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BACKGROUND OF THE INVENTION
The invention related to magnetic disks and more particularly to such disks
which are thin and flexible and are disposed in protective cartridges
therefor.
A thin flexible disk rotatably disposed in a protective envelope or
cartridge has previously been proposed in U.S. Pat. No. 3,668,658 issued
June 6, 1972. The envelope is of vinyl sheet material of considerably
greater thickness than the disk, but it is still somewhat flexible; and
the envelope closely encloses the disk which is rotatable therein. A
porous wipe is disposed between the disk and the inner surfaces of the
cartridge so that, as the disk rotates in contact with the wipe, the wipe
maintains the surfaces of the disk clean as well as acting as an
anti-static agent.
Such an envelope-disk assembly may be used in a disk drive for example of
the type disclosed in U.S. Pat. No. 3,846,836, issued Nov. 5, 1974. The
disk has a central opening through it and is clamped to be drivingly
rotated by means of a tapered collet which moves through the opening of
the disk and into a hollow hub so that the disk is clamped between the
tapered collet and the hub. Such a tapered collet is not capable of very
accurately centering the disk; however, it is sufficiently accurate so
that the disk may have 48 magnetic tracks per inch (1.88 tracks per
millimeter). The disk is relatively large, being 77/8 inches (200
millimeters) in diameter.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an improved magnetic
disk-hub assembly which is so constructed that the disk is capable of a
self-centering action with respect to the hub. Still more particularly it
is an object of the invention to provide an improved magnetic disk which
has a central non-round hole through it for loosely receiving a round
drive hub portion and which has an additional hole at one side of the
central hole for receiving a drive pin, with the non-round hole being of
such configuration that the drive from the pin causes the disk to center
itself on the hub portion. It is also an object to provide a variation of
the self-centering disk arrangement wherein the hub portion is non-round
while the central hole through the disk for receiving the hub portion is
round.
It is another object of the invention to provide an improved flexible disk
and cartridge assembly in which the disk is loosely disposed in the
cartridge, with a swing door disposed on an edge of the cartridge for
closing an access opening of the cartridge through which one or more
magnetic heads may be moved. It is still a further object of the invention
to provide an improved hub assembly for mounting and driving the flexible
disk in the cartridge, with the flexible disk having the non-round hole
through which the hub assembly extends and with the hub assembly having a
drive pin extending loosely through another hole of the flexible disk as
above mentioned for centering the disk with respect to the hub assembly.
In a preferred form, the invention includes a flexible magnetic disk having
a central arrow shaped hole and a drive hole in the disk located on a
radial line extending at about 90 degrees with respect to the radial line
extending through the apex of the arrow, a rigid cartridge loosely
enclosing the flexible disk and a hub assembly on which the flexible disk
is loosely mounted. The hub assembly includes a round hub portion
extending through the arrow shaped hole and includes a drive pin loosely
extending through the drive hole in the disk so that, as the drive pin is
effective for driving the disk, the straight tapering edges of the central
hole function to center the disk with respect to the hub assembly.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is an isometric view of magnetic disk cartridge comprising upper and
lower halves and swingable dust door making the disk within the cartridge
available for upper and lower magnetic heads;
FIG. 2 is a fragmentary top plan view of the cartridge showing the door in
open position;
FIG. 3 is a top plan view of the lower cover half of the cartridge and
taken on line 3--3 of FIG. 1;
FIG. 4 is a sectional view taken on line 4--4 of FIG. 1 and showing the
upper and lower magnetic heads in position on the upper and lower surfaces
of the disk;
FIG. 5 is a sectional view on an enlarged scale and taken on line 5--5 of
FIG. 3;
FIG. 6 is a sectional view of substantially the same type as FIG. 5 and
taken on line 6--6 of FIG. 3 but with the top cover half and the disk in
place on the lower cover half to complete the cartridge and showing
dusting fabric for the disk and fixed within the cartridge;
FIG. 7 is a sectional view of the cartridge including both halves and taken
on line 7--7 of FIG. 3;
FIG. 8 is a sectional view of the cartridge including both halves and taken
on line 8--8 of FIG. 3;
FIG. 9 is a sectional view of the cartridge including both halves and taken
on line 9--9 of FIG. 3;
