EP0404344A1 - Procédé et appareil de pulvérisation électrostatique - Google Patents

Procédé et appareil de pulvérisation électrostatique Download PDF

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Publication number
EP0404344A1
EP0404344A1 EP90305391A EP90305391A EP0404344A1 EP 0404344 A1 EP0404344 A1 EP 0404344A1 EP 90305391 A EP90305391 A EP 90305391A EP 90305391 A EP90305391 A EP 90305391A EP 0404344 A1 EP0404344 A1 EP 0404344A1
Authority
EP
European Patent Office
Prior art keywords
atomising
edges
electrodes
spacing
edge
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Withdrawn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
EP90305391A
Other languages
German (de)
English (en)
Inventor
Zafirios Vachlas
Stephen James Thorne
Timothy James Noakes
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.)
Imperial Chemical Industries Ltd
Original Assignee
Imperial Chemical Industries 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 Imperial Chemical Industries Ltd filed Critical Imperial Chemical Industries Ltd
Publication of EP0404344A1 publication Critical patent/EP0404344A1/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Withdrawn legal-status Critical Current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
    • B05B5/08—Plant for applying liquids or other fluent materials to objects
    • B05B5/087—Arrangements of electrodes, e.g. of charging, shielding, collecting electrodes
    • 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
    • B05B5/0255—Discharge apparatus, e.g. electrostatic spray guns spraying and depositing by electrostatic forces only

