Disk cartridge with shutter and stock roll therefor

Abstract: A disk cartridge is formed with a slidably mounted metallic shutter (11) for opening and closing a disk access opening formed in a cartridge shell. A stock roll material for forming the shutter is formed of a sheet of metallic base material (2), such as aluminium, to which upper (3) and lower (4) film layers are applied. The upper film layer (3) is formed of synthetic resin including a lubricant component and a colouring agent while the lower film layer (4) is formed of a synthetic resin which is harder than that of the first film layer (3) and to which no lubricant or colouring is added. The stock material is introduced to punching and bending processing apparatus (301) such that the upper lubricant containing film layer contacts the punch die (302) such that press oil need not be used during fabrication. Bending processing is carried out such that a U-shaped shutter (11) is formed having the lubricant containing film layer (3) at an inner surface thereof, and the harder lower film layer (4) forms the outer surface. Thus, the outer surface resists abrasion and flawing and may be printed upon with good results, while the inner lubricated layer ensures smooth sliding of the shutter (11) and eliminates the need for applying and removing press oil during manufacture. The colour applied to the lubricated film layer (3) ensures that the stock may always be correctly oriented at the initial stage of processing.

Description: The invention relates to disk cartridges. More specifically, the invention relates to a stock roll for facilitating manufacture of a shutter for a disk cartridge which rotatably houses therein a disk media for storage or retrieval of computer data or the like. Disk cartridges for storage and retrieval of computer data and the like, such as a 3.5 inch floppy disk cartridge, for example, are well known. A typical structure for such a disk cartridge may be such as shown in Fig. 1 of the accompanying drawings which shows a perspective view of a disk cartridge structure including a metallic shutter 105. As may be seen, the disk cartridge 101 includes a rotatable disk 102 formed, for example, of a magnetic recording media, and a disk shell 103 formed with a disk access opening 104 over which the shutter 105 is slideably mounted. The shutter 105 is substantially U-shaped and includes side portions 106, 107 connected at one end by an edge portion 110 at first and second perpendicular bends 108, 109. As may be seen in the drawing, such a disk cartridge includes a metallic shutter portion slideably mounted on the cartridge casing for opening and closing an opening for accessing the disk surface. Such a shutter portion may be formed of stainless steel, aluminium with alumite treatment or aluminium coated with a synthetic resin in place of alumite treatment. When a stock roll of such material is processed through a punch press for manufacturing shutter portions for disk cartridges, press oil is applied to an upper surface thereof for facilitating suitable 'bite' of an upper die for forming the shutters such that the material of the stock roll is sheared to form a punched plate. After punch processing of the stock roll material, the punched stock is subjected to bending processing to form the final U-shaped structure of the disk cartridge shutter. However, during manufacture of disk cartridge shutters according to the above process, several drawbacks are encountered. First, stainless steel shutters mean that a disk weight cannot be reduced beyond a certain degree, thwarting manufacturers' efforts to provide as lightweight a product as possible. In the case of aluminium shutters with alumite treatment, a disk weight can be favorably reduced; however, costs for producing the shutters are raised significantly. Further, when aluminium coated with synthetic resin is substituted for aluminium with alumite treatment the cost of the stock roll may be reduced; however, such material requires that press oil be used for assuring clean results during processing. Consequently, it becomes necessary to clean residue left from the press oil after punching. Thus, costs are again raised and processing steps are increased. It has been considered to provide a lubricant within the synthetic resin layer for allowing resin coated aluminium to be utilized without the need of applying press oil; however, the strength of such a resin layer is reduced and becomes more susceptible to flaws during processing. Also, printability of such a lubricant impregnated resin layer is unsuitable from a manufacturers' standpoint. EP-A-0459743 discloses a disk cartridge which includes a shutter having a sliding