Abstract:
An optical disk drive unit comprising: a sealing enclosure which encloses from exterior the disk cartridge and an access mechanism for the recording medium in the disk cartridge; an input device for inputting an eject command signal; a pin for moving and arranging a cartridge eject device to a state for starting its function; a cam which is disengaged from the pin when the cartridge is unloaded and which is contacted from the pin to start the ejecting function when the cartridge is loaded so that by rotating the cam, the ejecting function can be conducted; a cam drive disposed outside of the enclosure; a linkage for connecting a shaft of the cam drive to the cam through a hole formed in the enclosure; and a controller for controlling the cam in such a way that upon receipt of the eject command signal from the input device, the cam drive is driven to rotate the cam until the cartridge is ejected, wherein through a hole  15  of the chassis  1  is inserted a shaft  81  of the cam  80,  and a worm wheel  79  is connected to the shaft  81  through an engagement member  82,  the worm wheel  79  engaging with a worm  77  installed on a rotational shaft of an eject motor  76.

Description:
This is a continuation of application Ser. No.  08 / 514 , 225  filed Aug.  11 ,  1995 , now abandoned, which is a re- issue application of Ser. No.  07 / 890 , 539  filed May  28 ,  1992 , now U.S. Pat. No.  5 , 301 , 179 .    
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an optical disk drive unit having a mechanism for loading a disk cartridge which houses a disk-shaped recording medium on the device at a predetermined position thereof and ejecting the loaded disk cartridge from the device as well. 
     2. Description of the Related Art 
     An optical disk device uses an optical disk or a magneto-optic disk as a recording medium. The device uses the optical disk or magneto-optic disk (which is simply referred to as optical disk hereinafter) in a state wherein the optical disk is housed in a disk cartridge so that the optical disk can be conveniently exchanged. 
     Such a medium interchangeable optical disk device comprises a loading mechanism and an ejection mechanism for exchanging the disk cartridge, which forms many opening portions through which the inside of the device communicates with the outside of the device on the housing or chassis of the device so that the outer air is freely introduced into the device. 
     Accordingly, dusts or other particles included in the air stick to the optical parts assembled in the pickup device, which disturbs the wave-form of the optical signal, which lowers the reliability of the signal and causes the data error. 
     In order to prevent the outer air from entering into the optical disk device, it may be ideal to completely enclose the optical disk device. 
     However, in accordance with the ejection mechanism of the related art, to set the ejection mechanism as the initial state thereof, before the operation of the optical disk device, an eject pin has to be moved to a predetermined initial position by manually pressing an eject button, for instance. For this purpose, the chassis of the optical disk drive unit of the related art has a longitudinal opening formed therein corresponding to the moving range of the eject pin, which involves in the problem of entrance of outer air into the device through the opening. 
     Also, the movement of the eject pin along the longitudinal opening causes to generate dusts which are introduced into the device and attached to parts installed in the device. 
     SUMMARY OF THE INVENTION 
     The present invention was made considering the above mentioned problems of the related art. It is therefore an object of the present invention to provide an optical disk drive unit which is able to prevent the entrance of dusts into the optical disk device through the opening around the eject pin and avoid generation of dusts due to the movement of the eject pin. 
     The above mentioned object of the present invention can be achieved by 
     an optical disk drive unit for loading a disk cartridge which houses a disk-shaped recording medium at a predetermined position in the unit and ejecting the loaded disk cartridge from the unit as well, the optical disk drive unit comprising: 
     a sealing enclosure which sealingly encloses the recording medium and an access mechanism for writing/reading data on and from the recording medium from exterior in a state where the disk cartridge is installed in the unit; 
     an input device for inputting a command signal to eject the loaded disk cartridge from the unit; 
     an eject device for ejecting the disk cartridge from the unit; 
     a pin for moving and arranging the eject device to a state for starting its ejecting function; 
     a cam member which is arranged in such a way that the cam member is in a state of being disengaged from the pin when the disk cartridge is being unloaded from the unit and that the cam member is in a state of being contacted from the pin to start the ejecting function by the eject device when the disk cartridge is being loaded in the unit so that by rotating the cam member, the ejecting function can be conducted; 
     a cam drive device for driving the cam member to rotate which drive device is disposed outside of the sealing enclosure; 
     a linkage device for connecting a rotational shaft of the cam drive device to the cam member which linkage device is disposed penetrating through a hole formed in the sealing enclosure; and 
     a control device for controlling the cam member in such a way that upon receipt of the command signal to eject the disk cartridge transmitted from the input device, the cam drive device is driven to rotate the cam member until the disk cartridge is ejected. 
