GB796864A - Means for measuring or indicating speeds and/or speed changes - Google Patents

Abstract

796,864. Measuring fluid flow. NEEDLE, B. L. June 29, 1954 [July 9, 1953; Nov. 5, 1953], Nos. 19142/53 and 30547/53. Class 69 (1). A pitot tube arrangement particularly for sailing vessels or other craft comprises, a tube 12 with orifice 11 arranged to face the relative fluid flow, a second tube 28 with orifice 30 producing, in the position shown in full lines, a dynamic pressure above the static pressure but less than that produced at orifice 11, a pressure gauge 16 indicating the differential pressure between lines 13 and 27 connected to tubes 12 and 28 respectively, and means adjustable to vary this differential pressure to contain movement of liquid in the pressure gauge within reasonable limits. Tubes 12 and 28 are long enough to contain the change in water level so that lines 13 and 27 contain air only; the pressures in these lines are equalized when the rate of flow is zero (i.e. the vessel is at rest) and movement of piston 35 in cylinder 32 may be used to adjust the level of liquid in the sight glass 17 of gauge 16. By bringing this level back to the scale zero (i.e. the level of liquid 18 in the reservoir) the movement of the piston 35 may be used as a measure of speed. Alternatively the movement of liquid in sight glass 17 may be adjusted by rotation of tube 28 so that orifice 30 takes off a different pressure; in the position shown in broken lines it will take off the static pressure only and greater sensitivity will thus be achieved. The length of tubes 12 and 28 may be reduced by inserting in them expansion chambers which allow the necessary increase in pressures in lines 13 and 27 to be obtained with smaller changes in liquid level in these tubes. Tank 25 prevents any liquid from gauge 16 entering line 27.