EP0680790A2 - Buse à poudre - Google Patents

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Publication number
EP0680790A2
EP0680790A2 EP95104359A EP95104359A EP0680790A2 EP 0680790 A2 EP0680790 A2 EP 0680790A2 EP 95104359 A EP95104359 A EP 95104359A EP 95104359 A EP95104359 A EP 95104359A EP 0680790 A2 EP0680790 A2 EP 0680790A2
Authority
EP
European Patent Office
Prior art keywords
stream
powder
nozzle
passageway
coating material
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Withdrawn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
EP95104359A
Other languages
German (de)
English (en)
Other versions
EP0680790A3 (fr
Inventor
James A. Darland
Anthony J. Smotherman
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.)
Ransburg Corp
Original Assignee
Ransburg Corp
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 Ransburg Corp filed Critical Ransburg Corp
Publication of EP0680790A2 publication Critical patent/EP0680790A2/fr
Publication of EP0680790A3 publication Critical patent/EP0680790A3/fr
Withdrawn legal-status Critical Current

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05B—SPRAYING APPARATUS; ATOMISING APPARATUS; NOZZLES
    • B05B5/00—Electrostatic spraying apparatus; Spraying apparatus with means for charging the spray electrically; Apparatus for spraying liquids or other fluent materials by other electric means
    • B05B5/025—Discharge apparatus, e.g. electrostatic spray guns
    • B05B5/03—Discharge apparatus, e.g. electrostatic spray guns characterised by the use of gas, e.g. electrostatically assisted pneumatic spraying
    • B05B5/032—Discharge apparatus, e.g. electrostatic spray guns characterised by the use of gas, e.g. electrostatically assisted pneumatic spraying for spraying particulate materials
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05B—SPRAYING APPARATUS; ATOMISING APPARATUS; NOZZLES
    • B05B7/00—Spraying apparatus for discharge of liquids or other fluent materials from two or more sources, e.g. of liquid and air, of powder and gas
    • B05B7/02—Spray pistols; Apparatus for discharge
    • B05B7/08—Spray pistols; Apparatus for discharge with separate outlet orifices, e.g. to form parallel jets, i.e. the axis of the jets being parallel, to form intersecting jets, i.e. the axis of the jets converging but not necessarily intersecting at a point
    • B05B7/0807—Spray pistols; Apparatus for discharge with separate outlet orifices, e.g. to form parallel jets, i.e. the axis of the jets being parallel, to form intersecting jets, i.e. the axis of the jets converging but not necessarily intersecting at a point to form intersecting jets
    • B05B7/0815—Spray pistols; Apparatus for discharge with separate outlet orifices, e.g. to form parallel jets, i.e. the axis of the jets being parallel, to form intersecting jets, i.e. the axis of the jets converging but not necessarily intersecting at a point to form intersecting jets with at least one gas jet intersecting a jet constituted by a liquid or a mixture containing a liquid for controlling the shape of the latter

