Abstract: A ventilation system for use with a computer disc drive is described which enables disc file data storage capacity to be increased for a given volume of chamber housing the discs and which provides increased disc-drive performance. A plurality of axially extending channels is provided in the hub of the drive and a breather filter is located axially, at one end of the hub, in the housing wall of the chamber. Rotation of the discs causes air to be thrown out to the periphery of the discs creating a high pressure zone thereat and a low pressure zone at the rotation axis. Air is drawn into the low pressure zone and is communicated to the inter disc spaces via the axially extending channels from where it is thrown out by centrifugal force during rotation. A substantially constant air density is provided adjacent the disc surfaces leaving the aerodynamic characteristics of the read/write heads substantially unaffected and facilitating the reduction of interdisc spacing.

Abstract: A method and apparatus for controlling a stepper motor and a disk drive is described for minimization of stepper motor oscillations for a single step, minimizing the time taken for the stepper motor to move between tracks for multi-track seeks, and reduction of angular hysteresis due to the mechanical and magnetic properties of the stepper motor construction.This control is achieved using a microprocessor-based circuit adapted to drive the stepper motor in accordance with predetermined programs. Oscillations of the stepper motor are damped by controlling, using one program, the current applied to the stepper motor during the last step of its motion by switching this current on and off within small predetermined time intervals. The time taken to move between tracks is controlled by another program in which the non-linear torque speed characteristics of a particular stepper motor are matched by a non-linear pulse rate which is determined by data held in the memory of the microprocessor circuit.

Abstract: In a disk drive system which uses as stepper motor, overshooting of the desired final position is reduced by short-circuiting the windings of the stepper motor which normally remain open-circuit or are switched off. This short-circuiting provides a current path for any EMF induced in the unused windings. This effect is achieved by connecting a pair of transistors in parallel with each other and with each respective winding. The transistors are connected in opposite polarity to provide a short-circuit regardless of the polarity of the EMF across the windings. The transistors are connected to a microprocessor which is programmed such that the windings are selectively short circuited and the short circuits are applied at a predetermined time with regard to the step so that `damping` is optimized. The microprocessor may be programmed to switch the transistors on and off as desired giving flexible timing to suit different conditions. One or more stepper motor steps may be treated in this manner.