Patent GB-127314-A (GB)
Title: Improved Apparatus for Regulating the Aiming of Guns at Aerial Targets.
IPC: F41G5/08
Filed: 1917-04-13
Abstract: 127,314. Soc. Anon des Ateliers BrilliÚ frÞres. Nov. 23, 1916, [Convention date]. Periodic-counter and like speed indicators: speed indicators operating by sighting aerial objects.-Consists of apparatus for determining the corrections to be applied to gun-sights to compensate for the speed of an aerial target. The azimuthal and zenithal components of the angular speed of the target are each measured by a speed indicator having, instead of a pointer, a logarithmic cam which co-operates with a sliding or rotary logarithmic scale to give a direct reading of the product of the angular speed of the target and the time of flight of the projectile, i.e, the desired correction. In a modification. the extent of movement of the scale is a function of the correction, and mechanism is provided for applying the correction direct to the sight. In the construction shown diagrammatically in Fig. 1, a cam co-operates with a slide. The cam is mounted on the axis 0 of the speed indicator so that the angle through which it is turned measures the angular speed of the target. The cam is formed by drawing radii O1, O5, O10 &c. at angles a, #, -y, &c. to the horizontal, and measuring a.long these radii from the circumference of an arbitrary circle o, distances proportional to the logarithms of the corresponding angular speeds of the target. The graduations at the top of the slide are proportional to the logarithms of the times of flight of the projectile, and may be marked with the ranges. When the slide is moved to bring a definite range graduation against a fixed mark and the cam is turned by the speed indicator, the intersection of the cam and the lower edge of the slide gives the product desired. In the modification shown in Fig. 2, the cam 27 operates a pointer 33 and the slide is replaced by a rotary ring E marked outside with the ranges and inside with angles of correction. The ring is set to bring a range opposite a mark F and the reading is given by the pointer at the inner edge of the ring. In a modification of this arrangement, Fig. 3, the ranges are inside the ring which is set to bring the range opposite the pointer. The movement of the ring is then a measure of the logarithm of the required correction. This form is especially useful when i it is desired to correct the sight by the movement of setting the ring by hand. In Fig. 5 the invention is shown applied to a gun sight, only the mechanism for controlling the vertical movements of the gun and sight being shown. The sighting telescope 18 is mounted on the gun cradle so that its total movement is the movement due to the elevating gear of the gun less the adjustment for vertical lead. The shaft a which actuates the speed indicator is driven by differential gear 22, 23, 24 connected to the elevating mechanism 1, 2, 3 of the gun and also to the adjusting mechanism 6, 7, 8 of the sighting telescope so that the resultant velocity of the shaft a measures the angular velocity of the sighting telescope. The speed indicator is of the periodiccounter type comprising two spring-retracted drums f, k held by pawls h, m which are periodically released by cams h<1>, m<1>. The first drum is driven by a pawl e on a rocking bar and has a projection i engaging a similar projection i on the second drum. The shaft o of the second drum carries the logarithmic cam 27. The range ring E is rotated by cam mechanism 38, 38<1> on the sight adjusting gear, two cams being employed so that the ring E is always rotated in the same direction. Suitable multiplying gear, not shown, is interposed between the cams and the ring E. Thus the operation of the hand wheel 6 to set the ring E also adjusts the sight the correct amount.