Definitions

  • This invention relates to a process and apparatus for the electrostatic spraying of liquids. More particularly the invention is concerned with a process and apparatus utilising a sprayhead in which liquid is fed along a surface to an edge of the surface, hereafter termed "an atomising edge” and a high voltage is imposed between the atomising edge and a field intensifying electrode, sometimes referred to as a field adjusting electrode spaced from said atomising edge, whereby an atomising field strength is created so that the liquid is atomised at least preponderantly by electrostatic forces to form electrically charged particles which are projected away from said atomising edge.
  • a field intensifying electrode sometimes referred to as a field adjusting electrode spaced from said atomising edge
  • the solution proposed in EP 193348 is to cause a stream of gas to flow through the region of the electrical field, the direction and velocity of the stream of gas being such as to remove charged droplets of liquid from the said region, thereby to reduce any build-up in space charge which affects the magnitude of the electric field.
  • EP 186983 Another solution is proposed in EP 186983. This is to form the field intensifying electrode as a core of conducting or semiconducting material sheathed in a material of dielectric strength sufficiently high to prevent sparking between the electrode and the sprayhead and volume resistivity sufficiently low to allow charge collected on the surface of the sheathing material to be conducted through that material to the conducting or semi-conducting core. It has been found that the use of such an electrode, inter alia enables a higher potential difference to be applied between the sprayhead and field intensifying electrode without disruptive sparking. Hence the flow rate can be increased when such an electrode is used whilst maintaining the desired particle size, since the higher the potential difference, the greater the permitted flow rate for a given particle size.
  • the object of this invention is to further increase the flow rate whilst maintaining a desired particle size.
  • the invention is based upon the very surprising discovery that two atomising edges and their associated field intensifying electrodes can be brought close to each other without substantial uncontrollable electrostatic interference between them.
  • an electrostatic liquid spraying apparatus has a sprayhead comprising a pair of atomising edges extending side by side, liquid feed means to each of said atomising edges, a plurality of field intensifying electrodes extending lengthwise of the atomising edges, a pair of said electrodes being associated with each atomising edge with one disposed on either side thereof and forwardly of the associated atomising edge, and electric power supply means for imposing a potential difference between said atomising edges and said electrodes; and
  • the sprayhead has two atomising edges which can be disposed so close together that they can spray substantially the same area of a target which is moving relatively to the sprayhead within a period of time which is so short that in terms of paint spraying it is equivalent to one spray.
  • the atomising edges are delivering almost twice the number of particles per unit area per unit time as would a single atomising edge.
  • the operating parameters of the apparatus may, be so selected that for a liquid with a viscosity of 8cP and a resistivity of 2 x 108 ohm cm a spray can be achieved with a median particle size diameter not exceeding 100 ⁇ m. at flow rates up to 20 cc/sec/metre length of sprayhead.
  • the spacing of the atomising edges is more than about 300 mm.
  • the spray coating is not laid down properly and results in a mottling or striping effect.
  • the practical space requirements do not allow a spacing between the atomising edges of less than 20 mm.
  • the spacing between the atomising edges is preferably in the range of 20 to 100 mm.
  • the spacing between the atomising edges is preferably in the range 100 to 300 mm.
  • the spacing between each of said electrodes and its associated atomising edge is less than about 3 mm. liquid is deposited on the electrodes and can form a liquid bridge seriously affecting the atomisation. If the spacing is much greater than about 1 cm. then potential gradient is lost and there can be contamination problems which can only be overcome by working at much higher voltages. Ideally, the potential gradient between each said electrode and its associated atomising edge should be as great as possible without reaching break down or contamination.
  • the present invention utilises the sheathed electrode construction disclosed in EP 186983 so that the higher levels of potential gradient within the above specificed range of 1-3 KV per mm. without breakdown can advantageously be achieved.
  • the potential on the two adjacent electrodes, where four are used, or the middle one where three are used may be varied in value with respect to the potential on the two outer electrodes.
  • the potential with respect to earth at the atomising edges is as high as is practical.
  • This compression effect also increases with increase in the lengths of the atomising edges. It has been found that this increase in spray density is very beneficial in achieving a good spray coating.
  • the power supply means preferably is capable of adjustment to supply adjustable potentials to the atomising edges and the field intensifying electrodes. Preferably it is also capable of supplying different potentials to different ones of the field intensifying electrodes.
  • the sprayhead shown in Figure 1 comprises two linear and substantially parallel nozzle assemblies 10 and 11 the edges 12 and 13 of which form respective atomising edges.
  • Each nozzle assembly 10,11 is formed of two plate members 14 and 15 arranged face to face.
  • the facing surfaces are so configured that they butt over their portions 16 but are spaced apart over the remainder to form a liquid flow slot 17 extending over the whole length of the plates 14 and 15 and leading from a gallery 18 to the atomising edge 12,13.
  • One of the facing surfaces extends beyond the other to form a projecting lip 20 leading from the outlet of the slot 17 to the atomising edge 12,13.
  • the edges of the plates 14 and 15 are bevelled as shown.
  • the edges 12 and 13 may be toothed or straight.
  • the gallery 18 comprises a longitudinally extending channel formed in the surface of the plate member 15.
  • Each gallery 18 is connected with a liquid supply source (not shown) through tubes 19.
  • the edges of the plates 14 and 15 could be aligned as shown in Figures 2 to 4.
  • the plates 14 and 15 are of insulating material and to enable an electrical potential to be applied to the liquid feed an electrode 22 is provided in each of the nozzles 10 and 11. Each electrode 22 is positioned adjacent the atomising edge 12, 13 and is located in the facing surface of the plate 15. Each of the electrodes 22 is connected to a high voltage generator through insulated leads 23.
  • the actual potential on the atomising edge 12,13 will depend upon the potential drop between the electrode 22 and the atomising edge 12,13 through the liquid being sprayed.
  • the resistivity of liquid paint is of the order of 107 ohm cm. and at an applied potential of between 40-80KV a potential drop of about 10% can be tolerated.
  • the essential requirement is that the electric field at the atomising edge is sufficient to produce the required ligamentary spray.
  • one or both of the plates 14 and 15 of each nozzle may be made of electrically conducting or semi-conducting material and connected to the high voltage generator.
  • the nozzles 10 and 11 are supported in a suitable frame 25 which also supports three linear electrodes 26,27 and 28, termed herein field intensifying electrodes, but also sometimes referred to as field adjusting electrodes. These electrodes extend substantially parallel to each other and to the atomising edges 12 and 13 with the electrodes 26 and 27 on the outer sides of the atomising edges 12 and 13 and the electrode 28 extending midway between the atomising edges 12 and 13.
  • the electrodes 26 to 28 are disposed forwardly in the spraying direction of the atomising edges 12 and 13. Thus a pair of electrodes 26 and 28 are associated with atomising edge 12 and a pair of electrodes 27 and 28 are associated with atomising edge 13.
  • Each of the electrodes 26 to 28 comprises a core 30 of electrically conducting material such as carbon and a sheath 31 of semi-insulating material such as soda-glass.
  • the resistivity of the sheath is of the order of 1011 ohms cm.
  • the cores 30 of the electrodes may be held at earth potential. Alternatively a voltage with respect to earth may be imposed on them, which voltage creates the desired potential difference between the atomising edges 12 and 13 and the electrodes 26 to 28.
  • Figure 1 the atomising edges are shown spaced apart a distance a .
  • the nearest point on the nozzles 10 and 11 to the surfaces of the associated electrodes 26 to 28 are the atomising edges 12 and 13.
  • the distance between the atomising edges and the surfaces of electrodes 26 to 28 is labelled b in Figure 1.
  • each slot 17 was such as to allow the desired flow rate from each nozzle with a normal reservoir pressure head taking into account the viscosity of the liquid to be sprayed. In this example it was set to deliver at least 10 cc per second per metre length of sprayhead per nozzle of a liquid having a viscosity of 8 cP so that the total liquid delivered per second per metre length of the sprayhead was at least 20 cc.
  • the flow rate was advantageously adjustable to different values.
  • the spacing a between the two atomising edges 12 and 13 was 20 cms. This was so large that it was necessary to use two central electrodes which have been referenced for consistency with the other Figures as 28 a and 28 b .
  • the distance b was 180 mm.
  • the length of each atomising edge was 60 cm.
  • the voltage on the electrode 22 was 80 KV and the voltage on the field intensifying electrodes 26 to 28 was 40 KV.
  • the target surface which was at earth potential was at a distance of 30 cms. from the atomising edges 12 and 13 and moved at a speed equivalent to 1 meter in 19 secs.
  • the liquid paint which was a red grey surfacer used in the automotive industry had a resistivity of 4 x 107 ohms/cm. and a viscosity of about 3 poise. Its flow rate was about 100 cc. per min. through each nozzle.
  • the coat thickness was about 34-60 ⁇ m.
  • FIGs 6a and 6b show a comparison of the spray patterns achieved using the apparatus of Figure 2 and Figure 5.
  • the lengths of the atomising heads and spacings a referred to in Figures 2 and 5 are shown proportionally in Figures 6a and 6b.
  • the spray patterns are shown in contour form so that the closer the contours to each other, the denser the spray pattern. It can be seen that with the longer atomising edges 12 and 13 of Figure 5 the end effect i.e. the end spread is not so pronounced and there is more compression of the spray pattern between the atomising edges. This produces a denser spray which is very advantageous for paint spraying. A similar compression effect can be achieved by increasing the voltage with respect to earth on the electrodes 22.
  • twin nozzle arrangement of the present invention cannot only be arranged to produce a relatively high delivery rate for a given median particle size as described, but can also be used in two component systems which require substantially simultaneous application of the components on to a target, one component being supplied through one nozzle and the other component through the other nozzle.