     An advantage of the present invention is that, due to the arrangement wherein the drive unit for driving the eject pin is disposed in the outside of the enclosure body, it becomes possible to prevent dusts from entering into the enclosure which dusts are generated from the drive mechanism. 
     Also, it is another advantage of the present invention that, due to the arrangement wherein the opening around the linkage member which links the cam member and the drive unit together is closed, it becomes possible to avoid entrance of dusts through the opening. 
     Further objects and advantages of the present invention will be apparent from the following description of the preferred embodiments of the invention as illustrated in the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1a is an exploded perspective view of the magneto-optic disk drive unit in accordance with an embodiment of the present invention; 
     FIG. 1b is a sectional view of the cam which constitutes a disk loading mechanism of the present invention; 
     FIG. 2a is a perspective view of an example of the disk cartridge in accordance with the present invention; 
     FIG. 2b is a partial perspective view of the disk cartridge of FIG. 2a; 
     FIG. 3 is a plan view of the latch mechanism for explaining the function thereof; 
     FIG. 4 is a side view of the carrier and tray combined together; 
     FIG. 5a is a partial exploded perspective view of an example of the eject mechanism in accordance with the present invention; 
     FIG. 5b is a partial sectional view of the eject mechanism of FIG. 5a; 
     FIGS. 6a to  6 d are explanatory views for explaining the function of the cam member in accordance with the present invention; 
     FIG. 7 is an exploded perspective view of an example of the enclosure hosing body structure in accordance with the present invention; 
     FIG. 8 is a schematic partial sectional view representing a state where the chassis and the chassis cover are combined together; 
     FIG. 9 is a perspective view of an example of the access mechanism housed in the chassis in accordance with the present invention; 
     FIG. 10 is a sectional view of the optical disk drive unit in a state wherein the disk cartridge is sealingly enclosed therein; 
     FIG. 11 is a block diagram of the control system applied to the magneto-optic disk device in accordance with the present invention; 
     FIG. 12 is a flow chart of an example of the process of the ejecting function in accordance with the present invention; 
     FIG. 13a is a partial sectional view of another example of the sealing structure for the eject mechanism in accordance with the present invention; 
     FIG. 13b is a partial sectional view of still another example of the sealing structure for the eject mechanism in accordance with the present invention; and 
     FIG. 13c is a partial sectional view of a further example of the sealing structure for the eject mechanism in accordance with the present invention. 
     FIG. 14a is a partially expanded perspective view of another example of the eject mechanism in accordance with the present invention; 
     FIG. 14b is a schematic view showing a movement of the worm wheel  79  seen from the bottom thereof, in the eject mechanism of FIG. 14a; 
     FIG. 14c is another plane view of the male engagement member  82  used in the eject mechanism of FIG. 14a; 
     FIG. 15 is an explanatory view of the cam member used in the optical disk drive unit in accordance with the present invention, in which an increasing ratio of a radius to a rotary angle of the cam member is not constant; 
     FIG. 16a is a graph showing a change of the radius value of the cam member  80 , with respect to the rotary angle thereof; 
     FIG. 16b is a graph showing a change of the current value flowing in a motor, with respect to the rotary angle of the cam member  80 ; 
     FIG. 16c is a graph showing a change of the radius value of the cam member  80  of FIG. 15, with respect to the rotary angle thereof; and 
     FIG. 16d is a graph showing a change of the current value flowing in the motor, with respect to the rotary angle of the cam member  80  of FIG.  15 . 
     FIG. 16e is a view of an example for showing a change of the load of the simplified loading system with respect to a loading stroke. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Embodiments of the present invention are described hereinafter in detail with reference to the drawings. 
     FIG. 1a illustrates the magneto-optic disk drive unit in accordance with an embodiment of the present invention. 
     In the drawing, the magneto-optic disk drive unit comprises a chassis  1  on which is mounted a disk loading mechanism constituted from a tray  2  for housing a disk cartridge (described later), a carrier  3  which reciprocates in the directions of insertion and ejection for the disk cartridge, and cams  4 ,  5 ,  6  and  7  which links the tray  2  and the carrier  3  with each other so that the tray  2  is moved back and forth in the directions of insertion and ejection of the disk cartridge along with the movement of the carrier  3 . 
     In the chassis  1 , there are disposed leveling pins  8 ,  9 ,  10  and  11  for standardizing the height of the disk cartridge which is to be installed in the disk drive unit. The disk cartridge is inserted into the drive unit from the front side of the unit in the drawing. Two of the leveling pins  9  and  11  are disposed back and forth on the right side of the chassis  1  with respect to the cartridge insertion direction. The carrier  3  has longitudinal holes  12  and  13  formed therein along the insertion direction of the disk cartridge for guiding the pins  9  and  11  arranged on the chassis  1 . 
