GB2047567A - Coating with particulate material - Google Patents

Coating with particulate material Download PDF

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Publication number
GB2047567A
GB2047567A GB8008964A GB8008964A GB2047567A GB 2047567 A GB2047567 A GB 2047567A GB 8008964 A GB8008964 A GB 8008964A GB 8008964 A GB8008964 A GB 8008964A GB 2047567 A GB2047567 A GB 2047567A
Authority
GB
United Kingdom
Prior art keywords
particles
chamber
air
gas
charging
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.)
Granted
Application number
GB8008964A
Other versions
GB2047567B (en
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.)
Dodd K H
NAYLOR N
Original Assignee
Dodd K H
NAYLOR N
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 Dodd K H, NAYLOR N filed Critical Dodd K H
Priority to GB8008964A priority Critical patent/GB2047567B/en
Publication of GB2047567A publication Critical patent/GB2047567A/en
Application granted granted Critical
Publication of GB2047567B publication Critical patent/GB2047567B/en
Expired legal-status Critical Current

Links

Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05B—SPRAYING APPARATUS; ATOMISING APPARATUS; NOZZLES
    • B05B13/00—Machines or plants for applying liquids or other fluent materials to surfaces of objects or other work by spraying, not covered by groups B05B1/00 - B05B11/00
    • B05B13/02—Means for supporting work; Arrangement or mounting of spray heads; Adaptation or arrangement of means for feeding work
    • B05B13/0278—Arrangement or mounting of spray heads
    • 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
    • B05B5/047—Discharge apparatus, e.g. electrostatic spray guns using tribo-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
    • B05B5/08—Plant for applying liquids or other fluent materials to objects
    • 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
    • B05B7/14—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 designed for spraying particulate materials
    • B05B7/1481—Spray pistols or apparatus for discharging particulate material
    • B05B7/1486—Spray pistols or apparatus for discharging particulate material for spraying particulate material in dry state
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D1/00—Processes for applying liquids or other fluent materials
    • B05D1/02—Processes for applying liquids or other fluent materials performed by spraying
    • B05D1/04—Processes for applying liquids or other fluent materials performed by spraying involving the use of an electrostatic field
    • B05D1/06—Applying particulate materials
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D1/00—Processes for applying liquids or other fluent materials
    • B05D1/30—Processes for applying liquids or other fluent materials performed by gravity only, i.e. flow coating
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D3/00—Pretreatment of surfaces to which liquids or other fluent materials are to be applied; After-treatment of applied coatings, e.g. intermediate treating of an applied coating preparatory to subsequent applications of liquids or other fluent materials
    • B05D3/02—Pretreatment of surfaces to which liquids or other fluent materials are to be applied; After-treatment of applied coatings, e.g. intermediate treating of an applied coating preparatory to subsequent applications of liquids or other fluent materials by baking
    • B05D3/0218—Pretreatment, e.g. heating the substrate
    • B05D3/0245—Pretreatment, e.g. heating the substrate with induction heating
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D1/00—Processes for applying liquids or other fluent materials
    • B05D1/007—Processes for applying liquids or other fluent materials using an electrostatic field
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D2401/00—Form of the coating product, e.g. solution, water dispersion, powders or the like
    • B05D2401/30—Form of the coating product, e.g. solution, water dispersion, powders or the like the coating being applied in other forms than involving eliminable solvent, diluent or dispersant
    • B05D2401/32—Form of the coating product, e.g. solution, water dispersion, powders or the like the coating being applied in other forms than involving eliminable solvent, diluent or dispersant applied as powders

Landscapes

  • Application Of Or Painting With Fluid Materials (AREA)
  • Electrostatic Spraying Apparatus (AREA)

Abstract

A method and an apparatus for coating a surface of an article. The apparatus comprises a chamber (10) with an inlet (14) connected to a source of thermosetting or/and thermoplastics powder, for example powder paint, entrained in a stream of air or gas, and a plurality of outlets (16) arranged to direct particles of powder entrained in air or gas issuing from them towards the surface to be coated. The velocity of the air or gas is reduced as it passes through the chamber by creating a low pressure zone in the chamber by a cyclone effect. The particles are charged electrostatically, for example by triboelectric charging, to assist their adhesion to the surface. The chamber has a radio frequency induction heater (17) arranged to heat the surface so that the particles adhere to it and fuse to form a coating thereon. <IMAGE>

