Apparatus for loading a magnetic disc and for controlling the driving thereof

A hub holder which pushes the center hub of a magnetic disc to a reference surface for setting is associated with a cassette guide for guiding a magnetic disc cassette to a recording/reproducing position at which information is recorded or reproduced to or from the magnetic disc, so that the hub holder's displacement can be amplified by a required degree. An upper dust-proof door and a lower dust-proof door are swingably disposed at the cassette insertion opening of a magnetic disc unit, and they are normally so biased that they close the cassette insertion opening dust-tightly. When they are closed, one of them abuts against the other. Thus, the magnetic disc unit is compact in size and light in weight, easily clamps the center hub of the magnetic disc, and is closed in a completely dust tight manner.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a magnetic disc unit and more particularly 
to a magnetic disc unit of the type using a magnetic disc cassette of 
which a hard casing contains a magnetic disc as magnetic recording medium 
having a center hub. 
2. Description of the Prior Art 
There have been known a magnetic disc cassette of the type in which a 
magnetic disc with a center hub is contained in a hard casing. A 
conventional magnetic disc unit which loads the magnetic disc cassette of 
the type described for recording or reproducing information therein or 
therefrom has the following various disadvantages. 
In the conventional magnetic disc unit, after the magnetic disc cassette 
has been inserted into the magnetic disc unit, the magnetic disc is 
clamped by an additional operation of closing a door, rotating a lever or 
pushing a button. As a result, a large number of component parts are 
required, so that the magnetic disc unit is large in size and complicated 
in operation. 
In the conventional magnetic disc unit, in order to clamp a magnetic disc, 
a center cone fits in a center hole of a center hub of the magnetic disc, 
and pushes the center hub against a spindle. As a result, one set of 
clamping mechanism is needed which clamps the magnetic disc. Therefore, 
the magnetic disc unit cannot be made compact in size or thin and its 
mechanism is complicated. 
The conventional magnetic disc unit has one dust-proof door which is 
swingably attached to the cassette insertion opening. Such one dust-proof 
door results in a long radius of rotation when the door swings, so that a 
large space must be provided in order to allow the dust-proof door to 
swing, contrary to a recent tendency of making the magnetic disc unit more 
compact in size. 
In order to solve this problem, there has been proposed a set of an upper 
dust-proof door and a lower dust-proof door, but unless the mating edges 
of the upper and lower dust-proof doors are spaced apart from each other 
by a small gap, they cannot be opened or closed, so that dust particles 
enter the inside of the magnetic disc unit through the gap between them. 
In the conventional magnetic disc unit, photoswitches or microswitches are 
used to detect whether or not a magnetic disc cassette has properly been 
loaded at a suitable position. If the photoswitches are used, a light 
source and a photo detector must be disposed in opposite to each other, 
for example, in a vertical direction for the purpose of photo coupling, so 
that the magnetic disc unit become high and cannot be made compact in 
size. The same is true for microswitches. 
SUMMARY OF THE INVENTION 
It is, therefore one of the objects of the present invention to provide a 
magnetic disc unit which is compact in size and simple in construction. 
It is also an object of the present invention to provide a magnetic disc 
unit which facilitates and ensures the clamp of a magnetic disc. 
It is a further object of the present invention to provide a magnetic disc 
unit which can be closed in a dust tight manner. 
In order to attain these objects, a magnetic disc unit having a magnetic 
head for recording or reproducing information on or from a magnetic disc 
having a center hub and being accommodated in a cassette according to one 
aspect of the present invention comprises a cassette guide member for 
carrying the cassette in a manner that the cassette guide member moves the 
cassette to a predetermined position in the insertion direction of the 
cassette in accordance with the insertion of the cassette and for guiding 
the cassette to a recording/reproducing position at which information is 
recorded or reproduced on or from the magnetic disc; a spindle for 
rotating the magnetic disc; a hub holding member for pushing the center 
hub of the magnetic disc to the spindle to hold the magnetic disc between 
the spindle and the hub holding member; a transmitting member having a 
first portion for moving the cassette guide member to the 
recording/reproducing position, and a second portion for moving the hub 
holding member to the spindle in such a way that the displacement of the 
second portion is larger than that of the first portion; and a driving 
member for driving the transmitting member to move the transmitting member 
in a manner that the cassette guide member is positioned to the 
recording/reproducing position, when the cassette guide member reaches the 
predetermined position. 
In a preferred embodiment of the invention, the transmitting member may be 
a rotary plate having an end pivotally supported to be rotated by the 
driving member. The distance between the second portion and the end may be 
longer than the distance between the first portion and the end, so that 
the movement of the second portion is amplified in accordance with the 
ratio between the distances. 
The driving member may have an eject lever, a spring member for moving the 
eject lever in the direction of the ejection when the cassette guide 
member reaches the predetermined position and a button for controlling the 
discharge of the cassette. The eject lever can be moved in the direction 
of the ejection of the cassette by the spring member, when the cassette 
guide member reaches the predetermined position in a manner that the 
rotary plate swings toward the recording/reproducing position and can be 
moved in the direction of the insertion of the cassette by the button in a 
manner such that the rotary plate swing from the recording/reproducing 
position. 
