Patent GB-568578-A (GB)
Abstract: 568,578. Telescopes. ABAX CORPORATION. Feb. 2, 1943, No. 1697. Convention date, Nov. 13, 1941. [Class 97 (i)] [Also in Group XXI] Fire control apparatus for anti-aircraft guns comprises a target-following sight and a compactor sight containing a model or picture of the target, means operated in accordance with data obtained from the targetfollowing sight for setting the axis of the gun ahead and above the line of sight of the compactor by the horizontal and vertical leads to be required when the target and the model appear to be the same size, and separate means for training and elevating the line of sight of the compactor and the axis of the gun so that the gun is properly directed for firing when the line of sight of the compactor is directed towards the target and the latter appears identical in size with the model. In operation the target-follower is directed at and held on the moving target and thereby directs the gun and also the compactor sight approximately towards it. The target therefore appears substantially stationary in the comparator sight thereby facilitating the necessary adjustments to the latter for ensuring that the gun is correctly trained and elevated for firing. Target-following sight. The sight is illustrated diagrammatically in Fig. 1, and comprises a sight rod 103 universally mounted at a point Q, on a slide 107 movable in a radial groove of a horizontal turntable 105, and slidably mounted at P in a supporting block 113. The block is mounted to move in a spherical surface having a point Q, in the axis of the turntable and in a horizontal plane with the point Q, as centre, the mounting means comprising a bent arm 112 rotatably mounted on a rod 111 secured to a shaft 110 passing through the centre of the turntable. The position of the point Q, is controlled by a hand wheel 108 which rotates the turntable and by a foot pedal 109 which varies its radius in the radial groove. Training and elevating movements of the point P about point Q are produced mechanically when either the hand wheel or foot pedal are actuated. This is effected by coupling the wheel and pedal to a power drive 200 which in turn is connected to gears 114, 115 on shafts which train and elevate the point P. The drive is such that the relations between the movements of the point P to those of Q, respond to the following equations :- where - and - are the speeds ot the trammg dt dt and elevating movements given to point P, g the training angle, s the angle of elevation, e the distance QQ1, a the bearing angle of a radius r passing through QQ1, d the contact distance QP, and # a small constant. By this arrangement it can be shown that the point P moves in a plane containing the radius r and a an angular speed which is directly proportional to the distance e and to the sine of the angle between QP and r. The steering wheel which is adjusted to bring radius r parallel to the course of the target thus provides means for controlling the apparent direction of movement of the point on the sky towards which the sight line is divided while the pedal controls the speed of movement of this point. After adjustment therefore, the line of sight automatically follows the target while the line QP follows the path of the target and closely behind it, i.e. to the point A. The power drive 200 is employed for directing the gun and the other sight also to this point A. Fig. 3 (not shown) illustrates the mechanism of the power drive 200 for imparting the necessary movements to the point P when the hand wheel and pedal are actuated. Comparator sight. This sight shown diagrammatically in Fig. 4 comprises a model holder 300 consisting of a carrier plate 302 which is pivoted by adjustable parallel links 320 on a turntable 304. Training movements are imparted to the turntable by a hand wheel 305 and elevating movements to the plate 302 by gear 308 actuated by a hand wheel 307. The model 310 of the target is mounted on a rotatable ring 309 and means are provided for adjusting its position radially. Rotatably mounted on the turntable is a disc 405 carrying a mirror 402 and a rotatably mounted telescope 400. The latter is provided with a lateral aperture for viewing the target A, directly, the model being viewed via the mirror, and suitable adjustment of the lenses is made so that both the target and model are kept in focus. The telescope also has two eye pieces, one concentric with its longitudinal axis, and the other laterally disposed, a mirror being arranged within the telescope so that the target and model can be seen by the operator using the lateral eye-piece. A line from a point M on the turntable and a point N of ring 309, parallel to the links 320 and of the same length as the links, represents the aiming axis with which the gun is parallel. The model is offset from the point N by a horizontal distance S and by a vertical distance n, these distances being suitably chosen to ensure that the gun is correctly positioned at the time of firing. In Figs. 5 and 6 (not shown) means are shown for adjustably mounting a number of models of different sizes in the ring 309, the adjustments being effected by rack-andpinion mechanisms actuated by a computing device. This device, Fig. 9 (not shown), takes into account and computes the various factors which determine the correct line of fire and includes mechanisms coupled to the pedal 109, to the gear wheel 116, Fig. 1, of the sight tube and to the adjusting mechanism for focusing the lenses of the telescope, and additional mechanisms which are adjusted manually according to the type of aeroplane to be fired at and to the particular model chosen. The two sights are mounted, as shown diagrammatically in Fig. 10, on a turntable 602 carrying the gun 600 and various mechanisms are provided between the training and elevating gears of the sights and the gun, and between the various adjustable devices such as the telescope, ring 309, and model adjusting mechanism to ensure that the movements of any one are transmitted only to those other devices necessary to ensure that the gun is correctly trained and elevated at the point of firing. Operation. In operation one operator keeps the sight rod 103 of the target follower constantly on the target. The training and elevating movements thus given to the point P about point Q are transmitted both to the gun and compactor sight which are thus directed to the point A, Fig. 1, behind the target. Second and third operators between them adjust the computer after determining the type of aeroplane and the model to be used, make slight adjustments to the hand wheels 406, 407 to direct the optical axis of the telescope on the actual aeroplane A1, and train and elevate the axis of the line MN and the gun by hand wheels 305, 307a, until the model and target are seen in alignment. The gun is fired when the target and model appear to be identical in size.