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  • Electrostatic Spraying Apparatus (AREA)
  • Application Of Or Painting With Fluid Materials (AREA)
EP90305391A 1989-06-23 1990-05-18 Procédé et appareil de pulvérisation électrostatique Withdrawn EP0404344A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB898914506A GB8914506D0 (en) 1989-06-23 1989-06-23 Electrostatic spray process and apparatus
GB8914506 1989-06-23

Publications (1)

Publication Number Publication Date
EP0404344A1 true EP0404344A1 (fr) 1990-12-27

Family

ID=10658980

Family Applications (1)

Application Number Title Priority Date Filing Date
EP90305391A Withdrawn EP0404344A1 (fr) 1989-06-23 1990-05-18 Procédé et appareil de pulvérisation électrostatique

Country Status (9)

Country Link
EP (1) EP0404344A1 (fr)
JP (1) JPH0330848A (fr)
AU (1) AU5762490A (fr)
CA (1) CA2018551C (fr)
GB (2) GB8914506D0 (fr)
IE (1) IE901842A1 (fr)
PT (1) PT94441A (fr)
ZA (1) ZA904001B (fr)
ZW (1) ZW8490A1 (fr)

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1993017794A1 (fr) * 1992-03-05 1993-09-16 United Air Specialists, Inc. Ensemble ajutage de distribution electrostatique
WO1995006521A2 (fr) * 1993-09-02 1995-03-09 Imperial Chemical Industries Plc Dispositif de pulverisation electrostatique
EP0733407A1 (fr) * 1995-03-20 1996-09-25 Sames S.A. Dispositif de projection électrostatique de produit de revêtement
WO2006044876A1 (fr) * 2004-10-20 2006-04-27 The Procter & Gamble Company Buse de pulverisation electrostatique avec orifices de sortie multiples situes a distances variables de la surface cible
WO2006044877A2 (fr) * 2004-10-20 2006-04-27 The Procter & Gamble Company Buse de pulverisation electrostatique pourvue d'electrodes interieures et exterieures
WO2006032018A3 (fr) * 2004-09-14 2006-10-26 Battelle Memorial Institute Aerosols hautement aqueux non respirables contenant des substances biologiquement actives, procede de fabrication et dispositif a cet effet
WO2019140153A1 (fr) * 2018-01-12 2019-07-18 Spraying Systems Co. Ensemble buse de pulvérisation et procédé de mise en forme d'un panache de pulvérisation

