Disc cartridge

Abstract: A disc cartridge for rotatably accommodating an information carrier disc (1), which comprises a first casing (2) having a first cavity (2c) defined therein for accommodating a portion of the information carrier disc (1), and a second casing (3) having a second cavity (3c) defined therein for accommodating a remaining portion of the information carrier disc (1) and operatively coupled with the first casing (2) for movement relative to the first casing (2) between extended and retracted positions to bring the disc cartridge into opened and closed positions, respectively. Springs (5) are provided for urging the second casing (3) to the first position. When the second casing (3) is moved against the springs (5), the disc cartridge is brought to the opened position, allowing one or more access openings (2d) to be exposed to the outside of the disc cartridge. A disc retainer (6) is also provided for avoiding any arbitrary motion of the information carrier disc (1) within a disc chamber defined by the first and second cavities (2c, 3c) in the first (2) and second (3) casings.

Description: The present invention generally relates to a disc cartridge for use on an information read/write apparatus and, more particularly, to the disc cartridge particularly suited for use on the information read/write apparatus of a type employing a plurality of recording and/or reproducing heads. As is well known to those skilled in the art, an information carrier disc such as, for example, an optical disc, is accommodated within a generally rectangular disc cartridge not only for protecting the information carrier disc from being contaminated by finger prints and/or dust, but also for improving an operativity of the information read/write apparatus. For example, the Japanese Laid-open Patent Publication No. 60-98578, published June 1, 1985, discloses a generally rectangular flat disc cartridge accommodating therein a round information carrier disc. This prior art disc cartridge is so designed and so structured that the user of the apparatus need not remove the information carrier disc from the disc cartridge in readiness for a loading thereof into the information read/write apparatus, remove the empty disc cartridge after the loading and insert the empty disc cartridge in readiness for a recovery of the information carrier disc from the information read/write apparatus after an information recording or reading has been completed. The prior art disc cartridge referred to above has a width in a direction perpendicular to the direction of insertion or removal of the disc cartridge into or from the information read/write apparatus, which is somewhat smaller than the length thereof in a direction perpendicular to the widthwise direction thereby to avoid an incorrect insertion of the disc cartridge into the information read/write apparatus. This disc cartridge comprises front and rear casings defined by splitting the disc cartridge across the width thereof at a position generally intermediate of the length thereof, the front casings being adapted to move a first predetermined distance relative to the rear casing in the lengthwise direction of the disc cartridge. Generally elongated stationary and movable support members are provided on each side of the information carrier disc within the disc cartridge and along each of opposite side walls thereof. Only the movable support members on the respective sides of the information carrier disc are movable a second predetermined distance, which is half the first predetermined distance, a direction conforming to the lengthwise direction of the disc cartridge. The elongated movable support members while the front and rear casings are closed together cooperate to support the information carrier disc in a fixed position within the disc cartridge. However, when the front and rear casings are separated from each other by moving the front casing relative to the rear casing over the first predetermined distance leaving an access opening therebetween, the elongated movable support members are moved the second predetermined distance relative to the stationary support members within the rear casing, allowing the information carrier disc in position ready to be rotated for an information reading or writing operation. When in use on the information read/write apparatus, the disc cartridge in a closed position is inserted into or ejected from a cartridge receiving mouth in the apparatus. The information read/write apparatus must have a cartridge loading and unloading mechanism installed therein. The cartridge loading and unloading mechanism two parallel rows of paired roller elements grouped for each of the front and rear casings. Although first and second groups of the paired roller elements are driven at the same speed up until the disc cartridge in the closed position is completely inserted into a cartridge receiving mouth in the apparatus, the first group of the paired roller elements are held still while the second group of the paired roller elements are allowed to continue rotation so that the rear casing within the cartridge receiving mouth can further be moved relative to the front casing to form the access opening between the front and rear casings with the disc cartridge consequently held in an open position. The access opening between the front and rear casings is of a size corresponding to a turntable or a chuck assembly by which the information carrier disc can be clamped for rotation together with a motor-coupled spindle. The movement of the paired movable support members over the second predetermined distance, i.e., half the first predetermined distance is necessitated to bring a centre hole of the information carrier disc into alignment with the longitudinal axis of the motor-coupled spindle and at a 5 position generally exactly intermediate of the spacing of the access opening. As discussed above, the prior art disc cartridge is complicated in structure employing a substantial number of component parts enough to adversely affect the reliability of operation of the disc cartridge and, at the same time, requires the information read/write apparatus to be equipped with a complicated cartridge loading and unloading mechanism. EP-A-0,142,099 discloses a disc cartridge for rotatably accommodating an information carrier disc (1), comprising: a first casing having a first cavity defined therein for accommodating a portion of the information carrier disc, said information carrier disc being retained rotatably within said first cavity; a second casing having a second cavity defined therein for accommodating a remaining portion of the information carrier disc and operatively coupled with said first casing for movement relative to the first casing and also to the information carrier disc between extended and retracted positions to bring the disc cartridge into opened and closed positions, respectively; and at least one of said first and second casing having an access opening defined therein for an access of a turntable and at least one head, both provided in an information read/write apparatus, to the information carrier disc, said access opening being exposed to the outside when the second casing is moved to the extended position relative to the first casing and also to the information carrier disc. According to the present invention such a disc cartridge is characterised in that it further comprises at least one shutter operatively associated with the first casing or second casing and mounted on the other of the said first casing and said second casing for movement between first and second positions, said shutter being moved to the first position to open the access opening in response to the movement of the second casing to its extended position. Preferably, the disc cartridge may have a disc retainer for avoiding any arbitrary motion of the information carrier disc within a disc chamber defined by the first and second cavities. Also, preferably, a locking means may be provided on one of the first and second casings, which comprises a lock pawl means pivotally mounted inside the other of the first and second casings and engageable with said guide means, a biasing means for urging the lock pawl means towards the guide means, and a lock release means having a portion exposed to the outside from the cavity in the other of the first and second casings and operable to press the lock pawl means. In