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Description  |
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BACKGROUND
This invention provides a disk memory that seats a memory disk with a
consistent high accuracy by a drive chuck that engages only one side of
the disk. Features of the invention reside in the driven hub of the disk
and in the drive chuck.
The invention also provides a unique attachment of the storage medium of
the disk to the disk hub. The attachment eases the elastic deflection of
the disk, as conventionally occurs upon read-write engagement with the
transducer head.
Conventional disk drives, particularly for flexible magnetic media often
termed "floppy disks", engage the center of the disk from opposite sides
to position the disk and to rotate it. Consistent accurate positioning of
each disk is required to attain proper read/write interaction with the
transducer head and to attain correct track location and density.
Floppy disks traditionally are relatively large, with a diameter of either
five inches or eight inches. There is now a need for equally high
performance disk memories with significantly smaller disks, particularly
with a diameter under four inches. Conventional practices for mounting,
locating and driving the magnetic medium of a floppy disk are not readily
applied to such smaller disk memories.
It accordingly is an object of this invention to provide disk memory
apparatus that locates a memory disk with consistent high accuracy by
engaging only one side of a memory disk.
A further object of the invention is to provide apparatus which attains
such location of a disk in both the radial, i.e. lateral, and the vertical
directions.
Another object of the invention is to provide disk-locating memory
apparatus of the above character which attains repeatable indexing of
different disks, as desired to use the full track capacity of the
recording medium.
It is also an object of the invention to provide disk memory apparatus of
the above character which is highly reliable and low in cost, and further
which is well suited for use with memory disks of small size.
It is a further object of this invention to provide a magnetic memory disk
in which the recording medium is relatively free to deflect from the disk
hub, as desired for transducer head penetration at recording tracks close
to the disk center.
Other objects of the invention will in part be obvious and will in part
appear hereinafter.
CROSS REFERENCE TO OTHER APPLICATIONS
This application incorporates by this reference the disclosure in the
commonly assigned and copending applications for patent Ser. Nos. 444,612
and 444,611 entitled "Disk Drive" and "Anti-Backlash Nut and Head
Positioner", respectively, filed on even date herewith and both now
abandoned.
SUMMARY OF THE INVENTION
A disk memory according to the invention operates with a recording disk
having a central hub with a central aperture for receiving a spindle of
the disk drive. The spindle-receiving hub aperture is defined in part by a
pair of precisely-located flat surfaces which define between them an
included angle of less than 180.degree.. The flat surfaces thus define
between them a vee-shaped saddle. The bisector of the included angle
between the flat surfaces has a selected orientation on the disk hub.
The annular surface of the disk hub radially outward of the
spindle-receiving aperture has a recess therein which receives further
elements of the disk drive for accurately locating the disk relative to
the drive elements, as well as for spinning the disk. The recess in the
disk hub extends circumferentially, from a first end thereof in the
direction of disk rotation to a second end that is selectively located
relative to the flat surfaces of the spindle-receiving hub aperture. This
second end of the hub recess includes a rotational driving surface that
extends substantially radial on the hub. The radially inner side of the
recess extends between the first and second circumferentially spaced ends
of the recess at not greater than a first radial distance from the
spindle-receiving aperture. The outer radial side of the recess is formed
with at least three circumferentially successive sections. The first such
section, commencing at the first circumferential end of the recess, is
spaced from the spindle-receiving aperture at not less than a second
radial distance which exceeds the first radial distance. The second such
surface section is a radial camming surface aligned at a progressively
radially decreasing distance from the aperture between the second distance
and a lesser third distance which is still greater than the aforementioned
first distance. The third section of this surface, which typically extends
to the second end of the recess, is spaced from the spindle-receiving
aperture by a distance close to the aforementioned third distance,
particularly relative to the second distance, but preferably not less than
the third distance.
The second circumferential end of the recess is located relative to the
angle bisector such that a rotational drive force applied to the second
circumferential end of the recess, and a radially outward positioning
force applied to the third section of the outer side of the recess,
produce a resultant force that is oriented longitudinally and preferably
parallel to that bisector. Further, the resultant force is directed away
from the apex of the bisected angle.
