US3871580A - Electrostatic spraying - Google Patents

Electrostatic spraying Download PDF

Info

Publication number
US3871580A
US3871580A US386618A US38661873A US3871580A US 3871580 A US3871580 A US 3871580A US 386618 A US386618 A US 386618A US 38661873 A US38661873 A US 38661873A US 3871580 A US3871580 A US 3871580A
Authority
US
United States
Prior art keywords
powder
corona discharge
discharge device
elongate means
tube
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.)
Expired - Lifetime
Application number
US386618A
Inventor
Morris James Legge
John Alastair Phipps
Roger Patrick Corbett
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.)
Plascoat Systems Ltd
Original Assignee
Plastic Coatings 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 Plastic Coatings Ltd filed Critical Plastic Coatings Ltd
Application granted granted Critical
Publication of US3871580A publication Critical patent/US3871580A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

Images

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

Definitions

  • ABSTRACT [30] Foreign Application Priority Data i an electcrlosltlatic i gs p qy pp i p g is conveye t roug a te ectrlc tu e to a corona 15- 1972 Umted Kmgdom charge device by vibratory motion of the tube.
  • the [52] U S Cl 239/3 239/15 317/3 powder is dispersed in a cloud downstream of the co- [51] Bosb 5/02 rona discharge device by a vibrating member at the [58] end of the tube.
  • an apparatus for electrostatic powder spraying comprising a corona discharge device and a powder dispenser for conveying powder to the corona discharge device characterised in that the powder is conveyed along or through the dispenser solely by vibratory motion of the dispenser.
  • the dispenser comprises a dielectric tube having an open end for discharge and an inlet for receiving powder adjacent its opposite end, and means for vibrating the tube whereby powder fed to the tube is caused to flow along the tube to the corona discharge device.
  • a vibratable member for dispensing the powder in a cloud in the vicinity of the corona discharge device.
  • the vibratable member preferably comprises a plate adjacent the open end of the tube and vibratable in a plane substantially at right angles to the longitudinal axis of the tube.
  • the vibratable member and the corona discharge device are preferably located on an extension member attached to the open end of the tube, the vibration of the vibratable member being provided by a component of the vibration of the tube.
  • Part of the corona discharge device may provide the vibratable member.
  • the tube may be vibrated at a frequency of between and 200 Hz, preferablySO Hz at an amplitude of approximately 1 mm.
  • the dispenser may be located above and separately from the corona discharge device so that powder falling from the dispenser past the discharge device becomes electrostatically charged.
  • a method of electrostatic powder spraying comprising supplying a stream of powder particles to a corona discharge device solely by vibrating them along a vibrating dielectric tube and dispersing them in a cloud downstream of the corona discharge device by means of a vibrating member.
  • FIG. 1 is a side elevation of an electrostatic powder spraying apparatus according to the invention
  • FIG. 2 is a plan view of a discharge portion of the apparatus shown in FIG. 1,
  • FIG. 3 is a diagrammatic representation of an electrostatic powder spraying apparatus according to another aspect of the invention.
  • an electrostatic spraying apparatus or spray gun, comprising a vibrator tube of dielectric material, e.g., Perspex (Reg. Trade Mark), of about 1 inches internal diameter, which is clamped by means of clamps ll, 12 to a vibrator machine 13.
  • the dispositionof the clamps 11, I2 and the vibrator machine 13 are such that the tube 10 vibrates along its longitudinal axis in the directions indicated by the arrow 14, and because of inherent tolerances in the mechanism, also has a component of vibration at right angles to its longitudinal axis.
  • an inlet tube 15 In the Perspex tube 10, near one'end, is an inlet tube 15 through which powder may be fed in the direction shown by arrow 16.
  • a clamp 17 held to the other, open, end of the tube 10 by a clamp 17 is an extension member provided by a divergent guide plate 18 downstream 18 to the of which is attached a corona discharge element 19 and a vibratable member in the form of a thin brass flap 20 which extends in line with the tube 10.
  • the corona discharge element is maintained at a high potential by means of a high tension voltage supply line 21 fed from a high voltage source 9.
  • epoxy resin powder of a particle size such that 50 percent is less than 50a is gravity fed into the tube 10 by way of the supply tube 15.
  • the tube 10 is held in a horizontal position, and is vibrated by the vibrator 13 at a frequency of 50 Hz and at a longitudinal amplitude of about 1 mm. This vibration causes the powder in the tube to move in the direction of the arrow 22 onto the guide plate 18.
  • the particles are charged partly by contact with the guide plate 18, which is maintained at a potential of about 48 kV, and mainly by ion bombardment in the region in front of the discharge element 19. They are then accelerated by the electric field created between the discharge element 19 and the earthed object 23 to be coated by the powder, and are propelled on to this object 23.
  • the vertical component of vibration of the Perspex tube 10 causes the brass flap 20 to vibrate sympathetically in a plane perpendicular to the plane of vibration of the tube 10 as indicated by the arrows 24.
  • the effect of the vibrating flap 20 is to disperse the powder in a cloud and enable the powder particles more readily to take up their electrostatic charge.
  • typical rates of flow of the powder through the spray gun described above may vary between 27 and 123 grammes per minute.
  • the powder 33 is dispensed from a grounded metal vibratory dispenser 30, which is maintained well clear of the charging electrode 31, and is allowed to fall past the charging electrode where it is charged and deposited on the object 32 to be coated.
  • the invention provides an apparatus for and a method of airless electrostatic spraying of powder, airless in the context of the present invention being understood to mean that a moving stream of air or other fluid is not used as the means for conveying electrostatically charged powder particles to an object to be sprayed.
  • An advantage of the present invention over known electrostatic powder spray guns in which the powder is carried to the article to be coated partly by an air or other fluid stream is that the need for an air supply is eliminated and the danger of particles being carried in the air stream beyond the article to be coated is minimized. Furthermore, a flow of air is a possible source of powder contamination (oil or water) and is an additional variable when consistency of coating thickness is the aim. Consequently, the airless spray gun of the present invention is more efficient in that it is capable of depositing a larger proportion of its through-put of powder on the object to be coated than other guns so far commercially available.
  • corona discharge element 19 may be omitted and the high tension voltage supply line 21 attached directly to the brass flap 20 which then generates the required electrostatic field.
  • the flap 20 may be made of a material other than brass provided it is able to vibrate sufficiently to disperse the powder stream in a cloud of particles.
  • the frequency at which the vibrator operates may suitably lie in the range 5 to 200 Hz.
  • the tube may be replaced by an open channel.
  • An apparatus for airless electrostatic powder spraying comprising a corona discharge device, a vibratory dielectric hollow elongate means for conveying powder to the corona discharge device, the elongate means having an open end for delivering powder to the corona discharge device and an inlet for receiving powder adjacent its opposite end, means for vibrating the elongate means such that powder fed to the elongate means is caused to flow therealong to the corona discharge device, and a vibratable member for dispersing the powder in a cloud in the vicinity of the corona discharge device.
  • An apparatus as claimed in claim 1 wherein the elongate means comprises an open channel.
  • the vibratable member comprises a plate adjacent the open end of the elongate means and vibratable in a plane substantially at right angles to the longitudinal axis of the elongate means.
  • a method of electrostatic powder spraying comprising supplying a stream of powder particles to a corona discharge device solely by vibrating them along a vibrating dielectric tube and dispersing them in a cloud downstream of the corona discharge device by means of a vibrating member.

