System for controlling flow through a process region

A device, connected to an evacuation means, for regulating in a region a partial vacuum with respect to a reference pressure, the device comprising:

• a path, through which fluid passes from the region to the evacuation means;
• a movably mounted piston having a frontal face, which is exposed to fluid in the path, and a distal face, which is exposed to a reference pressure, the piston being disposed in the path so that the piston may constrict the path at a constriction point, wherein fluid in the path on the evacuation means side of the constriction point exerts a pressure on the piston in a direction transverse to the piston's direction of movement, and the piston being mounted so that the weight of the piston exerts a force on the piston in a direction that tends to widen the path at the constriction point;
• a base that can be moved with respect to the portion of the path at the constriction point;
• and
• a spring, one end of which is attached to the piston and the other end of which is attached to the base, wherein the spring is mounted to the distal face of the piston;
• wherein the partial vacuum in the region is with respect to an environment's pressure, fluid flows from the environment into the region and then into the device, and the reference pressure is the environment's pressure.

A device, connected to an evacuation means, for regulating in a region a partial vacuum with respect to a reference pressure, the device comprising:

• a path, through which fluid passes from the region to the evacuation means;
• a movably mounted piston having a frontal face, which is exposed to fluid in the path, and a distal face, which is exposed to a reference pressure, the piston being disposed in the path so that the piston may constrict the path at a constriction point, wherein fluid in the path on the evacuation means side of the constriction point exerts a pressure on the piston in a direction transverse to the piston's direction of movement, and the piston being mounted so that the weight of the piston exerts a force on the piston in a direction that tends to widen the path at the constriction point;
• wherein the frontal face has an effective area against which fluid in the path exerts a pressure, the distal face has an effective area against which the pressure of fluid upstream of the frontal face is exerted, and the effective areas of the frontal and distal faces are substantially equal to each other;
• a base that can be moved with respect to the portion of the path at the constriction point;
• and
• a spring, one end of which is attached to the piston and the other end of which is attached to the base.

A device, connected to an evacuation means, for regulating in a region a partial vacuum, the device comprising:

• an inlet connected to the region;
• an outlet connected to the evacuation means;
• a path bounded by a rigid wall, through which fluid passes from the inlet to the outlet, the path not being vented at any point between the inlet and the outlet;
• a piston-mounting structure;
• a piston, movably mounted on the piston-mounting structure, the piston having a rim, a frontal face, which is exposed to fluid in the path between the inlet and the outlet, and which has a central portion, and a distal face, which is exposed to a reference chamber having a reference pressure greater than the evacuation means's pressure, the piston being disposed in the path so that the piston may constrict the path between the piston's rim and the path's wall at a constriction point, wherein the piston is disposed in the path so that the fluid flows radially outward from the frontal face's central portion towards the piston's rim before flowing through the constriction point, and wherein the piston has a skirt which surrounds a portion of the piston mounting structure;
• and
• a spring for exerting a force on the piston, the spring being located within the piston's skirt and the piston-mounting structure.

A device, connected to an evacuation means, for regulating in a region a partial vacuum, the device comprising:

• a path bounded by a rigid wall, through which fluid passes from the region to the evacuation means;
• a piston-mounting structure;
• a piston, movably mounted on the piston-mounting structure, the piston having a rim, a frontal face, which is exposed to fluid in the path, and a distal face, which is exposed to a reference chamber having a reference pressure, the piston being disposed in the path so that the piston may constrict the path between the piston's rim and the path's wall at a constriction point;
• and
• a spring for exerting a force on the piston, the spring being located within the piston and the piston-mounting structure;
• wherein the partial vacuum in the region is with respect to an environment's pressure, fluid flows from the environment into the region and then into the device, and the reference pressure is the environment's pressure, and wherein the spring is under compression so as to exert a force on the piston in a direction that tends to narrow the path at the constriction point.

A device, connected to an evacuation means, for regulating in a region a partial vacuum, the device comprising:

• a path bounded by a rigid wall, through which fluid passes from the region to the evacuation means;
• a piston-mounting structure;
• a piston, movably mounted on the piston-mounting structure, the piston having a rim, a frontal face, which is exposed to fluid in the path, and a distal face, which is exposed to a reference chamber having a reference pressure, the piston being disposed in the path so that the piston may constrict the path between the piston's rim and the path's wall at a constriction point;
• and
• a spring for exerting a force on the piston, the spring being located within the piston and the piston-mounting structure;
• wherein the frontal face has an effective area against which fluid in the path exerts a pressure, the distal face has an effective area against which the reference pressure is exerted, and the effective areas of the frontal and distal faces are substantially equal to each other;
• and
• wherein the partial vacuum in the region is with respect to an environment's pressure, fluid flows from the environment into the region and then into the device, and the reference pressure is the environment's pressure.

A device, connected to an evacuation means, for regulating in a region a partial vacuum, the device comprising:

• a path bounded by a rigid wall, through which fluid passes from the region to the evacuation means;
• a piston-mounting structure;
• a piston, movably mounted on the piston-mounting structure, the piston having a rim, a frontal face, which is exposed to fluid in the path, and a distal face, which is exposed to a reference chamber having a reference pressure, the piston being disposed in the path so that the piston may constrict the path between the piston's rim and the path's wall at a constriction point;
• a spring for exerting a force on the piston, the spring being located within the piston and the piston-mounting structure;
• and
• buffering-fluid means for supplying a buffering fluid to a point between the piston and the piston-mounting structure such that a first portion of the buffering fluid flows into the path and a second portion of the buffering fluid flows into the reference chamber.

