Patent GB-177787-A (GB)
Abstract: 177,787. Pittoni, L. March 29, 1921, [Convention date]. Sights and methods of sighting. -A method of and apparatus for computing the azimuth angle, the quadrant angle of elevation, and the fuse-setting necessary for firing an anti-aircraft gun on the assumption that the aircraft is moving at a constant height consists (1) in measuring continuously the azimuth angle and the angle of sight, and superimposing upon these mechanically the variations which they undergo during the time of flight of the projectile plus a constant time allowed for fuse-setting and loading prior to firing, the time of flight adopted being that of the projectile corresponding to the position of the aircraft at the moment when the determination of the variations is commenced; (2) in employing the angle of sight and the known height of the aircraft to determine the fuse-setting; and (3) in superimposing upon the computed angle of sight the tangent angle of elevation corresponding to this angle of sight and the computed fuse-setting. The computed data may be displayed on indicators, but it is stated that the apparatus whereby the gun-laying data are calculated may be employed to actuate distant-control gears which lay the guns automatically. In the form shown, the fusesetting is computed by a device comprising a drum 1, Fig. 1, which turns on a fixed axle 2, and may be coupled to one or other of two toothed wheels 9, 10, riding loosely round the axle 2, by means of clutches 7, 8 controlled by a handle 17, Fig. 3. The drum 1 is rigid with a toothed wheel 41 driving the outer wheel 39 of a differential gear, the inner wheel 43 of which is mounted on - a sleeve 44 which turns on a fixed shaft 35 and carries two wheels 45, 46 meshing respectively with the wheels 9, 10; the planet pinions 38 are adapted to drive a drum 36 turning on the fixed axle 35. The drum 36, through a differential gear, causes an adjacent drum 47, Fig. 3, to turn at one-quarter its speed; the drum 1 in the same manner drives an adjacent drum. On the drum 1 are traced curves of equal time of flight as a function of angle of sight peripherally and height of aircraft axially; on the drum 36 are traced in the same manner curves of equal fuse-setting. The curves on the drums 1 and 36 are traced only for angles of sight up to 30‹; similar curves are traced on the adjacent drums 47 for all angles of sight. The drum 1 is rotated continuously through an angle equal to the angle of sight of the aircraft, for example by mounting the apparatus on a pedestal, Fig. 3, so that it may be turned in azimuth by a hand-wheel 60, and providing a sighting telescope 56, the elevating hand-wheel 57 of which is geared to the drum. The rotation of the drum 1, through the wheel 41 causes the drum 36 to rotate continuously at the same rate, the wheels 9, 10 being locked, as inhereafter described. Pointers 51, slidable along a screw 52 rotatable by a hand-wheel 53, may be displaced along the drums 1 and 36 and their adjacent drums 47 in accordance with the known height of the aircraft, and indicate at any instant the time of flight and fuse-setting corresponding to the height and angle of sight of the aircraft at that instant. The determination of the variation of the fuse-setting, from the instant of reading it on the instrument to that of burst of the shell, to compensate for the movement of the aircraft during this period, may be made at an accelerated rate by moving the lever 17 to the left, so as to couple the wheel 9 to the drum 1, and by leaving the wheel so coupled for a period equal to one half the sum of the time of flight indicated on the drum 1 at the instant of coupling plus the constant. When the wheel 9 is coupled, the drum 36 is rotated at twice the rate produced by the wheel 41 alone, so that the angle of rotation superimposed upon this drum is proportional to twice the change in angle of sight during the actual time the wheel is coupled. The pointers 51 will then exhibit on the drums 36 and 47 the corrected fuse-setting. If the time of flight is unduly long, the wheel 10 is coupled instead of the wheel 9; the drum 36 then turns at three times the rate produced by the wheel 41 alone, and the wheel 10 is left coupled for one third the time of flight indicated on the drum 1 plus the constant. The wheels 9, 10 may be braked by a device 18, 19, 22, 26 when the lever 17 is moved to unclutch the coupled wheel, whereafter the drums 1, 36 again rotate in unison but with the drum 36 displaced by the amount previously imparted thereto. The corrected fuse-setting can therefore be continuously called out by an operator watching the drums 36, 47. When the handle 17 is restored to the mid-position, springs 30, 31 return the wheels 9, 10 to the position for zero correction, and a spring pin 32 enters a hole in the wheel 10 and locks the wheels in this position. A stop watch 55 controlled by the movements of the lever 17 is provided. In the apparatus for determining the azimuth angle, a shaft corresponding to the drum 1 turns as a function of the azimuth angle, and communicates through gearing similar to that shown in Fig. 1, with a shaft corresponding to the drum 36, the corrected azimuth angle being displayed on an indicator mounted on the second shaft. In the apparatus for determining the quadrant elevation, a shaft 70, Fig. 7, turns as a function of the angle of sight, and drives a second shaft 74 through gearing similar to that shown in Fig. 1. The shaft 74, which thus turns as a function of the corrected angle of sight, carries the outer wheel 77 of a second differential gear, the pinions 78 of which drive a hollow shaft 79. The wheel 77 drives a screw 81 carrying a pointer 82, which is therefore displaced in accordance with the angle of sight along a drum 83 geared to the centre wheel 86 of the differential gear, and carrying curves of equal fuse-setting traced as a function of the angle of sight axially and tangent elevation peripherally. The drum is turned by a handwheel 85 to maintain the pointer 82 on the curve corresponding to the fuse-setting determined by the pointer 51, Fig. 3, and thus superimposes on the angle of sight transmitted to the shaft 79 by the wheel 77 the tangent elevation corresponding to that angle cf sight and the fuse-setting. The resultant quadrant elevation is exhibited on an indicator 88. The apparatus for the azimuth and elevation corrections mav both be controlled by the same handle, such as 17, and may be driven from the hand-wheels 60, 57, Fig. 3. The indicators showing the corrected azimuth angle and quadrant elevation may be replaced by transmitters actuating distant control gearing for automatically laying the guns.