Definitions

  • This invention relates to the uniform distribution of pulverulent materials, hereinafter generally referred to as powder, in bearing streams. It is disclosed in the context of atomizing and fan shaping nozzles for streams of coating powders, but is believed to be useful in other contexts as well.
  • dispensers for coating powders are known.
  • various dispensers for atomizing and dispensing liquid coating materials are known.
  • No representation is made hereby, nor should such a representation be inferred, that a thorough search of all pertinent prior art has been conducted or that no more pertinent prior art exists.
  • a problem which exists in the dispensing of coating powder is that the coating powder tends not to be uniformly distributed in the stream of bearing fluid, typically compressed air. Effects such as so-called “barber poling," the somewhat helical distribution of the powder borne by the carrier fluid stream, occur in the operation of many coating powder dispensers. Barber poling is quite apparent in the conduit which leads from the powder coating material source, such as a fluidized bed, and the dispenser. If the conduit is transparent or semitransparent, the barber poling can be seen as a somewhat helical distribution of the powder in the conduit.
  • Fan shaping air has long been used in liquid atomization.
  • the liquid stream once atomized either pneumatically, hydraulically or by any other technique into a somewhat cone-shaped cloud, has a stream, typically of compressed air, directed against each of two opposite sides of the cone.
  • the cone is thereby flattened, and the effects of such distributional irregularities as "hollowness" of the cone-shaped cloud, which might otherwise result in a "donut” shaped paint particle distribution on a stationary target, are reduced.
  • Such techniques have been practiced in both electrostatically charged and non-charged applications.
  • a nozzle for increasing the uniformity of distribution of a powder across a bearing fluid stream emanating from the nozzle.
  • the nozzle includes means for attachment of the nozzle to a conduit carrying the bearing fluid stream with the powder entrained in it.
  • the bearing fluid ordinarily will be compressed air, or a compressed air fraction such as carbon dioxide, nitrogen, argon, helium, or the like, or mixtures of selected ones of these.
  • a first passageway is provided through which the bearing fluid stream with the powder entrained in it is emitted. The first passageway is in open communication with the conduit when the bearing fluid stream with the powder entrained in it is to be emitted.
  • the nozzle further includes a pair of second passageways for directing a fluid compatible with the bearing fluid stream with the powder entrained in it onto opposite surfaces of the bearing fluid stream with the powder entrained in it substantially as the bearing fluid stream with the powder entrained in it is emitted from the first passageway.
  • the second passageways are coupled to a source of the compatible fluid. This increases the uniformity of distribution of the powder across the bearing fluid stream.
  • a nozzle for creating and non-contact charging of a stream of coating material particles emanating from the nozzle.
  • the nozzle includes means for attachment of the nozzle to a conduit carrying a coating material stream, and a first passageway through which the coating material stream is emitted.
  • the first passageway is in open communication with the conduit when the coating material stream is to be emitted.
  • a fluid compatible with the coating material stream is directed from a second passageway onto a surface of the stream of coating material particles substantially as the stream of coating material particles is emitted from the first passageway.
  • the second passageway is coupled to a source of the compatible fluid.
  • a charging electrode is disposed at least partly within the second passageway. Means are provided for coupling the charging electrode to a potential source. Flow of the compatible fluid through the second passageway causes charge to be transferred from the charging electrode to the coating material particles as the compatible fluid directed from the second passageway impinges upon the stream of coating material particles.
  • the nozzle further comprises a pair of charging electrodes disposed on opposite sides of the first passageway from each other, and means for coupling the charging electrodes to a source of electrostatic potential.
  • the charging electrodes are at least partly disposed within respective ones of the second passageways.
  • the nozzles of the drawings are intended to be mounted on any suitable dispenser of a stream of a carrier gas, typically air, entraining a coating powder directed at an article to be coated by the powder.
  • a dispenser can be of the so-called manual, that is, hand-triggered and aimed, or automatic, that is, machine-triggered and aimed or stationary, type.
  • An illustrative, but not limiting, example is the dispenser of U.S. Patent 5,022,590.
  • the nozzle 10 of Fig. 1 is one in which the dispensed powder is not electrostatically charged.
  • Such a nozzle 10 can be used, for example, to dispense coating powder onto articles which have been preheated so that the dispensed, typically resin-based, powder will fuse at least to some degree on impact with the preheated articles and stick to them. Ordinarily some subsequent processing of the articles will be undertaken, such as exposure to additional heat to fuse the powder coating more fully and render the coating substantially continuous.
  • the nozzle 10 includes a central passageway 12 through which powder in an entraining air stream 14 is dispensed. Horns 16 are disposed diametrically from each other adjacent passageway 12. A separate channel in the dispenser provides fan air to fan air channels 18 in horns 16. Channels 18 open to atmosphere at locations 20 on opposite sides of the powder entraining air stream 14 exiting from nozzle 10.
