Normalair-garrett (holdings) Limited

Leonard Moore

Owen D Furlong

Jonathan David Ward

Signal output means (11) responsive to gas flow and particularly suited for use in gas flow indicator apparatus (10), has first and second pressure-datum valves (24, 25) arranged in downstream order in a gas conduit (16), the second pressure-datum valve (25) being arranged to open at a lower pressure difference than the first pressure-datum valve (24). A flueric amplifier (15) has a power jet port (28) connected to the gas conduit (16) on the upstream side of the first pressure-datum valve (24), opposed control pressure ports (26, 27) connected respectively to a chamber (22) formed between the first and second pressure-datum valves (24, 25) and to the gas conduit (16) downstream of the second pressure-datum valve (25), and a vent port (30) also connected to the gas conduit (16) downstream of the second pressure-datum valve (25). A pressure signal output by the flueric amplifier (15) in response to gas flow through the conduit (16) may be used to trigger a visual or audio warning device (14).

Gas flow responsive signal output means

A flueric partial pressure sensor includes a flueric bridge having two bridge legs adapted for sensing a reference-gas and sample-gas mixture. A linear resistor and an orifice resistor are incorporated in each of the bridge legs which are conjoined to discharge from a single outlet. The resistors are arranged to provide an asymmetric balance of the flow rates through the bridge legs. The asymmetric balance is selected so that in operation a constant pressure output signal is generated for a chosen partial pressure of a constituent gas of the sample-gas mixture in varying absolute pressure conditions such as changes in altitude. Respective pressure signal outlets connected one with each bridge leg at a position between the linear resistor and the orifice resistor are used to effect control of a flueric laminar flow proportional amplifier. Outputs from the flueric amplifier may be used to regulate a fluid mixing valve shown in FIG. 3, or to effect switching of an indicator device shown in FIG. 4.

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Somerton, United Kingdom

Leonard Moore