     At a portion in front of the front side hole  12  of the carrier  3  is arranged an eject pin  14  disposed underside of the carrier  3  protruding downward therefrom. The eject pin  14  is arranged to push the carrier  3  in the operation of ejecting the disk cartridge. The chassis  1  has a hole  15  formed therein through which an eject mechanism (described later) for driving the eject pin  14  is arranged to pass. 
     Pins  16  and  17  are disposed behind the leveling pins  8  and  9 , respectively. The carrier  3  has longitudinal holes  18  and  19  formed therein through which the pins  16  and  17  of the chassis  1  are guided and escaped, respectively, so that the pins  16  and  17  protrude through the holes  18  and  19 , respectively, toward the upper side of the carrier  3 . Hooks  20  and  21  are arranged in the rear side portion of the carrier  3 . Springs  22  and  23  which bias the carrier  3  to move toward the cartridge ejecting direction are disposed spanning between each of the hooks  20 ,  21  and each of the pins  16 ,  17  protruding through the holes  18 ,  19 , respectively. 
     When the disk cartridge is not installed in the carrier  3 , the bias force from the springs  22  and  23  is made unenforceable on the carrier  3  due to the arrangement of a latch mechanism  24  which is disposed behind the hole  13  of the carrier  3  and prevents the carrier from moving. 
     The latch mechanism  24  comprises an axle  24 a arranged on the chassis  1 , a latch plate  24 b rotatably attached to the axle  24 a, a latch pin  24 c mounted on the latch plate  24 b at a position where the pin  24 c is able to engage with a lever  25  attached to the tray  2 , a latch roller  24 e which is arranged to engage with a recessed portion  24 d formed in the carrier  3 , and a latch spring  24 f made from a coil spring biasing the latch plate  24 b in the direction where the pin  24 c comes in contact with the lever  25 . An end of the spring  24 f engages with an end of the plate  24 b and the other end of the spring  24 f engages with a pin  24 g disposed adjacent to the axle  24 a. 
     Along the both side edges of the carrier  3 , at the front and rear end portions thereof, four vertically rising pieces  26 ,  27 ,  28  and  29  are formed. A cam  4 ,  5 ,  6 ,  7  is arranged corresponding to each of the pieces  26 ,  27 ,  28  and  29  in such a way that a functioning axle  4 a,  5 a,  6 a,  7 a of the cam  4 ,  5 ,  6 ,  7  is inserted into a through-hole formed in each piece  26 ,  27 ,  28 ,  29 . The cam  4 ,  5 ,  6 ,  7  has another functioning axle  4 b,  5 b,  6 b,  7 b formed on the same side as the axle  4 a,  5 a,  6 a,  7 a. Each axle  4 b,  5 b,  6 b,  7 b is inserted into a through-hole  30 ,  31 ,  32 ,  33  formed in each of both side walls of the tray  2 . It is to be noted that the holes  31  and  33  are desirably formed as an oval hole to absorb the unevenness of the assembling accuracy of the cam. 
     The cam  4 ,  5 ,  6 ,  7  has a pivot axle  4 c,  5 c,  6 c,  7 c formed on the other side of the functioning axle side, as illustrated in FIG. 1b which is representing only the cam  4  but the same as for the other cams  5 ,  6  and  7 . The pivot axle  4 c,  5 c,  6 c,  7 c is inserted into each of through-holes  1 c,  1 d,  1 e and  1 f formed in side plates  1 a and  1 b vertically disposed along both of the right and left side edges of the chassis  1 . 
     In accordance with the arrangement mentioned above, the cams  4 ,  5 ,  6  and  7  are rotatably attached to the chassis  1  and interconnect the tray  2  and carrier  3  as well. Also, due to this arrangement, the movement direction of the tray  2  is limited to the direction which is allowed by the cams  4 ,  5 ,  6  and  7 . 
     Also, at the root portion of each pivot axle  4 c,  5 c,  6 c,  7 c of the cam  4 ,  5 ,  6 ,  7  is formed a hub  4 d,  5 d,  6 d,  7 d protruding from the cam disk surface, as illustrated in FIG. 1b, so as to decrease the contact area between the cam and the chassis aiming at reduction of the frictional force generated therebetween. Further, the cam  4 ,  5 ,  6 ,  7  is made from resin having a low frictional coefficient such as polyacetal so as to minimize the frictional force generated in the contact area between the cam and the chassis. 
     The tray  2  is formed in such a shape that the tray holds the disk cartridge from upper side and the both right and left sides thereof. Also, the tray  2  has a support rim member along each of the right and left side edges of the tray at the lower portion thereof. The inlet portion for the cartridge of the rim member of the tray  2  is cranked downward. 