FIG. 10 is a longitudinal sectional view of a hub assembly for the magnetic
disk and showing in exploded relationship a drive member and a backing
member for the hub assembly;
FIG. 11 is a top plan view on an enlarged scale of a central part of the
hub assembly and taken from line 11--11 of FIG. 10;
FIG. 12 is a view similar to FIG. 10 but showing the hub assembly, drive
member and backing member together in cooperative driving relationship;
FIG. 13 is an exploded view of the disk and hub assembly and showing a top
view of the disk, a bottom view of the hub part of the hub assembly at the
top of the figure and a top view of the collar part of the hub assembly at
the bottom of the figure;
FIGS. 14 and 15 are top plan views of the magnetic disk showing the central
hub of the hub assembly in different relative positions with respect to
the disk;
FIG. 16 is a sectional view similar to FIG. 6 and showing additional
pressure applying means for the dusting fabric;
FIG. 17 is a view similar to FIGS. 6 and 16 and showing a still further
modified dusting fabric arrangement for the disk;
FIG. 18 is an exploded view of a modified disk and a modified hub assembly
and showing a top view of the disk, a bottom view of the hub part of the
hub assembly at the top of the figure and a top view of the collar part of
the hub assembly at the bottom of the figure;
FIG. 19 is a top plan view of the modified disk shown in FIG. 18 and having
a hub portion extending through the central hole of the disk;
FIG. 20 is a sectional view of an enlarged scale taken on line 20--20 of
FIG. 19;
FIG. 21 is a view similar to FIG. 3 and showing a lower cover half of a
modified form of the cartridge;
FIG. 22 is a fragmentary view similar to FIG. 4 and showing a modified hub
assembly for the disk; and
FIG. 23 is a view similar to FIG. 10 and showing the modified hub assembly
of FIG. 22 together with a modified backing member and a drive member for
engaging the modified hub assembly of FIG. 22.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring to FIG. 1 in particular, the magnetic disk cartridge 10 therein
illustrated may be seen to comprise an upper cover half 10A and a lower
cover half 10B, and these halves are fixed together by any suitable means,
such as, for example, by a suitable adhesive or by screws. A pair of flat
sided notches 12 and 14 are provided in opposite edges of the cartridge 10
by means of which the cartridge may be grasped by any suitable forceps or
the like for moving the cartridge 10 laterally. A rounded notch 16 is
provided in the same edge of the cartridge 10 as the notch 14, and notch
16 is rounded in cross-section and is adapted to receive a suitable detent
ball or roller for yieldably holding the cartridge 10 in a fixed position
in the disk drive for which the cartridge 10 is intended. An elongate slot
18 is provided in the cartridge 10 opposite the notch 16, and this is
adapted to receive a locating rib in the disk drive for properly locating
the cartridge 10 in the drive. The cartridge 10 has only one slot 18,
which is only on one edge of the cartridge, preventing it from being
loaded upside down in the disk drive.
A flexible magnetic disk 20 (see FIGS. 1 and 13) is rotatably disposed in
the cartridge 10, and an access opening 22 is provided in the front edge
of the cartridge 10 for receiving a pair of magnetic heads 24 and 26 (see
FIG. 4). The heads 24 and 26 may be suitably mounted on spring support
arms 28 and 30, for example, and these may be moved in unison in direction
A in order to move the heads 24 and 26 radially on disk 20. Any suitable
means may be provided for moving heads 24 and 26 off of or into contact
with the disk 20 once the heads 24 and 26 have entered the opening 22.
A dust door 32 (see FIGS. 1-3) is swingably mounted on a shaft 34 extending
into and through the cover halves 10A and 10B, and a torsion spring 36
extends around shaft 34. The spring 36 has one end fixed with respect to
the cartridge 10 and has its other end embedded in the door 32 so that it
tends to swing the door 32 into a closed position in which the door closes
the access opening 22 for thus shielding the disk 20.
The disk 20 is disposed on a hub assembly 40 (see FIGS. 4 and 10), and the
hub assembly 40 protrudes into a central opening 42 in the upper cover
half 10A and into a central opening 44 in the bottom cover half 10B. As
will be noted from FIG. 4, the opening 44 in the cover half 10B is
slightly smaller in diameter than the opening 42 in the top cover half
10A.
The bottom cover half 10B, as will be seen from the plan view of this cover
half in FIG. 3, has a plurality of radially extending internal ribs 46,
48, 50, 52, 54, 56 and 58. In addition, the bottom cover half 10B has
sidewardly extending internal ribs 60 and 62, and these form a half of the
access opening 22. In this connection, the lower magnetic head 26 and its
support 30 is shown in FIG. 3 within the opening 22.