the present invention, since the first and second casings are separable from each other, the number of movable component parts is minimized and the cartridge loading and unloading mechanism provided in the information read/write apparatus suffices to have, for example, pawls as stoppers in order for the disc cartridge to be properly positioned inside the cartridge loading and unloading mechanism and also to be brought into the opened position, making it possible to provide the disc cartridge that has a simplified structure and a high reliability. The selective opening and closing the shutter is operatively associated with the movement of one of the casings relative to the other of the casing and, therefore, no shutter opening and closing mechanism is necessary in the information read/write apparatus. Moreover, since the disc retainer disengages from the information carrier disc in response to the movement of one of the casings to the extended position relative to the other of the casings, the information read/write apparatus is not required to have a release mechanism for releasing the disc retainer, making it possible to manufacture it in a simplified structure. Furthermore, the first and second casings are lockable together by means of the locking means and, therefore, there is no possibility that the user may unnecessarily touch the information carrier disc. Particular embodiments of disc cartridges in accordance with the present invention will now be described with reference to the accompanying drawings, in which: Fig. 1 is an exploded view of one of the casing halves of the disc cartridge according to a first preferred embodiment of the present invention, with the upper panels removed; Fig. 2 is an exploded view of the other of the casing halves of the disc cartridge according to the first preferred embodiment of the present invention, with the upper panels of the respective casing halves removed; Fig. 3 is an exploded view of the disc cartridge according to the first preferred embodiment of the present invention, showing the upper panels of the respective casing halves; Fig. 4 is a perspective view of the disc cartridge according to the first preferred embodiment of the present invention showing the disc cartridge in the closed position; Fig. 5 is a perspective view, on an enlarged scale, of the disc cartridge according to the first preferred embodiment of the present invention showing the disc cartridge in the opened position; Figs. 6 and 7 are cross-sectional views of the disc cartridge taken along the lines I-I and II-II shown in Figs. 4 and 5, respectively; Figs. 8 to 12 are views similar to Figs. 1 to 5, respectively, showing a second preferred embodiment of the present invention; and, Figs. 13 and 14 are cross-sectional views of the disc cartridge taken along the lines I-I and II-II shown in Figs. 11 and 12; First Embodiment (Figs. 1 to 7) Referring to Figs. 1 to 7, a generally rectangular flat disc cartridge has a width in a direction perpendicular to the direction of selective insertion or removal of the disc cartridge into or from the information read/write apparatus and also has a length in a direction conforming to the direction of selective insertion or removal of the disc cartridge and perpendicular to the widthwise direction thereof. The disc cartridge contains therein a single-sided or double-sided information carrier disc 1 generally loosely accommodated therein for rotation about its centre and comprises first and second casings 2 and 3 operatively coupled together and supported for movement relative to each other to selectively bring the disc cartridge into opened and closed positions. Each of the first and second casings 2 and 3 is made of a relatively hard synthetic resin such as, for example, ABS resin. The first casing 2 oversized relative to the second casing 3 comprises generally rectangular upper and lower panels 2a and 2b of similar shape assembled together by the use of set screws or by the use of any known fusion-bonding technique while leaving a first cavity 2c defined therein for accommodating a part of the information carrier disc 1. This first cavity 2c is of a shape occupying a portion of a circle, but oversized relative to the semicircle so that a corresponding portion of the round information carrier disc 1 can be accommodated therein. Reference numeral 2d represents a centre hole defined in the first casing 2 for the access of the turntable of the information read/write apparatus thereto. This centre hole 2d is adapted to permit a turntable and a clamper, both provided in the information read/write apparatus, to clamp the information carrier disc 1 in position relative to a motor coupled spindle when the disc cartridge is loaded into the information read/write apparatus and is subsequently held in the opened position. A portion of the first casing 2 where this centre hole 2d is defined is, as will be described later, concealed within the second casing 3 when the disc cartridge is in the closed position as shown in Fig. 6. Reference numeral 2e represents a positioning stop provided on each side of the first casing 2 for positioning the disc cartridge at an inserted position within the cartridge loading and unloading mechanism when the disc cartridge is inserted into the apparatus through a cartridge receiving mouth (not shown). Reference numeral 2f represents positioning holes. One of the positioning holes 2f is of a generally round shape and the other of the positioning holes 2f is of a generally rectangular shape so that, when the disc cartridge is inserted into the cartridge loading and unloading mechanism in the information read/write apparatus, the first casing 2 can be properly positioned. Reference numeral 2g represents a positioning recess 2g provided on each side of the first casing 2 for the purpose of permitting the disc cartridge to be used on an automatic cartridge stacker by which a plurality of disc cartridges can be loaded into and removed from the cartridge loading and unloading mechanism automatically one at a time. The positioning recesses 2g are necessitated for component parts of the automatic loading mechanism to hold the disc cartridge in the automatic cartridge stacker. Reference numeral 2h represents a groove provided on each side of the first casing 2 for receiving a portion 4a of a respective generally elongated guide bar 4 as will be described later. Reference numeral 2i represents a recess for accommodating an erroneous erasure preventing pawl 7 for movement in a widthwise direction of the disc cartridge. Reference numeral 2j represents a detection hole. Whether or not the information carrier disc within the disc cartridge can be recorded can be detected depending on whether the erroneous erasure preventing pawl 7 is engaged in this detection hole 2j or whether it is not engaged in this detection hole 2j. Reference numeral 2ℓ represents an anchor pin for engagement with one end 11a of a tension spring 11 as will be described later. Reference numeral 2m represents stud shafts on which respective pulleys 12 are mounted as will be described later. Reference numeral 2n represents a guide rail engageable in a guide groove 9a in a shutter guide 9 as will be described later. Reference numeral 2o represents a positioning groove in which a belt holder 13 as will be described later is seated. The second casing 3 similarly comprises generally rectangular upper and lower panels 3a and 3b of similar shape assembled together by the use of set screws or by the use of any known fusion-bonding technique while leaving a second cavity 3c defined therein for accommodating the rest of the information carrier disc 1. This second cavity 3c is of a shape occupying a portion of a circle, but forms a round disc chamber in cooperation with the first cavity 2c in the first casing 2. It is to be noted that the first and second cavities 2c and 3c have respective steps defined therein at a position corresponding to an outer periphery of the information carrier disc and also at a position corresponding to an inner peripheral portion of the information carrier disc so that, when and so long as the disc cartridge is not in use, the information carrier disc can be supported in position within the disc chamber with non-recorded areas thereof resting on the steps. Reference numeral 3d represents a generally V-shaped positioning indent 3d defined on each side of the second casing 3 used