Electro-hydraulic valve positioner

Abstract

The current invention relates to motor valves and actuators associated with such motor valves. More particularly, the current invention relates to an electro-hydraulic positioner for such actuators so that the valve can be opened, closed or partially opened. The invention also relates to a method for positioning an actuator for a motor valve. The method utilizes a hydraulic liquid.

What is claimed is: 
     
         1 . An apparatus comprising:
 an electro-hydraulic valve positioner comprising:
 a first conduit; 
 a second conduit; 
 a pump having an inlet for receiving a hydraulic liquid from said first conduit and an outlet for discharging said hydraulic liquid to said second conduit; 
 a check valve in fluid flow communication with said outlet and said second conduit, said check valve prevents backflow from said second conduit to said second conduit; 
 an electromechanical valve in fluid flow communication with said first conduit and said second conduit and having a first position allowing fluid flow between said first conduit and said second conduit and a second position preventing fluid flow between said first conduit and said second conduit. 
   
     
     
         2 . The apparatus of  claim 1  further comprising an electronic control unit which turns said pump on in response to a first signal, turns said pump off in response to a second signal and switches said electro-mechanical valve from said first position to said second position in response to a third signal. 
     
     
         3 . The apparatus of  claim 1  wherein said electromechanical valve is a solenoid valve. 
     
     
         4 . The apparatus of  claim 1  further comprising a source of hydraulic liquid in fluid flow communication with said first conduit and wherein said hydraulic fluid is a hydraulic oil. 
     
     
         5 . The apparatus of  claim 1  further comprising a motor valve operationally connected to said electro-hydraulic valve positioner such that said motor valve is changed from a first position to a second position based on flow of hydraulic liquid between said first conduit and said second conduit. 
     
     
         6 . The apparatus of  claim 5  wherein said motor valve comprises:
 a control valve; and 
 an actuator assembly having a diaphragm having a first side at a first pressure and a second side at a second pressure wherein, when said second pressure is not greater than said first pressure by a predetermined amount, said control valve is in said first position and, when said second pressure is greater than said first pressure by said predetermined amount, said control valve is in said second position; wherein said first conduit is in fluid flow communication with said first side of said diaphragm and said second conduit is in fluid flow communication with said second side of said diaphragm; and wherein said hydraulic liquid is discharged at a higher pressure than it is received, such that hydraulic liquid discharged from said pump increases said second pressure and fluid flow through said electromechanical valve decreases said second pressure. 
 
     
     
         7 . The apparatus of  claim 6  further comprising an electronic control unit which turns said pump on in response to a first signal, turns said pump off in response to a second signal and switches said electromechanical valve from said first position to said second position in response to a third signal. 
     
     
         8 . The apparatus of  claim 7  further comprising a sensor which sends said second signal to said electronic control unit when a predetermined pressure set point is reached by said second pressure. 
     
     
         9 . The apparatus of  claim 8  wherein said sensor is a pressure transducer which is operationally connected to said actuator assembly such that said pressure transducer can sense said second pressure and send said second signal to said electronic control unit when a predetermined pressure set point is reached by said second pressure. 
     
     
         10 . The apparatus of  claim 8  wherein said actuator assembly has an actuator stem operationally connected to said control valve and which is moved based on said second pressure and wherein said sensor is a position sensor operationally connected to said actuator stem wherein said position sensor sends said second signal when said actuator stem reaches a predetermined position. 
     
     
         11 . An apparatus comprising:
 a motor valve comprising
 a control valve; and 
 an actuator assembly having a diaphragm having a first side at a first pressure and a second side at a second pressure wherein, when said second pressure is not greater than said first pressure by a predetermined amount, said control valve is in a first position and, when said second pressure is greater than said first pressure by a predetermined amount, said control valve is in a second position; 
   a fluid reservoir for containing a hydraulic liquid;   an electro-hydraulic valve positioner comprising:
 a first conduit in fluid flow communication with said first side of said diaphragm and in fluid flow communication with said fluid reservoir; 
 a second conduit in fluid flow communication with said second side of said diaphragm; 
 a pump having an inlet for receiving said hydraulic liquid from said first conduit and an outlet for discharging said hydraulic liquid to said second conduit, wherein said fluid is discharged at a higher pressure than it is received; 
 a check valve in fluid flow communication with said outlet and said second conduit, said check valve prevents backflow from said second conduit to said second conduit; 
 a solenoid valve in fluid flow communication with said first conduit and said second conduit and having a first position preventing fluid flow between said first conduit and said second conduit and a second position allowing fluid flow between said first conduit and said second conduit; 
 an electronic control unit which turns said pump on in response to a first signal, turns said pump off in response to a second signal and switches said solenoid valve from said first position to said second position in response to a third signal; 
 a sensor which sends said second signal to said electronic control unit when a predetermined pressure set point is reached by said second pressure. 
   
     
     
         12 . A process for positioning an actuator for a motor valve comprising:
 (a) receiving a first signal regarding a state of a first fluid;   (b) activating a pump in response to said first signal to thus introduce a hydraulic liquid into a second zone at a second pressure from a first zone at a first pressure wherein said second pressure is greater than said first pressure to thus produce a pressure difference;   (c) positioning said actuator in response to said pressure difference;   (d) deactivating said pump in response to a second signal wherein said deactivating occurs when said second pressure reaches a predetermined pressure set point;   (e) activating a valve in response to a third signal regarding said state of said first fluid to thus introduce said hydraulic liquid into said first zone from said second zone such that said pressure difference is reduced; and   (f) positioning said actuator in response to said thus reduced pressure difference.   
     
     
         13 . The process of  claim 12  wherein said predetermined pressure set point is determined based upon said first signal. 
     
     
         14 . The process of  claim 13  further comprising generating said second signal based on the position of said actuator. 
     
     
         15 . The process of  claim 12  wherein said first zone is on a first side of a diaphragm and said second zone is on a second side of a diaphragm and steps (c) and (f) of positioning said actuator further comprise moving said diaphragm by said pressure difference and positioning an actuating stem in response to said movement of said diaphragm. 
     
     
         16 . The process of  claim 15  further comprising generating said second signal based on the position of said actuator stem. 
     
     
         17 . The process of  claim 15  comprising sensing said second pressure by a pressure transducer and generating said second signal by said pressure transducer. 
     
     
         18 . The process of  claim 12  wherein an electronic control unit receives said first signal, said second signal and said third signal, and controls said pump and said valve based on said signals. 
     
     
         19 . The process of  claim 12  wherein said state of said first fluid is the level of said first fluid in a container.