Disk drive having an inwardly radially spring loaded hard ring disk pack attachment to the disk motor rotor

A hard disk pack assembly is attached to a motor powered rotatable member in a disk drive by a spring ring. A disk hub mounts one or more disks, functioning as an axial disk spacer when more than one disk is installed. The disk hub has a central circular opening fitted about a cylindrical body on the rotatable member and seats upon a shoulder on the cylindrical body. A spring ring snaps radially inwardly into a circumferential groove in the cylindrical body in a position wedged between surface of the circumferential groove and an upper circular edge of the circular opening in the disk hub to apply axial and radial components of spring force to the disk hub for the purpose of securely seating the disk hub on the shoulder of the cylindrical body and to center the disk hub with respect to the cylindrical body.

TECHNICAL FIELD 
This invention relates generally to hard disk drives and particularly to 
hard disk drives having removable hard disk pack assemblies. 
BACKGROUND OF THE INVENTION 
Disk pack assemblies in hard disk drives are usually fixed in place and are 
not removable. Dimensional tolerances with respect to disk flatness, 
wobble and runout in hard disk drives usually negate the use of disk pack 
assemblies in cartridges which may be installed and removed from the disk 
motor shafts or rotors. This is particularly true in small form factor 
drives, 2.5 form factor and less, where dimensional tolerances in 
conventional cartridge assemblies exceed acceptable tolerances in the 
small form factor drives. 
Thus, typically, hard disk drive disk pack assemblies, as seen in the U.S. 
Pat. No. to Matsudiara et al 4,945,432, are fixed disk pack assemblies in 
which the disks are axially stacked, with spacer rings between them, upon 
a hub, which hub may be a part of a motor rotor, and clamped between a 
shoulder at one end of the hub and a clamp at the other. There is no 
provision for removing the hub. 
The U.S. Pat. No. to Angel et al 3,587,074, illustrates a disk pack 
assembly embodying a single disk clamped between a shoulder on a disk hub 
and a clamping ring. A motor shaft is journaled in a coaxial bearing pair. 
The disk hub is secured to the end of the motor shaft by a single screw. 
If the disk drive housing could be split, removal of the screw would 
possibly permit removal of the single disk. 
The attachment of a disk pack assembly to a motor shaft or motor rotor 
involves critical dimensional tolerances. The slip fit of a disk hub about 
a motor shaft or within or about some part of a motor rotor, as in Angel 
et al, does not meet dimensional tolerances in small form factor drives, 
absent some centering arrangement associated with securing the disk pack 
assembly to some rotating part of the motor, as the motor shaft or the 
motor rotor. 
SUMMARY OF THE INVENTION 
The hard disk assembly according to this invention includes a hub which 
mounts at least one disk. The hub has a central circular opening which 
fits over the cylindrical body of a member, such as a motor rotor or 
shaft, or, other rotatable member, powered by a motor in a disk drive. The 
hub seats upon a peripheral shoulder or flange on the cylindrical body. A 
circumferential groove in the cylindrical body has an upper conical groove 
surface spaced above the upper surface of the hub. A spring ring of a hard 
material, such as a metal ring, has an expandable inner diameter which 
when expanded fits over the outer diameter of the cylindrical body and 
snaps into the circumferential groove, wedging between the upper conical 
groove surface and the hub, to apply a component of force seating the hub 
securely upon the flange and, to additionally apply a radial component of 
force centering the hub with respect to the cylindrical body. 
The spring rings having expandable inner diameters may take several forms. 
One form being a ring of spring sheet material of inverted V-shaped cross 
section, having inner and outer conical faces, the inner conical face 
being defined by a plurality of radial fingers, the distal ends of which 
are radially deflectable and displaceable to clear the diameter of the 
cylindrical body and snap into the circumferential groove to engage the 
upper conical surface of the circumferential groove, in which position the 
outer peripheral edge of the ring seats in a circumferential groove in the 
upper face of the hub, forcing the hub against the peripheral shoulder of 
the cylindrical body and radially centering the hub. 
