Latch for disc drives

Details Latch for disc drives Latch for disc drives

1999-02-26

2003-03-18

Miller, Brian E. (Department: 2652)

Dynamic magnetic information storage or retrieval

Head mounting

For moving head into/out of transducing position

Reexamination Certificate

active

06535357

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates generally to the field of disc drive data storage devices, and more particularly but not by way of limitation, to a latch for an actuator of a disc drive to retain the read/write heads in a parked location when the disc drive is non-operational.
BACKGROUND OF THE INVENTION
Modern disc drives are commonly used in a multitude of computer environments, ranging from super computers to notebook computers, to store large amounts of data in a form that is readily available to a user. Typically, a disc drive has one or more magnetic discs that are rotated by a spindle motor at a constant high speed. Each disc has a data storage surface divided into a series of generally concentric data tracks that are radially spaced across a band having an inner diameter and an outer diameter. The data is stored within the data tracks on the disc surfaces in the form of magnetic flux transitions. The flux transitions are induced by an array of read/write heads. Typically, each data track is divided into a number of data sectors where data is stored in fixed size data blocks.
The read/write head includes an interactive element such as a magnetic transducer. The interactive element senses the magnetic transitions on a selected data track to read the data stored on the track. Alternatively, the interactive element transmits an electrical signal that induces magnetic transitions on the selected data track to write data to the track.
Each of the read/write heads is mounted to a rotary actuator arm and is selectively positioned by the actuator arm over a pre-selected data track of the disc to either read data from or write data to the data track. The read/write head includes a slider assembly having an air bearing surface that, in response to air currents caused by rotation of the disc, causes the head to fly adjacent to the disc surface with a desired gap separating the read/write head and the corresponding disc.
Typically, multiple center-open discs and spacer rings are alternately stacked on a spindle motor hub. The hub, defining the core of the stack, serves to align the discs and spacer rings around a common axis. Collectively the discs, spacer rings and spindle motor hub define a disc pack assembly. The surfaces of the stacked discs are accessed by the read/write heads which are mounted on a complementary stack of actuator arms which form a part of an actuator assembly. The actuator assembly generally includes head wires which conduct electrical signals from the read/write heads to a flex circuit which, in turn, conducts the electrical signals to a flex circuit connector mounted to a disc drive base deck.
When the disc drive is non-operational, each read/write head is brought to rest upon the adjacent disc in a parking zone where data is not stored. Typically, each read/write head is positioned adjacent the parking zone before the rotational velocity of the spinning discs decreases below a threshold velocity. Below this threshold velocity the spinning discs fail to sustain an air bearing in support of the read/write heads.
Once the heads are positioned in the parking zone, it is necessary to secure the actuator assembly by a latching arrangement to prevent the read/write heads from subsequently moving out onto the data storage zone of the discs while the disc drive is non-operational. Latching arrangements are generally practiced in the art and have included various configurations of springs, solenoids and magnets to secure and release the actuator. For example, see U.S. Pat. No. 5,187,627 entitled MAGNETIC LATCH AND CRASH STOP, issued Feb. 16, 1993, to Hickox and Stram; U.S. Pat. No. 5,224,000 entitled CRASH STOP AND MAGNETIC LATCH FOR A VOICE COIL ACTUATOR, issued Jun. 29, 1993, to Casey and West; and U.S. Pat. No. 5,231,556 entitled SELF-HOLDING LATCH ASSEMBLY, issued Jul. 27, 1993, to Blanks. All of these references are assigned to the assignee of the present invention.
Associated problems with such devices have limited the application in which they can be used. For example, a continuing trend in the industry is the reduction in size of modern disc drives. As a result, the discs of modern disc drives increasingly have smaller diameters and tighter disc-to-disc spacings. Although providing increasing amounts of storage capacity, narrow vertical spacing of the discs gives rise to a problem of increased sensitivity to external mechanical shock. Additionally, as disc drives continue to decrease in size, smaller heads, thinner substrates, longer and thinner actuator arms and thinner gimbal assemblies continue to be incorporated into the disc drives. These factors significantly increase the need to protect the disc drives from incidental contact between the actuator arm/gimbal assemblies and the disc surfaces. Furthermore, market requirements demand ever increasing non-operating shock performance.
Consequently, there has not been available a latching device which will universally meet the ever increasing demands of disc latching in protecting the discs from the deleterious effects of non-operational shock, such as can occur during shipping and handling. Protection from these and other mechanical shocks continue to be a major problem to the industry.
Accordingly, there is a need for an improved latch apparatus for a disc drive to reduce the susceptibility of damage to the disc drive.
SUMMARY OF THE INVENTION
The present invention provides a latch for a disc drive assembly, wherein the disc drive assembly has a disc pack with a data storage disc having a parking zone and a data storage zone. The disc pack includes a spindle motor for rotating the disc. An actuator of the disc drive assembly is pivotally supported for pivoting in a plane parallel to that of the disc, the actuator supporting an array of read/write heads in radial movement across the disc in data reading and writing relationship therewith.
The disc drive has a voice coil motor that interacts with the actuator to move the read/write heads to selected positions in the data storage zone and to the parking zone. The parking zone provides a landing surface for the read/write heads when the disc drive is non-operational, thus preventing damage to stored data on the disc. The voice coil motor includes a magnet assembly having a pair of opposing magnet members supported by a pair of opposing poles. The latch of the present invention is generally interposed between the poles.
A latch pawl is pivotally supported by a supporting member in movement between a latched position and an unlatched position. In a preferred embodiment the latch pawl pivots about an axis that is parallel to an axis of rotation of the actuator. The latch pawl supports a first latch arm having a magnetically permeable member that interacts with a magnetic flux of the magnet assembly to retain the latch pawl in the latched position. The latch pawl furthermore supports an opposing second latch arm that retains the latch pawl in the unlatched position in a similar manner.
The latch pawl has a slot that receivingly engages a portion of the actuator to provide a coupling engagement therebetween. So coupled, pivotal movement of the actuator moves the latch pawl to the latched position when the disc drive is non-operational, and to the unlatched position when the disc drive is operational.
In the non-operational mode of the disc drive, the first latch arm retains the latch pawl position and the coupling engagement prevents movement of the actuator so that the read/write heads remain in the parking zone. On disc drive start-up, the discs are rotated to lift the read-write heads from the disc surface and the actuator pivots, overcoming the retaining force of the first latch arm, to move the latch pawl to the unlatched position. In the operational mode of the disc drive, the second latch arm retains the latch pawl position and the coupling disengagement permits free movement of the actuator as the read/write heads are moved to selected data tracks in the data storage zone.
The latch furthermore has an inner stop and an outer stop to lim

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