Patent GB-684667-A (GB)
Title: Improvements in or relating to lead computing devices
IPC: F41G5/00
Filed: 1943-02-09
Abstract: 684,667. Gyroscopic apparatus. STEVENS, A. H. (Massachusetts Institute of Technology). Feb. 9, 1943, No. 2180/43. Class 97 (iii). [Also in Group XXI] A device for computing the angle of lead to be imparted to a gun with respect to the sight, comprises a gyroscope mounted on the gun or proportional to the rate-of-turn of the gun or sight about an axis, means being provided to damp the the precessional movements of the gyroscope. In the construction shown diagrammatically in Fig. 1 the sighting device comprises two gyroscopes 20, 21 mounted in frames 40 and rotating respectively about vertical and horizontal axes 23, 26. The trunnion 22<SP>1</SP> of the frame of gyroscope 20 carries an arm 28 which is connected by links as shown to an unsilvered mirror 6 through which the target is viewed, the movements of the mirror being damped by providing on its shaft 7 a slotted disc which is partly immersed in oil in a housing 171. An image 9<SP>1</SP> of an adjustable reticle 9 is projected on the mirror 6 by a mirror 10 which is linked to the trunnion 25<SP>1</SP> of the frame of gyroscope 21 and which is provided with damping means in a housing 17. The optical system includes a lamp 15 and lens 16, and the adjusting means for the reticle consists of two set screws 66, 67 which are adjusted to introduce spotting corrections. As shown in Fig. 2 damping of the precessional movements is effected by containers 48 partly filled with oil or gum, in which containers move disc-like members 49, with rims 50 secured to the rotor frame. Electrical heating coils 51, 52 maintain the temperature of the fluid constant. The rear trunnions of each gyroscope are each spring centralized by four symmetrically arranged leaf springs 33, Fig. 3, which are clamped to ears 42 extending from the rear of the gyroscope housing 41 and to which are secured radial wires 34, 35 passing through a clamp 36 secured to the trunnion. The leaf springs, the tensions of which may be adjusted, thus offer a resistance to the precession of the gyroscopes. A further resistance to precession, which is adjustable for introducing the time-offlight factor, consists of two pairs of leaf springs 56, 57 between each pair of which is disposed a knife edge 55 carried by the arms of a member 53 secured to the rear trunnion of the frames 40. The effective resistance offered by the springs is varied by a graduated control knob 62 which through gearing 63, 61 and rack- and-pinion mechanism adjusts the radial positions of the springs. The forward trunnion of each frame is fitted with a frame 46, which is clamped to a wire 44 stretched between arms 45<SP>1</SP> carried by the housing 41. The wire thus acts as a pivotal support, prevents axial shift of the rotor, and opposes precession. To allow for super-elevation corrections a torque is applied to the frame 40 of gyroscope 20 by a weight 65 which is screw-threaded on an arm extending radially from its forward trunnion 22. In cases where the gun is mounted on a ship a similar weight 65<SP>1</SP> is provided on a vertical arm on the forward trunnion of the gyroscope 21, thus providing a torque opposing precession when the normally vertical axis of the gun is disturbed by rolling or pitching. The gyroscopes are rotated by air supplied by nozzles 68, 69, the temperature of the air being controlled by a thermostatically con. trolled air heater 71. Figs. 7 and 8 (not shown), show respectively mechanical and electric solenoid means for imparting a torque to the gyroscopes for taking care of the effects of cross winds. Specification 684,668 is referred to.