Patent GB-1352349-A (GB)
Title: Sighting device for target tracking
IPC: F41G3/22
Filed: 1971-04-19
Abstract: 1352349 Automatic control of position BOFORS A B 19 April 1971 [6 March 1970] 22965/71 Heading G3R [Also in Division G1] A sighting device for target tracking and comprising a movable member 8 which is connected to a gyro stabilized platform 12 arranged within a casing 1 and which is rotatable about two mutually perpendicular axes for tracking a target in azimuth and elevation is provided with a locking device which when in operation prevents movement of the member 8 relative to the casing and which, when not in operation, releases the member 8 for positioning relative to the casing by signals from a pair of gyros G s , G n  mounted on the platform 12 and from signal generators S s , S h  manually controlled by a universally mounted lever 16, the locking device being further arranged to provide a smooth change from the locked to the unlocked condition of the member 8 so that tracking of a moving target is unaffected by release of the locking device. As shown, the member 8 which is a mirror pivotally mounted about a horizontal axis on a vertically rotatable gimbal 10 in the casing 1 reflects light from a target to an observer through a telescope 4, 5, 6. The gimbal 10 supports the gyro platform 12 about a horizontal axis and the platform 12 which is arranged to be rotated about horizontal and vertical axes by servomotors M n , M s  is so connected to the mirror 8 by linked rods 14, 15 attached to the platform 12 and mirror 8 respectively that any angular movement of the platform about its horizontal and vertical axes provides a corresponding angular displacement of the sight line 9. The gyros G h , G s  servomotors M s , M h  and signal generators S s , S h  are arranged in similar electric circuits of which only one is illustrated in Fig. 3 comprising amplifiers F 1 , F 2 , F 3  and switches K 1 , K 2  and the components suffixed S. With the switches K 1 , K 2  in the position shown, which corresponds to the locking device being put into operation, any deviation of the mirror 8 from a predetermined position relative to the casing 1 is signalled by a device P s  which actuates the servomotor M s  to reduce the deviation, and hence further signals from the device P s , to zero by rotating the platform 12 accordingly. Simultaneously, the gyro G s  feeds signals, in accordance with the movement of the platform caused by manual movement of the casing, to a signal storing device comprising the amplifier F 3  having negative feedback and a capacitor 18. Upon releasing the locking device the switches K 1 , K 2  are changed from their illustrated positions so that the servomotor M s  is fed via amplifier F 1  with the signal stored just before the locking device is released and with signals from the gyro G s  and the manually actuated signal generator S s  so that a smooth effect in the tracking of a target can be achieved in changing the sighting device from the locked to the unlocked condition. The signal generator P s  is connected to warning lamps 20, 21 which indicate when the limits of a viewing window 3 in the casing 1 are approached by the sight line 9.