Electrostatic coating apparatus

Claim 2

ELECTROSTATIC FLUIDIZED BED COATING APPARATUS COMPRISING, IN COMBINATION, A HOUSING HAVING A GENERALLY PLANAR POROUS SUPPORT MEMBER MOUNTED THEREIN TO DEFINE WITHIN SAID HOUSING A FLUIDIZATION CHAMBER THEREABOVE AND A PLENUM THEREBELOW, AND HIGH EFFICIENCY GAS IONIZING MEANS SO DISPOSED AS TO FURNISH TO SAID PLENUM HIGHLY IONIZED GAS, SAID IONIZING MEANS BEING SPACED FROM SAID SUPPORT MEMBER BY A MIMINUM DISTANCE OF ABOUT 7.5 CENTIMETERS, AS MEASURED ALONG THE MOST DIRECT GAS FLOW PATH DEFINED THEREBETWEEN, SO THAT IONIZED GAS FROM SAID IONIZING MEANS PASSES FROM SAID PLENUM THROUGH SAID SUPPORT MEMBER AND INTO SAID FLUIDIZATION CHAMBER TO FLUIDIZE AND EFFICIENTLY ELECTROSTATICALLY CHARGE PARTICULATE MATERIAL SUPPLIED THERETO, WITH SAID MINIMUM SPACING EFFECTIVELY ISOLATING SAID IONIZING MEANS TO AVOID, UNDER NORMAL OPERATING CONDITIONS, THE PASSAGE OF A SUBSTANTIAL CURRENT THEREFROM TO AN EFFECTIVELY OPPOSITELY CHARGED MEMBER DISPOSED IN SAID FLUIDIZATION CHAMBER.

Claim 3

The apparatus of claim 1 wherein said gas ionizing means comprises a porous metal electrode having a maximum resistance value of about 0.05 ohm per centimeter.

Claim 4

The apparatus of claim 2 wherein said electrode comprises a porous mat of sharp-edged fibers.

Claim 5

The apparatus of claim 3 wherein said fibers are randomly disposed in said mat.

Claim 6

The apparatus of claim 4 wherein said electrode is provided by metal wool.

Claim 7

The apparatus of claim 3 wherein said fibers are woven in said mat.

Claim 8

The apparatus of claim 6 wherein said fibers are of a flattened wire having a width of about 0.05 centimeter or less.

Claim 9

The apparatus of claim 3 wherein said metal of said electrode is selected from the group consisting of iron, brass, aluminum, and alloys based upon one thereof, and wherein said electrode has a maximum resistance value of about 0.005 ohm per centimeter.

Claim 10

The apparatus of claim 1 wherein said ionizing means is so disposed as to cause substantially the entire volume of ionized gas therefrom to pass through said support member, and wherein said minimum distance of spacing is about 25 centimeters.

Claim 11

The apparatus of claim 9 wherein said ionizing means is mounted within said plenum.

Claim 12

The apparatus of claim 10 wherein said plenum comprises an inner compartment adjacent said support member and an outer compartment which is separated from said inner compartment by said ionizing means and which communicates with said inner compartment therethrough, said housing having a gas inlet opening which communicates with said outer compartment and which has a cross sectional area that is substantially smaller than the area over which said outer compartment communicates with said ionizing means, said outer compartment thereby effecting a decrease in velocity of gas introDuced through said inlet opening and a better distribution thereof to said ionizing means.

Claim 13

The apparatus of claim 11 wherein said ionizing means and said plenum compartments are cooperatively dimensioned, configured and disposed so as to maximize exposure to the charging elements of said ionizing means of gas passed therethrough from said outer compartment to said inner compartment.

Claim 14

The apparatus of claim 1 wherein at least the major portion of the gas flow path between said ionizing means and said support member is free from severe deionization structure.

Claim 15

The apparatus of claim 13 wherein said gas flow path major portion is free from structure having the deionization equivalent of a cylindrical tubular member with a length to diameter ratio greater than 1.5:1.0.

