Magnetic disk cartridge

A magnetic disk cartridge retains a rotational magnetic disk in a case through liners, which contact the associated surfaces of the disk and each have multiple long protrusions formed almost uniformly and almost in parallel to one another on the whole surface on the disk side. As the magnetic disk rotates, the angle of the disk surface contacting the long protrusions can gradually change, thus ensuring removal of dust from the disk. In additon, this structure can reduce the frictional resistance between the liner's surface and magnetic disk, which contributes to faster rotation of the disk.

BACKGROUND OF THE INVENTION 
(1.) Field of the Invention 
The present invention relates to a magnetic disk cartridge which 
magnetically records and holds information. 
(2.) Description of the Related Art 
A conventional magnetic disk cartridge is designed as follows. 
In general, nonwoven fabric liners are adhered respectively to the inner 
surfaces of a separate type plastic cases, with a rotatable magnetic disk 
disposed therebetween in such a way that the surfaces of each liner may 
contact the both sides of the magnetic disk. The liners each serve as 
cleaning sheet and a prevention against abrasion of the magnetic disk 
surfaces. 
The liner may be designed as disclosed in Japanese Unexamined Utility Model 
Publication No. Sho 63-52184 in such a manner as to have three long 
protrusions formed thereon protruding on the magnetic disk side and 
extending radially. 
With the use of such a liner, the long protrusions strongly contact with 
the magnetic disk to clean the disk surface while the other portion of the 
liner touches the disk very lightly, resulting in a small frictional 
resistance. The liners will not interfere with the fast rotation of the 
magnetic disk. 
Since the long protrusions on each liner of the conventional magnetic disk 
cartridge extend radially, however, when the magnetic disk rotates, the 
surface of the disk always contacts the radial long protrusions at almost 
the same angle. The contacting pattern does not therefore change, making 
the liners exert an insufficient effect to clean the magnetic disk. 
In addition, to form the long protrusions radially on the liner, it is 
necessary to cut a rolled liner sheet in a disk shape before forming 
radial long protrusions on the cut liner by pressing, or after forming 
radial long protrusions on the liner sheet. In this method, centering of 
the disk shape liner is indispensable and therefore the productivity of 
magnetic disk cartridge will be remarkably reduced. 
SUMMARY OF THE INVENTION 
It is therefore an object of the present invention to provide a magnetic 
disk cartridge which can enhance the effect of cleaning a magnetic disk 
without interfering with the fast rotation of the disk. It is another 
object of the present invention to provide a magnetic disk cartridge with 
high productivity. 
To achieve the objects, a magnetic disk cartridge according to the present 
invention comprises a case; liners disposed in the case; and a magnetic 
disk accommodated rotatably in contact with surfaces of the liners in the 
case, the liners each having multiple long protrusions formed all over a 
surface on a magnetic disk side almost uniformly and almost in parallel to 
one another. 
The protrusions may be formed to extend linearly. 
It is preferable that at least one of the long protrusions passes a center 
hole of each liner, or that at least one of the long protrusions contacts 
the center hole of the liner. 
In addition, it is preferable that an interval between adjoining long 
protrusions be set smaller than a diameter of the center hole of each 
liner. 
Further, it is also preferable that the long protrusions be formed in a 
zigzag pattern in a plain parallel to the surface of the magnetic disk. 
The long protrusions may be formed in a sinusoidal or sawtooth pattern. 
Furthermore, each long protrusion may be discontinuous. In this case, it is 
preferable that at least one substantial long protrusion portion is 
positioned on all rotational loci of the surface of the magnetic disk. 
With any of the long protrusion patterns described above, it is possible to 
gradually change the angle of the disk surface contacting the long 
protrusions as the magnetic disk rotates. This can significantly improve 
the effect of dust removing. In addition, because other portions of the 
liner but the long protrusions lightly contact the magnetic disk, the 
frictional resistance to the magnetic disk can be reduced, which 
contributes to faster rotation of the disk. 
Accordingly, it is possible to provide a high-quality magnetic disk 
cartridge which can surely avoid a read/write error caused by dust. 
In manufacturing a magnetic disk cartridge, a liner sheet with long 
protrusions uniformly formed thereon can be cut anywhere in a disk shape 
to provide liners without requiring the centering process mentioned above, 
thus resulting in higher productivity and lower manufacturing cost. 
