IMPROVEMENTS IN METERING DEVICES

摘要

A check valve (1) comprising a body (2) having an inlet (4) and an outlet (28), an inlet chamber (5) and an outlet chamber (27) mounted in the said body (2) between the inlet (4) and the outlet (28), the said inlet chamber (5) being provided with a check valve to permit or prevent the flow of liquid from the inlet chamber (5) to the outlet chamber (27), the check valve comprising a diaphragm (7) and pressurising means to exert a pressure on the said diaphragm (7), wherein the pressurising means provides for a variable pressure to be exerted on the said diaphragm.