Patent GB-365731-A (GB)
Title: Improvements in or relating to sighting and alignment mechanism and steering means for craft such as bombing aeroplanes
IPC: F41G3/24
Filed: 1930-12-04
Abstract: 365,731. Steering aeroplanes bomb sights. HILLIER, A., 15, Victoria Street, London.-(Sperry Gyroscope Co., Inc. ; Manhattan Bridge Plaza, Brooklyn, New York, U.S.A.) Dec. 4, 1930, No. 36660. [Class 4.] Adjustment of the bomb sight of an aeroplane is utilized for controlling the rudder to direct the course of the machine towards the target after which it may be maintained on that course by gyroscopic apparatus. The sighting system comprises a telescope 10, a prism 23 stabilized by a gyroscope 12 having a vertical spinning axis, a lens 22, erecting prism 21, and a reflecting prism 20. The prism 20 can be turned about transverse and longitudinal axes by movements of a lever H pivotally mounted on a longitudinal shaft 30 which carries the prism 20 in a fork 32. The whole of this apparatus is mounted on a platform P which can be turned about a vertical axis. To prevent rotation of the image as the prism 20 is turned about the longitudinal axis the prism 21 is turned at half the rate by gearing 25 .. 28. As the lever H is tilted laterally to cause the prism 20 to follow the target the rotation of the shaft 30 is transmitted through gearing 46, 47, 48 and a differential gear D to a sector 40 having two insulated contact strips 41, 42 co-operating with a contact 44 whereby a reversible motor 50 is energized to move a rudder R in the appropriate direction. The sector 40 is caused to follow up the displacement by gearing 51, 52, 53 and a differential gear D<1>. To prevent the rudder from being adjusted as the bomber moves the lever H to follow the target as the machine rolls a correction is applied to the member 55 of the differential D by connections to a member 60 which is maintained in a vertical plane by a projection 61 on the gyroscope 12. When the machine is headed towards the target, i.e. when the lever H and sector 40 are vertical, a switch 70 is closed and an electromagnet 100 closes a switch 101 to energize an electromagnet 71 to remove a lock 72 from the axis of an azimuth gyroscope G which controls a motor 75 through contact segments 77, 78 and a contact 76, for rotating the platform P through gearing 73, 74, a platform P<1>, carrying the contact 76, being caused to follow up the displacement by gearing 79, 80 and a differential gear D<11>. Such movements are brought about as the bomber continues to move the lever H to follow the apparent movement of the target due to drift, the platform P being turned in a direction equal and opposite to the machine until the ground course is directed towards the target. The winding of the magnet 100 is in circuit with contacts 103, 104 which are only closed when the sector 40 is in mid position. The gyroscope G and motor 75 may be mounted on the platform P which is then turned by a pinion engaging a fixed gear ring. As soon as the ground course is directed towards the target a lever 90 may be moved to switch over the control of the motor 50 from the sector 40 to the gyroscope G, a switch S effecting the necessary change in the electric circuits and a clutch 91, 92 connecting up a transmission from the motor spindle to the differential D<11> to act as a follow-up device whereby the machine is maintained on its course automatically. A handle 1 enables the platform P to be manually adjusted. To compensate for drift on the falling bomb, the prism 20 may be automatically tilted an additional amount proportional to the amount of turn of the platform P by gearing turned by movement of the platform P and acting upon one element of a differential gear inserted between the lever H and the pinion 25. An arbitrary tilt may also be given to the prism to enable an object offset by a known amount from an obscured target to be sighted.