The structural features of the present invention and the action and effects 
based on the features will be apparent from the following description of 
the preferred embodiment in conjunction with the accompanying drawings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
A preferred embodiment of the present invention will now be described 
referring to FIGS. 1 through 10. 
As shown in FIGS. 1 and 2, a magnetic disk 1 has a hub 2 formed in its 
center to rotate the disk and is retained in plastic cases 3 and 4 of a 
separate type. 
Liners 5 and 6, respectively adhered to the inner walls of the cases 3 and 
4, each have multiple linear long protrusions 7 formed in parallel and 
uniformly in its whole surface on the side of the magnetic disk 1, as 
shown in FIG. 3. 
Further, the liners 5 and 6 have gaps 9 provided where they correspond to 
head windows 8 of the cases 3 and 4, and have central openings 10 facing 
the hub 2 of the magnetic disk 1. 
A sliding shutter 11 opens and closes the head windows 8, and the cases 3 
and 4 are ultrasonically fused together at their four corners. 
The long protrusions 7 are determined according to their width W1 and 
height H, and the width W2 of the groove defined by the adjoining long 
protrusions. Through various experiments conducted, it was found that 
designing of the long protrusions 7 as follows could permit the magnetic 
disk to be efficiently cleaned and protected. The dimensions of the long 
protrusions 7 can vary regardless of presently available disk sizes, such 
as 3.5 inches, 5.25 inches and 8 inches. Figures in the parentheses are 
more preferable values. 
Protrusion Width W1: 1 to 10 mm (2 to 6 mm) 
Protrusion Height H: 0.3 to 2.0 mm (0.5 to 1.6 mm) 
Groove Width W2: 1 to 20 mm (2 to 10 mm) 
Too many protrusions 7 or the exceedingly high protrusions 7 would increase 
the rotational torque of the magnetic disk 1 and damage the magnetic disk 
1. In general, as the width of the grooves, W2, (interval between the long 
protrusions) increases, it is better to set the height H of the 
protrusions greater. As the width W2 decreases, it is better to reduce the 
height H. 
Such a width and height need to be determined in light of the material and 
thickness of the liners 5 and 6, the size of the magnetic disk 1, etc. 
Since the protrusions 7 are formed linear and parallel to one another as 
described above, the angle of the surface of the magnetic disk 1 
contacting the individual protrusions 7 gradually varies in accordance 
with the rotation of the magnetic disk 1. Accordingly, the pattern of the 
magnetic disk 1 contacting the protrusions 7 can be changed, making it 
possible to surely clean the surfaces of the magnetic disk 1. 
More specifically, as shown in FIG. 3, the magnetic disk 1 contacts a 
protrusion A among the protrusions 7 at almost right angles, but as the 
magnetic disk 1 contacts protrusions B, C and D its contact angle becomes 
acuter. 
The magnetic disk 1 very lightly contacts the liners 5 and 6 where the 
protrusions 7 are not present (or the groove portions), allowing the 
magnetic disk 1 to rotate at a high speed. 
To provide the liners 5 and 6, a roll of a nonwoven fabric for liners, made 
of polyester or rayon texture, pressed on one side with a metal plate to 
form the protrusions 7 with predetermined size and density, is cut in 
almost disk shapes. 
Compared with the conventional method for forming radial protrusions, this 
method requires no centering process in cutting the liners. Productivity 
therefore improves signigicantly, contributing to the reduction of the 
manufacturing cost. 
FIG. 5 through 10 illustrate different shapes of the liners 5 and 6 as 
modifications thereof. 
As long as size and density of the long protrusions 7 extending in parallel 
are properly determined to efficiently clean and protect the magnetic disk 
1, the long protrusions 7 may be formed in any direction, lateral 
horizontal or diagonal. Further, the long protrusions 7 should not 
necessarily extend continuously. They may be formed discoutinuous as shown 
in FIGS. 8 and 9 (indicated by S), or may be formed to be parallel 
sinusoidal waves as shown in FIG. 10. The long protrusions may be formed 
in a sawtooth pattern instead of the sinusoidal one. 
With those modified liners, it is possible to produce the same effects as 
acquired by the first type of produce the same effect as acquired by the 
first type of liners.