Dynamic magnetic information storage or retrieval – Head mounting – For moving head into/out of transducing position
Reexamination Certificate
1995-04-24
2001-02-06
Letscher, George J. (Department: 2754)
Dynamic magnetic information storage or retrieval
Head mounting
For moving head into/out of transducing position
C360S255000
Reexamination Certificate
active
06185073
ABSTRACT:
BACKGROUND OF THE INVENTION
FIELD OF THE INVENTION
This invention relates to an apparatus for adjusting a position of a rotary head in a magnetic recording/reproducing apparatus such as a video cassette recorder (VCR).
As shown in
FIGS. 1A and 1B
, recent high quality consumer VCRs have several rotary heads
1
on a rotary drum
2
for recording video signals, high fidelity audio signals and for erasing recorded tracks. All heads are bonded on small metal plates
3
a
, called a head base, and the rotary drum
2
is mounted on a fixed drum
4
.
All heads should be precisely positioned on a rotary drum
2
in order to satisfy the desired recording format on the tape, because the arrangement of recorded tracks are mainly determined by the head positions on the rotary drum. The head position includes absolute head height Ha which is the distance between a datum plane
5
of the fixed drum
4
and a track edge
6
of the head
1
, relative head height Hr which is the relative head height among the track edges of different heads, and gap azimuth angle
31
of the head
1
.
The conventional manner of adjusting the head position is as follows:
Consumer VTRs are not provided with a mechanism for adjusting the azimuth angle, and the angle is adjusted in the manufacturing process of the head when cutting out the chip from the gapped bar. Therefore, the precision of azimuth angle depends on the machining precision and the precision of adhering the head
1
to the head base
3
a
with an adhesive
8
.
On the other hand, to adjust the head height, first the height H0 of each head from the surface (the head adhesion surface) of the head base
3
a
of the track edge
6
is measured, and the absolute height Ha of each head is roughly adjusted by placing a metal plate
9
called a shim having a thickness corresponding to a required adjusting amount on the basis of the measured H0 value between the head base
3
a
and the rotary drum
2
, and each head is fixed to the rotary drum with screws.
Consequently, the rotary drum
2
on which the heads are mounted is fixed on the fixed drum
4
, and the relative height of the heads is precisely adjusted using a screw
10
of which a tip is contacting with a part of the head base as shown in
FIG. 1
b
. More specifically, by tightening or loosening the screw
10
, the head base is elastically deformed, and the head chip adhered to the tip of the head base is moved vertically in the head height direction (the direction parallel to the rotary shaft A of the rotary drum) as indicated by arrow B in the drawing and Ha and Hr are adjusted precisely. However, since the fluctuations of the tip shape of the screw
10
are significant and the height is changed as much as 500 microns by turning the screw
10
by a revolution, the precise adjustment of the height in the sub-micron order is not realized.
The basis of the above conventional technique is the mechanical deformation of the head base by pushing a small screw within its elastic limits. Accordingly, when the drum unit is subjected to vibratory or temperature changing circumstances, the small screw pushing the head base may be loosened and the head height may be fluctuated.
In our experiments, in an ambient temperature cycle test of −40 degrees and +80 degrees and a vibration test, it was found that the fluctuations of the relative head height were about 2 microns.
The influence of the above fluctuations on the reproduced picture qualities is very severe, especially in the long play mode, for example, the six-hour mode in the VHS system of narrow track recording, because the above fluctuations will cause tracking errors and decrease of reproducing voltage and increase of cross talk interference from adjacent tracks.
Furthermore, if a fluid bearing is adopted as the bearing of the rotary head drum, the yawing of the rotary head drum during rotating depends on the rotation of the rotary drum. It indicates that the absolute head height, relative head height and azimuth angle also depend on the rotation of the rotary head drum. Consequently, by the conventional head adjusting method, in which the head position should be adjusted without rotating the drum, it is very difficult to guarantee a high adjustment accuracy.
