US3686836A - Dust-free work station with two crossed laminar flows - Google Patents

Dust-free work station with two crossed laminar flows Download PDF

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Publication number
US3686836A
US3686836A US48172A US3686836DA US3686836A US 3686836 A US3686836 A US 3686836A US 48172 A US48172 A US 48172A US 3686836D A US3686836D A US 3686836DA US 3686836 A US3686836 A US 3686836A
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Prior art keywords
work station
work
flow
air
horizontal
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US48172A
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English (en)
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Pierre Rabilloud
Jean-Claude Guichard
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Individual
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24—HEATING; RANGES; VENTILATING
    • F24F—AIR-CONDITIONING; AIR-HUMIDIFICATION; VENTILATION; USE OF AIR CURRENTS FOR SCREENING
    • F24F3/00—Air-conditioning systems in which conditioned primary air is supplied from one or more central stations to distributing units in the rooms or spaces where it may receive secondary treatment; Apparatus specially designed for such systems
    • F24F3/12—Air-conditioning systems in which conditioned primary air is supplied from one or more central stations to distributing units in the rooms or spaces where it may receive secondary treatment; Apparatus specially designed for such systems characterised by the treatment of the air otherwise than by heating and cooling
    • F24F3/16—Air-conditioning systems in which conditioned primary air is supplied from one or more central stations to distributing units in the rooms or spaces where it may receive secondary treatment; Apparatus specially designed for such systems characterised by the treatment of the air otherwise than by heating and cooling by purification, e.g. by filtering; by sterilisation; by ozonisation
    • F24F3/163—Clean air work stations, i.e. selected areas within a space which filtered air is passed
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10S55/00—Gas separation
    • Y10S55/29—Air curtains

