Patent GB-626736-A (GB)
Abstract: 626,736. Gun-sight predictors. KODAK, Ltd. Jan. 13, 1947, No. 1134. Convention date, Jan. 12, 1946. [Class 92 (ii)] [Also in Group XXXV] A vector solver, particularly for use in predicting apparatus for guns, comprises at least one dipole coil 10, Fig. 1, wound on a substantially spherical core 11 with the turns distributed uniformly along a diameter of the sphere, and at least one electric pick-up coil 16 supported for rotation about the sphere's centre, means 20 being provided for applying alternating current to one of the coils and signal transmitting means, such as a wattmeter 22, being provided which are responsive to the current induced in the other coil. In Fig. 2, the dipole has eight groups 25 of forty turns evenly spaced along an axis; in a modification there are twenty groups. The sphere may be mounted on pins 13 of gimbals 14 to permit universal motion of its dipole axis 12 with respect to the coil 16. For predicting apparatus there are three dipole coils mutually at right angles on a sphere and three similarly arranged pick-up coils, as shown in Fig. 11. Problem.-In gunnery calculations the problem to be solved is the future position F, Fig. 10A, of a moving target with respect to the sighting point C, that is, the position of the target when a projectile reaches its path, the projectile being fired when the target is at its present position P. In the present invention, this is done by tracking the target from a given instant, termed the memory point instant, when the target is at M, and solving the vectors to discover point F at any present moment P. The value of the range vectors Dm and Dp are given by a range-finder. In solving the problem the apparatus divides the vectors CM, CP and MP by the time of flight tm to the memory point, Fig. 10B, and the other vectors by the time of flight tf to the point F. Apparatus.-The apparatus, Fig. 9, includes a memory point vector solver A and a prediction solver B, each having three dipole coils, each at right angles to the other two, and three similarly arranged pick-up coils 180, 181, 182 and 210, 211, 212 shown in Figs. 11 and 12. The whole apparatus is mounted on a platform which follows the target in azimuth and the dipole coils are rotated in elevation by gearing 67 to keep their range coil axes directed at the target. The other two dipole coils of each solver are termed the elevation coil and azimuth coils. The pick-up coils 180, 182 are always maintained in the north-south and east-west directions, but those of the prediction solver are movable. The target is followed by two telescopes 91, 92, tracking being effected by handles 94, 100, associated with aided tracking devices 95, 102, details of which appear in Fig. 18 (not shown). Device 102 rotates the entire apparatus around a fixed ring 101, and present azimuth data therefore appears in a gear 103 and hence in a shaft 105, which rotates the coils 180, 182 to keep them stationary in space as referred to above. A servo 109 adds azimuth lead, as obtained in the prediction solver, to present azimuth in a differential 113, and thus the gun azimuth appears at 115 to be fed to fine and coarse scales 116, 117 and transmitters 118, 119. Similarly, present elevation is fed from telescope shaft 98 to the gear 67 of the dipoles, and a servo 125 adds elevation lead and superelevation to produce gun elevation data in shaft 127, scales 130, 131 and transmitters 132, 133. The servomotors 109, 125 (see also Fig. 12) are. so driven that the range coil of the prediction solver dipole points along the predicted position vector as corrected for superelevation &c. Circuit.-Fig. 11 shows a part of the circuit before a memory point is selected and Fig. 1 shows the circuit after such time, the changeover being effected by switch 160. Referring to Fig. 11, present range data is constantly supplied by a servo 178 to a potentiometer 170 which modifies the output of a 5000 cycle oscillator 171 so that current fed through an amplifier 172 to the range coil 173 of the memory dipole is proportional to present range. The vector in coil 173 is analysed in the coils 180, 181, 182, which are associated with variable transformers 183, 184, 185 and phasesensitive motors 186, 187, 188 so arranged that the motors match the induced voltages with voltages applied via potentiometer 174 and amplifier 189. When switch 160 is set to the memory point position, Fig. 12, all the transformers are clamped by means illustrated in Fig. 17 (not shown), and at the same time a clutch 177 of a motor 179 is set in to drive potentiometer 174; the circuit to and from the dipoles is also varied as shown. From the memory point instant onwards the three coils 180, 181, 182 receive from oscillator 171 via potentiometer 174 and the transformers induced voltages proportional to polar components of the memory point vector divided, in potentiometer 174, by the memory time. The dipole is still tracking the target and all three coils thereof receive induced signals, the elevation and azimuth ones of which are amplified at 163, 164 and passed to the corresponding coils of the prediction dipole. The present range component of the memory point range is fed to a mixer 191 where it is subtracted from present range divided by memory time, this being done by potentiometers 170, 174, and added to present range divided by predicted time, this being done by potentiometers 215, 190; this mixing is in accordance with the vectors of Fig. 10B. The result is fed to the range dipole coil 225 and gives the predicted range vector. If now the pick-up coils 210, 212 are moved to make their induced voltages zero, the axis of the range pick-up coil 211 is directed towards the target's future position. Movement of coil 210 is effected by the servo 125, referred to above, which is arranged in circuit with amplifier 233, modulator 234, and a gun elevation potentiometer 141 in such manner that the coil is moved until the voltage across 234 is zero. The servo 109 associated with coil 212 is arranged in a similar circuit as shown. The circuit also includes potentiometers 240 for wind correction, 230 for superelevation, and the potentiometer 215, which are adjusted by a time of flight servo 216 which is in circuit with range coil 211 and potentiometer 221. The potentiometer 230 applies a suitable correction to the coil 210, and a similar device for azimuth drift may be applied to the coil 212. The wind potentiometer 240 leads to potentiometers 241, 242 manually set in accordance with the northsouth and east-west components of the wind velocity, and serving to apply corrections to the coils 180, 182.