Dynamic magnetic information storage or retrieval – Record transport with head stationary during transducing – Drum record
Patent
1984-05-30
1987-11-10
Hecker, Stuart N.
Dynamic magnetic information storage or retrieval
Record transport with head stationary during transducing
Drum record
360 84, 360108, 36013024, G11B 553, G11B 2104
Patent
active
047061448
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a rotary head device using a dynamic pressure type fluid bearing for use in video tape recorders (hereinafter abbreviated to VTR) and provides a rotary head device which is compact and excellent in rotary performance.
BACKGROUND ART
In the conventional fluid bearing cylinder device, with its particular structure as shown in FIG. 1, a fixed shaft 2 is pressed in and secured in place at the central portion of a lower cylinder 1, a sleeve 3 is rotatably mounted on the fixed shaft 2, a thrust bearing seat 4 is screwed on the top of the fixed shaft 2 and a thrust bearing 5 is screwed on the upper end of the sleeve 3. Herringbone shape patterns of grooves 6A and 6B are formed on the fixed shaft 2 and a spiral groove 7 are formed on the lower surface of the thrust bearing 5 by etching, etc. The space inside the bearing chamber formed between the shaft 2 and the sleeve 3 contains lubricant 8, which is oil or grease, etc., thereby comprising a dynamic pressure type fluid bearing. A rotary magnetic head 10 is mounted on an upper cylinder, which is mounted on the sleeve 3. Also mounted on the sleeve 3 is a disc shape rotary transformer 11 on the rotary side of the rotary head device for transmitting to the stationary side an electrical signal extracted from a magnetic tape through the magnetic head 10, not shown in the drawings. An armature magnet 13 is supported on a magnet case 14 of a motor attached to a lower end of the sleeve 3, which together with the parts mentioned above comprise a rotary side unit 20. On the other hand, inside the lower cylinder 1 is mounted a disc shape rotary transformer 12 on the stationary side of the rotary head device which receives the aforementioned electric signal. Also inside the lower cylinder 1, there is secured a motor stator 19 consisting of an iron plate 18, a printed substrate 17 and a coil 16. As the motor is energized under this state, the rotary unit 20 begins turning, producing a pressure by a pumping action of the patterns of grooves 6A, 6B and 7; then, the unit is floated up by the rising rigidity of the oil film, thereby enabling rotation of the rotary side unit 20 without making contact with the stationary side unit. Under this condition, the force of the armature magnet 13 to attract the iron plate 18 and the dead weight of the rotary side unit is exerted in the direction of B, as shown in FIG. 1, while a force opposing them is produced in the direction A due to the pumping action of the spiral groove 7.
However, in such a structure as described above, the dimension in the axial direction is large, thus detracting from compactness of the device. When the device is tilted sideways by 90 degrees to its horizontal position, as shown in FIG. 2, the fixed shaft 2 tends to be warped due to the dead weight of the rotary unit and the side pressure by a magnetic tape 60, causing a large shift in the relative position between the magnetic head 10 and the magnetic tape 60. As a consequence, the picture recorded by the VTR cannot be reproduced. For those and other such reasons, the structure was determined to be unacceptable in its performance as a portable VTR.
SUMMARY OF THE INVENTION
The present invention resides in a rotary head device using a dynamic pressure type fluid bearing having a lower cylinder, a rotary shaft which rotates in a sleeve placed at the center of the lower cylinder, an upper cylinder mounted on one end of the rotary shaft and having a head, a motor installed on the other end of the rotary shaft, with herringbone groove patterns formed on either one of the rotary shaft or the inner surface of the sleeve, the axial length of the herringbone groove pattern being larger on the upper cylinder side, but smaller on the motor side, said device including a pair of cylindrical rotary side and a pair of stationary side cylindrical rotary transformers.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a sectional view of a conventional fluid bearing cylinder;
FIG. 2 is a sectional view of a the principal part of t
REFERENCES:
patent: 3494674 (1970-02-01), Muijderman et al.
patent: 3763327 (1973-10-01), Hescher
patent: 4031558 (1977-06-01), Kusaka
patent: 4080639 (1978-03-01), Gunschmann
patent: 4099210 (1978-07-01), Dolby
patent: 4197565 (1980-04-01), Watanabe
patent: 4408239 (1983-10-01), Ushiro
Asada Takafumi
Hosokawa Yoshiteru
Shioyama Tadao
Yoshida Cyuryo
Hecker Stuart N.
Matsushita Electric - Industrial Co., Ltd.
Urcia Benjamin E.
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