The rib 46 as shown in FIG. 5 is formed with a V-shaped slot 64 in its
upper edge. A piece 66 of flexible Mylar (registered trademark of E. I.
dePont de Nemours & Co.) film or the like is disposed in slot 64, and a
thickness of porous fibrous paper wipe 68 is disposed on top of the film
66. The wipe 68 and the film 66 are fixed within the slot 64 to the rib 46
by any suitable means, such as by heat welding; and, when the bottom cover
half 10B is divorced from the upper cover half 10A, the film 66 and wipe
68 extend upwardly in the form of a V as is shown in FIG. 5.
A wipe 69 (see FIG. 3) similar to the wipe 68 and also supported by a piece
of Mylar film is fixed to the rib 54 in the same manner as the wipe 68 is
fixed to the rib 46, using heat welding and the same type of V-shaped slot
as shown in FIG. 5. The other radial ribs 48, 50, 52, 56 and 58 serve
mainly to strengthen the bottom cover half 10B.
It may be noted that the top and bottom cover halves 10A and 10B are mirror
images of each other except for the fact that the central holes 42 and 44
are different diameters as previously noted and except for the existence
of the slot 18 which is only in the bottom cover half 10B. With the top
and bottom cover halves 10A and 10B being assembled as shown in FIG. 1,
therefore, there are internal ribs in the top cover half 10A in exact
alignment with the ribs 46-62 previously described in connection with the
bottom cover half. Two such ribs 70 and 72 within the upper cover half 10A
are shown in FIGS. 6 and 7 which depict the cartridge in assembled
condition.
The rib 70 shown in FIG. 6 carries a porous paper wipe 74 anchored with
respect to the rib 70 in the same manner as the wipe 68 is anchored to the
rib 46 and backed by a piece of flexible film identical with the film 66
shown in FIG. 5. The Mylar film piece 66 and the corresponding film piece
supporting the wipe 74, as well as the wipes 68 and 74 themselves, are
bowed in shape by reason of being in contact with the disk 20 in the
assembled condition of the cartridge 10 as shown in FIG. 6. The wipe 69
and the corresponding wipe carried by a rib in the upper cover half 10A
located opposite the rib 54 also are bowed in the same manner as shown in
FIG. 6 so that these wipes are in contact with the disk 20. This bowing is
against the inherent resilience of the pieces of Mylar film so that the
wipes 68 and 74, for example, bear with resilient pressure on opposite
faces of the disk 20. The other radially extending ribs, such as the ribs
50 and 72, are spaced from each other and from the disk 20 as is
illustrated in FIG. 7.
Referring to FIGS. 8 and 9, it will be observed that the rib 62 has a
terminating portion 62a of increased height, and the corresponding rib 76
of the top cover half 10A has a corresponding portion 76a of increased
height. The rib portions 62a and 76a thus form a relatively narrow slot 78
for receiving the edge of the disk 20. The rib 60 likewise has an
increased height portion 60a, and the rib 60 and the corresponding rib of
the top cover half 10A thus provide a slot of the same type as the slot 78
for likewise receiving the marginal edge of the disk 20. The disk 20 is
thus guided at the sides of the access opening 22 quite accurately in a
median position, equally spaced from the adjacent inner surfaces of the
cover halves 10A and 10B forming the major surfaces of the access opening
22.
The hub assembly 40 is shown in detail in FIGS. 4 and 10 in particular and
may be seen to comprise a hub 80 and a collar 82 positioned on the hub 80.
The hub 80 is formed with a conical central cavity 84 disposed mainly in
an upwardly extending hub portion 86 as the assembly 40 is shown in these
figures and is formed with a cylindrical central opening 88 connected with
the opening 84 and disposed mainly in a downwardly depending hub portion
90. Three round tapered bosses 92 (see FIG. 11) extend upwardly from the
hub portion 86, and the inner surfaces of the bosses 92 are substantially
in correspondence with the outer upper edge of the opening 84. Three
smaller round bosses 94 extend upwardly from the hub portion 86 and are
interspersed between the bosses 92, and the bosses 94 have their outer
surfaces substantially in correspondence with the outer surface of the hub
portion 86.