to enable a chucking of the disc cartridge when the latter is loaded into the cartridge loading and unloading mechanism. Reference numeral 3j represents an access opening 3 defined in the second casing 3 for the access of read/write heads to the information carrier disc 1 inside the disc cartridge. Reference numeral 3k represents an anchor pin 3k to which one end lla of another tension spring 11 as will be described later is engaged. Reference numeral 31 represents holes to which pulleys 12 are journalled as will be described later. Reference numeral 3m represents a guide rail adapted to be engaged in a guide recess 9a in a shutter guide 9 as will be described later. Reference numeral 3n represents a positioning portion in which a belt holder 13 as will be described later is inserted and held in position. The guide bars 4 are fixedly placed within the respective grooves 2h in the first casing 2 with end portions 4a thereof received therein while the respective opposite end portions 4b serve as parallel guides along which the second casing 3 slides relative to the first casing 2 in a direction conforming to the lengthwise direction of the disc cartridge. These guide bars 4 are preferably made of a synthetic resin, for example, polyacetale, of a kind having a relatively high wear resistance chosen in consideration of the material that is used for the second casing 3. Reference numeral 6 represents a generally elongated disc retainer serving as means for suppressing an arbitrary motion of the information carrier disc 1 within the disc chamber. This disc retainer 6 comprises a cap-like pad 6a, a coiled compression spring 6b and a pad holder 6c. The caplike pad 6a is capped onto a tip 6g of the pad holder 6c and has an outer end face 6d adapted to contact the outer peripheral edge of the information carrier disc 1 to retain the latter in position within the disc chamber. Preferably, the pad 6a is made of a soft material such as, for example, butyl rubber, for the purpose of protecting the information carrier disc 1 from being damaged. The coiled compression spring 6b is mounted around a cylindrical body 6k of the pad holder 6c, having one end 6f engaged to a stopper 3i, integral with the second casing 3 and having a recess 3g defined therein, and the opposite end 6e engaged to an annular collar 6j integral with the pad holder 6c. The pad holder 6c is mounted in the second casing 3 with another cylindrical body 6h seated within a recess 3f defined in the second casing 3 and also with the cylindrical body 6k seated within the recess 3g and is axially movable, but is normally biased in a direction with the pad 6d partly protruding into the disc chamber. The pad holder 6c is preferably made of a synthetic resin, for example, polyacetale, of a kind having a relatively high wear resistance chosen in consideration of the material that is used for the second casing 3, for facilitating an axial sliding motion of the pad holder 6c. Although the compression spring 6c serves to bias the pad holder 6 in a direction permitting the pad 6a to partly protrude into the disc chamber, the pad holder 6c is axially inwardly pressed in contact with the outer peripheral edge of the information carrier disc 1 when and so long as the information carrier disc 1 is accommodated within the disc chamber in the disc cartridge and, at the same time, the disc cartridge is held in the closed position. It is to be noted that, when the pad holder 6c is so pressed axially inwardly, an annular end face 6i of the collar 6i integral with the pad holder 6c is disengaged from an engagement face 3h of the second casing 3 with the compression spring 6c consequently compressed axially inwardly, applying a biasing force to the outer peripheral edge of the information carrier disc through the pad 6a. As a matter of course, the magnitude of the biasing force applied to the outer peripheral edge of the information carrier disc can be adjusted by suitably selecting the compression spring 6b having a required force and/or capable of being axially inwardly compressed in a required quantity. The erroneous erasure preventing pawl 7 is movably accommodated within the recess 2i in the first casing 2 and is operable to detect whether or not the information carrier disc 1 is recordable with information. The shutters 8 are used to selectively open and close the access openings 2k and 3j, respectively, in the first and second casings 2 and 3. These shutters 8 have an equal width, as measured in a direction perpendicular to the direction of insertion of the disc cartridge, and also an equal thickness as measured in a direction perpendicular to a plane of rotation of the information carrier disc 1, but have different lengths as measured in a direction conforming to the direction of insertion of the disc cartridge. Specifically, the shutter 8 in the second casing 3 has a length greater than that in the first casing 2 by a quantity corresponding to the spacing between the first and second casings 2 and 3 when the disc cartridge is in the opened position. Each of the shutters 8 has the corresponding shutter guide 9 secured thereto by means of a screw hole 9b and a hole 8a in the respective shutter 8 with the guide groove 9a receiving therein the guide rail 2n or 3m so that the respective shutter 8 can slide in a direction perpendicular to the direction of insertion of the disc cartridge. Each of the shutter guides 9 is preferably made of a synthetic resin, for example, polyacetale, of a kind having a relatively high wear resistance chosen in consideration of the material that is used for the first or second casing 2 or 3, for facilitating a sliding motion of the respective shutter. Reference numeral 10 represents a belt provided on each side of the disc cartridge. Each of the belt has holes lOa and lOb defined at opposite ends thereof and is disposed in position with the hole lOa fixed to a screw hole 9c and with the hole lOb fixed to a screw hole 13a in the belt holder 13. Each of the tension springs 11 has one end lla anchored to the anchor pin 2ℓ in the first casing 2 or the anchor pin 3k in the second casing 3 and the opposite end llb anchored to an engagement hole 9d in the shutter guide 9. Each of these tension springs 11 is operable to bias the associated shutter 8 in a direction required to cover the access opening 2k or 3j in the first or second casing 2 or 3, respectively. The pulleys 12 provided in each of the first and second casings 2 and 3 journalled in bearing holes 2m or 3Q in the first or second casings 2 or 3, respectively for guiding the associated belt 10. Reference numeral 13 represents a belt holder provided on each of the first and second casings 2 and 3 and received in the positioning groove 2o or 3n in the first or second casing 2 or 3. Reference numeral 14 represents a shutter retainer bonded by the use of a bonding agent to a step 2p in the first casing 2 or a step 30 in the second casing 3 for avoiding any possible float of the associated shutter 8 which would otherwise occur in a direction perpendicular to a plane of the disc cartridge. The first and second casings 2 and 3 are jointed together in end-to-end abutted fashion having a thickness of 1 to 3 mm. The disc cartridge of a construction as described herein above in accordance with the second preferred embodiment of the present invention is used in the following manner in association with the information read/write apparatus (not shown). When the disc cartridge normally held in the closed position with the information carrier disc 1 accommodated therein is to be inserted into the cartridge receiving mouth, the user had to hold an end portion of the disc cartridge on a trailing side with respect to the direction of insertion. As the disc cartridge is inserted into the cartridge receiving mouth, the V-shaped positioning indents 3d in the second casing 3 are chucked by respective holder pins provided in the cartridge loading and unloading mechanism with the disc cartridge consequently guided towards an inserted position deep into the cartridge receiving mouth. During the insertion of the disc cartridge and when the disc cartridge is inserted to a position adjacent respective pawls in the cartridge loading and unloading mechanism, the first casing 2 is trapped with the pawls in the cartridge loading and unloading mechanism engaged in the respective positioning stop 2e, but the second casing 3 is moved against