Patent GB-761521-A (GB)
Title: Improvements in or relating to gyroscopes
IPC: G01C19/44
Filed: 1954-12-07
Abstract: 761,521. Gyroscopic apparatus. GIANNINI & CO., Inc., G. M. Dec. 7, 1954 [Dec. 8, 1953], No. 35462/54. Class 97(3) A gimbal-mounted gyroscope has caging means which operate on de-energization of the rotor driving means to lock the outer gimbal in a given position, and means for moving the outer gimbal to said locking position. It may also have means for erecting the inner gimbal on re-energization, of the rotor driving means which keep the outer gimbal locked until the rotor has reached a speed sufficient to stabilize the outer gimbal, but which release the outer gimbal before the rotor reaches its operating speed, so that, during the latter part of the acceleration of the rotor, the interaction of the accelerating rotor and the gimbals erects the inner gimbal. As shown in Fig. 1, the rotor 50 is mounted in gimbals 40, 20 in a cylindrical casing 10, the range of movement of the gimbal 40 being restricted to just less than 180 degrees by stops 43, 44 on the outer and inner gimbals respectively. Erecting means of conventional character may be provided to keep the rotor axis vertical. A caging ring 60 is mounted on the outer gimbal 20. A solenoid 66 mounted in casing 10 has an armature 65 with a caging pin 64 which is urged by spring action into one of a series of holes 62 in the caging ring when the solenoid is de-energized To start the gyroscope, a. switch 71, Fig. 2, is closed, applying power to an electric rotor driving motor 52. Current also flows through the normally closed contacts 79 of a relay 80 to a heating resistor 78 mounted in proximity to a bimetallic strip 77. The arrangement is so designed that the strip 77 closes contacts 76 after a time sufficient to allow the rotor to reach a speed less than its running speed but sufficient to stabilize the gimbal 20, e.g., between a tenth and a half of its running speed. Closing of contacts 76 completes a circuit through coil 69 of solenoid 66 to withdraw the caging pin 64. freeing gimbal 20. At the same time coil 82 of relay 80 is energized, opening contacts 79 to iiiterrupt the circuit through resistor 78, and closing contacts 81 to complete a holding circuit. The acceleration of the rotor in the remainder of its run-up period, causes rapid erection of the inner ring 40 two a point where the normal erection means 74 are able to bring the rotor axis quickly to the vertical. When the gyroscope is switched off, the caging pin 64 is urged towards 'the caging ring and enters a hole 62 if one is suitably positioned; if not the caging ring 60 will rotate with gimbal 20 as the rotor decelerates until the pin engages a hole 62. To faciltate this action, pin 64 has a rounded or pointed end and the holes 62 are countersunk. A semi-circular strip 85 is mounted on gimbal 20 and has a central dot (not shown) which is visible in a window 86 in casing 10 whengimbal 20 is substantially erected. Lines on strip 85 extend through an angle such that, if a part of a line is visible in window, 86, the tilt of gimbal 20 is within a range in which it can speedily be 'erected by the normal erecting means. In a modification, Fig. 3, the gimbals 20, 40 are erected by torque motors 94, 96 controlled by mecury switches 90, 92 mounted on the gimbals and energized in known manner from the three-phase supply to the rottor driving motor. Movement of gimbal 40 is limited by a bracket 44b mounted thereon, having lugs 44a which engage a rubber stop 43 on gimbal 20. A caging ring 100 fixed to gimbal 20 has an arcuate groove 103 ( see also Fig. 4B) terminating in holes 104. A solenoid 66 mounted on the casing has aspring-loaded armature 65 carrying a pin 111 protruding from a surrounding insulating bushing 112. When the gyroscope is caged by the bushing 112 engaging one of the holes 104, and the motor is started, the relay 66 is actuated to free gimbal 20 after a time delay, and the rotor is erected, in a manner similar to that described for the arrangement shown in Figs. 1 and 2. When the power supply is switched off, solenoid 66 is de-energized. The busing 112 may enter a hole 104 causing immediate caging, but in general the pin 11 will bear on the surface of ring 100, as shown in Fig. 4B. In this position a contact 116 on armature 65 bears against a fixedly mounted spring contact 118, completing a circuit to a signal lamp indicating that caging is not complete. The deceleration of the rotor may cause gimbal 20 to turn until bushing 112 enters one of the holes 104, when the armature 65 moves forward and the signal lamp goes out and the circuit is broken. If, after a certain time, the signal lamp is still alight, showing that caging has not been effected as described above, a caging switch is operated. This applies current to one end of a relay coil,'the other end of which is connected to pin 111, and thence through caging ring 100 to earth. Actuation of the relay connects to the torque motor 96 controlling the outer ring 20 to a source of voltage about ten times higher than the voltage applied to the torque motor in normal operation. This turns gimbal 20 rapidly until caging is effected, when the earth return through pin 111 is broken and the torque motor is de-energized. At the same time the signal lamp goes out. In a further modification, the caging relay is acuated as soon as power is switched off the pin 111 contacts ring 100, with consequent immediate energization of the torque motor to effect caging.