Fluidic set point pressure sensor

Abstract

A mechanically offset fluid amplifier for converting the absolute pressuref a pressurized fluid to a differential pressure indicating the pressure of the pressurized fluid relative to a predetermined set point pressure. The device includes two outlets separated by a splitter, a supply nozzle for directing a jet of the pressurized fluid toward a first of the two outlets at a velocity determined by the absolute pressure, and control elements for deflecting the jet toward the second outlet such that as the jet velocity increases from zero, the deflection of the jet increases to a maximum value and then decreases until the differential pressure between the two outlets is equal to zero when the absolute pressure of the pressurized fluid is equal to the predetermined set point pressure. The control elements includes two control inlets disposed on opposite sides of the jet and connected to a common source of control fluid through respective fluidic resistances, the second control inlet being disposed on the same side of the jet at the second outlet. The first and second control inlets include respective first and second forward control edges which are asymmetrically disposed on opposite sides of the jet so that the second control edge is disposed closer to the supply nozzle centerline than the first control edge.

Description

Claims

1. A fluidic set point pressure sensor for converting the absolute pressure of a pressurized fluid to a differential pressure indicating the pressure of the pressurized fluid relative to a predetermined set point pressure, comprising:

input means, connected to receive said pressurized fluid, for directing a jet of fluid along a first centerline at a velocity determined by said absolute pressure;

output means, disposed downstream from said input means, including first and second outlets separated by a splitter which is disposed asymmetrical to said first centerline such that at least a greater portion of said jet directed along said first centerline is received at the first outlet; and

control means for deflecting said jet towards said second outlet in accordance with said jet velocity such that as the jet velocity increases from zero, the deflection of the jet increases to a maximum value, then decreases, so that the differential pressure generated by the jet between the first and second outlets increases to a maximum positive value at which the pressure at the second outlet is greater than the pressure at the first outlet, then decreases to a negative value at which the pressure at the first outlet is greater than the pressure at the second outlet, the differential pressure being equal to zero when said absolute pressure is equal to said predetermined set point pressure, the differential pressure becoming positive whenever said absolute pressure falls below said set point pressure and becoming negative whenever said absolute pressure rises above said set point pressure.

2. A sensor, as described in claim 1, wherein said control means comprises:

a first vane which is disposed downstream from the input means on a first side of the jet adjacent the first outlet and which extends radially inward toward the first centerline to a first vane edge;

a second vane which is disposed opposite the first vane on a second side of the jet adjacent the second outlet and which extends radially inward toward the first centerline to a second vane edge which is disposed closer to the first centerline than the first vane edge;

an interaction zone which is defined by and extends between the input means and the first and second vanes;

a source of control fluid of low pressure which is constant relative to the predetermined set point pressure;

a first resistive fluid communication means for connecting the control fluid source in fluid communication with the first side of the jet in the interaction zone; and

a second resistive fluid communication means for connecting the control fluid source in fluid communication with the second side of the jet in the interaction zone.

3. A sensor, as described in claim 2, wherein the second resistive fluid communication means comprises a variable fluidic resistor.

4. A sensor, as described in claim 3, which further comprises means for venting fluid interposed between the first and second vanes and the output means.

5. A sensor, as described in claim 4, wherein the pressurized fluid is pressurized air and the control fluid source is ambient air at atmospheric pressure.

6. A sensor, as described in claim 5, wherein the fluid venting means includes at least one pair of vents disposed respectively on opposite sides of the jet between the first and second vanes and the output means, for establishing fluid communication between the ambient air and the opposite sides of the jet.

7. A sensor, as described in claim 5, wherein the flow resistance of the first resistive fluid communication means is very small relative to the flow resistance of the second resistive fluid communication means.

8. A fluidic set point pressure sensor for converting the absolute pressure of a pressurized fluid to a differential pressure indicating the pressure of the pressurized fluid relative to a predetermined set point pressure, comprising:

input means, connected to receive said pressurized fluid, for directing a jet of fluid along a first centerline at a velocity determined by said absolute pressure;

output means, disposed downstream from said input means, including first and second outlets separated by a splitter which is disposed asymmetrical to said first centerline such that at least a greater portion of said jet directed along said first centerline is received at the first outlet; and

control means for deflecting the jet towards the second outlet in accordance with the jet velocity such that as the jet velocity increases from zero, the deflection of the jet increases to a maximum value and then decreases, so that the differential pressure generated by the jet between the first and second outlets increases to a maximum positive value and then decreases to a negative value, the differential pressure being equal to zero when the absolute pressure of the pressurized fluid is equal to the predetermined set point pressure, the differential pressure becoming positive whenever said absolute pressure falls below said set point pressure and becoming negative whenever said absolute pressure rises above said set point pressure, said control means including first and second control fluid inlets respectively disposed on opposite sides of the jet and connected to a common source of control fluid through respective first and second fluidic resistive means, the second control inlet being disposed on the same side of the first centerline as the second outlet, the first and second control fluid inlets including respective first and second forward control edges which are asymmetrically disposed on opposite sides of the jet so that the second control edge is disposed closer that the first control edge to the first centerline.

9. A sensor, as described in claim 8, wherein the fluidic resistance of the first fluidic resistive means is less that the fluidic resistance of the second fluidic resistive means.

10. A sensor, as described in claim 9, wherein the second fluidic resistive means comprises an adjustable fluidic resistor.