409A EP0884480A2 EP 0884480 A2 EP0884480 A2 EP 0884480A2 EP 97202409 A EP97202409 A EP 97202409A EP 97202409 A EP97202409 A EP 97202409A EP 0884480 A2 EP0884480 A2 EP 0884480A2
Authority
EP
European Patent Office
Prior art keywords
vacuum pump
electromagnet
casing
rotor
sealing means
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP97202409A
Other languages
English (en)
French (fr)
Other versions
EP0884480A3 (de
Inventor
Fausto Casaro
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Varian SpA
Original Assignee
Varian SpA
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Varian SpA filed Critical Varian SpA
Publication of EP0884480A2 publication Critical patent/EP0884480A2/de
Publication of EP0884480A3 publication Critical patent/EP0884480A3/de
Withdrawn legal-status Critical Current

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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04D—NON-POSITIVE-DISPLACEMENT PUMPS
    • F04D23/00—Other rotary non-positive-displacement pumps
    • F04D23/001—Pumps adapted for conveying materials or for handling specific elastic fluids
    • F04D23/005—Pumps adapted for conveying materials or for handling specific elastic fluids of axial-flow type
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04D—NON-POSITIVE-DISPLACEMENT PUMPS
    • F04D29/00—Details, component parts, or accessories
    • F04D29/08—Sealings
    • F04D29/10—Shaft sealings
    • F04D29/14—Shaft sealings operative only when pump is inoperative
    • F04D29/143—Shaft sealings operative only when pump is inoperative especially adapted for elastic fluid pumps

