Patent GB-1258439-A (GB)
IPC: G01C19/30
Filed: 1969-06-30
Abstract: 1,258,439. Gyroscopic apparatus: measuring angular displacement electrically. AMBAC INDUSTRIES Inc. June 30, 1969, No.32892/69. Headings G1C and G1N. A gyroscope comprises a frame 100, a shaft 54 mounted for rotation in bearings 80, 82 in the frame, a gyro wheel 50 carried on the shaft 54 by means of crossed spring pivots as 58 and 74, 76 and air intermediate ring 72, so that the wheel 50 is driven by the shaft 54 but is mounted so that its spin axis may deviate from the axis of the shaft, the wheel 50 being formed with an annular cavity, pick-off and torquer coils being supported inside the cavity on a fixed non-magnetic cylinder 124, and, ring magnets 142, 144 secured to the wheel 50 inside the cavity for interacting with the pick-off and torquer coils, the wheel 50 being disposed so as to provide a shield of magnetic material between the annular cavity and the frame 100 to minimize extraneous torques on the wheel produced by the magnetic fields of the magnets 142, 144 interacting with the gyroscope frame. The shaft 54 is driven by an electric motor 90 at the end thereof remote from the wheel 50 and a ring .123 on the shaft limits the angular deviation of the wheel. The magnetic shield round the annular cavity in the wheel 50 is provided by the wheel itself and by a cylindrical member 136 secured thereto, and also by a ring nut 148 which secures the ring magnets 142, 144 in place in the wheel 50, the coil supporting cylinder 124, e.g. of phenolic impregnated cloth, extending between the cylinder 136 and nut 148 into the cavity in the wheel 50. An annular polepiece 146 is disposed between the magnets 142, 144 and this is formed with protruding regular steps or teeth, as 146a, disposed opposite similar protruding steps 136a on the cylinder 136. These steps effectively provide polepieces co-operating with the coils on the cylinder 136. Preferably ten such poles are provided disposed with equal separations round the circumference of the wheel 50. The dispositions of the pick-off and torquer coils are shown in Fig .7 which is in the form of a flat plan view of the circumference of the cylinder 124. Dotted line rectangles 280 show the positions of the polepieces provided by the stepped portions 136a, 146a and the locus of these with the axis of the shaft 54 and the spin axis of the wheel 50 aligned is given by a line pp<SP>1</SP>. Four pairs of pick-off coils are disposed in recesses in the cylinder 124 at 90 degrees intervals therearound the coils of each pair being arranged symmetrically with respect to the line PP<SP>1</SP> so that the voltage developed across each coil will be equal with the wheel 50 in its null position. The pick-off coils detect movement about two orthogonal axes at right-angles to the axis of the shaft 54 one axis being defined by the pairs of coils 240, 242 and 250, 252 and the other axis by the pairs 246, 248 and 254, 256. The coils of each pair are connected in series and the pairs of coils defining each axis are also connected in series but in opposite senses so that in the wall position the voltages induced in one pair cancel those induced in the other and on deviation of the gyro spin axis the developed voltage will be of a sign dependent on the direction of the deviation from the wall position. Four torquer coils 260, 262, 264, 266 are also provided and also defining two orthogonal axes the coils 260, 264 for one axis being connected in series in opposite senses suds to import equal but opposite torques on the polepieces as 280 about the axis defined by the other two coils 262, 266.