Abstract

In an electrostatic powder spraying apparatus, powder is conveyed through a dielectric tube to a corona discharge device by vibratory motion of the tube. The powder is dispersed in a cloud downstream of the corona discharge device by a vibrating member at the end of the tube.

Description

United States Patent Field of Search 239/3, 15; 222/199, 200; i 117/93.4 R;317/3 Legge et a1. Mar. 18, 1975 ELECTROSTATIC SPRAYING [75] Inventors: Morris James Legge, Farnham; [56] References C'ted 19h! Ab teirii t rit iliert qettzhs; UNITED STATES PATENTS Roger Patrick Corbett, 2,550,852 12/1970 Southampton, all of England ,38 ,050 5/1 68 3,496,911 2/1970 [73] Assignees: Plastic Coatings Limited, Surrey, 3558952 H1971 Y England; University of 3,637,135 1/1972 Luderer et a1. 239/3 Southampton, Southampton, v England Primary Examiner-Robert S. Ward, Jr 7 Assistant Examiner-Michae1 Mar [22] Flled' 1973 Attorney, Agent, or FirmLarson, Taylor & Hinds [21] v Appl. No.: 386,618
[57] ABSTRACT [30] Foreign Application Priority Data i an electcrlosltlatic i gs p qy pp i p g is conveye t roug a te ectrlc tu e to a corona 15- 1972 Umted Kmgdom charge device by vibratory motion of the tube. The [52] U S Cl 239/3 239/15 317/3 powder is dispersed in a cloud downstream of the co- [51] Bosb 5/02 rona discharge device by a vibrating member at the [58] end of the tube.
7 Claims, 3 Drawing Figures ELECTROSTATIC SPRAYING This invention relates to an apparatus for electrostatic powder spraying and to a method of electrostatic powder spraying.
According to one aspect of the present invention there is provided an apparatus for electrostatic powder spraying comprising a corona discharge device and a powder dispenser for conveying powder to the corona discharge device characterised in that the powder is conveyed along or through the dispenser solely by vibratory motion of the dispenser.
Preferably the dispenser comprises a dielectric tube having an open end for discharge and an inlet for receiving powder adjacent its opposite end, and means for vibrating the tube whereby powder fed to the tube is caused to flow along the tube to the corona discharge device.
Preferably there is further provided a vibratable member for dispensing the powder in a cloud in the vicinity of the corona discharge device.
The vibratable member preferably comprises a plate adjacent the open end of the tube and vibratable in a plane substantially at right angles to the longitudinal axis of the tube.
The vibratable member and the corona discharge device are preferably located on an extension member attached to the open end of the tube, the vibration of the vibratable member being provided by a component of the vibration of the tube.
Part of the corona discharge device may provide the vibratable member.
The tube may be vibrated at a frequency of between and 200 Hz, preferablySO Hz at an amplitude of approximately 1 mm.
The dispenser may be located above and separately from the corona discharge device so that powder falling from the dispenser past the discharge device becomes electrostatically charged.
According to another aspect of the invention there is provided a method of electrostatic powder spraying comprising supplying a stream of powder particles to a corona discharge device solely by vibrating them along a vibrating dielectric tube and dispersing them in a cloud downstream of the corona discharge device by means of a vibrating member.
The invention will now be described by way of example with reference to the diagrammatic accompanying drawings in which FIG. 1 is a side elevation of an electrostatic powder spraying apparatus according to the invention,
FIG. 2 is a plan view of a discharge portion of the apparatus shown in FIG. 1,
FIG. 3 is a diagrammatic representation of an electrostatic powder spraying apparatus according to another aspect of the invention.
Referring to the drawings there is shown an electrostatic spraying apparatus, or spray gun, comprising a vibrator tube of dielectric material, e.g., Perspex (Reg. Trade Mark), of about 1 inches internal diameter, which is clamped by means of clamps ll, 12 to a vibrator machine 13. The dispositionof the clamps 11, I2 and the vibrator machine 13 are such that the tube 10 vibrates along its longitudinal axis in the directions indicated by the arrow 14, and because of inherent tolerances in the mechanism, also has a component of vibration at right angles to its longitudinal axis.
In the Perspex tube 10, near one'end, is an inlet tube 15 through which powder may be fed in the direction shown by arrow 16.
Held to the other, open, end of the tube 10 by a clamp 17 is an extension member provided by a divergent guide plate 18 downstream 18 to the of which is attached a corona discharge element 19 and a vibratable member in the form of a thin brass flap 20 which extends in line with the tube 10.
The corona discharge element is maintained at a high potential by means of a high tension voltage supply line 21 fed from a high voltage source 9.
