GB1369902A - Multiple pulse generator - Google Patents

Abstract

1369902 Magnetic storage devices; non contact making switches J R WIEGAND and M VELINSKY 31 Aug 1971 40516/71 Headings H3B and H3X A multiple pulse generating device comprises a bundle of magnetic wires held together by a dielectric to form a cylindrical body. Each wire is of a generally uniform composition and is treated by heating and work hardening so that its core portions are of lower coercivity and retentivity than its outer, shell portions. The wires may have helical easy axes of magnetization. Normally the magnetization of the core is in the opposite direction along the wire to that of the shell, and forms a flux path for the shell. When an external field is applied along the wire, either by a coil or permanent magnet, and the field is increased, the magnetization of the core is suddenly aligned with the external field as the influence of the shell is overcome. This sudden change of magnetization, which occurs by passage of a domain wall along the core, will induce a sharp pulse in an adjacent output coil. Figure 1 shows an external field coil 22 and an output coil 24 wound on a bundle 17. The output from the coil 24 is shown against the applied field in Figure 5, each step representing one of the wire cores being aligned with the applied field. The device may be used in a magnetic memory of high signal to noise ratio. In Figure 2 a permanent magnet is held adjacent a bundle of the wires by a flexible material 30, so that when the magnet is moved by pressing button 38 multiple pulses are obtained from the coil 24. Several such push-button devices may be connected to the same output winding. By changing the cores for ones with a different number of wires a different number of output pulses are obtained. Manufacture:-The wires are prepared from an Fe-Ni alloy, and the preferred wire is 48% Fe-52% Ni having 10,000 grains/mm<SP>2</SP>, and a diameter of 0À012 inches. The wire may be drawn from a rod of 1-1¢ inches diameter through successive dies at some 75 feet/minute, each die giving a 20% reduction in area. This drawing is done at a temperature which produces the desired grain size, and is followed by room temperature work hardening, e.g. a 2¢% strain. A helical easy axis may be obtained by twisting the wire while it is tension. The resulting wire is cut into lengths and potted.