Cartridge housing formed to protect disk-shaped medium from dust-particles

A disk-shaped information memorizing medium having as small as possible a gap formed between a cartridge housing and an opening and closing door to prevent dust from entering. To this end, an opening window is provided through one plane portion of the cartridge housing opposing an information memorizing surface of an optical disk and the opening and closing door is swung along a plane of this plane portion.

BACKGROUND OF THE INVENTION
 1. Field of the Invention
 The present invention relates to a memorizing medium cartridge such as a
 disk-shaped information memorizing medium cartridge in which an
 information memorizing medium such as an optical disk, a magneto-optical
 disk and the like is accommodated in a state of rotating freely and
 particularly to a memorizing medium cartridge capable of effectively
 restraining minute dust from entering in a cartridge housing while it is
 in a state of being reserved.
 2. Description of the Related Art
 In the past, generally, as an information memorizing cartridge in whose
 housing an information memorizing medium capable of recording and/or
 reproducing information such as audio, video, computer data and the like
 is accommodated in a state of rotating freely , for example, a cartridge
 having an arrangement as shown in FIG. 1 has been known. This information
 memorizing cartridge is a disk cartridge 1 containing therein a write-once
 type magnetic disk where a user can record and write in information such
 as computer data and the like later on and has an outward appearance shape
 as shown in FIG. 1.
 That is, this disk cartridge 1 comprises a cartridge housing 2 which is
 made up of a pair of upper and lower shells 2a and 2b, and an
 magneto-optical disk 4 accommodated in a state of rotating freely in a
 disk accommodating room 3 of this cartridge housing 2 and the like. On
 both surfaces of the upper and lower of the cartridge housing 2 are
 provided upper and lower opening windows 5 extending to one side from a
 central portion and this opening window 5 is made capable of being opened
 and closed by an opening and closing door 6 which is made capable of
 sliding along its one side. Then, at a central portion of the
 magneto-optical disk 4 is provided a hub portion 7 having a center hole 7a
 which is chucked to a turntable provided on a main body side of an
 information memorizing apparatus and this hub 7 is made to oppose a
 central portion of the opening window 5.
 However, as the conventional disk cartridge having such an arrangement is
 structured such that the opening and closing door 6 is formed like a U
 letter shape to be fit in one side of the cartridge housing 2 and the
 opening window 5 is opened and closed by sliding the opening and closing
 door 6 along its one side, there has been a problem that a big gap forms
 between the cartridge housing 2 and the opening and closing door 6,
 thereby making it impossible to prevent the minute dust from intruding.
 In this case, when the dust, which has intruded in the cartridge housing 2,
 attaches itself to a surface of an information memorizing surface of the
 magneto-optical disk 4, the read-out or write-in beam is shielded and the
 information memorizing surface is damaged by the dust, thereby making it
 impossible to carry out a read/write of information normally.
 Particularly, in a case of an information memorizing device with a large
 capacity, the effect of even minute dust can not be negligible and hence,
 there is a demand for a disk cartridge capable of preventing the intrusion
 of even the minute dust.
 Further, in the above-mentioned conventional disk cartridge 1, because the
 opening and closing door 6 is located at a portion where it is easily
 touched by a user's hand, there is a fear that the user opens the opening
 window 5 by erroneously sliding the opening and closing door 6. Further,
 because the opening and closing door 6 moves linearly along one side of
 the cartridge housing 2, there is a problem that a surface area of the
 cartridge housing 2 can not be made smaller.
 Also, as another example of the conventional memorizing medium cartridge,
 for example, there is a disk cartridge as is stated in a public bulletin
 of Japanese laid-open patent publication No. 7-6493. This disk cartridge
 comprises an upper case whose remaining half is circular-shaped and a
 remaining half is square-shaped, a lower case having the same shape as
 that of the upper case, two notch portions provided in a position which
 opens by 90 degrees in the circular shaped portions of the upper and lower
 cases when viewed from a disk center, a memorizing window provided at a
 center of the two notch portions of the lower case, a swinging shutter
 which covers the notch portions and the memorizing window and is fit in
 the circular portions of the upper and lower cases and a driven roller
 provided in a position symmetrical to the notch portions relative to the
 disk center in the upper and lower cases.
 Although this disk cartridge is arranged such that the swinging shutter
 moves curvedly in the circular portion of the upper and lower cases,
 because the swinging shutter is formed in the same U letter shape as the
 above-mentioned opening and closing door 6 and this swinging shutter is so
 structured to fit in the circular portions of the upper and lower cases, a
 large gap similarly forms between the upper and lower cases and the
 swinging shutter, thereby giving birth to the problem that minute dust can
 not be prevented from intruding.
 SUMMARY OF THE INVENTION
 The present invention is implemented in view of these problems with the
 conventional disk cartridge and its object is to solve the above-mentioned
 problems by putting in place an arrangement that an opening window is
 provided on at least one plane portion of the cartridge housing as well as
 by swinging the opening and closing door along the plane of this plane
 portion to carry out a measure against the dust for reducing as small as
 possible the gap which forms between the cartridge housing and the opening
 and closing door.
