Dynamic magnetic information storage or retrieval – Head – Head accessory
Reexamination Certificate
2001-03-30
2004-05-18
Davis, David (Department: 2652)
Dynamic magnetic information storage or retrieval
Head
Head accessory
Reexamination Certificate
active
06738224
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a magnetic tape device, and more particularly to a magnetic tape device comprising a tape guide, which is suitable for the high-speed travel of a magnetic tape.
2. Description of the Related Art
A magnetic tape device utilizes a magnetic tape, which is a tape-shaped magnetic recording medium, makes the magnetic tape travel while being guided by rotating tape guides (roller guides), and reads/writes data by using a magnetic head in relation to the magnetic tape thereof.
A magnetic tape is guided within a tape travel path by a plurality of tape guides. This magnetic tape is housed in a tape cartridge. The magnetic tape is wound around a file reel disposed inside the cartridge. The cartridge is introduced into the inside of a magnetic tape device by a loader. The magnetic tape housed inside the cartridge is attached to a machine reel by having the end thereof guided by a threader. The machine reel takes up the magnetic tape wound around the file reel.
FIG. 8
is a block diagram showing one example of the placement of tape guides and a magnetic head, which constitute a magnetic tape device. In
FIG. 8
, tape guides
1
L,
1
R are lined up in the direction of travel of the magnetic tape and positioned on a base
3
. A magnetic head
2
is affixed on the base
3
between tape guides
1
L and
1
R. Magnetic head
2
can perform data read/write by arbitrarily selecting any one of a plurality of tracks (for example, 24). That is, there is provided a plurality of playback head portions
2
a
and recording head portions
2
b
for each track.
FIG. 9
is a cross-sectional view showing one example of a conventional tape guide. In
FIG. 9
, a tape guide
1
comprises a fixed shaft
10
. This fixed shaft
10
is affixed to a base
3
. Two bearings
11
,
11
′ support a rotating shaft
12
rotatably around fixed shaft
10
. This rotating shaft
12
is a so-called cylindrical roller. The peripheral surface
12
a
of this roller
12
is a guide surface for guiding a magnetic tape. Peripheral surface
12
a
of roller
12
guides a magnetic tape in a state in which same makes contact with the recording surface of the magnetic tape. Roller
12
rotates in accordance with the frictional force between the magnetic tape and roller
12
when the magnetic tape travels. The rotational speed of peripheral surface
12
a
of roller
12
becomes the same as the travel speed of the magnetic tape. A lower flange
13
is affixed to the bottom side of fixed shaft
10
. An upper flange
14
is disposed on the top side of fixed shaft
10
. Upper flange
14
comprises a movable portion
14
b
, a fixed portion
14
a
and a coil spring
15
. Fixed portion
14
a
is affixed to a small diameter portion
10
a
of fixed shaft
10
. Movable portion
14
b
is fitted onto the small diameter portion
10
a
so as to be capable of moving up and down along the small diameter portion
10
a
. Coil spring
15
biases movable portion
14
b
toward a step portion
16
of fixed shaft
10
. The force by which coil spring
15
biases movable portion
14
b
constitutes a force for biasing a magnetic tape to lower flange
13
. Movable portion
14
b
is capable of moving up and down along the small diameter portion
10
a
of fixed shaft
10
. Movable portion
14
b
, under the biasing force of coil spring
15
, is hit against step portion
16
of fixed shaft
10
. Applying suitable biasing force in accordance with coil spring
15
enables a magnetic tape to be made to travel along lower flange
13
. Because a magnetic tape will not be biased to lower flange
13
if the biasing force is too weak, a magnetic tape will slip out of position in the up-down direction of the roller guide during tape travel. Slippage causes uneven winding on the take-up reel, and becomes a cause of the edges of a magnetic tape folding. Further, if the biasing force is too strong, there is the danger of the edges of a magnetic tape being either folded or scraped, and of a magnetic tape being destroyed.
In a magnetic tape device of this kind, in order for magnetic tape read/write processing to be carried out faster, it is necessary for a magnetic tape to be made to travel at higher speed.
However, the problem is that a conventional tape guide (roller guide) has low endurance to highspeed rotation, and the life of a conventional tape guide decreases when it is rotated at high speed.
Meanwhile, a hydrobearing guide is well-known as a tape guide for use in place of a roller guide, which rotates in accordance with the travel of a magnetic tape. A hydrobearing guide is constituted from, for example, a ceramic, and because it does not rotate in accordance with magnetic tape travel, has high durability. The peripheral surface of a hydrobearing guide has a circular arc surface for guiding a magnetic tape along the tape travel path, and it is known that when a magnetic tape is made to travel at high speed, the magnetic tape travels by levitating without coming into contact with the circular arc surface. The following expression is known as an expression for approximating the degree of levitation of a magnetic tape.
Degree of levitation expression
h−
0.643
r
(6
&mgr;V/T
)
⅔
h: degree of levitation, r: radius of curvature of guide, &mgr;: viscosity of air, V: tape travel velocity, T: tape tension
By making a magnetic tape travel by levitating in relation to a tape guide, the magnetic tape does not come in contact with the circular arc surface, thus enabling the prevention of magnetic tape friction during highspeed travel. Based on the above expression, the larger the circular arc radius of the circular arc surface (the radius of curvature r of the above-mentioned expression) at this time, the greater the degree of levitation of a magnetic tape in relation to the circular arc surface. Therefore, to ensure the required degree of levitation, it is necessary that the circular arc that forms the tape travel path be set to a predetermined radius.
However, when a magnetic tape is being wound onto the take-up reel, or in the interval until a stopped magnetic tape achieves highspeed travel, and furthermore, in the interval until a magnetic tape travelling at high speed is stopped, the magnetic tape travels by making contact with the circular arc surface (According to the above-mentioned expression, the degree of levitation is proportional to the tape travel speed, and when the tape travel speed is slow, a magnetic tape is not levitated.) To curb as much as possible the friction of a magnetic tape resulting from the magnetic tape traveling by making contact with the circular arc surface, it is necessary to improve as much as possible the relative surface roughness of the circular arc surface of a hydrobearing guide.
However, the problem is that, when the relative surface roughness of the circular arc surface is improved, when a magnetic tape comes in contact with the circular arc surface, the magnetic tape sticks to the circular arc surface. When an attempt is made to make a magnetic tape travel after the magnetic tape has been stuck to the circular arc surface one time, the magnetic tape either breaks or stretches, causing the magnetic tape to be damaged.
The sticking of a magnetic tape tends to occur more readily the larger the contact surface area of the magnetic tape and circular arc surface. To make the contact surface area smaller, it is necessary to make the circular arc radius of the circular arc surface smaller, but by so doing, as explained hereinabove, it becomes impossible to make a magnetic tape travel so that it levitates at a sufficient degree of levitation.
SUMMARY OF THE INVENTION
Therefore, an object of the present invention is to provide a magnetic tape device, which is capable of making a magnetic tape travel stably without being stuck to a hydrobearing guide.
A magnetic tape device of the present invention comprises a magnetic head for performing read/write operation to a magnetic tape traveling a tape travel path, and tape guides, each of which has a guide sur
Davis David
Fujitsu Limited
Greer Burns & Crain Ltd.
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