Method and apparatus for gas flow control

Abstract

A method and apparatus for self-calibrating control of gas flow. The gas flow rate is initially set by controlling, to a high degree of precision, the amount of opening of a flow restriction, where the design of the apparatus containing the flow restriction lends itself to achieving high precision. The gas flow rate is then measured by a pressure rate-of-drop upstream of the flow restriction, and the amount of flow restriction opening is adjusted, if need be, to obtain exactly the desired flow.

1 . An apparatus for controlling the flow of fluid, comprising:
 a first block having a flow restriction surface;   a second block having a complementary flow restriction surface, wherein the flow restriction surface and the complementary flow restriction surface cooperate to form a flow restriction valve;   a fluid inlet hole formed in one of the first block or second block and providing fluid passage to the flow restriction valve;   a fluid outlet hole formed in one of the first block or second block and providing fluid passage to the flow restriction valve;   a seal provided about the flow restriction valve; and,   wherein a change in the amount of the flow restriction valve opening is effected by elastic flexure of at least one of the first block or second block.   
     
     
         2 . The apparatus of  claim 1 , further comprising a displacement sensor. 
     
     
         3 . The apparatus of  claim 2 , wherein the displacement sensor is configured to measure amount of flow restriction opening to a precision of at least 100 nanometers. 
     
     
         4 . The apparatus of  claim 2 , further comprising an actuator operable to cause the elastic flexure. 
     
     
         5 . The apparatus of  claim 4 , further comprising a feedback receiving output of the displacement sensor and controlling the amount of flow restriction valve opening by sending an actuating signal to the actuator. 
     
     
         6 . The apparatus of  claim 4 , wherein the actuator comprises a piezoelectric actuator. 
     
     
         7 . The apparatus of  claim 5 , wherein the feedback controls the amount of flow restriction valve opening to a precision of at least 100 nanometers. 
     
     
         8 . The apparatus of  claim 2 , wherein the displacement sensor's measurement is carried out at least once every 100 milliseconds. 
     
     
         9 . The apparatus of  claim 1 , wherein at least one of the first block or the second block comprises a cantilever arrangement. 
     
     
         10 . A system for precision gas delivery, comprising:
 a flow control valve;   a pressure transducer measuring gas pressure upstream of the flow control valve;   a temperature sensor;   a flow regulator positioned upstream of the flow control valve;   a conduit coupling the flow regulator to the flow control valve; and,   a controller receiving signals from the pressure transducer and temperature sensor and controlling the operation of the flow control valve according to flow calculation;   wherein the flow control valve comprises an actuator varying the amount of gas flow by elastically flexing a body part of the flow control valve.   
     
     
         11 . The system of  claim 10 , wherein the flow control valve further comprises a displacement sensor measuring the elastic flexing of the body part and sending a corresponding signal to the controller. 
     
     
         12 . The system of  claim 11 , wherein the controller controls the amount of flow restriction opening of the flow control valve to a precision of at least 100 nanometers. 
     
     
         13 . The system of  claim 11 , wherein the signal of the displacement sensor is carried out at least once every 100 milliseconds. 
     
     
         14 . The system of  claim 10 , wherein the controller determines the flow rate through the flow control valve by actuating the flow regulator to temporarily interrupting gas flow upstream of the flow control valve and using the pressure transducer to measure the rate of drop in pressure in the conduit. 
     
     
         15 . The system of  claim 10 , wherein the flow regulator comprises a metering valve. 
     
     
         16 . The system of  claim 10 , wherein the body part of the flow control valve comprises a flow restriction surface, and wherein the flow control valve further comprises:
 a second body part having a complementary flow restriction surface, wherein the flow restriction surface and the complementary flow restriction surface cooperate to form a flow restriction valve;   a fluid inlet hole formed in one of the first body part or the second body part and providing fluid passage to the flow restriction valve;   a fluid outlet hole formed in one of the first body part or the second body part and providing fluid passage to the flow restriction valve;   a seal provided about the flow restriction valve; and,   wherein a change in the amount of the flow restriction valve's opening is effected by elastic flexure of at least one of the first body part or the second body part.   
     
     
         17 . A method for controlling flow rate through gas delivery system having a flow control valve, a flow regulator, and a known gas confinement volume coupled between the flow regulator and the flow control valve; comprising:
 actuating the flow control valve to deliver a desired flow rate;   temporarily interrupting gas flow through the flow regulator;   measuring temperature of the gas;   measuring pressure drop of the gas within the known volume;   using the measured temperature, pressure drop and known volume to calculate flow rate through the flow control valve;   resuming flow through the flow regulator; and,   using calculated flow rate to adjust the flow through the flow control valve by activating an actuator to cause elastic flexure of a body part of the flow control valve.   
     
     
         18 . The method of  claim 17 , further comprising measuring the elastic flexure displacement of the body part. 
     
     
         19 . The method of  claim 17 , wherein the flow regulator comprises a metering valve and wherein the step of resuming flow comprises gradually opening the metering valve to thereby control the pressure rise in the known volume. 
     
     
         20 . The method of  claim 17 , wherein adjusting the flow through the flow control valve comprises activating the actuator to cause elastic flexure of the body part about a cantilever part.