     Inside of the tray  2 , two levers  25  and  34  are rotatably arranged to open and close a shutter of the disk cartridge as described later. The levers  25  and  34  are biased outward. A guide pin or engaging hook  35 ,  36  is disposed on the upper surface of each of the levers  25  and  34 . The guide pins (hooks)  35  and  36  are inserted in circular arc shaped guide slots  37  and  38  formed in the upper plate member of the tray  2 , respectively, engaging with the rim of each slot opening. The hooks  35  and  36  are guided along the slots  37  and  38 , respectively, whereby the movement directions of the levers  25  and  34  are limited. Also, the levers  25  and  34  are disposed at different levels so that they can move without interfering with each other. 
     In the lever  25  is formed a longitudinal hole  38  through which the latch pin  24 c penetrates. Also, a cut away  39  is formed in the lever  25  opening the hole  38  out of the lever  25  so as to guide the latch pin  24 c into and out of the hole  38 . 
     On the upper surface of the tray  2  is mounted a magnetic head  40  for generating an auxiliary magnetic field within a movable range of the optical pickup. Also, inside of the tray  2 , along the both right and left side edges of the tray  2 , pressing strip members  41  and  42  are arranged to limit the height of the disk cartridge by pressing the cartridge from upper side thereof. The pressing members  41  and  42  are biased downward by leaf springs  43  and  44 , respectively. Only one of the leaf springs  43  is illustrated in FIG.  1 a. 
     FIGS. 2a and 2b illustrate an example of the disk cartridge which is driven by the drive unit in accordance with the present invention. 
     As illustrated in FIG. 2a, in the center portion of the disk cartridge  55  is formed a rectangular access window  56  which is longitudinal in the insertion direction of the cartridge. The window  56  is opened and closed by a shutter  57 . The shutter  57  is arranged as being folded from an edge portion  60  of the cartridge  55 . 
     The shutter  57  arranged as mentioned above has openings  58  and  59  for receiving the above mentioned levers  25  and  34 , respectively. 
     In accordance with the above mentioned structure, in the event wherein the disk cartridge  55  is not housed in the tray  2 , as illustrated by dash-two-dot lines in FIG. 3, the latch roller  24 e of the latch mechanism  24  is being caught in the recess  24 d of the carrier  3 . Thereby, the eject springs  22  and  23  are made unenforceable to the carrier  3 . 
     Also, in this state, the carrier  3  is waiting for insertion of the cartridge at the rearmost position with respect to the insertion direction. Therefore, as illustrated by solid lines in FIG. 4, the axles  4 b,  5 b,  6 b and  7 b of the cams  4 ,  5 ,  6  and  7  are being positioned at the uppermost level thereof. Accordingly, the insertion opening for the cartridge formed in the front side of the tray  2  comes to the same level as the insertion inlet  71  formed in the front panel  70  disposed in front of the chassis  1 . 
     From this state, when the disk cartridge  55  is inserted into the tray  2 , the levers  25  and  34  enter into the openings  58  and  59  of the shutter  57 , respectively, so that the shutter  57  is gradually opened according to the insertion motion of the cartridge. On the middle of the insertion motion of the cartridge into the tray  2 , the latch pin  24 c enters into the oval hole  38  of the lever  25  through the cut away opening  39  formed continuous to the hole  38  of the lever  25 . When the lever  25  is further moved according as the cartridge  55  is further inserted toward the rearmost side of the tray  2 , the latch pin  24 c is pushed by the lever  25  so that the latch plate  24 b is rotated in the clockwise direction against the bias force of the latch spring  24 f. 
     Due to this function, at the time when the lever  25  is moved to the rear end position so that the shutter  57  is completely opened, as illustrated by solid lines in FIG. 3, the latch pin  24 c is moved to an end of the oval hole  38  and the latch roller  24 e is disengaged from the recess  24 d of the carrier  3 . Therefore, the eject springs  22  and  23  act on the carrier  3  so that the carrier  3  is forced to move in the ejecting direction toward the front side of the unit. Also, in this state, the bias force which acts upon the levers  25  and  34  is made unenforceable on the levers due to the function of the latch mechanism  24 . 
     As a result of the series of function as mentioned above, as illustrated by dash-two-dot lines in FIG. 4, the cams  4 ,  5 ,  6  and  7  rotate in the clockwise directions since the axles  4 a,  5 a,  6 a and  7 a of the cams  4 ,  5 ,  6  and  7  are forced to move in the cartridge ejecting direction according as the carrier  3  moves. 
