Optical disc cartridge

The present invention discloses an optical disc cartridge housing therein a magneto optical disc, wherein, a second opening for a magnetic head of the case to access is formed joining with a notch formed at an end surface of the case, and also a notch coordinating with the second opening is formed at a shutter when the shutter is at a position for opening. Thereby, it is unnecessary for the magnetic head to rise and fall in such a case where the optical disc cartridge is inserted into the optical disc driving unit, and the magnetic head accesses the magneto optical disc.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to an optical disc cartridge, particularly, 
to improvements of openings for magnetic head and of a shutter. 
2. Description of the Prior Art 
FIG. 1 is a perspective view showing a construction of a conventional 
optical disc cartridge, and FIG. 2 is a sectional view of the above cut 
off through II--II line shown in FIG. 1. In FIG. 1, reference numeral 1 
indicates a plastic case of an optical disc cartridge wherein a magneto 
optical disc 3 is housed. The case 1 is shaped like a flat board being 
hollow inside with a thickness of several mm, comprised of two flat 
members, that is, upper case 15 and lower case 16. At the lower case 16, a 
first opening including a rectangular hole 6 and a center hole 8 is 
formed. The first opening 4 is for an optical head (not shown) to access, 
and the width and length thereof are those which are enough for the 
optical head to access the magneto optical disc 3. Also, at the upper case 
15, a second opening 5 of the same shape as that of the first opening is 
formed. The second opening 5 is for a magnetic head 10 to access, and the 
width and length thereof are those which are enough for the magnetic head 
10 set up on an arm 9 shown in FIG. 2 to access the magneto optical disc 
3. And, the upper case 15 has a thickness of l.sub.1. 
A shutter 2 of stainless steel thin board, which closes both the openings 4 
and 5 of the case 1 when an optical disc cartridge is taken out of the 
disc driving unit, is set up at one end of the case 1 so that it, having a 
section of U shape, has both faces of the case therebetween. The shutter 2 
is installed so that it moved freely between a position for closing both 
openings 4 and 5 and a position for opening them. It is usually energized 
at the position for closing by means of a spring 11 (refer to FIG. 3). An 
aperture 7, facing the first opening 4 of the case 1 when the shutter 2 is 
at the position for opening and being the same shape as the first opening, 
is formed at the shutter 2, the magnetic head 10 accessing the magneto 
optical disc 3 therefrom. FIG. 3 through FIG. 6 show the case and the 
shutter in detail used in the case described above. FIG. 3 shows a plan 
view of the upper case 15 side of the optical disc cartridge, when the 
shutter 2 is at the position for closing. In the figure, reference numeral 
11 is a spring which changes its shape by the movement of the shutter 2, 
and energizes the shutter 2 at the position for closing the opening 5. 
FIG. 4 shows a plan view of the lower case 16 side of the case 1. In the 
case of an optical disc cartridge, FIG. 4 shows the side of an optical 
head. In the figure, numeral 6 indicates a rectangular aperture used when 
an optical head (not shown) is inserted, and 8 indicates a circle aperture 
joining with the rectangular aperture, used for inserting a mount for 
fitting a magneto optical disc when the magneto optical disc is driven by 
a motor (not shown). These two apertures form a first opening 4. FIG. 5(a) 
is an enlarged view of the E portion in FIG. 4, and FIG. 5(b) is a plan 
view in the case where the FIG. 5(a) is taken as a front view and FIG. 
5(c) is a sectional view when cut off through the K--K line shown in FIG. 
5(b). In these figures, numeral 25 indicates an outside board of the lower 
case 16, and since a notch 16b is formed at an end side of the aperture 6 
of the first opening 4, the outside board 25 is thinner by a predetermined 
length than the other part 24 of the lower case 16. This leads an optical 
head to smooth accessing. FIG. 6(a) is a plan view showing a conventional 
shutter, FIG. 6(b) is a left side view of the above, and FIG. 6(c) is a 
sectional view of the above cut off through the M--M line shown in FIG. 
