Coating processes – Direct application of electrical – magnetic – wave – or... – Electrostatic charge – field – or force utilized
Reexamination Certificate
1999-08-17
2001-06-12
Parker, Fred J. (Department: 1762)
Coating processes
Direct application of electrical, magnetic, wave, or...
Electrostatic charge, field, or force utilized
C427S475000, C427S478000, C427S485000, C118S634000, C118SDIG005
Reexamination Certificate
active
06245391
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a powder coating apparatus and a powder coating method, and more particularly, to an apparatus and a method therefor in which a powder coating is performed using an electrostatic fluidized dipping method.
BACKGROUND ART
From the viewpoint of environmental preservation, attention is paid to ecofriendly, pollution-free type powder coating that uses no solvents. One of such powder coating methods is an electrostatic fluidized dipping method. In the electrostatic fluidized dipping method, a tank for storing a powder coating material is formed at a lower portion of a substantially closed booth, and air is blown into the storage tank to thereby cause the charged powder coating material to fly up within the booth. Then, in such an atmosphere, an electrically grounded object to be coated is introduced above the storage tank, and the powder coating material is caused to adhere onto the surface of the object to be coated by an electrostatic force.
According to this method, coating is carried out within the booth, and thus powder coating can be performed on the surface of the object to be coated while preventing the splashing and adhesion of the powder coating material onto peripheral equipment, etc., arranged outside the booth.
However, since fluctuation of particle diameter occurs in the powder coating material, finer particles are easily blown up while particles having larger sizes are hardly blown up. Since the particles of the coating material are thus classified, those particles having such a large size so as not to be blown up from the storage tank located in the lower portion of the booth to the object to be coated do not contribute to the formation of a film on the surface of the object to be coated. Therefore, there is a problem inherent in the conventional method that the use efficiency of the coating material was lowered.
DISCLOSURE OF THE INVENTION
The present invention has been made to overcome the aforementioned problem and therefore has as an object to provide a powder coating apparatus and a method therefor with which the use efficiency of a powder coating material can be improved.
A powder coating apparatus according to the present invention comprises: a booth; a fluidized bed of a powder coating material formed on the bottom of the booth and having an opening on the top thereof; coating material blowing structure for introducing the powder coating material from the fluidized bed and blowing the introduced powder coating material into the booth from an upper portion of the booth; holding structure for holding an object to be coated within the booth; electrodes provided within the booth so as to confront the object to be coated held by the holding structure; a power supply for applying a high voltage between the electrodes and the object to be coated; and circulating stream forming structure for forming a circulating stream of the powder coating material within the booth.
The fluidized bed may be detachably attached to the booth. Further, the circulating stream forming structure may have ejectors for blowing air upward from a lower portion of the booth. Still further, a rectifying unit for rectifying a stream of the powder coating material may be arranged immediately above the fluidized bed.
The powder coating apparatus may also have such a structure that the booth has openings at both ends in the longitudinal direction thereof, and the holding structure holds the object to be coated while moving the object to be coated in the longitudinal direction of the booth so that the object to be coated is allowed to pass through the booth via the openings at both ends, and the holding structure electrically grounds the object to be coated. In this case, the powder coating apparatus may further comprise sucking structure for sucking air from the openings at both ends in the longitudinal direction of the booth, and a bag filter for capturing the powder coating material contained in the air sucked by the sucking structure.
A powder coating method according to the present invention comprises the steps of: fluidizing a powder coating material on the bottom of a booth; introducing the fluidized powder coating material to blow the introduced powder coating material into the booth from an upper portion of the booth; introducing an object to be coated into the booth; forming an electric field for inducing the powder coating material around the object to be coated; and forming a circulating stream of the powder coating material within the booth.
The powder coating method may further comprise the step of passing the object to be coated through the booth by moving the object to be coated in the longitudinal direction of the booth. In this case, air may be sucked from an entrance and an exit for the object to be coated which are provided at both ends in the longitudinal direction of the booth to thereby entrap the powder coating material contained in the sucked air.
REFERENCES:
patent: 3828729 (1974-08-01), Goodridge
patent: 3905785 (1975-09-01), Fabre
patent: 4207833 (1980-06-01), Napadow
patent: 4301764 (1981-11-01), Campion et al.
patent: 4354451 (1982-10-01), Vohringer et al.
patent: 5056460 (1991-10-01), Vohringer
patent: 63-274465 (1988-11-01), None
patent: 5-308709 (1993-11-01), None
Kawai Hiroki
Yamamoto Masahiro
Nihon Parkerizing Co. Ltd.
Parker Fred J.
Wenderoth , Lind & Ponack, L.L.P.
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