The collar 82 has three rivet portions 96 extending through three
corresponding holes 98 formed in the hub 80. The hub 80 is provided with
an annular boss portion 100 surrounding each of the holes 98, and the
rivet portions 96 are formed over the hub 80 so as to tightly hold the
collar 82 in contact with the portions 100 for fixing the collar 82 and
hub 80 together. Due to the existence of the boss portions 100, the collar
82 and hub 80 have a gap 102 between them, and the disk 20 is disposed in
the gap 102. The disk 20 (see FIG. 14) has three openings 104 through it
for receiving the boss portions 100, and the openings 104 are slightly
greater in diameter than the diameters of the boss portions 100 so that
the disk 20 may move slightly radially with respect to the hub 80 and boss
portions 100. The thickness of the gap 102 is slightly greater than the
thickness of the disk 20 so that the disk 20 may also have a slight
movement axially with respect to the hub 80.
The hub 80 is provided with a lug portion or pin 106 that extends
downwardly as the assembly 40 is shown in FIG. 10 and into a slot 108 in
collar 82 that is substantially greater in size than the lug portion 106
so that the lug portion 106 is out of contact with the faces of the collar
82 forming the sides of the slot 108. The disk 20 as seen in FIG. 14 has
an opening or hole 110 through which the lug portion 106 extends, and the
lug portion 106 has a flat driving face 106a which coacts with a flat edge
110a of the hole 110 which functions as an abutment for driving the disk
20.
The disk 20 is provided with a center opening or hole 112 through which the
hub portion 90 extends (see FIG. 14). The hole 112 is arrow shaped and has
two straight sides 112a and 112b adapted to contact the hub portion 90
which is round, and the sides 112a and 112b extend at an angle .alpha.
with respect to each other. The angle .alpha. may, for example, be 60
degrees and may well be in the range of 75 degrees .+-. 45 degrees. The
apex b of the angle .alpha. is located on a radial line c extending
through the center of disk 20 which is disposed at an angle .beta. of
preferably 90 degrees or thereabouts with respect to a radial line d of
the disk 20 extending through the edge 110a of hole 110, as shown in FIG.
14.
The hub assembly 40 and thus the disk 20 are driven from the rotatable
drive member or spindle 114 (see FIG. 10), and the hub assembly 40 is held
in forceful contact with the drive member 114 by means of a backing member
116. The drive member 114 is rotatably disposed in a bearing 118 and is
rotatably driven from any suitable prime mover (not shown). Suitable
supporting structure for bearing 118 and drive member 114 is provided so
that member 114 remains fixed from lateral movement with respect to the
longitudinal center line e of the drive member 114 as member 114 is
driven. The drive member 114 has a conical forepart 120 which fits in the
conical cavity 84 in the assembly 40 as is indicated in dotted lines by
the reference numeral 120a. The forepart 120 is slightly less tapered than
the walls of the cavity 84 so that the forepart 120 engages the walls of
the cavity at the extreme end of the forepart substantially in the plane
of the disk 20. This construction assures that the disk is exactly
centered with respect to center line e even though manufacturing
tolerances militate against a perfect fit of tapered forepart 120 in
conical cavity 84.
The forepart 120 of the drive member 114 is provided with a circumferential
groove 122, and a rubber O-ring 124 is disposed in the groove 122 and
extends slightly outwardly from the exterior surface of the forepart 120.
When the forepart 120 of drive member 114 is fully positioned within the
conical cavity 84 and is in its dotted line position 120a, the O-ring 124
is slightly compressed by the bosses 92 and therefore forms a driving
connection between the drive member 114 and the hub portion 86.
The backing member 116 includes a disk portion 126 adapted to bear on the
lower surface of the hub 80, and the backing member 116 has a tapered boss
128 which enters the opening 88. Rotation of the backing member 116 is
permitted by means of a bearing 130 in which the backing member 116 is
disposed, and a spring 132 is disposed between the bearing 130 and a frame
member 134. A retaining washer 136 is fixed on the lower end of the
backing member 116 as it is illustrated in FIG. 10 and prevents the
backing member 116 from separating from the frame member 134. It will be
observed that there is a gap between the backing member 116 and the
opening through the frame member 134 through which the backing member 116
extends so that there can also be a slight lateral movement of the backing
member 116 with respect to the frame member 134.