With this arrangement, the noted resultant force moves the memory disk
relative to the disk drive to maintain both flat surfaces in the disk
aperture seated against the drive spindle. That is, the structure of the
disk hub is such that the disk hub receives from the disk drive a
resultant force that not only spins the disk, but presses the vee-saddle
of the hub aperture firmly against the drive spindle, thereby reliably
locating the disk radially relative to the driving spindle.
A further feature is that the third, i.e. forwardmost, section of the outer
surface of the recess in the disk hub preferably is slightly angled in the
direction of increasing radial distance. Hence movement along this surface
section in the direction of hub rotation is to slightly greater radial
distances from the center of the hub. With this geometry, a
radially-outward force exerted on this surface section has a component
directed opposite to the direction of disk rotation. This is desired to
attain consistent proper indexing of disks by consistently maintaining the
disk-rotating drive element firmly seated against the rotational driving
surface of the disk hub.
A disk memory according to the invention further has a drive chuck for the
accurate positioning and rotational drive of a disk having a hub
structured as stated above. The drive chuck includes a precision located
spindle of circular cross section and relative to which the disk is to be
positioned. The drive chuck preferably retains the disk hub firmly seated
thereto by means of a permanent magnet structure in the drive chuck and a
magnetically soft material in the disk hub. The drive chuck has a driven
member radially spaced from the spindle for projecting into a recess of
the disk hub and imparting a circumferentially-directed rotational driving
force thereto. The drive chuck further includes a radially-biasing member
that imparts a selected radial force to the hub. For use with the
foregoing disk hub, the drive member is spaced from the drive spindle at
between the stated first and third radial distances. The bias member is
normally within the stated second radial distance and is movable radially
inward to be within the stated third distance.
This bias member preferably projects into a recess in the hub and engages
the outer side of the recess. This engagement exerts on the disk hub a
radially-outward force which is independent of the
circumferentially-directed rotational drive force which the drive member
imparts to the hub. The bias member preferably is movable radially with a
resilient radially-outward bias. The bias member accordingly can engage a
camming surface section of the hub recess and slide along that surface to
progressively cam the disk toward the desired location.
In the illustrated preferred embodiment, after traversing the full length
of this camming surface, due to the rotational movement of the drive chuck
relative to a disk, the bias member progresses to engage further surface
section of the hub where it continues to apply the radially-directed
locating force. The bias member is, however, essentially free to slide
along this further surface section until the drive member mounted with it
on the drive chuck engages a circumferential end of the hub recess and
thereupon commences rotating, i.e. spinning, the disk in tight direct
coupling with the drive chuck. The engagement of the bias member with the
further surface section of the hub recess preferably is arranged to
maintain the chuck drive member in contiguous driving abutment with the
hub recess, as desired.
A further feature of the invention is that a selectively compliant web is
adhered to the recording medium of the disk and to the disk hub for
securely joining them together. This attachment is effective essentially
at the inner edge of the recording medium, and the disk hub extends
radially out beyond that edge for positionally supporting a radially
larger annular portion of the medium. The recording medium hence is free
to deflect elastically from this underlying portion of the disk hub, to
which the recording medium is not attached. A magnetic recording head,
i.e. a read/write transducer, bears against a flexible recording medium
sufficiently to produce such an elastic deflection, which commonly is
termed "head penetration". Hence this relatively unrestricted elastic
deflection of the recording medium adjacent the location of inner
recording tracks is desired to enhance the utility and the locational
precision of recording tracks close to the center of the disks.
The invention accordingly comprises the several steps and the relation of
one or more of such steps with respect to each of the others, and the
apparatus embodying features of construction, combinations of elements and
arrangement of parts exemplified in the following detailed disclosure and
which effects such steps, and the scope of the invention is indicated in
the claims.
BRIEF DESCRIPTION OF DRAWINGS
For a fuller understanding of the nature and objects of the invention,
reference should be made to the following detailed description and the
accompanying drawings, in which:
FIG. 1 shows a disk memory embodying features of the invention;
FIG. 2 shows the disk memory of FIG. 1 with the circuit board removed, with
the memory disk removed, and with the receiver in the unseated position
ready for loading a memory disk into the disk memory;
FIG. 3 is a simplified transverse sectional view of the disk drive of FIG.