  • Air pressure to, and flow 22 from, the channels 18 can be controlled concurrently with, or separately from, the stream 14.
  • the impingement of streams 22 on the opposite sides of stream 14 "homogenizes" the powder particles carried by stream 14, distributing those particles across the transverse section of stream 14 more uniformly and reducing distributional anomalies such as barber poling in the powder borne in stream 14.
  • the nozzle 30 of Figs. 2-3 is one in which the dispensed powder is electrostatically charged.
  • a nozzle 30 can be used, for example, to dispense coating powder onto articles which have not been pretreated so that the dispensed power will stick to them. Instead, the powder is charged by corona discharge from electrodes 32 provided on opposite sides of a central passageway 34 and spaced equidistantly from the two horns 36 with which the nozzle 30 is provided.
  • the powder is typically a resin or porcelain powder and, as such, is not electrically very conductive.
  • the charge which is imparted to it does not readily migrate from it even when the charged powder grains strike a typically grounded, electrically highly conductive, for example, unfinished steel or aluminum, article to be coated by the powder.
  • the powder grains consequently are held on the surfaces of the article by electrostatic attraction until the powder can be fused into a substantially continuous coating by subsequent processing. Ordinarily some subsequent processing of the articles will be undertaken, such as exposure to additional heat to fuse the powder coating and render the coating substantially continuous.
  • the nozzle 30 includes the central passageway 34 through which powder in the entraining air stream 37 is dispensed. Horns 36 are disposed diametrically from each other adjacent passageway 34. A separate channel in the dispenser provides fan air to fan air channels 38 in horns 36. Channels 38 open to atmosphere at locations 40 on opposite sides of the powder entraining air stream 37 exiting from nozzle 30. Air pressure to, and flow 42 from, the channels 38 can be controlled concurrently with, or separately from, the stream 37.
  • the nozzle 50 of Fig. 4 is one in which the dispensed powder is electrostatically charged.
  • the arrangement of Fig. 4 places the electrodes 52 out of the powder laden stream 54 so that the electrodes 52 are not as likely to be eroded by the powder.
  • the nozzle 50 includes the central passageway 56 through which powder in the entraining air stream 54 is dispensed. Horns 58 are disposed diametrically from each other adjacent passageway 56.
  • a separate channel in the dispenser provides fan air to fan air channels 60 in horns 58. Channels 60 open to atmosphere at locations 62 on opposite sides of the powder entraining air stream 54 exiting from nozzle 50. Air pressure to, and flow 64 from, the channels 60 can be controlled concurrently with, or separately from, the stream 54.
  • Electrodes 52 are exposed to the flows 64 in channels 60 and are thus continuously “washed” by flows 64. At the same time, flows 64 pick up charge from electrodes 52 and transfer it to the powder in stream 54 as they impact against the opposite sides of stream 54. This increases the electrical charge-to-mass ratio of the dispensed powder.
  • the impingement of streams 64 on the opposite sides of stream 54 also homogenizes the powder particles carried by stream 54, distributing those particles across the transverse section of stream 54 more uniformly and reducing distributional anomalies in the powder borne in stream 54.
  • Fig. 5 illustrates a system employing the nozzle of Fig. 4.
  • a manual powder dispenser 80 illustrated in broken lines, dispenses a stream of compressed air, entraining a coating powder from a fluidized bed 82 directed at an article 84 to be coated by the powder.
  • the illustrative dispenser 80 is of the general type illustrated and described in U.S. Patent 5,022,590.
  • High electrostatic potential to charge the dispensed powder is provided to the electrodes from an electrostatic potential source 88 through a resistor to a charging ring of the type described in U.S. Patent 5,022,590.
  • the charging ring can be constructed from an electrically conductive or semiconductive filled or unfilled resin.
  • the nozzle itself and its holder ring can be constructed from an electrically non-conductive filled or unfilled resin such as polytetrafluoroethylene. Air pressure to, and flow from, the fan homogenizing channels can be controlled 90 separately from the control 92 of the powder bearing stream.
  • the powder passing through the illustrated nozzles does not contact the air horns through which the shaping and atomizing air is directed onto the dispensed powder stream.
  • Impact fusion the buildup of partially cured or gelled powder caused by heat buildup due to contact friction, on the air horns is thus substantially reduced.
  • Such impact fusion otherwise might cause buildup to a heavy thickness which can then slough off back into the stream of atomized powder and be conveyed to the article being coated and create a blemish in its coating.
  • the charging electrodes are also located outside the powder-bearing air stream.
  • the potential for impact fusion buildup on the electrodes is thus also substantially reduced.
  • the impact fusion of powder on prior art electrodes tended to reduce the charging efficiency of these electrodes. That drop off in efficiency is substantially illuminated by placing the charging electrodes as illustrated in Figs. 2-4.
  • the preferred placement of the electrodes substantially completely within the shaping air channels provides the added benefit of continuously rinsing the electrodes. This ensures that the electrodes supply charge to the atomizing/shaping air stream at substantially their maximum capability for transfer to the atomized powder.