the tension springs 11 until the centre hole 2d is completely exposed to the outside of the disc cartridge. In this manner, the first and second casings 2 and 3 are separated away from each other with the disc cartridge consequently brought into the opened position. Simultaneously with the separation of the first and second casings 2 and 3 away from each other, the tension springs 11 are pulled axially outwardly by the respective belts 10, causing the shutters 8 to move to open the access openings 2k and 3j. At this time, since the information carrier disc 1 is essentially received within the first cavity 2c which is oversized relative to the second cavity 3c in the second casing 3, the information carrier disc remains within the first cavity 2c in the first casing 2 even after the disc cartridge has been brought into the opened position. On the other hand, as the first and second casings 2 and 3 are separated away from each other, the disc retainer 6 moves together with the second casing 3 then moving relative to the first casing 2 and, therefore, the pad 6a naturally disengages from the outer peripheral edge of the information carrier disc 1 thereby automatically releasing the information carrier disc. Once this happens, the information carrier disc 1 is free to rotate about its centre. Thereafter, respective positioning pins in the cartridge loading and unloading mechanism are engaged into the positioning holes 2f in the first casing 2 to hold the first casing 2 at a required position. Simultaneously or substantially simultaneously therewith, the turntable and the clamper, both provided in the information read/write apparatus, approach the centre hole 2d to clamp the information carrier disc 1 in coaxial relationship therewith in readiness for the drive of the information carrier disc 1 in one direction about the motor-coupled spindle. At the same time, two pairs of read/write heads of the information read/write apparatus give access to the information carrier disc 1 through the access openings 2k and 3j from opposite directions perpendicular to a plane of the information carrier disc in readiness for information reading or writing or erasure. The removal of the disc cartridge once inserted deep into the cartridge receiving mouth from the latter will now be described. Simultaneously with release of the positioning of the first casing 2 using the positioning holes 2f, the information carrier disc 1 being clamped is released, allowing the turntable and the clamper to move out of and away from the access openings 2k and 3j. Then, the disc cartridge is discharged in a direction counter to the direction of insertion thereof. At this time, when the chucking of the V-shaped positioning indents 3d in the second casing 3 is released, the second casing 3 is drawn close towards the first casing 2 by the action of the pulling force of the tension springs 11 with the centre hole 2d consequently concealed within the second casing 3, thereby bringing the disc cartridge into the closed position. Simultaneously therewith, the tension springs 11 are caused to restore to their original states by means of the belts 10, causing the shutters 8 to move in a direction required to close the access openings 2k and 3j completely, respectively. It is to be noted that, as the second casing 3 is pulled close towards the first casing 2, the disc retainer 6 fitted to the second casing 3 is axially driven by the compression spring 6c with the pad 6a brought into contact with the peripheral edge of the information carrier disc 1 to automatically retain the information carrier disc 1 in position inside the disc cartridge. Even after the disc cartridge has been ejected fro∼ the cartridge loading and unloading mechanism in the information read/write apparatus or the storage thereof outside the information read/write apparatus, the tension springs 11 constantly pull one of the first and second casings 2 and 3 close to the other of the first and second casings 2 and 3 and, therefore, the centre hole 2d and the access openings 2k and 3j are kept concealed and, at the same time, the information carrier disc 1 is retained substantially fixedly inside the disc cartridge by the action of the disc retainer 6. Thus, in the foregoing embodiment, only one of the first and second casings 2 and 3, particularly the second casing 3, is moved close towards the other of the first and second casings 2 and 3, that is, the first casing 2, to close the disc cartridge. Therefore, the number of movable component parts necessary to permit the second casing 3 to close towards and away from the first casing 2 is considerably reduced. Also, in order to selectively open and close the disc cartridge embodying the present invention, the cartridge loading and unloading mechanism in the information read/write apparatus suffices to have the pawls serving as stoppers, making it possible to simplify the cartridge loading and unloading mechanism. Thus, the foregoing embodiment of the present invention is effective to provide the improved disc cartridge of high reliability. Since the access openings 2k and 3j are automatically selectively opened and closed with the associated shutters operatively associated with the relative movement of the first and second casings 2 and 3 to selectively bring the disc cartridge into the opened and closed positions, no selective opening and closing is necessary which has hitherto beer accomplished by chucking the shutters by means of, for example, pawls. Attention is called that a single motion, i.e., the relative movement of the first and second casings 2 and 3, is effective to automatically drive a plurality of shutters, that is, the shutters 8. In addition, since when the first and second casings 2 and 3 having respective joint ends of 1 to 3 mm in thickness are jointed together in end-to-end abutted fashion when the∼ disc cartridge is in the closed position, no gap will b∼ formed at the joint even though one or both of the first an second casings 2 and 3 deform or warp, thereby ensuring that no foreign matter such as dust will intrude into the interior of any one of the first and second casings 2 and 3, that is, into any one of the first and second cavities 2c and 3c forming the disc chamber inside the disc cartridge. Also, no scrap of any one of the first and second casings 2 and 3 which would be formed when a shutter is employed in a disc cartridge will enter the disc chamber. The disc cartridge of the above described construction can be utilized in an information read/write apparatus of a type employing at least one read/write heads disposed on one side of the information carrier disc or on each of the opposite sides thereof. By way of example, the information read/write apparatus employing a pair of read/write heads disposed on both sides of the information carrier disc can make use of the disc cartridge of the aforementioned construction. As compared with the information read/write apparatus operable with the prior art disc cartridge utilizing a shutter, the present invention make it possible to reduce the size, particularly, the width and the depth, of the information read/write apparatus. In particular, the information read/write apparatus operable with the disc cartridge of the present invention can have a cartridge insertion path of a length substantially equal to that employed in the information read/write apparatus operable with the prior art disc cartridge. Furthermore, since when the disc cartridge is loaded and positioned in the information read/write apparatus the second cavity in the second casing 3 separate away from the information carrier disc 1, all that is necessary is to accurately position only the first casing 2 and the second casing 3 need not be accurately positioned. Moreover, the disc retainer releases the information carrier disc 1 as the first and second casings 2 and 3 are separated from each other and retains the information carrier disc 1 firmly in position inside the disc chamber automatically when the first and second casings 2 and 3 are closed together. Accordingly, the present invention merely requires the use of the disc retainer at a position distant from the information carrier disc 1 when the first and second casings 2 and 3 are separated from each other and, therefore, no connecting member is needed to associate the movement of one of the first and second casings 2 and 3 with that of the other of the first