A SHUTTER ASSEMBLY FOR USE IN A DISC CARTRIDGE

Abstract: In a disc cartridge comprising a cartridge case and a shutter slidably mounted on the cartridge case for opening and closing head accessing opening, the shutter comprises a first plate and a second plate opposing to the first plate, a connection member for connecting the first plate and the second plate, and projection formed on at least any one of the first and second plate of the shutter in such a manner that the projection is slanted toward the connection member.

Description: The present invention relates to a disc cartridge having a shutter for closing and opening a head insertion hole of the disc cartridge. A conventional disc cartridge having a floppy magnetic disc in the thin cartridge case is shown in Fig. 1, wherein the cartridge comprises a thin case 51 of a generally rectangular shape and made of hard synthetic resin material, a magnetic disc 52 rotatably enclosed in the case 51 and a shutter 53 slidably mounted on the case 52 so as to move along one side or front side of the case 51. In the central portion of the case 51, there are defined a circular opening 54 and a head accessing opening 55. A shallow recess 56 is defined on the top wall of the case 51 in the region near the head accessing opening 54 for sliding the shutter 53 passing the head accessing opening 55. A guide slot 57 is also defined in the top wall along the front side of the case 51 for guiding the movement of the shutter. 53. Conventionally the shutter 53 is formed of a stainless steel plate formed by a generally U shape in a side view having a pair of opposing plates 61a and 61b in each of which an opening 58 is defined with the generally same shape and size as the head accessing opening 55. A part shown by 61 adjacent to the opening 58 acts as a lid plate. Two raised members 59 are inwardly projected on one plate 61a by bending a part of the plate inwardly. The raised members 59 are adapted to be slidably fitted in the guide slot 57 of the case 51. However, since the shutter 53 is made of a metal plate and the raised members are short, it is hard for the raised members 59 to be resiliently deformed when the shutter is mounted to the case 51 fitting the raised members 59 in the guide slot 57. In order to facilitate to fit the raised members 59 into the slot 57, there is formed one or more thin portions 60 in the front edge of the case 51 through which the raised members 59 are passed causing the thin portions 60 to be bent. In order to protect the floppy disc from deformation by an external force, the case 51 is made of hard plastic resin materials. Therefore, it is difficult to give a large amount of bending to the thin portions 60 to pass the raised members 59 since the resiliency of the case 51 is insufficient. Accordingly, to elongate the raised member 59 makes it difficult to mount the shutter 53 to the case 51. To cut the raised members 59 short makes it easy to mount the shutter on the case 51 fitting the raised members 59 in the slot 57 however, the raised members 59 are easily disengaged from the slot 57, thereby resulting in easy disengagement of the shutter from the case 51. As mentioned above, control of the length of the raised members 59 must be severe. A disc cartridge comprising a shutter assembly with the features of the precharacterizing part of claim 1 is known from GB-A-2 142 766. In this disc cartridge, the shutter which is made from sheet metal comprises three projections protruding from the shutter into a guide slot of the cartridge case. The projections are formed by means of a press by invertly bending a part of the shutter. The projections are located apart from the shutter opening. Therefore, the cartridge case requires a guide slot of considerable length so that the formation of a U-shaped notch for retaining the shutter in the opening position becomes difficult. The three positions must be oriented with high precision to ensure a smooth running of the shutter. EP-A-0 137 965 describes a cartridge having a U-shaped shutter which is also made from metal sheet. This shutter does not have an access opening in the first plate and there are two projections formed from the sheet material and bent invertly to come into engagement with a guide slot of the cartridge case. An object of the present invention is to provide a disc cartridge having a shutter assembly which can be easily mounted on a cartridge case without unnecessary deformation of the cartridge case. This object is solved, according to the invention, with the features of claim 1. The disc cartridge of the present invention has a shutter assembly which can be moved smoothly preventing the guide slot portion of the cartridge from being scraped. Fig. 1 is a perspective view showing an example of a disc cartridge with a shutter disengaged, Fig. 2 is a cross sectional view showing an essential portion of the shutter mounted on the cartridge case, Fig. 3 is a perspective view showing an embodiment of a disc cartridge according to the present invention with a shutter disengaged, Fig. 4 is a partial top plan view of the disc cartridge according to the present invention, Fig. 5 is a cross sectional view taken along the lines A-A in Fig. 4, Fig. 6 is a cross sectional view taken along