Patent GB-726849-A (GB)
Abstract: 726,849. Gyroscopic apparatus. SPERRY CORPORATION. April 1, 1953 [April 14, 1952], No. 9014/53. Class 97 (3). In a gyroscopic instrument having a sensitive element mounted with freedom of angular movement about a normally horizontal axis and controlled in position about that axis by the application of precessing torques under the control of a first gravity-responsive controller mounted so as to tilt on tilt of the sensitive element, there is an auxiliary gravity responsive controller pivoted about an axis parallel to, or co-incident with, the said axis and effective to engage with the sensitive element when the latter tilts about the axis through more than a pre-determined angle. The gyro-vertical shown in Fig. 1 comprises a rotor case 1 pivoted about axis 5 in a gimbal 7 journalled about a perpendicular axis 9 in a craft, and has liquid level switches 15, 17 carried by the rotor case for detecting tilt about the axes 9, 5 respectively and controlling torque motors. Limit stops 31, 32 as described in Specification 625,288 on the gimbal co-operate with spring pins 33 on the gyro to prevent excessive relative tilt about axis 5. Pivoted to the gimbal 7 about axis 9 is a pendulum 35 carrying insulated blocks 38, Fig. 2, which, when the angle between the rotor case and gimbal reaches a certain limit, e.g. 90 degrees, such that the switches 15, 17 may be ineffective to apply signals to the torque motors, may move a spring 43 into contact with a pin 39 on the gimbal to close a circuit through a lamp 45, thus warning the pilot that the instrument readings are at least temporarily faulty, as described in Specification 726,890. When this limit is reached, the pendulum is picked up by the gimbal and exerts a torque about axis 9 to precess the gyro about axis 5 until the limit stops 31, 32 are engaged. Precession then stops and the gimbal breaks contact with the pendulum so that the liquid levels 15, 17 again become effective to erect the gyro in normal manner. Instead of, or in addition to, the warning lamp 45, means may be provided to erect the gyro quickly from extreme tilts. As shown in Fig. 5, when switch 39 is closed by the pendulum 35, a circuit is completed so that a relay 63 opens and a relay 67 closes, the latter completing a holding circuit through a coil 65 and a thermal switch 85. When the limit stops 31, 32 are engaged and the pendulum starts to erect the gimbal, contact 39 opens so that relay 63 closes to heat coil 75 of switch 85. While relay 67 is closed increased voltage is supplied to both torque motors since the switch contact 78 is moved from an intermediate point 79 on transformer 81 to the full supply voltage on the lower contact 83. After a pre-determined time, switch 85 opens and the torquing rate then becomes normal. In another form, the pendulum is pivoted above and parallel to axis 9 on a bracket carried by the gimbal 7 and supporting two pins for contact with the pendulum. The pendulum 35 may be replaced by a liquid or other level and as shown in Fig. 6 may comprise balls 53 freely rolling in a track 55 in a fixed part surrounding axis 9, the gimbal ring having projections 57, 58 extending into the track so as to engage the balls when the relative tilt of the rotor and the gimbal reaches the prescribed limit in either direction.