Automatic flow control valve with variable set-points

An automatic fluid control system comprising:

• (a) a main valve apparatus having:
• a main valve body with an inlet port, an outlet port and a main valve seat disposed between the ports;
• a main valve member moveable between an open position clear of the valve seat and a closed position engaging the valve seat;
• a main valve diaphragm cooperating with the main valve member and main valve body to define a control chamber having a control port, the main valve member being responsive to control pressure within the control chamber acting on the main valve diaphragm;
• (b) a pilot valve apparatus having a flexible pilot diaphragm, a pilot inlet port, and a pilot outlet port, the ports communicating with one side of the pilot diaphragm;
• the pilot valve apparatus also comprising an actuator apparatus having a moveable actuator partition, and first and second actuator ports communicating with opposite sides of the actuator partition;
• (c) a T-junction having a T-inlet port, a T-control port, and a T-pilot port;
• (d) an inlet conduit communicating the inlet port of the main valve with the T-inlet port of the T-junction, a control conduit communicating the control port of the main valve with the T-control port, and a pilot conduit communicating the pilot inlet port of the pilot valve apparatus with the T-pilot port;
• (e) first and second pressure differential conduits communicating with the first and second actuator ports respectively to apply a force to the actuator partition dependent on fluid flow through the main valve;
• and
• (f) a resilient connector cooperating with the actuator partition and the pilot diaphragm to permit limited relative movement therebetween and to transfer a first resilient force to the pilot diaphragm resulting from movement of the actuator partition so as to vary flow through the pilot valve apparatus.

A pilot valve apparatus comprising:

• (a) a pilot valve body having a pilot inlet port and a pilot outlet port communicating with an interior of the valve body;
• (b) a flexible pilot diaphragm dividing the interior of the pilot valve body into first and second pilot chambers on opposite sides of the pilot diaphragm;
• (c) a first pilot valve member and a second pilot valve member cooperating with each other to control flow through the ports, the first pilot valve member being fixed relative to the pilot valve body and the second pilot valve member being responsive to the position of the pilot diaphragm;
• (d) an actuator apparatus having an actuator body and a moveable actuator partition, the partition dividing an interior of the actuator body into first and second actuator chambers, the actuator body having first and second actuator ports communicating with the first and second actuator chambers respectively;
• and
• (e) means to permit limited independent relative movement between the pilot diaphragm and the actuator partition, and to transfer force from the actuator partition to the pilot diaphragm to vary flow through the pilot valve, the means to permit said limited movement cooperating with the pilot diaphragm and the actuator partition.

A method of controlling fluid flow through a main valve to maintain downstream pressure substantially between two pre-determined set-points, the method comprising the steps of:

• (a) detecting inlet pressure in fluid flow adjacent an inlet of the main valve and generating a control pressure signal proportional to said inlet pressure;
• (b) transmitting a first portion of the control pressure signal to act on a main valve member of the main valve to control position of the main valve member based on flow through the main valve;
• (c) transmitting a second portion of the control pressure signal to a pilot valve apparatus to control flow therethrough, the pilot valve apparatus having a flexible pilot diaphragm;
• (d) generating two pressure differential signals to reflect the fluid flow rate through the main valve;
• (e) transmitting the pressure differential signals to opposite sides of a moveable actuator partition of an actuator to deflect the actuator partition in response to said pressure differential signal;
• (f) transmitting downstream pressure to the pilot diaphragm;
• and
• (g) transmitting a resilient force to the pilot diaphragm arising from at least a portion of said deflection of the actuator partition so as to vary flow through the pilot valve, which in turn modifies the control pressure acting on the main valve member to re-position the main valve member to maintain downstream pressure substantially between the set-points.

A method of controlling fluid flow through a main valve to maintain downstream pressure substantially between two pre-determined set-points, the method comprising the steps of:

• (a) detecting inlet pressure in fluid flow adjacent an inlet of the main valve and generating a control pressure signal proportional to said inlet pressure;
• (b) transmitting a first portion of the control pressure signal to act on a main valve member of the main valve to control position of the main valve member based on flow through the main valve;
• (c) transmitting a second portion of the control pressure signal to a pilot valve apparatus to control flow therethrough, the pilot valve apparatus having a flexible pilot diaphragm;
• (d) generating two pressure differential signals to reflect the fluid flow rate through the main valve;
• (e) transmitting the pressure differential signals to opposite sides of a moveable actuator partition of an actuator to deflect the actuator partition in response to said pressure differential signal;
• (f) transmitting downstream pressure to the pilot diaphragm;
• and
• (g) permitting limited independent relative movement between the pilot diaphragm and the actuator partition and transferring force from the actuator partition to the pilot diaphragm to vary flow through the pilot valve to reposition the main valve member to maintain downstream pressure substantially between the set-points.