Patent GB-753167-A (GB)
Title: Magnetic switching device
IPC: H03K17/97
Filed: 1954-04-26
Abstract: 753,167. Non - contactmaking relays NATIONAL CASH REGISTER CO. April 26, 1954 [May 18, 1953], No. 11979/54. Class 40 (4). [Also in Groups XIX, XXXVIII and XL (b)] In a magnetic switching device comprising a plurality of saturable cores each magnetically coupling an input and an output coil, an alternating input is transferred to the output of a selected core or cores according to the position of a movable control magnet which establishes an unsaturated condition, the remaining cores being disabled by magnetic saturation. As shown in Figs. 2 and 3, a number of toroidal cores 20, each formed of material having a substantially rectangular hysteresis loop such as ferrite, are radially positioned around a rotatable control magnet which comprises a hollow longitudinally-magnetised cylindrical permanent magnet 28 and circular polepieces 23, 24. A pair of low-reluctance connecting portions 21, 22 extend from diametrically opposite points on each toroid to positions adjacent the polepieces, the input coil 26 being arranged with half its turns on each side of portion 22 while the output coil 27 is similarly arranged about portion 21. The input coils may be energized in series from a common alternating source 30 and the selection of an unsaturated core over which the signal is transferred is determined by the position of a large air gap formed by notches 29 in the polepieces, the other cores being saturated by the control magnet. As each input and output coil is symmetrically disposed on either side of a connecting portion, induced switching transients arising from flux changes are neutralized within the coils. Two or more cores may be desaturated together by arranging the notches to subtend a larger angle or by providing additional notches. Alternatively a plurality of cores 31, 34 having separate input and output coils 32, 33 and 35, 36 respectively, Fig. 1 (part), may utilize common connecting portions 40, 42, adjacent cores being linked magnetically by a further connecting portion 41. The switching device may be utilized to route information read from predetermined sectors I-IV of a magnetic data storage drum 51, Fig. 5, to different output channels, the control magnet 50 being rotated with the drum. The reading head 54 is connected to all the cores over an amplifier 55 and parallel-connected input coils 56, and as the notch 53 in the control magnet subtends the same angle as that over which a signal for a particular channel is recorded on the drum, the reproduced signals are directed in turn to the appropriate output channels. As the control magnet may be rotated at speed it may be balanced by fitting non-magnetic plates 57 adjacent the recesses. In a modified construction of the switching device, the polepieces may be made relatively movable to the cylindrical magnet and independently adjustable with respect to the cores. With this arrangement each polepiece independently desaturates a particular core, according to the position of its notch. In a further modification, Fig. 7, the control magnet 69 is in the form of a notched channel member which is secured to a supporting member 70 and is longitudinally movable relative to the cores. With the control magnet in the position shown all the cores are saturated. An alternative arrangement of the cores and control magnet are shown in Fig. 8, in which each core is normally saturated by an associated permanent magnet 84, desaturation of the selected core being effected by a U-shaped control magnet 83.