surface coated with a material with a low coefficient of friction. EP-A-0524824 discloses a disk cartridge shutter which includes an inner layer defining a sliding surface that is formed of a material with a low coefficient of friction. EP-A-0497560 discloses a process for forming a composite film on an aluminium plate which provides for improved formability of the aluminium plate. According to one aspect of the invention, there is provided a stock roll material for forming disk cartridge shutters, comprising: a sheet of a metallic base material; a first film layer of a thickness of approximately 1 µm applied on one major surface of said sheet, said first film layer comprising a granular wax having a grain diameter of substantially 1 µm uniformly dispersed in a urethane resin evenly applied and processed by heat hardening; and a second film layer of a thickness of approximately 2 µm applied on the other major surface of said sheet, said second film layer having a surface hardness greater than that of said first film layer and comprising an epoxy resin processed by heat hardening. According to another aspect of the invention, there is provided a method of forming a shutter for a disk cartridge, comprising the steps of: applying a first film layer of a thickness of approximately 1 µm to one major surface of a sheet of a metallic base material, said first film layer comprising a granular wax having a grain of diameter of substantially 1 µm uniformly dispersed in a urethane resin evenly applied and processed by heat hardening; applying a second film layer of a thickness of approximately 2 µm to the other major surface of said sheet, said second film layer having a surface hardness greater than that of said first film layer and comprising an epoxy resin processed by heat hardening; punch processing said sheet including said first and second film layers by introducing said sheet to a punching apparatus for forming a punched plate, said sheet being oriented such that said first film layer faces a punching member of said punching apparatus so as to lubricate a contact surface of said sheet during such punch processing; and bending said punched plate using a bending apparatus to form a U-shaped shutter, said punched plate being arranged at said bending apparatus such that said first film layer forms an inner surface of said shutter and said second film layer forms an outer surface of said shutter. According to a further aspect of the invention, there is provided a disk cartridge including a slideable shutter, comprising: a cartridge casing including an upper shell and a lower shell, said upper and lower shells including recessed areas and disk access openings within said recessed areas; a disk formed of a recording medium material rotatably mounted between said upper and lower shells; upper and lower liner portions interposed respectively between upper and lower surfaces of said disk and inner surfaces of said upper and lower shells; and a shutter slideably mounted astride said upper and lower shells within said recessed areas, said shutter having windows on each side thereof which in one position correspond to said disk access openings in said upper and lower shells and expose upper and lower surfaces of said disk for effecting reading or writing operations from or to said disk, wherein said shutter comprises a U-shaped sheet of a metallic base material, a first film layer of a thickness of approximately 1 µm applied on an inner surface of said sheet, said first film layer comprising a granular wax having a grain diameter of substantially 1 µm uniformly dispersed in a urethane resin evenly applied and processed by heat hardening, and a second film layer of a thickness of approximately 2 µm applied on an outer surface of said sheet, said second film layer having a surface hardness greater than that of said first film layer and comprising an epoxy resin processed by heat hardening. Thus, the invention can provide a low cost, lightweight and readily processed stock roll for disk cartridge shutters which resists flawing and is easily printed upon. The invention can also provide a disk cartridge having a slideable metallic shutter which ensures smooth operation and a high quality surface finish to which durable printing may be applied. The invention is diagrammatically illustrated by way of example in the accompanying drawings, in which: Fig. 1 is a perspective view showing structural components of a disk cartridge; Fig. 2 is a cross-sectional view of a stock roll of shutter material according to the invention, during a punch processing step for manufacture of a disk shutter; Fig. 3 is a perspective view of a bending processing step in the