Automatic flow control valve with variable set-points

摘要

The invention provides a pilot valve apparatus for use in an automatic fluid control system for maintaining pressure downstream from a main control valve between two setpoints irrespective of flow changes through the main control valve. The pilot valve has a flexible pilot diaphragm which moves with a moveable pilot valve member to cooperate with a fixed pilot valve member to control fluid flow through the pilot valve apparatus. The pilot valve controls control pressure acting on the main control valve. An actuator apparatus connected to a body of the pilot valve apparatus has a moveable actuator partition which is exposed to a pressure differential signal reflecting flow through the main control valve. A resilient connector cooperates with the actuator partition and the pilot diaphragm to permit limited relative movement therebetween, and to transfer resilient force to the pilot diaphragm resulting from movement of the actuator partition. This transfer varies location of the moveable pilot valve member with respect to the fixed pilot valve member to vary flow through the pilot valve apparatus, so as to vary control pressure, which in turn controls the main control valve. An adjustable actuator stop can cooperate with the actuator partition to limit movement of the actuator partition. An actuator resilient member can cooperate with the actuator partition to apply a force selectively to the actuator partition to resist displacement thereof.