International Business Machines Corporation

Karl A Shidler

Gerald Roy Knutson

Timothy Roy Block

Francis S Luecke

Ronald L Soderstrom

Steven Dennis Keidl

Daniel O Castrodale

Jeffrey L Lovgren

Norman Edward Slindee

Larry Frederick Mattson

Ralph A Russell

Mark R Enstrom

Coy Lee Huffine

The invention uses a small sized, low cost, high accuracy, semiconductor laser interferometer to position the transducer in a disc storage system. Light is reflected back over the path to be measured and directly back into the semiconductor laser. This causes the power present in the laser to be varied. Unexpectedly, the output of the photosensor associated with the laser has an asymmetric, sawtooth waveform.

Precision measurement and positioning system for disk storage system

Control information for a flexible magnetic disk storage assembly is recorded on the periphery of the disk in a region not used for recording data. The control information is read through the protective cover or envelope which encloses the disk by means of a magnetic transducer such as a four track audio cassette head which bears against the envelope. By recording index and sector pulses as part of the control information, hard sectoring can be inexpensively and accurately achieved. A recorded fixed frequency control signal can be read and used as part of the feedback loop in a phase locked oscillator used to control a d.c. motor driving the spindle. The control information can also include servo tracks which assist in registering the data transducer directly over data tracks on media which has changed its dimensions.

Magnetic disk-control track read through envelope

A transducer particularly for use with magnetic record disks and composed of cores having transducing gaps therein adapted to contact or be in near contact with a record disk at the gaps and composed also of outriggers on the sides of the cores for increasing the surface area of the transducer adapted to contact or be in near contact with a record disk. The cores are of ferrite and have windings thereon, and the outriggers are of ceramic, both the ferrite and ceramic being nonconductive electrically. One of the outriggers is provided with a plating of electrically conductive material on a side surface with the plating being coterminous with the surface of the outrigger adapted to contact the record disk or be in near contact with it, and a ground lead is connected with the plating so as to ground any electrostatic charge on the surface of the disk.

Method of making grounded transducer for magnetic record disks

A magnetic head or transducer assembly for cooperating with a relatively moving magnetic medium and for reading and/or writing a track of magnetic information on the medium and for erasing the edges of the track and old information adjacent to the edges of a newly written track. The head comprises a central magnetic core with a gap on an active face of the head assembly and with a read/write coil on the magnetic core and comprises a pair of additional, erase magnetic cores on opposite sides of the central magnetic core and forming a pair of erase gaps on the active face of the head assembly. A single erase coil is disposed on opposite legs of the erase cores, and an L-shaped side bar completes the erase magnetic circuit for both of the erase cores and lies on one end of the erase coil and provides an air gap between it and the ends of each of these erase core legs so as to cause the action of the two erase gaps to be equal in their erasing action.

Read/write and tunnel erase magnetic head assembly

A transducer particularly for use with magnetic record disks and composed of cores having transducing gaps therein adapted to contact or be in near contact with a record disk at the gaps an composed also of outriggers on the sides of the cores for increasing the surface area of the transducer adapted to contact or be in near contact with a record disk. The cores are of ferrite and have windings thereon, and the outriggers are of ceramic, both the ferrite and ceramic being nonconductive electrically. One of the outriggers is provided with a plating of electrically conductive material on a side surface with the plating being coterminous with the surface of the outrigger adapted to contact the record disk or be in near contact with it, and a ground lead is connected with the plating so as to ground any electrostatic charge on the surface of the disk.

Grounded transducer for magnetic record disks

A rotary magnetic record disk assembly comprising a magnetic disk which is rotatably disposed within a containing jacket of material of high electrically insulating characteristics. An electrically conductive layer is disposed on the inside surface of the jacket for draining away electrostatic charge on the jacket.

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Rochester, MN, United States of America

Karl A Shidler