Claim 16

Electrostatic coating apparatus comprising, in combination, a housing having a porous support member mounted therein and defining a fluidization chamber thereabove and a plenum therebelow; and a porous electrode comprised of sharp-edged metal fibers and having a maximum resistance value of about 0.05 ohm per centimeter, said electrode being mounted in a gas flow conduit defined at least in part by said plenum, so as to ensure that the major portion of gas flowing through said conduit passes through said electrode, and being spaced from said support member by a minimum distance of about 7.5 centimeters, as measured along the most direct gas flow path defined therebetween, said electrode also being adapted to receive a high applied voltage for the efficient ionization of gas passed therethrough, so that gas introduced into said conduit may be highly ionized by passage through said electrode, and thereafter employed to fluidize and efficiently electrostatically charge particulate material supplied to said fluidization chamber, said minimum spacing effectively isolating said electrode to avoid, under normal operating conditions, the passage of a substantial current therefrom to an effectively oppositely charged member disposed in said fluidization chamber.

Claim 17

Electrostatic coating apparatus comprising, in combination, a housing having a porous support member mounted therein and defining a fluidization chamber thereabove and a plenum therebelow; and a porous electrode comprised of sharp-edged metal fibers and having a maximum resistance value of about 0.05 ohm per centimeter, said electrode being mounted in a gas flow conduit defined at least in part by said plenum, so as to ensure that the major portion of gas flowing through said conduit passes through said electrode, and being spaced from said support member by a minimum distance of about 7.5 centimeters, as measured along the most direct gas flow path defined therebetween, said electrode also being adapted to receive a high applied voltage for the efficient ionization of gas passed therethrough, so that gas introduced into said conduit may be highly ionized by passage through said electrode, and thereafter employed to fluidize and efficiently electrostatically charge particulate material supplied to said fluidization chamber, said minimum spacing effectively isolating said electrode to avoid, under normal operating conditions, the passage of a substantial current therefrom to an effectively oppositely charged member disposed in said fluidization chamber.

Claim 18

The apparatus of claim 15 wherein said metal of said electrode is selected from the group consisting of iron, brass, aluminum, and alloys based upon one thereof, and wherein said electrode has a maximum resistance value of about 0.005 ohm per centimeter.

Claim 19

The apparatus of claim 15 wherein the lower extremity of said plenum is defined by a floor extending thereacross, and wherein said electrode of metal fibers extends across said plenum as a layer supported upon said floor.

Claim 20

The apparatus of claim 17 wherein said plenum is further defined by a sidewall extending upwardly from adjacent said floor, at least one of said floor and said sidewall defining openings for gas flow into said plenum, said openings being disposed relative to said electrode of metal fibers so as to ensure passage therethrough of at least the major portion of gas entering said plenum.

Claim 21

The apparatus of claim 18 wherein said housing has a sidewall and a bottom wall spaced, respectively, from said sidewall and said floor of said plenum to enclose said plenum therewithin and to cooperatively define an outer plenum thereabout.

Claim 22

The apparatus of claim 19 wherein said electrode comprises a mat of said fibers, the disposition of said metal fiber mat and the area for gas flow provided by said openings ensuring that gas which enters said first mentioned plenum from said outer plenum passes through substantially the entire volume of said mat, thereby obtaining maximum utilization thereof for gas ionization.

Claim 23

The apparatus of claim 15 wherein said conduit includes a section of reduced cross sectional dimensions opening into said plenum, and wherein said electrode comprises a mat of metal fibers disposed within said conduit section.

Claim 24

The apparatus of claim 21 wherein said conduit section is a gas pipe connected to said housing.

Claim 25

The apparatus of claim 15 wherein said housing has apertures therein adapted to permit objects Of extended length to be drawn through said fluidization chamber.

Claim 26

The apparatus of claim 23 wherein said porous support member also has an aperture therein that is adapted to permit such extended length objects to be drawn therethrough and vertically of said housing.

Claim 27

The apparatus of claim 24 wherein said apparatus additionally includes a hollow insulating member disposed vertically in said plenum and adapted for the passage therethrough of such extended length objects, said insulating member preventing electrical discharge to the object from said electrode.