 According to an aspect of the present invention, there is proposed a
 disk-shaped information memorizing medium cartridge which comprises:
 a cartridge housing in which a disk-shaped information memorizing medium
 accommodating room is formed by superposing a pair of shells;
 a disk-shaped information memorizing medium accommodated capable of
 rotating freely in the disk-shaped information memorizing medium
 accommodating room;
 an opening window formed in one shell of the pair of shells, and which
 exposes an information memorizing surface of the disk-shaped information
 memorizing medium; and
 an opening and closing door which is installed in one shell of the pair of
 shells to be capable of swinging freely and opens and closes the opening
 window by its swinging with a plane of one shell of the pair of shells as
 a guide, wherein the plane of the one shell is substantially parallel to
 the information memorizing surface of the disk-shaped information
 memorizing medium rotatabley accommodated in the disk-shaped information
 memorizing medium accommodating room.
 Since the present invention is arranged in the above-mentioned manner, the
 opening and closing door is swung along the plane of the plane portion on
 which the opening window of the cartridge housing is provided, whereby it
 is possible to reduce the gap formed between the cartridge housing and the
 opening and closing door as small as possible and to effectively restrain
 intrusion of the minute dust into the cartridge housing when it is in a
 state of being reserved.

DESCRIPTION OF THE PREFERRED EMBODIMENTS
 Hereafter, embodiments of the present invention will be explained with
 reference to the attached drawings. FIG. 2 through FIG. 11 show a first
 embodiment of the present invention in which FIG. 2 is a perspective view
 of a disk cartridge such as a disk-shaped information memorizing medium
 cartridge when looked at from a lower surface side, FIG. 3 is an exploded
 perspective view of the disk cartridge, FIG. 4 is a plan view of the disk
 cartridge when an opening and closing door is closed at a time of a lower
 shell plate being removed, FIG. 5 is a plan view of the disk cartridge
 when the opening and closing door is closed at a time of an upper shell
 being further removed, FIG. 6 is a plan view of the disk cartridge when
 the opening and closing door is opened at a time of the lower shell plate
 being removed, FIG. 7 is a plan view of the disk cartridge when the
 opening and closing door is opened at a time of the upper shell being
 further removed, FIG. 8 is an enlarged sectional view taken on line A--A
 of FIG. 4, FIG. 9 is an enlarged sectional view taken on line B--B of FIG.
 4, FIG. 10 is an enlarged sectional view taken on line C--C of FIG. 6 and
 FIG. 11 is a perspective view showing a second lock mechanism in an
 enlarged scale.
 Also, FIG. 12 through FIG. 15 show a second embodiment of the present
 invention in which FIG. 12 is a plan side sectional view of the disk
 cartridge when the opening and closing door is closed at a time of one
 shell being removed, FIG. 13 is an enlarged sectional view taken on line
 D--D of FIG. 12, FIG. 14 is a plan side sectional view of the disk
 cartridge when the opening and closing door is opened at a time of one
 shell being removed and FIG. 15 is an enlarged sectional view taken on
 line E--E of FIG. 14.
 A disk cartridge 10 pertaining to the first embodiment showing one concrete
 example of a disk-shaped information memorizing medium cartridge is one
 which uses a recording and reproducing optical disk 11 as one concrete
 example of an information memorizing medium. With a lower surface side
 being upward as shown in FIG. 2 and FIG. 3, this disk cartridge 10
 comprises a cartridge housing 12 which is formed by superposing a pair of
 an upper shell 13 and an lower shell 14, the optical disk 11 accommodated
 in a state of rotating freely in a disk accommodating room 15 formed in
 the cartridge housing 12, an opening and closing door 17 capable of
 opening and closing an opening window 16 formed in the lower shell 14 and
 the like.
 The upper shell 13 is nearly half circular shaped in its front half and
 nearly square shaped in its back half, and is made up of a plate-state
 body and in its inside is provided the disk accommodating room 15 made up
 of a circular cave-in portion. The front-half of the upper shell 13 is
 made up of, as shown in FIG. 4 through FIG. 7, a middle center arc portion
 13a provided on one side of a nearly middle portion in a width direction
 which orthogonally intersects a front to back direction and a rear center
 arc portion 13b provided on the other side of the nearly middle portion in
 the same width direction. There is an arrangement such that an arc center
 of the front-half middle center arc portion 13a of the upper shell 13 is
 set at a nearly central portion of the disk accommodating room 15 and an
 arc center of the rear center arc portion 13b is set in the neighborhood
 of a back corner portion of a back half, and a lock pin, which will be
 mentioned later, of the opening and closing door 17 is guided by the rear
 center arc portion 13b.
 Further, in the front-half center portion of the upper shell 13 is provided
 a concave portion 18 which extends from the middle center arc portion 13a
 to the rear center arc portion 13b, and a step portion 18a is set at a tip
 end portion of the concave portion 18 on a rear center arc portion 13b
 side. Then, a spring support pin 19 is provided on a middle center arc
 portion 13a side of the concave portion 18 and a pin support hole 18b is
 provided outside this spring support pin 19. Further, guide channels 20
 and 21 which play roles of positioning, preventing an erroneous insertion
 and the like upon being loaded on a disk recording and reproducing
 apparatus are provided extending in a front to rear direction on both side
 surface portions in the widewise direction of the upper shell 13.
