Patent GB-422116-A (GB)
Title: Improvements in method and means for controlling compasses
IPC: G01C17/00
Filed: 1933-06-02
Abstract: 422,116. Magnetic compasses; gyroscopic apparatus. BENDIX AVIATION CORPORATION, 105, West Adams Street, Chicago, U.S.A. June 2, 1933, No. 16010. Convention date, June 6, 1932. [Classes 97 (ii) and 97 (iii)] The indicating element of a magnetic compass is subjected during turning of the supporting craft or periodically to the control of a non- magnetic directional element, for example a directional gyroscope or a constrained gyroscope responsive to rate of turning. In the form shown in Fig. 1, the precession of a gyroscope with two degrees of freedom is used to control means for gripping the compass card and means for turning it to compensate for deviations induced by turning of the supporting craft. The hub 13 of the compass card 1 carries the pivot pin 12 and a depending globular skirt 40 adapted to be gripped by jaws 41 on bellcrank levers 42 which are pivoted at 47 on a pinion 43 freely mounted on the pivot supporting pillar 11. The jaws 41, which are normally held out of the gripping position by springs 49, may be caused to grip the skirt by a solenoid 55. The pinion 43 is geared through pinions 81, 80, 77, 76, 73 and 72 to a shaft 70 carrying two opposed ratchet wheels. The co-operating pawls 89, 90 are carried by arms 87, 88 freely mounted on the shaft 70 and spring urged so that pins 92 maintain the pawls in inoperative position. The pawl and ratchet mechanism are adapted to be actuated by an A-frame 96 which is continuously reciprocated by the motor 95 but is normally out of contact with the pawl arms 87, 88. The gyro rotor 25 driven by an air jet 31 is mounted about a transverse axis 26 in a ring 27 pivoting about a longitudinal axis 28, 29 in the casing 30. A semicircular plate 35 fixed to the ring 27 is connected to dash-pot mechanism 111, to centraliz. ing means consisting of coil spring 37 and leaf spring 36, and to the A-frame 96 by a link 105. When the gyro 25 precesses upon turning of the supporting craft, the spring 36 is flexed and contacts with a post 66 closing the circuit of the solenoid 55 through battery 64 and leads 60, 61, so that the compass card is gripped and simultaneously the A-frame is moved by the link 105 and drives one or other of the pawl arms 87, 88 with strokes proportional to the amount of the precession. The pinion 43 and card 1 are therefore rotated by an amount which compensates for turning of the craft. In the form shown in Fig. 5, the compass card 1 is intermittently clutch to a gyro with three degrees of freedom. The rotor 126 driven by jet 142, is mounted about a horizontal axis in the ring 127, pivoting about an axis 128, 129 in a ring 130, pivoting in turn in a ring 131, which is mounted for rotation about a vertical axis in bearings 133, 134. The vertical ring 131 has a depending sleeve 156, enclosing a plunger 155 with a conical clutching member 150 adapted to engage a hemispherical member 151 on the card 1. The plunger 155 is normally maintained raised by a spring 171 but may be lowered into engaging position by links 157, 163 when a piston 164 is pushed by an air jet 176 fed by a pipe 175 along a cylinder 165 carried by a platform 161. fixed to the ring 131. An arm 181 pivoted at 182 and carrying a friction roller 184 riding on the surface of plate 136 normally masks the jet 176 but is drawn to one side upon turning of the craft and allows the plunger to be lowered into engaging position. The card 1 is accordingly maintained steady during turning by connection with the gyro 126. In a modification in which the gyro is clutched to the compass card periodically and independently of turning of the craft the arm 181 is dispensed with and the supply of air to the jet 176 is controlled by a valve operated by timing mechanism. In a further modification the plunger 155 may be operated by a solenoid which is energized under the control of (1) co-operating contacts on the ring 131 and plate 136 or (2) an auxiliary gyro with two degrees of freedom or the usual gyroscopic turn indicator, or (3) a time controlled switch.