Dynamic magnetic information storage or retrieval – Head mounting – For moving head into/out of transducing position
Reexamination Certificate
1999-03-19
2001-04-10
Klimowicz, William (Department: 2754)
Dynamic magnetic information storage or retrieval
Head mounting
For moving head into/out of transducing position
Reexamination Certificate
active
06215628
ABSTRACT:
FIELD OF THE INVENTION
This invention relates generally to the field of rigid disc drives, and more particularly, but not by way of limitation, to a system for latching the carriage in a disc drive incorporating ramp loaded and unloaded heads, and holding the carriage in a park position with the heads unloaded from the discs during non-operating conditions in the presence of applied mechanical shocks.
Disc drives of the type known as “Winchester” disc drives or hard disc drives are well known in the industry. Such disc drives 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 boughless direct current spindle motor. In disc drives of the current generation, the spindle motor rotates the discs at speeds of up to 10,000 revolutions per minute (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 to 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 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 most common type of Winchester disc drive is the “contact start/stop” (CSS) type, in which the heads are in contact with the disc surfaces during non-operating conditions. When power is applied to such disc drives, the spindle motor is accelerated from rest to its operational speed with the start of the spindle motor acceleration occurring while the heads are still in direct contact with the disc surfaces. At some point during the spindle motor acceleration, the heads begin to fly above the discs, and do not directly contact the discs during normal operation.
When power is removed from a CSS type disc drive, the actuator is typically driven to a park position with the heads over a designated “park zone” near the inner diameter of the discs, and as the spindle motor gradually slows to a stop, the heads again come into direct contact with the discs. The actuator is commonly latched at this park position until power is once again restored to the disc drive.
One disadvantage of the CSS type disc drive is that it is subject to “head slap”, a phenomenon which occurs when an applied mechanical shock is of sufficient magnitude to overcome the load force of the head suspension used to mount and support the heads. Such uncontrolled separation of the heads and discs is accompanied by uncontrolled re-establishment of head/disc contact, potentially causing damage to the heads, the discs or both.
While CSS type disc drives have been successfully utilized in both desktop and laptop computer systems, the increasingly stringent mechanical shock requirements of both disc drives and the systems within which they are used have lead to an increased utilization of a second type of disc drive, typically referred to as “ramp load/unload” or “dynamic head load/unload” disc drives, hereinafter sometimes referred to as “ramp type” disc drives.
Ramp type disc drives include ramp structures near the outer diameter of the discs on which the heads are “parked” during non-operating conditions. When power is applied to the disc drive, the spindle motor is brought to substantially its operational speed before the latching mechanism holding the heads on the ramp structure is released. The actuator is then moved to controllably move the heads off the ramp structure into engagement with an established air bearing above the discs. Engaging the heads and discs in this manner is commonly referred to as “loading” the heads onto the discs.
Similarly, when a power loss to the disc drive is detected, the heads are moved rapidly outward on the discs, onto the ramp structure and latched in this “unloaded” position with no vertical association with the discs. Thus, in ramp type discs drives, it is the design intention that there will never be any direct contact with the heads and the discs, and that the heads will be radially displaced from the discs during non-operational conditions.
It is apparent to those of skill in the art that, with the heads parked and latched away from the discs during non-operational conditions, the disc drive will be capable of withstanding greater magnitudes of applied mechanical shock than a CSS type disc drive which is subject to such undesirable phenomenon as “head slap”.
Since the heads used in current generations of disc drives are mechanically delicate and cannot survive direct contact with ramp structures, it is common for ramp loading and unloading of the heads to be accomplished by contact between the ramp structure and specially designed contact features on the head suspension used to mount and support the head, rather than by contact between the heads themselves and the ramp structure.
Disc drives of the current generation are typically specified to be capable of experiencing applied mechanical shocks during non-operational conditions of 1000 G without incurring any fatal damage, and, as such, the latch mechanism used to hold the actuator at the park location—and the heads on the ramp structure—has become a major focus of engineering effort in the industry.
Actuator latches, or carriage latches, fall broadly into two categories: active and passive. Active latches are typically engaged using the force of the actuator as it moves the heads to the park position, and then must be actively disengaged, or unlatched, through the use of electromechanical mechanisms, such as solenoids. The cost and mechanical complexity of such active latching mechanisms—as well as the physical space required for their implementation—have acted to lessen their use in the industry.
Passive latching mechanisms can be further generally subdivided into two groups: magnetic and inertial. Magnetic latches are the simplest to implement, but have well-understood drawbacks. Magnetic latches are typically implemented by providing a fixed magnetic structure mounted to non-moveable portions of the disc drive and a complementary contact element on the moving portion of the disc drive. When the moving portion of the disc drive is brought into a position where the contact element is in close proximity to the magnet structure—typically very close to the desired park posit
Crowe & Dunlevy
Klimowicz William
Seagate Technology LLC
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