Claim 28

Electrostatic coating apparatus comprising, in combination, a housing having a porous support member mounted therein to define within said housing a fluidization chamber thereabove and a plenum therebelow; high efficiency gas ionizing means spaced from said support member and so disposed as to furnish to said plenum highly ionized gas; and baffle means fabricated from an insulating material and interposed in the gas flow path between said ionizing means and said support member so as to shield said ionizing means and increase the effective length of said gas flow path, so that ionized gas from said ionizing means passes from said plenum through said support member and into said fluidization chamber to fluidize and efficiently electrostatically charge particulate material supplied thereto, with said baffle means cooperating to effectively isolate said ionizing means to avoid the passage of a substantial current therefrom to an effectively oppositely charged member disposed in said fluidization chamber.

Claim 29

Electrostatic coating apparatus comprising, in combination, a housing having a porous support member mounted therein to define within said housing a fluidization chamber thereabove and a plenum therebelow; high efficiency gas ionizing means spaced from said support member and so disposed as to furnish to said plenum highly ionized gas; and baffle means fabricated from an insulating material and interposed in the gas flow path between said ionizing means and said support member so as to shield said ionizing means and increase the effective length of said gas flow path, so that ionized gas from said ionizing means passes from said plenum through said support member and into said fluidization chamber to fluidize and efficiently electrostatically charge particulate material supplied thereto, with said baffle means cooperating to effectively isolate said ionizing means to avoid the passage of a substantial current therefrom to an effectively oppositely charged member disposed in said fluidization chamber.

Claim 30

The apparatus of claim 26 wherein said ionizing means includes a metal electrode having a maximum resistance value of about 0.005 ohm per centimeter, and having elements extending across a lower portion of said plenum, said baffle means comprising a planar member extending across said plenum above said electrode and having a larger area than that of the upper effective surface of said electrode, to thereby mask said electrode from said support member and provide said shielding and pathlengthening effects.

Claim 31

The apparatus of claim 1 wherein said housing has apertures therein adapted to permit objects of extended length to be drawn through said fluidization chamber.

Claim 32

The apparatus of claim 28 wherein said porous support member also has an aperture therein that is adapted to permit such extended length objects to be drawn therethrough and vertically of said housing.

Claim 33

The apparatus of claim 29 wherein said apparatus additionally includes a hollow insulating member disposed vertically in said plenum and adapted for the passage therethrough of such extended length objects, said insulating member preventing electrical discharge to the object from said electrode.

Claim 34

Electrostatic fluidized bed coating apparatus comprising, in combination, a housing, a generally planar pourous support member having upwardly extending peripheral sidewalls to define therewith a tray, said member being snugly but removably mounted within upstanding walls of said housing whereby to define within said housing a fluidization chamber thereabove and a plenum therebelow; and high efficiency gas ionizing means spaced from said support member and so disposed as to furnish to said plenum highly ionized gas, so that ionized gas from said ionizing means passes from said plenum through said support member and into said fluidization chamber to fluidize and effectively electrostatically charge particulate material supplied thereto, with said spacing of said ionizing means from said support member effectively isolating said ionizing means to avoid the passage of a substantial current therefrom to an effectively oppositely charged member disposed in said fluidization chamber.

Claim 35

Electrostatic fluidized bed coating apparatus comprising, in combination, a housing, a generally planar pourous support member having upwardly extending peripheral sidewalls to define therewith a tray, said member being snugly but removably mounted within upstanding walls of said housing whereby to define within said housing a fluidization chamber thereabove and a plenum therebelow; and high efficiency gas ionizing means spaced from said support member and so disposed as to furnish to said plenum highly ionized gas, so that ionized gas from said ionizing means passes from said plenum through said support member and into said fluidization chamber to fluidize and effectively electrostatically charge particulate material supplied thereto, with said spacing of said ionizing means from said support member effectively isolating said ionizing means to avoid the passage of a substantial current therefrom to an effectively oppositely charged member disposed in said fluidization chamber.