 These guide channels 20 and 21 have one end opened respectively in the
 middle center arc portion 13a and the rear center arc portion 13b and the
 other end extended in the neighborhood of a rear portion of the rear half.
 Then, in the neighborhood of the rear portion of the guide channel 20 is
 provided a connection concave portion 22. This connection concave portion
 22 is connected to a cave-in portion 23 provided in one corner portion of
 a rear portion in the rear half of the upper shell 13. This cave-in
 portion 23 is partitioned into an outer concave portion 23a and an inside
 concave portion 23b by a partition-shaped stripe body and a protruding
 shaft 25 is projectingly provided in the inside concave portion 23b. Then,
 in the circumference of the disk accommodating room 15, a plurality of
 screws 13c are provided for screwing the lower shell 14 which is
 superposed thereon. Further, a pair of positioning holes 26 for
 positioning this disk cartridge 10 in a predetermined position of a disk
 recording and reproducing apparatus are provided in both corner portions
 of the rear portion of the rear half of the upper shell 13.
 The optical disk 11 to be accommodated in the disk accommodating room 15 of
 the upper shell 13 consists of a thin disc shaped member with a center
 hole 11a provided in the central portion, and on one surface of its plane
 portion, provided is an information memorizing surface 11b capable of
 memorizing information, which an optical head of an optical pick-up
 apparatus built in the disk recording and reproducing apparatus opposes. A
 turn table of a disk rotation driving apparatus built in the disk
 recording and reproducing apparatus is fit in the center hole 11a, and the
 optical disk 11 is chucked by the turn table and driven into rotation in
 one body.
 As for materials for this optical disk 11, for example, synthetic resin
 such as polycarbonate (PC), polyolefin and the like are suitable, but it
 is possible to use not only other synthetic resin but also various kinds
 of other materials such as glass material, aluminum alloy and the like
 other than the synthetic resin, which are used as an information
 memorizing medium.
 Also, the lower shell 14 is made up of an upper shell plate 14a and a lower
 shell plate 14b. The upper and lower shell plates 14a and 14b are of
 nearly the same shape as the upper shell 13 as shown in FIG. 3, and each
 of front halves thereof is nearly half circular shaped and each of rear
 halves thereof is made up of a plate body as a plane portion forming
 nearly a square shape. Then, middle center arc portions 27a and 27b are
 provided on one sides of nearly middle portions in front halves of the
 respective shells 14a and 14b and, rear center arc portions 28a and 28b
 are similarly provided on the other side. Then, a stopper portion 29
 protruding by a predetermined amount to the rear center arc portion from
 an edge portion of the middle center arc portion 27b is provided at a
 nearly middle portion in the front half of the lower shell plate 14b. This
 stopper portion 29 stops a lock pin of the opening and closing door 17 and
 limits its rotation amount.
 Further, opening windows 16a and 16b which correspond to each other in an
 up to down direction when they are superposed are provided in the upper
 and lower shells 14a and 14b, respectively. These opening windows 16a and
 16b are each made up of an oblong aperture state opening portion with a
 predetermined width, which extends linearly in a front to back direction
 with one end set in a nearly middle portion and the other end set in the
 neighborhood of a nearly middle portion in the front half. Then, a door
 accommodating concave portion 30 in which the opening and closing door 17
 is accommodated in a state of rotating freely is provided on one surface
 of the upper shell plate 14 in relation to the upper opening window 16a.
 This door accommodating concave portion 30 is so arranged as to correspond
 to a form in which the opening and closing window 17 swingingly shifts its
 position by a predetermined angle in order to open as well as close the
 opening windows 16a and 16b.
 Prior to explaining a form of this door accommodating concave portion 30,
 first of all, the opening and closing door 17 will be explained. This
 opening and closing door 17, as shown in FIG. 3, comprises a rectangular
 shaped shutter piece 17a capable of completely closing the opening doors
 16a and 16b, an arm piece 17b contiguous to one side of the shutter piece
 17a in a longitudinal direction and a lock nail 17c provided contiguous to
 a tip end portion of this opening and closing door 17b. In an outside edge
 portion of the shutter piece 17a is provided a lock pin 31 projecting to
 its one surface side and this lock pin 31 is made to slidably come into
 contact with the above-mentioned rear center arc portions 13b, 28a and
 28b. At an inner side of this shutter piece 17a, an arc shaped escape
 portion 17d is provided for preventing the shutter piece 17a from
 overlapping with the opening windows 16a and 16b when the opening windows
 16a and 16b are in a state of being opened.
 Further, the arm piece 17b of the opening and closing door 17 is provided
 by being extended in a direction which forms a diagonal line to the corner
 portion whereat the lock pin 31 of the shutter piece 17a is fixed. Then,
 as shown in FIG. 11, at a tip end portion of the arm piece 17, its one
 part is bent down forward to form a spring receiving tab 17e, and at a
 position a little returning toward the shutter piece 17a side from the
 spring receiving tab 17e of the arm piece 17b, a swinging hole 17f, which
 is a center of a swinging operation of the opening and closing door 17, is
 provided. The projecting shaft 25 of the upper shell 13 is fit in this
 swinging hole 17f capable of swinging freely. Also, the lock nail 17c of
 the opening and closing door 17 is made up of a U letter shaped member
 having nail tabs in a front to back direction, and a position of the lock
 nail 17c in terms of height is adjusted by providing a step portion 17g
 between the tip portion of the arm piece 17b and the lock nail 17c.