In a non-limiting example, epoxy resin powder of a particle size such that 50 percent is less than 50a is gravity fed into the tube 10 by way of the supply tube 15. The tube 10 is held in a horizontal position, and is vibrated by the vibrator 13 at a frequency of 50 Hz and at a longitudinal amplitude of about 1 mm. This vibration causes the powder in the tube to move in the direction of the arrow 22 onto the guide plate 18.
The particles are charged partly by contact with the guide plate 18, which is maintained at a potential of about 48 kV, and mainly by ion bombardment in the region in front of the discharge element 19. They are then accelerated by the electric field created between the discharge element 19 and the earthed object 23 to be coated by the powder, and are propelled on to this object 23.
The vertical component of vibration of the Perspex tube 10 causes the brass flap 20 to vibrate sympathetically in a plane perpendicular to the plane of vibration of the tube 10 as indicated by the arrows 24. The effect of the vibrating flap 20 is to disperse the powder in a cloud and enable the powder particles more readily to take up their electrostatic charge.
In this example, typical rates of flow of the powder through the spray gun described above may vary between 27 and 123 grammes per minute.
In another embodiment of the invention, shown in FIG. 3, the powder 33 is dispensed from a grounded metal vibratory dispenser 30, which is maintained well clear of the charging electrode 31, and is allowed to fall past the charging electrode where it is charged and deposited on the object 32 to be coated.
It is thus seen that the invention provides an apparatus for and a method of airless electrostatic spraying of powder, airless in the context of the present invention being understood to mean that a moving stream of air or other fluid is not used as the means for conveying electrostatically charged powder particles to an object to be sprayed.
An advantage of the present invention over known electrostatic powder spray guns in which the powder is carried to the article to be coated partly by an air or other fluid stream is that the need for an air supply is eliminated and the danger of particles being carried in the air stream beyond the article to be coated is minimized. Furthermore, a flow of air is a possible source of powder contamination (oil or water) and is an additional variable when consistency of coating thickness is the aim. Consequently, the airless spray gun of the present invention is more efficient in that it is capable of depositing a larger proportion of its through-put of powder on the object to be coated than other guns so far commercially available.
In an alternative embodiment the corona discharge element 19 may be omitted and the high tension voltage supply line 21 attached directly to the brass flap 20 which then generates the required electrostatic field.
The flap 20 may be made of a material other than brass provided it is able to vibrate sufficiently to disperse the powder stream in a cloud of particles.
The frequency at which the vibrator operates may suitably lie in the range 5 to 200 Hz.
The tube may be replaced by an open channel.
What we claim is:
1. An apparatus for airless electrostatic powder spraying comprising a corona discharge device, a vibratory dielectric hollow elongate means for conveying powder to the corona discharge device, the elongate means having an open end for delivering powder to the corona discharge device and an inlet for receiving powder adjacent its opposite end, means for vibrating the elongate means such that powder fed to the elongate means is caused to flow therealong to the corona discharge device, and a vibratable member for dispersing the powder in a cloud in the vicinity of the corona discharge device.
2. An apparatus as claimed in claim 1 wherein the elongate means comprises a tube.
3. An apparatus as claimed in claim 1 wherein the elongate means comprises an open channel.
4. An apparatus as claimed in claim 1 wherein the vibratable membercomprises a plate adjacent the open end of the elongate means and vibratable in a plane substantially at right angles to the longitudinal axis of the elongate means.
5. An apparatus as claimed in claim 1 wherein the vibratable member and the corona discharge device are located on an extension member attached to the open end of the elongate means, the vibration of the vibratable member being provided by a component of the vibration of the elongate means.
6. An apparatus as claimed in claim 1 wherein part of the corona discharge device provides the vibratable member.
7. A method of electrostatic powder spraying comprising supplying a stream of powder particles to a corona discharge device solely by vibrating them along a vibrating dielectric tube and dispersing them in a cloud downstream of the corona discharge device by means of a vibrating member.