1, along section line 3--3 thereof;
FIG. 4 is a top plan view of the drive chuck of the disk drive of FIG. 1;
FIG. 5 is a transverse cross section of the drive chuck of FIG. 4 taken
along line 5--5 thereof;
FIG. 6 is a fragmentary plan view of a memory disk according to the
invention;
FIGS. 7A, 7B and 7C show different sequences in the positioning of a memory
disk onto a drive chuck in accordance with features of the invention; and
FIGS. 8 and 9 show a memory disk having a recording medium attached to a
hub in accordance with features of the invention.
DESCRIPTION OF ILLUSTRATED EMBODIMENTS
A disk memory 10 according to the invention has, as FIGS. 1 and 2 show, a
chassis 12 which mounts a motor 14. The motor has a spindled chuck 18 on
which a memory disk 16 seats and which imparts both locating and driving
forces to the disk. The chassis 12 also mounts a transducer unit indicated
generally at 20 which includes a head-carrying carriage 22 which a
positioning drive 24 selectively positions by means of a lead screw 26 and
follower nut 28. A receiver 30 is movable on the chassis between a seated
position shown in FIG. 1 and an unseated position shown in FIG. 2. The
receiver when seated carries a memory disk 16 to be positioned and driven
by way of the motor chuck 18 and to be engaged for read/write information
transferring operation by the carriage-carried recording head. In the
unseated position of the receiver 30, the carriage 22 releases its
engagement with a disk and the memory disk thereon is lifted free of the
spindled motor chuck 18.
FIG. 3 shows that the illustrated spindled chuck 18 is carried on a motor
shaft 32 assembled directly with the chassis 12 by way of bearings 34, 34.
The spindled chuck 18 is at one end of the motor shaft 32, above the
chassis platform 36. At the other, lower end of the motor shaft is a
flange-mounted rotor 38. The illustrated motor stator 40 also is
separately mounted directly to the chassis 12, as shown.
The spindled chuck 18, shown in FIGS. 4 and 5, has a casing 42 secured on
the motor shaft 32 adjacent the shaft upper end. The shaft extends beyond
the casing to form a spindle 44 of circular cross section. The illustrated
casing 42 is essentially a circular wheel with inner and outer annular
rims 42a and 42b, the edges of which form a planar chuck face 18a on which
the hub of a storage disk seats, as appears in FIG. 1. The annular channel
which the casing 42 defines between the rims 42a and 42b mountingly seats
a permanent magnet 46, a disk rotating drive pin 48, and a positioning
mechanism 50. The upper surface of the illustrated permanent magnet is
substantially coplanar with the casing rims.
The drive pin 48 is fixed to the casing 42, illustratively between the
inner and outer rims thereof, and projects a cylindrical stem outward
beyond the planar chuck face 18a by at least several thousandths of an
inch in order to seat in a recess in the hub of a disk seated on the
chuck.
The illustrated disk positioning mechanism 50, which operates with a motor
14 (FIGS. 1 and 3) which applies clockwise drive (FIG. 4) to the chuck 18,
has a resiliently-acting radially biasing cam 52 pivotally seated on a
post 54. The post is fixed to the casing at the floor of the channel and
extends parallel to the drive pin 48, which is parallel to the spindle 44
and hence to the motor shaft 32.
The illustrated cam 52, which seats fully within the casing channel except
for a projecting tab 56, has a bifurcated forward end formed with arms 58
and 60 that fit on either side of the drive pin 48. The tab 56 extends
from the arm 58 transverse to the chuck face 18a, from which it projects
to engage the hub of a disk. The cam has a first moment arm, as viewed in
FIG. 4, between the tab 56 and the axis of rotation on the post 54. A
second moment arm extends transversely to the first between the axis of
rotation on post 54 and the force which a compression spring 62 imposes on
the cam. The spring is seated on a locating pin 64 projecting rearwardly
from the body of the cam 52 and is compressed between the rotationally
back end of the cam 52 and a spring seat formed by one edge of the magnet
46 and the inner wall of the casing outer rim 42a, as shown in FIG. 4. The
compressed spring 62 urges the cam 52 to rotate in a counter-clockwise
direction about the post 54. This rotation, however, is limited in at
least one instance by the abutment of the cam arm 60 with the drive pin
48, as appears in FIG. 4. In this illustrated position of the mechanism
50, the arm 60 is spaced radially outward of the inner rim 42a. The cam
accordingly is free to rotate clockwise from the position shown in FIG. 4,
against the bias of the spring 62. Such clockwise rotation of the cam
stops when the cam arm 58 abuts the drive pin 48.
