Patent ID: 7178459

Claim:
An apparatus for distributing powders on a support in a predetermined pattern, comprising: a belt conveyor ( 2 ) for transporting the support ( 3 ); a head for applying the powders ( 1 ), located above the conveyor ( 2 ), which head ( 1 ) comprises a ring-wound closed continuous belt ( 4 ) exhibiting a plurality of perforations arranged according to a predetermined pattern, which perforations are of a size which enables passage of predetermined quantities of powders; means for controlling a supply and delivery of powders through the perforations and for keeping the continuous belt ( 4 ) clean; means for controlling a movement of the continuous belt ( 4 ) in synchrony with a movement of the conveyor ( 2 ), characterised in that said means for controlling a supply and delivery of powders through the perforations and for keeping the continuous belt ( 4 ) clean comprise: a hopper ( 5 ) located at a short distance above the continuous belt ( 4 ); the hopper ( 5 ) exhibiting an outlet mouth which is transversally arranged with respect to the advancement direction of the continuous belt ( 4 ) and the conveyor ( 2 ), and which is delimited, perpendicular to the advancement direction of the continuous belt ( 4 ) and the conveyor ( 2 ), by a front edge ( 50 ) and a back edge ( 51 ); a fixed upper doctor ( 6 ) which operates at the front edge ( 50 ) and which is pressed against an upper face of the continuous belt ( 4 ) by a elastic element ( 9 ); a fixed lower doctor ( 8 ) which is pressed against a lower face of the continuous belt ( 4 ) and exerts thereon an antagonistic action to an action exerted by the fixed upper doctor ( 6 ); an adjustable doctor ( 7 ) which operates at the back edge ( 51 ) and is pressed against the upper face of the continuous belt ( 4 ) and is arranged opposite to and antagonistically to the fixed upper doctor ( 6 ); the adjustable doctor ( 7 ) being adjustable by sliding in a perpendicular direction to the back edge ( 51 ) and the front edge ( 50 ) in order to regulate an aperture of the outlet mouth of the hopper ( 5 ).