SUMMARY OF THE INVENTION
It is hence a primary object of the invention to present an apparatus and an appropriate rotary head for adjusting the head position without being influenced by vibrations and ambient temperature changes.
In order to attain the above object, a rotary head adjuster of the invention comprises stage means, measuring means, laser means, and control means. The stage means is connected to the control means, and possesses a function of fixing the rotary head composed of plural head chips itself or the drum unit mounting the rotary head to a movable stage unit, and a function of adjusting a laser beam irradiation position by moving the stage so that a laser beam may be accurately applied to an appropriate position of the rotary head according to a control command from the control means.
The measuring means is connected to the control means, and it possesses a function of measuring relative positions of plural head chips, and a function of transmitting results of measurement to the control means.
The laser means is also connected to the control means, and it possesses a function of oscillating and emitting a laser beam corresponding to a required adjustment amount of a position of each head chip, according to a control command relating to a laser irradiation condition from the control means.
The control means is connected to the measuring means, the stage means, and the laser means, and it possesses a function of calculating the required adjustment amount of individual head chips by comparing desired relative positions with the results of measurement of the individual head chip positions received from the measuring means, and determining adequate laser irradiation conditions for realizing a plastic deformation of the head base depending on the obtained required adjustment amount (for example, laser power, pulse width, irradiation position, and irradiation sequence) according to a specified algorithm, and a function of controlling the other means connected depending on the obtained irradiation conditions.
According to this invention, since the rotary head is adjusted by means of plastic deformation, which is not susceptible to influence of vibrations and ambient temperature changes, high accuracy head positioning is realized. According to this invention, since no screws for adjusting the head positions are required, it has advantages in production costs.
Furthermore, according to this invention, enabling to apply a laser beam to a head base while rotating the head drum, the rotary head can be adjusted precisely even if the fluid bearing is adopted as a bearing of a rotary drum.
The invention also includes a rotary head itself adjusted by the above device.
REFERENCES:
patent: 4203140 (1980-05-01), Watanabe
patent: 4507696 (1985-03-01), Hütter
patent: 4814908 (1989-03-01), Schmitz
patent: 5065267 (1991-11-01), Yohda
patent: 5303108 (1994-04-01), Higashionji et al.
patent: 5341256 (1994-08-01), Murata
patent: 5347415 (1994-09-01), Murata et al.
patent: 0093886 (1983-11-01), None
patent: 3421219 (1985-12-01), None
patent: 0185844 (1986-07-01), None
patent: 59-203272 (1984-11-01), None
patent: 61-189463 (1986-11-01), None
patent: 62-93028 (1987-04-01), None
patent: 62-134118 (1987-06-01), None
patent: 1-227279 (1989-09-01), None
patent: 4-310613 (1992-11-01), None
Patent Abstracts of Japan, vol. 8, No. 278 (P-322)(1715) Dec. 19, 1984 & JP-A-59 144 030 (Sony K.K) Aug. 17, 1990.
Patent Abstracts of Japan, vol. 14, No. 321 (P-1074)(4264) Jul 10, 1990 & JP-A-2 105 318 (Topcon Corp.) Apr. 17, 1990.
Proceedings of Lamp '87, Osaka (May, 1987), “Laser Forming of Metals and Alloys”, Yoshiharu Namba, pp. 601-606.
Rikohgaku-sha, “Welding Engineering”, First Edition, May 11, 1989, with Summary and translation of pp. 80-84. (Partial Translation).
Higashionji Masaru
Maegawa Takaaki
Mukae Hideaki
Murata Akio
Okada Toshiharu
Letscher George J.
Matsushita Electric - Industrial Co., Ltd.
Wenderoth , Lind & Ponack, L.L.P.
LandOfFree
Rotary magnetic head having head base which is bent along... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Rotary magnetic head having head base which is bent along..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Rotary magnetic head having head base which is bent along... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2560601