This invention relates to a magnetic disc memory. Known magnetic disc memories comprise a plurality of circular magnetic storage discs which are arranged fixed against rotation and axially spaced from one another on a shaft directed at right angles to the disc plane, a drive mechanism to drive the shaft, a plurality of swivel arms to hold the magnetic heads serving to record and play back information onto the or from the magnetic storage discs, the swivel arms being mounted pivotably for a common swivel movement about a pivot directed substantially parallel to the shaft of the magnetic storage discs, so that a swivel arm can be pivoted at least partly into each gap between any two magnetic storage discs adjacent one another, and a drive mechanism to swing the swivel arms, the magnetic storage discs and the swivel arms together with the magnetic heads being enclosed in a housing.
The quality of such a magnetic disc memory is determined substantially by four criteria: by the reliability with which information can be stored and reproduced, by the mechanical dimensions, by the power input and by the access time, that is, the average period required to locate a certain storage place and to store or read information at this storage place. The reliability of storage or reproduction is determined by, among other things, the storage density, that is, the number of storage places per unit of area of the magnetic storage discs. For a given storage capacity it is not permissible, therefore, to fall short of certain minimum dimensions of the magnetic storage discs.
The access time is substantially determined by the speed at which the magnetic heads can be adjusted to a certain storage place of the magnetic storage discs. So that high setting speeds can be achieved, on the one hand, the moving parts (swivel arms, magnetic heads) must be made stable, so that they withstand the high acceleration forces and are not excited to the point of their natural mechanical resonance, and, on the other hand, correspondingly strong drive mechanisms are required, so that the swivel arms can be moved with the correspondingly high acceleration. Because of this, the volume and weight of known magnetic disc memories are relatively large, although a reduction in size of the magnetic storage discs, while retaining the same storage capacity, would be possible owing to improved coating of the magnetic storage discs and the higher storage density obtained thereby.
The problem of the invention is to design a magnetic disc memory of the above-mentioned type, so that its dimensions can be reduced and a lessening of the power input and a shortening of the access time are achieved at the same time.