the lines B-B in Fig. 4, Fig. 7 is a top plan view of the shutter shown in Fig. 4, Fig. 8 is a cross sectional view taken along the lines E-E in Fig. 7, Fig. 9 is a partial top plan view of the disc cartridge according to the present invention showing a condition when no use, Fig. 10 is an enlarged cross sectional view taken along the lines C-C in Fig. 9, Fig. 11 is a cross sectional view similar to Fig. 10 with the shutter disengaged Fig. 12 is a cross sectional view taken along the lines D-D in Fig. 9, Fig. 13 is a partial cross sectional view of a part of a mold used in making the shutter, Fig. 14 is a perspective view of a shutter used in a second embodiment, Fig. 15 is a cross sectional view of a mold used for making the shutter according to the present invention, and Figs. 16 is a cross sectional view of a modification of the shutter. Referring to Figs. 3 to 13, a disc cartridge according to the present invention is mainly comprised of a cartridge case 1, a magnetic disc 2 rotatably mounted in the cartridge case 1 and a shutter 3 slidably mounted on the cartridge case 1. The cartridge case 1 comprises a first half case 1a and a second half case 1b, each being made of hard synthetic resin materials such as ABS resin, each being formed by a generally flat rectangular plate surrounded by low vertical walls in the known manner. A drive shaft insertion opening 4 is defined in the central portion of the cartridge case 1, and an elongated head accessing opening 5 is defined near the drive shaft insertion opening 4. A shallow recess 6 is defined in the front portion of each half case so as to limit the movement of the shutter 3. Said head accessing opening 2 is defined in the recess 6. A guide slot 7 is defined on each of the half case 1a and 1b near the front edge of the case 1 so as to extend in the direction of the movement of the shutter 3. In the front edge portion of the first case half 1a, thin portions 21 are formed near the front edge of the cartridge case so as to be resiliently deformed for facilitating mounting of the shutter 3 as mentioned later. The magnetic disc 2 is provided with a hub 8 which is rotatably accommodated in the drive shaft insertion opening 4 of the first case half 1a as shown in Fig. 3. Said shutter 3 is made of synthetic resin materials such as polyacetal resin or polyamid resin with a predetermined resiliency deformable easier than the cartridge case 1. The shutter 3 is formed by a first flat plate 3a, second flat plate 3b opposing in parallel with the first flat plate 3a and a connecting plate 3c for connecting both plates 3a and 3b, so that the shutter 3 is formed generally in a U character shape in a side elevational view. Each of the first plate 3a and 3b is provided with an elongated rectangular opening 9 having the same size and shape as the head accessing opening 5 and a lid member 10. The opening 9 and the lid member 10 in the first plate 3a face to the opening 9 and the lid member 10 in the first plate 3b. Two projections 11 in a form of a small plate are projected in positions near the connecting plate 3c from the first plate 3a toward the second plate 3b with a predetermined interval along the movement of the shutter 3. The projections 11 are so slanted that the free end of the projection 11 is directed toward the connecting plate 3c. It is appreciated that the projections 11 are formed with an angle not vertical relative to the first plate 3a but inclined toward the connecting plate 3c. In other words, the projections 11 are respectively slanted in the direction X (as shown in Fig. 11) of insertion of the disc case 1 into the shutter. The slanting angle ϑ of the projection 11 relative to the first plate 3a is preferably 95° to 120° and more preferably 100° to 110°. It may be said, the greater the angle ϑ, easier to mount the shutter on the disc case 1. However, in case the angle ϑ is too large, engagement of the projection 11 in the guide slot 7 may be unstable. Thus, the range of the slanting angle defined above is desired. The thickness d of the projection 11 may be selected by 0. 4 mm for example thicker than the thickness 0.35 mm of the shutter 3 so as to reinforce the projections 11. However, the thickness of the projections 11 may be thinner than 0.4 mm so as to be deformed at the time of insertion of the shutter 3 into the disc case 1. It may be said the longer the projection 11, the easier the deformation of the projection 11. Considering the above matter, the length of the projection 11 may be about 0.7 mm for the inner height L=2.8 mm between the first and second plates 3a and 3b of the shutter 3. Two through holes 12 having a rectangular shape are defined between the respective projections 11 and the most front end of the disc case 1. Another projection 13 is formed inside of the shutter at the center with respect to the distance between two plates 3a and 3b on the connecting plate 3c. A coil spring 14 is suspended between the projection 13 and a suitable position on the cartridge case 1 so that the shutter 3 is always biassed toward the closing direction to close the head accessing opening 5. Fig. 13 shows a structure of an essential portion of a mold for molding the shutter. The mold mainly comprises fixed core 17 used for forming the inner