 The door accommodating concave portion 30 in which the opening and closing
 door 17 having such the form is accommodated comprises a shutter moving
 portion 30a forming nearly a fan shape corresponding to a moving
 configuration of the shutter piece 17a and an arm moving portion 30b
 allowing the moving of the arm piece 17b. A concave portion side edge 32a
 positioned on one side of the shutter moving portion 30a of this door
 accommodating concave portion 30 extends straight in a front to back
 direction with a predetermined distance from one side edge of the opening
 window 16a. Then, as shown in FIG. 4 and FIG. 5, when one side edge of the
 opening and closing door 17 is in contact with the concave portion side
 edge 32a, the opening widows 16a and 16b are completely closed by the
 shutter piece 17a.
 Also, a concave portion side edge 32b positioned on the other side of the
 shutter moving portion 30a of the door accommodating concave portion 30 is
 so set as to slantly extend in a forward direction from a position which
 is swung by a predetermined angle from the other side edge of the opening
 window 16a. As a result, as shown in FIG. 6 and FIG. 7, when the other
 side edge of the opening and closing door 17 is in contact with the
 concave portion side edge 32b, the shutter piece 17a having the escape
 portion 17d can completely open the opening window 16a and 16b.
 Further, in a corner portion opposing in a diagonal direction the rear
 portion center arc portion 28a of the arm moving portion 30b of the door
 accommodating concave portion 30, a first opening aperture 33 to expose a
 part of the cave-in portion 23 and a second opening aperture 34 which is
 set at an outside of a widewise direction of this first opening aperture
 34 are provided. The second aperture 34 is to expose a part of an elastic
 member, which will be explained later and is so formed as to correspond to
 the connection concave portion 22 of the upper shell 14a. Then, on a front
 side of the second opening aperture 34 of the upper shell 14a, a block
 portion 35 projecting toward the upper shell 13 side is provided. This
 block portion 35 is fit in a part of the outer concave portion 23a of the
 upper shell 13 and as a result, it is possible to carry out an approximate
 positioning of the upper shell plate 14a relative to the upper shell 13.
 On an outside of the door accommodating concave portion of this upper shell
 13 are provided a plurality of positioning fit-in holes 36 and respective
 fit-in holes 36 are set respectively at positions corresponding to screw
 holes 13c of the upper shell 13. Then, a plurality of fit-in convex
 portions 37, which are to be fit in these fit-in holes 36, are provided by
 the same number on the inner surface of the lower shell plate 14b. By only
 fitting the fit-in convex portions 37 in the fit-in holes 36 and
 superposing the upper and lower shells plates 14a and 14b, positioning of
 both the shell plates 14a and 14b can be carried out. Then, by engaging
 its tip portion in screw portion 13c after inserting a shaft portion of
 set screws through these, it becomes possible to make up the cartridge
 housing 12 by integrally assembling the upper and lower shells 13 and 14.
 Further, in the neighborhood of both the corner portions in the rear half
 of the upper shell plate 14a, a pair of positioning holes 38 for
 positioning the disk cartridge 10 at a predetermined position in the disk
 recording and reproducing apparatus are provided. Then, in the
 neighborhood of one positioning hole 38, a projection 39 fit in the
 central portion of the projecting shaft 25 which has penetrated the first
 opening hole 33 is provided.
 Also, in the concave portion 18 of the upper shell 13 is installed a lock
 arm 40 capable of swinging freely. This lock arm 40 comprises: a rod
 shaped arm main body 40a, a lock nail 40b provided at one end in a
 longitudinal direction of this arm main body 40a and a swinging pin 40c
 which is provided on an opposite side of the lock nail 40b of the arm main
 body 40a and at the same time, its both ends project sideward. Then, one
 end of the swinging pin 40c is fit in the pin supporting hole 18b of the
 upper shell 13 capable of swinging freely and the other end thereof is fit
 in the pin supporting hole 18b provided in the upper shell plate 14a
 capable of swinging freely, whereby the lock arm 40 is pivotally supported
 in the cartridge housing 12 capable of swinging freely.
 One end of a torsion spring 41 showing one concrete example of the elastic
 body is urged toward the inner surface of the lock arm 40. A coil portion
 of this torsion spring 41 is loosely fit in the spring supporting pin 19
 and the other end thereof is urged toward a bottom surface of the terraced
 portion 18. The lock nail 40b of the lock arm 40 is always urged toward
 the terraced portion 18 by a spring force of the torsion spring 41. A
 first lock mechanism for locking the opening and closing door 17 is made
 up of this lock arm 40 and the torsion spring 41.
 Also, in the outer concave portion 23a of the upper shell 13 is
 accommodated a plate spring body 43 showing one example of the elastic
 member. This plate spring body 43, as enlargedly shown in FIG. 11,
 comprises; a thin and long spring main body 43a, an elastic piece 43b
 which is formed by bending a little one longitudinal end portion of the
 spring main body 43a toward a surface direction, and a lock tab 44 and an
 input tab 45 which are formed so as to stand upright in the same direction
 by bending in a widewise direction both end edges on a side opposite to
 the elastic tab 43b of the spring main body 43a.