6(a). The under face 33 of the lower case 16 side of the shutter 2 is 
narrower in width in comparison with the top face 34 of the upper case 15 
side, an aperture 7 of approximately the same shape as the second opening 
5 of the upper case being formed at the top face 34. At the under face 
side of connecting portion 27 of the top face 34 with the under face 33, a 
notch 18 is formed having a width being the same as that of the aperture 7 
and a depth corresponding to the notch 16b of the outside board 25 of the 
lower case 16. 
Generally, a magnetic head is used for generating a biased magnetic field 
for overwriting. Since the magnitude of the magnetic field which is 
generated by a slider type magnetic head is small, it cannot be kept away 
from a recording medium as an optical head is. So, slider-type magnetic 
head 10 impresses a magnetic field in the state that it rises several 
through ten-odd .mu.m above a recording medium by means of dynamic 
pressure. (Fixed-type magnetic head is used in the state that it is kept 
about tens through 100 .mu.m apart from a recording medium.) Accordingly, 
in the conventional magneto optical disc, since the opening 5 is formed 
only on one side surface of the case, when an optical disc cartridge for a 
magneto optical disc is inserted into the disc driving unit, the magnetic 
head 10 needs to get over the end surface of the case 1, therefore causing 
a problem that the elevating mechanism has to be set up on an arm 9. This 
leads to a large-sized disc driving unit and complicated driving system of 
magnetic head. 
Since the distance between the magnetic head 10 and the recording medium is 
very close, there is a problem that, in the case where the air inflowing 
from outside of the optical disc cartridge includes dust, the dust results 
in cutting off the air flow, thereby prohibiting the magnetic head 10 from 
rising and sometimes causing the magnetic head to fall down on the 
recording medium. Also, there is a problem that air flow is not stabilized 
on the surface of the recording medium which faces the magnetic head 10, 
since there is no air intake in the upper case 15. 
SUMMARY OF THE INVENTION 
The present invention has been devised to solve the problems of the 
aforesaid prior art and, therefore, it is a primary object of the present 
invention to provide an optical disc cartridge which can do without an 
elevating mechanism of a magnetic head by joining an opening for the 
magnetic head with a notch formed at one end surface thereof and by 
forming a notch at a shutter coordinating with the above notch. 
It is another object of the present invention to provide an optical disc 
cartridge which controls the movement of a shutter and whose connecting 
part is strengthened by forming a groove at one end surface of the case 
and by forming a bending portion which engages with the above groove at a 
joining portion of the shutter having the case there-between. 
It is a further object of the present invention to provide an optical disc 
cartridge which supplies clean air all over the surface of a magneto 
optical disc facing a magnetic head by providing an air intake with a 
filter at the surface of an optical disc cartridge facing the magnetic 
head. 
The above and further objects and features of the invention will more fully 
be apparent from the following detailed description with accompanying 
drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Hereinafter, a detailed description is made of the present invention in 
reference to drawings showing embodiments thereof. 
FIG. 7 is a perspective view showing a construction of an optical disc 
cartridge of the present invention. FIG. 8 is a cross-sectional view of 
the embodiment of the invention shown in FIG. 7. In the figures, reference 
numeral 1 indicates a plastic case of an optical disc cartridge wherein a 
magneto optical disc 3 is housed. The case 1 is shaped like a flat board 
being hollow inside with a thickness of several mm, comprised of two flat 
members, that is, upper case 15 and lower case 16. At the lower case 16, a 
first opening 4 including a rectangular hole 6 and a center hole 8 is 
formed. The first opening 4 is for an optical head to access, and the 
width and length thereof are those which are enough for the optical head 
to access a magneto optical disc 3. Also, at the upper case 15, a second 
opening 5 for a magnetic head 10 is formed. The second opening 5 is joined 
with a notch 15b which is a cut-off portion of an end surface 15a of the 
upper case 15, being opened with a length which is enough for a magnetic 
head 10 to access the inmost track of the magneto optical disc 3. The 
width of the opening 5 is determined so that the slider-type magnetic head 
10 which is set up on an arm 9 shown in FIG. 8 can access all the track of 
the magneto optical disc, at the position where the magnetic head 10 faces 
an optical head 18. Thickness l.sub.2 of the case in the figure is thinner 
than that l.sub.1 of the conventional case by the length cut off. 