     As a result, the axles  4 a,  5 a,  6 a and  7 a of the cams  4 ,  5 ,  6  and  7  are moved lowermost position thereof so that the tray  2  descends to the position for loading the disk drive unit. 
     Also, in this state, the functioning surface of the magnetic head  40  is positioned in the vicinity of the recording surface of the magneto-optic disk (not shown) housed in the disk cartridge  55 . 
     When the disk cartridge  55  is inserted in that way mentioned above, the carrier  3  is shifted in the ejecting direction toward front side of the unit and the tray  2  is moved arching downward along a circular arc so that the disk cartridge  55  is aligned with a predetermined position. 
     Next, the operation of ejecting the disk cartridge is described below. 
     When the disk cartridge  55  is to be ejected from the drive unit, the operator presses an eject button (described later) so that the eject pin  14  is moved in the cartridge insertion direction toward the rear side of the unit by the eject mechanism (described later) in cooperation with the eject button. Thereby, the carrier  3  is moved in the cartridge insertion direction against the force of the eject springs  22  and  23 . According as the carrier  3  moves in the insertion direction, the cams  4 ,  5 ,  6  and  7  are rotated in the counterclockwise in FIG. 4 so that the tray  2  ascends gradually. 
     On the other hand, the latch plate  24 b of the latch mechanism  24  is biased to rotate counterclockwise by the latch spring  24 f. Therefore, when the carrier  3  moves and comes to the position where the recess  24 d formed in the carrier  3  faces to the latch roller  24 e, the roller  24 e falls into the recess  24 d. 
     At the same time when the roller  24 e is caught into the recess  24 d, the latch plate  24 b is rotated so that the latch pin  24 c pushes the lever  25  and that the pin  24 c disengages from the oval hole  38  of the lever  25 . 
     Accordingly, in the state wherein the tray  2  is moved to the uppermost position thereof, the levers  25  and  34  and the latch mechanism  24  apply force on the disk cartridge  55  so that the cartridge  55  is pushed out of the tray  2  and that a part of the cartridge  55  projects from the insertion inlet  71  formed in the front panel  70 . Thereby it becomes possible to draw the cartridge  55  out of the tray  2 . 
     As mentioned above, the carrier  3  reciprocates and simultaneously therewith the tray  2  moves upward or downward along the circular arc trail in accordance with the movement of the carrier  3  so that the cartridge  55  is loaded or unloaded. 
     Also, in accordance with this particular embodiment of the present invention mentioned above, tray  2  descends drawing the cartridge  55  toward the rear side of the unit, which makes it possible to install the cartridge  55  in the drive unit simply by pushing the cartridge  55  into the inlet  71 . That is, it becomes unnecessary to push the cartridge  55  by a finger until the cartridge  55  comes to the rear end of the inside of the disk drive unit. 
     FIGS. 5a and 5b illustrate an example of the eject mechanism in accordance with the present invention. 
     In the drawings, the eject mechanism comprises a plate  75  on which an eject motor  76  is mounted. A worm  77  is installed on the output shaft of the motor  76 . The worm  77  engages with a worm wheel  79  which is rotatably installed on a pin  78  mounted on the plate  75 . 
     A male engagement member  82  is secured to the upper surface of the worm wheel  79  coaxially therewith and rotatable about the pin  78 . The engagement member  82  engages with a female engagement member  81  which projects downward from the chassis  1  through a hole  15 . The member  81  is formed as an integral structure with a cam  80  and rotates coaxially therewith. Also, the plate  75  is secured to the under side of the chassis  1  by means of screws. 
     In accordance with the structure mentioned above, when the eject motor  76  is driven to rotate, the rotational force thereof is transmitted to the cam  80  through the worm  77 , worm wheel  79 , and the engagement members  81  and  82  so that the cam  80  rotates in the same direction as the worm wheel  79 . 
     Next, in the FIGS. 14a and 14b, a protrusion  791  mounted on a lower portion of the worm wheel  79  pushes a lever of a switch to thereby stop the worm wheel  79  in a predetermined position. In this moment, the protrusion  791  and the cam  80  has a particular positional relationship therebetween. When the engagement member  81  of the cam  80  and the engagement member  82  are engaged with each other, they can be engaged in two directions. However, one of the two directions of the engagement will cause to disturb an operation of the eject pin  14 . Therefore, as shown in FIG. 14c, in order to avoid such a disturbance, widths (C, D) of notches  821  of the engagement member  82  are made different from each other so that the cam  80  and the worm wheel  79  are engaged with each other only in a desired one direction. 
     Next, the function of the cam  80  is described with reference to FIGS. 6a to  6 d below. 