When the cartridge 10 is in its free condition, outside of a disk drive
containing the drive member 114 and backing member 116, the spring 36
holds the dust door 32 in closed position (as shown in dotted lines in
FIG. 2). The door 32 thus closes the access opening 22 of the cartridge
and seals the disk 20. The cartridge 10 and particularly its cover halves
10A and 10B is made from a hard tough material, such as polycarbonate, and
the cartridge and particularly the cover halves thus provide protection
for the disk 20 which is relatively fragile. More particularly, the disk
20 may be of polyethylene terephthlate, such as of 0.003 inch (0.0762mm)
thickness, being a so called "floppy" disk which has many advantages but
is relatively flexible, flimsy and easily damaged. The door 32 when in
closed position prevents dust from collecting on the surfaces of the disk
20 and prevents any fingering of the disk 20 which would leave finger
marks, preventing effective subsequent magnetic reading or writing on the
disk. The hub assembly 40 effectively positions the disk 20 in the
cartridge 10 so that the edges of the disk 20 cannot come into contact
with any internal surfaces of the cartridge 10. The hub portion 90 fits
loosely within the opening 44 in the bottom cover part 10B and prevents
only a limited sideward movement of the hub assembly 40 and disk 20 with
respect to the bottom cover part 10B. The hub portion 86 and particularly
the bosses 94 may contact the sides of the hole 42 in the top cover part
10A and thus limit the sideward movement of the hub assembly 40 and disk
20 to a limited distance with respect to the top cover part 10A. Also, it
will be observed from FIG. 4 in particular that the axial movement of the
hub assembly 40 is limited in the cartridge by the collar 82 contacting an
adjacent inner surface of the bottom cover half 10B and by the hub 80
contacting an adjacent inner surface of the top cover half 10A. Thus, an
axial push on the hub assembly 40 will not allow a strain to be put on the
disk 20 or a radial push on the hub assembly 40 will not allow damage to
the periphery of the disk 20. The cartridge 10 with the disk 20 therein
may thus be stored, handled and moved about with the disk 20 being
protected from damage throughout.
The cartridge 10 having the disk 20 therein may be moved into a disk drive
(not shown) by utilizing forceps (not shown), for example, entering the
notches 12 and 14 so as to slide the cartridge 10 moving in direction D as
shown in FIG. 1 into the disk drive. It is contemplated that the disk
drive preferably shall have a stationary rib for entering the slot 18, and
the rib as the cartridge 10 is moved in direction D into the disk drive,
shall contact the short end 32a of the door 32 so as to pivot the door 32
into its open position in which it is shown in full lines in FIG. 2. The
dust door 32 thus opens the access opening 22 when the cartridge 10 is
thus positioned in a receiving disk drive. It is contemplated also that
the disk drive shall preferably have a spring loaded detent ball or roller
entering the cavity 16 and holding the cartridge 10 in its fully loaded
position within the disk drive.
The disk drive also includes the magnetic heads 24 and 26 on their spring
support arms 28 and 30 (see FIG. 4) which may move in direction A into the
access opening 22 after the cartridge 10 has been moved into final
position in the disk drive. The magnetic heads 24 and 26 are spaced with
respect to each other and then may be moved into contact with the disk 20
by any suitable mechanism. The increased height rib portions 62a and 76a
(see FIG. 8) forming the slot 78 on one side of the access opening 22 and
the corresponding increased height rib portion 60a and its corresponding
rib portion carried by the top cover half 10A hold the disk 20 within
close limits with respect to a median position in the access opening 22 so
as to assure that the heads 24 and 26 do not abut the peripheral edge of
the disk 20 as the heads 24 and 26 are moved into the access opening 22.
With the cartridge 10 thus being in position in the disk drive, the
cartridge 10 and backing member 116 may be moved in direction C so that
the forepart 120 of the drive member 114 fits in the conical cavity 84 and
so that the part 126 of the backing member 116 is in spring pressed
abutment with the lower surface of the hub 80. The spring pressed backing
member 116 thus firmly holds the tapered forepart 120 of the drive member
114 in the cavity 84 and causes a continued indentation of the O-ring 124
by the bosses 92 so that the O-ring 124 and bosses 92 form a non-slip
driving connection from the drive member 114 to the hub assembly 40. The
drive member 114 is then rotatably driven from its prime mover and thus
drives the hub assembly 40 and disk 20. The hub assembly parts are then in
their FIG. 12 positions.