Claims (7)

1. An apparatus for airless electrostatic powder spraying comprising a corona discharge device, a vibratory dielectric hollow elongate means for conveying powder to the corona discharge device, the elongate means having an open end for delivering powder to the corona discharge device and an inlet for receiving powder adjacent its opposite end, means for vibrating the elongate means such that powder fed to the elongate means is caused to flow therealong to the corona discharge device, and a vibratable member for dispersing the powder in a cloud in the vicinity of the corona discharge device.
2. An apparatus as claimed in claim 1 wherein the elongate means comprises a tube.
3. An apparatus as claimed in claim 1 wherein the elongate means comprises an open channel.
4. An apparatus as claimed in claim 1 wherein the vibratable member comprises a plate adjacent the open end of the elongate means and vibratable in a plane substantially at right angles to the longitudinal axis of the elongate means.
5. An apparatus as claimed in claim 1 wherein the vibratable member and the corona discharge device are located on an extension member attached to the open end of the elongate means, the vibration of the vibratable member being provided by a component of the vibration of the elongate means.
6. An apparatus as claimed in claim 1 wherein part of the corona discharge device provides the vibratable member.
7. A method of electrostatic powder spraying comprising supplying a stream of powder particles to a corona discharge device solely by vibrating them along a vibrating dielectric tube and dispersing them in a cloud downstream of the corona discharge device by means of a vibrating member.
US386618A 1972-08-10 1973-08-08 Electrostatic spraying Expired - Lifetime US3871580A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB3730672A GB1435512A (en) 1972-08-10 1972-08-10 Electrostatic spraying