Another form of spring ring being of a material of solid cross section, 
disclosed cross sections being circular and wedge shaped. Such solid rings 
are split rings permitting expansion or enlargement of their inner 
diameter to clear the diameter of the cylindrical body and to snap into 
position in the circumferential groove, in a position wedged between the 
upper conical surface of the circumferential groove and the upper circular 
edge of the circular opening in the disk hub. The solid split ring applies 
both axial and radial forces to the hub to seat the hub on the peripheral 
shoulder and to center the hub with respect to the cylindrical body.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
FIGS. 1-3 provide plan and section views of one embodiment of this 
invention. These figures, while depicting the structure of a small form 
factor (1.3 form factor, for example), hard disk drive 1, should not be 
construed as limiting this invention in its application to a disk drive or 
to any particular size of disk drive. Typically these figures are drawn to 
an enlarged scale, FIG. 2, taken in the section plane II--II of FIG. 1, 
being an enlargement of FIG. 1, and FIG. 3 being a further enlargement of 
a fragmentary portion of FIG. 2, to permit the illustration of essential 
detail. In FIGS. 1 and 2, the disk drive 1 comprises a main frame or base 
structure 5 of metal, such as aluminum, which is the backbone, i.e., the 
primary structural member of the disk drive structure. The base structure 
5 is preferably of a single piece of milled or cast metal which is 
precision machined, having a base plate 5a with integral end walls 5b and 
side walls 5c, FIG. 1. 
Since the electrical function of this disk drive is not necessary to an 
understanding of this invention, the printed circuit assembly, comprising 
the disk controller for the disk drive, is not shown. 
A cover 5e, FIG. 2, is secured as by adhesive bonding, to the upper edges 
of the end walls 5b and the side walls 5c of the base structure or 
mainframe 5 to seal and further stiffen the assembly. 
The hard disk drive 1 comprises a hard disk assembly 8 and a rotary 
actuator assembly 9. 
The rotary actuator assembly 9 is journaled on the spindle 9a secured in 
the base 5a and comprises two arm structures 9d, one above and one below 
the hard disk assembly 8. Each arm structure mounts a transducer, such as 
a magnetic head 9d4 at its distal end, in a position confronting a surface 
of the disk 8a. Only the upper arm structure 9d is seen in the drawings, 
appearing only in FIG. 1. An actuator motor arm 9e mounts a coil 9f1 of an 
axial gap actuator motor 9f. The electromagnetic field of the coil 9f1 
links the magnetic field of a permanent magnet structure 9f3 mounted to 
the base structure 5. As is known, the coil 9f1 is reversibly energized to 
move the rotary actuator 9 bi-directionally about the spindle 9a to move 
the transducer to different radial locations with respect to the surface 
of a disk 8a of the disk assembly 8. 
The hard disk assembly 8 comprises a disk spacer or hub 12 having a central 
circular opening 12a, FIGS. 2 and 3, top and bottom axial faces 12b and 
12c to which disks 8a and 8b, respectively, are adhesively bonded, and 
upper and lower circular edges 12d and 12e respectively of the circular 
opening 12a. 
In FIGS. 1 and 2, the disk motor 13 is a radial gap motor having a salient 
pole stator 13b, FIG. 1, the magnetic poles 13b1 of which are mounted 
directly to the base structure 5 beneath the motor rotor 13a. The outer 
ends of the salient poles 13b1 of the stator, one being shown in FIG. 1, 
define a radial gap with a permanent magnet ring 13c disposed within the 
rim of the rotor, the permanent magnetic ring 13c being radially spot 
magnetized in alternating polarity in equally spaced circumferential 
positions thereabout, defining a number of permanent magnet poles greater 
(or less)in number than the number of salient poles. The disk motor rotor 
13a is of a magnetic flux conducting material such as steel and forms the 
flux return path for the radially poled permanent magnet poles in the 
permanent magnet ring 13c. 