The memory disk 16 for operation with the spindled chuck 18 has, as FIG. 6
shows, a relatively thin disk-like annulus 70 of stiffly-flexing magnetic
recording material which can be similar to those conventional used in
magnetic floppy disks, and a hub 72. The illustrated disk 16 is of
unusually small size wherein the recording annulus 70 has a circular outer
circumference of three and one-quarter inch diameter and it has a central
opening, illustratively circular, with a diameter in the order of one-half
inch.
The illustrated preferred hub 72 is a flat disk of magnetically soft
material such as ferretic stainless steel for magnetic attraction to the
permanent magnet 46 of the drive chuck 18 (FIGS. 4 and 5). The hub is
centrally apertured with a spindle seating aperture 74 of circular cross
section except for two flat surfaces 76 and 78. The two flat surfaces are
angled relative to one another to form an included angle between them of
less than 180.degree., thereby to form between them a precisely located
vee-shaped saddle. The bisector 80 of the included angle between the flat
surfaces 76 and 78 has a selected orientation on the disk hub, as
described below. The diameter of the circular portion of the disk aperture
74 can be significantly larger than the diameter of the chuck spindle on
which it seats, thereby facilitating placement of the disk 16 onto the
spindled chuck as appears in FIG. 1.
With further reference to FIG. 6, the disk hub 72 has a positioning and
driving recess indicated generally at 82. The illustrated recess extends
fully through the disk for convenience of manufacture. The illustrated
recess has an arcuate length, i.e. extends circumferentially, along the
direction in which the disk is rotationally driven from a load end 82a to
a drive end 82b. The side of the recess forming the load end 82a is
illustrated as a straight line extending parallel to a radius which passes
through the recess. The side of the recess which forms the drive end 82b
includes a flat surface aligned along a radius 86, as shown. The radially
inner side 82c of the recess is spaced by at least a first radial distance
from the center of the hub and preferably is an arc of constant radius.
The remaining side of the illustrated recess 82, i.e. the radially outer
side, has three circumferentially contiguous sections 82d, 82e and 82f.
The surface section 82d, extending from the load end 82a, can be straight
as shown, or arcuate, and is located at a radius in excess of a selected
second value. The surface section 82e provides a radially inward camming
action. For this purpose, it preferably is straight as illustrated and
extends radially inward from the second radial value at the juncture with
the surface section 82d to a third radial value less than the second value
but greater than the first value, as illustrated. The foregoing dimensions
of the recess 82 are selected such that the drive pin 48 and bias tab 56
of the spindled chuck 18, FIGS. 4 and 5, fit freely within the recess at
the load end 82a, and that the tab 56 engages the surface section 82e with
a camming engagement. Further, the drive pin and the bias tab, when the
cam 52 of the chuck 18 is rotated clockwise from the position of FIG. 4,
fit within the relatively narrow drive end 82b of the recess.
As further shown in FIG. 6, the third, outer surface section 82f of the
recess 82 extends from the camming surface section 82e to the drive end
82b of the recess. This surface section can, as illustrated, be flat and
oriented to be essentially at the third radial distance from the center of
the hub. More particularly, this surface section preferably is at a radial
location not less than the third value and instead extends slightly
radially outward, e.g. is angled outward relative to the surface section
82e as designated with the angle 84.
By way of illustrative example and without limitation, one hub 72 according
to the invention for a three and one-quarter inch diameter floppy magnetic
recording disk has a hub outer diameter of 0.95 inch, operates with a
chuck spindle 44 of 0.197 inch diameter, has an aperture 74 having a
diameter of 0.21 inch in the circular portion, and has two flat surfaces
76 and 78 defining an included angle of 90.degree. between them. The
bisector 80 of this angle is oriented at 75.degree. ahead, i.e. in the
direction of clockwise rotation of the disk hub illustrated in FIG. 6, of
the radial line 86. The recess 82 extends circumferentially for slightly
more than 45.degree. behind this radial line, i.e. counterclockwise from
it, has the inner side 82c at a radial distance of 0.22 inch (the first
radial distance) the camming surface 82e extends from a radial distance of
0.375 inch (the second radial distance) to 0.322 inch (the third radial
distance), and the angle 84 has a value of approximately 10.degree..
