Fluid relay apparatus

摘要

A control valve includes a single diaphragm as a common wall between an input signal chamber having an input port and an output chamber having a central supply port and an exhaust orifice. The orifice has a seating face parallel to and spaced from the diaphragm. A spring-loaded ball valve unit in the supply passage is aligned with an operator moving with the diaphragm. An increasing input signal first moves the diaphragm to close the exhaust orifice and thereafter moves the operator to open the supply valve. Pressure builds in the output chamber, tending to return the diaphragm and close the supply valve until the output and pilot pressure are balanced. The supply valve then closes. As the exhaust is sealed off, this effectively seals the output chamber. If the signal decreases, the diaphragm uncovers the exhaust orifice until a new balanced state is created. In high flow capacity systems a multiplicity of exhaust orifices are employed to match exhaust and supply flow capacity while maintaining minimal leakage.