Patent GB-929762-A (GB)
IPC: G01F1/12
Filed: 1961-03-07
Abstract: 929,762. Rotary liquid flow-meters. GAZ DE FRANCE. March 7, 1961 [March 8, 1960; June 24, 1960], No. 8271/61. Class 110 (2). A fluid flowmeter comprising a turbine interposed in a fluid-flow path and rotatable by the fluid flow therethrough and output means responsive to rotation of the turbine, includes a stationary deflector upstream of the turbine having vanes imparting a rotational velocity to the fluid, sensor means downstream of the turbine sensing any residual rotational velocity component of the fluid and retarding means operable by the sensor means to apply a variable retarding couple to the turbine to maintain said residual rotational velocity component of the fluid substantially zero. As shown in Fig. 1, a stationary deflector unit 2 having helicoidal vanes 2a is positioned in a duct 1 upstream of a turbine 4 and a sensor unit 13 having flat radial vanes 13c downstream of the turbine. The turbine 4 comprises vanes 4c having minimal clearance with the duet and a hub 4a formed with a transverse end wall 4b supporting a shaft 5 which is journalled in bearings 6, 7 carried by the hub 3 of the stationary deflector unit 2. The sensor unit 13 includes a hub 13a formed with a transverse end wall 13b supporting a shaft 14 which is journalled in bearings 15, 16 carried by a faired casing 17 fixed in the duct 1 by a spider 24. The shaft 14 is formed with screw-threads 14a co-operable with a nut member 18 which is prevented from rotating by rods 20 slidingly passing through an end wall 17a of the casing 17. The rods 20 carry an annulus 19 formed with a pair of permanent magnet polepieces 19a co-operable with a ring armature 22 secured to an extension 23 on the deflector unit hub 3. In operation, any residual rotational velocity component in the fluid as it leaves the turbine blades 4c rotates the sensor unit vanes 13c and hence the shaft 14 to axially displace the polepieces 19a towards the armature 22. This increases the induced eddy currents within the non-magnetic end wall 4b of the turbine to increase the retarding torque applied to the turbine until the residual angular velocity is reduced to zero whence the vaned member 13 is brought to rest. At this time the turbine operates under optimum efficiency conditions with the speed of the turbine equal to half the angular velocity of the fluid entering the turbine to give an accurate measure of the fluid flow-rate which is picked-off by means of a worm 8, worm gear 8a and pick-off shaft 9. In a modified construction, the permanent magnet polepieces 19a and the ring armature are replaced by a Roots' blower type of gear pump 30, 31, Fig. 2, driven by the turbine 4<SP>1</SP> and a throttle valve 36 controlling the amount of fluid circulated by the pump and admitted to the pumping chambers through a port 37. The sensor unit 13<SP>1</SP> in this case positions the throttle valve 36 through shaft 141 and gearing 33, 34 to vary the flow through the pump to retard the rotation of the turbine until again the residual rotational velocity component of the fluid leaving the turbine is zero. The turbine shaft 5<SP>1</SP> coaxial with the shaft 4<SP>1</SP> drives through gearing 25, 26 the " pick-off."