Electrostatic powder-depositing installation

In an electrostatic powder-depositing installation for depositing powder on the interior of hollow parts of large dimensions, said installation comprising:

• a powder-depositing cage, a powder-depositing unit placed within said cage using air for depositing powder on said hollow parts, a vacuum pressure filtering system for removing non-deposited powder from the air used in the coating operation, a system for supplying powder to said powder-depositing unit, and a non-deposited powder recovery tank for recovery of powder, the improvement wherein said powder-depositing cage comprises vertical exterior walls and a horizontal top wall, vertical interior walls extending downwardly from said top wall towards the bottom of the cage but terminating short of said cage bottom and being spaced from said vertical exterior walls to define a relatively large opening within the top wall of said cage through which non-deposited powder tends to escape, and forming a powder-depositing chamber such that downwardly open hollow parts may be vertically dropped to fit over the powder-depositing unit positioned within said chamber by passage of the hollow parts through the opening within the top wall of the powder-depositing cage, and wherein said top wall and said interior and exterior walls define a peripheral chamber for collecting of air bearing non-deposited powder, said peripheral chamber leading to said filtering system such that air loaded with said non-deposited powder is vacuum drawn into the peripheral chamber and thereby prevented from escaping through the cage top wall opening and is subsequently filtered in said filtering system to collect the non-deposited powder, said non-deposited powder being recovered by said recovery tank connected to said filtering system, and recycled to the powder-depositing unit connected to said recovery tank for further employment in the projection of powder onto said parts.