Patent GB-880327-A (GB)
Title: Improvements in or relating to magnetic signal storing and/or reproducing apparatus
IPC: G11B15/43
Filed: 1959-12-22
Abstract: 880,327. Friction clutches; gearing for stopping and starting machinery. TELEFUNKEN G.m.b.H. Dec. 22, 1959 [Dec. 24, 1958; Nov. 11, 1959], No. 43512/59. Class 80 (2). [Also in Group XXXVIII] A system of magnetic clutches is used in a tape recording mechanism (see Group XXXVIII). In one form of magnetic clutch a motor 101 having a shaft 104 connected to shaft 106. Coaxial with shaft 106 is shaft 109 carrying the capstan. Riveted to the shaft 106 is a disc 112 carrying the lower annular half-cup 113 of an electromagnet. A disc 114 carries the upper half-cup 115. Discs 114, 112 are connected by bolts around the periphery so that they rotate with shaft end 106. In the cavity formed by the half-cups is a coil 117 connected to slip rings 118. Between the inner edge surfaces of the annular half-cups 113, 115 is situated the periphery of a very thin metal diaphragm 119 in metal disc form. A further diaphragm is mounted on shaft 109, with similar half-cups 121, 122, and similar discs 123, 124. The upper disc is connected by screws 125 to the stationary frame 102. The discs 123, 124 are connected by bolts 126, springs 127, 128 causing the magnet cups to be biased towards each other. On starting, a potential energizes windings 117 through slip rings 118 and diaphragm 119 is clamped between the half-cups, and thus shafts 106-109 are coupled together. To stop the capstan winding 117 is disconnected and winding 129 is energized. Then disc 120 is clamped between the stationary half-cups 121, 122. The shaft is thus decoupled from shaft 106 and is stopped instantly. In a further embodiment the disc may be supported in the air gap of an annular electromagnet. A drive disc 201, Fig. 3, is attached to a shaft 202 rotating in bearings 203 to which is attached a magnetic yoke 205, supplied with current by slip rings 208 and brushes 209. When energized, the yoke attracts armature 206 and clamps the spring steel coupling disc 207 at its periphery. A further spring steel disc 216 is mounted on shaft 214 similarly between armature 217 and yoke 218. Armature 217 is connected to the upper part of the housing by bolt 220. When the windings are unenergized springs 222 lift the discs so that they run freely in the air-gap. The armatures and yokes are provided with clutch linings 223, the lining mixture, applied in liquid form, being casting resin powdered quartz and metal filings. In the clutch, Fig. 4, a shaft 302 carries a disc 314, the edge of which is the armature 306, which is attracted either to yoke 305 or 315. Yoke 315 is attached to shaft 302 with insulating cement, the shaft also having slip rings 307. Yokes 305, 315 are shaped like crown-wheels, a coil 309 or 317 being slipped over every tooth as indicated in 403, Fig. 5. A friction lining 404 is fitted between two teeth. To provide for rapid tape drive reversal two clutches are used for each drive, coupled to a shaft by toothed gears so that the shaft direction is determined according to which clutch is energized. In Fig. 7, two capstans are used and the tape is applied to one or the other by a displacement of pressure rollers 513, 514.