Disk cartridge

Abstract: A disk cartridge has a spindle insertion hole (8) and a head insertion hole (9). A pair of projections (800,800) project inwardly from adjacent portion between the two holes (8,9). Each of the projections (800,800) has a triangle which comprises a straight side (801) extending almost perpendicularly to a lateral side of the head insertion hole and an arched side (802) forming part of edge of the spindle insertion hole (8). An almost annular projection (85) being formed on an inner wall of the case of the disk cartridge along peripheral edge of the spindle insertion hole (8) or at a position separated outwardly in radius direction of the spindle insertion hole (8) from a peripheral edge of the spindle insertion hole (8) in such a manner that opposite ends of the annular projection are extended on each of the triangle projections in arched shape. The annular protection has a small width to be opposed to a non-recording surface of the disk so as to surround the spindle insertion hole.

Description: BACKGROUND OF THE INVENTION The present invention relates to a disk cartridge for encasing a recording medium such as an optical disk or a magnetic disk. In general, a magnetic disk or an optical disk is encased in a cassette case made of two shell halves. A hole into which a spindle for rotating the disk is to be inserted is formed in the center portion of the cassette case. Adjacent to the spindle hole, a head insertion hole into which a writing/reading head is to be inserted is formed in the radial direction to traverse the recording surface of the disk. The head insertion hole is opened and closed by a shutter slidingly provided on the cassette case. The front end of the cassette case has a guide portion along which is reciprocatingly moved a slider to hold the shutter for opening and closing the head insertion hole and the spindle insertion hole. The slider is in a rectangular bar-shape and holds the bent portion of the shutter. The shutter has a pair of side plate portions extending parallel to each other from the opposite sides of the bent portion thereof in order to open and close the above two holes of the cassette case. There is provided a twist coil spring between the front portion of the slider and the cassette case for urging the shutter in the direction where the two holes are closed. As mentioned above, the opposite ends of the twist coil spring are held at the front end of the slider and at the front corner of the cassette case, respectively. However, if the disk cartridge is subjected to an impact force, e.g., when it is dropped on a floor, the twist coil spring may be disconnected from the front end of the slider and the corner of the cassette case. Further, an operation for connecting the coil spring to the slider and the cassette case is troublesome, and dust may enter the cassette case when the case is dropped to move the shutter to open the two holes of the cassette case. A reading/writing device (player) for receiving the disk cartridge has a pair of drive pins for opening and closing the shutter, and, however, neither a relational movement between the drive pins and the shutter nor a charging movement of the disk cartridge into the reading/writing device is smooth. The disk is held, at its center portion, by the spindle in a floating condition in the cassette case, and, however, the disk cannot be held stably therein. Moreover, when the disk is rotationally held, the information recording surface of the disk sometimes abuts against the inner surface of the case to cause a scratch and a damage thereonto. When the disk happens to strongly abut against the edge of the head insertion hole, the information recording surface of the disk may suffer a damage. When the peripheral edge of the disk in the case strikes against the corner of a substantially circular surrounding wall, the peripheral edge thereof may suffer a damage. In addition, there is provided a writing protection mechanism in the case for preventing old information having been already recorded on the disk from being erased by recording new information onto the disk. However, there may occur a case that some parts of the writing protection mechanism are assembled upside down in the case. EP-A-0 273 983 discloses a disk cartridge having a number of pads on the inside of the cartridge. The pads have a sticking preventing portion formed on their disk supporting surface sides. The pads are opposing a non-recording surface of the disk. EP-A-0 358 442 (according to Article 54 (3)) describes a disk cartridge having upper and lower shelf halves assembled together with each other to form a case to hold a disk therein. The case has a spindle insertion hole at its center position, into which a spindle is inserted for rotating the disk with the hub while holding the hub of the disk and has a head insertion hole formed continuously from the spindle insertion hole into which a reading/writing head is inserted. The spindle insertion hole and the head insertion hole being opened and closed by a movable shutter. A semicircular projection is formed on an inner wall of the case at the peripheral edge of the spindle insertion hole for supporting the disk. SUMMARY OF THE INVENTION It is an object of this invention to provide a disk cartridge which can hold stably a disk therein without generating a scratch or damage on the disk. This object is solved by the features of claim 1. Further embodiments are claimed in the sub-claims. BRIEF DESCRIPTION OF THE DRAWINGS In the accompanying drawings: FIG. 1 is a perspective view of a disk cartridge according to this invention; FIG. 2 is a partial perspective view of the disk cartridge when a shutter is opened; FIG. 3 is a plan view of a center portion of either the upper or lower shell half; FIG. 4 is a cross sectional view of a center portion of the disk cartridge, showing other embodiment; FIG. 5 is a cross sectional view of a center portion of the disk cartridge, showing still other embodiment; and FIG. 6 is a cross sectional view of a center portion of the disk cartridge, showing still other embodiment. DETAILED DESCRIPTION OF THE INVENTION As shown in FIGS. 1 and 2, a disk cartridge C for encasing an optical disk, has an upper and a lower shell halves 6, 7 which are assembled in alignment with each other to form a case. The center portion of the case has a spindle insertion hole 8 and a head insertion hole 9 disposed adjacent to the spindle insertion hole 8 to receive a reading/writing head (not shown) to form an opening portion of the case. In order to open and close the opening portion, a shutter 10 is provided slidably in the left and right directions on the disk cartridge C. As shown in Fig. 3, the head insertion hole 9 is provided adjacent to the spindle insertion hole 8. At two positions separated from the respective peripheries of the spindle insertion holes 8,8 of the both shell halves 6, 7 are provided two annular projections each projected toward a non-recording surface of the disk. When the disk cartridge C is transferred, the disk is stably supported by one of the annular projections 85, 85. In this case, since one of the annular projections 85 contacts the non-recording surface thereof, the quality of a recording surface thereof is maintained. The upper shell half 6 has, at its corners, a plurality of male projections each having a screw hole for receiving a fastening screw while the lower shell half 7 has a plurality of female projections formed at the positions corresponding to those of the male projections. Each female projection has a hole for receiving one of the male projections. In FIG. 4, a disk 210 accommodated in the disk cartridge C is made of synthetic resin such as polycarbonate or the like. On the side of the lower shell half 7 is provided a recording surface 210a outside of a non-recording surface 210b around the spindle insertion hole 8. The projections 85, 85 are opposed to the non-recording surface 210. Each projection 85 may have an outer layer 100 made of thermoplastic elastomer as an elastic member, which has a slippery property better than polycarbonate and is softer than that. The layer 100 and the projection 85 are formed separately through an injection molding. Further, each projection 85 has an arched shape in cross section on the side of the disk 210. Each outer layer 100 may be formed with nitrile butadiene rubber (NBR) or ethylene-propylene rubber (EPM) which is formed separately from the projections 85 so as to be engaged therewith or attached thereto by adhesive. In addition, polyacetal having a slippery property may be used as the outer layer 100. The polyacetal layer is formed separately from the projection 85 through injection molding. If the disk cartridge C is formed with polyacetal, it can obtain a good wear-resisting property, and, however, cannot obtain a good heat resistance. Accordingly, it is not desirable that the whole part of the disk cartridge C is made of polyacetal. In FIG. 4, the projection 85 is formed at a position separately from the periphery of the spindle hole 8. However, in consideration of only prevention of wear of the disk and elastic support thereof, the outer layer 100 may be formed on a conventional projection provided at the edge of the spindle insertion hole 8. That is, as shown in FIG. 5, fluoro resin (coating layer 102) may be attached to the top surface of two annular projections 101, 101 each formed adjacent to the periphery of the spindle insertion hole 8. Further, FIG. 6 shows two annular projections 110, 110 each having an intermediate layer 111 as an elastic layer made of thermoplastic elastomer with which an annular base projecting portion 112 made of polycarbonate is covered, and an outer layer 113 made of fluoro resin having a slippery property with which the intermediate layer 111 is coated. Each projection 110 has an arched shape in cross section. The intermediate layer 111 is formed separately from the base projecting portion 112. In general, a hard coating process is performed on the surface of the disk for protection of the surface while the disk is rotated. However, coating material is not attached onto the center portion of the disk because of rotational centrifugal force exerted on the coating material. Therefore, each annular projection mentioned above can prevent a non-coated surface of the disk from contacting the inner surface of the case of the disk cartridge thereby to avoid wear, damage or scratches on the disk and the case. When the spindle S is stopped to be retracted from the hub of the disk, the disk 210 continues its rotation under its inertia force. At this time, the non-recording surface 210b contacts the annular projections 85, 101, 110. However, since the projections are not only covered with the outer layers 100, 102, 113 each having a slippery property, respectively, but also formed in an arched shape in their cross section, a wear between the disk and the projections can be effectively avoided. Instead of the above annular projections, an annular film 161 made of a slippery material such as PET may be attached onto the periphery of the spindle insertion hole 8 in order to avoid generation of scratches on the disk.

