Dynamic magnetic information storage or retrieval – Head mounting – Disk record
Reexamination Certificate
2000-09-29
2003-04-08
Hudspeth, David (Department: 2653)
Dynamic magnetic information storage or retrieval
Head mounting
Disk record
Reexamination Certificate
active
06545844
ABSTRACT:
BACKGROUND OF THE INVENTION
This application relates generally to the field of rigid magnetic disc drive data storage devices, and more particularly, by not by way of limitation, to a clock head which facilitates writing of servo information on rigid discs in a disc drive.
Disc drives of the type known as “Winchester” disc drives or rigid disc drives are well known in the industry. Such disc drives magnetically record digital data on a plurality of circular, concentric data tracks on the surfaces of one or more rigid discs. The discs are typically mounted for rotation on the hub of a brushless DC spindle motor. In disc drives of the current generation, the spindle motor rotates the discs at speeds of up to 10,000 RPM.
Data are recorded to and retrieved from the discs by an array of vertically aligned read/write head assemblies, or heads, which are controllably moved from track to track by an actuator assembly. The read/write head assemblies typically consist of an electromagnetic transducer carried on an air bearing slider. This slider acts in a cooperative hydrodynamic relationship with a thin layer of air dragged along by the spinning discs to fly the head assembly in a closely spaced relationship to the disc surface. In order to maintain the proper flying relationship between the head assemblies and the discs, the head assemblies are attached to and supported by head suspensions or flexures.
The actuator assembly used to move the heads from track to track has assumed many forms historically, with most disc drives of the current generation incorporating an actuator of the type referred to as a rotary voice coil actuator. A typical rotary voice coil actuator consists of a pivot shaft fixedly attached to the disc drive housing base member closely adjacent the outer diameter of the discs. The pivot shaft is mounted such that its central axis is normal to the plane of rotation of the discs. An actuator housing is mounted to the pivot shaft by an arrangement of precision ball bearing assemblies, and supports a flat coil which is suspended in the magnetic field of an array of permanent magnets, which are fixedly mounted to the disc drive housing base member. On the side of the actuator housing opposite to the coil, the actuator housing also typically includes a plurality of vertically aligned, radially extending actuator head mounting arms, to which the head suspensions mentioned above are mounted. When controlled DC current is applied to the coil, a magnetic field is formed surrounding the coil which interacts with the magnetic field of the permanent magnets to rotate the actuator housing, with the attached head suspensions and head assemblies, in accordance with the well-known Lorentz relationship. As the actuator housing rotates, the heads are moved radially across the data tracks along an arcuate path.
The movement of the heads across the disc surfaces in disc drives utilizing voice coil actuator systems is typically under the control of closed loop servo systems. In a closed loop servo system, specific data patterns used to define the location of the heads relative to the disc surface are prerecorded on the discs during the disc drive manufacturing process. The servo system reads the previously recorded servo information from the servo portion of the discs, compares the actual position of the actuator over the disc surface to a desired position and generates a position error signal (PES) reflective of the difference between the actual and desired positions. The servo system then generates a position correction signal which is used to select the polarity and amplitude of current applied to the coil of the voice coil actuator to bring the actuator to the desired position. When the actuator is at the desired position, no PES is generated, and no current is applied to the coil. Any subsequent tendency of the actuator to move from the desired position is countered by the detection of a position error, and the generation of the appropriate position correction signal to the coil.
Servo information is typically recorded on the discs in late stages of the manufacturing process, i.e., after the disc stack and head assemblies have been completely assembled in the drive. Since, at the time of servo-writing, there is no information on the discs themselves with which to control movement of the actuator—as described above—servo writing is typically accomplished using sophisticated machines called servo-writers.
In order to assure that the servo information is accurately recorded on the discs—and in order to enable highly accurate positioning of the head assemblies in the finished disc drive—it is essential that the recorded servo information being recorded is closely synchronized with the rotational speed of the spindle motor.
Servo-writers typically include some type of registration and clamping system to accurately position the entire disc drive within the servo-writer, and maintain the drive being servo written in a fixed location throughout the servo writing process. Once the drive is locked in position, it is powered up and a clock head is engaged to the layer of air dragged along by one of the disc surfaces—typically the uppermost disc in the disc stack—near its outermost periphery. The rotational speed of the spindle motor is tested, and information from this testing is used to apply a highly precise series of timing marks to the disc. These timing marks are used by the servo-writer to synchronize the servo data to be written with the rotational speed of the disc.
Once the clock head has completed writing the timing marks, the servo-writer proceeds to record the position control information on the discs. This position control information may be in the form of “dedicated” servo information, all written to a single surface of the disc stack set aside for this purpose, or “embedded” servo information, which is recorded at specific intervals between those areas of the discs allocated for recording user data.
Whatever type of servo information is being recorded, the actuator of the disc drive cannot itself control movement of the head assemblies from track to track during servo writing, since the tracks do not exist until completion of servo writing. Therefore, it is common for the servo-writer to also include a highly precise servo actuator, which is mechanically coupled—usually through an opening in the disc drive housing—to the disc drive actuator, to control head movement during the servo writing process.
Once servo writing is complete, any openings used by the servo-writer are sealed, and the disc drive is in condition for initial self-testing.
Servo-writers have assumed many forms. For example, one type of servo-writer was used before the top cover of the disc drive assembly was attached. While this type of servo-writer had simple access to the disc drive actuator and discs, it also had to be utilized in a “clean room” environment, creating extra costs for manufacturing equipment, as well as stringent cleanliness demands on manufacturing personnel.
Furthermore, most disc drives currently being manufactured secure both the tops and bottoms of the spindle motor and actuator pivot shaft to the disc housing, i.e., to both the disc drive base plate, and the disc drive top cover. Without the top cover secured in place, it is problematic to maintain the desired relationship between the actuator and disc stack, and, therefore, such “open drive” servo-writers have fallen out of use.
A second type of servo-writer, described in U.S. Pat. No. 5,760,989, issued Jun. 2, 1998, to Colban, assigned to Phase Metrics of San Diego, Calif., inserted a clock head through a cooperative opening in the lateral side wall of a disc drive.
The clock head assembly of Colban was precisely clamped to the disc drive after the disc was mounted to a plate member having alignment and clamping features. The clock head assembly included a manually operated camming system for lifting and lowering the clock head assembly. In operation, the person utilizing the invention had to ensure that the camming system was maintain
Jones Gordon Merle
Miller Stephen John
Schaenzer Mark James
Castro Angel
Hudspeth David
Kelly Joseph R.
Seagate Technology LLC
Westman Champlin & Kelly P.A.
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