LAMINATED MAGNETIC HEAD FOR EFFECTING CHECKERBOARD PATTERN MAGNETIZATION OF A MAGNETIC MATERIAL

1,136,147. Electromagnetic printing. AGFAGEVAERT A.G. 11 May, 1966 [21 May, 1965], No. 20824/66. Heading B60. [Also in Division H1] Apparatus for magnetizing a record carrier to exhibit a finely divided chequered pattern of alternately north and south magnetic poles extending two-dimensionally of its surface, comprises (Fig. 1) a stack of U-laminations of thickness corresponding to the width of record carrier to be magnetized, wound with series electromagnet coils 5, 6 establishing opposed polarities at the legs of the U, which contact a stack 21 comprising plural triangular laminations, of which a first comprises (Fig. 2) a soft iron plate 11 composite with a beryllium bronze plate 14 of equal thickness, a complete beryllium bronze-plate 12, a soft iron plate 13 composite with a beryllium bronze plate in reciprocal relation to plate 11, 14, a beryllium bronze plate, and so on in sequence ; the magnetically permeable plates overlapping only at the apex of the triangle, and being energized respectively by the north and south poles of the electromagnet. The stack is ground to a sharp edge at apex 22, and with electromagnet is orientated to dispose its magnetic axis at a critical acute angle to the normal the record carrier 25, which is traversed over a soft iron support plate by spring loaded rubber sheathed rollers 27, 28 driven by synchronous motor 29. The leading is edge of apex 22 may be chamfered (Fig. 4, not shown). In operation, the electromagnet is energized from a switchable A.C. supply also energizing motor 29, and the record carrier 25 is traversed at a speed which is in a predetermined ratio to the supply frequency, and on succeeding half cycles bands of alternate N S NS &c. and SN SN &c. poles are impressed transversely of the record carrier, which consequently assumes the required chequered pattern of N and S poles. The pattern may be subjected to infra-red radiation delineating an image, e.g. of printing, such as to raise the temperature of the exposed pares above the cure point for demagnetization, whereby the unaffected parts retain magnetization to attract a magnetic pigment powder or ink, which may be transferred to paper or a copy carrier.