and second casings 2 and 3, thereby making it possible to reduce the number of component parts used to construct the disc cartridge. Second Embodiment (Figs. 8 to 14) Referring to Figs. 8 to 14, a generally rectangular flat disc cartridge has a width in a direction perpendicular to the direction of selective insertion or removal of the disc cartridge into or from the information read/write apparatus and also has a length in a direction conforming to the direction of selective insertion or removal of the disc cartridge and perpendicular to the widthwise direction thereof. The disc cartridge contains therein a single-sided or double-sided information carrier disc 1 generally loosely accommodated therein for rotation about its centre and comprises first and second casings 2 and 3 operatively coupled together and supported for movement relative to each other to selectively bring the disc cartridge into opened and closed positions. Each of the first and second casings 2 and 3 is made of a relatively hard synthetic resin such as, for example, ABS resin. The first casing 2 oversized relative to the third casing 3 comprises generally rectangular upper and lower panels 2a and 2b of similar shape assembled together by the use of set screws or by the use of any known fusion-bonding technique while leaving a first cavity 2c defined therein for accommodating a part of the information carrier disc 1. This first cavity 2c is of a shape occupying a portion of a circle, but oversized relative to the semicircle so that a corresponding portion of the round information carrier disc 1 can be accommodated therein. Reference numeral 2d represents a generally rectangular access opening defined in the first casing 2 for the access of both of the read/write heads and the turntable of the information read/write apparatus thereto. This access opening 2d is adapted to permit a turntable and a clamper, both provided in the information read/write apparatus, to clamp the information carrier disc 1 in position relative to a motor-coupled spindle when the disc cartridge is loaded into the information read/write apparatus and is subsequently held in the opened position. A portion of the first casing 2 where this access opening 2d is defined is, as will be described later, concealed within the second casing 3 when the disc cartridge is in the closed position as shown in Fig. 18. It is to be noted that the access opening 2d in the upper panel 2a is not made in the form of a hole such as in the lower panel 2b, but is made completely open. Reference numeral 2e represents a positioning stop provided on each side of the first casing 2 for positioning the disc cartridge at an inserted position within the cartridge loading and unloading mechanism when the disc cartridge is inserted into the apparatus through a cartridge receiving mouth (not shown). Reference numeral 2f represents positioning holes. One of the positioning holes 2f is of a generally round shape and the other of the positioning holes 2f is of a generally rectangular shape so that, when the disc cartridge is inserted into the cartridge loading and unloading mechanism in the information read/write apparatus, the first casing 2 can be properly positioned. Reference numeral 2g represents a positioning recess 2g provided on each side of the first casing 2 for the purpose of permitting the disc cartridge to be used on an automatic cartridge stacker by which a plurality of disc cartridges can be loaded into and removed from the cartridge loading and unloading mechanism automatically one at a time. The positioning recesses 2g are necessitated for component parts of the automatic loading mechanism to hold the disc cartridge in the automatic cartridge stacker. Reference numeral 2h represents a groove provided on each side of the first casing 2 for receiving an end portion 4a of a respective generally elongated guide bar 4 as will be described later, and reference numeral 2i represents a recess for accommodating an erroneous erasure preventing pawl 7 for movement in a widthwise direction of the disc cartridge. Reference numeral 2j represents a detection hole. Whether or not the information carrier disc within the disc cartridge can be recorded can be detected depending on whether the erroneous erasure preventing pawl 7 is engaged in this detection hole 2j or whether it is not engaged in this detection hole 2j. Reference numeral 2k represents access openings defined in the first casing 2 for the access of the read/write heads thereto. Reference numeral 2 represents an anchor pin for engagement with one end all of a tension spring 11 as will be described later. Reference numeral 2m represents bearing holes in which respective pulleys 12 are mounted as will be described later. Reference numeral 2n represents a guide rail engageable in a guide groove 9a in a shutter guide 9 as will be described later. Reference numeral 20 represents c positioning groove in which a belt holder 13 as will be described later is seated. The second casing 3 similarly comprises generally rectangular upper and lower panels 3a and 3b of similar shape assembled together by the use of set screws or by the use of any known fusion-bonding technique while leaving a second cavity 3c defined therein for accommodating the rest of the information carrier disc 1. This second cavity 3c is of a shape occupying a portion of a circle, but forms a round disc chamber in cooperation with the first cavity 2c in the first casing 2. It is to be noted that the first and second cavities 2c and 3c have respective steps defined therein at a position corresponding to an outer periphery of the information carrier disc and also at a position corresponding to an inner peripheral portion of the information carrier disc so that, when and so long as the disc cartridge is not in use, the information carrier disc can be supported in position within the disc chamber with non-recorded areas thereof resting on the steps. Reference numeral 3d represents a generally V-shaped positioning indent 3d defined on each side of the second casing 3 used to enable a chucking of the disc cartridge when the latter is loaded into the cartridge loading and unloading mechanism. Reference numeral 3e represent anchor pins to which respective ends 5a of springs 5 are respectively anchored as will be described later. Reference numeral 3j represents an access opening 3 defined in the second casing 3 for the access of read/write heads to the information carrier disc 1 inside the disc cartridge. Reference numeral 3k represents an anchor pin to which one end lla of another tension spring 11 as will be described later is engaged. Reference numeral 3Q represents holes to which pulleys 12 are journalled as will be described later. Reference numeral 3m represents a guide rail adapted to be engaged in a guide recess 9a in a shutter guide 9 as will be described later. Reference numeral 3n represents a positioning portion in which a belt holder 13 as will be described later is inserted and held in position. The guide bars 4 are fixedly placed within the respective grooves 2h in the first casing 2 with end portions 4a thereof received therein while the respective opposite end portions 4b serve as parallel guides along which the second casing 3 slides relative to the first casing 2 in a direction conforming to the lengthwise direction of the disc cartridge. These guide bars 4 are preferably made of a synthetic resin, for example, polyacetale, of a kind having a relatively high wear resistance chosen in consideration of the material that is used for the second casing 3. The springs 5 have respective opposite ends 5a and 5b and is fixed ln position with the ends 5a anchored to the associated engagement pins 3e in the second casing 3 and with the ends 5b anchored to associated engagement pins 4c integral with the respective end portions 4b of the guide bars 4. These tension springs 5 serve to draw the second casing 3 close to the first casing 2 to hold the disc cartridge in the closed position when and so long as the disc cartridge is not in use. Reference numeral 6 represents a generally elongated disc retainer serving as means for suppressing an arbitrary motion of the information carrier disc 1 within the disc chamber. This disc retainer 6 comprises a cap-like pad 6a, a coiled compression spring 6b and a pad holder 6c. The cap-like pad 6a is capped onto a tip 6g of the pad holder 6c and has an outer end