surface of the shutter 3, side cores 15 and 16 of movable mold employed for molding the outer surfaces of the first plate 3a and second plate 3b and upper core 38 for forming the outer surface of the connecting plate 3c. By these cores, there are formed spaces 20, 19 and 39 for preparing the first plate 3a, projections 11 and the second plate 3b. The molten synthetic resin materials are injected into the spaces 19, 20 and 39 under a reduced pressure, subsequently, the mold is cooled. The upper core 38 is removed in the direction X and the side cores 15 and 16 are removed in Y direction, whereby the molded shutter 3 can be taken out of the mold. The line 40 represents a separation interface of the mold. When the shutter 3 is taken out of the mold, both of the free ends of the first plate 3a and second plate 3b of the shutter 3 resiliently abut each other as shown in Fig. 8. Accordingly, in order to assemble the the shutter 3 as shown in Fig. 8 to the cartridge case 1, the free ends of the first and second plates 3a and 3b are opened as shown in Fig. 3, then the shutter 3 is inserted into the case 1 using a suitable tool (not shown). As shown in Figs. 10 and 11, there are formed the thin portions 21 at the positions corresponding to the projections 11 frontwardly of the guide slot 7 of the first half case 1a and the front end of the thin portion 21 is chamferred at 22. Thus, upon insertion of the case 1 with the chamferred portion 22 directed toward the shutter 3, the projection 11 of the shutter 3 rides on the chamferred portion 22, whereby the projection 11 is resiliently bent and gets over the thin portion 21 resulting in being engaged in the guide slot 7. As shown in the embodiment, since the projection 11 can be bent in the direction X of which is the direction of the insertion of the case 1 to the shutter 3, the projection 11 can easily gets over the thin portion 21 to engage in the guide slot 7. It is noted that after each of the projections 11 is engaged in the guide slot 7, if the shutter 3 is applied with a force in the direction to disengaging the shutter from the cartridge case 1, the shutter can be prevented from being disengaged by such action that each of the projections 11 props against the inner surface 7a of the guide slot 7 since the projection 11 is slanted toward the connecting plate 3c. In case the shutter 3 is formed of synthetic resin materials as a whole, it is possible to decrease the weight of the shutter compared to the conventional metal shutter, resulting in decreasing the total weight of the disc cartridge. In addition, if the disc cartridge is subjected to a strong shock by dropping for example, the metal shutter may be easily disengaged from the cartridge case due to a relatively heavy weight of the metal shutter. However in case the plastic resin shutter is used as in the present invention, the shutter can be prevented from being disengaged from the cartridge case due to the relatively light weight even if a shock is applied to the cartridge case 1. Referring to Figs. 14 and 15 showing another embodiment of the present invention, the shutter 3 shown in Figs. 14 and 15 is generally similar to the shutter 3 shown in the first embodiment except that there are defined a pair of openings 31 on the second plate 3b corresponding to the first openings 12 of the first plate 3a. The second openings 31 are necessary to decrease the error of the thickness between the first plate 3a and second plate 3b as mentioned hereinafter with reference to Fig. 15. A mold for molding the shutter 3 mentioned above comprises side cores 32, and 33, a fixed core 34 between the cores 32 and 33 and a upper core 35. A space 37 for making the second plate 3b is defined by the cores 32 and the fixed core 34. Another space 38 for the first plate 3a is defined by the cores 33 and 34. A further space 39 for the connecting member 3c is defined by the fixed core 34 and the upper core 35. The first openings 12 are respectively defined by the part of the side core 33 and the second openings 31 are respectively defined by the part of the side core 32. In case the shutter 3 is molded using a gate G, if the first openings 12 are defined solely on the first plate 3a without the second openings 31 on the second plate 3b, moreover the projection 11 is formed at the opening 12, there occurs a difference of the flow resistivities in the space 38 and 37, that is the flow resistance of the space 38 is greater than the space 37. In addition if the free end 34a of the core 34 is not supported, the molten resin can flow easier in the space 37 than the molten resin in the space 38, so that the side core 34 may be inclined toward the side core 33 by the pressure of the injected resin. Thus, naturally, the second plate 3b is thicker than the first plate 3a, thereby resulting in fault of the molding. In order to avoid the fault, in the embodiment, the end 34a of he fixed core 34 is clamped by the slidable side cores 32 and 33 to prevent inclination of the fixed core 34 thereby enabling the widths of the spaces 37 and 38 to be equal. By contacting the top projected portions 32a and 33a of the side cores 32 and 33 each having the same width (represented by the length of the projected portions 33a and 32a in the direction