     In a state wherein the disk cartridge  55  is not installed in the drive unit, as illustrated by the solid line in FIG. 6a, the eject pin  14  of the carrier  3  is positioned at the rearmost position in the anti-eject direction apart from the cam  80  as mentioned above. From this state, when the disk cartridge  55  is inserted, the carrier  3  is moved toward the front side of the unit as mentioned above so that the pin  14  also moves toward the front side of the unit and comes close to the cam  80 . Finally, the pin  14  moves to the position where the pin abuts against the cam  80 , as illustrated by dash line in FIG.  6 a. 
     When the cartridge is to be ejected, according to the command signal to eject the cartridge, the motor  76  is driven to rotate so that the cam  80  is rotated clockwise from the state of FIG.  6 b. Thereby, the pin  14  is gradually shifted toward the rear side of the unit along with the carrier  3  in accordance with the ejecting function thereof as mentioned above (FIGS.  6 c and  6 d). 
     Finally, immediately before the cam  80  is rotated for one turn when the pin  14  comes to the predetermined position in the cartridge ejecting direction, the disk cartridge is ejected from the unit as mentioned above. 
     When the cam  80  is rotated for one turn, the mechanism returns to the initial state. 
     As mentioned above, the cartridge ejecting operation can be achieved by rotating the cam  80  for one turn by the eject motor  76 . 
     Also, in this case, the clearance or gap between the inside rim of the hole  15  and the engagement member  81  penetrating through the hole  15  is very small, so that almost no outer air can flow into the chassis of the unit through the gap formed around the engagement member  81  which constitutes the axle of the cam  80 . 
     In this case, the optical disk drive unit is provided with a cam  80  having such a shape that an increasing rate of a radius of a basic circle of the cam  80  with respect to a rotational angle thereof changes (FIG.  16 c), while conventionally, the increasing ratio thereof is constant (FIG.  16 a). Thereby, a load applied to the eject motor  76  is dispersed, and a life duration of the eject motor  76  can be prolonged. In concrete, as shown in FIG. 15, the relationship α&gt;β is formed in which the radius increasing ratio between the angle 0 and the angle A 1  is dr/dθ=α, and that between the angle A 1  and the A 2  is dr/dθ=β. 
     The reason therefor is as below. A load of a loading, namely a force for enabling a pin  14  to move increases in the latter half of a moving distance of the pin until an ejection of the cartridge, in this loading system. Therefore, when the cam has such an outer configuration that the value of dr/dθ decreases in the latter half of the angular displacement of the cam, the load applied to the eject motor  76  can be uniformed, the load of the eject motor  76  can be decreased, and a time used for the ejection of the cartridge can be shortened (FIGS.  16 b and  16 d). This is because when an electric current flowing in the eject motor  76  is small, the load applied to the eject motor  76  decreases and therefore the life duration of the eject motor  76  is prolonged, 
     FIG. 16e is a view of an example for showing a change of the load of the simplified loading system with respect to a loading stroke. The cam has such a configuration that the angular displacement amount to the point A 1  is large while that beyond the point A 1  is small. 
     Also, in accordance with the arrangement mentioned above, the transmission means for the eject mechanism is disposed outside of the chassis  1 . Therefore, the dusts generated due to the engagement between the worm  77  and the worm wheel  79 , for instance, can be prevented from entering into the chassis  1 . 
     FIG. 7 illustrates an example of the sealing enclosure construction for housing the disk drive unit in accordance with an embodiment of the present invention. 
     In the drawing, a chassis cover  85  is depicted being formed in a shape wherein the lower rim portion of the cover  85  abuts against the upper rim portion of the chassis  1  and wherein the cover  85  is secured to the chassis  1  by a screw  86  at the rear end portion of the chassis  1 . Also, in the front face of the chassis cover  85  is formed an insertion inlet  87  for receiving a disk cartridge which is to be inserted into the drive unit. An urged lid  88  for the inlet  87  is disposed inside the inlet  87  in a state of being biased to close the opening of the inlet and rotatable to open and close the inlet. 
     Small projections  89 ,  90  are formed in both side ends of the inlet member  87 . Only one of the projections  90  is illustrated in FIG.  7 . The projections  90  of the inlet member side fit into small holes  91  and  92  formed in both right and left ends of the front edge of the chassis  1 . The width of the lid  88  disposed in front of the chassis  1  is the same as or slightly smaller than the outer size of the disk cartridge  55 . 
     Also, the inlet  87  is formed in such a shape that the inlet surrounds the whole of the outer surface of the disk cartridge  55  and that the width of the inlet is slightly larger than the outer width of the disk cartridge  55  and height of the inlet is about the same as the thickness of the disk cartridge  55  so that the upper and lower surfaces of the disk cartridge  55  come in slight contact with the upper and lower members which constitute the inlet. 
