GB1301559A - - Google Patents

Abstract

1301559 Purging paint-spraying equipment CARRIER ENG CO Ltd 14 June 1971 [29 July 1970] 36783/70 Headings F2N and F2V [Also in Division F1] In paint-spraying equipment wherein spray guns 32, 33, Fig. 1, may be selectively connected via line 31 and rotatable arm 25 to any one of paint supply ports 4, 5, 6, ... 21 or to a solvent supply port 22, from which solvent for purging the equipment is deliverable to the guns between disconnection of arm 25 from one paint supply port and connection of the arm to another-port, supplying paint of a different colour, the solvent delivery line 57, 59 to port 22 includes a piston 51/cylinder 50 combination, Figs. 1 and 2 arranged to control the pressure of the solvent, such that when arm 25 is connected to port 22 residual paint, left in arm 25 and line 31 after disconnection from one paint supply port, is discharged from the guns by the following pressurized solvent at the same rate as it was discharged before disconnection from the paint supply port. In use, with valve 59a closed, valve 60 is opened to fill solvent chamber 55, urging the piston 51 up against adjustable stop 53, valve 60 then being re-closed. A valve 61 is then opened to admit compressed air through passages 67, 68 to the space 54 above the piston. The pressure of this compressed air is equal to the pressure of the paint supply. Valve 61 is then re-closed. Arm 25 is then moved from the paint supply port to port 22 and valve 59a is opened so that the air pressure in space 54 pressurizes the solvent which passes to the spray guns. As the proportion of relatively high viscosity residual paint to relatively low viscosity solvent in the discharge line decreases, so does the combined resistance to flow of the two fluids. The position of stop 53 is adjusted in accordance with the dimensions of the paint circuit, from the ports to the discharge nozzles of the guns; this and the decreasing pressure in space 54 maintains the desired constant rate of discharge. Selector valve.-1, Fig. 1, includes a flat annulus, indicated by broken lines 29, rotatable with the arm 25 and arranged to cooperate with sealing faces of all the ports 4-23 save that port with which the end of arm 25 co-operates. The arm is mounted on a pinion 26 associated with a rack 27.