Patent GB-328001-A (GB)
Title: Improvements in or relating to means for ascertaining data for use in anti-aircraft gunnery
IPC: F41G5/08
Filed: 1928-10-16
Abstract: 328,001. Sinclair, T. C. Oct. 16, 1928. Sights and methods of sighting. - In anti-aircraft gunnery apparatus, means for continuously predicting the necessary data for future positions of the target while the latter is being followed by a sighting device comprise a course member, representing the present position and course of the target, which is set in accordance with target speed and co-operates with a chart showing times of flight of projectile for various heights of target, an indication of the point in space through which the target will pass after a time interval equal to the time of flight of the projectile being given when there is coincidence between the same time readings on the course member and the chart. The apparatus is mounted within cylindrical casings, the casing A, Figs. 4 and 5, being fixedly carried by a stand and the casing A<3>, carrying the sighting telescope B, being rotatable in azimuth round the central axis by operating a hand-wheel A<14> in following the target in azimuth. The target is followed in elevation by operating a hand-wheel B<5> thereby rotating a spindle B<3> which is geared, as shown in Fig. 10, to a rack C<6> on a carriage C sliding on radial guides C<1> in the casing A<3>, as shown in detail in Fig. 11. The carriage freely supports on a vertical pivot bearing C<5> a course member D, the position of the axis of the bearing from the central axis of the instrument being always proportional to the present ground range of the target since it is adjusted from the hand-wheel B<5>. Arranged below the carriage is a platform A<9> which is kept fixed by gearing during azimuthal rotations of the casing A<3>, and a caster C<8> on the carriage engages this platform and thereby maintains the course member D in a direction corresponding to the course of the target. The course member is in the form of a drum marked circumferentially with various target speeds and longitudinally with seconds of movement at these speeds with the zero at the axis of the bearing C<5>. The drum is adjusted on its axis to bring the appropriate speed uppermost so as to be visible beneath the transparent plate F carrying the chart shown in Fig. 17. One half of the chart shows curves R<3> for times of flight of projectile at various heights of target, the other half giving fuze times by curves R<4>. The cover A' of the casing A<3> carries marks E<6>, E', Fig. 2, radially and oppositely adjustable through right and left handed screws E by turning a hand-wheel E<3>. When the chart has been turned by wheel F<1> to bring the appropriate radial height line thereon against the mark E<6>, this mark is moved (for the case shown in Fig. 17) to the point of coincidence between the " 10 secs." time of flight line R<3> and the " 10 secs." time line on the drum D. This mark E<6> therefore indicates the future position of the target and the opposite mark E' indicates the correct fuze time, provided the said coincidence is maintained by turning the cover A' by hand-wheel A<16>, and by turning the hand-wheel E<3>. To enable these adjustments to be set up on the instrument as vertical deflection and lateral deflection either in azimuth or plane of sight, the lower part of the casing is provided with triangulation devices which set up present and future positions on the sun members of differential gears the planetary members of which are connected to the deflection dials. The triangulation members giving vertical deflection are shown in Figs. 5 and 6. The height setting is conveyed to pins J<2>, J<3> on right-andleft handed screws H, the pin G being geared to the hand-wheel B' to give the present ground range, and the pin K<12> being geared with the hand-wheel E<3> to give the future ground range. The angle between the links J<7> and K<13> is conveyed through a shaft G<9> and a sleeve K<17> to the sun members G<13>, G<12> of a differential gear, the planet wheels of which give through a gear G<14> the reading of vertical deflection on dial G<15>. Lateral deflection in azimuth is shown on a dial M driven through a clutch M<1> from the shaft M<5> moved by rotation of the cover A<7>. By displacing the clutch, lateral deflection in the plane of sight may be given on the dial M, such deflection being given on a differential gear L" by the angle between the lever J<7> and a lever L<5> forming part of the triangulation device shown at the bottom of Fig. 10. The above described means for setting up lateral deflection in plane of sight is only suitable for targets approaching and receding, more accurate means being described for a crossing target. The appropriate scale for target speed is brought uppermost on the drum D by following the target for say 10 secs. during which time finger-pressed levers N<16>, Fig. 11, operate to press a bracket D<16> against the fixed platform A<9>. The movements of the carriage C<1> then draw a vane D<14> through the bracket D<16> and cause rotation of the drum D through a shaft D<8>. Means are provided for quickly turning the carriage through 180‹ on the bearing C<5> to meet the case when the target suddenly reverses its course.