Definitions

  • laminar flow should not be taken to mean a flow defined by a Reynolds number of under 2,000 but a flow characterized by the fact that a thin stream of smoke injected into its midst will be discharged in the general direction of the flow in the form of a plume which, though it broadens out slightly, maintains an axis which is straight and parallel to that direction.
  • a result of this basic property is that stations of this type not only provide a dust-free work surface but that pollution at any point is discharged along a constrained path and all the dangerous zones are known. In particular, any continuous or accidental polluting with dust remains under control.
  • a dust-free work station comprises two sections, to wit a rear section which surmounts the work surface proper and which is crossed by a horizontal transverse laminar flow and another narrower section located between the first section and the operator and crossed by a vertical laminar flow.
  • FIG. 1 shows in vertical section a conventional horizontal flow type dust-free station
  • FIG. 2 shows in vertical section a conventional flow type dust-free station
  • FIG. 3 shows in vertical section a dust-free station according to this invention.
  • FIG. 4 is a vertical section taken through the line IV-IV of FIG. 3.
  • FIG. I shows a horizontal laminar flow type station formed by a chest 1 open at the front at 2 and comprising a blower 3 which is located beneath work surface 4 and which sucks in air from the room at 5 and impels it toward the rear end of the chest, whence it flows through a filter 6 as a laminar flow 7 directed toward the operator.
  • the air which is continuously drawn in form and expelled into the work premises sweeps the work surface 4 horizontally. All polluting agents are discharged in a direction parallel to the work surface and, along this parallel, everything lying past the source of dust is polluted.
  • a vertical plane of this kind is polluted locally only by those sources of pollution which lie upstream of the flow.
  • FIG. 2 shows that, in the case of a vertical flow, the arrangement is similar to that in FIG. 1 but that in this case the air flows in a vertical laminar flow 8 and issues through the work surface 9 which is compulsorily formed by a perforated grid-like surface.
  • the flow is taken up by a blower 3 as in the case of FIG. I and is impelled toward a filter 6 located above the work station.
  • All polluting agents are discharged in a vertical direction and, along this perpendicular at right angles to the work surface, everything lying downwardly of the source of pollution is polluted. In this case there is total independence of the sources of pollution lying in the same horizontal plane. A given vertical plane will be polluted along perpendiculars to the work surface only by such sources as lie thereon.
  • a final example involves the manufacture of certain types of microelectronic circuitry, which must be carried out in a dust-free atmosphere with a relative humidity of under l percent. Such small objects cannot be placed on perforated grids, thereby excluding a vertical flow. Moreover, to use a horizontal flow would be to discharge very dry air at a high rate into the premises, which would soon cause acute discomfort to the operators.
  • such a station comprises a work surface 10 surmounted by a chest formed by an end-wall 11 and a ceiling wall 12, the side walls of the chest being replaced by an air filter 13 on one side and by an offtake grid 14 on the other.
  • a suitable duct 15 containing a blower 16 mounted in an opening in a transverse wall 17 draws off air at 14 and delivers it through 13.
  • a vertical laminar flow 19 generated between a horizontal filter 20 forming an extension of ceiling 12 and a horizontal offtake grid 21 forming an extension of work surface 10.
  • This flow moves parallel to lateral surfaces 22 located on the extensions of portions 13 and 14 and is preferably engendered by a further blower 23 mounted in a transverse partition wall 24 located across a suitable duct 25 enabling air to be sucked through 21 and blown through 20.
  • a blower 23 mounted in a transverse partition wall 24 located across a suitable duct 25 enabling air to be sucked through 21 and blown through 20.
  • the same blower could be used to engender both flows, but a two-blower arrangement permits greater independence of adjustment.
  • the directions of flows l8 and 19 could easily be reversed by interchanging the positions of the filters and the offtake grids without in any way affecting the properties of the system.
  • the laterally circulating horizontal laminar flow 18 is the one which keeps the work surface 10 clean.
  • the work station can be so adjusted as to maintain laminarity over the entire work surface.
  • the principal properties of this flow are the independence of polluting sources lying in a vertical plane perpendicular to the direction of the flow, and also the fact that any horizontal plane can be polluted along horizontal paths perpendicular to filter 13 only by such sources of pollution as lie in that plane.
  • the vertical flow serves a dual purpose From the aerodynamic point of view, it provides a movable wall which must be adjusted so as to allow the horizontal flow 18 to establish and maintain itself all the way to offtake grid 21, there being at the most a narrow eddy zone in which adjacent layers of the two flows mingle over a small depth close to grid 21.
  • a non-limitative embodiment will now be considered by way of example, in which the lateral flow 18 is blown through a filter cell 13 with a section measuring 610 millimeters by 610 millimeters and is drawn through an identical cross-sectional area.
  • Work surface 10 which is 610 millimeters deep, is 1,500 millimeters wide.
  • the mean velocity of the flow 18, as measured by a hot-wire anemometer, is 0.5 meter per second.
  • the vertical flow 19 is blown through an area measuring 30 millimeters by 1,250 millimeters and is drawn out through an identical cross-section. Good adjustment is obtained when the offtake flow rate through 21 is slightly greater than the blowing rate through 20, the surplus air being discharged through a leak orifice downstream of blower 23. This form of adjustment is selected when the aim is to get rid of a specific type of pollution.
  • the air flow rates are 670 mlhr and 1,072 mlhr respectively.
  • they are preferably generated by two blowers supplying two separate circuits, thereby permitting readier adjustmentby virtue of this segregation.
  • Each circuit operates with a continuous recycling process, with or without an input of fresh air (usually drawn from the surrounding air), the tainted air being possibly discharged outside the premises.
  • Both flows may be flows of air or any other gas, either alone or in a mixture.
  • Each circuit may have inserted thereinto absolute filters and layers of activated carbon in order to absorb dangerous vapors. It is likewise possible, and is of especialadvantage in the case of the horizontal flow 18, for the circuits to comprise complete or partial air-conditioning.
  • the flows can be led out from a central airconditioning unit.
  • a dust-free work station is usable for most current applications of hoods utilizing horizontal or vertical flows. It provides a solution to problems which could hitherto be resolved only by the use of glove-boxes, particularly when it is necessary to operate in a clean atmosphere on jobs which generate gaseous or other polluting agents that must not be allowed to escape to the exterior, or when the working atmosphere must exhibit special properties such as a low relative humidity or a low or high temperature, or must contain a special gas that precludes any form of mingling with the environment in the work premises.
  • a dust-free work station comprising, for the purpose of bounding a working space, a set of walls including a generally horizontal work surface having an access opening to said surface in a non-horizontal side of said walls, means for producing a first laminar air current within said space above said work surface moving generally horizontally from one wall side to an opposite wall side, and means for producing a second curtainlike laminar current of air, distinct from said first current, passing in a generally vertical direction over said access opening outside said work space.
  • a work station as claimed in claim 1 wherein said set of walls includes an end-wall opposite said opening, a ceiling wall, and two side walls formed by a diffusion grid and by an offtake grip respectively.
  • a work station as claimed in claim 2 including a second set of walls generally surrounding said first set and providing a second opening arranged in forwardly spaced communicating relation to said first opening, said second current moving vertically in the space betw ens 'dfirs andse ndo ni 4. it wo rk station as c aime 1n c f m 2 wherein said diffusion grid is formed by a dust filter.
  • a work station as claimed in claim 1 including an enclosed conduit extending outside said space with its opposite ends in communication with said grids to provide a circulatory path for said first air current, and air impelling means in said conduit.
  • a work station as claimed in claim 1 including an enclosed conduit extending outside said space and terminating at its opposite ends in mutually facing openings disposed adjacent the upper and lower edges of said access opening, the planes of said mutually facing openings projecting forwardly and generally perpendicularly of the plane of said access opening, to provide a circulatory path for said second air current, and air impelling means in said conduit.