Description

SPECIFICATION Coating method and apparatus This invention relates to the coating of articles and in particular is concerned with a method and an apparatus for this purpose.
According to a first aspect of the invention there is provided a method of coating a surface of an article comprising directing particles of a thermosetting or/and thermoplastics powder towards the surface and simultaneously heating the surface so that particles adhere to the surface and fuse to form a coating thereon.
Preferably the surface is heated by subjecting it to radio frequency induction heating.
The particles are preferably charged electrostatically to assist their adhesion to the surface.
The particles may be directed towards the surface by allowing them to fall on to the surface under gravity but preferably the particles are entrained in a stream of air or gas at a relatively low velocity. In both cases, the direction of the particles towards the surface is assisted by electrostatic charging of the particles.
Electrostatic charging of the particles may be effected by causing them, in thier passage towards the surface, to pass through a corona discharge or by causing the particles to rub against a surface of a material which is such as to charge them by triboelectric charging.
The radio frequency of the induction heating is selected according to the material of the surface to be coated. Thus, the example, in the case of a surface of a ferrous material a relatively low frequency is sufficient to induce an electric current in the article such as to heat at least the surface thereof, but a higher frequency is required for a surface of a plastics material.
The powder may comprise particles of a thermosetting material only or particles of a thermoplastics material only or a mixture of such particles.
According to a second aspect of the invention there is provided an apparatus for coating a surface of an article which comprises means for directing particles of a thermosetting or/ and thermoplastics powder towards the surface and means for simultaneously heating the surface whereby particles adhere to the surface and fuse to form a coating thereon.
The heating means preferably comprise a radio frequency induction heater.
Preferably the apparatus is provided with means for charging the particles electrostatistically.
The apparatus preferably comprises a chamber having an inlet connected, in use, to a source of powder entrained in a stream of air or gas, and an outlet or outlets positioned, in use, to direct particles of the powder entrained in the air or gas issuing from the outlet(s) towards the surface to be coated.
The stream of air or gas conveying the particles to the chamber may have a velocity greater than that required for direction of the particles towards the surface to be coated. In this regard, it is important that the velocity of the air or gas flow directing the particles towards the surface is as low as possible.
Preferably, therefore, the chamber is formed to reduce the velocity of the air or gas flow as it passes through it.
The chamber may be of cylindrical form with the inlet arranged so that the incoming air or gas is caused to flow around the chamber in the manner of a cyclone thereby creating a low pressure zone in the centre, the outlet or outlets being disposed in this zone so that air or gas issues through the outlet(s) from said zone at a relatively low velocity, the chamber being provided with one or more further outlets enabling surplus air or gas to escape from the chamber.
The radio frequency induction heater comprises an element, for example in the form of a flat coil or serpentine, connected or connectible to a radio frequency wave generator.
This element is conveniently mounted inside the chamber, although it could be disposed outside and adjacent to the chamber. In any event, the chamber is made of a material or materials such that it is not heated by the electromagnetic waves emitted by the element.
