EP0251687A2 - Tête de pulvérisation électrostatique - Google Patents

Tête de pulvérisation électrostatique Download PDF

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Publication number
EP0251687A2
EP0251687A2 EP87305637A EP87305637A EP0251687A2 EP 0251687 A2 EP0251687 A2 EP 0251687A2 EP 87305637 A EP87305637 A EP 87305637A EP 87305637 A EP87305637 A EP 87305637A EP 0251687 A2 EP0251687 A2 EP 0251687A2
Authority
EP
European Patent Office
Prior art keywords
electrode
main body
spray head
spray
head according
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Withdrawn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
EP87305637A
Other languages
German (de)
English (en)
Other versions
EP0251687A3 (fr
Inventor
Kenneth Edward Frampton
Wamadeva Balachandran
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.)
Pharmindev Ltd
Original Assignee
Pharmindev 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 Pharmindev Ltd filed Critical Pharmindev Ltd
Publication of EP0251687A2 publication Critical patent/EP0251687A2/fr
Publication of EP0251687A3 publication Critical patent/EP0251687A3/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Withdrawn legal-status Critical Current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
    • B05B5/043—Discharge apparatus, e.g. electrostatic spray guns using induction-charging
    • 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
    • B05B5/16—Arrangements for supplying liquids or other fluent material
    • B05B5/1608—Arrangements for supplying liquids or other fluent material the liquid or other fluent material being electrically conductive

Definitions

  • This invention relates to an electrostatic spray head for induction charging of conductive liquids.
  • each droplet must be given a significant net electrical charge and secondly that the charged droplets must be acted upon by an electric field.
  • the electrical charge required by a droplet, having a diameter of 50 ⁇ m is typically between 0.5 and 1.5 x 106.
  • the electrostatic field may be self-generated or may be imposed by other adjacent charged bodies such as metallic electrodes or other charged droplets.
  • Electrostatic induction has proven to be a very satisfactory method of charging spray droplets for agriculture and it is the object of the invention to provide an electrostatic spray head for carrying out this method.
  • the level of droplet charge imparted by electrostatic-induction depends upon the time taken to transfer a charge to the droplet-­formation zone in relation to the time required for droplet formation.
  • the charge-transfer capability by conduction from a gounded metal nozzle through the issuing liquid jet depends upon the electrical properties of the liquid forming the continuous jet.
  • this spray-liquid characteristic may be specified by the charge-transfer time constant and it should be less than the droplet formation time in order to be satisfactorily charged by this induction process. Spray liquids less resistive than 106 ohm/m should be charged satisfactorily by the electrostatic-induction method.
  • an electro-­static spray head for propelling a spray of induction-charged droplets, comprises a main body of electrically non-conducting material formed at its rear end for detachable connection to a liquid supply pipe, a spray tube of electrically non-conducting material passing through and detachably secured in the main body with its rear end projecting from the rear end of the body for liquid-tight connection with the liquid supply and its forward end carrying a combined filter and nozzle of metallic material which projects beyond the forward end of the body, an induction electrode assembly detachably secured to the forward end of the body and having an electrically non-conducting housing concentrically surrounding and extending forwardly of the nozzle and carrying, at its forward end, a metal foam electrode spaced from the forward end of the nozzle and in the path of the spray issuing therefrom and an annular counter electrode mounted in the forward part of the body and surrounding the rear part of the nozzle and the induction electrode assembly, said counter electrode being maintained at opposite polarity to the in
  • the electrostatic spray head shown consists mainly of three parts namely, a main body 1, a spray tube 2 and an induction electrode assembly 12 (Fig. 2).
  • the main body 1 is made from non-conductive material and shaped in the form of a bell with a vertical cylindrical section 15 incorporating a recess 22 to hold a sealing ring (not shown). This section is designed to fit directly into a standard connector (not shown) for non-conductive piping. There is an additional recess 23 (Fig. 1) at the top of the main body 1 to locate lugs 24 on the spray tube 2.
  • the main body 1 also houses a counter electrode 5 (Fig. 2) which is a metallic disc designed so as to snap in and out of the main body relatively easily.
  • the electrostatic potential to the counter electrode 5 is applied through a metal insert 6 of L-shaped section to provide the rigidity to withstand the bending forces acting on it.
  • the end 25 of the insert 6 makes contact directly with the electrode 5 using residual compliance to maintain the contact.
  • the other end of the insert 6 is designed to accept a standard spade connector (not shown) for easy release and reconnection.
  • the spray tube 2 is a rigid tube of non-conductive material having a cross member or lugs 24 at its head.
  • This cross member 24 locates in the recess 23 at the top of the main body 1, the two parts being held in position by the standard pipe connector.
  • the other end of the tube 2 is provided with a metallic nozzle 3 incorporating a filter which fits into the end of the tube.
  • Two diametrically opposite flats are provided on the outside of the nozzle body for easy separation of nozzle and filter from the tube.
  • a nozzle-cap 4 made of non-conductive material is provided in order to prevent the metallic surface of the nozzle from being exposed to the inducing electrostatic field.
  • the induction electrode assembly 12 consists of a hollow cylindrical casing 16 of non-conductive material having an outer diameter equal to the width of the central section 17 of the lower end of the main body 1.
  • One end of the casing has embedded therein a metallic ring 9 with internal threads which mate with threads on another metallic ring 8 embedded in the main body 1.
  • the other end of the cylindrical casing 16 is cut away at 18 to leave four symmetrical lobes 13 which engage the convex rear surface of an induction electrode 11 made of metallic foam of a few mm thickness.
  • the sides of the electrode 11 are concave and define between them four lobes or corners 19 which project laterally beyond the walls of the casing 16 when the electrode is secured to the end of the casing with the assistance of four metallic inserts 10.
  • One end of each of the inserts 10 enters apertures 20 (Fig. 4) in the metal ring 9 whereas the other end is soldered in apertures 21 in the induction electrode 11.
  • the electrostatic potential is applied to the induction electrode 11 via a metal insert 7, the rings 8 and 9 and the inserts 10.
  • the ring 8 and the metal insert 7 are both embedded in the main body 1.
  • the spray liquid which is maintained at ground or earth potential, is supplied from a pressurised source to the spray head via the spray tube 2.
  • a liquid film a few mm in diameter and length, is formed at the nozzle orifice 26 which in turn, will break up into droplets as the spray is generated.
  • the induction electrode 11 is arranged concentrially of the liquid film issuing from the nozzle and separated by a few mm therefrom such that the droplet formation zone is well within the width of the induction electrode, to ensure maximum transfer of charge.
  • Positive potential (2 - 6) kv is applied to the induction electrode 11 while maintaining the liquid film at earth potential so that a negative charge will be imparted to the spray droplets by induction.
  • the volume of the secondary droplets sprayed from the lobes is small compared to the main spray.
  • auxiliary gas via pasages 14 in the main body 1 which gas would diffuse through the induction electrode 11 to repel the fine spray tending to coat it.
  • the applied potential and the geometrical positioning of the induction electrode 11 are not unique but any changes that may be incorporated must avoid the onset of corona in the system.
  • the counter electrode 5 is maintained at a negative potential (-2 to -6)kv such that the local electrostatic field set up prevents the spray from fouling the spray head and minimises spray drift.
  • the polarities of both electrodes can be reversed if desired.

