Patent GB-732975-A (GB)
Title: Improvements in or relating to gyroscopic apparatus
Inventor: SEDGFIELD HUGH BROUGHAM
IPC: G01C19/38
Filed: 1952-05-30
Abstract: 732,975. Gyroscopes. SPERRY GYROSCOPE CO., Ltd. May 15, 1953. [May 30, 1952], No. 13846/52. Class 97 (3). [Also in Group XXXVIII] Gyroscopic apparatus of the kind comprising a rotor mounted for spinning about a first axis that intersects a second axis, about which a rotor-driving shaft is mounted for spinning in a support, at a pivot point on the second axis about which point the rotor, when spinning about the first axis, is free to pivot through a limited angle in any plane through the first axis from a position in which the two axes are in line, is characterized in that the rotor is driven from the driving shaft through one or more flexible connecting members connected on the one hand to the driving shaft and on the other hand to the rotor, which member (or each of which members), by undergoing oscillating flexure during a rotation of the shaft and the rotor, permits the shaft and the rotor to rotate about their spin axes when these axes are inclined to each other. As shown in Fig. 1, the gyroscope has a primary rotor 1 and a secondary rotor 2 mounted for rotation about a spin axis A, B in ball bearings 4, 5 in a rotor case 3. Rotor 2 is about five times as heavy as rotor 1. The case 3 comprises two hemispheres 8, 9 with end plates 11, 12, all bolted together with rubber sealing rings 10, 13, 14, and the case is evacuated after sealing. Rotor 2 is driven by an electric motor comprising a stator 6 on the rotor case and a squirrelcage rotor 7 fixed to rotor 2. The rotor 1 is suspended from rotor 2 by means of an axial wire 16 and a spider 17, 18 joined by a copper bead 22 on to which the two parts 28, 29 of the rotor 1 are press-fitted. The wires 16 and the legs of the spider pass through holes in rotor 1 to allow a small degree of angular movement. The wire and spider are preferably just not in tension : for this reason they are clamped tight with the whole assembly below operating temperature. Rotor 1 is driven from rotor 2 by a flexible connection comprising a ligament 32, Fig. 2, clamped at its ends at 33, 34 to rotor 2. The ligament passes through a hole in rotor 1 and is clamped at its centre by a clamp 35 on the rotor. A second hole 36 serves to balance the rotor. A follow-up arrangement is provided to bring the axis of rotor 2 into line with that of rotor 1. Four pick-offs, of which two are shown at 38, 40, are disposed symmetrically about the axis of rotor 1, and are mounted on a sleeve 46 slidable on a sleeve 49 on casing 3. Each pick-off comprises a coil with pole-pieces overlapping a ring 37 of magnetic material carried by the rotor 1. A screw 53 acts on a cam pivoted at 52 to slide sleeve 46 along sleeve 49 against action of a spring 50, to adjust the amount of overlap between the pole-pieces and the ring. The casing may be mounted in gimbals with torque motors which are controlled by the pick-offs, when the gyroscope is used as a directional gyro. When it is used as a gyro-magnetic compass, the torque motors also receive signals from an arrangement such as a flux valve, using the circuit shown in Fig. 4. In this circuit, coils 143, 143<SP>1</SP> of oppositelypositioned pick-offs are connected across an A.C. source through resistors 181, 190 and rectifiers 180, 189. The action of the rectifier produces a D.C. component in the current through the pick-offs, exerting forces on ring 37 which are, however, equal and in balance. The A.C. components of the flux at the pickoffs are also in balance and in phase. Two resistors 182, 183 of equal value are connected across the A.C. supply, and their common ends are connected through a resistor 184 and the primary winding of a transformer 185 to the junction of coils 143, 143<SP>1</SP>. If the rotor 1 tilts with respect to the casing in the plane of the pick-offs, their overlap with the ring 37 will change and the inductance of one coil will be increased and that of the other decreased. Thus the A.C. potential at the junction of the coils differs from that at the junction of resistors 182, 183, and current flows in the primary of transformer 185. The secondary voltage is amplified and applied to a torque motor to precess rotor 2 into alignment with rotor 1. A D.C. potential applied through terminals 186, 187 across resistor 184 causes D.C. to flow through the coils in one case in the same direction as the D.C. component referred to above, and in the other case in the opposite direction. This results in a greater flux in one pick-off, giving rise to a precessional torque on rotor 1. The D.C. signal may be applied to one pair of coils from a flux valve to keep the gyro axis on a constant magnetic direction. The other pair of coils may receive a signal from a gravity-responsive device, to keep the gyro axis horizontal. Other signals may be generated to compensate for the effects of the mechanical constraint of wire 16 and the legs of spider 17, 18, and of unbalance of rotor 1. Specifications 719,957 and 733,058 are referred to.