GB1247416A - Electromechanical transducer - Google Patents

Abstract

1,247,416. Measuring angular displacement electrically. BENDIX CORP. May 21, 1969 [May 29, 1968; Aug. 23, 1968], No. 25916/69. Heading G1N. A trandsucer for measuring the angle of attack of an aircraft comprises a rotary differential transformer whose rotor is a cylindrical iron core with an axial flat, attached to a wind vane, and located inside a wound stator, the circuitry including a servomotor which causes the stator to follow angular displacement of the rotor and also drives an output synchro element. As shown Figs. 2, 6 , the stator 16, mounted on bearings 13, has four poles 17 on each of which is wound a primary winding a -d and secondary winding A-D. The rotor 18, mounted on bearings 19 and attached to the wind vane 21, comprises a ferromagnetic cylindrical rod with a flat 20. The primary windings a-d are connected in series and fed with A.C. from a source 41, Fig. 7: the secondary windings A-D are connected in pairs in opposition to give no resultant output signal when the flat 20 is as shown. When the wind vane 21 and rotor 18 are displaced by a change in wind angle the secondary windings produce an output signal which is amplified at 42 to energize motor 39 and drive the stator 16 via gearing G until the output signal is again zero. The angular movement of motor 39 is also used to drive output potentiometers or synchros. In another embodiment the rotor has two diametrically opposite poles and the stator has eight poles of which alternate ones are wound with a coil, the four coils being connected in series and centre tapped to form one branch of a bridge network. Angular displacement of the wind vane and stator produces an unbalanced signal which is used to energize a servomotor to restore bridge balance. As shown, Fig. 2, the rotor of the transducer is attached to a wind vane 21 by two V-shaped crossed groves 23, 24 carrying metal dowels 25, 26 to ensure accurate alignment. The wind vane elements 28, 29 have a triangular cross-section.