Patent GB-554752-A (GB)
Title: Sighting apparatus for guns
IPC: F41G5/08
Filed: 1939-06-19
Abstract: 554,752. Calculating-apparatus. SVOBODA, A. June 19, 1939, No. 17842. Convention date, Dec. 31, 1938. [Class 106 (i)] [Also in Group XXI] Relates to apparatus, for predicting the future position of the target after the time of flight of the shell, in which the target is continuously followed by a sight moved by a constant-speed motor through manually-controlled variable-speed mechanisms, computers for determining the firing data being connected with the transmission. According to the invention the transmission includes elements which indicate a series of time derivatives of target co-ordinates and compute the future position of the target in accordance with Taylor's theorem. In the simplified form of apparatus described it is sufficient to proceed only to the second derivatives of the x, y co-ordinates of the target and the z or height co-ordinate may be assumed constant. Fig. 1 shows the general arrangement of the predictor in association with a telescope 12 and mirror sight rod 14 which is moved by slides 11x, 11y giving the x y target co-ordinates. The height z is introduced from a height finder 13z moving a pointer 12z: The analysers 30x, 30y, 30z containing disc and roller variable speed gears controlled by handles 31x, 31y, 31z are driven from a common motor 20 and the derivatives of the target motion x, x<SP>1</SP>, x<SP>11</SP>, y, y<SP>1</SP>, y<SP>11</SP>, &c. emerge as shown at shafts 34x, 34x<SP>1</SP>, 34x<SP>11</SP>, &c. and are passed to computers 50x, 50y, 50z which give as outputs the future co-ordinates x(t+T), y(t+T), &c. where T is the time of flight obtained as explained later. The computers 50x &c. calculate in accordance with Taylor's series the expansion f(t+T=q+q<SP>1</SP>T+¢q<SP>11</SP>T<SP>2</SP> &c., where q=f(t). The future co-ordinates are passed to predicting apparatus 70 whereby the firing data, that is, gun bearing b, gun elevation e, fuse time C, and time of flight T are determined. The general arrangement of the analyser 30x, the computer 50x and the predictor 70 is shown in Fig. 7. The variable-speed drive for the sight slide 11x comprises discs 35 driven in opposite directions by the constant speed motor 20 and a friction roller 39 between the discs which rotate with and moves axially along a shaft 40 under the action of arms 36 turned in opposite directions about shaft 37 by oppositely moving slides 38 actuated by handle 31x. The arrangement is such that the rotation of the roller gives the zero derivatives 32x, 34x for displacing the sight and driving the computor 50x, the sliding of the roller on the shaft 40 gives the first derivative 34x<SP>1</SP> and the movement of slides 38 gives the second derivative 34x<SP>11</SP> these latter derivatives being conveyed to the computer 50x. This computer includes an endless cord 61x passing over fixed pulleys as shown and over movable pulleys on slides carried by bars 53, 54, sliding in accordance with T and T<SP>2</SP> respectively. The slides engage over radial arms 57, 59 rotated in accordance with the derivatives 34x<SP>1</SP>, 34x<SP>11</SP>. The calculated future x co-ordinate enters the predictor 70 at 51x to move bar 74x a similar bar 74y being moved by the future y co-ordinate entering at 51y. These bars adjust a block 75 on a cord 80 which passes over pulleys to actuate a drum 87 carrying curves for gun elevation e and fuse times C, and a cam 96 for giving the time of flight T for use in the computor. The pointers used with the curves are driven in accordance with future z co-ordinate through a rack 124. The cord 80 of the predictor is also connected to the gun bearing indicator g.