face 6d adapted to contact the outer peripheral edge of the information carrier disc 1 to retain the latter in position within the disc chamber. Preferably, the pad 6a is made of a soft material such as, for example, butyl rubber, for the purpose of protecting the information carrier disc 1 from being damaged. The coiled compression spring 6b is mounted around a cylindrical body 6k of the pad holder 6c, having one end 6f engaged to a stopper 3i, integral with the second casing 3 and having a recess 3g defined therein, and the opposite end 6e engaged to an annular collar 6j integral with the pad holder 6c. The pad holder 6c is mounted in the second casing 3 with another cylindrical body 6h seated within a recess 3f defined in the second casing 3 and also with the cylindrical body 6k seated within the recess 3g and is axially movable, but is normally biased in a direction with the pad 6d partly protruding into the disc chamber. The pad holder 6c is preferably made of a synthetic resin, for example, polyacetale, of a kind having a relatively high wear resistance chosen in consideration of the material that is used for the second casing 3, for facilitating an axial sliding motion of the pad holder 6c. Although the compression spring 6c serves to bias the pad holder 6 in a direction permitting the pad 6a to partly protrude into the disc chamber, the pad holder 6c is axially inwardly pressed in contact with the outer peripheral edge of the information carrier disc 1 when and so long as the information carrier disc 1 is accommodated within the disc chamber in the disc cartridge and, at the same time, the disc cartridge is held in the closed position. It is to be noted that, when the pad holder 6c is so pressed axially inwardly, an annular end face 6i of the collar 6i integral with the pad holder 6c is disengaged from an engagement face 3h of the second casing 3 with the compression spring 6c consequently compressed axially inwardly, applying a biasing force to the outer peripheral edge of the information carrier disc through the pad 6a. As a matter of course, the magnitude of the biasing force applied to the outer peripheral edge of the information carrier disc can be adjusted by suitably selecting the compression spring 6b having a required force and/or capable of being axially inwardly compressed in a required quantity. The erroneous erasure preventing pawl 7 is movably accommodated within the recess 2i in the first casing 2 and is operable to detect whether or not the information carrier disc 1 is recordable with information. The shutters 8 are used to selectively open and close the access openings 2k and 3j, respectively, in the first and second casings 2 and 3. These shutters 8 have an equal width, as measured in a direction perpendicular to the direction of insertion of the disc cartridge, and also an equal thickness as measured in a direction perpendicular to a plane of rotation of the information carrier disc 1, but have different lengths as measured in a direction conforming to the direction of insertion of the disc cartridge. Specifically, the shutter 8 in the second casing 3 has a length greater than that in the first casing 2 by a quantity corresponding to the spacing between the first and second casings 2 and 3 when the disc cartridge is in the opened position. Each of the shutters 8 has the corresponding shutter guide 9 secured thereto by means of a screw hole 9b and a hole 8a in the respective shutter 8 with the guide groove 9a receiving therein the guide rail 2n or 3m so that the respective shutter 8 can slide in a direction perpendicular to the direction of insertion of the disc cartridge. Each of the shutter guides 9 is preferably made of a synthetic resin, for example, polyacetale, of a kind having a relatively high wear resistance chosen in consideration of the material that is used for the first or second casing 2 or 3, for facilitating a sliding motion of the respective shutter. Reference numeral 10 represents a belt provided on each side of the disc cartridge. Each of the belt has holes lOa and lOb defined at opposite ends thereof and is disposed in position with the hole lOa fixed to a screw hole 9c and with the hole lOb fixed to a screw hole 13a in the belt holder 13. Each of the tension springs 11 has one end lla anchored to the anchor pin 2ℓ in the first casing 2 or the anchor pin 3k in the second casing 3 and the opposite end llb anchored to an engagement hole 9d in the shutter guide 9. Each of these tension springs 11 is operable to bias the associated shutter 8 in a direction required to cover the access opening 2k or 3j in the first or second casing 2 or 3, respectively. The pulleys 12 provided in each of the first and second casings 2 and 3 journalled in bearing holes 2m or 3Q in the first or second casings 2 or 3, respectively for guiding the associated belt 10. Reference numeral 13 represents a belt holder provided on each of the first and second casings 2 and 3 and received in the positioning groove 20 or 3n in the first or second casing 2 or 3. Reference numeral 14 represents a shutter retainer bonded by the use of a bonding agent to a step 2p in the first casing 2 or a step 30 in the second casing 3 for avoiding any possible float of the associated shutter 8 which would otherwise occur in a direction perpendicular to a plane of the disc cartridge. The first and second casings 2 and 3 are jointed together in end-to-end abutted fashion having a thickness of 1 to 3 mm. The disc cartridge of a construction as described herein above in accordance with the second preferred embodiment of the present invention is used in the following manner in association with the information read/write apparatus (not shown). When the disc cartridge normally held in the closed position with the information carrier disc 1 accommodated therein is to be inserted into the cartridge receiving mouth, the user had to hold an end portion of the disc cartridge on a trailing side with respect to the direction of insertion. As the disc cartridge is inserted into the cartridge receiving mouth, the V-shaped positioning indents 3d in the second casing 3 are chucked by respective holder pins provided in the cartridge loading and unloading mechanism with the disc cartridge consequently guided towards an inserted position deep into the cartridge receiving mouth. During the insertion of the disc cartridge and when the disc cartridge is inserted to a position adjacent respective pawls in the cartridge loading and unloading mechanism, the first casing 2 is trapped with the pawls in the cartridge loading and unloading mechanism engaged in the respective positioning stop 2e, but the second casing 3 is moved against the tension springs 5 and 11 until the access opening 2d is completely exposed to the outside of the disc cartridge. In this manner, the first and second casings 2 and 3 are separated away from each other with the disc cartridge consequently brought into the opened position. Simultaneously with the separation of the first and second casings 2 and 3 away from each other, the tension springs 11 are pulled axially outwardly by the respective belts 10, causing the shutters 8 to move to open the access openings 2k and 3j. At this time, since the information carrier disc 1 is essentially received within the first cavity 2c which is oversized relative to the second cavity 3c in the second casing 3, the information carrier disc remains within the first cavity 2c in the first casing 2 even after the disc cartridge has been brought into the opened position. On the other hand, as the first and second casings 2 and 3 are separated away from each other, the disc retainer 6 moves together with the second casing 3 then moving relative to the first casing 2 and, therefore, the pad 6a naturally disengages from the outer peripheral edge of the information carrier disc 1 thereby automatically releasing the information carrier disc. Once this happens, the information carrier disc 1 is free to rotate about its center. Thereafter, respective positioning pins in the cartridge loading and unloading mechanism are engaged into the positioning holes 2f in the first casing 2 to hold the first casing 2 at a required position. Simultaneously or substantially simultaneously therewith, the turntable and the clamper, both provided in the information read/write apparatus, approach the access opening 2d to clamp the information carrier disc 1 in coaxial