Preferably, the magnetic disc unit may further comprise a cassette 
discharge lever for discharging the cassette. The cassette discharge lever 
moves in the insertion direction of the cassette in accordance with the 
insertion of the cassette and is kept in the lock condition in which the 
cassette discharge lever does not discharge the cassette. When the 
cassette reaches the predetermined position, the lock condition is 
released by the eject lever to discharge the cassette when the eject lever 
is moved in the insertion direction of the cassette in response to the 
operation of the button. 
In another preferred embodiment of the invention, the spindle may have a 
spindle shaft which is movable in a direction perpendicular to the main 
surface of the cassette and is biased toward such a direction as to push 
the center hub in a manner that the center hub is clamped between the hub 
holding member and the spindle shaft. 
The magnetic disc unit may further comprise a head seeking mechanism 
including a stepping motor, a lead screw and a gimbal spring for 
connecting the stepping motor to the lead screw in such a way that the 
magnetic head toward a position on the magnetic disc at which the 
information is recorded or reproduced. 
In a second aspect of the present invention, a magnetic disc unit having a 
magnetic head for recording or reproducing information on or from a 
magnetic disc having a center hub and being accommodated in a cassette 
comprises a cassette guide member for carrying the cassette in a manner 
that the cassette guide member moves the cassette to a predetermined 
position in the insertion direction of the cassette in accordance with the 
insertion of the cassette and for guiding the cassette to a 
recording/reproducing position at which information is recorded or 
reproduced on or from the magnetic disc; a spindle for rotating the 
magnetic disc; a hub holding member for pushing the center hub of the 
magnetic disc to the spindle to hold the magnetic disc between the spindle 
and the hub holding member; a transmitting member having a first portion 
for moving the cassette guide member to the recording/reproducing 
position, and a second portion for moving the hub holding member to the 
spindle in such a way that the displacement of the second portion is 
larger than that of the first portion; a driving member for driving the 
transmitting member to move the transmitting member in a manner that the 
cassette guide member is positioned to the recording/reproducing position, 
when the cassette guide member reaches the predetermined position; an 
opening for allowing the insertion of the cassette; and a pair of 
dust-proof doors, each of which is pivotally supported inside of the 
opening in a manner that the dust-proof doors are so biased that an end of 
one of the dust-proof doors which is not pivotally supported is in contact 
with the side of the other dust-proof door to close the opening when the 
cassette is not inserted. 
In a third aspect of the present invention, a magnetic disc unit, which has 
a magnetic head for recording or reproducing information on or from a 
magnetic disc having a center hub and being accommodated in a cassette 
having a notch notched at one end of said cassette from the side of one 
main surface of the cassette to the side of another main surface of the 
cassette for detecting the insertion and one main surface of the cassette, 
comprises a cassette guide member for carrying the cassette in a manner 
that the cassette guide member moves the cassette to a predetermined 
position in the insertion direction of the cassette in accordance with the 
insertion of the cassette and for guiding the cassette to a 
recording/reproducing position at which information is recorded or 
reproduced on or from the magnetic disc; a spindle for rotating the 
magnetic disc; a hub holding member for pushing the center hub of the 
magnetic disc to the spindle to hold the magnetic disc between the spindle 
and the hub holding member; a transmitting member having a first portion 
for moving the cassette guide member to the recording/reproducing 
position, and a second portion for moving the hub holding member to the 
spindle in such a way that the displacement of the second portion is 
larger than that of the first portion; a driving member for driving the 
transmitting member to move the transmitting member in a manner that the 
cassette guide member is positioned to the recording/reproducing position, 
when the cassette guide member reaches the predetermined position; a pair 
of leaf switches disposed at positions corresponding to the notch when the 
cassette is inserted with the one main surface upside and down side, 
respectively; a first means for detecting the insertion of the cassette in 
response to the combination of the operations of the pair of leaf switches 
when the cassette held in the cassette guide member reaches the 
recording/reproducing position; and a second means for detecting that the 
one main surface is positioned upside in response to the combination of 
the operation of the pair of leaf switches when the cassette held in the 
cassette guide member reaches the recording/reproducing position. 
In a fourth aspect of the present invention, a magnetic disc unit for 
recording or reproducing information on or from a magnetic disc having a 
center hub and being accommodated in a cassette comprises, a cassette 
guide member for carrying the cassette in a manner that the cassette guide 
member moves the cassette to a predetermined position in the insertion 
direction of the cassette in accordance with the insertion of the cassette 
and for guiding the cassette to a recording/reproducing position at which 
information is recorded or reproduced on or from the magnetic disc; a 
spindle for rotating the magnetic disc; a hub holding member for pushing 
the center hub of the magnetic disc to the spindle to hold the magnetic 
disc between the spindle and the hub holding member; a transmitting member 
having a first portion for moving the cassette guide member to the 
recording/reproducing position, and a second portion for moving the hub 
holding member to the spindle in such a way that the displacement of the 
second portion is larger than that of the first portion; a driving member 
for driving the transmitting member to move the transmitting member in a 
manner that the cassette guide member is positioned to the 
recording/reproducing position, when the cassette guide member reaches the 
predetermined position; a magnetic head contacting the magnetic disc to 
record or reproduce information on or from the magnetic disc when the 
cassette is positioned at the recording/reproducing position; a first arm 
member having a first end and a second end which are pivotal at a fulcrum 
formed on the cassette guide member; a stopper member for stopping the 
first end of the first arm member at a stopping position; and a second arm 
member for supporting the magnetic head and for moving the magnetic head 
toward the magnetic disc in a manner that the magnetic head contacts the 
magnetic disc in accordance with the movement of the second end of the 
first arm member when the cassette guide member reaches the 
recording/reproducing position. 
