GB1220265A - Recirculating system for flowable spray media - Google Patents

Abstract

1,220,265. Forcing liquids by gaseous pressure. GYROMAT CORP. April 10, 1968 [April 28, 1967], No.17402/68. Heading F1R. [Also in Division B2] A circulating system for supplying a medium to a spray gun comprises two tanks, each of which can be pressurized so as to act as the supply tank while the other tank acts as a recovery tank to receive overspray returned from the spray chamber containing the spray gun, and control means for interchanging the functions of the two tanks. A conveyor belt 12 travels beneath a spray gun 10, overspray being collected in a trough 16 and then passing through a separator 17 in which the spray medium (which may be an emulsion or solution of polytetrafluoroethylene) is separated from the entraining air and discharged to a return line 41. Compressed air is supplied from a line 43 to pressurize either a tank A or a tank B via a respective solenoid valve 37 or 57, whereby spray medium is forced from the pressurized tank via a respective check valve 31 or 51 to the spray gun 10. The spray medium recovered from the overspray passes from the return line to the unpressurized tank B or A via a respective solenoid valve 53 or 33 and check valve 55 or 35. When the liquid level in the pressurized tank has fallen below the level of a respective electrical probe PA or PB, the solenoid valve 53 or 33 is closed to stop the return flow to the unpressurized tank, and the solenoid valve 57 or 37 is opened to the compressed air line 43 to start the pressurization of this tank. Until this pressurization is complete, the other tank remains pressurized to avoid interruption of supply to the spray gun. On completion of the pressurization, as sensed by a pressure switch PSB or PSA, the solenoid valve 37 or 57 of the initially pressurized tank is closed to the compressed air line 43 and opened to atmosphere and its other solenoid valve 33 or 53 is opened, thereby completing the reversal of the functions of the two tanks. The reversal sequence is repeated whenever the level in the pressurized tank falls below the level of its probe PB or PA. Whenever both probes PA and PB are simultaneously uncovered by liquid, replenishment of the liquid is necessary. To this end, the simultaneous uncovering of both probes PA and PB causes opening of a solenoid valve 63 whereby tank A is replenished from a pressurized tank C until the level reaches a probe PC, whereupon the valve 63 is closed. An electrical circuit for the automatic control of the solenoid valves by the liquid level probes and pressure switches through the intermediary of relays is described.