Automatic bleed valves.

摘要

An automatic bleed valve bleeds gas from a liquid reservoir. It comprises a housing (10) having a passage extending between an inlet (11) and an outlet (12) with the passage including a bore (15) in which a piston (17) is slidably received. The piston (17) includes a capillary (23) providing fluid communication between the inlet (11) and a chamber (16) formed in the passage adjacent the outlet (12). The piston (17) is biased into an upstream position in which gas entering the inlet (11) passes through the capillary (23) to the chamber (16) and thence to the outlet (12). However, the passage of liquid through the capillary (23) so increases the pressure drop across the piston (17) as to move the piston (17) to a downstream position in which the piston closes the outlet (12) to prevent communication between the chamber (16) and the outlet (12), thus closing the valve. A downstream end (24) of the piston (17) is located in the chamber and has a greater area than the upstream end of the piston (17) so that when the piston (17) is in the downstream position the pressure of liquid in the chamber (16) acting on the greater area maintains the valve closed, thus allowing the valve to accommodate pressure fluctuations in the reservoir. By a suitable reversal of parts, the valve can be used to bleed liquid from a pressurized gas reservoir.