     A recessed step  93  is formed under the inlet  87 . A front wall  94  is arranged in the front side of the chassis  1 . The vertical front side surface of the step  93  abuts against the vertical inner side surface of the front wall  94 . The height of the front wall  94  is slightly shorter than the leveling pins  8 ,  9 ,  10  and  11  (FIG.  1 ). 
     Also, each of the side plates  1 a and  1 b of the chassis  1  (FIG. 1) has a projecting step formed on its upper surface which step mates with a recessed step formed on the lower surface of each side plate of the chassis cover  85  so that the sealing tightness between the chassis and the cover is enhanced. This structure is illustrated in FIG. 8 which shows the side plate  1 a of the chassis having the step  1 aa projecting from the upper surface of the plate  1 a formed in such a way that the step  1 aa is received by and mates with the recessed step  85 a formed in the lower surface of the side plate of the cover  85 . 
     In accordance with the above mentioned way of arrangement, the chassis cover  85  is attached to the chassis  1  and the inlet  87  for insertion and ejection of the cartridge is closed by the lid  88  so that the inside of the chassis  1  is sealingly closed from outside. 
     Also, the chassis  1  is mounted on and secured to a frame  95  through pads or vibroisolating rubbers  96 ,  97 ,  98  and  99 . 
     Also, a front panel  70  is attached to the front surface of the frame  95 . Vent slots  100  for intaking outer air are formed in the lower portion of the panel  70 . Also, an eject button  101  is arranged on the panel  70 . 
     FIG. 9 illustrates an access mechanism for read/write data on and from the magneto-optic disk assembled in the chassis  1 . The mechanism arranged in the chassis  1  comprises a spindle motor  102  for driving the magneto-optic disk to rotate, a turn table  104  installed on the shaft  103  of the motor  102  for mounting the disk thereon, an optical pickup device  105 , seek motors  106  and  107  for driving the optical pickup device to move and a linear encoder  108  for detecting the schematic position of the optical pickup. 
     A flexible printed wiring board  109  is disposed on the optical pick up device. Necessary circuits for driving the optical pickup  105 , seek motors  106  and  107  and the linear encoder  108  are arranged on the printed wiring board  109 . The wirings of the flexible printed wiring board  109  are connected to pins of a connector  111  which projects into the chassis  1  from underside thereof through a hole  110  formed in the bottom plate of the chassis  1 , as illustrated in FIG.  10 . 
     The connector  111  is connected to a control board  112  disposed under the chassis  1 . Also, the hole  110  is covered and closed by the flexible printed wiring board  109  so that sealing tightness of the hole  109  is raised. 
     The drive circuit and control circuit for the motors disposed in the chassis  1  are mounted on a wiring board  116  disposed in a space between the rear end of the chassis  1  and the rear end of the frame  95 . To this circuit board  116  is connected a heat radiation plate  117  attached to the rear end of the frame  95  so as to radiate the heat generated from the parts mounted on the board  116 . 
     Also, in a state wherein the disk cartridge  55  is installed in the unit, the under surface of the trailing end of the disk cartridge  55  comes in slight contact with the upper surface of the front wall  94  of the chassis  1 . In this state, the disk cartridge  55  comes in contact with the lower member  87 a of the inlet  87  formed in the chassis cover  85  so that the lower part of the cartridge is sealed. Also, the lower edge of the lid  88  comes in contact with the upper surface of the disk cartridge  55  so that the upper part of the cartridge is sealed. Further, both sides of the disk cartridge  55  come in contact with the inner side wall of the inlet  87  so that the both side parts of the cartridge are sealed. 
     As mentioned above, even in the case where the disk cartridge  55  is inserted in the unit, the sealing tightness between the cartridge  55  and the chassis  1  is reliably maintained so that the outer air is almost prevented from entering into the chassis  1  through the gap between the chassis  1  and the cartridge  55 . 
     Besides, the impact force which acts upon the chassis  1  is absorbed by the vibroisolating rubbers  96 ,  97 ,  98  and  99 , which keeps the gap between the chassis  1  and the members surrounding the chassis closed so that the sealing tightness of the chassis is maintained being unchanged even when an impact force acts upon the chassis. 
     In accordance with the above mentioned arrangement of the enclosure for disk cartridge, the access mechanism housed in the chassis  1  is always sealingly enclosed in the chassis and discommunicated from the outside of the chassis. Therefore, even in the event where the cooling air is ventilated into the frame  95 , the outer air is essentially prevented from entering into the access mechanism as a result of which it becomes possible to avoid the event that dusts included in the air stick to the optical parts of the pickup device. 
