Patent GB-930207-A (GB)
Title: Improvements in gunsight having remote lead computing gyroscope
IPC: F41G3/22
Filed: 1960-03-25
Abstract: 930,207. Gun sights. GENERAL ELECTRIC CO. March 25, 1960 [March 30, 1959], No. 10647/60. Class 92. Relates to a gun sight having a lead computing gyroscope 32, Fig. 2, as described in Specification 653,610, provided with an eddy current disc 42 and associated electromagnet 44 designed to apply a torque to the gyroscope which tends to precess it into alignment with the axis of the magnet, the torque being proportional to the magnet flux density which is controlled according to range and ballistic data so that the precession of the gyroscope provides the lead angle. According to the invention the appropriate lead angle is obtained as electrical signals generated by transverse and elevation pickoffs 48, 50 in response to the gyroscope movement and the gun sight optical system is located remotely from the gyroscope, a servo system 52, 54, Fig. 1, being employed to position a movable mirror 74 of the optical system in accordance with the electrical signals from the pickoffs 48, 50. As shown in Fig. 1, # denotes the angle of lead for a target 18 viewed at 12 through a combining glass 26 fixed to casing 20 containing the optical system. This comprises a collimating lens 24, the movable mirror 74 actuated by a drive unit 56, a reticle 76 illuminated from a light source 78 through a condensing lens 80 and reflected from a mirror 82 to present to the movable mirror 74 a reticle which is reflected from the mirror 74 to the combining glass 26. An additional display may be presented from a display source 84 reflected from a mirror 86. The gyroscope is located in a housing 30, Fig. 1, in a gimbal 34 on a shaft 36 rotatable in a bearing 90, Fig. 2, mounted in the pickoff 48 the casing of which is fixed to the housing 30. Shaft 37 fixed to the gimbal 34 is journalled on bearing 98 mounted within a torque motor 64 fixed to the housing 30. Movement of the gyroscope in elevation is about shafts 38 in bearings 39 in the gimbal 34. The shaft 40 is the spin axis of the gyroscope and its projecting end carries the eddy current disc 42 opposite which is the electromagnet 44. The gyroscope receives information from an accelerometer 60 and a precession amplifier 62 which controls the torque motor 64 for providing a torque to the gimbal 34 through the shaft 37. Radar range information is presented to the magnet 44 through a range servo 66 which is combined with ballistic information in the ballistic unit 68. Information on air data is computed in a computer 70 fed from a static pressure tube 72 which information is in turn supplied to the magnet 44. When the gun sight is moved to cause the line of sight to follow the target, the gyroscope spin axis will be displaced by an amount dependent upon the apparent angular velocity of the target and the torque applied by virtue of the interaction of the disc 42 and magnet 44 in accordance with the time of flight of the projectile. The resulting movement of the gyroscope thus computes the correct lead angle and appropriate electrical voltages are fed to the elevation and transverse servos 52, 54 which in turn control the optical drive unit 56 to move the mirror 74 in accordance with the angle of lead. Details of the electrical servomechanisms and the means for moving the mirror 74 are shown in Fig. 2.