A device, connected to an evacuation means, for regulating in a region a partial vacuum, the device comprising:

• an inlet connected to the region;
• an outlet connected to the evacuation means;
• a path bounded by a wall, through which fluid passes from the inlet to the outlet, the path not being vented at any point between the inlet and the outlet;
• a movably mounted piston, the piston having a rim and a frontal face, which is exposed to fluid in the path between the inlet and the outlet, the frontal face having a central area, the piston also having a distal face, which is exposed to a reference pressure greater than the evacuation means's pressure, the piston being disposed in the path so that the piston may constrict the path between the piston's rim and the path's wall at a constriction point, and so that fluid flows radially outward from the frontal face's central portion towards the piston's rim before flowing through the constriction point, wherein the piston has a skirt extending from the rim;
• and
• a spring for exerting a force on the piston, the spring being located within the piston's skirt.

A device, connected to an evacuation means, for regulating in a region a partial vacuum, the device comprising:

• a path bounded by a wall, through which fluid passes from the region to the evacuation means;
• a movably mounted piston, the piston having a rim and a frontal face, which is exposed to fluid in the path, the frontal face having a central area, the piston also having a distal face, which is exposed to a reference pressure, the piston being disposed in the path so that the piston may constrict the path between the piston's rim and the path's wall at a constriction point, and so that fluid flows radially outward from the frontal face's central portion towards the piston's rim before flowing through the constriction point;
• and
• a spring for exerting a force on the piston;
• wherein the distal face of the piston is exposed to a reference chamber and the piston is mounted on a piston-mounting structure, the device further including buffering-fluid means for supplying a buffering fluid to a point between the piston and the piston-mounting structure, such that a first portion of the buffering fluid flows into the path and a second portion of the buffering fluid flows into the reference chamber.

A device for controlling the flow of a first fluid, the device comprising:

• a passageway through which the fluid flows;
• a piston movably mounted so that as the piston moves the piston applies a varying resistance to the flow through the passageway;
• a piston-mounting structure on which the piston is mounted, the piston-mounting structure and the piston defining a chamber in fluid communication with an environment;
• and
• second-fluid means for supplying a second fluid to a point between the piston and the piston-mounting structure, such that a first portion of the second fluid flows into the passageway and a second portion of the second fluid flows into the chamber;
• wherein the piston includes a skirt which surrounds a portion of the piston-mounting structure, and the point to which the second-fluid supplying means supplies the second fluid is between the piston-mounting structure and the piston's skirt.

A device, for controlling the flow of a first fluid, the device comprising:

• a passageway through which the fluid flows;
• a piston movably mounted so that as the piston moves the piston applies a varying resistance to the flow through the passageway;
• a piston-mounting structure on which the piston is mounted, the piston-mounting structure and the piston defining a chamber in fluid communication with an environment;
• and
• second-fluid means for supplying a second fluid to a point between the piston and the piston-mounting structure, such that a first portion of the second fluid flows into the passageway and a second portion of the second fluid flows into the chamber;
• wherein the piston-mounting structure is tilted from a vertical orientation.

A device for regulating the flow of fluid from an environment, where the fluid is substantially still, through a region, then through the device, and to a vacuum source, so as to maintain a substantially constant partial vacuum in the region with respect to the environment, the device comprising:

• a passageway through which the fluid flows from an inlet in fluid communication with the region to an outlet in fluid communication with the vacuum source;
• a piston movably mounted adjacent the passageway, so that as the piston moves the piston applies a varying resistance on the flow through the passageway at a constriction point, the piston having a frontal face exposed to fluid flowing through the passageway upstream of the constriction point, and a distal face opposite the frontal face;
• and
• a piston-mounting structure on which the piston is mounted, the piston-mounting structure and the piston's distal face defining a chamber in fluid communication with an environment, the piston-mounting structure being tilted from a vertical orientation, so that the piston moves along a line offset from vertical, and so that the weight of the piston tends to lower the resistance to the flow, the piston-mounting structure including bearing means for reducing friction between the piston and the piston-mounting structure.

A device, connected to an evacuation means, for regulating in a region a partial vacuum with respect to a reference pressure, the device comprising:

• a path, through which fluid passes from the region to the evacuation means;
• a movably mounted piston having a frontal face, which is exposed to fluid in the path, and a distal face, which is exposed to a reference pressure, the piston being disposed in the path so that the piston may constrict the path at a constriction point, wherein fluid in the path on the evacuation means side of the constriction point exerts a pressure on the piston in a direction transverse to the piston's direction of movement, and the piston being mounted so that the weight of the piston exerts a force on the piston in a direction that tends to widen the path at the constriction point;
• a base that can be moved with respect to the portion of the path at the constriction point;
• a stepper motor for moving the base;
• and
• a spring, one end of which is attached to the piston and the other end of which is attached to the base.