The means for charging the particles electrostatically may comprise a generator arranged to produce a corona discharge in a zone through which the particles pass, for example inside the chamber. Preferably, however the chamber or a conduit conveying the particles to the chamber has at least a portion thereof arranged so that the particles rub against it and formed of a material such that the rubbing action charges the particles by triboelectric charging.
The chamber preferably has a plurality of outlets which may be, for example, slits or circular apertures.
The method and apparatus of the invnetion are particularly suitable for coating articles with powder paint.
The invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a section through one form of coating apparatus embodying the invention, and Figure 2 shows the apparatus of Fig. 1 mounted on a remote-controlled arm for the painting of, for example, the body of a motor car.
The coating apparatus illustrated in the drawings comprises a chamber 10 defined by a cylindrical side wall 11 and two domeshaped end walls 12 and 1 3. The walls 11 and 1 3 are made of a plastics material, for example polyvinylchloride, polyethylene, a polyamide or an acrylic, and the wall 1 2 is of a porous ceramic material.
The chamber has an inlet 1 4 which is connected to a conduit 1 5 to a source of powder entrained in an air stream having a relatively high velocity, and the inlet 14 is disposed so that the air entering the chamber flows around the cylindrical side wall 11 in the manner of a cyclone thereby creating a low pressure zone at the centre of the chamber. Communicating with this zone is a plurality of outlets 1 6 in the form of slits at regular spacings in the wall 1 3 of the chamber, and thus air at a relatively low pressure and hence having a velocity less than the velocity of the air entering the chamber issues from the outlets, the air carrying particles precipitated from the rapidly moving air flow around the chamber.The apparatus is positioned so that the low velocity air flow directs the particles towards the surface to be coated. Surplus air escapes from the chamber through the porous wall 12.
The particles rub against the walls of the chamber and the walls 11 and 1 3 are of a suitable plastics material such that the rubbing action charges the particles electrostatically by triboelectric charging. The particles therefore adhere to the surface to be coated, the article concerned being at earth potential.
Mounted inside the chamber is a radio frequency induction heating element 1 7 in the form of a flat coil or serpentine, the element being arranged so that the particles pass through the gaps in it as they flow to the outlets 1 6. The element is connected to a radio frequency wave generator and transmits radio frequency waves to the article thereby heating it simultaneously with the application of particles to the surface of the article. As a result, the particles which adhere to the surface, such adhesion also being assisted by heating of the surface, fuse and form a coating on the surface.
The walls of the chamber and the other parts of the apparatus adjacent to the induction heater are such that they are not heated by the heater.
If desired, the article may be pre-heated before being coated by the apparatus.
The size of the outlets 1 6 of the chamber is related to the velocity of the air flow through them.
Powder is supplied to the chamber from a fluidised bed 18, powder being drawn from the bed through a pipe 1 9 by air under pressure passing along a pipe 20 connected to the conduit 1 5.
The apparatus may be fixed or movable and the chamber may be shaped according to the contour of the surface to be coated.
Fig. 2 shows the chamber 10 of the apparatus incorporated in a heat mounted on an arm 21 which is carried by a pillar 22 and is movable by remotely controlled means to traverse the head over a surface of a motor car MC which is required to be painted, the apparatus being supplied with powder paint.

