EP0806572A2 - Pompe à diffusion - Google Patents

Pompe à diffusion Download PDF

Info

Publication number
EP0806572A2
EP0806572A2 EP97302923A EP97302923A EP0806572A2 EP 0806572 A2 EP0806572 A2 EP 0806572A2 EP 97302923 A EP97302923 A EP 97302923A EP 97302923 A EP97302923 A EP 97302923A EP 0806572 A2 EP0806572 A2 EP 0806572A2
Authority
EP
European Patent Office
Prior art keywords
outer body
pump
diffusion pump
chimney
diffusion
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Withdrawn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
EP97302923A
Other languages
German (de)
English (en)
Other versions
EP0806572A3 (fr
Inventor
Graeme Huntley
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.)
BOC Group Ltd
Original Assignee
BOC Group Ltd
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 BOC Group Ltd filed Critical BOC Group Ltd
Publication of EP0806572A2 publication Critical patent/EP0806572A2/fr
Publication of EP0806572A3 publication Critical patent/EP0806572A3/fr
Withdrawn legal-status Critical Current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
    • F04F—PUMPING OF FLUID BY DIRECT CONTACT OF ANOTHER FLUID OR BY USING INERTIA OF FLUID TO BE PUMPED; SIPHONS
    • F04F9/00—Diffusion pumps

Definitions

  • the present invention relates to vacuum pumps of the type known as diffusion pumps.
  • Diffusion pumps are well known and widely used for the attainment of high and ultra high vacuum. When used with modern working fluids and accessories, they can produce pressures approaching 10 -10 mbar. The pumps are generally incapable of exhausting directly to the atmosphere and require the use of a backing pump, commonly an oil sealed rotary vacuum pump, in conjunction with the diffusion pump itself.
  • Diffusion pumps generally comprise a substantially cylindrical outer body which is cooled by, for example, coils helically wound around the outside of the body through which cooling water can be circulated or alternatively by air cooled fins attached to the outside of the body.
  • the outer body Within the outer body is positioned a hollow “chimney " sitting at, or close to, the base of the outer body and which tapers (continuously or, more usually, in stages) upwardly from the base.
  • the chimney is generally contained within the outer body and is positioned substantially concentrically therein.
  • top cap having a generally circular portion of somewhat larger diameter than the top of the chimney and positioned symmetrically with regard to the chimney and having a downwardly projecting annular side portion whose lower edge is somewhat beneath the upper edge of the chimney.
  • the top cap is therefore substantially an inverted "cup shaped" component positioned about the top of the chimney with a circular or annular passageway therebetween.
  • the top cap and the adjacent portion of the chimney defining the annular passageway is known as a 'jet stage'.
  • a heater is provided in the base of the outer body and, prior to use of the pump, a working fluid is placed in the base of the body to a height above the lower edge of the chimney positioned within the body.
  • the fluid is usually a low vapour pressure oil although some versions of diffusion pumps use mercury.
  • a pump inlet is positioned in the outer body above the top cap and an outlet in the side of the body towards the base of the chimney but above the oil level.
  • the outlet is normally connected to a backing pump as described above.
  • the backing (rotary) pump is turned on and left running continuously, a pressure of at least 0.1 mbar being required on the exhaust side of the diffusion pump.
  • the cooling system (water or air) for the outer body is turned on and the oil can now be heated by the heater for, for example, fifteen to twenty minutes, when it begins to boil. Hot vapour rises up the chimney and forms (aided by the taper) a relatively high oil pressure at the top of the chimney. The vapour is then urged through the passageway between the chimney and the top cap, the jet stage, to an area of much lower pressure and creates an annular vapour jet.
  • This jet is designed to move at a velocity which is supersonic and which impinges on the inside surface of the cooled outer body where the vapour condenses and condensed oil flows down the inside wall of the outer body and returns to the oil reservoir at the base of the body.
  • a limitation of known diffusion pumps whether they be air or water cooled, is that they can operate in only one orientation; that is to say, vertically with the chimney extending vertically upwardly from the base within the hollow body, which thereby allows the condensed working fluid to drain back to the base.
  • a diffusion pump comprises;
  • the wick material is a sintered material.
  • a known diffusion pump 1 comprises a hollow outer body 2 of generally circular cross-section, a major portion of which is provided with cooling coils 4 for circulation of cooling fluid, for example water.
  • the body 2 includes a base 6 and vapour chimney 8 is positioned within the outer body 2 and extends upwardly from the base 6.
  • a working fluid 7 is located in the base of the chimney 8 and, as shown, a heater 10 is located immediately below the base 6.
  • the chimney is formed with a single jet stage 12.
  • the diffusion pump 1 also includes an outlet 14 for connection to a backing vacuum pump and an inlet 16 for connection to a chamber to be evacuated. As shown, the jet stage 12 is located adjacent the inlet 16.
  • the backing pump is turned on to reduce the pressure within the diffusion pump 1 and, if necessary, a coolant is passed through the coils 4.
  • Heating of the working fluid by means of the heater 10 causes boiled vapour to rise up the chimney 8 in the general manner described earlier and to emerge through the jet stage 12 and thereafter to fall downwardly in the general direction of the base 6 along the inner surface of the outer body 2.
  • the hollow outer body 2 of the diffusion pump 1 is provided on its inside surface with a layout of wick material 20 (see Figure 2) which will absorb the working fluid.
  • FIG 2 this illustrates a diffusion pump according to the present invention which has been inverted through 180 degrees and generally utilising the same reference numerals as shown in Figure 1.
  • the working fluid present in the wick from a reservoir at the base of the pump in normal orientation or otherwise rises through the wick material 20 by capilliary action as indicated by the arrows A to arrive at or adjacent the heater 10 where it is evaporated.
  • the vaporised working fluid then passes through the chimney 8 and out via the jet stage 12 in the conventional manner. It will be evident that by using a layer of wick material 20 which covers the whole or a substantial portion of the inner surface of the outer body 2, the diffusion pump 1 can be used effectively in any orientation. This is a particularly useful attribute when evacuating small portable devices such as portable mass spectrometers which require a secondary pump to operate in any orientation.
  • FIG. 3 this illustrates a diffusion pump according to the present invention which as shown is in a conventional orientation.
  • the wick material 20' is located over the base 6' of the body 2' as well as a portion of the inner surface of the outer body 2' adjacent the heater 10'. This will allow the diffusion pump to be transported in any orientation without the loss of working fluid or the contamination of system parts.
  • This diffusion pump can be operated in the upright conventional orientation or at a considerable angle to the upright when compared with a conventional diffusion pump.