Families Citing this family (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
ATE72775T1 (de) * 1987-09-22 1992-03-15 Ici Plc Elektrostatische spruehvorrichtung.
KR100455718B1 (ko) * 2000-01-28 2004-11-08 안강호 분무입자의 유도가 가능한 전기수력학적 분사장치
US7455249B2 (en) * 2006-03-28 2008-11-25 Illinois Tool Works Inc. Combined direct and indirect charging system for electrostatically-aided coating system
JP2009268608A (ja) * 2008-05-02 2009-11-19 Shintaro Tanaka 体内脂肪分解排出法
JP6473629B2 (ja) * 2015-02-09 2019-02-20 アネスト岩田株式会社 静電噴霧装置
JP6494095B2 (ja) * 2015-03-20 2019-04-03 アネスト岩田株式会社 静電噴霧装置
JP6485951B2 (ja) * 2015-03-20 2019-03-20 アネスト岩田株式会社 静電噴霧装置の流量調整方法、及び、その流量調整のできる静電噴霧装置

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1958406A (en) * 1926-12-27 1934-05-15 William A Darrah Electrical spraying device
EP0186983B1 (fr) * 1984-12-20 1989-03-22 Imperial Chemical Industries Plc Pulvérisateur électrostatique

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1958406A (en) * 1926-12-27 1934-05-15 William A Darrah Electrical spraying device
EP0186983B1 (fr) * 1984-12-20 1989-03-22 Imperial Chemical Industries Plc Pulvérisateur électrostatique

Cited By (15)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1993017794A1 (fr) * 1992-03-05 1993-09-16 United Air Specialists, Inc. Ensemble ajutage de distribution electrostatique
US5927618A (en) * 1993-09-02 1999-07-27 The Procter & Gamble Company Electrostatic spraying device
WO1995006521A2 (fr) * 1993-09-02 1995-03-09 Imperial Chemical Industries Plc Dispositif de pulverisation electrostatique
WO1995006521A3 (fr) * 1993-09-02 1995-04-27 Ici Plc Dispositif de pulverisation electrostatique
CN1071144C (zh) * 1993-09-02 2001-09-19 普罗格特-甘布尔公司 静电喷射装置
EP0733407A1 (fr) * 1995-03-20 1996-09-25 Sames S.A. Dispositif de projection électrostatique de produit de revêtement
US5738727A (en) * 1995-03-20 1998-04-14 Sames S.A. Device for electrostatic spraying of a coating product
FR2731921A1 (fr) * 1995-03-20 1996-09-27 Sames Sa Dispositif de projection electrostatique de produit de revetement
WO2006032018A3 (fr) * 2004-09-14 2006-10-26 Battelle Memorial Institute Aerosols hautement aqueux non respirables contenant des substances biologiquement actives, procede de fabrication et dispositif a cet effet
WO2006044876A1 (fr) * 2004-10-20 2006-04-27 The Procter & Gamble Company Buse de pulverisation electrostatique avec orifices de sortie multiples situes a distances variables de la surface cible
WO2006044877A2 (fr) * 2004-10-20 2006-04-27 The Procter & Gamble Company Buse de pulverisation electrostatique pourvue d'electrodes interieures et exterieures
WO2006044877A3 (fr) * 2004-10-20 2006-09-28 Procter & Gamble Buse de pulverisation electrostatique pourvue d'electrodes interieures et exterieures
US7160391B2 (en) 2004-10-20 2007-01-09 The Procter & Gamble Company Electrostatic nozzle apparatus
US7360724B2 (en) 2004-10-20 2008-04-22 The Procter & Gamble Company Electrostatic spray nozzle with internal and external electrodes
WO2019140153A1 (fr) * 2018-01-12 2019-07-18 Spraying Systems Co. Ensemble buse de pulvérisation et procédé de mise en forme d'un panache de pulvérisation

Also Published As

Publication number Publication date
IE901842A1 (en) 1991-01-02
JPH0330848A (ja) 1991-02-08
PT94441A (pt) 1992-02-28
CA2018551A1 (fr) 1990-12-23
GB8914506D0 (en) 1989-08-09
ZW8490A1 (en) 1991-02-27
GB9011465D0 (en) 1990-07-11
CA2018551C (fr) 2000-03-28
IE901842L (en) 1990-12-23
AU5762490A (en) 1991-01-03
ZA904001B (en) 1991-04-24

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