Here, it is preferable that the fulcrum is determined at a position between 
the first end and the second end of the first arm member. The first arm 
member swings around the first end stopped by the stopper member in 
accordance with the movement of the fulcrum and the second end moves 
toward the magnetic head when the cassette guide member reaches the 
recording/reproducing position. When the magnetic disc is recorded or 
reproduced information, the stopper member releases the first end of the 
first arm member from the stopping position to rotate the first arm member 
rotates a round the fulcrum and to move the second end of the first arm 
member toward the magnetic disc at the time of recording/reproducing 
information on/from the magnetic disc, in a manner that the displacement 
of the second end of the first arm member is larger than that of the 
fulcrum. 
The above and other objects, effects, features and advantages of the 
present invention will become more apparent from the following description 
of preferred embodiments thereof taken in conjunction with the 
accompanying drawings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
FIG. 1 shows a magnetic disc cassette to be used in a magnetic disc unit in 
accordance with the present invention. The cassette 1 contains a magnetic 
disc 12. A center hub 2 for clamping protrudes at the center of the 
magnetic disc 12 and has a center hole 3 disposed at the center of the hub 
2 for centering. A driving hole 4 into which a pin for rotating the 
magnetic disc 12 is inserted is formed in the vicinity of the center hole 
3. 
The cassette 1 is inserted into a magnetic disc unit in the direction 
indicated by the arrow B. A head window 5 is formed on the front side of 
the cassette 1. A dust-proof or dust-tight shutter 6 is slidably provided 
inside of the head window 5. 
On both sides of the head window 5 are formed are small holes 8 for 
positioning the cassette 1 and write-protecting holes 9. A notch 10 is 
formed so as to detect the top or back surface of the cassette 1. 
The cassette 1 is further provided with an index hole 11 and a slide lever 
7 for opening or closing the shutter 6. When the cassette 1 is inserted 
into the magnetic disc unit, the slide lever 7 engages with a pawl (not 
shown) disposed in the magnetic disc unit, so that the lever 7 slides 
toward a direction indicated by the arrow A whereby the shutter 6 is 
opened. 
The magnetic disc cassette 1 with the above-described construction can be 
inserted into a magnetic disc unit in accordance with the present 
invention as shown in FIG. 2 through FIG. 8. 
The magnetic disc unit generally designated by the reference numeral 15 has 
a couple of side panels 16 and 17 and a front panel 18 extended between 
the side panels 16 and 17. The front panel 18 is formed with a cassette 
insertion opening 18a through which the cassette 1 is inserted. 
As shown in FIGS. 2, 6A, 6B, 9 and 10 and particularly as best shown, on 
enlarged scale, in FIGS. 9 and 10, upper and lower dust-proof doors 19 and 
20 are pivotally supported by shafts 21 and 22, respectively, which in 
turn are mounted to the inner surface of the front panel 18. The upper and 
lower dust-proof doors 19 and 20 are normally biased under the forces of 
coiled springs 23 (See FIG. 2) mounted to the shafts 21 and 22 in a manner 
that the upper and lower dust-proof doors 19 and 20 normally close the 
cassette insertion opening 18a. 
If only one dust-proof door 19a is provided as shown in FIG. 11A, the space 
with a depth R corresponding to the width of the dust-proof door 19a must 
be provided so as to permit the rotation of the dust-proof door 19a around 
its shaft 21a. On the other hand, in order to reduce the space, the upper 
and lower dust-proof doors 19b and 20b may be provided as shown in FIG. 
11B. In this case, the space with a depth r (where r.perspectiveto.R/2) 
must be provided so as to allow the rotation of the upper and lower 
dust-proof doors 19b and 20b around the shafts 21b and 22b. Therefore, the 
required depth becomes shorter and accordingly the magnetic disc unit can 
be made more compact in size. However, if the distance l between the upper 
and lower shafts 21b and 22b is not equal to the sum of the the heights of 
the upper and lower dust-proof doors 19b and 20b, it may happen that the 
leading edges of the dust-proof doors 19b and 20b collide with each other 
or are spaced apart from each other, so that the dust-proof doors 19b and 
20b do not function to prevent dust from invading through the opening 18a. 
This inconvenience is caused often by dimensional variations of parts, 
that is, the upper and lower dust-proof doors 19b and 20b. 
Referring back to FIGS. 9 and 10, the lower edge of the upper dust-proof 
door 19 abuts against the front surface of the lower dust-proof door 20 in 
a manner that, as best shown in FIG. 10, the upper edge portion of the 
lower dust-proof door 20 is bent inwardly at an angle .alpha., to form a 
bent portion 20a, against which the lower edge of the upper dust-proof 
door 19 abuts, so that when the cassette 1 is not inserted into the 
magnetic disc unit 15, the cassette insertion opening 18a is tightly 
closed in a dust-proof manner. 
