Vortex-shedding flowmeter having a sensing vane

Claim 1

A vortex-shedding flowmeter comprising: A. a flow tube through which a fluid to be metered is conducted along the axis of the tube; B. a shedder having a predetermined geometry transversely disposed in said tube to divide the flow therein and to cause vortices to be shed alternately on either side thereof at a repetition rate proportional to the flow rate of the fluid, thereby producing downstream trains of vortices moving along the right and left sides of the tube, the wave span between the eyes of successive vortices in each train having a substantially constant length determined by said geometry; C. a vane disposed in said tube between the left and right trains of vortices whereby vortices which pass along the left side of the vane impose forces on the right side thereof and vortices which pass along the right side of the vane impose forces on the left side thereof, said vane being pivoted on a shaft extending along a pivot axis which is normal to the tube axis, the body of said vane being symmetrical with respect to said pivot axis to define like leading and trailing edges, said vane having a length which is about three quarters the length of the wave span, whereby the forces imposed on the vane produce torques causing said vane to vibrate at a frequency in accordance with said repetition rate; and D. means operatively coupled to said vibrating vane to sense the vibrations thereof to produce a corresponding signal.