Patent GB-1235334-A (GB)
Title: Data storage apparatus
Inventor: TSUI FRANK
IPC: G11C11/14
Filed: 1968-08-01
Abstract: 1,235,334. Magnetic storage apparatus. INTERNATIONAL BUSINESS MACHINES CORP. 1 Aug., 1968 [17 Aug., 1967], No. 36652/68. Heading H3B. [Also in Division G4] In data storage apparatus comprising two ferrite layers sandwiching a layer of intersecting strip conductors to form a ferrite block two of the four corner areas surrounding the cross-over of two conductors which are arranged diagonally opposite to each other are non- magnetizable areas which channel the magnetic flux due to a current in the conductors to a flux path diagonally through the other two corners. In a first embodiment two ferrite layers provided with square holes 2 in chessboard fashion, Fig. 4, have sandwiched therebetween orthogonal conductors 3, 4, the conductors 3, 4 and holes 2 being so matched to each other that the conductors extend along the peripheral edges of the holes. The square lands 8 of the layers of ferrite between the holes are linked with each other by two ferrite legs on both sides of the conductors which two legs together with the corner areas of the lands 8 they connect form the closed flux path of a storage element 9<SP>1</SP>. The storage elements may be operated by coincident currents. To increase the mechanical strength the holes 2 can be filled with a ceramic material. In order to accurately determine the flux cross-section the square lands 8 may be coated with a magnetically insulating layer 11 leaving unshielded the corner areas. This layer can be formed of a non-magnetic layer disposed between the two ferrite layers or of a non-magnetic metal layer which through eddy current effects as a magnetic screen. In the arrangement of Figs. 7 to 9 (not shown) the holes 2 are replaced by magnetic insulating layers which are embedded in the ferrite layers prior to sintering thereof and which may be of a non- magnetic coating or a good conducting metal. Instead of employing square holes or insulating layers circular holes or insulating layers may be used, Fig. 10 (not shown). The diameter of the circular holes and the width of the conductors are such that the holes of two neighbouring lines or columns partly protrude into the conductor extending between the lines or columns to ensure that the overlapping area of two intersecting conductors is limited by the two neighbouring holes. Fig. 11 shows an arrangement in which magnetic insulating areas are used for channelling the magnetic flux and in which zig-zag strip conductors 30, 31 form the insulating areas. The strip conductors 30, 31 are arranged between two unpunched ferrite layers so that with the exception of square lands 32 and negligibly small lands 33 the ferrite face is covered by the conductors arranged as shown. Eddy currents produced in the conductors channel the magnetic flux through the corner areas 34 of the areas 32 to form storage elements. The invention may be applied to the formation of multi-aperture cores, Fig. 12, which shows a ferrite block consisting of three ferrite layers provided with insulating layers arranged in chessboard fashion and including conductors 41, 42 and 43, 44. By means of conductive layers serving as magnetic screens, two of which 47, 48 are shown, for channelling the magnetic flux, two flux paths 54, 55 are obtained and the storage cell comprises three legs 49, 50, 51 corresponding to flux paths in a conventional transfluxor around minor, major and minor and major apertures. The block 40 is made using a first centre ferrite layer having a low He value, a second ferrite layer of the same thickness but higher He value and a third ferrite layer twice as thick and having a very high He value.