relationship therewith in readiness for the drive of the information carrier disc 1 in one direction about the motor-coupled spindle. At the same time, two pairs of read/write heads of the information read/write apparatus give access to the information carrier disc 1 through the access opening 2d from opposite directions perpendicular to a plane of the information carrier disc and another two pairs of read/write heads of the information read/write apparatus give access to the information carrier disc 1 through each of the access openings 2k and 2j from opposite directions perpendicular to a plane of the information carrier disc in readiness for information reading or writing or erasure. Thus, the disc cartridge according to the third embodiment of the present invention is so designed as to accommodate the eight read/write heads. The removal of the disc cartridge once inserted deep into the cartridge receiving mouth from the latter will now be described. Simultaneously with release of the positioning of the first casing 2 using the positioning holes 2f, the information carrier disc 1 being clamped is released, allowing the turntable and the clamper to move out of and away from the access openings 2d and the read/write heads are moved out of the access openings 2k and 3j. Then, the disc cartridge is discharged in a direction counter to the direction of insertion thereof. At this time, when the chucking of the V-shaped positioning indents 3d in the second casing 3 is released, the second casing 3 is drawn close towards the first casing 2 by the action of the pulling forces of the tension springs 5 and 11 with the access opening 2d consequently concealed within the second casing 3, thereby bringing the disc cartridge into the closed position. Simultaneously therewith, the tension springs 11 are caused to restore to their original states by means of the belts 10, causing the shutters 8 to move in a direction required to close the access openings 2k and 3j completely, respectively. It is to be noted that, as the second casing 3 is pulled close towards the first casing 2, the disc retainer 6 fitted to the second casing 3 is axially driven by the compression spring 6c with the pad 6a brought into contact with the peripheral edge of the information carrier disc 1 to automatically retain the information carrier disc 1 in position inside the disc cartridge. Even after the disc cartridge has been ejected from the cartridge loading and unloading mechanism in the information read/write apparatus or the storage thereof outside the information read/write apparatus, the tension springs 5 and 11 constantly pull one of the first and second casings 2 and 3 close to the other of the first and second casings 2 and 3 and, therefore, the access opening 2d and the access openings 2d, 2k and 3j are kept concealed and, at the same time, the information carrier disc 1 is retained substantially fixedly inside the disc cartridge by the action of the disc retainer 6. Thus, in the foregoing embodiment, only one of the first and second casings 2 and 3, particularly the second casing 3, is moved close towards the other of the first and second casings 2 and 3, that is, the first casing 2, to close the disc cartridge. Therefore, the number of movable component parts necessary to permit the second casing 3 to close towards and away from the first casing 2 is considerably reduced. Also, in order to selectively open and close the disc cartridge embodying the present invention, the cartridge loading and unloading mechanism in the information read/write apparatus suffices to have the pawls serving as stoppers, making it possible to simplify the cartridge loading and unloading mechanism. Thus, the foregoing embodiment of the present invention is effective to provide the improved disc cartridge of high reliability. According to the foregoing second embodiment of the present invention, the number of the shutters used is minimized and, also the possibility of foreign matter entering the disc cartridge and that of wear of any one of the first and second casings are minimized. In other words, since when the first and second casings 2 and 3 having respective joint ends of 1 to 3 mm in thickness are jointed together in end-to-end abutted fashion when the disc cartridge is in the closed position, no gap will be formed at the joint even though one or both of the first and second casings 2 and 3 deform or warp, thereby ensuring that no foreign matter such as dust will intrude into the interior of any one of the first and second casings 2 and 3, that is, into any one of the first and second cavities 2c and 3c forming the disc chamber inside the disc cartridge. Also, no scrap of any one of the first and second casings 2 and 3 which would be formed when a shutter is employed in a disc cartridge will enter the disc chamber. Also, since the access openings 2k and 3j are automatically selectively opened and closed with the associated shutters 8 operatively associated with the relative movement of the first and second casings 2 and 3 to selectively bring the disc cartridge into the opened and closed positions, no selective opening and closing is necessary which has hitherto been accomplished by chucking the shutters by means of, for example, pawls. Attention is called that a single motion, i.e., the relative movement of the first and second casings 2 and 3, is effective to automatically drive a plurality of shutters, that is, the shutters 8. The disc cartridge of the above described construction can be utilized in an information read/write apparatus of a type employing at least one read/write heads disposed on one side of the information carrier disc or on each of the opposite sides thereof. By way of example, the information read/write apparatus employing a pair of read/write heads disposed on both sides of the information carrier disc can make use of the disc cartridge of the aforementioned construction. As compared with the information read/write apparatus operable with the prior art disc cartridge utilizing a shutter, the present invention make it possible to reduce the size, particularly, the width and the depth, of the information read/write apparatus. In particular, the information read/write apparatus operable with the disc cartridge of the present invention can have a cartridge insertion path of a length substantially equal to that employed in the information read/write apparatus operable with the prior art disc cartridge. Furthermore, since when the disc cartridge is loaded and positioned in the information read/write apparatus the second cavity 3c in the second casing 3 separate away from the information carrier disc 1, all that is necessary is to accurately position only the first casing 2 and the second casing 3 need not be accurately positioned. Moreover, the disc retainer releases the information carrier disc 1 as the first and second casings 2 and 3 are separated from each other and retains the information carrier disc 1 firmly in position inside the disc chamber automatically when the first and second casings 2 and 3 are closed together. Accordingly, the present invention merely requires the use of the disc retainer at a position distant from the information carrier disc 1 when the first and second casings 2 and 3 are separated from each other and, therefore, no connecting member is needed to associate the movement of one of the first and second casings 2 and 3 with that of the other of the first and second casings 2 and 3, thereby making it possible to reduce the number of component parts used to construct the disc cartridge. It is to be noted that, in the foregoing second embodiment of the present invention, the access opening 2d defined in the upper panel 2a of the first casing 2 was not made in the form of a hole. However, the access opening 2d defined in the upper panel 2a of the first casing 2 may be made in the form of a hole. Conversely, although in the first embodiment the access opening 2d or the centre hole 2d defined in the upper panel 2a of the first casing 2 has been made in the form of a hole in a manner similar to that in the lower panel 2b, the access opening in the upper panel 2a in the second embodiment of the present invention may not be made in the form of a hole and may be made completely open. In the case of a hole, the information carrier disc 1 can be supported more stably. In contrast thereto, in the case of the completely open type, the