High data volume demands in the smallest possible volume of mechanical 
packaging, regardless of the form factor size, result in limited space 
within the disk drive housing for various mechanical structures. Thus, any 
simplification of the mechanical design which eliminates parts or which 
simplifies the fabrication of the disk drive, becomes a requirement for 
fabrication of the drive. In a structure of the type of FIG. 2, for 
example, a simplification which is presently used in the fabrication of 
the disk drive employs an adhesive bond between the hard disks 8a and 8b 
and the hub 12 at the hub surfaces 12b and 12c. Employing this adhesive 
bonding as the sole means of attaching the hard disk 8a and 8b to the disk 
hub 12, eliminates any need for mechanical devices of the type employed by 
Matsudaira et al to clamp the hard disks to the dish hub. Other 
attachments, such as that attachment disclosed in the applicant's related 
copending application, referenced hereinabove, are applicable here. 
As seen in the cross sectional views of FIGS. 2 and 3, the circular opening 
12a of the disk hub 12 is fitted over a concentric cylindrical body 13a1 
of the motor rotor 13a and seats upon a shoulder 13a2. Neither of the 
disks 8a, 8b, contact the motor rotor. A circumferential groove 13a4 is 
formed in the cylindrical body 13a1. The circumferential groove 13a4 has 
an upper circumferential groove edge 13a5, a lower circumferential groove 
edge 13a6, a circumferential groove bottom 13a7, and an upper conical 
groove surface 13a8 sloping downwardly and inwardly of the cylindrical 
body 13a1 from the upper circumferential groove edge 13a5 to the 
circumferential groove bottom 13a7. The lower circumferential edge 13a6, 
FIG. 3, of the circumferential groove 13a4 is positioned below the upper 
surface 12b of the hub 12. The upper conical surface 13a8 of the 
circumferential groove 13a4 slopes downwardly and inwardly in the 
cylindrical body 13a1, as best seen in the enlarged cross sectional view 
of FIG. 3, in a position above the hard disk assembly 8. A toroidal split 
spring ring 14 of metal having a body of circular cross section, is seated 
in the circumferential groove 13a4. The split ring 14 is of lesser plan 
form diameter than the diameter of the cylindrical body 13a1. The circular 
cross section of the body of the spring ring 14 has a diameter of greater 
dimension than the dimension between the upper conical groove surface 13a 
of the circumferential groove 13a4 and the upper circular edge 12d of the 
circular opening 12a in the disk hub 12. The spring ring is spread open, 
using a tubular mandrel or spring ring pliers and is slipped over the 
upper end of the cylindrical body 13a1 and snapped into the 
circumferential groove 13a4. When installed, the spring bias of the spring 
ring 14, as best seen in FIG. 3 has an inwardly directed radial force 
component which draws the circular spring body 14a into the 
circumferential groove 13 where it is jammed or wedged between the upper 
conical groove surface 13a8 of the circumferential groove 13a4 and the 
upper circular edge 13d of the circular opening 12a in the disk hub 12. In 
this position, the spring ring 14 applies radial and axial force 
components to the disk hub 12, centering the disk hub with respect to the 
cylindrical body 13a1 and securely seating the disk hub 12 against the 
shoulder or flange 12e on the cylindrical body 13a1, in secure static 
frictional engagement therewith. The disk hub 12 is further secured to the 
cylindrical body 12a2 by the static friction coupling between the disk hub 
12 and the cylindrical body 13a1 provided by the split ring 12a7. The 
essential features of the circumferential groove reside in the upper 
conical groove surface 13a8, the disposition of the lower circumferential 
groove edge 13a6 sufficiently below the upper circular edge 13d of the 
circular opening in the disk hub 12, and the depth of the circumferential 
groove to the groove bottom 13a7, both for the purpose of clearing the 
circular body cross section 14a of the split ring 14. Thus, it will be 
appreciated that other cross sectional configurations may be employed, the 
cross section of the circumferential groove 12a4 disclosed representing 
the presently preferred design. 
