Process-chamber flow control system

A system for controlling air flowing from an environment, where the air is substantially still, through parallel conduits, to an exhaust, wherein pressure from the exhaust is substantially less than pressure from the environment, comprising:

• a first regulator for maintaining in a first plenum disposed in one conduit a pressure that is between the pressures of the environment and the exhaust, the first regulator including a first piston having a frontal face, the entire frontal face being directly exposed to the flow of air in the first plenum, the first piston further including a distal face exposed to the pressure of the environment, the first piston being mounted so as to variably impede the flow of air through the first regulator, and so that the first plenum pressure that remains a constant amount less than pressure from the environment and independent of pressure from the exhaust;
• and
• a second regulator for maintaining in the second plenum disposed in a second conduit a pressure that is between the pressures of the environment and the exhaust, the second regulator including a second piston having a frontal face, the entire frontal face being directly exposed to the flow of air in the second plenum, the second piston further including a distal face exposed to the pressure of the environment, the second piston being mounted so as to variably impede the flow of air through the second regulator, and so that the second plenum pressure that remains a constant amount less than pressure from the environment and independent of pressure from the exhaust;
• wherein the first and second plenums are separate and distinct, such that (i) the first plenum pressure may be different from the second plenum pressure, (ii) the first plenum pressure is not affected by changes in the amount of flow through the second plenum, and (iii) the second plenum pressure is not affected by changes in the amount of flow through the first plenum.

A system for controlling air flowing from an environment, where the air is substantially still, through parallel conduits, to an exhaust, wherein pressure from the exhaust is substantially less than pressure from the environment, comprising:

• a first regulator for maintaining in a first plenum disposed in one conduit a pressure that is between the pressures of the environment and the exhaust and that is a constant amount less than the pressure of the environment, the first regulator including a first piston and a constriction point formed by the first piston, the first piston having a frontal face, the entire frontal face being directly exposed to the flow of air in the first plenum and being upstream from the constriction point, and a distal face that is exposed to the pressure of the environment, the first piston being mounted so as to variably impede the flow of air through the first regulator, and so that the first plenum pressure that remains a constant mount less than pressure from the environment and independent of pressure from the exhaust;
• and
• a second regulator for maintaining in the second plenum disposed in a second conduit a pressure that is between the pressures of the environment and the exhaust and that is a constant amount less than the pressure of the environment, the second regulator including a second piston and a constriction point formed by the second piston, the second piston having a frontal face, the entire frontal face being directly exposed to the flow of air in the second plenum and being upstream from the constriction point, and a distal face that is exposed to the pressure of the environment, the second piston being mounted so as to variably impede the flow of air through the second regulator, and so that the second plenum pressure that remains a constant amount less than pressure from the environment and independent of pressure from the exhaust.