Claims: A disk cartridge having upper and lower shell halves (6, 7) assembled together with each other to form a case to hold an optical disk therebetween, the case having a spindle insertion hole (8) at its center position, into which a spindle is inserted for rotating the disk, and having a head insertion hole (9) formed continuously from the spindle insertion hole (8) into which a reading/writing head is inserted, the spindle insertion hole (8) and the head insertion hole (9) being opened and dosed by a movable shutter (10), wherein an almost annular projection (85) is formed, on an inner wall of the case at a position separated outwardly in radius direction of the spindle insertion hole (8) from a peripheral edge of the spindle insertion hole (8), the annular projection (85) surrounds the spindle insertion hole (8) about an angle of considerably more than 180°. A disk cartridge according to claim 1, wherein the annular projections (85; 101; 110) are covered with an outer layer (100; 102; 111, 112, 113) having a slippery property. A disk cartridge according to claim 2, wherein the outer layer (100) is made of thermoplastic elastomer. A disk cartridge according to claim 2, wherein the outer layer (102) is made of fluoro resin. A disk cartridge according to claim 2, wherein the outer layer (100) is made of rubber material. A disk cartridge according to claim 2, wherein the outer layer (111, 112, 113) is composed of a thermoplastic elastomer layer with a fluoro resin layer. A disk cartridge according to claim 1 or 2, wherein said projection (85) has an arched shape in cross section on a side of the disk. A disk cartridge according to claim 2, wherein the outer layer (100) is formed separately from the projection (85) through an independent injection molding. A disk cartridge according to claim 2, wherein the outer layer (100) is attached on the projection (85) by an adhesive. A disk cartridge according to one of claims 1 to 9, wherein the head insertion hole (9) and the spindle insertion hole (8) have a chamfered edge. A disk cartridge according to one of claims 1 to 10, wherein the case is made of polycarbonate which is injected through a single gate at a position corresponding to as retaining plate for guiding a slide plate of the shutter (10).

Inventors: AKIYAMA NOBORU, KAMEDA KATSUMI, AKIYAMA, NOBORU, KAMEDA, KATSUMI, Akiyama, Noboru, c/o Dai Nippon Insatsu K. K., Kameda, Katsumi, c/o Dai Nippon Insatsu K. K.
Applicants: DAINIPPON PRINTING CO LTD, DAI NIPPON INSATSU KABUSHIKI KAISHA
Application year: 1991
Main classification: G11B23
IPC codes: B29C45, G11B23