Publications (1)

Publication Number Publication Date
US3871580A true US3871580A (en) 1975-03-18

Family

ID=10395432

Family Applications (1)

Application Number Title Priority Date Filing Date
US386618A Expired - Lifetime US3871580A (en) 1972-08-10 1973-08-08 Electrostatic spraying

Country Status (5)

Country Link
US (1) US3871580A (en)
JP (1) JPS49132123A (en)
CH (1) CH572768A5 (en)
FR (1) FR2195918A5 (en)
GB (1) GB1435512A (en)

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2543575A1 (en) * 1975-09-30 1977-04-07 Brennenstuhl Kg Hugo PROCESS FOR COATING OBJECTS WITH POWDER-ORGANIC PARTICLES OR FLAKES OR FIBERS AND DEVICE FOR CARRYING OUT THIS PROCEDURE
DE102013114384A1 (en) * 2013-12-18 2015-06-18 Ip Plasma & Brands Gmbh Apparatus and method for feeding and dosing fine powder

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2550852A (en) * 1946-03-29 1951-05-01 Nat Lock Co Catch
US3384050A (en) * 1963-02-19 1968-05-21 Sames Sa De Machines Electrost Electrostatic coating system
US3496911A (en) * 1968-07-22 1970-02-24 Velvetex Ind Corp Electrostatic flocking
US3558052A (en) * 1968-10-31 1971-01-26 F I N D Inc Method and apparatus for spraying electrostatic dry powder
US3637135A (en) * 1968-04-26 1972-01-25 Atlas Copco Ab Method of and apparatus for spray coating components

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2550852A (en) * 1946-03-29 1951-05-01 Nat Lock Co Catch
US3384050A (en) * 1963-02-19 1968-05-21 Sames Sa De Machines Electrost Electrostatic coating system
US3637135A (en) * 1968-04-26 1972-01-25 Atlas Copco Ab Method of and apparatus for spray coating components
US3496911A (en) * 1968-07-22 1970-02-24 Velvetex Ind Corp Electrostatic flocking
US3558052A (en) * 1968-10-31 1971-01-26 F I N D Inc Method and apparatus for spraying electrostatic dry powder

Also Published As

Publication number Publication date
JPS49132123A (en) 1974-12-18
CH572768A5 (en) 1976-02-27
DE2336458B2 (en) 1975-09-11
DE2336458A1 (en) 1974-02-28
FR2195918A5 (en) 1974-03-08
GB1435512A (en) 1976-05-12

Similar Documents

Publication Publication Date Title
EP0085149B1 (en) Process and apparatus for electrostatic application of liquids or powders on substances or objects
US3558052A (en) Method and apparatus for spraying electrostatic dry powder
US3991710A (en) Electrogasdynamic production line coating system
US4343828A (en) Electrodynamic painting system and method
US3085749A (en) Electrostatic spray heads
US3698636A (en) Device for the electrostatic application of protective coatings with synthetic powders by the use of spray guns
US3791341A (en) Electrostatic resin powder spray system
GB605338A (en) Method and apparatus for electrostatically coating articles
US3512502A (en) Electrostatic coating apparatus
US3521815A (en) Guns for the electrostatic spray coating of objects with a powder
DK147907B (en) MOISTURIZING DEVICE AND / OR DISPOSAL OF ELECTRICALLY INSULATED ITEMS AND MATERIALS
SE438966B (en) SPRAY DEVICE FOR POWDER WITH SPRAY GAS SPECIFICALLY INTRODUCED IN THE NOZZLE OPENING
US3384050A (en) Electrostatic coating system
US2881092A (en) Spray device actuated by supersonic means
US3010428A (en) Spraying devices
US3678336A (en) Electrostatic powder striping applicator
US3871580A (en) Electrostatic spraying
US3585060A (en) Electrogasdynamic particle deposition systems
US5820941A (en) Powder spray coating
GB834275A (en) Electrostatic spraying installation
US3051394A (en) Electrostatic spray coating apparatus and method
US20050287306A1 (en) Process for electrostatic powder coating an article using triboelectrically charged powder with air jet assist
US3793049A (en) Electrostatic coating method
JP3362230B2 (en) Electrostatic powder coating equipment
US2847324A (en) Method and apparatus for control of charged particles in electrostatic machines