Metal working – Method of mechanical manufacture – Electrical device making
Reexamination Certificate
1998-03-04
2001-05-22
Young, Lee (Department: 3729)
Metal working
Method of mechanical manufacture
Electrical device making
C029S603010, C029S603070, C029S603130
Reexamination Certificate
active
06233812
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a rotary head device and a magnetic head unit having plural magnetic heads on a rotary member and a head base, used in magnetic recording and reproducing apparatus such as VTR, and a manufacturing method thereof.
FIG. 9
is a structural diagram of a magnetic head unit used in a conventional rotary head device for VHS system. Magnetic heads
31
,
32
are fixed on a head base
33
. In a manufacturing process of magnetic heads, usually, the front surfaces of the magnetic heads
31
,
32
are finished along the sliding direction S and the thickness direction T (vertical direction to the sheet of paper) orthogonal to the sliding direction S to specified dimensions by tape polishing process, after machining. More specifically, first, the front surfaces Ss of the magnetic heads
31
,
32
are machined by leaving an allowance for finishing by tape polishing process. Then, by using a polishing tape, the front surfaces Ss are processed in curvature to the portion indicated by broken line R in
FIG. 9
, after being adhered to the head base
33
.
As shown in
FIG. 9
, when the magnetic heads
31
,
32
are processed simultaneously, the front surfaces Ss are processed along the sliding direction S over two magnetic heads
31
,
32
. In the conventional magnetic head for VHS system, the gap M of the two magnetic heads
31
,
32
is about 0.7 mm. The thickness of the magnetic recording tape for VHS system is about 20 microns. Therefore, even in the magnetic heads finished over two magnetic heads, the magnetic heads contact with the magnetic tape smoothly.
In the recent digital VTR, in order to cope with various functions, the gap M of the magnetic heads is extended to 1.2 to 4.5 mm. The thickness of the magnetic tape for the digital VTR to realize high recording density is very thin, as compared with the magnetic tape for VHS system, and is nearly 7 to 14 microns. In the rotary head device in such digital VTR, therefore, the magnetic tape may sink in between the magnetic heads and may be damaged by the edges of the magnetic heads. To prevent this damage, it is necessary to finish individually the curved surfaces Ss along the sliding direction S of the individual magnetic heads.
FIG. 10
is a plan view of a conventional magnetic head unit for a digital VTR after processing. Radii Rs
1
, Rs
2
of curved surfaces Ss along the sliding direction S of the magnetic heads
31
,
32
fixed on the head base
33
are identical. However, the positions of their centers Or
1
, Or
2
are different.
In a conventional method of manufacturing the magnetic head unit for the digital VTR, the process is complicated, that is, once the respective magnetic head is fixed on a provisional base, and the curved surface is processed by tape polishing. Then, the respective magnetic head is dismounted from the provisional base, and the plural magnetic heads
31
,
32
are fixed on the head base
33
as the final step.
In the conventional magnetic head unit, since the radii Rs
1
, Rs
2
of adjacent magnetic heads
31
,
32
are identical, optimum conditions are not obtained for improving the contact state between the head and tape due to effects of the layout of plural magnetic heads
31
,
32
on the common head base
33
, and for reducing the wear of heads.
Moreover, when disposing multiple magnetic heads on a smaller rotary drum for high density recording, the ratio of area occupied by the magnetic heads including head base on the rotary drum is high. Therefore, the design is much limited in the fixing method of rotary drum on the rotor, and connecting method of magnetic heads and rotary transformer unit. Still more, to cope with higher recording data rate, if the number of magnetic heads is increased, the space for disposing the head base is limited, and it is more difficult to realize.
SUMMARY OF THE INVENTION
It is hence an object of the invention to present a manufacturing method of rotary head device and a manufacturing method of magnetic head unit, capable of processing the front shape of plural magnetic heads precisely in batch to a specified dimension in a simple manufacturing process.
It is other object to present a rotary head device and a magnetic head unit for realizing a favorable interface between plural magnetic heads and a magnetic tape, manufactured by a method of the invention.
In the invention, curved surfaces along the sliding direction of individual magnetic heads are formed by machining or other means before fixing on a rotary member or a head base, and, after fixing the plural magnetic heads on the rotary member or head base, the curved surfaces along the thickness direction of the plural magnetic heads are finished in batch by tape polishing or other means. According to this method, the independent plural magnetic heads having curved surfaces in the sliding direction mounted on the rotary member or head base can be processed in batch to a desired front surface by finishing polishing means such as tape, without requiring complicated processes of fixing temporarily and processing the front surfaces individually.
In a preferred aspect of the invention, the central position of the curved surface along the sliding direction of a magnetic head is set so as to be present at the intersection of the gap position of the magnetic head and the position of center of rotation of the rotary member. As a result, it does not matter whether the configuration is such that the gap line of the magnetic head is directed to the center of the rotary member, or the configuration is such that the gap line of the magnetic head is parallel to the center line of the rotary member.
In other preferred aspect of the invention, the size of the curved surface formed preliminarily along a sliding direction is different from the size of the adjacent magnetic head. As a result, depending on the characteristics of the adjacent magnetic heads at the leading side and trailing side in the magnetic tape running direction, the contact of heads and tape may be improved, and the wear of heads may be reduced.
In a different preferred aspect of the invention, the magnetic heads are fixed directly on a rotary member without using a head base. As a result, the area occupied by the magnetic heads on the rotary drum is saved, and the degree of freedom is increased in design, such as the fixing method of rotary drum on the rotor unit or the connecting method of magnetic heads and rotary transformer unit. Therefore, the rotary head device of smaller size and suited to higher density recording can be produced efficiently.
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Fujiki Mitsuhisa
Hino Masayuki
Kugioka Suekazu
Okana Tetsuya
Yoda Hiroshi
Matsushita Electric - Industrial Co., Ltd.
McDermott & Will & Emery
Trinh Minh
Young Lee
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