GB1316286A - Device for spraying electrified powdered materials for the coating or surface treatment of various parts - Google Patents

Abstract

1316286 Spray producers SOC CARRIER SA 29 Oct 1970 [4 Nov 1969] 51579/70 Heading B2F In the electrostatic spraying of articles with a mixture of powder and air the articles are passed through a chamber 1 on a carrier, the chamber being at a lower pressure than its surroundings, the carrier passing through lockchambers 2 and in front of at least one spraying device 18, this being supplied with powder and air from a feeding tank 4 having a dosimeter-mixer 9 therein, supplied with compressed air from a pipe 16, and also having means 7 to ensure the recycling of powder not deposited on the sprayed articles, the spraying device having a dividing element 21 (Fig. 2) in the slot from which the material is sprayed. As shown the spraying device 18 comprises a vertical tube which is supplied with the powder-air mixture through a homogenizing tube 17, the dividing member 21 consisting here of a plate with grooves or notches 22, 23 on alternate sides thereof, these defining individual spray orifices, the electrostatic charging being by a wire 26 (Fig. 1) connected to a voltage supply 29, although this may optionally be directly connected to dividing element 21 if this is of metal and the tube in which it is mounted is of insulating material. A flap 18 1 at the top of the tube controls the pressure therein to prevent the spraying being at too great a pressure. The pressure in the chamber 1 is reduced through pipe 30. The dosimetermixer 9 has at the end 12 of a tube 10, a shutter flap 13, this being moveable (through member 14 and control 15) to vary the degree of suction caused by the air supplied through pipe 16 and so to vary the amount of spray material supplied to the spraying device. Alternative dividing members may be incorporated in the spray device 18, these consisting of a member with teeth defining the orifices, these varying in size along the length of the device 18 to ensure uniform spraying along the length of the device (Fig. 4, not shown) and a strip or wire which is corrugated to define the orifices, the corrugations similarly of varying sizes (Fig. 5, not shown). As an alternative to the supply and recirculation device shown for the powder-air mixture, a fluidized bed may be used (Fig. 6, not shown), a vibrator connected to a filter connected to the bottom of the chamber by a pipe controlling the supply of powder to the bed, this being on a mesh screen over a chamber supplied with air for the fluidization of the bed, the material being drawn from the bed through an ejector. An embodiment with two spraying devices positioned to spray both sides of the articles is also described.