Patent GB-1483565-A (GB)
Title: Stacked flexible disc data storage devices and access methods therefor
IPC: G11B5/55
Filed: 1975-05-21
Abstract: 1483565 Accessing disc memories INTERNATIONAL BUSINESS MACHINES CORP 21 May 1975 [29 Aug 1974] 21856/75 Heading G5R To access a selected disc in a disc data store, comprising a plurality of flexible record discs arranged in one or more groups on a common support 12, Fig. 1, with each group having two outer discs E, A of maximum radius with discs B, C, D of other radii interleaved therebetween, a control, Fig. 14, causes an accessing mechanism (20), Figs. 11, 12 (not shown), to perform a "weaving" motion consisting of alternate axial and generally radial movements. Each disc group may have discs of three different radii arranged as in Fig. 1, certain discs A, E being common to two groups. Arrangements with discs of four and five different radii are also disclosed, Figs. 8, 10 and 9 (not shown). The discs are stabilized by a rigid backing plate 16 and radial air flow from shaft 12 through spacers 15. The accessing mechanism (20), Figs. 11, 12, has an axial carriage (54) moved axially by a leadscrew or voice coil 55, Fig. 14, and carrying a radial carriage (60) moved radially by a voice coil 63, Fig. 14, to move air foil-shaped disc partitioning access arm (23) radially, or by means of a pivoted link, in a generally radial arc Fig. 13 (not shown). Arm (23) carries a transducer (23A), or, if both sides of each disc are record surfaces, two transducers for simul. taneous access to facing sides of two immediately adjacent discs. An accessing control, Fig. 14, for a disc pack as in Fig. 1 with one record surface per disc, has a coarse position control 80 which initially supplies the address of an access window 24, Fig. 1, between the outer discs A, E of the required group, to add and hold circuit 81 which acts to drive axial voice coil motor (V.C.M.) 55 until circuit 83 gives an output on line 86 indicating that the X (axial) position of arm (23) sensed at 85 agrees with the address in circuit 81. A cycle counter 91 is then moved from the zero to R1 state whereupon AND 94 passes a 50-mil. radial movement signal from constants register 95 to add and hold circuit 96 which drives radial VCM 63 until the R (radial) position of arm (23) sensed at 103 agrees with the address in circuit 96 whereupon counter 91 steps to the X1 position to cause circuit 81 to drive axial VCM 55 by 16 mils. according to a signal from store 95 and in a positive or negative direction under control of signals from register 111 which receives data indicating which disc of the group is to be accessed. Completion of this X movement, or sensed by X-compare 83, steps counter 91 to the R2 position which causes radial VCM 63 to move arm (23) radially in by a further 50 mils. Counter 91 then steps to the X2 position which causes drive of VCM 55 to effect a + or - 8 mils. axial movement of arm (23) under control of signals from store 95 and register 111 to add and hold circuit 81. Counter 91 then steps to the END position resulting in return of counter 91 to its zero state and a signal on line 123 enabling track addressing circuits 124 to drive radial VCM 63, via circuits 96, 100, 101, to select the desired track on the selected disc.