Abstract: Turntable (10) has a turntable bottom (19) and a turntable wall (20) which together define a locating space (21) in which the hub (7) of an information disc is engageable, and in which it is centered by means of a centering member (12) and clamped by magnetic clamping means. At the circumference of the locating space a centering wall (26) is provided, which wall has an inwardly sloping surface (27). The dimensions of the various parts, the field strength of the magnetic means and the coefficients of friction of the cooperating materials of the hub and the turntable are selected in such a way that, once an information disc has reached a position in which the free end of the centering member (22) has engaged the centering hole (17) of the information disc, the outer wall (28) of the hub (7) is situated above the sliding surface (27) of the turntable.

Abstract: A disk cartridge having a housing in which a disk is rotatably mounted via a hub assembly. The housing includes two cover plates, each of which has a door aperture that is selectively covered by a door that is controlled by a dedicated door control assembly. When the cartridge is inserted into a disk drive, each door is opened by its respective door opening assembly such that both sides of the disk are accessible for magnetic or optical read/write operations.In the preferred embodiment, the hub assembly includes two hub halves, at least one of which includes a plurality of resilient fingers for leveling a surface of the disk when the cartridge is contained within the disk drive. At least one of the hub halves also includes a channel having a plurality of pockets formed therein such that when a spindle base having a torque transferring element is positioned adjacent to the pockets, one of the pockets is able to substantially immediately receive the torque transferring element.

Abstract: A mold is manufactured using a substrate and hub also used in the manufacture of the disc. A structure carrier provided with a mold structure is detachably connected to a substrate, and the mold structure is then centered relative to the central recess of an auxiliary tool. A disc hub is then centered relative to the recess and fixed to the substrate and the assembly of the hub, the substrate, and the structure carrier is centered on a mold base which likewise has a central recess. The structure carrier is fixed to the base, and the substrate is detached from the structure carrier leaving the mold structure centered relative to the central recess.

Abstract: Information carrier includes an optically readable disc with a center hole and a hub with radially resilient clamping members which extend through the center hole to retain it on the disc and center it with respect to the information carrying surface on the disc. The hub further carries a sleeve which centers it on a spindle, and a magnetizable clamping ring for retaining it on a turntable, which carries permanent magnets. In an information carrier having two discs sandwiched together, the clamping members of each hub extend between the clamping members of the other hub and pass through the center holes of both discs to engage the opposite disc and retain the discs to each other.

Abstract: Method of providing a substrate of an optically readable information disc with an optically detectable structure, mould for use in the method, apparatus for carrying out the method, and information disc manufactured in accordance with the method.Substrate (3) is provided with a disc hub (8) comprising disc-centering means (9) which serve to center the finished information disc (17) on the drive spindle (27) of a drive apparatus. The intermediate product comprising the substrate (3) and the disc hub (8) is centered on the base (1A) of the mould by cooperation between the base-centering means (17) and the disc-centering means (9). This may be effected by the use of an auxiliary centering means (12) which is in contact with a wall (14) of a central centering hole (11) in the disc hub (8) and with a wall (13) of a central centering recess (10) in the base (1A).

Abstract: The invention relates to a method of providing a substrate with a centered optically detectable structure, such as a servo structure on a transport substrate of an optical information disc. The method uses a mould (1) having a base (1A) carrying a mould structure (2) which is covered with a reproduction layer (4) of a transparent radiation-curable resin, which after curing is detached from the mould together with the substrate. In its center the base (1A) of the mould is provided with base-centering means (7) relative to which the mould structure is centered accurately. Before it is placed on the mould a substrate (3) is provided with a disc hub (8) comprising separate disc-centering means (9) which serve to center the finished information disc (17) on the drive spindle (27) of a drive apparatus. The intermediate product comprising the substrate (3) and the disc hub (8) is centered on the base (1a) of the mould by cooperation between the base-centering means (17) and the disc-centering means (9).

Abstract: An interchangeable optically readable storage disk has a substrate with a recording surface, and a cover thereon which may comprise a second substrate with a further recording layer. The disk includes a protecting arrangement at the circumference of the substrate, which includes a balancing arrangement. The balancing may be effected by apertures in the protecting arrangement, or balancing masses affixed thereto.