In order that the lower edge of the upper dust-proof door 19 may securely 
abut against the bent portion 20a of the lower dust-proof door 20, it is 
preferable that the radii of rotation l.sub.1 and l.sub.2 of the lower and 
upper dust-proof doors 20 and 19 are substantially equal to each other. 
A flat inverted-U shaped cassette guide 24 is disposed on the rear side of 
the front panel 18 in the magnetic disc unit 15 in such a way that the 
front end of the cassette guide 24 is opposite to the cassette insertion 
opening 18a of the front panel 18. When the cassette 1 is inserted into 
the cassette insertion opening 18a, the cassette 1 is first engaged with 
the end of the cassette guide 24 and then is guided straight by the 
cassette guide 24 to be inserted into the magnetic disc unit 15. In this 
case, a pawl or projection (not shown) engages with the slide lever 7 of 
the cassette 1 (FIG. 1). Accordingly, as the cassette 1 is inserted 
deeper, the shutter 6 is opened gradually and when the leading end of the 
cassette 1 reaches the bottom of the cassette guide 24, the shutter 6 is 
fully opened, so that heads 79 and 80 can engage with the magnetic disc 
12. 
As shown in FIG. 2, a cassette discharge lever 25 is disposed above the 
cassette guide 24. The lever 25 is provided with elongated slots 25a and 
25b into which guide pins 26 and 27 are slidably fitted. A spring 28 is 
extended between a projection 24a formed by cutting and then folding a 
portion of the cassette guide 24 and an end protrusion 25c of the cassette 
discharge lever 25, so that the discharge lever 25 is normally biased 
toward the front panel 18. 
The leading edge of the discharge lever 25 is folded downwardly to form a 
projection 25d which is fitted downwardly into an opening 24b formed in 
the cassette guide 24 so as to be adapted to engage with the cassette 1 
when the cassette 1 is inserted into the cassette guide 24. 
A projection 25e is extended from one end of the discharge lever 25 toward 
the side plate 16 and is adapted to engage with a locking arm 29 which is 
rotatably provided around a shaft 30 as shown in FIG. 5. In FIG. 5, a 
spring 31 is extended between a projection 16a extended from an end 
portion of the side panel 16 and the locking arm 29, so that the locking 
arm 29 is normally biased in the counterclockwise direction. The locking 
arm 29 has an upwardly extended arm 32 and a forwardly extended arm 33 as 
shown in FIG. 5. The arm 32 is positioned to be engaged with the 
projection 25e of the discharge lever 25. 
An eject lever 34 is disposed outside of the side panel 16 and is provided 
with horizontally elongated slots 34a and 34b which are spaced apart from 
each other in the longitudinal direction of the eject lever 34. Pins 35 
extended from the side panel 16 are slidably fitted into the elongated 
slots 34a and 34b. 
An elongated opening 34c is formed substantially at the center of the 
ejected lever 34 between the elongated slots 34a and 34b. A hole 36 is 
formed in the vicinity of the elongated opening 34c on the side of the 
locking arm 29. The side panel 16 is provided with a hole 37 at a remote 
position from the hole 36, so that a spring 38 is extended between these 
holes 36 and 37 in such a way that the eject lever 34 is normally biased 
toward the front panel 18. 
A pin 39 is protruded from the outer surface of an end portion of the eject 
lever 34 on the side of the locking arm 29. The pin 39 is engaged with a 
hook 33a formed at the leading edge of the forwardly extended arm 33 of 
the locking arm 29. 
A button 98 for controlling the discharge of the cassette 1 is attached to 
the leading end of the bent portion 34e extended from the eject lever 34 
toward the front panel 18, as shown in FIGS. 2 and 8. 
A shaft 40 is extended between the side panels 16 and 17 as shown in FIG. 2 
in parallel with and inside the front panel 18. The shaft 40 rotatably 
supports one end of a rotary plate 41. 
A pin 42 is extended inwardly from the free end of the rotary plate 41 and 
is rotatably supported by a projection 43 extended from both sides of the 
cassette guide 24 so that the rotary plate 41 is co-operatively coupled to 
the cassette guide 24. 
A pin 44 is protruded from the rotary plate 41 toward the side panel 16 and 
is slidably fitted into a Z-shaped cam hole 45 formed in the upper edge 
portion of the eject lever 34. 
As shown in FIG. 2 and in more detail in FIG. 14, a locking lever 46 is 
pivoted with a pin 47 to the cassette guide 24 in the vicinity of the 
cassette discharge lever 25 and on the side of the side panel 16. The 
locking lever 46 has a projection 46a which is extended outwardly and is 
positioned to be engaged with the side edge 34d of the eject lever 34 on 
the side of the locking arm 21. 
A pin 48 is protruded from the locking lever 46 at the side edge thereof on 
the side opposite to the pin 47. A V-shaped spring 49 is extended between 
the pin 48 and the pins 26 and 27 as shown in FIGS. 2 and 14 so that the 
locking lever 46 is normally biased in the clockwise direction about the 
pin 47 in FIG. 2. 
