Patent GB-159020-A (GB)
Title: Improvements in or relating to sighting apparatus for use with anti aircraft guns
IPC: F41G3/00
Filed: 1919-11-19
Abstract: 159,020. Sinclair, T. C. Nov. 19, 1919. Sights and methods of sighting.-A sighting- apparatus for use with anti-aircraft guns comprises two inclined sighting members movable at the same or different speeds so as to follow a coordinate representation of the horizontal path of the target and indicate the deflexion both in azimuth and in the plane of sight. The sighting members P', Q<1> are universally pivoted on a baseplate A and loosely held, as by spiral springs D<4>, to sliders C<1>, D<1> on parallel rods C, D carried from the base-plate by vertical supports B which are graduated and adjustable by rack-and-pinion gears to adjust the height of the rods in accordance with the height of the target as ascertained by known means. The supports B are adjustable, by screws F geared together through a spindle F<3> with wheel F<2>, across the base-plate in accordance with the presentation angle of the target, and the base-plate is movable about a vertical pivot A on a tripod or other support to bring the rods C, D parallel with the horizontal component of the path of the target, which is effected by the aid of a semi-circular plate R movable about the pivot of the base-plate. This. plate has a mark movable over a graduated semicircle on the base plate for indicating its angular displacement and carries a height-fuze indicator chart comprising curves of equal fuze setting and curves of equal times of flight for varying trajectories, and radial lines at equal angles apart to represent heights. These curves are conveniently marked to read one quarter of the actual times of flight. The sliders C<1>, D' are connected with their guide-rods C, D so that one can be traversed at one quarter the rate of the other, for which purpcse the operating screws C<2>, D<2>, Fig. 6, of the sliders are geared through change-speed gear arranged to give equal drive through wheels J, K and a 1 : 4 drive through wheels J<2>, K<1> according to whether a cone-clutch sleeve L on the screwed end of screw D is engaged, by operation of a milled disk M<1>, with the wheel K or the wheel K<1>. In using the device, the supports B are first adjusted in accordance with the ascertained height of the target, and the scale R is rotated until the radial line corresponding to the ascertained height of the target is opposite the graduation on the base-plate corresponding with the estimated presentation angle, this rotation being to right or left according to whether the target is approaching from right or left. The sliders are now released from their traversing screws by opening the divided nuts G, Fig. 8, through operation of the coned press or screw button G<1>, and are moved along the rods C, D which are adjusted laterally across the base-plate until the target is seen through the telescope on the bar P<1>. The sliders are now engaged by their nuts with the screws, which at this time are geared for equal speed and traversed, to keep the sight bars on the target, by the milled disc 0<1> through a wheel gearing with the wheel J' on the screw C<2>. The scale R is now manipulated to retain the corresponding ascertained weight line on it below a vertical telescopic pointer S on the slider D<1>, and the gear between the screws C<2>, D<2> is changed so that the screw D<2> is traversed at four times the rate for a period equal to one quarter of the ascertained time of flight of the projectile for the ascertained height, the observer keeping the bar P' on the target. At the end of this period the gearing is changed to equal speed, the telescope being kept on the target, and the position of the pointer S is noted with reference to the fuze-setting curves or zones on the chart. At this position the sight bar Q<1> indicates the future line of sight, the vertical deflexion of which can be read off on a quadrant Q<3>, and the lateral' deflexion in azimuth on a quadrant on the baseplate, and in the plane of sight on a quadrant Q<2>.