Patent GB-741161-A (GB)
Title: Improvements in or relating to anemometric devices
IPC: G01P3/484
Filed: 1953-05-11
Abstract: 741,161. Electric indicating systems. SOC. NOUVELLE DES ESTABLISSEMENTS BRANDT. May 11, 1953 [May 14, 1952], No. 13036/53. Class 40(1) An anemometer comprises a head oriented automatically to point in the direction of the wind. the head comprising a wind wheel mounted in a hollow cylindrical casing to rotate about the casing having a vane pivoted thereto for automatically rotating the cylindrical casing until its axis is set in the wind direction. The wind wheel produces electric impulses the frequency of which is' measured to indicate the wind speed. A follow-up device controlled, in dependence on the velocity and direction of the wind with respect to a reference direction may be used to control, e.g. aircraft control ,surfaces, ship's rudders, or tightening devices for cables. Anemometer head construction, and automatic orienting; Figs. 1 and 2. The cylindrical casing 18,open at both ends, has an axial shaft 21 rotatably mounted in diametral arms 23, 24 and carrying the helicoidal vanes 20 of the wind wheel. The casing 18 is fixed by struts 19 within a cage 14-15-16, the base 16 of which is mounted on a vertical shaft 9. Pendulously supported by the casing 18 about an axis Z-Z parallel to shaft 21 is a vane 26. Normally, with the casing axis set in the direction of the wind, the vane is vertical. Any variation in the wind direction rocks the vane to engage one or other of contacts 27. 27a which through an associated relay 41, 41a drives a follow-up motor 13. The motor through worm gearing 11, 10 drives the shaft 9 to bring the wind wheel shaft 21 back into the direction of the wind. The shaft 21 embodies a condenser C5 comprising a coaxial ceramic sleeve having inner and outer metallic coatings, the inner coating 52 being earthed through the supporting sleeve 53 and shaft 21, while the outer coating 51 carries a metallic star wheel 48 having an odd number of radial arms so that electrodes 56, 57 mounted diametrally on the insulating arm 24 come opposite an arm of the star wheel successively as the wind wheel rotates Current is led to the follow-up switch contacts 27, 27a and the electrodes by way of brushes and associated slip rings 32-34 on the shaft 9 which also carries two cams 69, 70. The cam 69, Fig. 3. has two semi-circular concentric portions of different diameters and serves to control a contact 75 dependent on the sense of wind direction. The cam 70 is a sine cam controlling a potentiometer 79 linearly in accordance with ,the angle of wind .direction relative to a reference direction P. Measuring wind speed, Figs. 1, 3. The electrode 56 is at a high positive potential derived from a rectifier 66, and by. a sparkdischarge charges the condenser C5 as each arm of the starwheel 48 passes it. The condenser C5 is discharged between successive charges by a spark-discharge to the electrode 57 into a capacitor C1 which discharges gradually through a resistor R1. Hence pulses corresponding to the speed of the starwheel and hence to the windspeed are fed over a coupling condenser C2 to both grids of a thyratron V1 which fires at each pulse and is cut off when a condenser Fig. 3 normally charged in series with a resistors R5, 79 is discharged to a predetermined voltage through the thyratron. The mean charging current of C3 and hence the potential across the potentiometer 79 is thereby proportional to wind-speed which may be indicated on a volt meter 93. The potential derived from the slider 78 ofpotentiometer 79 thus corresponds to the component of the wind speed in the reference direction P. Potentiometric follow-up system. The potential of the potentiometer slider 78 is fed to the grid of a triode V2 and is normally balanced against the potential derived from the motor-driven slider 106 of a potentiometer 105 fed to the grid of a triode V3. If the potential on the grid of V3 exceeds that on the grid of V2 the differential relay r 1 in the anode circuits operates, and through a further relay r 2 energises the servomotor G to run in the follow-up sense. As balance is reached and rl, r2 fall off the motor is energized in the opposite sense, oscillation of the motor about its equilibrium position being prevented by the relay r2 reacting against the relay r1 through a winding 102, so that as equilibrium is approached the relays r1, r2 oscillate with substantially no effect on the motor. With the potentiometer 105 linear its slider position is proportional to the voltage, indicated at 94, of the slider 78, i.e., it corresponds to the component of the wind velocity along the reference direction P. The motor may drive a load H correspondingly. Depending on the sense of the wind relative to the reference direction P, the con.tact 75 is open or closed to release or energize relays r3, r4 which determine whether the positive supply is connected to the upper or lower end of the potentiometer 105. so that the balance position of the slider 10 is above or below the earthed tapping point thereof to indicate the sense of the wind. Modifications.-The wind wheel may alternatively produce pulses at a frequency proportional to speed through a switch, an electromagnetic or a capacitative pick-off, Figs.. 7, 8 (not shown). The protective cage 14-15-16 may be fixed Fig. 5 (not shown) the cylindrical casing 18 being supported therein directly on the shaft 9. The frequency meter may comprise a monostable multivibrator which in response to windwheel impulses, produces constant width pulses, these being integrated in a resistorcapacitor circuit. The inputs to the triodes V2, V3 may be preamplified. By duplication the component 'of the wind velocity perpendicular to the reference direction may also be obtained.