(57) Electrostatic or electrogasdynamic coating apparatus includes a coating gun, e.g.
for use with dry powder, whose structure defines a through passage leading from an
inlet tube (10) operatively connected to a source of particulate coating material
to a discharge barrel (12). A central needle cathode electrode (15) is mounted in
a constricted region of the passage, its tip being adjacent an annular porous metal
anode electrode (25) whose central opening defines part of the passage. A flow of
the material is induced along the passage by a first pressurized gas (e.g. air) stream
fed from a first supply formation (24) to enter the passage in the region of the electrodes,
in which region the particles receive an electric charge from the latter. At the same
time a second pressurized gas steam, which is controlled independently of the first
stream, is fed from a second supply formation (24) through the porous electrode itself
to prevent build-up of particles on the acting portion thereof.
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