Patent GB-1054238-A (GB)
IPC: G01C19/00
Abstract: 1,054,238. Gyroscopic apparatus. AMERICAN CHAIN & CABLE CO. Inc. May 4, 1965 [May 7, 1964], No. 18698/65. Heading G1C. A rate gyro comprises a sealed casing 10 a support shaft cantilevered from a member 15 within the casing, the shaft comprising a fixed portion 19 joined by a flat necked portion 21 to a further portion 22 whose axis defines the spin axis of a rotor 48, the shaft portion 22 flexing about the flat-necked portion 21 in the plane of Fig. 1 to define the precession axis of the gyro. The casing 10 is liquid filled and is provided with a bellows 12 to allow for thermal expansion of the liquid. The rotor is mounted inside a further sealed casing 24 on a sleeve 27 affixed on the shaft portion 22. The rotor 48 rotates on bearing balls 32, 40 and is provided with a hysterisis ring 54 adjacent stator arms 50 and coils 51 of a synchronous rotor spin motor. Electrical connector pins for the motor, as 55, extend from the casing 24 and are connected by flexible pigtail leads to further pins on the casing 10. The precession movements of the casing 24 are damped by the provision of a gap 44 between a surface 46 in the member 15 and a suitably shaped annulus 45 of e. g. nylon, whose thermal expansion is such as to narrow the gap 44 as temperature rises and vice versa to provide a constant damping effect with changes in temperature and thus of viscosity of the liquid in the casing 10. The annulus may also incorporate a torquer for the rotor casing 24 in the form of a magnetically permeable annulus with two permanent magnets fixed thereto in the annulus 45, and a corresponding annular coil in the member 15. The supply to the coil may be controlled by the gyro pick-off (to be described) to torque the rotor back to its equilibrium position, and this electromagnetic system may also be used if desired, to provide damping the annulus 45 then being dispensed with. Further, the feed-back may be such as to prevent movement of the rotor casing 24 altogether, the rate of precession then being measured by the current needed to prevent the precession taking place. Also, by supplying a known current to the annular coil the precession of the gyro may be checked. The interior walls of the casing 10 acts as a stop for the movement of the casing 24. The pick-off arrangement comprises an elongated bar 67 of magnetically permeable material fixed to the shaft portion 22 at right angles to the precession axis. The bar 67 moves in the central plane between two opposed E-shaped cores as 70, with central primary cores, as 74, and with the secondary cores of each E- core of opposite polarity but corresponding to those of the other core. In this way the resultant output of the pick-off is substantially intensive to any movements of the bar 67 at right angles to the precession axis. The positions of the E-cores are adjusted during manufacture and fine adjustment may be effected by moving the position of a magnetically permeable bar 106 by means of screws 105 to produce an accuate null signal when the gyro is its equilibrium position. In an alternative arrangement, the bar 67 is arranged parallel to the precession axis of the gyro with the E-cores again appropriately arranged to be substantially insensitive to any movements at right angles to this axis.