Landscapes

  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Compressors, Vaccum Pumps And Other Relevant Systems (AREA)
  • Structures Of Non-Positive Displacement Pumps (AREA)
EP97302923A 1996-05-07 1997-04-29 Pompe à diffusion Withdrawn EP0806572A3 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GBGB9609467.7A GB9609467D0 (en) 1996-05-07 1996-05-07 Improvements in diffusion pumps
GB9609467 1996-05-07

Publications (2)

Publication Number Publication Date
EP0806572A2 true EP0806572A2 (fr) 1997-11-12
EP0806572A3 EP0806572A3 (fr) 1998-06-17

Family

ID=10793279

Family Applications (1)

Application Number Title Priority Date Filing Date
EP97302923A Withdrawn EP0806572A3 (fr) 1996-05-07 1997-04-29 Pompe à diffusion

Country Status (3)

Country Link
EP (1) EP0806572A3 (fr)
JP (1) JPH1073100A (fr)
GB (1) GB9609467D0 (fr)

Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1448750A (en) * 1973-12-28 1976-09-08 Boc International Ltd Vacuum vapour pumps
SU985415A1 (ru) * 1980-11-05 1982-12-30 Предприятие П/Я А-3634 Охлаждаема ловушка
SU1576737A1 (ru) * 1988-09-27 1990-07-07 Предприятие П/Я А-3605 Адсорбционна ловушка

Also Published As

Publication number Publication date
GB9609467D0 (en) 1996-07-10
EP0806572A3 (fr) 1998-06-17
JPH1073100A (ja) 1998-03-17

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