Claims (20)

1. A method of coating a surface of an article comprising directly particles of a thermosetting or/and thermoplastics powder towards the surface and simultaneously heating the surface so that particles adhere to the surface and fuse to form a coating thereon.
2. A method as claimed in Claim 1 wherein the surface is heated by subjecting it to radio frequency induction heating.
3. A method as claimed in Claim 1 or 2 wherein the particles are charged electrostatically.
4. A method as claimed in Claim 1, 2 or 3 wherein the particles are directed towards the surface by allowing them to fall on to the surface under gravity.
5. A method as claimed in Claim 1, 2 or 3 wherein the particles are entrained in a stream of air or gas at a relatively low velocity.
6. A method as claimed in Claim 3 or Claim 4 or 5 when dependant on Claim 3 wherein electrostatic charging of the particles is effected by causing them, in their passage towards the surface, to pass through a corona discharge.
7. A method as claimed in Claim 3 or Claim 4 or 5 when dependant on Claim 3 wherein electrostatic charging of the particles is effected by causing them to rub against a surface of a material such as to charge them by triboelectric charging.
8. An apparatus for coating a surface of an article, which comprises means for direct ing particles of a thermosetting or/and thermoplastics powder towards the surface and means for simultaneously heating the surface whereby particles adhere to the surface and fuse to form a coating thereon.
9. An apparatus as claimed in Claim 8 wherein the heating means comprises a radio frequency induction heater.
10. An apparatus as claimed in Claim 8 or 9 which is provided with means for charging the particles electrostatically.
11. An apparatus as claimed in Claim 8, 9 or 10 which comprises a chamber having an inlet for connection, in use, to a source of powder entrained in a stream of air or gas, and an outlet or outlets to be positioned, in use, to direct particles of the powder en trained in the air or gas issuing from the outlet(s) towards the surface to be coated.
1 2. An apparatus as claimed in Claim 11 wherein the chamber is formed to reduce the velocity of the air or gas flow as it passes through it.
1 3. An apparatus as claimed in Claim 1 2 wherein the chamber is of cylindrical form with the inlet arranged so that the incoming air or gas is caused to flow around the chamber in the manner of a cyclone thereby creating a low pressure zone in the centre, the outlet or outlets being disposed in this zone so that air or gas issues through the outlet(s) from said zone at a velocity lower than that of the incoming air or gas, the chamber being provided with one or more further outlets enabling surplus air or gas to escape from the chamber.
14. An apparatus as claimed in Claim 11, 1 2 or 1 3 wherein the radio frequency induction heater comprises an element, for example in the form of a flat coil or serpentine, for connection in use, to a radio frequency wave generator, this element being mounted inside the chamber.
1 5. An apparatus as claimed in Claim 11, 1 2 or 1 3 wherein the radio frequency induction heater comprises an element, for example in the form of a flat coil or serpentine, for connection in use, to a radio frequency wave generator, this element being disposed outside and adjacent to the chamber.
16. An apparatus as claimed in Claim 10 or any one of Claims 11 to 1 5 when dependant on Claim 10 wherein the means for charging the particles electrostatically comprise a generator arranged to produce a corona discharge in a zone through which the particles pass.
1 7. An apparatus as claimed in Claim 10 or any one of Claims 11 to 1 5 when dependant on Claim 10 wherein the means for charging the particles electrostatically effect such charging by triboelectric charging.
1 8. An apparatus as claimed in any one of Claims 11 to 1 5 wherein the chamber or a conduit conveying the particles to the chamber has at least a portion thereof arranged so that the particles rub against it and formed of a material such that the rubbing action charges the particles by triboelectric charging.
1 9. An apparatus as claimed in any one of Clams 11 to 1 5 wherein the chamber has a plurality of outlets in the form of slits or circular apertures.
20. An apparatus substantially as herein described with reference to and as illustrated in Fig. 1 or Fig. 2 of the accompanying drawings.
GB8008964A 1979-03-16 1980-03-17 Coating with parachute material Expired GB2047567B (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
GB8008964A GB2047567B (en) 1979-03-16 1980-03-17 Coating with parachute material

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB7909348 1979-03-16
GB8008964A GB2047567B (en) 1979-03-16 1980-03-17 Coating with parachute material

Publications (2)

Publication Number Publication Date
GB2047567A true GB2047567A (en) 1980-12-03
GB2047567B GB2047567B (en) 1983-12-14

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ID=26270921

Family Applications (1)

Application Number Title Priority Date Filing Date
GB8008964A Expired GB2047567B (en) 1979-03-16 1980-03-17 Coating with parachute material

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GB (1) GB2047567B (en)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2136315A (en) * 1983-02-04 1984-09-19 Standard Telephones Cables Ltd Insulating coatings
GB2237519A (en) * 1989-11-02 1991-05-08 Alcatel Nv Process for coating a metallic conductor with a layer of plastic
US5254185A (en) * 1989-12-15 1993-10-19 Calor-Emag Ag Method for producing a surface-coated component, in particular a contact piece for a vacuum switch, and device for executing this method
FR2822729A1 (en) * 2001-04-03 2002-10-04 Gesal Ind Non-stick coating of utensil surface, employs polymer powder coating with surface pre-heating, which is prolonged whilst powdered state persists

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2136315A (en) * 1983-02-04 1984-09-19 Standard Telephones Cables Ltd Insulating coatings
GB2237519A (en) * 1989-11-02 1991-05-08 Alcatel Nv Process for coating a metallic conductor with a layer of plastic
GB2237519B (en) * 1989-11-02 1993-08-11 Alcatel Nv Method of producing a high-frequency cable
US5254185A (en) * 1989-12-15 1993-10-19 Calor-Emag Ag Method for producing a surface-coated component, in particular a contact piece for a vacuum switch, and device for executing this method
FR2822729A1 (en) * 2001-04-03 2002-10-04 Gesal Ind Non-stick coating of utensil surface, employs polymer powder coating with surface pre-heating, which is prolonged whilst powdered state persists

Also Published As

Publication number Publication date
GB2047567B (en) 1983-12-14

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Legal Events

Date Code Title Description
PCNP Patent ceased through non-payment of renewal fee