 The lock tab 44 of this spring main body 43a is provided with a notch 44a
 reaching a bottom portion of the spring main body 43a and an engagingly
 stopping tab 44b is set at an outside of the lock tab 44 by the notch 44a.
 An elastic tab 43b side of the lock tab 44 is made an inclining surface
 and along the inclining surface, the lock nail 17c of the opening and
 closing door 17 moves to a surface direction of the optical disk 11,
 thereby making it possible to take a locked state shown in FIG. 4, FIG. 11
 and the like as well as an unlocked state shown in FIG. 6 and the like.
 Also, the input tab 45 of the plate spring body 43 is formed like a L
 letter shape in cross-section and on its upper surface is provided with an
 inclining plane 45a gradually descending forward toward the elastic tab
 43b side. This input tab 45 is supposed to become an input portion for
 mounting and demounting of the lock nail 17c by the lock tab 44 by
 elastically deforming the plate spring body 43, and an operating pin 48
 provided in the disk recording and reproducing apparatus slides on the
 inclining plane 45a. By this, an engagingly stopping tab 44b side of the
 spring main body 43a is pushed downward with a result that the lock tab 44
 escapes downward, thereby releasing locking of the lock nail 17c. A second
 lock mechanism for locking the opening and closing door 17 is made up of
 this plate spring body 43.
 The opening and closing door 17, which is doubly locked by the first and
 second lock mechanisms in this manner, is always urged toward a direction
 to close the opening windows 16a and 16b by the torsion spring 46 showing
 one example of an elastic body loosely fit in the projecting shaft 25
 which is loosely inserted through its swinging hole 17f. One end of this
 torsion spring 46 is made to be seated on an inner surface of the inner
 concave portion 23b and the other end is engagingly stopped by the spring
 receiving tab 17e of the opening and closing door 17. Therefore, when an
 external force acting on the opening and closing door 17 is only a spring
 force by the torsion spring 46, the lock nail 17c climbs over the lock tab
 44 to enter into the notch 44a by the spring force and its one nail
 portion becomes a state of being in contact with an inner edge of the
 engagingly stopping portion 44b.
 Meanwhile, as for materials for the upper shell 13 and the upward lower
 shell plate 14a and the downward lower shell plate 14b, for example, ABS
 resin (acrylonitrile.multidot.butadien.multidot.styrene resin) is
 suitable, but other synthetic resin such as HIPS (high impact proof
 polystrene), PP (polypropylene) and the like can be used. Further, as
 materials for the opening and closing door 17 and the plate spring body
 43, for example, a stainless steel plate and the like are suitable, but
 other metal-made plate materials can naturally be applied and further,
 synthetic resin such as HIPS or the like is also used.
 Before the disk cartridge 10 having the above-mentioned arrangement is
 installed in the disk recording and reproducing apparatus, disk cartridge
 is placed in a state as shown in FIG. 4 and FIG. 5. That is, the opening
 and closing door 17 is in a state of completely closing the opening
 windows 16a and 16b with the spring force of the torsion spring 46, and
 the opening and closing door 17 is in a state of being immovably locked by
 the first and the second lock mechanisms.
 By inserting the disk cartridge 10 in such a state in the disk recording
 and reproducing apparatus, locked states of the first and second locking
 mechanisms are released by the first and second locking mechanisms
 provided in the disk recording and reproducing apparatus and thereafter,
 the opening windows 16a and 16b are opened by swinging the opening and
 closing door 17 by a door opening mechanism.
 First of all, when the disk cartridge 10 is inserted in the disk recording
 and reproducing apparatus, a locked state of a first lock releasing
 mechanism is released by a first lock releasing mechanism. This first lock
 releasing mechanism is, for example, arranged by having an arm member to
 outwardly swing the lock arm 40, and by swinging the lock arm 40 from the
 state shown in FIG. 4 and FIG. 5 in an anti-clockwise direction by its arm
 member against the spring force of the torsion spring 41, the lock nail
 40b of the lock arm 40 moves away from the lock pin 31 of the opening and
 closing door 17, thereby releasing the locked state by the first locking
 mechanism.
 Concurrently with or before and after this, the second lock releasing
 mechanism releases the locked state by the second lock mechanism. This
 second lock releasing mechanism is, for example, supposed to have an
 arrangement in which to have the above-mentioned operating pin 48 and is
 brought into operation with this operation pin 48 entering into the guide
 channel 20 provided on one side of the disk cartridge 10. When this
 operating pin 48 enters into the guide channel 20 and rides on the
 inclining plane 45a of the input tab 45, because, until then, both ends of
 the plate spring body 43 are in a state of having been lifted up by being
 supported at three points by the action of an electric tape 43b of the
 plate spring body 43, the lock tab 44 side of the plate spring body 43 is
 elastically deformed downward by an insertion force of the operating pin
 48 in FIG. 11. As a result, the lock tab 44 slips out downward from
 between the lock nails 17c, thereby releasing the locked state by the
 first locking mechanism.
 As a result, two locked states of the opening and closing door 17 are
 released, but because the opening and closing door 17 is urged in a
 direction to close the opening windows 16a and 16b by the torsion spring
 46, the opening and closing door 17 can not be moved in this situation.