The drive chuck 18 of FIGS. 4 and 5 operates with a disk having the hub 72
of FIG. 6 as now described with additional reference to FIGS. 7A, 7B and
7C. These views show successive stages in the engagement of the drive
chuck 18 with the hub 72, as viewed from above the hub with the chuck
underneath.
The motor 14 (FIG. 1) is off and hence stopped when a record disk 16 is
loaded into the disk memory 10. The disk hub 72 seats on the chuck 18 with
the spindle 44 projecting into the hub aperture 74. FIG. 7A illustrates
the typical situation where the hub 72 is off-center relative to the drive
spindle at this initial condition. When the illustrated drive motor is
turned on, the chuck 18 rotates clockwise as viewed in FIG. 7A. When pin
48 and tab 56 of the drive chuck advance to pass the load end 82a of the
hub recess, they project without interference into the portion of the
recess 82 defined by the outer surface section 82d, as appears in FIG. 7A.
The disk hub is now free to lie flat on the chuck surface 18a. The
magnetic attraction of the chuck permanent magnet 46 draws the hub and
holds it in this seated position. The memory disk 16 typically is
stationary at this time.
Continued clockwise rotation of the drive chuck moves the drive pin 48 and
the bias tab 56 further clockwise relative to the memory disk, and the tab
56 engages the camming surface 82e of the hub recess. FIG. 7B shows a
final stage of this condition. The sliding camming engagement of the bias
tab 56 with the camming side of the hub recess rotates the cam 52 of the
chuck clockwise about the mounting post 54. The tab 56 applies to the hub
a force from the chuck spring 62. This force is directed radially outward
on the disk hub as shown in FIG. 7B with the force vector 88. It
accordingly shifts the hub 72 and correspondingly the entire disk 16
relative to the drive chuck 18. The result of this shift may, for example,
be as FIG. 7B shows, where the hub flat surface 76 is seated against the
drive spindle 44, but not necessarily the other flat surface 78.
Continued rotation of the drive chuck carries the tab 56 past the camming
surface section 82e of the hub recess and along the reverse surface 82f
until the drive pin 48 abuts the recess drive end 82b. This is the
condition which FIG. 7C illustrates. At this point, the hub 72, and
correspondingly the record disk 16, is positioned to the final desired
location relative to the drive spindle 44. That is, the vee-saddle which
the two flat surfaces 76 and 78 of the hub aperture define is seated on
the drive spindle.
More particularly, FIG. 7C shows that the drive pin 48 exerts against the
drive end of the hub recess a force, shown with the force vector 92, which
is oriented substantially normal to the radial line 86. This force, as
desired, rotates the memory disk with the drive chuck. The tab 56
continues to press radially outward on the disk hub as indicated in FIG.
7C with the force vector 90.
The resultant of the two force vectors 90 and 92, illustrated as having a
force vector 94, is oriented substantially parallel to the angle bisector
80, and is directed away from the apex of the included angle which the two
hub flat surfaces 76 and 78 form. This is the desired result for firmly
seating both flat surfaces, and therefore the disk hub, symmetrically
against the drive spindle. The disk, as a result, is precisely located
with consistent accuracy relative to the spindle of the chuck.
With further reference to FIG. 7C, the preferred reverse slope of the
surface section 82f, against which the tab 58 bears, directs the radial
force of vector 90 rotationally backward, i.e. slightly counterclockwise
from the radial orientation. As a result, the bias force from the tab 56
acts to maintain the drive pin 48 in abutting engagement with the hub end
82b. This action ensures consistent contact with minimal bounce or like
disturbance between the drive pin 48 and the hub 72. This
resiliently-applied consistent contact between the drive chuck and the
disk hub attains precise and consistent rotational indexing of a memory
disk on the disk memory and this, in turn, diminishes unusable and
otherwise lost storage space in each track of a memory disk.
