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RELATED APPLICATION ASSIGNED TO SAME ASSIGNEE AS THE PRESENT INVENTION
Hatchett et al, U.S. Ser. No. 847,376, filed Oct. 31, 1977, entitled
"Flexible Record Disk Signal Storage Apparatus," which is a continuation
of U.S. Ser. No. 777,233 filed Mar. 7, 1977 (now abandoned).
BACKGROUND OF THE INVENTION
This invention relates to data storage apparatus of the type comprising a
flexible record disk mounted for rotation over and relative to a
stationary Bernoulli surface, and relates more particularly to a cartridge
containing a flexible record disk, which cartridge is reversibly mountable
on a drive spindle so as to permit transducing access selectively to
either planar surface of the disk.
DESCRIPTION OF THE PRIOR ART
It has heretofore been found that mechanical stability and hence the
recording on and playback from a flexible magnetic disk can be enhanced by
having the cartridge which contains the disk provide a generally concave
stationary Bernoulli surface adjacent the rotatable disk. The disk rotates
on an air cushion above said surface, and the surface has a slot through
which a transducer may access the convex side of the disk.
U.S. Pat. No. 3,830,506 discloses a flexible disk that rotates on an air
cushion above a concave stabilizing surface. A radially movable transducer
accesses the concavely curved cylindrical surface of the disk (i.e., the
surface remote from said stabilizing surface).
U.S. Pat. No. 4,057,840 discloses a cartridge that provides a convexly
curved cylindrical surface. A drive spindle has axially extending drive
pins that enter holes in a flexible disk to rotate the disk.
These configurations enable reading and writing on only one side of the
flexible disk. It would, of course, be preferable if improved operational
characteristics achieved with curved stabilizing surfaces could be
obtained using a cartridge that would enable recording on both sides of
the flexible disk.
SUMMARY OF THE INVENTION
Toward this end and according to the invention, a flexible disk is disposed
in a cartridge comprising two substantially identical housing portions so
formed as to enable the cartridge to be inserted in either of two
positions on a drive spindle. Each housing portion has a slot through
which a recording and/or playback head may access the then adjacent
underside of the disk.
To insure reversibility of the cartridge without loss of mechanical
stability during rotation of the disk, the housing portions provide
respective Bernoulli stabilizing surfaces which face each other when the
cartridge is assembled. According to one embodiment, each stabilizing
surface has two generally diametrically opposed generally flat chordal
parts that extend upwardly and downwardly, respectively, at equal acute
angles from opposite edges of a central part that is perpendicular to the
axis of the drive spindle. The edges of this central part from which these
chordal parts extend may be parallel or divergent. According to another
embodiment of the invention, each housing portion of the cartridge
provides a stabilizing surface having only a single chordal part that
extends upwardly (or downwardly) at said acute angle from a remaining part
that is perpendicular to the axis of the drive spindle.
Other objects and advantages will become apparent from the following more
detailed description of preferred embodiments of the invention and from
the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a plan view, partially broken away, of a reversible cartridge
containing a flexible disk rotatable relative to a selectable one of two
spaced Bernoulli stabilizing surfaces and constructed according to one
embodiment of the invention;
FIG. 2 is a sectional view taken along the line 2--2 of FIG. 1;
FIG. 3 is a sectional view taken along the line 3--3 of FIG. 1;
FIG. 4 is a fragmentary sectional view, to enlarged scale, of the cartridge
of FIG. 1 mounted in operative position;
FIG. 5 is a plan view, partially broken away, of a flexible disk-containing
cartridge constructed according to another embodiment of the invention;
and
FIG. 6 is a sectional view taken along the line 6--6 of FIG. 5.
DESCRIPTION OF PREFERRED EMBODIMENT--FIGS. 1-4
As illustrated in FIGS. 1-3, a cartridge 10 embodying the invention
comprises a flexible record disk 11 suitably clamped between two
substantially identical hubs 12a,b that are secured to respective drive
plates 13a,b. The assemblage 11, 12a,b, 13a,b is rotatably disposed as a
unit within two stationary housing portions 14a,b of substantially
identical configuration. Portions 14a,b each have a flat surface 15 and
remote therefrom an irregular surface 16. The cartridge is assembled such
that the respective irregular surfaces 16 are substantially uniformly
spaced facing each other; whereas the flat surfaces 15 are at opposite
exposed sides of the cartridge.
Each surface 16 comprises a central part x surrounding the respective hub
12a,b and lying in a plane perpendicular to the axis of disk rotation.
Each surface 16 also comprises a pair of diametrically opposed generally
flat chordal parts y,z bent or creased along lines 17a,b, respectively, so
as to extend at equal acute angles .alpha., but in opposite directions
(i.e., upwardly and downwardly) from central part x.
Each housing portion 14a,b has a respective slot 18a,b through which a
magnetic recording and/or playback head 100 can access one or the other
recording surface, respectively, of the flexible disk 11. As illustrated,
head 100 is mounted on an arm 101 that is pivoted at 102; and slots 18a,b
are therefore curved to conform to the radius of arm 101. It should be
noted that the housing portions 14a,b are assembled such that line 17a of
14a overlies line 17b of 14b, and vice versa; this results from the fact
that the upper portion 14a is turned over 180.degree. left-to-right with
respect to the lower portion 14b. Consequently, slots 18a,b will be
disposed as shown in FIG. 1, and head 100 will access the lower recording
surface of disk 11 through slot 18b.