perpendicular to the paper of Fig. 20) of the projection 11 onto the fixed core 34a, the flow resistance of the molten resin in the space 37 may be made generally equal to the flow resistance in the space 38 for keeping the flow speed of the molten resin in both spaces 37 and 38 equal. By the arrangements mentioned above, it is possible to make the thickness of the first plate 3a and the second plate 3b to be equal. In other words, according to the arrangement mentioned above, the number of the inferior products of the shutter can be decreased. In the arrangement mentioned above, the second openings 31 may be defined by insertion of a part of the side core into the space 37. It is not essential to provide the thin portions 21 in the front edge portion of the disc cartridge and the slanted face 22. Although in the embodiments mentioned above, the shutter 3 is used exclusively for opening and closing the head insertion hole 5, it may be possible to use the shutter for opening and closing the head insertion hole 5 and opening 4 for insertion of the hub 8. It may be possible to make the corner between the first plate 3a and the connection member 3c resiliently deformable when the projection 11 gets over the thin portion 21 of the cartridge case 1 so as to facilitate to insert the shutter into the cartridge case 1. In order to help such resilient deformation of the shutter at the corner of the connection between the first plate and connection member, in case the openings 12 are defined on a line passing the projections 11 in the direction of insertion of the cartridge case 1 into the shutter 3, the bending strength at the corner may be decreased, so that the corner can be resilient deformed easily. These action may be assured so long as the openings 12 are respectively defined at such areas that are near the corner between the first plate and the connection member and aligned with the projections 11 in a direction of insertion of the shutter into the cartridge case. The deformation of the corner between the first plate and the connection member may be easier as the openings 12 are closer to the corner and the openings 12 are larger in particular the openings 12 are elongated in the direction of the insertion of the cartridge case 1, whereby the arrangement mentioned above is desired to insert the shutter into the cartridge case 1 with a decreased force. In particular, since the shutter 3 is made of synthetic resin materials, it is suitable since the amount of the deformation at the corner is large. A modification of the shutter for use in the disc cartridge shown in Fig. 16. In the modification of the shutter 3 shown in Fig. 16, the openings 12 are defined on both of the first plate 3a and the second plate 3b being aligned with the projection 11. It is an advantage of the present invention that the shutter can be easily inserted to the cartridge case since the projections 11 are formed of synthetic resin materials slanted in the direction of insertion of the shutter to the cartridge case. It is a further advantage that since the projections 11 of the shutter 3 are formed of synthetic resin materials, wearing of the guide slot 7 of the cartridge case and projections 11 can be prevented and the sliding resistance of the shutter against the cartridge case is decreased, thereby enabling a smooth sliding motion of the shutter. It is a further advantage that since the first opening 12 is defined being aligned with the projection 11 on the first plate and the second opening is defined on the second plate corresponding to the first opening, the first plate and the second plate of the shutter can be made with a generally thin and equal thickness, thereby assuring a smooth motion of the shutter. It is noted that the present invention may be applied not only to a disc cartridge having a magnetic recording disc but to a disc cartridge having an optical recording disc.

Claims: A disc cartridge comprising a cartridge case (1) having a head accessing opening (5), a disc (2) rotatably mounted in the cartridge case (1) and a shutter (3) slidably mounted on the cartridge case (1) for opening and closing said head accessing opening (5), the shutter (3) comprising a first plate (3a) having an opening (9) and a second plate (3b), a connection member (3c) connecting the first plate (3a) and the second plate (3b), and projections (11) provided on the first plate (3a) near the corner between the first plate and the connection member (3c) and being movable within a guide slot (7) defined on the cartridge case (1), the respective tips of the projections (11) being slanted toward the connection member (3c) so as to define through holes (12), characterized in that the shutter (3) is wholly made of a synthetic resin material, and the shutter has at least two projections (11), and through holes (12), each through hole (12) being adjacent to the, corresponding projection (11) and extending from this one up to the connection member (3c). The disc cartridge according to claim 1, wherein the angle of each of the projections (11) relative to the first plate (3a) is 95° to 120°.

Inventors: FUJITA, MINORU, KATO, YOSHITAKE, MARUYAMA, HIROSHI
Applicants: HITACHI MAXELL LTD.
Application year: 1986
Main classification: G11B23
IPC codes: G11B23