Dynamic magnetic information storage or retrieval – Head mounting – For moving head into/out of transducing position
Reexamination Certificate
1999-05-17
2001-05-01
Klimowicz, William (Department: 2754)
Dynamic magnetic information storage or retrieval
Head mounting
For moving head into/out of transducing position
C360S254700
Reexamination Certificate
active
06226154
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates generally to a disk drive having a load/unload ramp, and in particular to improvements in the load/unload ramp.
FIG. 1
shows a plan view of a typical disk drive having a single disk
8
that spins between two head suspension assemblies
24
A,
24
B (only one head suspension assembly
24
A is visible). To access different data tracks, the head suspension assemblies are moved by an actuator arm
25
in the radial direction of the disk. The actuator arm
25
is turned on a shaft
21
by a voice coil motor, as described later.
As shown in
FIG. 2
, each head suspension assembly comprises a load beam
26
A (
26
B) attached to the actuator arm
25
, a tab
28
A (
28
B) located at the tip of the load beam, a flexure
30
A (
30
B) attached to the load beam, a slider
11
A (
11
B) attached to the flexure, and a read/write head
12
A (
12
B) attached to the slider. The flexure is a delicate structure that allows the slider to pitch and roll against a dimple (not visible) in the load beam, in compliance with the disk surface, for proper air-bearing performance as the slider flies above the spinning disk.
The load/unload (LUL) ramp
40
in
FIG. 1
provides a safe place to park the head suspension assemblies when the disk is not spinning, to prevent contact between the sliders and the surface of the stationary disk.
FIG. 3
shows a sectional view of a conventional LUL ramp
40
, also showing the outer edge of the disk
8
with the sliders
11
A,
11
B and tabs
28
A,
28
B. The flexures have been omitted for simplicity.
To unload the sliders from the disk, the load beams move to the right in FIG.
3
. The load-beam tabs
28
A,
28
B land on inclined lifting slopes
44
at the front of the LUL ramp and travel up the lifting slopes, across maximum lift surfaces
46
, and down back slopes
48
to reach parking surfaces
50
, as indicated by the dotted arrows. As the tabs
28
A,
28
B ascend the lifting slopes, the sliders
11
A,
11
B are lifted away from the disk
8
. When the sliders are loaded onto the disk, the above motions are performed in reverse.
The lifting slopes
44
must be high enough to allow for variations in the landing point of the load-beam tabs, and to provide at least a minimum necessary lift in the worst case. The inclination of the lifting slopes must be sufficiently gradual that the sliders do not approach the surface of the disk too rapidly when being loaded. The back slopes
48
must be high enough to prevent unintended escape of the load-beam tabs from the parking surfaces
50
. In a disk drive with a small form factor, to minimize the dimensions of the LUL ramp, the lifting slopes
44
are generally made as low, short, and steep as possible within these constraints. Minimizing the height of the lifting slopes
44
has the added advantage of minimizing the energy needed to unload and park the sliders. A conventional LUL ramp is symmetric with respect to the median plane
7
of the disk
8
; both lifting slopes
44
have the same minimum height and maximum inclination, and in the parked position, the sliders are separated by a distance comparable to the thickness of the disk.
A problem is that the flexure design characteristics that allow the sliders to pitch and roll while flying over the disk also allow the sliders to pitch and roll in their parked position. Violent pitching and rolling motions can occur in response to shock forces, as when the disk drive is dropped. To aggravate the problem, since the flexures are only lightly loaded against the load-beam dimples, shock forces can easily separate the flexures from the dimples, allowing the sliders to come closer together. Thus while the sliders cannot contact the disk surface in their parked positions, which are outside the disk perimeter, the parked sliders can collide with each other. Such collisions can damage the air-bearing surfaces of the sliders, possibly rendering the disk drive inoperable.
To prevent such collisions, U.S. Pat. No. 6,067,209, filed Jun. 17, 1998 by A. Aoyagi, D. W. Albrecht (the present inventor) and others, provides the LUL ramp with limiter surfaces that interact with tab-like extensions of the flexures. The limiter surfaces restrict the movement of the flexures in the parked position, as will be described later. For complete collision prevention, a separator plate can also be inserted between the sliders.
However, because of the continuing reduction in disk drive dimensions, including disk diameter, disk drive thickness, and disk thickness, the separation between the parked sliders is becoming very small. For instance, in a disk drive which is currently envisaged, the thickness of the disk is on the order of 0.4 to 0.6 mm, and the distance between the parked sliders is on the same order. With such a narrow separation, the sliders may collide during shock events despite the above-mentioned limiter surfaces. If a separation plate is inserted, then instead of colliding with each other, the sliders may become contaminated by contact with the separation plate, leading to contamination of the disk surface, again with adverse effects on air-bearing performance.
In this connection, it should be noted that disk drives of a very small size are likely to be used in handheld devices, such as digital cameras. In these applications, the disk drive will often be a removable storage unit, which is apt to be roughly handled or dropped, and therefore experience severe shock forces.
SUMMARY OF THE INVENTION
An object of the invention is to reduce the possibility of shock-induced collision between the sliders.
Briefly, in a preferred embodiment of the present invention, the load/unload ramp has first and second compound surfaces disposed on opposite sides of the median plane of a disk in a disk drive. Each compound surface has a parking surface disposed outside the disk perimeter. The disk drive has load beams with read/write heads and tabs. When the read/write heads are unloaded from the disk, the tabs engage the load/unload ramp and finally come to rest on the parking surfaces. One of the two parking surfaces is farther than the other parking surface from the median plane of the disk.
By placing one parking surface farther away from the median plane of the disk, the invention increases the separation between the read/write heads in the parked position, reducing the possibility of collision between the sliders on which the read/write heads are mounted.
The invention also provides a disk drive with a load/unload ramp having the features described above.
For a fuller understanding of the nature and advantages of the present invention, reference should be made to the following detailed description taken in conjunction with the accompanying drawings.
REFERENCES:
patent: 5341260 (1994-08-01), Jabbari
patent: 6067209 (2000-05-01), Aoyagi et al.
International Business Machines - Corporation
Klimowicz William
Millett Douglas R.
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