fabrication of a disk shutter according to the invention; Fig. 4 is a perspective view of a completed shutter formed of stock roll material according to the invention; Fig. 5 is a cross-sectional view of the completed shutter of Fig. 4; and Fig. 6 shows an exploded perpsective view of a complete disk cartridge structure utilizing a shutter according to the invention. Referring to Fig. 2, a section of a roll of shutter stock 1 is shown in position for punch processing. As may be seen, the shutter stock 1 is formed in a layered configuration. According to the present embodiment, the shutter stock is based on a metallic layer 2 formed of aluminium. The metallic layer 2 has upper and lower surfaces respectively coated with an upper lubricant containing synthetic resin layer 3 (hereinbelow: lubricant containing layer 3) and a lower plain resin layer 4 (hereinbelow: non-lubricant containing layer 4) formed of synthetic resin to which lubricant has not been added. Further, according to the present embodiment, the lubricant containing layer 3 is formed with a colored tint while the non-lubricant containing layer 4 is formed without coloration (i.e. transparent). The lubricant containing layer 3 is formed of a granular wax having a grain diameter of substantially 1µm uniformly dispersed in a urethane system resin. This composite is evenly applied on the top surface of the metallic layer 2 and treated by heat hardening processing to form a coating film having a thickness of approximately 1µm. Compared to the above lubricant containing layer 3, the non-lubricant containing layer 4 is formed as a resin film having substantially high strength (hardness), based on an epoxy system resin, or the like, which is applied to the lower surface of the metallic layer 2 and processed by heat hardening to form a resin film having a thickness of approximately 2µm. A roll of shutter stock 1 formed as described above is fed into a punch processing apparatus 201 including an upper die 202 and a lower die 203. According to the present embodiment, the shutter stock is fed into the punch processing apparatus 201 such that the lubricant containing layer 3 is faced upward to be contacted by the upper die 202 while the non-lubricant containing layer 4 is faced downward to contact the lower die 203. The upper die 202 punches the shutter stock 1 via the lubricant containing layer 3 to form a punched plate 5 of predesigned shape and dimensions as shown in Fig. 3. As may also be seen in Fig. 3, the punched plate 5 is then fed into a bending processing apparatus 301 including an upper punch 302 and a lower die 303. The bending processing apparatus is active to bend the punched plate 5 into a U-shaped configuration for forming a completed disk cartridge shutter. The upper punch 302 contacts the upper surface of the punched plate 5 which is coated with the lubricant containing layer 3 the same as the shutter stock 1. The bending processing apparatus is arranged such that, after carrying out of bending processing, the punched plate is formed into a U-shaped shutter 11, the inside surface of which is covered by the lubricant containing layer 3 and having a protective layer of the non-lubricant containing layer 4 on an outer surface thereof, as seen in Figs. 4 and 5. Referring now to Fig. 6, a 3.5 inch floppy disk cartridge formed with a shutter according to the invention is shown. As may be seen in the drawing, the disk cartridge includes a disk 22 formed of a recording medium which is rotatably mounted in a casing 25. The casing 25 includes an upper shell 26 and a lower shell 27. The disk 22 is mounted between the upper and lower shells 26, 27 with upper and lower liners 23, 24 interposed between the surface of the disk 22 and the inner surface of the upper and lower shells 26, 27. The upper and lower shells 26, 27 further include a recessed portion 28 for slidably mounting the shutter 11. The recessed portions 28 of the upper and lower shells 26, 27 further have a disk access opening 29 defined therethrough for allowing a head of a disk drive to write to and read from the disk 22. An edge 28a of the recessed portion 28 allows a thickness of the shutter stock 1 forming the shutter 11 to be snugly recessed in the outer surface of the casing 25, slidably mounted via a shutter spring 30. Sliding movement of the shutter 11 when mounted on the casing 25, permits windows 12, 12 formed on each side of the shutter 11 to be positioned so as to correspond to the disk access openings 29, 29 formed in the upper and lower shells 26, 27 exposing the surfaces of the disk 22 during use. Further, an erasure prevention member and a lifter 32 are provided on the lower shell 27. Hereinbelow, the