As shown in FIGS. 2 and 14, the locking lever 46 has a projection 46b which 
is protruded from the end portion of the locking lever 46 on the side of 
the pin 48 and on the side of the cassette discharge lever 25. The 
projection 46b is positioned to be engaged with the depending projection 
25f of the cassette discharge lever 25 on the side of the front panel 18. 
In FIG. 2, one end of a leaf spring 50 is securely fixed with pins 51 to 
the upper surface of the rotary plate 41 at the center portion thereof. 
As shown in FIGS. 6A and 6B, a hub holder 53 is securely fixed through a 
bearing 52 to the undersurface of the leaf spring 50 on the side of its 
free end. 
In FIGS. 6A and 6B, a spindle 54 is disposed in opposed relationship with 
the hub holder 53. As best shown in FIG. 12, the spindle 54 is rotatably 
mounted to the base plate 54a of the magnetic disc unit 15. A disc 55 is 
fixedly attached to the upper surface of the spindle 54. At the center of 
the disc 55, there is formed an opening 55a through which a spindle shaft 
56 is slidably fitted into the spindle 54. The spindle shaft 56 is 
normally biased upwardly by the force of a spring 57 which is accommodated 
between the inside of the spindle shaft 56 and the opening 55a. A driving 
pin 58 is engaged with the disc 55 in a manner that the pin 58 is 
vertically movable and is adapted to engage with the driving hole 4 of the 
hub 2 of the magnetic disc 12. The driving pin 58 is normally biased 
upwardly by the force of a leaf spring 59. 
A pulley 60 is securely fixed to the lower end of the spindle 54. As shown 
in FIG. 8, an endless belt 63 is wrapped around the pulley 60 and a pulley 
62 carried by the output shaft of a motor 61, so that the rotation of the 
motor 61 is transmitted to the pulley 60 and hence to the spindle 54. 
Referring back to FIG. 2, projections 64 are protruded longitudinally of 
the cassette guide 24 on the upper surface thereof on the opposite side of 
the cassette discharge lever 25 in a manner such that the projections 64 
are opposed to each other. A shaft 65 is supported between the projections 
64 to rotatably carry the center portion of a head load arm 66. 
As best shown in FIG. 7, the outer end of the head load arm 66 has a 
projection 66a which protrudes outwardly from the side panel 17. A push 
arm or lever 68 is pivotally supported by a pin 67 on the outer side of 
the side panel 17 below the projection 66a. The edge of the horizontal 
portion of the rotary arm 68 is in contact with the undersurface of the 
projection 66a, while the vertical portion of the rotary arm 68 is pivoted 
with a pin 69 to one end of a load arm or lever 70. 
The other end of the load arm or lever 70 is connected to a rod 71a of a 
solenoid 71 fixed to a stationary member of the magnetic disc unit 15 on 
the side opposite to the front panel 18. 
Still referring to FIG. 7, a spring 72 is extended between the projection 
66a of the head load arm 66 and the pin 67 and between the pin 67 and a 
pin 73 which is protruded from the side panel 17, so that the head load 
arm 66 is normally biased in the clockwise direction in FIG. 4. 
As shown in FIGS. 6A and 6B, a head arm 74 is disposed on the upper side of 
the cassette guide 24 in opposite relationship with the leaf spring 50. 
The base of the head arm 74 is securely jointed with screws 77 to a block 
76 which in turn is rotatably supported through a pin 75 to a seek arm to 
be described below. The block 76 is normally so biased as to rotate about 
the pin 75 in the counterclockwise direction in FIG. 6 by the force of a 
coiled spring 78. A magnetic head 79 is securely attached to the lower 
surface of the head arm 74 at the leading edge thereof. 
A positioning pin 97 is protruded from the upper surface of the base plate 
54a so as to be engaged with the positioning hole 8 of the cassette 1. 
The head arm 74 may be made of, for instance, a leaf spring and has a 
projection 74a, as shown in FIG. 2, which is protruded from the end 
portion of the head arm 74 on the side of the head load arm 66 toward the 
head load arm 66. The inner end of the head load arm 66 engages with the 
undersurface of the projection 74a. The head arm 74 is normally biased 
upwardly by the inner end of the head load arm 66 which is pushed upwardly 
by the force of the spring 72. The cassette guide 24 has an opening 24c 
which corresponds to the head 79. A stationary head 80 is disposed on a 
carriage to be described below in opposed relationship with the movable 
head 79. 
As shown in FIG. 2 and in more detail in FIGS. 15 and 16, a stepping motor 
81 is mounted to a mounting plate 96 and dowels 82a and 82b of a joint 82, 
shown in FIGS. 15 and 16, which is securely fixed to the output shaft 81a 
of the stepping motor 81 are fitted into holes 83a and 83b, respectively, 
of a gimbal spring 83 shown in FIGS. 15 and 17. One end of the lead screw 
84 is connected to the center hole 83c of the gimbal spring 83 and the 
other end of the lead screw 84 is rotatably supported by a bearing 85, as 
shown in FIGS. 15 and 16. 
