Dynamic magnetic information storage or retrieval – Head mounting – For shifting head between tracks
Reexamination Certificate
1999-09-24
2001-09-11
Davis, David (Department: 2652)
Dynamic magnetic information storage or retrieval
Head mounting
For shifting head between tracks
C403S372000, C384S535000
Reexamination Certificate
active
06288879
ABSTRACT:
FIELD OF THE INVENTION
This invention relates generally to the field of disc drive data storage devices, and more particularly, but not by way of limitation, to the <Title>.
BACKGROUND OF THE INVENTION
Modern hard disc drives comprise one or more rigid discs that are coated with a magnetizable medium and mounted on the hub of a spindle motor for rotation at a constant high speed. Information is stored on the discs in a plurality of concentric circular tracks by an array of transducers (“heads”) mounted to a radial actuator for movement of the heads relative to the discs.
Typically, such radial actuators employ a voice coil motor to position the heads with respect to the disc surfaces. The heads are mounted via flexures at the ends of a plurality of arms which project radially outward from an actuator body. The actuator body pivots about a shaft mounted to the disc drive housing at a position closely adjacent the outer extreme of the discs. The pivot shaft is parallel with the axis of rotation of the spindle motor and the discs, so that the heads move in a plane parallel with the surfaces of the discs.
The actuator voice coil motor includes a coil mounted on the side of the actuator body opposite the head arms so as to be immersed in the magnetic field of permeable pole pieces. When controlled DC current is passed through the coil, an electromagnetic field is set up which interacts with the magnetic field of the magnetic circuit to cause the coil to move in accordance with the well-known Lorentz relationship. As the coil moves, the actuator body pivots about the pivot shaft and the heads move across the disc surfaces.
Control of the position of the heads is typically achieved with a closed loop servo system such as disclosed in U.S. Pat. No. 5,262,907 entitled HARD DISC DRIVE WITH IMPROVED SERVO SYSTEM issued Nov. 16, 1993 to Duffy et al. (Duffy '907), and assigned to the assignee of the present invention. A typical servo system utilizes servo information (written to the discs during the disc drive manufacturing process) to detect and control the position of the heads through the generation of a position error signal (PES) which is indicative of the position of the head with respect to a selected track. The PES is generated by the servo system by comparing the relative signal strengths of burst signals generated from precisely located magnetized servo fields in the servo information on the disc surface.
During track following in which a selected head is caused to follow a selected track, a servo processor compares the value of the PES to a desired value indicative of the desired position of the head to the selected track and issues a digital correction signal to the power amplifier, which in turn provides an analog current to the actuator coil to adjust the position of the head with respect to the track. During a seek operation in which a selected head is moved from an initial track to a destination track, relatively large currents are applied to the coil to initially accelerate and then decelerate the head towards the destination track. The velocity of the head is repeatedly measured and the current applied to the coil is adjusted in accordance with the difference between the actual velocity of the head and a velocity profile.
As will be recognized, a continuing trend in the industry is to provide characteristics at an ever decreasing cost. To this end, efforts are continually being undertaken to improve not only disc drive storage and transfer rates, but also manufacturing of the disc drives. Therefore, top down assembly is the ultimate goal in creating low cost disc drives. However, the method by which the actuator assembly has been manufactured in the past has traditionally been expensive and has inhibited top down assembly. Moreover, such prior art methods have provided little stiffness for the actuator during assembly to prevent actuator displacement. In particular, the actuator body is mounted to the shaft by an arrangement of precision ball bearing assemblies. The shaft, precision ball bearings, and a sleeve are commonly referred to as the cartridge bearing. The cartridge bearing is typically attached by means of a screw inserted through the base deck and into the shaft. However, such a method of assembling the cartridge bearing prevents the cost reducing top down assembly.
With continued demand for reduced cost and ever increasing levels of mechanical shock resistance, there remains a continued need for improvements in actuator assembly to prevent actuator slippage during such non-operational shock. It is to such improvements that the present invention is directed.
SUMMARY OF THE INVENTION
The present invention is directed to an the <Title>.
As exemplified by preferred embodiments, a disc drive includes a base deck which supports a spindle motor, a disc connected to the spindle motor for rotation, and a cover which cooperates with the base deck to provide a sealed enclosure. An actuator assembly has an E-block for reading and writing data to the disc. A cartridge bearing is disposed within the actuator assembly to facilitate rotational movement.
A post extends from the base deck and supports the actuator assembly and cartridge bearing. In particular, the cartridge bearing comprises a stationary shaft, a bearing supported by the shaft and a sleeve rotatably supported by the bearing for rotation about the stationary shaft. A first tolerance ring is disposed between an inner surface of the shaft and the post to secure the cartridge bearing in place during assembly. A second tolerance ring is interposed between the cartridge bearing and the E-block to secure the E-block. Together the first tolerance ring, cartridge bearing, second tolerance ring, and E-block are press fitted over the post.
The post extends the entire height of the sleeve to provide greater support for the cartridge bearing, and therefore the actuator assembly. Moreover, the stationary shaft has a top portion which extends beyond the height of the sleeve to allow ease of handling. Finally, once assembly is complete, the cartridge bearing is affixed to the base deck by a screw inserted through the top cover and through an aperture disposed at the top portion of the stationary shaft. The aperture is sized to snugly receive the post so that the screw threadingly engages a corresponding threaded aperture in the post.
In an alternative embodiment, the cartridge bearing is directly slip fitted onto the post with a slip fit pin for ease of manufacture with minimal tooling. Such slip fitting facilitates top down assembly while maintaining rigidity in the cartridge bearing and the E-block during such assembly.
The objects, advantages and features of the present invention will be apparent from the following detailed description when read in conjunction with the drawings and appended claims.
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Samsung, Technical Manual, May, 1998 (Rev. B), p. 5-2.
Eckerd Steve S.
Heaton Daniel M.
Misso Nigel F.
Crowe & Dunlevy
Davis David
Seagate Technolocy LLC
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