Dynamic magnetic information storage or retrieval – Head mounting – For shifting head between tracks
Reexamination Certificate
1999-07-29
2001-05-08
Evans, Jefferson (Department: 2754)
Dynamic magnetic information storage or retrieval
Head mounting
For shifting head between tracks
C360S291000
Reexamination Certificate
active
06229674
ABSTRACT:
TECHNICAL FIELD
This invention relates to the field of tape media read-write head positioning devices.
BACKGROUND ART
Read-write head positioning devices used in magnetic tape drives to align the read-write head with data in the magnetic tape often incorporate a two-actuator design. One actuator provides coarse positioning to move the read-write head between data bands. The other actuator provides fine positioning to maintain alignment between the read-write head and the data tracks. The two actuators are usually mounted in a “piggyback” arrangement with the fine position actuator riding on the coarse position actuator.
The coarse positioning actuator is typically a linear stage driven by a stepper motor. Stepper motors have the ability to move the linear stage anywhere across the width of the magnetic tape at modest speeds. However, most stepper motors lack the accuracy and bandwidth necessary to maintain alignment between the read-write head and the data tracks as the magnetic tape moves across the face of the read-write head.
The fine positioning actuator is typically a voice coil mounted on the linear stage and held at a rest position by some type of spring. A voice coil actuator provides micron to submicron precision positioning at a bandwidth of hundreds to thousands of hertz. However, a single voice coil and spring combination that can meet the fine positioning requirements across the full width of the tape is expensive and unnecessary.
The combination of coarse positioning and fine positioning is desired to meet the requirements associated with reading and writing on the magnetic tapes. Current solutions involve two actuators, their respective controllers, and a significant amount of hardware. What is desired is a simpler positioning device that requires only one actuator and minimal hardware.
DISCLOSURE OF INVENTION
The present invention is a coarse and fine transducer positioning device employing a single actuator. A carriage transports the transducer relative to a moving frame. The moving frame transports the carriage relative to a fixed frame. A detent mechanism disposed between the fixed frame and moving frame provides coarse positioning of the moving frame at several discrete positions relative to the fixed frame. One or more resilient members bias the carriage toward a rest position relative to the moving frame. The single actuator is disposed between the carriage and fixed frame to provide fine positioning of the carriage, and thus the transducer. Coarse position movement is achieved by first driving carriage in the desired direction to engage mechanical stops on the carriage with stop abutments on the moving frame. Next, the actuator drives the carriage further causing the detent mechanism to release the moving frame. Coarse position movement is halted when the detent mechanism captures at the desired discrete position.
Variations of the present invention are created by disposing the actuator, resilient member, detent mechanism, and stop abutments at different positions. In one embodiment, the actuator is disposed between the carriage and moving frame and the stop abutments are part of the fixed frame. In another embodiment, the actuator and resilient member are disposed between the fixed frame and the moving frame, the detent mechanism is disposed between the moving frame and the carriage, and the stop abutments are part of the fixed frame.
A voice coil is used as the single actuator in the preferred embodiment of the present invention. Coarse and fine positioning may be achieved by varying the current through the voice coil's winding. The resilient members are thin metal flexures in the preferred embodiment. The flexures allow for submicron movement and are insensitive to debris that may collect on the positioning device.
Accordingly, it is an object of the present invention to provide an apparatus and a method for providing coarse positioning and fine positioning for a transducer using a single actuator.
These and other objects, features and advantages will be readily apparent upon consideration of the following detailed description in conjunction with the accompanying drawings.
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Brooks & Kushman P.C.
Evans Jefferson
Storage Technology Corporation
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