The lead screw 84 and the output shaft 81a of the stepping motor 81 are 
interconnected through the gimbal spring 83 as shown in FIG. 17, so that 
the lead screw 84 is pushed toward the stepping motor 81 by a displacement 
6 as shown in FIG. 16. Therefore, a backlash in the thrust direction of 
the lead screw 84 with respect to the bearing 85 and the stepping motor 81 
can be eliminated. 
As shown in FIG. 2, one end of a seek arm 86 is threadably engaged with the 
lead screw 84 so that a lead bar 87 is shifted forwardly or backwardly 
through the seek arm 86. 
The seek arm 86 is fixed to the outside of a carriage 88. A portion of the 
carriage 88 which is opposite to the seek arm 86 is guided by a guide bar 
89 which is disposed in parallel with the lead screw 84. The pin 75 which 
supports the block 76 is supported between a pair of projections 88a 
protruded from the carriage 88. 
As shown in FIG. 8, a pair of leaf switches 90 are disposed on the base 
plate 54a in order to detect whether the cassette is inserted into the 
magnetic disc unit 15 or not and also to detect the upper or lower surface 
of the inserted cassette. These switches 90 are disposed to a position 
which corresponds to the notch 10 for detecting the upper or lower surface 
of the magnetic disc cassette 1 and to a position which corresponds to a 
position on the cassette 1 which is symmetrical to the notch 10 with 
respect to the head window 5. 
FIG. 18 is a perspective view showing an embodiment of a detection 
mechanism. The leaf switch 90 has a movable plate 91 and a stationary 
plate 92. When no external force is exerted to the movable plate 91, the 
movable and stationary plates 91 and 92 are maintained substantially in 
parallel with each other. The base plate 54a has holes 54c. One of the 
holes 54c is located at the position corresponding to the notch 10 of the 
magnetic disc cassette 1 when the cassette 1 is inserted into the magnetic 
disc unit, while the other hole 54c is located at a position which is 
symmetrical to the notch 10 with respect to the head window 5. A pin 93 is 
inserted into the hole 54c. The pin 93 has a head 93a which is supported 
by the movable plate 91 of the leaf switch 90. The head 93a is provided in 
order to prevent the pin 93 from being slipped off. 
FIG. 19A shows the open condition of the leaf switch 90, while FIG. 19B 
shows the close condition of the leaf switch 90. When the magnetic disc 
cassette 1 is not inserted into the magnetic disc unit 15, the upper end 
93b of the pin 93 is out of engagement with the cassette 1, so that the 
movable plate 91 is spaced apart from the stationary plate 92. 
When the magnetic disc cassette 15 is inserted into the magnetic disc unit 
15, the top of the pin 93 which is located at a position which does not 
correspond to the notch 10 of the magnetic disc cassette 1 is brought into 
contact with the magnetic disc cassette 1, so that the pin 93 is pushed 
downward in accordance with the downward movement of the cassette 1. Then, 
as shown in FIG. 19B, the movable plate 91 is deflected to be brought into 
contact with the stationary plate 92 when the loading of the magnetic disc 
cassette 1 is completed. On the other hand, the pin 93 which is located at 
the position corresponding to the notch 10 of the magnetic disc cassette 1 
is out of engagement with the cassette 1, so that the movable plate 91 is 
not deflected and accordingly is out of engagement with the stationary 
plate 92. 
As described above, whether the magnetic disc cassette 1 is inserted into 
the magnetic disc unit 15 or not and whether the upper surface of the 
cassette 1 is directed upward or downward can be detected by a pair of 
detection means, one of which is located at the position corresponding to 
the notch 10 of the magnetic disc cassette 1 and the other of which is 
located at the position which is symmetrical to the notch 10 with respect 
to the head window 5. 
In contrast, a conventional detection means uses a photocoupler as shown in 
FIG. 20A, in which a light source or light emitting device 95a and a light 
receiving device or phototransistor 95b are required to be aligned with 
the notch 10 on both sides of the cassette 1. As a result, the detection 
means is complicated. Moreover, electrical power must always supplied to 
the light source 95a, so that power consumption is increased. 
FIG. 20B shows another conventional detection means using a microswitch 
95c. Here, a pin 95d which is in contact with the microswitch 95c is used 
to detect whether or not the notch 10 exists and thus it is sufficient 
that the pin 95d corresponds to the notch 10 only on one side of the 
cassette 1, so that the structure of the detection means is simple. In 
addition, no light source is needed, so that only a small amount of power 
consumption is sufficient. 
However, the microswitch 95c has a relatively large height m so that the 
space for mounting the microswitch 95c is increased. On the other hand, 
according to the present invention, the leaf switch 90 is used whose 
height is smaller than that of the microswitch 95c and accordingly the 
magnetic disc unit in accordance with the present invention can be made 
thin. 
Next, the modes of operation of the magnetic disc unit according to the 
present invention with the above-describe construction will be described 
in detail. 
Before the magnetic disc cassette 1 is inserted into the magnetic disc unit 
15, the lower edge of the upper dust-proof door 19 abuts against the bent 
portion 20a of the lower dust-proof door 20 under the force of the coiled 
spring 23, as shown in FIG. 9, so that there exists no space between the 
upper and lower dust-proof doors 19 and 20. 