structure can advantageously be simplified and made inexpensive. It is also to be noted that, although in the foregoing second embodiment the use of the two shutters 8 has been made, the number of the shutters may not be always limited to two, but may be one or four. Also, instead of the use of the two pairs of the springs 5 and 11, the use of one pair of the springs 5 may be dispensed with in the practice of the second embodiment of the present invention. Conversely, while in the second embodiment of the present invention only the springs 11 have been used, the use may be made of both of the springs 5 and 11. Where only the springs 11 are employed, the structure can be made simpler and inexpensive. In contrast thereto, where the springs 5 and 11 are employed, the load which would be imposed on the belts can advantageously be lessened to avoid any possible breakage of any one of the belts 10 due to a fatigue. In any one of the foregoing embodiments of the present invention, the information carrier disc that can be accommodated within the disc cartridge of the present invention may be of any known disc, for example, a phase-variable optical disc, magneto-optical disc or convertible magnetic disc. In addition, the disc cartridge shown and described in connection with any one of the foregoing embodiments of the disc cartridge of present invention has been described as applicable to the information read/write apparatus employing a mechanical clamp system, that is, a combination of the turntable and the clamper, for holding the information carrier disc for rotation together with the motor-coupled spindle, and for this purpose, the disc cartridge has been shown having the access opening or centre hole 2d defined therein for the access of the turntable and the clamper. However, where the disc cartridge of the present invention is desired to be applied to the apparatus employing a magnet clamp system wherein a magnet is employed to clamp the information carrier disc between it and the turntable, arrangement may be such that a portion of the upper panel which may align with the clamper, that is, a portion of the upper panel corresponding to the centre of the information carrier disc, may be covered. In any one of the embodiments of the present invention, although the disc retainer 6 has been described as provided in the second casing 3, the disc retainer 6 may be disposed at any suitable location where it can selectively move close towards and away from the information carrier disc. In addition, instead of the compression spring 6b forming a part of the disc retainer 6, any suitable biasing means such as, for example, a rubber string may be employed. The disc cartridge of the present invention is operable with any type of information read/write apparatuses of a type operable with the use of an information carrier disc. Specifically, the information read/write apparatus has recently been developed which is provided with a plurality of heads on one or both sides of the information carrier disc and which is so designed and so structured that a transfer rate of the apparatus as a whole is increased by dividing or combining information and by recording or reproducing the divided or combined on or from the information carrier disc, thereby to accomplish a digital recording or reproduction of motion pictures such as a NTSC composite signal, a component signal or a high-definition signal. The information read/write apparatus has also been developed which is provided with a plurality of heads on one or both sides of the information carrier disc so that, for example, an audio signal can be digitally recorded or reproduced independently to deal with a plurality of channels independently. In view of the above, the disc cartridge of the present invention is equally applicable to any of those recently developed apparatuses.

Claims: A disc cartridge for rotatably accommodating an information carrier disc (1), comprising: a first casing (2) having a first cavity (2c) defined therein for accommodating a portion of the information carrier disc (1), said information carrier disc (1) being retained rotatably within said first cavity (2c); a second casing (3) having a second cavity (3c) defined therein for accommodating the remaining portion of the information carrier disc (1) and operatively coupled with said first casing (2) for movement relative to the first casing (2) and also to the information carrier disc (1) between extended and retracted positions to bring the disc cartridge into opened and closed positions, respectively; and at least one of said first (2) or second casing (3) having an access opening (2d) defined therein for an access of a turntable and at least one head, both provided in an information read/write apparatus, to the information carrier disc (1), said access opening (2d) being exposed to the outside when the second casing (3) is moved to the extended position relative to the first casing (2) and also to the information carrier disc (1), characterised in that the disc cartridge further comprises at least one shutter (8) operatively associated with the first casing (2) or second casing (3) and mounted on the other of said first casing (2) and said second casing (3) for movement between first and second positions, said shutter (8) being moved to the first position to open the access opening (2d) in response to the movement of the second casing to its extended position. A disc cartridge according to claim 1, further comprising at least one belt (10) provided in the first (2) or second (3) casing and operatively connecting the shutter (8) with the other of the second (3) or first (2) casings. A disc cartridge according to claim 1 or 2, further comprising a disc retainer means (6) for suppressing an arbitrary motion of the information carrier disc (1) accommodated within a disc chamber defined by the first (2c) and second (3c) cavities, said disc retainer means (6) in its entirety being movable in response to a movement of the second casing (3) to separate away from the information carrier disc (1) when said second casing (3) is brought to the extended position, but brought into engagement with the information carrier disc (1) when the second casing ( 3) is moved to the retracted position. A disc cartridge according to claim 3, wherein said disc retainer means (6) is provided inside the second casing (3). A disc cartridge according to any preceding claim, in which each of said first (2) and second ( 3) casings has at 25 least one hole (2k, 3j) defined therein for an access of at least one head, provided in an information read/write apparatus, to the information carrier disc (1), and at least one shutter (8) is mounted on each casing (2, 3) and operatively associated with the other casing (3, 2) for movement between first and second positions, each shutter (8) being moved to the first position to open each hole (2k, 3j) in response to the movement of the second casing (2) to its extended position. A disc cartridge according to claim 5, further comprising at least one belt (10) provided in the first (2) or second (3) casing and operatively connecting the shutter (8) with the other of the first and second casings (3, 2). A disc cartridge according to claim 1 or 5, further comprising a locking means including a lock pawl means (15) pivotally mounted inside the other of the first (2) and second (3) casings and engageable with said guide means (4), a biasing means (17) for urging the lock pawl means (15) towards the guide means (4), and a lock release means (16) having a portion exposed to the outside from the cavity in the other of the first and second casings and operable to press the lock pawl means (15). A disc cartridge according to any one of the preceding claims, wherein said portion of the information carrier disc (1) is constrained within said first cavity (2c) and wherein said second casing (3) is movable relative to the first casing (2) and also to the information carrier disc (1). A disc cartridge according to any one of the preceding claims, wherein the first cavity (2c) has a generally sector-shaped surface area larger than that of the second cavity (3d).

Inventors: MIYAZAKI BENICHI, NISHINO YUKIO, WAKABAYASHI KANJI, MIYAZAKI, BENICHI, NISHINO, YUKIO, WAKABAYASHI, KANJI
Applicants: MATSUSHITA ELECTRIC IND CO LTD, MATSUSHITA ELECTRIC INDUSTRIAL CO., LTD.
Application year: 1992
Main classification: G11B23
IPC codes: G11B23