Control grid in electrostatic fluidized bed coater
AssigneeElectrostatic Equipment Corporation
InventorDonald J. Gillette
Life of this patent
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Abstract
Apparatus is provided for the fluidized bed electrostatic coating of workpieces, especially those of continuous length, such as metal wires. The apparatus includes a control grid (normally grounded), which spans the coating chamber and establishes an electrical effect which densifies and regulates the cloud of charged particles therewithin. Objects (also normally grounded) passed through the cloud so produced may therefore readily develop a uniform deposit upon all exposed surfaces.
Claims19
Electrostatic fluidized bed coating apparatus comprising, in combination:
- a housing having a generally planar substantially horizontal porous support member mounted therein to define within said housing a fluidization chamber thereabove and a plenum therebelow;
- means for introducing gas into said plenum for passage upwardly through said support member to effect fluidization of particulate coating material supplied to said chamber;
- means to effect electrostatic charging of such particulate material;
- and an electrically conductive, generally planar mesh-like control grid disposed within and substantially spanning the cross-sectional area of said chamber above said support member, said grid being substantially free of horizontal flat surfaces and being adapted for control of its electrical potential, and said housing being adapted for the passage of a workpiece therethrough at a location between and spaced from each of said support member and said grid, whereby the cooperative effects of fluidization and electrostatic charging may produce a cloud of electrostatically charged particulate material above said support member, and whereby said control grid may be used to densify and regulate such cloud, for improved coating.
A system for electrostatically coating a continuous length workpiece, comprising:
- (a) electrostatic fluidized bed coating apparatus comprising, in combination, a housing having a generally planar, substantially horizontal porous support member mounted therein to define within said housing a fluidization chamber thereabove and a plenum therebelow;
- means for introducing gas into said plenum for passage upwardly through said support member to effect fluidization of particulate coating material supplied to said chamber;
- means to effect electrostatic charging of such particulate material;
- and an electrically conductive, generally planar, mesh-like control grid disposed within and substantially spanning the cross-sectional area of said chamber above said support member, said grid being substantially free of horizontal flat surfaces and being adapted for control of its electrical potential, and said housing being adapted for the substantially horizontal movement therethrough of at least one workpiece of continuous length at a location between and spaced from each of said support member and said grid, whereby the cooperative effects of fluidization and electrostatic charging may produce a cloud of electrostatically charged particulate material above said support member, and whereby said control grid may be used to densify and regulate such cloud, for improved coating;
- and
- (b) means for continuously conveying said workpiece through said housing of said apparatus at said location between said support member and said grid.
A method for depositing of particulate material upon a workpiece comprising the steps of:
- forming within a fluidized bed of particles an electrostatically charged cloud thereof;
- increasing the density and uniformity of said cloud with an electrically conducting grid at a potential different from that of said charged particles;
- and passing through said cloud, at a level below and out of contact with said grid, a workpiece maintained substantially at the potential of said grid, whereby said article may acquire upon all of its exposed surfaces a substantially uniform deposit of said particles.
Dependencies are inferred from the claim text.