When the magnetic disc cassette 1 is inserted, the upper and lower 
dust-proof doors 19 and 20 are forced to swing about their shafts 21 and 
22 and move away from each other. Since the upper and lower dust-proof 
doors 19 and 20 overlap each other, their widths are longer according to 
this overlap. Therefore, as shown in FIG. 10, the distance l.sub.3 between 
the upper shaft 21 and the upper surface of the magnetic disc cassette 1 
inserted into the cassette insertion opening 18a is longer. 
This means that the moment arm is long so that the upper and lower 
dust-proof doors 19 and 20 can smoothly be opened and thus the magnetic 
disc cassette 1 can easily be inserted. 
The magnetic disc cassette 1 thus inserted into the opening 18a is then 
guided by the cassette guide 24 and the pawl or projection (not shown) 
engages with the slide lever 7 of the cassette 1. As a consequence, as the 
cassette 1 advances toward the inside of the magnetic disc unit 15, the 
shutter 6 is opened gradually. 
Then, the magnetic disc cassette 1 engages with the bent portion 25d at the 
inner end of the cassette discharge lever 25 to move the cassette 
discharge lever 25 against the force of the coiled spring 28. 
The projection 25e of the cassette discharge lever 25 engages with the 
upwardly extended arm 32 of the locking arm 29, so that the locking arm 29 
is rotated in the clockwise direction about the shaft 30 in FIG. 5. 
Then, as the locking arm 29 rotates, the hook 33a of the forwardly extended 
arm 33 of the locking arm 29 is disengaged from the pin 39, so that the 
eject lever 34 is guided by the pin 35 toward the front panel 18 under the 
force of the spring 38. 
As the eject lever 34 is displaced, the pin 44 is forced to move downwardly 
along the V-shaped cam slot 45 so that the rotary plate 41 to which the 
pin 44 is attached is rotated about the shaft 40 in the clockwise 
direction in FIG. 6A. As a consequence, the cassette guide 24 is lowered 
together with the cassette 1 as shown in FIG. 6B. 
In this case, the downward displacement of the cassette guide 24 is 
amplified in accordance with the ratio between the distance l.sub.5 
between the shaft 40 and the pin 44 and the distance l.sub.6 between the 
shaft 40 and the pin 42 as shown in FIG. 13. 
In FIG. 6A, as the cassette guide 24 is lowered, the leaf spring 50 and the 
rotary plate 41 are lowered together, so that the hub holder 53 is lowered 
and consequently the hub 2 of the magnetic disc 12 in the cassette 1 is 
clamped between the hub holder 53 and the spindle 54 as shown in FIG. 6B. 
The lower end of the hub holder 53 is fitted into the center hole 3 and 
the shaft 56 of the spindle 54 is also fitted into the center hole 3 of 
the hub 2 from the lower side of the hub 2, so that the magnetic disc 12 
is centered with respect to the spindle 54. If it happens that the driving 
hole 4 and the driving pin 58 are aligned with each other, the driving pin 
58 is immediately fitted into the driving hole 4 as shown in FIG. 6B. In 
general, however, the driving pin 58 is in contact with the lower surface 
of the hub 2, thereby causing elastic deflection of the leaf spring 59. 
That is, the leaf spring 59 is deflected downwardly. 
In this case, the downward displacement of the hub holder 53 with respect 
to the downward displacement of the rotary plate 41 is amplified by a 
factor equal to the ratio between the distance l.sub.5 and the distance 
l.sub.7 between the shaft 40 and the hub holder 53, as understood from 
FIG. 13. 
When the magnetic disc cassette 1 reaches a loading reference position in 
this manner, the positioning pin 97 extended from the base plate 54a is 
fitted into the positioning hole 8 of the cassette 1. 
When the cassette discharge lever 25 is advanced from the position shown by 
a dash-and-dot line to the position shown by a solid line in FIG. 14, the 
locking lever 46 is rotated in the clockwise direction in FIGS. 2 or 14. 
Then, the projection 46b of the locking lever 46 is brought into contact 
with the edge 25f of the cassette discharge lever 25. As a result, the 
cassette discharge lever 25 is prevented from returning backwardly and 
thus is locked. 
Simultaneously with the downward displacement of the cassette guide 24, the 
head load arm 66 is also lowered and consequently the head arm 74 is also 
lowered to such an extent that the head 79 does not contact the magnetic 
disc 12. That is, the movable head 79 is spaced apart from the magnetic 
disc 12 by a small distance and the magnetic disc 12 is interposed between 
the movable and stationary heads 79 and 80. 
In this way, the magnetic disc cassette 1 is loaded in the magnetic disc 
unit 15. 
When the magnetic disc cassette 1 is lowered in the manner described above 
to the surface of the loading position reference, the leaf switches 90 
detect that the magnetic disc cassette 1 has been loaded in position, as 
shown in FIG. 19B. That is, one of the two leaf switches 90 is closed. At 
the same time, it is detected whether the upper surface of the magnetic 
disc cassette 1 is directed downwardly or upwardly. Once the loading of 
the magnetic disc cassette 1 has been confirmed, the motor 61 is energized 
so that the pulley 60 is rotated via the endless belt 63 and consequently 
the spindle 54 starts rotating. While the spindle 54 makes one rotation, 
the driving pin 58 is fitted into the driving hole 4 of the hub 2, as 
shown in FIG. 6B, so that the magnetic disc 12 starts rotating. 