     Further, the heat generating sources such as the drive circuit and the control circuit for the access mechanism are assembled on the circuit board  116  disposed at the rear end portion of the frame  95  so that the heat is prevented from being accumulated in the chassis  1  to a certain degrees. Also, the heat from inside of the chassis  1  is radiated to outside of the chassis  1  through the outer surface of the chassis  1  and the its cover  85 , which makes it possible to keep the temperature in the chassis  1  within an allowance range for the access mechanism and the magneto-optic disk. 
     it is to be noted that by constituting the chassis  1  from die casting material, it becomes possible to raise the accuracy of size of each part of the chassis, which further enables to raise the sealing tightness of the chassis  1 . 
     It is also to be noted that by constituting the chassis cover  85  from plastic material, it becomes possible to easily realize a complicated shape, which makes it possible to obtain a high sealing tightness without using a special sealing member. Also, the chassis cover  85  is easily attached to the chassis  1  as well and the lid  88  is also easily attached to the chassis cover  85 . 
     FIG. 11 illustrates an example of the block diagram of the control system for the disk drive unit in accordance with the present invention. 
     In the drawing is represented a control unit  120  which transmits and exchanges various data between the host device so as to control the function of the magneto-optic disk device. The control unit  120  also controls the functions of the eject motor  6 , the spindle motor  102 , the photo pickup device  105  and the seek motors  106  and  107 . 
     Numeral  121  designates a group of sensors such as a write protect sensor  48 , and media mark sensors  45 ,  46  and  47 . The detected signals output from the sensors  121  are transmitted to the control unit  120 . The on/of signal output from the eject switch  122  operated in cooperation with the eject button  101  is also transmitted to the control unit  120 . Further, The detection signal output from the position sensor  123  which detects one turn of the cam  80  is also transmitted to the control unit  120 . 
     FIG. 12 illustrates a flow chart of the sequence executed by the control unit  120  at the time when the eject switch  122  is turned on by pressing the eject button  101 . 
     First, whether the spindle motor  102  is stopped or not is checked in step  201 . If the check result is NO, the spindle motor  102  is deenergized to stop (step  202 ). 
     When the motor  102  is stopped in such a way, the eject motor  76  is driven to rotate until the position sensor  123  outputs the detection signal (step  203 ). 
     It is to be noted that, in accordance with the sealing arrangement of the embodiment mentioned above, the gap between the shaft (engagement member)  81  of the cam  80  and the inside wall of the hole  15  formed in the chassis  1  is not completely sealed. However, instead of such an arrangement, to achieve a complete sealing at this portion, it may be possible to arrange an oilless type metal bearing  210  for the shaft  81  which bearing fits into the hole  15 , as illustrated in FIG.  13 a. Or otherwise, it also may possible to arrange a sealing type ball bearing  211  for the shaft  81  which bearing fits into the hole  15 , as illustrated in FIG.  13 b. 
     Further, instead of those arrangements mentioned above, it also may possible to arrange the sealing structure in such a way that a wall  15 a is formed on the chassis floor member surrounding the hole  15  and that a sealing wall  80 a is formed hanging from the cam  80  and covering the wall  15 a from outer side thereof, as illustrated in FIG.  13 c. In accordance with this arrangement, the gap between the wall  15 a and the sealing member  80  is cranked and constitutes a labyrinth seal structure so that it becomes possible to almost completely prevent the entrance of the outer air through the gap into the chassis. 
     It is to be noted that in accordance with the embodiment mentioned above, the invention is applied to a magneto-optic disk drive unit. However, the present invention can be applied to an optical disk drive unit as well. 
     It is also to be noted that in accordance with the embodiment mentioned above, the cartridge insertion inlet portion of the chassis cover is formed in such a shape that the inlet member surrounds the entire surface of the disk cartridge to be inserted. However, the lower side member of the inlet can be deleted without impairing the effect of the present invention. 
     As mentioned above, in accordance with the present invention, the drive means for driving the eject pin is disposed outside of the sealing enclosure unit housing the disk drive arrangement, which makes it possible to effectively prevent the entrance of the dusts or other minute particles generated from the driving mechanism into the enclosure unit. Also, in accordance with the present invention, the arrangement is made to close the gap between the inner side wall of the hole formed in the chassis and the linkage member which is disposed between the cam and the cam drive means and penetrates through the hole to interconnect the cam and the drive means together, which makes it possible to reliably prevent the entrance of dusts or other particles into the drive unit enclosure through the gap. 
     Many widely different embodiments of the present invention may be constructed without departing from the spirit and scope of the present invention. It should be understood that the present invention is not limited to the specific embodiments described in the specification, except as defined in the appended claims.