On the other hand, numeral 2 indicates a shutter, 17 indicates a notch at 
the upper case 15 side of the shutter; 2, 27 shows a bridge at the one end 
surface side of the case. The shutter 2 of stainless steel thin board, 
which closes both the openings of the case 1 when an optical disc 
cartridge is taken out of the disc driving unit, is set up at one end of 
the case 1 so that it, having a section of U shape, have both faces of the 
case therebetween. The shutter 2 is installed so that it moves freely 
between a position for closing both openings 4 and 5 and a position for 
opening them. It is usually energized at the position for closing by means 
of a spring (not shown). When the shutter 2 is at a position for opening, 
an aperture 7, facing the second opening 5 of the case 1, being wider in 
width and joining with a notch 17 engaging with a notch 15b of the upper 
case 15, is formed. Also, a notch 18, which faces a notch 16b of the lower 
case 16, is formed. 
FIG. 9 is a plan view of the lower case 16 side of the case 1. In the case 
of a magneto optical disc, FIG. 9 shows the side of an optical head. In 
the figure, reference numeral 6 indicates a rectangular aperture used when 
an optical head 11 is inserted, and 8 indicates a circle aperture joining 
with the rectangular aperture, used for inserting a mount for fitting a 
magneto optical disc when the magneto optical disc is driven by a motor 
(not shown). These two apertures form a first opening 4. And in the 
vicinity of an end portion of inserting side at the lower case 16, a guide 
groove 16a of the shutter 2 is formed. 
FIG. 10(a) is an enlarged view of the C portion of FIG. 9, FIG. 10(b) is a 
plan view in the case where the FIG. 10(a) is taken as a front view, and 
FIG. 10(c) is a sectional view when cut off through the G--G line in FIG. 
10(b). In these figures, reference numeral 25 is an outside board of the 
lower case 16, and since a notch 16b is formed at an end side of the 
aperture 6 of the first opening 4, the outside board is thinner by a 
predetermined length than the other part 24 of the lower case 16. This 
leads an optical head to smooth accessing. Also, at an end surface of the 
lower case 16, a groove 23 flush with the notch 16b of the outside board 
25 is formed, with which an under board 26 of the shutter 2 to be 
described later is engaged. And an end surface of the upper case 15, a 
notch 15b is formed, joining with the second opening 5. The width of the 
notch 15b is a little larger than the largest width of the magnetic head 
10, therefore, it is not necessary for the magnetic head 10 to rise and 
fall to get over the end portion 15a of the upper case 15. 
FIG. 11 and FIG. 12 are plan views showing a construction of a shutter. 
FIG. 11(a) is a plan view of the shutter viewed from the lower case side, 
FIG. 11(b) is a sectional view of the shutter cut off through A--A line in 
FIG. 11(a). FIG. 12(a) is a plan view of the shutter viewed from the upper 
case side, FIG. 12(b) is a front view of the shutter, and FIG. 12(c) and 
FIG. 12(d) are cross-sectional views of the shutter as seen through the 
F--F line and D--D line in FIG. 12(a). An under face 33 at the lower case 
16 side of the shutter 2 is narrower in width when compared with a top 
face 34 of the upper case 15 side. At the top face 34, an aperture 7 of 
approximately the same shape as the second opening 5 of the upper case 15 
is formed. At the under face side of a connecting portion 27 of the top 
face 34 with the under face 33, a notch 18 having a same width as the 
aperture 7 and a depth corresponding to the notch 16b of the outside board 
25 of the lower case 16 is formed. At the edge of the connecting portion 
27, the under board 26 which is bent into L-shape is formed and is to be 
engaged with the aforesaid groove 23. Also, at the top face 34 side of the 
connecting portion 27, a notch 17 of approximately the same width as that 
of the notch 15b joining with the second opening 5 is formed. Also, at 
both ends of the under face 33, a guide claw 28 which is bent into L-shape 
is formed. The claw 28 engages with the guide groove 16a to guide the 
movement of the shutter 2. 