After the loading of the magnetic disc cassette 1 has been detected in 
response to the output signals from the leaf switches 90, the solenoid 71 
is energized to retract the rod 71a and consequently the load arm 70 is 
pulled toward the solenoid 71, as shown in FIGS. 7 and 8. As a result, as 
shown in FIG. 7, the push arm 68 is rotated about the pin 67 in the 
clockwise direction, so that the projection 66a of the head load arm 66 is 
pushed upwardly against the spring 72. As a consequence, the head load arm 
66 is rotated in the clockwise direction about the pin 65 in FIG. 4, so 
that its inner end 66b is lowered. As a result, the head arm 74 which has 
been locked by the projection 74a of the head arm 74 is now released to be 
freely movable downwardly. The force of the coiled spring 78 lowers the 
magnetic head 79 together with the head arm 74. Therefore, the magnetic 
head 79 which has been spaced apart from the magnetic disc 12 by a small 
distance is caused to engage with the magnetic disc 12. 
Since the head load arm 66 is pivotally supported at its center by the pin 
65 the amount of the displacement of the magnetic head 79 can be made 
larger than that of the cassette guide 24. Thus, as shown in FIG. 6B, it 
is ensured that the magnetic head 79 is in contact with the magnetic disc 
12. 
After the magnetic disc cassette 1 has been loaded in the manner described 
above, the stepping motor 81 is energized to rotate, so that the lead 
screw 84 is rotated and consequently the carriage 88 starts to be 
displaced through the seek arm 86, whereby information is written or read 
out. 
In order to discharge the magnetic disc cassette 1 from the magnetic disc 
unit 15, the button 98 which is attached to the leading end of the bent 
portion 34e extended from the eject lever 34 toward the front panel 18, as 
shown in FIG. 8. Then, as shown in FIG. 5, the eject lever 34 is caused to 
advance against the force of the coiled spring 38 and then the projection 
25e of the cassette discharge lever 25 pushes the arm 32. The eject lever 
34 is displaced to the underside of the arm 33 of the locking arm 29 which 
is rotated in the clockwise direction. As the arm 33 is lowered, the eject 
lever 34 is again locked by the hook 33a. 
As the eject lever 34 advances, the projection 46a of the locking lever 46 
is pushed by the eject lever 34, so that the locking lever 46 is rotated 
about the pin 47 in the counterclockwise direction in FIGS. 2 or 14, so 
that the projection 46b is disengaged from the edge 25f of the cassette 
discharge lever 25. 
When the eject lever 34 advances, the pin 44 which has been located at the 
lowermost position of the cam slot 45 is displaced to the uppermost 
position thereof, as shown in FIG. 5, so that the rotary plate 41 returns 
to its horizontal position. 
When the rotary plate 41 returns to its horizontal position, the cassette 
guide 24 which is connected via the pin 42 to the rotary plate 41 is also 
lifted upwardly, so that the magnetic disc cassette 1 returns to the same 
level as the cassette 1 was positioned at at the time the cassette 1 was 
inserted into the magnetic disc unit 15 as shown in FIG. 6A. 
Under these conditions, the edge 25f of the cassette discharge lever 25 is 
disengaged from the projection 46b of the locking lever 46 as described 
before, so that the cassette discharge lever 25 is suddenly attracted 
toward the front panel 18 under the force of the coiled spring 28. As a 
result, the bent portion 25d discharges the magnetic disc cassette 1 from 
the magnetic disc unit 15 through the cassette insertion opening 18a. 
Thereafter, all the movable members are reversed in operation, so that the 
magnetic disc unit 15 is now ready to receive another magnetic disc 
cassette 1. 
After the magnetic disc cassette 1 has been discharged from the magnetic 
disc unit 15, the upper and lower dust-proof doors 19 and 20 are closed 
under the force of the coiled spring 23, as shown in FIG. 9. Thus, the 
cassette insertion opening 18a is completely closed in a dust tight 
manner. 
As described above, according to the present invention, the center hub of 
the magnetic disc is clamped so that unlike a conventional magnetic disc 
unit, separate buttons and levers for loading and clamping are not 
required. Thus, the present invention can provide a magnetic disc unit 
which is compact in size and light in weight and which can easily clamp 
the center hub of the magnetic disc. 
The upper and lower dust-proof doors are swingably disposed at the cassette 
insertion opening of a magnetic disc unit and are biased so as to overlap 
each other. Therefore, when they are closed, no dust is permitted to 
penetrate into the magnetic disc unit. Thus, the magnetic disc unit is 
compact in size and light in weight and can be closed in a completely dust 
tight manner. 
The head load arm is associated with the cassette guide, so that the 
displacement of the movable magnetic head can be amplified. As a result, a 
magnetic disc unit according to the present invention can be made thin. 
While in a conventional magnetic disc unit, photoswitches or microswitches 
are used to detect the loading of the magnetic disc cassette, according to 
the present invention, leaf switches are employed so that the magnetic 
disc unit can be made even thinner.