Pneumatic valve actuator sequencing control system and sequencing relay

Abstract

A multi-valve, multi-port, relay device used in a control system for sequentially pressurizing a first reservoir before a second and depressurizing the second reservoir before the first. A piston valve configuration for blocking a second outlet permitting an external pressure supply source to pressurize an external reservoir via a first outlet. The piston is biased in the second outlet blocking position by a spring having a force preselected by the operator via an adjustment screw. A pressure force greater than the piston spring biasing force opens the piston valve configuration. When open, the piston valve configuration and a check valve configuration cooperates to block flow out of the first outlet, but permit flow out the second outlet to a second external reservoir, until full pressurization. An overpressurization feature enables the bleed off of pressure increases associated with thermal expansion of the working fluid. Termination of the supply pressure gives rise to an associated backflow pressure from both external reservoirs, but the piston valve configuration stays open temporarily due to the backpressure from the first outlet, thereby permitting depressurization of the second external reservoir, following which the piston closes permitting a first external reservoir to depressurize and in a low pressure operable embodiment thereof, the second external reservoir begins a residual pressure bleed off stage via a poppet valve.