When the disk 20 is rotatably driven by the hub assembly 40, the opposite
wipes 68 and 74 (see FIG. 6) are in friction contact with the disk 20. The
same is true of wipe 69 (see FIG. 3) on the rib 54 and the wipe carried by
the top cover part 10A located opposite the wipe 69. These wipes thus
function as mechanisms for removing and wiping off contaminants from the
disk 20 and capturing these contaminants. The wipes have low friction with
respect to the disk 20, but they are held in bearing contact with the disk
20 due to the action of the resilient Mylar backing 66 for the wipe 68 and
the corresponding Mylar backings for the other wipes. These wipes (68,
68a, 74 etc.) therefore also act as means restraining the rotation of the
disk 20 to some slight extent. Likewise, the magnetic heads 24 and 26 when
they are in contact with the disk 20 for a magnetic reading or writing
action also to some extent restrain the rotation of the disk 20. For these
purposes, it is preferred that the wipes shall be of a porous low friction
fibrous material such as, for example, the dusting fabric which is
manufactured by the Kendall Company of Boston, MA. and is designated H854,
Novonette #1. Obviously other wipes may be used, such as, for example, the
3M 550 wipe made by the Minnesota Mining & Manufacturing Company,
generally known in the art as "pink wipe". Although the use of Mylar
backing 66 for the wipe 68 and the corresponding Mylar backings for the
other wipes is preferred, these backings may be omitted. In this case, the
wipes 68 etc. are directly fastened within the V-shaped groove 64 and the
corresponding grooves in the other ribs of the cover halves 10A and 10B
carrying the other wipes. Generally the wipes without such Mylar backings
are sufficiently resilient so as to continue to bear on the disk 20 as it
rotates, functioning in the same manner to capture contaminants from the
disk and to slightly restrain the disk in its rotation.
As has been previously described, the boss portions 100 (see FIG. 10) fit
loosely within the disk openings 104, and the lug portion 106 fits loosely
in the disk opening 110. Also, it can be expected that the edges 112a and
112b of the opening 112 are not in contact with the hub portion 90
initially. Therefore, under these conditions, even though the hub assembly
40 and particularly the hub 80 is held in fixed centralized location with
respect to the drive member 114 due to the action of the tapered forepart
120 acting on the walls of the conical cavity 84, the disk 20 will not be
centralized in fixed position laterally with respect to the fixed center
line e of the drive member 114.
The disk 20 is accurately centered with respect to the drive member 114
when the acutely extending hole edges 112a and 112b are both in contact
with the round hub portion 90; and the lug portion 106 of the hub 80, in
turning the disk 20 against the restraining action of the wipes 68, 69, 74
etc. and against the restraining action of the magnetic heads 24 and 26,
causes the disk 20 to shift laterally to move both of edges 112a and 112b
into contact with the hub portion 90. In this movement of the disk 20, one
or both of the edges 112a and 112b may slide on the round periphery of the
hub portion 90; and the edges 112a and 112b and the periphery of the hub
portion 90 thus act as camming surfaces in this action. With the edges
112a and 112b thus both being moved into contact with the hub portion 90,
the disk 20 is then centralized with respect to the hub assembly 40 and
also with respect to the longitudinal center line e of the drive member
114.
FIGS. 14 and 15 may be referred to for an understanding of the manner in
which the lug portion 106 of the hub 80 moves the disk 20 laterally to
move both hole edges 112a and 112b into contact with the hub portion 90 so
as to thereby center the disk 20. The disk 20 is rotated in the direction
E shown particularly in FIG. 14, and initially the lug portion 106 of the
hub 80 may be assumed to be out of engagement with the sides of the hole
110 in the disk 20 and the hole edges 112a and 112b may be assumed to be
out of contact with the hub portion 90 as shown in FIG. 15. As the lug
portion 106 rotates along with the hub assembly 40 from the drive member
114, the restraint on the disk 20 due to the wipes including the wipes 68,
69, 74 etc. and due to the magnetic heads 24 and 26 in contact with the
disk 20 is opposite to direction E. The head 24 is shown in FIG. 14, and
the force F of restraint due to head 24 is shown in this figure. At this
time, the lug portion 106 and particularly its flat surface 106a moves
into contact with the flat edge portion 110a of the hole 110 in the disk
20, and the resultant of the force applied by the lug portion 106 on the
disk 20 and of the restraint in the direction F provided by the magnetic
heads 24 and 26 is a force in the direction G shown in FIG. 14. Since the
force in the direction G is nearly diametrically opposite the apex b in
the disk 20, the disk 20 shifts laterally until its hole edges 112a and
112b are in contact with the round hub portion 90 as shown in FIG. 14.