Landscapes

  • Electrostatic Spraying Apparatus (AREA)
EP95104359A 1994-04-05 1995-03-24 Buse à poudre. Withdrawn EP0680790A3 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US222897 1988-07-22
US22289794A 1994-04-05 1994-04-05

Publications (2)

Publication Number Publication Date
EP0680790A2 true EP0680790A2 (fr) 1995-11-08
EP0680790A3 EP0680790A3 (fr) 1996-06-12

Family

ID=22834189

Family Applications (1)

Application Number Title Priority Date Filing Date
EP95104359A Withdrawn EP0680790A3 (fr) 1994-04-05 1995-03-24 Buse à poudre.

Country Status (1)

Country Link
EP (1) EP0680790A3 (fr)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2005018823A3 (fr) * 2003-08-18 2005-09-22 Nordson Corp Pulverisateur pour materiau particulaire
US7150585B2 (en) 2002-10-14 2006-12-19 Nordson Corporation Process and equipment for the conveyance of powdered material
US7793869B2 (en) 2003-08-18 2010-09-14 Nordson Corporation Particulate material applicator and pump
ITBO20130560A1 (it) * 2013-10-14 2015-04-15 Ibix Srl Metodo e apparecchiatura per la spruzzatura a fiamma di polveri termoplastiche

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2446022C3 (de) * 1974-09-26 1985-10-24 ESB Elektrostatische Spritz- und Beflockungsgesellschaft G.F. Vöhringer GmbH, 7758 Meersburg Vorrichtung zum elektrostatischen Beschichten von Gegenständen mit flüssigem oder pulverförmigem Beschichtungsmaterial
FR2605533A1 (fr) * 1986-10-28 1988-04-29 Sames Sa Projecteur de produit pulverulent en suspension dans l'air

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US7150585B2 (en) 2002-10-14 2006-12-19 Nordson Corporation Process and equipment for the conveyance of powdered material
US7478976B2 (en) 2002-10-14 2009-01-20 Nordson Corporation Process and equipment for the conveyance of powdered material
US7481605B2 (en) 2002-10-14 2009-01-27 Nordson Corporation Process and equipment for the conveyance of powdered material
US7648312B2 (en) 2002-10-14 2010-01-19 Nordson Corporation Process and equipment for the conveyance of powdered material
US8057129B2 (en) 2002-10-14 2011-11-15 Nordson Corporation Process and equipment for the conveyance of powdered material
US8491226B2 (en) 2002-10-14 2013-07-23 Nordson Corporation Process and equipment for the conveyance of powdered material
WO2005018823A3 (fr) * 2003-08-18 2005-09-22 Nordson Corp Pulverisateur pour materiau particulaire
US7793869B2 (en) 2003-08-18 2010-09-14 Nordson Corporation Particulate material applicator and pump
US8827191B2 (en) 2003-08-18 2014-09-09 Nordson Corporation Spray applicator with multi-piece housing
ITBO20130560A1 (it) * 2013-10-14 2015-04-15 Ibix Srl Metodo e apparecchiatura per la spruzzatura a fiamma di polveri termoplastiche

Also Published As

Publication number Publication date
EP0680790A3 (fr) 1996-06-12

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