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Ventilation (AREA)
US48172A 1969-06-23 1970-06-22 Dust-free work station with two crossed laminar flows Expired - Lifetime US3686836A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
FR6921026A FR2045223A5 (enrdf_load_stackoverflow) 1969-06-23 1969-06-23

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US3686836A true US3686836A (en) 1972-08-29

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US48172A Expired - Lifetime US3686836A (en) 1969-06-23 1970-06-22 Dust-free work station with two crossed laminar flows

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US (1) US3686836A (enrdf_load_stackoverflow)
DE (1) DE2030565A1 (enrdf_load_stackoverflow)
FR (1) FR2045223A5 (enrdf_load_stackoverflow)

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3880061A (en) * 1973-10-09 1975-04-29 American Air Filter Co Work station
US4371386A (en) * 1981-05-18 1983-02-01 Veco International, Inc. Filter housing
US4427427A (en) 1982-01-19 1984-01-24 Veco S.A. Vertical laminar flow filter module
US4976815A (en) * 1987-04-03 1990-12-11 Tadahiro Ohmi Draft chamber
US5984990A (en) * 1998-02-27 1999-11-16 Mcdonald; Kevin Dustfree workbench for golf club shafts including underlying air filtration system
US6783563B1 (en) * 2002-09-25 2004-08-31 Delta International Machinery Corp. Downdraft dust collector
US6875248B1 (en) * 2002-09-25 2005-04-05 Delta International Machinery Corp. Dust collection cabinet

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2417372A1 (fr) * 1978-02-16 1979-09-14 Hauville Francois Enceinte pour manipulations effectuees sur des produits contaminants ou necessitant une atmosphere sterile

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3113501A (en) * 1961-09-15 1963-12-10 George K Cargo Air door
US3143952A (en) * 1960-08-24 1964-08-11 Dualjet Corp Method and apparatus for conditioning gas
US3367257A (en) * 1965-03-23 1968-02-06 Pyle National Co Air control for white room

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3143952A (en) * 1960-08-24 1964-08-11 Dualjet Corp Method and apparatus for conditioning gas
US3113501A (en) * 1961-09-15 1963-12-10 George K Cargo Air door
US3367257A (en) * 1965-03-23 1968-02-06 Pyle National Co Air control for white room

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3880061A (en) * 1973-10-09 1975-04-29 American Air Filter Co Work station
US4371386A (en) * 1981-05-18 1983-02-01 Veco International, Inc. Filter housing
US4427427A (en) 1982-01-19 1984-01-24 Veco S.A. Vertical laminar flow filter module
US4976815A (en) * 1987-04-03 1990-12-11 Tadahiro Ohmi Draft chamber
US5984990A (en) * 1998-02-27 1999-11-16 Mcdonald; Kevin Dustfree workbench for golf club shafts including underlying air filtration system
US6783563B1 (en) * 2002-09-25 2004-08-31 Delta International Machinery Corp. Downdraft dust collector
US6875248B1 (en) * 2002-09-25 2005-04-05 Delta International Machinery Corp. Dust collection cabinet

Also Published As

Publication number Publication date
DE2030565A1 (de) 1971-01-07
FR2045223A5 (enrdf_load_stackoverflow) 1971-02-26

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