When an optical disc cartridge of the above construction is set in a disc 
driving unit (not shown), the shutter 2 is moved from a position for 
closing to a position for opening by means of a driving means provided in 
the disc driving unit, and the aperture 7 of the shutter 2 and the second 
opening 5 of the upper case 15 coordinate with each other. At that time, 
since the notch 15b and the notch 17 are formed at the end portion 15a of 
the upper case 15 and at the connecting portion 27 of the shutter 2, 
respectively, and the thickness of the end portion of the case 1 is 
thinner than the conventional one, the magnetic head 10 is arranged on the 
recording medium 3 without getting over the end surface of the case 1. 
Next, explanation will be given of another embodiment of the invention. 
FIG. 13(a) is a plan view showing a construction of a shutter of an 
optical disc cartridge of another embodiment, FIG. 13(b) is a side view 
thereof, and FIG. 13(c) is a sectional view of the shutter cut off through 
the H--H line in FIG. 13(a). In this embodiment, unlike the aforesaid 
embodiment, an under board 26 which is bent is not formed, and a notch 17 
has a same width with that of an aperture 7, thereby, simplifying 
manufacturing and reducing the cost. But the strength for bending lowers 
because the width of end face 27 is narrow and is not bent. 
From this point of view, the first embodiment shown in FIG. 11 and FIG. 12 
has few problems conserning strength because it has a section of L-shape 
and C-shape. It is also capable of having a function for positional 
controlling by moving the shutter 2 with making the under board 26 go 
along with the groove 23. FIG. 14 is a drawing showing a further 
embodiment wherein the width of opening is reduced corresponding to the 
size of the magnetic head. Since thickness of the shutter is thin, being 
usually about 0.3 mm, the above method increases the strength. In the 
figure, reference numeral 7 is an aperture. 
As mentioned above, the present invention has advantage. For example, there 
is no need for an arm which upholds a magnetic head to have a function for 
rise and fall. A disc driving unit can be small-sized and accessing time 
can be reduced, by forming an opening for accessing the magnetic head by 
cutting off an end of a case. At this time, a groove, which has been 
formed at the case, has also an effect for positional controlling of the 
movement of the shutter. 
Next, the second embodiment of the present invention will be explained. 
FIG. 15 is a perspective view showing a construction of an optical disc 
cartridge related to the second invention, and FIG. 16 is a sectional view 
of the optical disc cartridge cut off through the XVI--XVI line in FIG. 1. 
In the figures, reference numeral 1 indicates a plastic case of an optical 
disc cartridge wherein a magneto optical disc 3 is housed. The case is 
shaped like a flat board being hollow inside with a thickness of several 
mm, and a rectangular first opening 4 including a center hole 8 is formed 
at one surface. The first opening 4 is for an optical head 11 to access, 
and the width and length thereof are those which are enough for the 
optical head 11 to access the magneto optical disc 3. FIG. 17 is an 
enlarged plan view showing the shape of a second opening when the shutter 
is positioned at the opening. At the other surface of the case 1 is formed 
the second opening 5 for the magnetic head 10 having a smaller width than 
that of the first opening 4. The second opening 5 is joined with a notch 
15b which is a cut off portion of an end surface of the case 1, being 
opened with a length which is enough for a magnetic head 10 to access the 
inmost track of the magneto optical disc 3 in the vicinity of the center 
position at the other surface. The width of the second opening 5 is 
determined so that the slider-type magnetic head 10 which is set up on an 
arm 9 shown in FIG. 17 can access all the track of the magneto optical 
disc at the position where the magnetic head 10 faces an optical head 11. 