Definitions

  • the present invention refers to a vacuum pump and more precisely to a turbomolecular vacuum pump adapted to be used in presence of corrosive gases.
  • the corrosive gases present in the working environment can gather within the pump and reach, through the gaps existing between the rotating and the stationary parts, the pump electric motor and the mechanical bearings or the magnetic suspensions, when these latter are provided for.
  • CP Corrosion Proof
  • a further object of the present invention is to solve the problem of realizing a seal adapted to prevent the inlet of corrosive gases when the vacuum pump is stopped, such seal being operative without requiring an electric feed.
  • Figure 1 illustrates a monolithic hollow rotor group 1 of a turbomolecular vacuum pump comprising a first plurality of smooth rotor disks 2 and a second plurality of rotor disks 3 provided with peripheral radial blades 4.
  • Such monolithic rotor 1 is supported by a rotatable shaft 5 driven by an electric motor 6 located inside a cylindrical casing 7.
  • said cylindrical casing 7 is substantially coaxial with the monolithic rotor 1 and comprises a first portion 7a of a smaller cross section that extends axially inside a cavity defined in the monolithic hollow rotor 1 and a second portion 7b of larger cross section secured to a casing (not shown) of the vacuum pump and located ouside said monolithic hollow rotor 1.
  • the cylindrical casing 7 is further provided with a closed base 9 in correspondence of that free end of the portion 7a that is adjacent to the rotor 1, and with an open base 10 at the opposed free end of the portion 7b.
  • the closed base 9 of said first portion 7a is further provided with an axial central hole 11 for receiving a first ball bearing 12 rotatably supporting the shaft 5.
  • a circular cover 13 closes the open base 10.
  • a second ball bearing 14 rotatably supporting the free end of the rotatable shaft 5 that is opposed with respect to the monolithic rotor 1, is disposed in a central cavity 15 of an axial projection 16 of said circular cover 13, such projection extending internally to the portion 7a of cylindrical casing 7.
  • the rotor 17 of the electric motor 6 is located between said first ball bearing 12 and said second ball bearing 14, and is fastened to the rotatable shaft 5.
  • stator 18 of the electric motor 6 is located between said rotor 17 and the inner wall of said cylindrical casing 7, and secured to said inner wall.
  • Such stator 18 comprises windings 19 fed through electric leads 20 from an electric connector 21 fitted in the portion 7b of the cylindrical casing 7 and accessible outside of the vacuum pump.
  • a gap 8 is provided between the rotor 1 and the portion 7a of the casing 7 for allowing an unimpeded rotation of the rotor 1 with respect to the casing 7.
  • disengageable sealing means 22 are provided in the gap 8, in correspondence of the closed base 9, around said rotatable shaft 5, said means comprising an electromagnet 25 and an annular flexible cap or washer 23 of a ferromagnetic material, to which it is secured an elastic ring 24, for example formed of Viton (TM).
  • TM Viton
  • said disengageable sealing means separates the gap 8 into two portions - i.e. an inner portion 8a and an outer portion 8b - with respect to said means of seal 22.
  • the electromagnet 25 is fed by the electric leads 26 from the electric connector 21 and comprises a solenoid with an axis substantially orthogonal to said (annular) washer 23.
  • the flexible washer 23 is actracted towards the electromagnet 25 assuming a disengaged position and the gas can flow unimpeded between the two portions of gap 8a and 8b and viceversa, and the rotor 1 is free to rotate.
  • the washer 23 comprises an inner folded edge 27 in correspondence of which said elastic ring 24 is fastened by vulcanisation or bonding.
  • the outer circumferential periphery of said annular washer 23 is blocked between the outer circumferential rim 31 of a first U-shaped inner ring nut 29 of a ferromagnetic material in which the elettromagnet 25 is fastened by an epoxy resin, and an L-shaped rim directed towards the inner part 32 of a second outer ring nut 30.
  • Said ring nuts 29 and 30 are further preferably joined together thanks tothreadings formed on the outer circumferential surface of the inner ring nut 29 and on the inner circumferential surface of the outer ring nut 30, respectively.
  • An annular channel 28, shown in Figure 1, is provided in the base 9 of the first portion 7a of said cylindrical casing 7 aroud the rotatable shaft 5 for housing the ring nuts 29 and 30.
  • a sealing ring 34 partially contained in an annular groove 37 on the outer circumferential surface of said ring nut 30, ensures the sealing between the second ring nut 30 and the channel 28.
  • Both the channel 28 and the ring nut 29 are further provided with an axial hole for the passage of the leads 26 for feeding said electromagnet 25.
  • a radial screw 33 is further provided for firmly securing the ring nut 30, and therefore the sealing means 22, in the channel 28.
  • Figure 3 illustrates a second embodiment of the invention in which the sealing means 22' comprises a washer 23' having a circumferential periphery with an L-folded portion 23'a, while the opposed end has an inner edge 27' folded in the opposite direction with respect to said portion 23'a.
  • Said portion 23'a is further firmly blocked inside the annular channel 28 provided in the base 9 of said first portion 7a of the cylindrical casing 7, around the shaft 5, between the wall of the channel 28 and a ring nut 29' housing the electromagnet 25.
  • the outer circumferential surface of said ring nut 29' has a portion 29'a with a smaller diameter for housing said portion 23'a of the washer 23'.
  • annular groove 37' partially housing a sealing ring 34 preventing the passage of gas radially through the channel 28.
  • a system for determining the relative speed of the rotor with respect to the pump body for example constituted by a movement sensor 36, can be advantageously provided for controlling a feeding unit (not shown) of the electromagnet 25 only when the relative speed between the rotor 1 and the casing 7 is (or is at least approaching to) zero.
  • the braking couple the sealing ring 24 applies to the rotor 1 is proportional to the radius of the ring 24, it is preferable to provide a sealing ring with the maximum possible diameter, depending on the geometry of the vacuum pump.
  • Figure 4 illustrates a third embodiment of the invention in which the sealing means 22'' comprises an annulus 39 of a ferromagnetic material with a elastic ring 24 partially contained in a circular groove 40 of the surface facing the rotor 1 of the pump.
  • Said annulus 39 is located adjacent an electromagnet 25 that innturn is blocked in a U-shaped ring nut 41 of a ferromagnetic material housed in the annular channel 28 provided in the base 9 of the first portion 7a of cylindrical casing 7.
  • a plurality of coil springs 42 adapted to repel said annulus 39 with respect to the ring nut 41 when the magnetic field generated by the electromagnet 25 is not present.
  • Said springs 42 are partially housed in as many axial holes 43 of the inner wall of the ring nut 41.
  • said annulus 39 is therefore movable between an engaged position where the elastic ring 24 - pressing the surface of the rotor due to the repulsive force exerted by the springs over the annulus 39 - prevents the gas from flowing between the zone located ouside the circumference of the ring 24 and the zone located inside such circumference, and viceversa, and a disengaged position where the rotor, thanks to the actraction force generated by the magnetic field over the annulus 39 is free to rotate with respect to said elastic ring 24 and thus the gas can flow.
  • a second annular ring nut 44 is provided that is screwed over the outer circumferential surface of said ring nut 41 and axially extends outside the channel 28 for preventing radial displacements of the annulus and its misalignism with respect to the magnetic field generated by the electromagnet 25.
  • a sealing ring 34 adapted to prevent the gas passage radially through the channel 28.
  • the portion of said second ring nut 44 axially extending outside the channel 28 is further provided with a radial edge 45 folded towards the inside and adapted to limit the axial movement of the annulus 39 and preventing its outcoming.
  • the annulus 39 has a thickness of at least 2 mm for avoiding an excessive limitation of the electromagnet attraction force and ensuring a good axial guide surface.
  • a plurality of axial holes 46 are further provided for making easier the screwing of said second ring nut 44 on the first ring nut 41 for inserting a suitable tool (not shown).
  • FIG. 5 there is illustrated a fourth embodiment of the invention in which the sealing means 22''' are formed as an annular L-shaped member 50 of a ferromagnetic material housing an elastic ring 24 in a circular groove 51 of the surface facing the rotor 1 of the pump.
  • Such annular member 50 comprises a first portion 50a adjacent to an electromagnet 25 that in turn is secured in a U-shaped ring nut 52 of a ferromagnetic material, with this ring nut being housed in the annular channel 28 provided in the base 9 of the first portion 7a of the cylindrical casing 7, and a second portion 50b slidably disposed between said ring nut 52 and the annular channel 28.
  • a radial outer projection 52a having a plurality of holes for the passage of screws 53 for fastening the ring nut 52 to the base of the channel 28 is provided at the base of the ring nut 52.
  • Coil springs 54 resting on the radial projection 52a are further provided for driving back said member 50 with respect to the ring nut 52 when the magnetic field of the electromagnet 25 ceases.
  • the coil springs 54 are partially housed in as many axial holes 55 provided in portion 50b of the annular member 50.
  • said annular member 50 is movable between a first engaged position in which the elastic ring 24 is urged against the rotor surface by the repulsion force of the springs 54 and prevents the gas from flowing from the zone outside the circumference of the ring 24 to the zone inside such circumference and viceversa, and a second disengaged position in which the rotor 1 of the vacuum pump - thanks to the attractive force of the magnetic field acting on member 50 - can freely rotate with respect to said elastic ring 24 and the gas can freely flow.
  • a series of threaded axial pins 56 are screwed in the inner wall of the ring nut 52 and pass through as many holes provided in the portion 50a of the annular member 50 to prevent the annular member 50 from coming out of the seat defined between the ring nut 52 and the channel 28.
  • the annular member 50 has a thickness of at least 2 mm to prevent excessive limitations to the attraction force of the electromagnet.
  • a sealing ring 34 partially housed in an annular groove 57 for preventing the gas passage radially through the channel 28.
  • the vacuum pump according to the invention can further comprise a feeding unit comprising a device for converting the kinetic energy stored by the rotor 1 into electric energy when the rotor 1 decelerates.
  • the use of said converting device has the advantage of progressively braking the rotation of the rotor for the whole time in which the energy conversion takes place.
  • an external feeding battery either in combination or as an alternative to the energy conversion device.
  • the feeding battery provides the additional advantage that it can be mounted, if required, on board of the pump, thus feeding the electromagnet until the rotor speed is at least near to zero even in case the cables from an external feed unit for feeding the pump are interrupted or have been disconnected from the connector 21.
  • sealing means 22 can be advantageously located even outside the rotor 1, for example between the outer wall of said casing 7 and the adjacent wall of the disk rotor 2 that is nearest to said casing 7.
  • the sealing means 22 can be further advantageously used as braking devices for the rotor 1 during the working of the pump.

