US 5,348,036 AGranted

Automatic control valve

AssigneeSinger Valve Inc.

InventorsKari J. Oksanen, Grant V. LaBar

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Abstract

An automatic control valve has a main valve member moveable between open and closed positions thereof in response to pressure applied to a first piston or diaphragm in a first control chamber. The valve member moves to modulate flow through the valve to maintain desired flow conditions. Pilot pressure signals are generated to reflect the flow conditions, usually upstream and downstream from the valve, which signals are processed to generate a control signal which is fed to the first control chamber to control pressure therein. Normal movement of the valve produces wear which causes leakage of the diaphragm or seals oft he piston causing loss of primary control of the valve member which tends to fail "open". This causes an initial rise in flow through the valve which is detected by the pilot pressure signal but because of the leakage, is unable to correct. This prior art problem is avoided by providing a back-up piston or diaphragm which is maintained in an inactive position during normal operation of the valve by the first piston or diaphragm, and thus does not wear. When pilot pressure signals reflect primary control failure, the back-up piston or diaphragm moves to an active position and selectively cooperates with the main valve member to control flow conditions through the valve independently of the first control chamber.

Claims20

Dependent claims

An automatic control valve comprising:

(a) a valve body having an inlet port, an outlet port, and a valve seat disposed between the ports, the valve seat defining a valve opening to permit communication between the ports,
(b) a main valve member moveable between a closed position against the seat to close the valve, and an open position spaced from the seat to control flow of liquid through the valve opening to maintain a desired flow condition through the valve,
(c) a first partition means moveable between extended and retracted positions thereof to reflect the two positions of the main valve member, the first partition means cooperating with the valve body to define in part a variable volume first control chamber, the first control chamber being exposed to a first control pressure which reflects the liquid flow condition through the valve, the control pressure acting on the first partition means to move the first partition means, the first partition means cooperating with the valve member so that the valve member moves in response to changes in the first control pressure to attempt to position the valve member to maintain the desired liquid flow condition through the valve,
(d) a second partition means being moveable between inactive and active positions thereof, the second partition means cooperating with the valve body to define in part a variable volume second control chamber, the second control chamber being exposed to a second control pressure which reflects an unacceptable deviation of liquid flow through the valve from the desired flow condition, the second partition means being retained in the retracted position thereof when deviations of the liquid flow conditions through the valve are acceptable, and
(e) second partition coupling means for selectively coupling the second partition means with the valve member should the deviation of the flow conditions through the valve become unacceptable, which increases the second control pressure to become sufficiently high to position the valve member in response to the second control pressure.

2 more elements

A method of automatically controlling liquid flow through a valve, the method comprising the steps of:

(a) detecting an acceptable first flow condition through the valve and generating a first control signal to reflect an acceptable deviation from a desired flow condition through the valve,
(b) displacing a main valve member in response to the first control signal by varying pressure in a first control chamber, the main valve member being displaced by a first partition means with respect to a valve seat in a direction to attempt to maintain the desired flow condition,
(c) detecting an unacceptable second flow condition through the valve and generating a second control signal to reflect an unacceptable deviation from the desired flow condition, and
(d) displacing the main valve member in response to the second control signal by varying pressure in a second control chamber, the main valve member being displaced by a second partition means with respect to the valve seat in a direction to attempt to maintain the desired flow condition.

1 more element

Dependencies are inferred from the claim text.