 Then, next, the opening and closing door 17 is swung by a door opening
 mechanism. This door opening mechanism is, for example, arranged by
 comprising a pressuring-down member capable of moving the opening and
 closing door 17 by pressuring down the lock pin 31 against the spring
 force of the torsion spring 46. Then, by pressuring down the lock pin 31
 by the pressuring-down member of this door opening mechanism and by
 swinging the opening and closing door 17 from a state as shown in FIG. 4
 and FIG. 5 to a state as shown in FIG. 6 and FIG. 7, the opening windows
 16a and 16b are completely opened.
 Contrary to this, when the disk cartridge 10 is taken out from the disk
 recording and reproducing apparatus, the above-mentioned first and second
 lock releasing mechanisms and the door opening mechanism act together in a
 converse direction, thereby automatically swinging the opening and closing
 door 17 in the inverse direction, and the opening windows 16a and 16b are
 closed with this opening and closing door 17. That is, for example, when
 the pressing force of the lock pin 31 is released by the pressuring-down
 member of the door opening mechanism and is put in a free state, the
 opening and closing door 17 swings to shift its position from the state as
 shown in FIG. 6 and FIG. 7 to the state as shown in FIG. 4 and FIG. 5 by
 the spring force of the torsion spring 41 which acts on the arm tab 17b,
 and a former state in which the opening windows 16a and 16b are closed is
 restored.
 When the operating pin 48 of the second lock releasing mechanism retreats
 in a link motion with this, because the plate spring body 43 has an
 elastic deformation released and reverts to a former state, its lock tab
 44 enters into the lock nails 17c of the opening and closing door 17. As a
 result, a first stair locked state of the opening and closing door 17 by
 the first lock releasing mechanism is secured. In the same way as this,
 the lock arm 40 is returned to a former state by the spring force of the
 torsion spring 41 as regulation of the lock arm 40 by the arm member of
 the first lock releasing mechanism is released. As a result, the lock nail
 40b of the lock arm 40 is engaged with the lock pin 31, which makes it
 possible to secure a second step locked state of the opening and closing
 door 17 by the first locking mechanism.
 In this manner, according to the disk cartridge 10 concerning the first
 embodiment, because the opening and closing door 17 is so structured to be
 swung along a plane of-the plane portion by placing the opening and
 closing door 17 between the upper and lower shell plates 14a and 14b of
 the lower shell 14 in which the opening windows 16a and 16b of the
 cartridge housing 12 are provided, it became possible to reduce as much as
 possible the gap formed between the cartridge housing 12 and the opening
 and closing door 17. Therefore, it became possible to effectively restrain
 minute dust from entering into the cartridge housing through the gap
 between the cartridge housing 12 and the opening and closing door 17.
 Further, it is possible to beforehand prevent an accident in which a user
 erroneously opens the opening and closing door 17 as the opening and
 closing door 17 is accommodated in the lower shell 14. And further,
 because there are provided dual lock mechanisms in the opening and closing
 door 17, it is possible to surely prevent an accident in which a user
 erroneously opens the opening and closing door 17.
 A disk cartridge 50 according to a second embodiment of the present
 invention is, as shown in FIG. 12 through FIG. 15, one in which an opening
 and closing door 57 is exposed outside a cartridge housing 52. This disk
 cartridge 50 comprises: a cartridge housing 52 which is arranged by
 superposing a pair of an upper shell 53 and a lower shell 54, an optical
 disk 51 which is accommodated capable of rotating freely in a disk
 accommodating room 55 formed in this cartridge housing 52, the opening and
 closing door 57 capable of opening and closing an opening window 56 formed
 in the lower shell 54 and the like.
 The upper shell 53 is made up of a plate shape body comparatively thin in
 thickness with a front half being of a semi-circular shape and a rear half
 being of a square shape, and a screw shaft portion 58 projecting downward
 is provided nearly in the middle portion of its inside face. Also, the
 lower shell 54 is made up of a plate shape body as a plane portion having
 an appropriate thickness with a front half similarly being of a
 semi-circular shape and a rear half being of a square shape, and a disk
 accommodating room 55 consisting of a circular shaped concave portion is
 provided on its inside face. Then, guide channels 60 and 61, which play a
 role of positioning when it is loaded on the disk recording and
 reproducing apparatus and of preventing erroneous insertion and the like,
 are provided on both side portions in a widewise direction of the lower
 shell 54 extending in a front to back direction.
 Further, a circular channel 59 concentric with this disk accommodating room
 55 is provided outside the disk accommodating room 55 of the lower shell
 54. This circular channel 59 is so set as to start in the neighborhood of
 one guide channel 60 and to cover nearly 3/4 of a circumference of the
 disk accommodating room 55 and an arm accommodating concave portion 63 in
 which an engagingly stopping arm 62 showing one concrete example of an
 engagingly stopping member is accommodated capable of swinging freely is
 contiguously connected to its starting edge portion. A supporting pin 63a
 is projectingly provided in this arm accommodating concave portion 63 and
 a base end of the engagingly stopping arm 62 is supported by this
 supporting pin 63a capable of swinging freely.
 The engagingly stopping arm 62 comprises: an engagingly stopping nail 62a
 provided at its tip end and an input projection 62b which is set between
 this engagingly stopping nail 62a and a hole for the supporting hole 63a.