function and effects of the disk cartridge utilizing the shutter 11 formed of the shutter stock 1 as set forth above will be described in detail. First of all, during manufacture, the shutter stock may always be correctly set for shutter processing since the lubricant containing layer 3 and the non-lubricant containing layer 4 are distinguished by colour. That is, the upper lubricant containing layer 3 includes a coloured tint while the non-lubricant containing layer 4 is uncoloured. Alteratively, both layers may be tinted in different colours. In addition, since the lubricant containing layer 3 is faced upward to contact the upper die 202 of the punching apparatus 201, high quality punch processing of the shutter stock 1 may be reliably ensured without need for using press oil, thus costs and processing steps may be reduced. Further, since the shutter 11 formed has the lubricant containing layer 3 at the inner surface of the U-shape and the high-hardness non-lubricant containing layer 4 at the outer surface thereof, printing is carried out on the outer non-lubricant containing layer 4. Accordingly, the best printing results can be obtained even while the need for use of press oil is eliminated. It will also be appreciated that the high hardness of the non-lubricant containing layer 4 ensures that the outer surface of the shutter 11 will resist abrasion and flawing and present a clean appearance while clean shearing of the shutter stock 1 is obtained. Referring to Table 1 below, the results of film adhesion, abrasion resistance, strength to pencil, surface wettability, and strength of printing tests are shown comparing the characteristics of the inner and outer surfaces (i.e. the lubricant containing layer 3 and the non-lubricant containing layer 4) of the shutter 11. TESTED SURFACE INNER SURFACE (3) OUTER SURFACE (4) FILM MATERIAL urethane system resin w/ granular wax kneading epoxy system resin FILM THICKNESS 1µm 2µm FILM ADHESION 92/1000 100/100 ABRASION RESISTANCE 70X 100X STRENGTH TO PENCIL 4H 9H SURFACE WETTABILITY 43 (dyne/cm) more than 54 (dyne/cm) STRENGTH OF PRINTING fairly weak good In testing according to the above table, film adhesion was measured by sectioning areas of the inner and outer film layers (lubricant containing layer 3 and the non-lubricant containing layer 4) into 1µm squares by cutting with a cutter knife and applying a strip of adhesive cellophane tape over the sectioned area. The adhesive tape was then lifted and the number of squares which were lifted and adhered to the tape were counted. Abrasion resistance was measured by rubbing the film surface with a rubber eraser with an applied force of 500g and measuring the time before the onset of surface abrasion. Strength to pencil was measured according to the standards of JIS-K5400. Surface wettability was determined by applying a standard test solution on the film surface and evaluating shrinkage of the film layer. Strength of printing was measured by mixing VIC ink manufactured by Seiko Advance Co. at 8 percent by weight with a specified setting agent, printing the ink on the film layers via silk screen technique, drying for two minutes at 60°C, applying adhesive tape over the printed area then lifting the adhered tape off the printed area and visually evaluating the results. It will be noted that the shutter stock 1 may also be preferrably employed for forming shutter for disks other than standard 3.5inch floppy disks, other types such as magneto-optical disks, etc., may also benefit from the shutter of the invention. Further, it will be noted that, in addition to the other effects and advantages of the invention as noted above, since the lubricant containing layer 3 is finally provided on the inner surface of a U-shaped shutter 11, friction between the inner surface of the shutter and the disk casing 25 can be reduced. Thus the shutter 11 opens more smoothly and sticking or jamming of the shutter mechanism is prevented. Also, since no press oil is used, washing processing to remove oil residue is not required. Thus environmentally harmful solvents, such as trichloroethylene, which are commonly used for such washing processing, are permanently removed from the manufacturing process. Thus, as described hereinabove, there is provided a disk cartridge including a metallic shutter and stock roll material therefor which has all sought for advantages over conventional structures. It will be noted that, although the preferred embodiment is set forth in terms of a U-shaped shutter for a floppy disk cartridge, the present invention may be embodied in various different ways without departing from the scope of the invention as defined in the appended claims.