Landscapes

  • Electrostatic Spraying Apparatus (AREA)
EP87305637A 1986-06-24 1987-06-24 Tête de pulvérisation électrostatique Withdrawn EP0251687A3 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB868615371A GB8615371D0 (en) 1986-06-24 1986-06-24 Electrostatic spray head
GB8615371 1986-06-24

Publications (2)

Publication Number Publication Date
EP0251687A2 true EP0251687A2 (fr) 1988-01-07
EP0251687A3 EP0251687A3 (fr) 1989-10-04

Family

ID=10599998

Family Applications (1)

Application Number Title Priority Date Filing Date
EP87305637A Withdrawn EP0251687A3 (fr) 1986-06-24 1987-06-24 Tête de pulvérisation électrostatique

Country Status (4)

Country Link
EP (1) EP0251687A3 (fr)
JP (1) JPS6393364A (fr)
AU (2) AU7456987A (fr)
GB (1) GB8615371D0 (fr)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE4312262A1 (de) * 1993-04-15 1994-10-20 Gema Volstatic Ag Elektrostatische Sprühvorrichtung
EP1526921A2 (fr) * 2002-08-06 2005-05-04 Clean Earth Technologies, LLC Procede et dispositif de vaporisation electrostatique
DE102007060211A1 (de) * 2007-12-14 2009-06-18 Itw Gema Gmbh Verfahren und Vorrichtung zum elektrostatischen Sprühbeschichten von Objekten

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2989241A (en) * 1956-07-16 1961-06-20 Ransburg Electro Coating Corp Apparatus for electrostatic spray coating
DE1245810B (de) * 1958-04-04 1967-07-27 Gen Motors Corp Vorrichtung zum elektrostatischen Spritzlackieren
DE1577737A1 (de) * 1966-04-28 1970-07-30 Ransburg Electro Coating Corp Verfahren und Einrichtung zur elektrostatischen Spritzbeschichtung
DE2514117B2 (de) * 1974-04-01 1980-07-10 Ppg Industries, Inc., Pittsburgh, Pa. (V.St.A.) Vorrichtung zum elektrostatischen Aufsprühen von Überzugsmassen
US4228961A (en) * 1979-05-07 1980-10-21 Onoda Cement Co., Ltd. Electrostatic power painting head

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2989241A (en) * 1956-07-16 1961-06-20 Ransburg Electro Coating Corp Apparatus for electrostatic spray coating
DE1245810B (de) * 1958-04-04 1967-07-27 Gen Motors Corp Vorrichtung zum elektrostatischen Spritzlackieren
DE1577737A1 (de) * 1966-04-28 1970-07-30 Ransburg Electro Coating Corp Verfahren und Einrichtung zur elektrostatischen Spritzbeschichtung
DE2514117B2 (de) * 1974-04-01 1980-07-10 Ppg Industries, Inc., Pittsburgh, Pa. (V.St.A.) Vorrichtung zum elektrostatischen Aufsprühen von Überzugsmassen
US4228961A (en) * 1979-05-07 1980-10-21 Onoda Cement Co., Ltd. Electrostatic power painting head

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE4312262A1 (de) * 1993-04-15 1994-10-20 Gema Volstatic Ag Elektrostatische Sprühvorrichtung
EP1526921A2 (fr) * 2002-08-06 2005-05-04 Clean Earth Technologies, LLC Procede et dispositif de vaporisation electrostatique
DE102007060211A1 (de) * 2007-12-14 2009-06-18 Itw Gema Gmbh Verfahren und Vorrichtung zum elektrostatischen Sprühbeschichten von Objekten

Also Published As

Publication number Publication date
GB8615371D0 (en) 1986-07-30
AU7467287A (en) 1988-01-07
JPS6393364A (ja) 1988-04-23
EP0251687A3 (fr) 1989-10-04
AU7456987A (en) 1988-01-07

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Inventor name: BALACHANDRAN, WAMADEVA

Inventor name: FRAMPTON, KENNETH EDWARD