The split ring 14 has a circular body 14a of a cross sectional diameter 
which is greater than the minimum dimension between the conical groove 
face 13a8 and the edge 12d of the central circular opening 12a of the disk 
hub 12. The cross section diameter of the circular body 14a of the split 
ring 14 is chosen to achieve optimum split ring penetration into the 
circumferential groove 13 without contacting the groove surfaces other 
than the upper conical groove surface 13a8. 
FIGS. 4 and 5 show a second embodiment of this invention. Parts in these 
figures corresponding to those of FIGS. 1, 2 and 3 bear like reference 
characters. FIGS. 4 and 5 illustrate a split spring ring body 14a of wedge 
shaped cross-section. The key features of this wedge shaped split ring 14 
reside in the upper conical surface 14a1 and the lower conical surface 
14a2. Attention is directed to the difference in slope of these respective 
conical surfaces the angles of these conical surfaces with respect to a 
horizontal plane being different, that for the upper conical surface 14a1 
being greater than that for the lower conical surface. Comparing these 
respective angles with FIG. 3, for example, it will be seen that the angle 
of the conical surface 14a1 corresponds essentially to the tangent of the 
angle at the point of contact of the circular body 14a of the split ring 
of FIG. 3 with the upper conical surface 13a8 of the cylindrical member 
13a. Similarly, the angle of the lower conical surface 14a2 of the wedge 
shaped split ring 14 of FIG. 5 corresponds closely to the tangent of the 
angle defined between the point of contact of the circular body 14a of the 
split ring of FIG. 3 with the upper circular edge 12d of the circular 
opening 12a in FIG. 3. The inner and outer circumferential surfaces of the 
wedge shaped split ring 14 are trimmed as shown to avoid interference, 
respectively, with the groove bottom 13a7 and the disk 8a. Similarly, the 
bottom face of the wedge shaped split ring 14 is trimmed so that it clears 
the bottom edge 13a6 of the circumferential groove 13a4. As in the case of 
the toroidal split ring 14 of FIGS. 4 and 5, the wedge shaped split ring 
14 of FIG. 5 applies radial and axial components of split ring force to 
the disk hub 12 to securely seat the disk hub on the shoulder 13a2 on the 
cylindrical body 13a1 and to center the disk hub 12 with respect to the 
cylindrical body 13a1. 
A third embodiment of the invention is seen in FIG. 6 and 7. Here again, 
parts in these figures corresponding to those of FIGS. 1, 2 and 3 bear 
like reference characters. In FIGS. 6 and 7 the ring 14 is fabricated of 
flexible sheet metal and, as seen in FIG. 6, is of inverted V shaped cross 
section, defining an inner conical surface 14b and an outer conical 
surface 14c. As seen in FIG. 7, the inner conical surface is defined by a 
plurality of radially disposed fingers 14b1. These fingers are of a length 
to extend into the upper vertex of the spring ring 14 outside of the 
cylindrical surface 13a1 of the cylindrical body 13a. The outer perpherial 
edge of this ring fits into a circumferential slot 12f in the upper 
surface 12b of the disk hub 12, in a position adjacent to and clear of the 
disk 8a. This spring ring 14 is installed by inserting a mandrel of 
slightly larger diameter than the diameter of the cylindrical body 13a 
into the spring ring 14. This deflects the fingers 14b radially outwardly. 
When the mandrel is positional concentrically of the upper end of the 
cylindrical body 13a, the spring ring may then be forced downwardly along 
the mandrel and onto the outer circumferential surface 13a1 of the 
cylindrical body to a position in which the spring ring 14 snaps into the 
circumferential groove 13a4. The outer peripheral edge of the spring 14 is 
then forced into the circumferential groove 12f in the disk hub 12. In 
this position the outer perpherial edge of the spring ring 14 couples an 
axial component of force and a radial component of force to the disk hub 
12 to securely seat the disk hub 12 on the shoulder 13a2 at the base of 
the cylindrical body 13a and to center the disk hub 12 with respect to the 
cylindrical body 13a.