Furthermore, the second opening 5 is formed asymmetrically in width to the 
dimensional center line L--L of the case 1, and the relationship between 
the distance m.sub.2 from an end portion of upstream side of the magneto 
optical disc 3 in the rotational direction shown as an arrow "A" to the 
center line L--L and the distance m.sub.1 from an end portion of 
downstream side to the center line L--L is m.sub.1 &lt;m.sub.2. 
At the surface of the second opening 5 side of the case 1, a round shape 
air intake 30 is formed with the rotational center of the magneto optical 
disc 3 as the center position, the air intake 30 being provided with a 
filter 31 having numerous meshes of about 0.5 .mu.m. 
On the other hand, a shutter 2 of stainless steel thin board, which closes 
both the openings 4 and 5 of the case 1 when an optical disc cartridge is 
taken out of the disc driving unit, is set up at one end 1a of the case 1 
so that it, having a section of U-shape, has both faces of the case 
therebetween. The shutter 2 is installed so that it move freely between a 
position for closing both openings 4 and 5 and a position for opening 
them. It is usually energized at a position for closing by means of a 
spring (not shown). At the shutter 2, an aperture 7 coordinating with the 
second opening 5 of the case 1 when the shutter 2 is at the position for 
opening, being the same shape as the opening 5, and having a notch 17, is 
formed. 
FIG. 18 is a side sectional view showing the relationship between a 
magnetic head and a magneto optical disc. The magnetic head 10 is 
comprised of a slider portion 10a which rises by dynamic pressure caused 
by rotation of the magneto optical disc 3, and a head portion 10b which is 
approximate C-shape with the upper end thereof being fixed to the slider 
portion 10a, having a predetermined gap 22 between a lower end thereof and 
the slider portion 10a. By coinciding the center position of the gap 22 on 
the center line L--L shown in FIG. 17, the spot position of the optical 
head 11 corresponds to the center position of the gap 22. The relationship 
between the distance m.sub.1 and the distance m.sub.2 must be determined 
in proportion to the distance n.sub.1 from the center position of the gap 
22 to the end portion of the head portion 10b, and the distance n.sub.2 
from the center position of the gap 22 to the end portion of the slider 
portion 10a. 
Next, explanation will be given on its operation. FIG. 19 is a plan view of 
an optical disc cartridge, showing air flow taken into the case. Air taken 
in from the air intake 30 has dust removed by a filter 31, cleansed and 
then supplied onto the magneto optical disc 3. The supplied air proceeds 
from the center to the periphery by means of the rotation of the magneto 
optical disc 3, and is diffused uniformly as shown by an arrow "B", 
forming stabilized air flow. By means of dynamic pressure, the magnetic 
head 10 rises keeping the gap between the magneto optical disc 3 and 
itself constant. When an optical disc cartridge is set in the disc driving 
unit (not shown), the shutter 2 is moved from the position for closing to 
the position for opening, and the notch 17 of the shutter 2 coordinates 
with the second opening 5 of the case 1. The magnetic head 10 is arranged 
on the magneto optical disc 3 without getting over the end surface of the 
case 1 since the notch 15b of the case is opened. 
Furthermore, in this embodiment, although the air intake is a circle in 
shape, and the center position thereof is the rotational center of the 
magneto optical disc, this invention is not limited to this embodiment. 
The air intake may not be a circle in shape, and the center position may 
not coincide with the rotation center. 
As described heretofore, according to the second invention, it is possible 
to supply clean air from the center of the magneto optical disc to its 
periphery, and to make the air flow uniform and stabilized. 
Furthermore, the shutter is made of stainless steel in the inventions 
described above, however the material of the shutter may not only be 
stainless steel but instead a synthetic resin. 
As this invention may be embodied in several forms without departing from 
the spirit of essential characteristics thereof, the present embodiment is 
therefore illustrative and not restrictive, since the scope of the 
invention is defined by the appended claims rather than by the description 
preceding them, and all changes that fall within the meets and bounds of 
the claims, or equivalence of such meets and bounds thereof are therefore 
intended in be embraced by the claims.