Automatic flow control valve with variable set-points

摘要

The invention provides a pilot valve apparatus for use in an automatic liquid control system (10) for maintaining pressure downstream from a main control valve between two set-points according to flow rate through the main control valve (18). The pilot valve has a flexible pilot diaphragm which cooperates with pilot valve members to control liquid flow through the pilot valve (12) apparatus to control the main control valve. An actuator apparatus (83) cooperating with 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 force transfer varies flow through the pilot valve apparatus to control the main control valve. To limit downstream pressure, movement of the actuator partition can be opposed by a spring and/or an adjustable stop, or a housing of the actuator can be shaped to selectively support portions of the actuator partition.