Fluid flow instrument

Claim 1

IN A VERTICAL SPEED INDICATOR FOR AIRCRAFT, A SHAFT, A HOUSING HAVING TWO SUBSTANTIALLY PARALLEL SPACED PLATES AND A MEMBER JOINING SAID PLATES AND HAVING THE MAJOR PORTION OF ITS INTERIOR SURFACE OF CYLINDRICAL CURVATURE ABOUT THE AXIS THEREOF, EACH SAID PLATE HAVING AN APERTURE COAXIAL WITH SAID AXIS, A SHAFT PASSING THROUGH SAID APERTURES AND ROTATABLE THEREIN, A PAIR OF BEARINGS DISPLACED FROM SAID APERTURES AND SUPPORTING SAID SHAFT FOR ROTATION, A VANE ATTACHED TO SAID SHAFT AND ROTATABLE IN SAID HOUSING AND IN CLOSE PROXIMITY TO SAID PLATES AND SAID MEMBER, PARTITION MEANS SEPARATING THE INTERIOR SPACE OF SAID HOUSING INTO A FIRST COMPARTMENT AND A SECOND COMPARTMENT LIMITED BY SAID PARTITION MEANS AND SAID VANE, A RESERVOIR FOR AIR, CONDUIT MEANS CONNECTING SAID SECOND COMPARTMENT WITH SAID RESERVOIR, CONDUIT MEANS CONNECTING SAID FIRST COMPARTMENT WITH THE ATMOSPHERE, AND CONDUIT MEANS DIRECTLY CONNECTING ONE OF SAID APERTURES WITH SAID RESERVOIR, THE CONNECTION BEING MADE ADJACENT THE OUTSIDE SURFACE OF ONE SAID PLATE.