Patent GB-892699-A (GB)
Title: Improvements in preparing surfaces for receiving coats of paint or the like
Inventor: ASHWORTH NORMAN IVES
IPC: B24C9/00
Filed: 1959-05-27
Abstract: 892,699. Abrasive blasting. ABRASIVE DEVELOPMENTS Ltd. May 5, 1960 [May 27,1959; Dec. 5, 1959], Nos. 17996/59 and 41387/59. Class 60. A process for "flatting down" the surface of a car body or other workpiece after the application of a filler or primer coat preparatory to receiving a finishing coat of paint or the like fluid comprises subjecting the surface of the coat to the grinding action of a mixture of abrasive particles and water projected on to the surface of the coat to produce a fine and even matt surface on such coat, the quantity of water in the mixture being such that on striking the surface the water causes the abrasive particles to move in a lateral direction over the surface of the coat to give the even and fine matt surface without breaking down such coat. Motor car bodies 1 are mounted on a conveyer 2 which moves a car body into an air lock compartment which prevents excessive escape of blasting mixture to atmosphere and then into a compartment 3 in which it is treated with the abrasive mixture whilst the conveyer is moving; the car body then proceeds through a compartment 4 for washing the treated surface by water sprays. A mixture of abrasive particles and water in a sump 5 is fed by pumps 6 through conduits 6a to spray guns 7 and/or impellers 8 in the treating compartment 3, the mixture passing from the car body draining back to the sump 5. In the washing compartment 4 water is sprayed on the body by a mixture of air under pressure and water through spray guns 9 to produce an atomised spray to give effective quick washing with a minimum of water; the used water drains to the sump 5. The contents of the sump are agitated, by branch circulation from the pumps or by paddles, so that broken down abrasive particles and pigment particles float to the upper portion of the liquid in the sump 5 and are discharged through an overflow outlet 11, in the side of the sump, which is guarded to prevent undue turbulence so as to allow heavier abrasive particles of the required weight for use to sink in the sump. A perforated screen 11a is provided. The overflow mixture passes by pipe 12 to a centrifugal classifier 13 in which the re-usable heavier abrasive particles are separated and pass through outlet 14 to a conveyer 15 which returns them to the sump 5. The water, broken down abrasive particles and pigment particles pass from outlet 16 through pipe 16a to a centrifugal classifier 17 in which the broken down abrasive particles are separated and pass through outlet 17a to waste. The water and pigment particles pass through outlet 17b and pipe 17c to a filter 18 in which the pigment particles are removed; the clean water is fed by a pump 19 through pipe 19a to a storage tank 20 from which it is pumped through conduits 9a to the washing sprayers 9, overflow from the tank 20 passing to the sump 5. If the water contains harmful salts, a salt extracting unit may be provided through which all water for the wash nozzles passes. A branch pipe 21 from the pipe 19a delivers water through control valve 19b to assist the discharge overflow from the sump 5 through the classifier 13 and also through a branch pipe 22 and control valve 22a to the classifier 17. Abrasive discharged to waste by the classifier 17 is replaced by fresh abrasive delivered from a hopper 15b on to the conveyer 15. Wasted water is replaced by supplying fresh water to the tank 20. After washing, the car body passes into a drying section; high velocity warm air is discharged over the body to remove any residual microparticles prior to spraying, or alternatively a high powered suction device is used to remove the residual dry abrasive from the body.