Patent GB-191401361-A (GB)
Title: Improvements in Sighting and Firing Apparatus in connection therewith for Discharging Projectiles from Aeroplanes, Dirigibles, Balloons, and the like.
Filed: 1914-01-17
Abstract: 1361. Soc. Anon. l'Helice IntÚgrale, Anciens Etablissements L. ChauviÞre- Jan. 18, 1913, [Convention date]. Void [Published under Section 91 of the Act]. Angle-measuring instruments.-Relates to apparatus for determining the instant at which to release a projectile or bomb from aircraft in order to hit a stationary or movable target, the altitude and velocity of the aeroplane &c. and the direction and speed of the wind being allowed for. According to the invention, the image of the target is obtained on the ground-glass screen of a camera obscura carried by the aeroplane. For a constant speed V of the aeroplane, a sighting point p on the screen is assumed, and the objective of the camera is set in the correct relative position, according to the altitude, by means of a graduated dial. For variable speeds of the aeroplane a pointer indicating the required position p on the screen is set automatically according to the altitude and the actual speed of the aeroplane. To allow for wind the camera is so mounted that it always remains horizontal and it is rotatable according to the wind direction and speed, the rotation controlling a sighting-bar which indicates to the pilot the course to be steered. As illustrated, a camera A, Fig. 4, is arranged on the aeroplane; the image b<1> of a target B will travel over the screen b with a velocity depending upon the aeroplane speed V and also upon the altitude. Assuming that the aeroplane travels at a speed V, and that the projectile is released at a point O, Fig. 5, the trajectory T of the projectile is plotted, and the points b, b<1>, b<2> .. b<n> corresponding to altitudes H, H<1>, H<2> .. H<n> are joined to 0 thus determining firing angles #, #<1>, #<2> .. #<n> to be used in determining the instant at which to release the projectile. If the point p, Fig. 6, on the screen is the required position of the image at the instant of discharge, lines pa, pa<1>, pa<2> .. pa<n> drawn, respectively parallel to the lines Ob, Ob<1>, Ob<2> .. Ob<n> will give the positions, corresponding to various altitudes, that the objective a, Fig. 4, of the camera must occupy at that instant in order that the projectile may hit the target. The objective a is adjusted to the various positions a, a<1>, a<2> .. a<n> for the various altitudes H, H<1>, H<2> .. H<n> by means of a board d, Fig. 3, sliding in grooves d<1> and actuated by means of racks d<2>, pinions d<3> and a disk D<1> which is graduated for altitudes and co-operates with an index e. The actual velocity of the aircraft, due principally to velocity and direction of wind, will usually differ from the assumed speed V, and may vary between zero and 2V, taking V as the mean velocity. Accordingly the trajectory of the projectile may vary from the vertical OH<n>, Fig. 5, to the trajectory OB<n>, and consequently the required position of n on the screen for a given height H<n> may vary from the position O<1>, Fig. 6, vertically above a<n> to the position O<2> obtained by drawing from a<n> a line parallel to OB<n>. The different positions of p between O<1> and O<2> are automatically determined as follows: a wire c, Fig. 2, passing round pulleys c<1>, c<2>, c<3>, c<4>, once round a pulley k, and in front of the screen is driven by means of a roller j on the shaft k<1> and a disk i driven by gearing i<1>, Fig. 3, on a shaft g<2> which is driven by a roller g from a uniformly rotating clockwork-driven disk h. The position of the roller g on the disk h, and consequently the velocity of the disk i corresponds to the altitude of the aeroplane and is determined by means of a slotted cam-plate f attached to the board d, and a pin g' engaging the slot. A second slotted cam-plate f<1> attached to the board d, Figs. 2 and 3, operates a rod m<1> and sets the pin l<2> in such a position in the slot l<1> in a toothed sector l that a movement of the pointer p, carried by a rack n engaging the sector l, over that portion of p<o> p<n>, Fig. 6, corresponding to zero and maximum speeds of the aeroplane and image at the given altitude will move the roller j over the length j<1> j<2>, Fig. 2, and thus impart to the wire c a velocity corresponding to the velocity of the image at the given height. In operation, the altitude of the aeroplane is first determined. The disk D', Fig. 3, is then set for this altitude; this operation sets the objective a, for the determined altitude, and also sets the roller g on the disk h, the pin l<2> in the slot l<1>, and the roller j on the disk i such that the velocity of the wire c corresponds to the speed of the image for that altitude and for the mean speed V of the aeroplane. If it is now found that the actual speed of the image agrees with that of the wire c, the aeroplane has the mean speed V and the position of the pointer p agrees with that already assumed on the screen for this constant speed V. If, however, the speeds of the wire and image are different, that of the wire is increased or diminished bv moving the rack n by hand. This movement shifts the roller j on the disk i and also moves the pointer p and, when the speeds of wire and image are alike, the pointer p occupies the correct position for the actual aeroplane velocity at the determined height. In order to allow for wind, the pilot steers by means of a vertical bar at P, Fig. 7, and a movable cross-wire which is normally at P<1> and is displaceable by the operator who is observing the path of the image across the camera screen. The camera is mounted in cardan joints q<1>, q<2>, q<3>, q<4>. The joint c<4> is movable about a vertical axis t, and the joint c<3> is connected by a block q<5> to a rack r operated in a guide r<1> by means of a crank r<2> and pinion S. A cable u<1> is wound on a pulley u on the shaft s<1> and connected to the cross-wire device l<1> and a spring v and the parts are so designed that any movement of the central line e<1> of the screen through an angle # to the direction e<2> produces a corresponding movement of the point P<1> to P<2> so that the angle P<1>, P, P<2> is #. In a modified form, the frame carrying the camera is operated by worm-gearing and the point P<1> operated by jointed rods. In operation, if the path of the image on the screen is found to be along any line other than the line e<1>, for example along e<2>, the crank s<2> is rotated to displace the cross-wire P<1>. The pilot then has to turn the aeroplane through the angle necessary to bring the target again in line with P, P<2>, and both operations are repeated until the path of the image does coincide with the line e', the aeroplane then being correctly placed to drop a projectile on the target when the image coincides with the fiducial mark on the screen.