Patent GB-1160152-A (GB)
Title: Disc Memory Assembly
IPC: G11B5/55
Filed: 1966-10-12
Abstract: 1,160,152. Memory discs; disc assemblies. SOC. GENERALE DU VIDE (Sogev). 12 Oct., 1966 [12 Oct., 1965], No. 45683/66. Heading G5R. A memory device comprises a memory disc having a record medium (e.g. a magnetic coating or film) on at least one of its side faces and supported for rotation without positive restraint against limited axial displacement, backing means co-operating with the opposite side face of the disc, a lateral positioning member mounted adjacent the first side face for limited axial displacement relative to the disc and the backing means (the member including means defining a reference surface generally parallel to the disc side face), forcedeveloping means in the member co-operating with the disc for controlling the axial distance between the first side face and the reference surface, and an information-transfer head (e.g. a magnetic head) mounted in the member for coacting with the record medium and in a predetermined axial position with respect to the reference surface, so as to maintain a prescribed operating clearance between the head and the record medium. The assembly to be described includes several memory discs, each having a magnetic coating on each face. Each disc 5, Fig. 12, is made of non-magnetic material, e.g. metal, ceramic, glass or plastics, and has a rim 103 to protect the faces, to assist positioning in the device, and to facilitate stacking in storage. Cell construction.-The apparatus includes a number of cells, each consisting of a rectangular dish arranged vertically, Fig. 3, with the right-hand wall omitted, and abutting against the left-hand wall 6 of an adjacent cell. The front wall 8 of each cell is slotted at 4 and covered by a hinged cover 3, Fig. 2. The inner surface of each wall 6 is formed with three bosses 25 to 27 to which are secured shoes 21 to 24 respectively (see also Fig. 12). Another shoe 24 is secured to a boss 29 integral with the cover 3, Fig. 2. In operation, the shoes " support " the discs (see below). Three members 41 and one member 48 which accommodate magnetic heads are movably secured to the wall 6, Figs. 2, 3 and 9, and four similar members 77 and movably secured to a vertical plate 59 which is movable in a direction perpendicular to its plane, Figs. 3 and 9. Prior to loading a disc 5 in a cell, the plate 59 is pushed to the right, as in cell C3, Fig. 3, by three springs 83, Figs. 3 and 2, upon deflation of a pneumatic finger 84. A pair of upper guide rails 87 is secured to a yoke structure 89 mounted on a shaft 91 pivotable in bearings 93, Fig. 2. A lever arm 95 projects from the shaft 91 and is connected by a tension spring 101, Fig. 3, to the plate 59, so that when the plate is in its extreme right position, the rails are urged to the right, the end of the lever arm engaging a stop post 99 projecting from the plate 59. A pair of lower guide rails 88, similarly arranged, is provided. Disc insertion, support and drive.-The cover 3 of a particular cell is raised and a disc 5 is slid inwards between lower and upper runways 82, Fig. 2, and between the members of each pair of guide rails; the cover is then closed. Air is now supplied to chambers 35, one being provided in each of the shoes 21 to 24, Fig. 12. The air issues from a slot 37 extending the whole length of the shoe and impinges against the rim 103 of the disc. The disc is thus supported by the sheet-like air jets, issuing from the four shoes, in a balanced, floating condition. Air is next supplied to members 41, 78 and 77; in the case of a member 41, Figs. 8 and 9, it issues from the end of a boss 40, impinges against the closed wall 400 of the bore 43, flows past the roughened bevel surface 44 into the body of the member 41, and finally escapes from four ports 48, Fig. 8, to impinge against the adjacent face of the disc 5. The disc is thus positioned equidistantly between the two sets of four members, and each member has its " working " surface maintained parallel to the adjacent disc face by its four jets 48. Next, air is supplied to the pneumatic finger 84 so that the cell and its contents assume the orientations of cell C2, Fig. 3, except that the disc 5 is just out of contact with the guide rails 87, 88. Finally, the disc is urged into, and maintained in, rotation by the supply of air to a series of drive nozzles 106, Fig. 2, spaced at intervals around the disc in its operative position; the air impinges against angled serrations 223 provided on one face of the disc. For braking purposes, oppositelydirected nozzles 107 direct air against oppositely-disposed angled serrations (not shown) provided on the other face of the disc, when necessary. Head and track arrangements.-Each member 41 and the like accommodates four banks of magnetic heads 42, Fig. 9, whose operative end faces 52, Fig. 8, are maintained at a distance e" from the adjacent disc face during use. To avoid excessively close positioning and objectionable cross-talk, the heads in each bank are spaced by a distance equal to that between four tracks on the disc. Thus bank I, Fig. 8, is associated with the tracks numbered, e.g. 1, 5, 9 . . ., bank II is associated with tracks 3, 7, 11. . ., bank III is associated with tracks 2, 6, 10..., and so on. If the member 41 of Fig. 8 is represented by A, Fig. 2, member B, or 78, may be associated with a further, similar set of tracks numbered, e.g. 1<SP>1</SP>, 2<SP>1</SP>, 3<SP>1</SP>. . . in the same (inner) annular array, Fig. 2. Two further members 41 are associated with an outer annular array of tracks, as shown. Alternative driving and supporting arrangements.-Instead of the air drive, an electric motor for each disc may be provided, fixed to the cell wall and having a flange on its drive shaft, the flange having mounted thereon three axially-displaceable plungers. The plungers, when engaged with the walls of a curvilinear triangular recess in the disc face, drive the disc without impeding its centreless floating condition (Fig. 16, not shown). Instead of four peripheral, disc-supporting shoes 21 to 24, only two, symmetrically disposed around the bottom of the disc, need be provided (Fig. 14, not shown). As a further alternative, these may be replaced by a single shoe. According to a modification of the arrangement of the four shoes 21 to 24 above described, these may be mounted on their supports in positions that are circumferentially tilted in a common direction by a small equal angle. Then, when the disc is spinning at its prescribed speed, the air supply to these shoes is cut off, the disc then being supported by the boundary film of air entrained by the disc periphery and forced into the wedge-shaped spaces thus formed. Fail-safe arrangements.-Air is normally supplied from a pump manifold 202, Fig. 13, to drive nozzles, shoes and actuators. In the event of air failure, a pressure pick-off 222 opens a valve 220, supplying pressure air from a separate source 218 to the braking nozzles 107. Plate 59 moves outwards, and the disc, now stationary, drops on to the peripheral shoes. The members 41, 77, 78 (or " lateral shoes ") remain supplied with air from reservoir 212 until the disc has come to rest.