It should be noted that the forces which the illustrated drive chuck 18
exert on a record disk, to position the disk and to rotationally spin it,
are directed essentially entirely in the plane of the disk, i.e. parallel
to the plane of FIGS. 7A, 7B and 7C. There is ideally no vertical force
component. This force orientation is desired to ensure that a record disk
16 seats in the disk memory with the hub flat against the chuck face. The
recording surface or surfaces of the disk 16, as a result, are at the
prescribed level or other location desired for optimum interaction with
the read/write transducer of the disk memory.
FIGS. 8 and 9 show a further feature of the invention whereby the disk
record medium is relatively free to deflect from the plane of the disk
hub, as desired for penetration of the disk by the recording head,
particularly at inner recording tracks. Further, the record medium can
deflect transversely relative to the hub without any rotational slip or
windup.
More particularly, FIG. 8 shows a preferred record disk 16 with the annulus
70 of recording medium mountingly attached to the disk hub 72 by means of
a selectively compliant web or tape 98 adhered to the recording annulus
and to the hub. FIGS. 8 and 9 do not show the layer of adhesive at the
interface of the tape 98 with the record annulus 70 and the hub 72. The
inner rim 70a of the illustrated record medium rests on the hub
approximately midway between the hub outer periphery and the inner
periphery at the spindle aperture 74. An inner portion of the record
medium adjacent this rim hence rests on the hub. The tape 98 is adhered
onto this overlying inner portion of the record annulus and to the top
surface of th hub within the rim 70a. The tape preferably is compliant in
the thickness direction to drape over the rim 70a. However, the tape
resists shear or wrinkling deformation so as to resist differential
rotation of the hub 72 relative to the record medium. Similarly, the
tape-securing adhesive provides a rigid nonshearing bond. A preferred
material for the tape 98 is a synthetic polymer film as marketed under the
trade designation "Mylar" and in one embodiment has a 5 mil thickness. A
preferred adhesive is a crosslinked permanent acrylic pressure-sensitive
adhesive such as is marketed by Flexcon Company, Inc. in Spencer, Mass.,
under the designation "V-95 Permanent Acrylic Adhesive". This adhesive
also has the permanence and temperature resistance deemed desirable.
The point of attachment which the adhesive and the tape thus effect between
the record medium and the hub of the disk 16 is at the inner rim 70a of
the record annulus. The annulus 70 is free of attachment to the hub
outward from this rim. The record annulus 70 hence is free elastically to
deflect from the hub, as FIG. 9 shows, without detracting from the
attachment. Accordingly, such a deflection of the recording medium of the
disk 16, which a read/write head conventionally causes, can occur at
record tracks aligned unusually close to the hub without undue mechanical
stress and without introducing the significant geometrical misalignment
that often occurs when the record medium is only free to deflect
commencing at the outer edge of the hub.
The invention accordingly provides a recording disk, particularly a
magnetic recording disk, of simple construction which readily receives
head penetration at innermost or central tracks with unusually low
mechanical stress and with unusually low geometrical distortion of
recording track configuations. Further, a recording disk according to
other features of the invention is readily and reliably located precisely,
with comparative high accuracy, on a drive spindle that engages only one
side of the disk. Further, the drive spindle can be significantly smaller
than the spindle-receiving aperture in the disk, as desired for ease in
loading and unloading the disk. A drive chuck according to the invention
for facilitating this precise disk location with relatively simple
mechanical mechanism is also provided. Although the invention is described
with reference to magnetic disk memories, features of the invention and
particularly of the precise locating structures thereof may have
application to other rotational driving chucks, as well as to hub
structures of other driven devices.
It will thus be seen that the objects set forth above, among those made
apparent from the preceding description, are efficiently attained. Since
certain changes may be made in carrying out the above method and in the
construction set forth without departing from the scope of the invention,
it is intended that all matter contained in the above description or shown
in the accompanying drawings be interpreted as illustrative and not in a
limiting sense.
It is also to be understood that the following claims are intended to cover
all of the generic and specific features of the invention herein
described, and all statements of the scope of the invention which, as a
matter of language, might be said to fall therebetween.
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