 The engagingly stopping nail 62a and the input projection 62b of the
 engagingly stopping arm 62 are projected in the same direction and are
 always urged toward the guide channel 60 side by a torsion spring 64
 showing a concrete example of an elastic body. That is, a coil portion of
 the torsion spring 64 is loosely fit around the supporting pin 63a with
 one end being engagingly stopped by a spring receiving tab 63b in the arm
 accommodating concave portion 63 and the other end being seated on the
 engagingly stopping arm 62. This engagingly stopping arm 62 is set such
 that the engagingly stopping nail 62a and the input projection 62b face a
 continuously connection opening 65 which continuously connects the guide
 channel 60 with the arm accommodating concave portion 63. Then, there is a
 setting such that the input projection 62b projects into the guide channel
 60 by a spring force of the torsion spring 64 while the engagingly
 stopping nail 62a is accommodated in the arm accommodating concave portion
 63.
 A ribbon shaped lock band 66 is accommodated capable of sliding freely in
 the circle channel 59 so that one end of the engagingly stopping arm 62
 faces the engagingly stopping nail 62a. At one end in a longitudinal
 direction of this lock band 66, an engagingly stopping hole by which the
 engagingly stopping nail 62a is engagingly stopped capable of being
 mounted and demounted is opened, and in a nearly middle portion of a front
 half of the lower shell 54 which is an on-the-way portion in a
 longitudinal direction, the opening and closing door 57 is integrally
 fixed. A third locking mechanism for locking the opening and closing door
 57 at a time of the opening window 56 being in a closed state is made up
 of this lock band 66, the torsion spring 64 and the engagingly stopping
 arm 62.
 Also, in the front half of lower shell 54 opposing the fixed portion of the
 lock band 66 and the opening and closing door 57 is provided an operating
 concave portion 67 for carrying out swinging operation of the opening and
 closing door 57. This operating concave portion 67 is extended long in a
 lateral direction from a nearly middle portion of the front half of the
 lower half 54 to a portion reaching the other guide channel 61, and a
 notch portion 67a where the opening and closing door 57 passes capable of
 sliding freely is provided in a projected stripe opposing this, which is
 set between the disk accommodating room 55 and the circle channel 59.
 Further, a hub hole 68 is opened in a central portion of the disk
 accommodating room 55 in the middle or the substantial center of the lower
 shell 54 and the opening window 56 which extends forward succeeding this
 hub hole 68 and nearly reaches the middle portion of the front half is
 provided. This opening window 56 and the hub hole 68 are made to be freely
 opened and closed by the opening and closing door 57 mounted on the lower
 shell 54.
 This opening and closing door 57 is cross-sectionally U letter shaped and
 comprises a shutter piece 57a for opening and closing the opening window
 56 and the hub hole 68, a peripheral tab 57b succeeding a peripheral edge
 of the shutter 57a and a base piece 57c which is so provided as to succeed
 the peripheral tab 57b and oppose the shutter piece 57a. At the base end
 of the shutter piece 57a of the opening and closing door 57 is provided a
 inserting hole 57d, and a part of the peripheral tab 57b is swelled so
 that a finger and the like can easily catch it. The base piece 57c of the
 opening and closing door 57 is disposed along an inner surface of the
 upper shell 53, and an operating pin 70 which projects to a shutter piece
 side is integrally provided in an inner peripheral end thereof.
 Also, the optical disk 51 accommodated in the disk accommodating room 55 of
 the cartridge 52 comprises a disk portion 51a having a nut hole 71 at its
 center portion and a tube shaft portion 51b provided at the center portion
 on one surface of the optical disk portion 51a. The tube shaft portion 51b
 penetrates through the hub hole 68 of the lower shell 54 and the inserting
 hole 57d of the opening and closing door 57 to project to a lower surface
 side. Then, the shutter piece 57a is prevented from coming off by a ring
 shaped stopping ring 72 fixed at a tip end portion of the tube shaft
 portion 51b. Further, a nut member 73 is loosely fit in the nut hole 71
 and a screw shaft portion 58 of the upper shell 53 is engaged with a screw
 portion provided on an inner peripheral surface thereof.
 This nut member 73 comprises a head portion 73a for preventing itself from
 coming off the nut hole 71 and a slit 73b provided on an outer peripheral
 surface extending in parallel with the center of the screw hole. The
 operating pin 70 of the opening and closing door 57 is slidably inserted
 into the slit 73b of the nut member 73. Then, a chucking plate 74
 consisting of an iron plate and the like for being installed on a
 turntable is fit in an inside of the tube shaft portion 51b covering the
 head portion 73a side of the nut member 73.
 As for the materials of this optical disk 51, as similar to the case in the
 above-mentioned first embodiment, polycarbonate (PC) and the like are
 suitable, but it is possible to use not only other synthetic resin but
 also various kinds of other materials such as glass material, aluminum
 alloy and the like other than the synthetic resin. Also, as for the
 materials of the upper and lower shells 53 and 54, synthetic resin such as
 ABC resin, HIPS and the like are similarly suitable, but it is possible to
 use other synthetic resin but also other materials such as aluminum alloy
 and the like. Further, as for the materials of the opening and closing
 door 57, for example, stainless steel with excellent resistance to
 corrosion is suitable, but it goes without saying that not only aluminum
 alloy and the like but also synthetic resin can be used.
