GB1120058A - A control system for a spray apparatus - Google Patents

Abstract

1,120,058. Coating apparatus; spray-producers. DEVILBLISS CO. 21 April, 1966 [8 July, 1965], No. 17557/66. Headings B2F and B2L. A control system for a spray apparatus in which fluid is fed to and discharged from a spray gun 10 having a supply passage 17, comprises a fluid pressure regulator valve 18 interposed in said supply passage, the discharge pressure of said regulator valve being responsive to a control pressure, means to maintain a relatively low control pressure on said regulator valve and thus a relatively low fluid pressure in said supply passage during normal spraying, and override means to compose a relatively high control pressure on said regulator valve and thus a relatively high pressure in said fluid supply passage during other operation of said spray gun, whereby material in said fluid supply passage may be rapidly replaced. In the arrangement shown spray gun 10 includes a pneumatic cylinder 11 having a piston 12 directly connected to a needle 13 which operates in a fluid discharge passage 14. Atomizing air enters the gun from passage 15 and discharges from an annular orifice 15a. The atomizing air is controlled by air valve 16 carried by needle 13 and thus moved off its seat by piston 12 when the gun is turned on. Fluid is supplied through conduit 17 and is held at a regulated pressure by valve 18 and during normal spraying this pressure is maintained at a relative low pressure e.g. 5 to 7 p.s.i. by control air pressure from control regulator valve 19. Regulator 19 is manually adjustable so that the operator can vary the normal fluid pressure at will. The gun may be of electrostatic or non-electrostatic type. Fluid may be supplied from several sources, A, B, C by any suitable means but as shown the containers A, B, C are under pressure from a pneumatic supply source 30 through branch line 29 and the discharge from each goes respectively to a pneumatically controlled valve 32A, 32B, 32C and thence via a common manifold 33 to the fluid pressure regulator 18. Operation of the spray gun may be controlled through photo-electric control means 46 in response to articles 45 being conveyed past the gun but such control means can be by-passed by manual or automatic means. The colour change system includes air operated switch 28 solenoid operated air valve 26, air operated voltage control valve 25 and an air operated override air valve 56 and provides means for overcoming the normal adjustment of regulator valves 18 and 19 whereby fluid such as a solvent fluid from container C may be pushed through control valve 32C, manifold 33 and regulator 18 to the gun 10 at an increased pressure and velocity, thus reducing the time necessary for purging these lines of the terminated fluid A prior to initiation of spraying a second fluid B. This override means can also be used to momentarily increase the pressure of the fluid during spraying to clear any block ages in the system. A time delay device may be incorporated to delay the inactivation of the override system for a short time after the initiation of a new colour cycle in order to permit the system to be filled at high pressure and to clear the system of purging fluid, Indicator means may also be provided to alert the operator to the passage of a minimum time during which flow of solvent should persist to ensure adequate cleansing. In a second embodiment the cleansing and refilling of the system up to the spray gun is accomplished with the gun closed the cleaning fluid passing out to a waste tank. The use of pneumatically actuated valves and controls particularly in the spray zone is said to reduce fire and explosion risk.