Abstract Methods and apparatus for applying coating materials to articles, using electrogasdynamic apparatus providing a flow channel having a dielectric boundary which has a length-/width ratio of greater than 2.5. Gas containing particulate coating material is ionized to create an electrical discharge field for imparting an electrical charge to the particles prior to passage through the dielectrically bounded flow path and thereby creating a high space charge potential. In special applications, a freeradical forming monomer gas or a fusible particle substance is carried in an inert gas into the electrical discharge field and through the flow channel toward the article to be coated. In any case, the charged particles are subjected to an axial charge repelling field (due to space charge effects) in the flow channel to raise the electrical potential of the particles, and thereby the potential gradient between the particles and the workpiece.
In an electrogasdynamic system for applying a coating to an article, the combination of: means for forming a suspension of coating particles in a gaseous stream; electrode means for subjecting the coating particles to an electrical discharge to impart an electrical charge to the particles; and flow channel means defining for the charged particles a flow path having a substantially non-conducting boundary which has an axial length between the electrode means and an outlet that is greater than the maximum width thereof, at an axial location of greatest charge concentration, by a factor of at least 2.5.
Claim 2
Dependent Claim
97 words
In an electrogasdynamic system for applying a coating to an article, the combination of: means for forming a suspension of coating particles in a gaseous stream; electrode means for subjecting the coating particles to an electrical discharge to impart an electrical charge to the particles; and flow channel means defining for the charged particles a flow path having a substantially non-conducting boundary which has an axial length between the electrode means and an outlet that is greater than the maximum width thereof, at an axial location of greatest charge concentration, by a factor of at least 2.5.
Claim 3
Dependent Claim
33 words
Apparatus according to claim 1, further comprising: source means of at least one monomer gas; and means for introducing the monomer gas into the gaseous stream to be subjected to the electrical discharge.
Claim 4
Dependent Claim
35 words
Apparatus according to claim 1, further comprising: means for applying heat to the suspended particles prior to deposition thereof on the article and suFficient to condition the particles for fusion upon contact with the article.
Claim 5
Dependent Claim
100 words
Apparatus according to claim 1, further comprising: gas supply means for moving the gaseous stream and the charged particles through the flow channel means, and; the flow channel means opening into a zone less restricted in cross section than the flow channel means to establish a space charge field by the emission of charged particles therein, and; the means for moving the gaseous stream and the charged particles being operative to force the particles against an axial charge repelling field resultant from the space charge field and into the space charge field to significantly increase the potential on the particles.