 According to the disk cartridge 50 having such the arrangement, as shown in
 FIG. 12 and FIG. 13, when the opening window 56 is closed by the opening
 and closing door 57, the nut member 73 is pulled in an upward direction
 and the optical disk 51 is in a state of having been lifted. Therefore,
 the shutter piece 57a of the opening and closing door 57 is lifted by the
 tube shaft portion 51b of the optical disk 51 and the shutter piece 57a
 becomes a state of being placed in pressured contact with a lower surface
 of the lower shell 54. As a result, the gap between the shutter piece 57a
 and the lower shell 54 is made as small as possible, thereby making it
 possible to effectively restrain the minute dust from entering. Further,
 because the opening and closing door 57 is locked by the third locking
 mechanism, it is possible to beforehand prevent an accident in which a
 user erroneously opens the opening and closing door 57.
 When the operation pin enters into one guide channel 60 and pushes down
 with pressure the input projection 62b of the engagingly stopping arm 62
 by installing the disk cartridge 50 in the disk recording and reproducing
 apparatus while the opening and closing door 57 is in a state of being
 closed, the engagingly stopping arm 62 is pushed back toward the inside
 against the spring force of the torsion spring 64. As a result, the
 engagingly stopping nail 62a of the engagingly stopping arm 62 retreats
 inside and gets out of the engagingly stopping hole of the lock band 66,
 thereby releasing the lock by the third locking mechanism.
 Then, when the opening and closing door 57 is swung into an opened state as
 shown in FIG. 14 from a closed state shown in FIG. 12 by operating the
 door opening mechanism, the opening window 56 is completely opened. Then,
 the operating pin 70 provided in the base piece 57c integrally swings
 according to the swing of the opening and closing door 57, thereby
 swinging the nut member 73 by the same angle. Compared with this, because
 the screw shaft portion 58 with which the nut member 73 is engaged is
 integrated with the upper shell 53, when the nut member 73 swings, the nut
 member 73 itself is guided by the operating pin 70 and relatively moves in
 a downward direction. As a result, with a descending action of the nut
 member 73, the optical disk 51 supported by its head portion 73a descends
 under its own weight by a descending amount of the nut member 73 and
 changes into a state as shown in FIG. 15.
 In this state, the optical disk 51 is chucked by raising a turntable on the
 disk recording and reproducing apparatus side or the like. As a result,
 the optical disk 51 is integrated with the turn table in terms of a
 rotating direction, thereby making it possible to write (recording) and
 read out (reproducing) an information signal in and from the optical disk
 51.
 Contrary to this, when the disk cartridge 50 is taken out of the disk
 recording and reproducing apparatus, an opposite operation of the
 above-mentioned operation is carried out. Then, the opening and closing
 door 57 is swung in an opposite direction and the disk cartridge 50
 changes from a state as shown in FIG. 14 and FIG. 15 to a state as shown
 in FIG. 12 and FIG. 13.
 The same effect by the disk cartridge 10 concerning the first embodiment is
 obtained by the disk cartridge 50 according to the second embodiment.
 Explanations have been made up to this point, but the -present invention is
 not limited to the above-mentioned embodiments. For example, in the
 above-mentioned embodiments, an example of using the optical disk as an
 information memorizing medium has been explained, but the present
 invention can be applied to magnetic disks such as an magneto-optical
 disk, a floppy disk and the like and other various kinds of information
 memorizing media. Further, in the above-mentioned embodiments, the example
 in which the present invention is applied to the dual purpose recording
 and reproducing disk recording and reproducing apparatus as an information
 memorizing medium has been given, but needless to say, the present
 invention can be applied to a disk memory apparatus capable of only either
 of recording and reproducing.
 Also, in the above-mentioned embodiments, explanations have been made about
 the examples in which the opening windows 16 and 56 are provided in
 respective one plane portions of the cartridge housings 12 and 52, but the
 cartridge housing can be structured such that access can be simultaneously
 made from top and bottom of the cartridge housing by boring opening
 windows on plane portions of both surfaces. Further, the use of the
 torsion spring as an elastic body has been explained, but needles to say,
 it is possible to use not only plate spring and other spring materials but
 also rubber state elastic bodies such as rubber or synthetic resin akin to
 this and the like. In this manner, the present invention can be subjected
 to various changes within a range of departing its gist.
 As have been explained in the above, according to the present invention,
 because there is provided the arrangement in which the opening and closing
 door is swung along a plane of the plane portion of the cartridge housing,
 it is possible to reduce the gap between the opening and closing door and
 the cartridge housing as small as possible, and hence, it is possible to
 effectively restrain the minute dust from entering into the cartridge
 housing through the gap between the cartridge housing and the opening and
 closing door. Further, because the opening and closing door is locked by
 the locking mechanism when the opening windows are closed, such an effect
 can be obtained that an occurrence of an accident in which a user
 erroneously opens the opening and closing door can be beforehand
 prevented.
 Having described preferred embodiments of the present invention with
 reference to the accompanying drawings, it is to be understood that the
 present invention is not limited to the above-mentioned embodiments and
 that various changes and modifications can be effected therein by one
 skilled in the art without departing from the spirit or scope of the
 present invention as defined in the appended claims.