Landscapes

  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Non-Positive Displacement Air Blowers (AREA)
  • Compressors, Vaccum Pumps And Other Relevant Systems (AREA)
  • Applications Or Details Of Rotary Compressors (AREA)
EP97202409A 1997-06-11 1997-08-01 Vakuumpumpe Withdrawn EP0884480A3 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
IT97TO000510A IT1292764B1 (it) 1997-06-11 1997-06-11 Pompa da vuoto.
ITTO970510 1997-06-11

Publications (2)

Publication Number Publication Date
EP0884480A2 true EP0884480A2 (de) 1998-12-16
EP0884480A3 EP0884480A3 (de) 1999-08-25

Family

ID=11415777

Family Applications (1)

Application Number Title Priority Date Filing Date
EP97202409A Withdrawn EP0884480A3 (de) 1997-06-11 1997-08-01 Vakuumpumpe

Country Status (2)

Country Link
EP (1) EP0884480A3 (de)
IT (1) IT1292764B1 (de)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN114352553A (zh) * 2021-12-31 2022-04-15 北京中科科仪股份有限公司 一种旋涡机构及复合分子泵

Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2521650A1 (fr) * 1982-02-16 1983-08-19 Cit Alcatel Pompe rotative a vide eleve
DE3631941A1 (de) * 1985-09-30 1987-04-16 Kraftwerk Union Ag Geblaese zum antrieb eines kontinuierlichen gasstromes
JPS62282195A (ja) * 1986-05-29 1987-12-08 Mitsubishi Electric Corp タ−ボ分子ポンプ

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
None

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN114352553A (zh) * 2021-12-31 2022-04-15 北京中科科仪股份有限公司 一种旋涡机构及复合分子泵
CN114352553B (zh) * 2021-12-31 2024-01-09 北京中科科仪股份有限公司 一种旋涡机构及复合分子泵

Also Published As

Publication number Publication date
ITTO970510A0 (de) 1997-06-11
IT1292764B1 (it) 1999-02-11
EP0884480A3 (de) 1999-08-25
ITTO970510A1 (it) 1998-12-11

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