The head 24 is shown in FIG. 14 substantially on the same radial line d as
the engaging surfaces 106a and 110a, and it will be apparent that the
result of the force by the lug portion 106 and the restraining force by
the heads 24 and 26 is a couple which acts in the direction G to move the
hole edges 112a and 112b into engagement with the hub portion 90. The
restraining effect of the heads 24 and 26 acting in conjunction with the
propelling effect by the lug portion 106 rotating in direction E varies
from translation in the direction G to couples tending to move disk 20 in
the direction G or to engage one or the other of the hole edges 112a and
112b with hub portion 90 and tending to move the disk 20 along these edges
on hub portion 90 toward the apex b, depending on the position of the
heads 24 and 26 at the time with respect to the lug portion 106. Although
the restraining effect of the heads 24 and 26 has just been specifically
referred to, the restraining effect of the wipes 68, 69, 74, etc. on the
disk 20 in centralizing the disk 20 with respect to the hub portion 90 is
the same as for heads 24 and 26, and it will be apparent that the
centralizing effects of the heads 24 and 26 and of the wipes 68, 69, 74,
etc. are all simultaneously operative and cumulative for this purpose. The
wipes 68, 69, 74, etc. are fixed radially with respect to the center of
the disk 20, while the heads 24 and 26 may move inwardly and outwardly
radially of the disk for reading and writing on the various magnetic
tracks of the disk so that the heads are not effective on the same radius
of the disk all of the time. It is important, however, that the restraint
on the disk 20 be provided at a greater radius of the disk than that at
which the lug portion 106 is disposed in order to provide the translation
and couples just described; and the wipes 68, 69, 74, etc. are located at
greater radii than the lug portion 106, and the same is true of the heads
24 and 26, although the radius at which the heads 24 and 26 are located
varies.
The angle .alpha. at which the hole edges 112a and 112b extend with respect
to each other may vary while still obtaining the disk centralizing action
as above described. The lower limit of the angle .alpha. cannot be exactly
defined and is dependent upon the strength of the material of the disk 20.
Making the angle .alpha. quite small will tend to cause the disk 20 to be
split as the disk 20 is moved in direction G and will also tend to cause
ripples in the disk material at the edges of the hole 112. If the disk 20
is constructed of Mylar of 0.003 inch (0.0762mm) thickness, a good lower
limit for the angle .alpha. can be expected to be about 30 degrees. A
useable upper limit for the angle .alpha. can be that angle at which any
of the restraints on disk rotation, due to the wipes 68, 69, 74, etc. or
due to the heads 24 and 26, tends to cause the hole edges 112a and 112b to
move in a direction opposite to the direction G for any particular
rotative position of the disk 20 with respect to the particular restraint.
The angle .alpha. using this criteria, could have an upper limit of 120
degrees. It will be understood, however, that the restraints on disk
rotation by the wipes 68, 69, 74, etc. and the heads 24 and 26 are
cumulative, and therefore the resultant cumulative action may actually
have a resultant tending to move the disk to engage hole edges 112a and
112b with hub portion 90 and hold them in engagement even though the
effect of one of the restraints is the opposite (with less than optimum
choice of angles .alpha. and .beta.).
The optimum angle .beta. of the radial line d passing through the hole
drive edge 110a and measured from the radial line c passing through the
apex b is 90 degrees (see FIG. 14), and this is in the direction of
rotation E of the disk 20. An analysis indicates that the angle .beta.
between the radial lines d and c should preferably be close to this value.
The extent to which the angle .beta. of 90 degrees may well be changed
will depend on the coefficients of friction between the materials of the
disk 20 and the hub portion 90.
Due to the accuracy with which the disk 20 is centered with respect to the
center e of the drive member 114, the track density radially of the disk
may be high. For example, 125 tracks per inch (4.92 tracks per millimeter)
are recordable on a disk 20. This compares with 48 tracks per inch (1.88
tracks per millimeter) recordable in previous "floppy" disks which were
not centered with the same accuracy as is obtained using the present
invention. Not only can the number of tracks per inch or per millimeter
radially be increased, but the recording densit | | |
