Dynamic magnetic information storage or retrieval – Automatic control of a recorder mechanism – Controlling the head
Reexamination Certificate
1996-02-20
2001-02-13
Nguyen, Hoa T. (Department: 2651)
Dynamic magnetic information storage or retrieval
Automatic control of a recorder mechanism
Controlling the head
C360S078020
Reexamination Certificate
active
06188537
ABSTRACT:
FIELD OF INVENTION
This invention relates generally to electromechanical devices such as disk drives and tape drives and more specifically to position sensors for transducers such as magnetic heads and optical data sensors.
BACKGROUND OF THE INVENTION
Electromechanical devices such as disk drives and tape drives often have a moveable transducer for data recording or reading. The transducer may be a magnetic recording head, a magnetic reading head, a combined magnetic recording and reading head, or in the case of optical disks, an optical sensor. Typically, at power on, absolute transducer position is uncertain. Transducer position is typically determined by driving the transducer into a mechanical stop or driving the transducer into a switch (mechanical or optical). Driving the transducer into a mechanical stop often generates audible noise. In addition, a mechanical stop may cause jamming of the transducer position actuator mechanism or other mechanical stress related problems. If a switch is used, the switch trip position must be accurately known. Typically, either the switch trip position is mechanically adjustable to an accurate position or the switch is mounted in a fixed position with absolute accuracy. In general, for switches mounted directly on printed circuit boards, the trigger position of the switch varies substantially from drive to drive due to component tolerances and manufacturing assembly tolerances. A transducer position sensing system is needed that can provide accurate position despite component and manufacturing assembly tolerances.
SUMMARY OF THE INVENTION
The present invention provides a transducer position sensing system that provides accurate transducer position without requiring absolute position accuracy of a sensor switching point. In addition, the transducer can pass through or beyond the switch point without causing mechanical stress on the transducer actuator mechanism. The switching position is fixed (non-adjustable) and does not require absolute mounting position accuracy or tight manufacturing tolerances, thereby lowering manufacturing costs. The switching position is repeatable within a drive but may vary from drive to drive. The switching position is accurately determined once during the manufacturing of the mechanism. The switching position is recorded in a permanent memory readable by a drive controller. Then, the switching position is permanently known by the drive controller. Knowing the switching position enables the drive to calibrate transducer position during an initialization procedure.
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Eisaku Shimizu, Patent Abstracts of Japan, “Magnetic Disk,” vol. 11 No. 87, Mar. 17, 1987.
Eland Michael P.
Miller Kevin L.
Hewlett--Packard Company
Nguyen Hoa T.
Winfield Augustus W.
Wong K.
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