Mine roof support safety valve - has metallic insert between flexible plunger portions separating gas cushion and pressurised fluid chambers

摘要

The safety valve for a mine roof support has a rigid body in which is a blocking element which is biassed to a position blocking communication between inlet and outlet ports. The blocking element has two flexible portions which a separated by a metallic insert, one portion being acted on by the pressurised fluid and the other by the bias which is a gas cushion. The metallic insert is pref. in the form of a disc or the finger of a glove. In the latter case, one of the flexible portions is received within the insert which itself is received within the other flexible portion.