Referring now to FIGS. 1 and 4, assemblage 11, 12a,b 13a,b preferably is
secured together by a plurality of screws 19a,b. Screws 19a are inserted
from the upper side of cartridge 10, as viewed in FIG. 4; whereas screws
19b are inserted from the lower side of the cartridge. This arrangement
enables the housing portions 14a,b to be of identical configuration while
at the same time enabling connection of assemblage 11, 12a,b, 13a,b into a
unitary structure.
This assemblage is movable a limited axial distance relative to housing
portions 14a,b. The limits of such movement are defined by contact of hub
shoulder 20a or b selectively with housing shoulder 21a or b. This limited
movement enables the drive plate 13b to be electromagnetically attracted
to a magnetic chuck 22 when cartridge 10 is mounted in operative position
on a drive spindle 23, as shown in FIG. 4, said chuck being keyed to said
spindle. Note that chuck 22 draws disk 11 closer to the chordal parts y,z
of surface 16 of housing portion 14b.
Each surface 16 is preferably etched, dimpled or otherwise treated so as to
provide a roughened surface to prevent the disk from adhering to the
surface during start-up as a result of adhesive forces. Each roughened
surface 16 constitutes a Bernoulli stabilizing surface. As chuck 22
through drive plate 13b and hub 12 rotates disk 11 at high speed, air is
drawn in through apertures in the cartridge housing, as denoted by arrows
24. This causes the spinning disk to be supported on a thin (several mils)
air cushion.
In actual tests, it was found that satisfactory mechanical stability was
obtained during disk rotation if the angles .alpha. varied from 6.degree.
to 20.degree., with best results when .alpha. was equal to about 8.degree.
to 10.degree.. As illustrated, bend lines 17a,b diverge at equal acute
angles .phi. (FIG. 1) from a diametral line d. Angle .phi. will be
determined by the diameter of hub 12, but preferably is in the order of
about 15.degree.. Bend lines 17a,b should preferably intersect diametral
line e at a point within one-quarter of a diameter from diametral line d,
as shown in FIG. 1, in order to achieve good stabilization. During other
tests, when parallel bend lines were used (in lieu of the divergent lines
17a,b), it was noted that stabilization decreased as the bend lines were
moved outward a distance greater than one-quarter of the diameter of the
disk from diametral line d.
As earlier noted and as illustrated, slots 18a,b are curved to permit
access by a pivoted recording/playback head 100. Note that if the
cartridge is inserted in reversed relation onto spindle 23 by flipping the
cartridge over from left to right as viewed in FIG. 1, slot 18a will be
disposed in the same position as that in which slot 18b is shown in FIG.
1. Hence, it is possible to record on both surfaces of disk 11 and to
access either surface selectively with a single head 100.
Alternatively, radial slots may be used (in lieu of the curved slots 18a,b)
if it is preferred to move a recording/playback head radially of the disk.
Also, it should be noted that the center of the slots need not coincide
with the radius of the disk. They may, if desired, be offset from a radial
line; but, in such case, they should preferably be about halfway between a
radial line and the downturned part z when the rotational direction of
disk 11 is clockwise.
Another advantage of this reversible cartridge 10 is the fact that a servo
track (not shown) need be recorded on only one of the recording surfaces
of disk 11. Since the servo signal is of low frequency, it can be read
through the polyethylene terephthalate substrate to which the magnetizable
coatings are applied to form the record disk.
DESCRIPTION OF ALTERNATE EMBODIMENT--FIGS. 5-6
In the cartridge 10' constructed according to this embodiment, like
reference numerals but primed are used to denote parts that are similar to
those in the embodiments of FIGS. 1-4. Cartridge 10' differs from
cartridge 10 in that the surface 16' of each housing portion 14a', 14b' is
modified. Part z is eliminated and the part x' that is perpendicular to
the axis of disk rotation is enlarged to embrace the entire surface 16'
except for divergent part y'.
Tests have indicated satisfactory stability using just this single chordal
bend y' in each stabilizing surface 16', although the embodiment of FIGS.
1-4 is preferred. Note that the surfaces 16' face each other; but, as
illustrated in FIG. 6, part y' diverges downwardly from upper housing
portion 14a' and part y' diverges upwardly from lower housing portion
14b'. If mounted over the drive spindle (not shown) with portion 14b'
adjacent the head, the head will access the then lower recording surface
of disk 11 as it is rotated on the air cushion above lower surface 16'. If
the cartridge of FIG. 5 is reversed 180.degree. left to right for mounting
on the drive spindle to access the other recording surface of the disk
(which will now be the lower recording surface), it will appear exactly as
shown in FIG. 6 except that housing portions 14a' and 14b' will be
respectively below and above disk 11.
Note that thickness of cartridge 10' is reduced with the single bend
configuration. Also, with either embodiment, the bend angle .alpha. should
preferably be kept as small as possible to minimize thickness of the
cartridge 10 or 10', but just large enough to insure the required
mechanical stability for the selected disk size, hub size and rotational
speed. Also the thickness of the cartridge 10 or 10' may be reduced by
having the outer edge portions of parts y,z of surface 16 or of part y' of
surface 16' bend or curve toward the part x or x', as the case may be.
While the invention has been particularly shown and described with
reference to preferred embodiments thereof, it will be understood by those
skilled in the art that the foregoing and other changes in form and detail
may be made therein without departing from the spirit, scope and teaching
of the invention. Accordingly, the apparatus herein disclosed is to be
considered merely as illustrative, and the invention is to be limited only
as specified in the claims.
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