Patent GB-579325-A (GB)
Title: Improvements relating to electrical calculating apparatus
IPC: H04N3/26
Filed: 1942-11-30
Abstract: 579,325. Electrical gunnery calculating-apparatus. COSSOR, Ltd., A. C., BEDFORD, L. H., BELL, J., and LANGHAM, E. M. Nov. 30,1942, No. 17006. [Class 92 (ii)] [Also in Group XIX] An electrical calculating system comprises apparatus for producing from a source of alternating voltage of low frequency and substantially constant amplitude, two alternating voltages co-phased with each other but varying in amplitude relative to that of said source in proportion respectively, one to a variable ratio and to the sine of a variable angle, and the other to the same ratio and to the cosine of the same variable angle, said apparatus comprising a magslip resolver having its primary winding connected across said source, means to set said magslip resolver to said angle, and a two-gang potentiometer having its sections connected one across each of the secondary windings of said magslip resolver and means to set said potentiometer to said ratio. The principle of the invention is illustrated diagrammatically in Fig. 1, as applied to a predictor, given the polar co-ordinates B, S, R of a target, to find the azimuth Bf<1>, elevation E, slant range R <1> and time of flight tf of the shell of a gun. A source of alternating current 1, free of harmonics is applied to a magslip resolver continuously adjusted according to the angle B, to produce voltages proportional to sin B and cos B, which are applied to cosine potential dividers 21, 22, while the mains 1 are applied to a sine potential divider 20, the potential dividers being in the form of potentiometers ganged together and continuously adjusted according to the angle S. The outputs are applied to linear potentiometers 30, 31, 32 ganged together and continuously adjusted according to R. The outputs are then proportional to the cartesian co-ordinates x, y, H and are applied to devices 2, 3, 4 and 5, 6, 7. The devices 5, 6, 7 produce potentials proportional to x, y, H, in the manner described in Specification 579,336, [Group XIX], which potentials are measured in the manner described in Specification 579,337, [Group XXXVI], to be applied to the devices 2, 3, 4 as described below. The correction for the time of flight of the shell tf is a non-linear function of the estimated range R<1 >and this factor is entered by a resistor 80 adjustable for miscellaneous corrections and a graded potentiometer 72, also Fig. 3, which supplies a cathode follower valve 301 to energize a transformer 302, from which several secondary windings 304, 314 ... , equivalent to the devices 2, 3, 4 of Fig. 1, are taken. Considering winding 304, the input x is applied at 114 and tapping 305 is moved according to x, referred to above, while tapping 306 is manually set according to the x component of the wind. A similar arrangement exists regarding y in winding 314, while further windings (Fig. 4, not shown) take in the potentials H, H and a vertical correction for wind applied by a magslip resolver in which both the stator and the rotor are rotatable. The respective sums of the x and y voltages are applied to null indicators 90, 91, supplied on the other side with voltages xf<1>, yf<1> by a magslip resolver 40, 41 rotated according to the estimated angle B<1>f and ganged linear potentiometers 50, 51, rotated according to an estimated r<1>f which is equated through a null indicator 92 with R<1> cos E supplied through devices 60, 70. Meanwhile, the sum of the H voltages is applied to a null indicator 93, supplied on the other side by a voltage H<1> equal to R<1> sin E. A practical arrangement of elements 40, 50, 90 and 41, 51, 91 is shown in Fig. 5, in which a magslip resolver 701 has a secondary winding 703 tuned to the same phase as the mains by a suitable condenser. A linear potentiometer 704 opposes the voltage supplied by tapping 305 (equivalent of 2 in Fig. 1) with a voltage x<1>f, and the resultant energizes the transformer 705, the secondary of which is applied to a pentode valve 708 which supplies the deflector plate 710 of a cathode-ray tube. The other secondary winding 714 of the magslip resolver similarly controls the' deflector plate 716, so that deviation of the cathode-ray spot indicates error in the estimate of Bf<1> or rf<1>. By providing hairlines on the screen, mechanically coupled to the rotor of the magslip resolver, the spot can be made to move in one direction with alteration of Bf<1> and perpendicularly with variation of rf<1>. The null indicators 92, 93 can be similarly combined. The estimated values of Bf<1>, rf<1>, E and R<1> are interdependent and are correct only when null indications are given simultaneously by all the indicators 90, 91, 92, 93. The cathode-ray tube is arranged for alternating excitation in the manner described in Specification 579,339, [Group XL]. An alternative arrangement for adjusting the magslip resolver 701 and potentiometer 704 is by using a further magslip resolver in the manner described in Specification 579,338, [Group XIX], to give indications of the corrections necessary, or to operate servomotors to effect the necessary corrections automatically. The values of Bf<1>, E and tf can be continuously transmitted to the gun crews by selsyns.