Rotary head cylinder device with fluid bearing

Details Rotary head cylinder device with fluid bearing Rotary head cylinder device with fluid bearing

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, 36013074, G11B 552, G11B 2104, G11B 1561

Patent

active

047061430

DESCRIPTION:

BRIEF SUMMARY
TECHNICAL FIELD

The present invention relates to a rotary head cylinder device used in video tape recorders, etc., having a dynamic pressure type radial fluid bearing (hereinafter referred to as fluid bearing cylinder device) and provides a fluid bearing cylinder device which is thin and has high rotational precision, realized by utilizing cylindrical rotary transformers and by making the surface areas different between two herringbone patterns of grooves in the radial fluid bearing.


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 shaped patterns of grooves 6A and 6B are formed on the fixed shaft 2 and a spiral groove 7 is 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 9, 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, not shown in the drawings, through the magnetic head 10. An armature magnet 13 is supported on an armature magnet case 14 of a motor attached to a lower end of the sleeve 3, which together with the other 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 arrow B as shown in FIG. 1, while a force opposing them is produced in the direction of arrow A as shown in this figure by the pumping action of the spiral groove 7. These forces are balanced and, as a result, the rotary side unit is rotated in a stable condition at a specified height.
With such a structure as described above, the rotary transformers 11 and 12 are in a disc shape, resulting in a thick fluid bearing cylinder device as a whole. Moreover, as shown in FIG. 2, when this device is tilted sideways by 90 degrees, the stationary shaft 2 tends to warp, causing a shift in the relative positions between the magnetic head 10 and the magnetic tape 60, thus interfering with normal play back, etc., of a video tape recorder (hereinafter abbreviated to VTR), etc. For a portable VTR, this device was inadequate with respect to its size and performance.


DISCLOSURE OF THE INVENTION

The device of the present invention comprises a lower cylinder, a fixed shaft supported at the bottom in a cantilever way, a sleeve rotatably fitted on the fixed shaft, a thrust bearing member secured on the upper end surface of the sleeve, at least one magnetic head and a motor securely held on the sleeve, rotary transformers, and an upper cylinder fixed on the sleeve or on the lower cylinder. The free axial end surface of the fixed shaft is used as a bearing surface and two herringbone shape groove patterns are formed on the outer

REFERENCES:
patent: 3420583 (1969-01-01), Hirs
patent: 3494674 (1970-02-01), Muijderman et al.
patent: 4099210 (1978-07-01), Dolby
patent: 4347536 (1982-08-01), Miyashita et al.
patent: 4408239 (1983-10-01), Ushiro
patent: 4487514 (1984-12-01), Mori
Chironis, "New Data on Gas Bearings", Product Engineering, Dec. 7, 1964.

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