Slow-acting on/off valve

Abstract

Disclosed is a slow-acting ON/OFF valve which includes a valve-opening pressure chamber that makes an actuating member (which actuates a valve body that comes into contact with and moves away from a valve seat to close and open a flow passage) move in a valve-opening direction against a spring biasing force in a valve-closing direction, and supplies air to the valve-opening pressure chamber, in minute increments, via a flow rate regulation valve. In this slow-acting ON/OFF valve, the dead time from the receipt of a valve-opening signal to the commencement of a valve-opening operation is short. A manifold is provided independently of the valve-opening pressure chamber. Between the valve-opening pressure chamber and the manifold, the following three valves are provided: a pressure regulation valve which allows air to flow into the valve-opening pressure chamber from the manifold until pressure in the valve-opening pressure chamber reaches a predetermined reserve pressure and which is closed upon the pressure in the valve-opening pressure chamber reaching the reserve pressure; a flow rate regulation valve which supplies air to the valve-opening pressure chamber from the manifold, in minute increments, after the pressure in the valve-opening pressure chamber reaches the reserve pressure; and an exhaust valve which rapidly discharges air in the valve-opening pressure chamber to the manifold upon pressure in the manifold dropping below the pressure in the valve-opening pressure chamber and is thereafter closed.