Claims: A stock roll material for forming disk cartridge shutters, comprising: a sheet (2) of a metallic base material; a first film layer (3) of a thickness of approximately 1 µm applied on one major surface of said sheet (2), said first film layer (3) comprising a granular wax having a grain diameter of substantially 1 µm uniformly dispersed in a urethane resin evenly applied and processed by heat hardening; and a second film layer (4) of a thickness of approximately 2 µm applied on the other major surface of said sheet (2), said second film layer (4) having a surface hardness greater than that of said first film layer (3) and comprising an epoxy resin processed by heat hardening. A stock roll material as set forth in claim 1, wherein said metallic base material is aluminium. A stock roll material as set forth in claim 1, wherein said first film layer (3) further comprises a colouring component such that a surface colour thereof is different from that of said second film layer (4). A method of forming a shutter for a disk cartridge, comprising the steps of: applying a first film layer (3) of a thickness of approximately 1 µm to one major surface of a sheet (2) of a metallic base material, said first film layer (3) comprising a granular wax having a grain of diameter of substantially 1 µm uniformly dispersed in a urethane resin evenly applied and processed by heat hardening; applying a second film layer (4) of a thickness of approximately 2 µm to the other major surface of said sheet (2), said second film layer (4) having a surface hardness greater than that of said first film layer (3) and comprising an epoxy resin processed by heat hardening; punch processing said sheet (2) including said first and second film layers (3, 4) by introducing said sheet (2) to a punching apparatus (201) for forming a punched plate (5), said sheet (2) being oriented such that said first film layer (3) faces a punching member (202) of said punching apparatus (201) so as to lubricate a contact surface of said sheet (2) during such punch processing; and bending said punched plate (5) using a bending apparatus (301) to form a U-shaped shutter (11), said punched plate (5) being arranged at said bending apparatus (301) such that said first film layer (3) forms an inner surface of said shutter (11) and said second film layer (4) forms an outer surface of said shutter (11). A method of forming a shutter as set forth in claim 4, wherein said first film layer (3) further comprises a colouring component such that a surface colour thereof is different from that of said second film layer (4). A method of forming a shutter as set forth in claim 4, wherein said metallic base material is aluminium. A disk cartridge including a slideable shutter, comprising: a cartridge casing (25) including an upper shell (26) and a lower shell (27), said upper and lower shells (26, 27) including recessed areas (28, 28) and disk access openings (29, 29) within said recessed areas (28, 28); a disk (22) formed of a recording medium material rotatably mounted between said upper and lower shells (26, 27); upper and lower liner portions (23, 24) interposed respectively between upper and lower surfaces of said disk (22) and inner surfaces of said upper and lower shells (26, 27); and a shutter (11) slideably mounted astride said upper and lower shells (26, 27) within said recessed areas (28, 28), said shutter (11) having windows (12, 12) on each side thereof which in one position correspond to said disk access openings (29, 29) in said upper and lower shells (26, 27) and expose upper and lower surfaces of said disk (22) for effecting reading or writing operations from or to said disk (22), wherein said shutter (11) comprises a U-shaped sheet (2) of a metallic base material, a first film layer (3) of a thickness of approximately 1 µm applied on an inner surface of said sheet (2), said first film layer (3) comprising a granular wax having a grain diameter of substantially 1 µm uniformly dispersed in a urethane resin evenly applied and processed by heat hardening, and a second film layer (4) of a thickness of approximately 2 µm applied on an outer surface of said sheet (2), said second film layer (4) having a surface hardness greater than that of said first film layer (3) and comprising an epoxy resin processed by heat hardening. A disk cartridge as set forth in claim 7, wherein said first film layer (3) further comprises a colouring component such that a surface colour thereof is different from that of said second film layer (4). A disk cartridge as set forth in claim 7, wherein said metallic base material is aluminium.

Inventors: KIKUCHI SHUICHI, KIKUCHI, SHUICHI
Applicants: SONY CORP, SONY CORPORATION
Application year: 1996
Main classification: G11B23
IPC codes: G11B23