US 4,051,541 AGranted

Access to floppy disk stack

AssigneeInternational Business Machines Corporation

InventorsBernard William McGinnis, James Amos Weidenhammer

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Abstract

A method and associated apparatus for efficiently establishing a "self-sustaining" split in a rotating stack of floppy type storage disks in a form suitable for read/write transducing access. The formation of such splits is fully described in U.S. Pat. No. 3,936,800 to McGinnis et al. In the present method a partial split formed at one disk interface position is used as a stable reference for detecting the location of that interface position relative to a target address position. The form of the partial split is not suitable for storage transducing access. However, the partial split forms much more quickly than the self-sustaining split. If the deviation from the target position is zero the partial split is transformed directly into the self-sustaining fully accessible form by controlling internal ventilation pressure between the disks in accordance with said patent 3,936,880. If the deviation is not zero the mechanism forming the partial split (e.g., external air jet) is repositioned in small corrective increments thereby shifting the partial split and eventually reducing the deviation to zero (the deviation being redetermined after each increment of repositioning). Since the time required to form the partial split is much less than the time required to form a fully accessible split it follows that the average access delay, with such "trial-and-error" positioning and iterative determination of deviation, is significantly less than the time required otherwise for correctable positioning of a self-sustaining split.

Claims16

Dependent claims

In a mass storage flexible disk file containing multiple flexible storage disks rotating coaxially in a spaced stack configuration, said stack receiving ventilation fluid internally to replenish ambient fluid expelled from between said disks by centrifugal action, the pressure of said received fluid being variable to cause storage surfaces of said disks to rotate alternatively in distinct first and second states of axial displacement equilibrium, said states serving respectively to inhibit and support formation of a circumferentially uniform auto-sustaining split suitable for storage transducing access at any axial coordinate position in said stack when said stack is transiently disturbed at said position, the method of quickly and precisely aligning a source of said transient disturbance with a target coordinate position in said stack prior to formation of said circumferentially uniform split comprising:

while said ventilation pressure is controlled to retain said surfaces in said first state of equilibrium, applying an external disturbance at a selected trial position in said stack estimated to coincide with said target coordinate but subject to imprecise determination due to varying motion of the eges of the disks interfacing at said target coordinate;
said disturbance forming and sustaining a partial split having circumferentially irregular shape at said trial position;
said partial split being unsuited for storage transducing access;
determining location of said partial split relative to said target coordinate by using a widened portion of said partial split as a relatively stable positional reference for distinguishing said relative location;
when said trial position coincides with said target coordinate position varying the pressure of said ventilation fluid to form said auto-sustaining split at said target coordinate position;
and
when said trial and target positions do not coincide, shifting the position of said external disturbance incrementally until said trial and target positions do coincide and then excecuting said above-mentioned pressure varying step to form said auto-sustaining split.

4 more elements

In a mass storage disk file containing multiple flexible storage disks rotating coaxially in a spaced stack configuration, said stack being supplied with ventilation fluid internally which replenishes ambient fluid expelled from between said disks by centrifugal action, the pressure of said ventilation fluid being variable to condition surfaces of said disks alternatively to distinct first and second states of axial displacement equilibrium, said states serving respectively to inhibit and support formation of a circumferentially uniform auto-sustaining split suitable for storage transducing access at any pre-selected target axial coordinate position in said stack when said stack is transiently disturbed at said position in association with a variation in said pressure, the method of estabilishing a said circumferentially uniform split precisely and quickly at a said target position comprising:

applying a disturbance externally at a selected (trial) axial position in said stack while said surfaces are in said first (inhibiting) state of displacement equilibrium;
said trial position being either coincident with said target position or offset slightly therefrom due to variations in disk thickness and varying motion of edges of said disks tending to make determination of said target position inherently imprecise;
said disturbance forming and sustaining a partial split at said trial position, said partial split having circumferentially irregular shape unsuited for storage transducing access but forming much more quickly than said auto-sustaining split;
determining offset of said trial position relative to said target position by using a wide portion of said partial split as a relatively unvarying positional reference in said stack;
depending upon whether said offset determining step respectively indicates coincidence (null offset) or non-coincidence between said trial and target positions selectively performing a respective one of the following steps:
a. upon coincidence generating an indication of said coincidence;
b. upon non-coincidence correctively shifting the position of said disturbance relative to said stack, in predetermined increments of displacement and in a direction suitable for reducing the offset, and repeating said steps of determining and selectively performing;
and
in response to said indication of coincidence, varying said ventilation fluid pressure to condition said surfaces to said second state of displacement equilibrium while sustaining said disturbance;
thereby causing said auto-sustaining split to form at the target position.

7 more elements

In a mass storage flexible disk file containing multiple flexible storage disks rotating coaxially in a spaced stack configuration, said stack receiving ventilation fluid under varied pressure which replenishes ambient fluid expelled from between said disks by centrifugal action, and which also conditions displaceable storage surfaces of said disks alternatively to distinct first and second states of displacement equilibrium, said states serving respectively to inhibit and support formation of a circumferentially uniform auto-sustaining split suitable for storage transducing access at any selected target axial coordinate position of said stack when said stack is transiently disturbed at said position, apparatus for precisely and quickly verifying correct alignment of a source of said transient disturbance with said target position before forming said split comprising:

means for positioning a said source of disturbance in alignment with a trial position estimated to coincide with said target position;
means effective to jointly condition said ventilation fluid pressure to a condition associated with said first equilibrium state, and said source to a condition for sustainably disturbing said stack to produce a partial split at said trial position having circumferentially irregular form;
means for detecting a relatively unvarying wide portion of said partial split;
means coupled to said detecting means for determining the offset of said trial position relative to said target position;
and
means conditioned upon said determination of offset for alternatively effecting:
a. generation of indication of position coincidence when said offset has null magnitude;
and
b. otherwise initiating coordinated further iterative operation (of said positioning means, said detecting means, said offset determining means and said alternative effecting means) to re-locate said partial split closer to said target position, in re-locational increments sufficiently small to avoid the possibility of overshooting the target position.

6 more elements

Dependencies are inferred from the claim text.