Dynamic magnetic information storage or retrieval – Head mounting – For adjusting head position
Reexamination Certificate
2000-04-06
2003-02-18
Renner, Craig A. (Department: 2652)
Dynamic magnetic information storage or retrieval
Head mounting
For adjusting head position
Reexamination Certificate
active
06522506
ABSTRACT:
RELATED APPLICATION DATA
The present application claims priority to Japanese Application No. 11-103236 filed Apr. 9, 1999 which application is incorporated herein by reference to the extent permitted by law.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a magnetic head unit having a rotary drum in which a magnetic head element is disposed and to a method for writing or reading signals to/from a magnetic tape by using the magnetic head unit.
2. Description of the Related Art
Hitherto, there has been proposed a helical scan type signal recording/reproducing method for recording/reproducing signals to/from a magnetic tape by obliquely sliding a magnetic head element mounted in a rotary drum on the running magnetic tape.
Because this helical scan method is a method for writing or reading signals by sliding the magnetic head element on the running magnetic tape at high speed, it has merits that the relative sliding speed of the magnetic tape and the magnetic head element is fast and that a high data transfer rate may be obtained.
The magnetic head unit for writing or reading signals to/from the magnetic tape by means of this helical scan method comprises a unit body whose outer shape is approximately cylindrical and the magnetic head element attached to the rotary drum side of the unit body. The magnetic head element is attached to a head base such that its edge portion is fixed to the rotary drum so that it projects somewhat out of the peripheral plane of the unit body. Meanwhile, the magnetic tape is wound around the peripheral plane of the unit body while slanting by a predetermined slant angle with respect to the direction which crosses at right angles with an axis of rotation of the rotary drum, e.g., by a winding angle of 180 degrees.
The magnetic head element attached to the rotary drum slides aslant on the magnetic tape, thus writing or reading signals to/from the magnetic tape, when the rotary drum is rotated while winding the magnetic tape around the peripheral plane of the unit body.
By the way, the condition of contact between the magnetic head element of the magnetic head unit and the magnetic tape depends on a projection of the edge portion of the magnetic head element out of the peripheral plane of the unit body. Then, when the edge portion of the magnetic head element projects too much out of the peripheral plane of the unit body, the pressure of contact of the magnetic head element to the magnetic tape becomes excessive, thus becoming a factor of increasing the wear of the magnetic head element or of damaging the magnetic tape. When the edge portion of the magnetic head element projects too little out of the peripheral plane of the unit body on the contrary, the magnetic head element does not touch the magnetic tape well, thus causing a large spacing loss produced by a gap between the magnetic head element and the magnetic tape to decrease the output.
SUMMARY OF THE INVENTION
By the way, the adoption of a magneto-resistance effect type magnetic head element as a reproducing magnetic head element has been discussed in order to deal with the recent requirement for recording at high density by the helical scan method magnetic head unit.
Although the magneto-resistance effect type magnetic head element has a merit that it allows a high reproducing output to be obtained as compared to an inductive type magnetic head element which has been used in general as a reproducing magnetic head element in the helical scan method magnetic head unit, it has had a problem that it is very liable to wear when it is slid on a magnetic tape at high speed.
Then, in the magnetic head unit described above, the magneto-resistance effect type magnetic head element must be attached to the rotary drum more carefully and the projection of the edge portion of the magnetic head element from the peripheral plane of the unit body must be adjusted at higher precision to minimize the wear of the magnetic head element when it is adopted as the reproducing magnetic head element.
However, it is very difficult and cumbersome to adjust the projection of the edge portion of the magnetic head element out of the peripheral plane of the unit body in the stage of attaching the magnetic head element to the rotary drum, as described above.
Further, even if the magnetic head element is attached to the rotary drum such that the projection of the edge portion of the magnetic head element out of the peripheral plane of the unit body is optimized, it is unable to avoid the advancement of the wear of the magnetic head element which occurs along its use. Then, when the magnetic head element is attached fixedly to the rotary drum like the magnetic head unit described above, the projection of the edge portion of the magnetic head element out of the peripheral plane of the unit body changes and the touch of the magnetic head element to the magnetic tape may not be kept well when the wear of the magnetic head element advances.
Because the magnetic tape is wound aslant around the peripheral plane of the unit body in the magnetic head unit described above, the ratio of a part of the magnetic tape wound around the rotary drum to a part of the magnetic tape wound around the stationary drum differs depending on the position. For instance, the magnetic tape is wound more to the rotary drum at the tape advancing side of the unit body, i.e., at the side where the magnetic tape is started to be wound, and the magnetic tape is wound more to the stationary drum at the side of the unit body where the tape is released.
Then, in the magnetic head unit, air film is created between the rotary drum and the magnetic tape as the rotary drum is rotated, and the distance between the magnetic tape and the peripheral plane of the unit body differs corresponding to the rate of the part of the magnetic tape wound to the rotary drum. That is, the distance of the magnetic tape at the part wound more to the rotary drum from the peripheral plane of the unit body is large than the magnetic tape of the part wound more to the stationary drum. Accordingly, when the magnetic head element is fixed to the rotary drum like the magnetic head unit described above, the pressure of contact of the magnetic head element to the magnetic tape changes depending on the position of the magnetic tape where the magnetic head element slides, i.e., whether the magnetic head element is located at the side where the magnetic tape advances or at the side where the magnetic tape is leased, thus causing nonuniformity of the touch in some cases.
The present invention has been made in view of the problems as described above and provides a magnetic head unit which is arranged so as to effectively suppress the wear of the magnetic head element and the damage of the magnetic tape and to be able to obtain a high output by keeping the touch of a magnetic head element to a magnetic tape well, and a method for writing or reading signals by using the magnetic head unit.
According to one aspect of the invention, the magnetic head unit comprises an approximately cylindrical unit body having a stationary drum and a rotary drum turnably provided with respect to the stationary drum; a magnetic head element in which an edge portion thereof is disposed in the rotary drum side so as to face to the outside from the peripheral plane of the unit body; and head projection regulating means for varying a projection of the edge portion of the magnetic head element out of the peripheral plane of the unit body.
In this magnetic head unit, the unit body has the rotary drum and the stationary drum and is formed approximately into the cylindrical shape as a whole. The rotary drum is turnable with respect to the stationary drum.
The magnetic head element is disposed on the rotary drum side of the unit body. The magnetic head element is provided such that the edge portion thereof faces to the outside from the peripheral plane of the unit body. When the rotary drum is rotated, the magnetic head element slides on a magnetic tape wound around the peripheral plane of the u
Renner Craig A.
Sonnenschein Nath & Rosenthal
Sony Corporation
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