Disk cassette shutter

Abstract: The present invention provides a shutter for a protective envelope containing a recording disk, having both satisfactory sliding property and satisfactory heat-resisting property. The shutter is formed by folding a laminated sheet having a first layer (4b) formed of a material having high heat-resisting property and a second layer (4a) formed of a material having low frictional property so that the first layer forms the outer surface of the shutter and the second layer form the inner surface of the shutter. The first layer of the laminated sheet ensures the shutter satisfactory heat-resisting performance and the second layer of the same ensures the shutter satisfactory sliding performance. A printed layer or an evaporated metal layer may be formed between the first and second layers of the laminated sheet and/or the first and second layers of the laminated sheet may be colored to enhance the aesthetic appearance of the shutter.

Description: The present invention relates to a method of manufacturing a shutter for a protective envelope containing, for example, a 3.5" flexible disc. A protective envelope containing a 3.5" flexible disc is provided with a U-shaped shutter which slides on the protective envelope. Some shutters are formed by pressing a thin stainless steel sheet, some shutters are formed by injection-moulding a synthetic resin, such as polypropylene or polyacetal and some shutters are formed by punching out a blank from a synthetic resin sheet, such as vinyl chloride sheet and folding the blank. A resin shutter is disclosed in US-A-5 161 080 which is in accordance with the precharacterising portion of claim 1. However, there has been no shutter having both satisfactory sliding property and satisfactory heat-resisting property. A stainless steel shutter shows unsatisfactory sliding performance on a protective envelope formed of ABS resin or the like and the stainless shutter is liable to abrade the protective envelope and produce abraded powder. The flexible disc contained in the protective envelope is soiled with the abraded powder, which is possible to cause drop-out in recording information on and reproducing recorded information from the flexible disc. Steel shutters are disclosed in, for instance, JP-A-3-073479 and EP-A2-0 343 844. The former discloses the provision of a synthetic resin coating having a good slipperiness on the steel plate. A shutter formed by folding a synthetic resin sheet has a poor heat resisting property. If the protective envelope is stored in a high-temperature atmosphere, the opposite side walls of the shutter are liable to warp away from each other to increase the width W as shown in Fig. 2(B) of the accompanying drawings. If the width W of the shutter increases, large gaps are formed between the shutter and the protective envelope and the flexible disk contained in the protective envelope is soiled with dust, which is liable to cause drop-out. If filler, such as glass fibers, is added to the synthetic resin sheet to improve the heat-resisting property of the shutter, the sliding property of the shutter is deteriorated and the protective envelope is abraded by the shutter when the same slides on the protective envelope to produce abraded powder. If the synthetic resin forming the synthetic resin sheet is softened to improve the sliding property of the shutter, the heat-resisting property of the shutter will be deteriorated. Thus, the improvement of the sliding property and that of heat-resisting property are incompatible. In manufacturing synthetic resin shutters, for instance, the appearance of the shutters can be improved by forming the shutters in different colours. However, the manufacturing cost of the shutters increases unless the shutters of different colours are manufactured in large lots. The appearance of shutters may be improved by patterns formed by multicolour, multilayer printing. However, it is difficult to select appropriate ink having sufficiently high durability and metallic relief printing, in particular, is scarcely practical. The present invention has been made to solve the foregoing problems and it is therefore an object of the present invention to provide a method of making a shutter satisfactory in both sliding property and heat-resisting property. According to the present invention, there is provided a method of forming a resin shutter to be mounted slidably on a protective envelope containing a recording disc to cover slots formed in the opposite side walls of the protective envelope, by folding a synthetic resin sheet, characterised by forming said synthetic resin sheet (4) as a laminated sheet by laminating a first resin sheet having a high heat resisting property with a second resin sheet having a low frictional property, and folding said laminated sheet to form the shutter with the first sheet forming the outer surface of the shutter and the second sheet forming the inner surface of the shutter. Since the inner layer of this shutter of the present invention thus constructed, to be in sliding contact with the protective envelope is formed of a material having low frictional property, the shutter has improved sliding property. Since the outer layer of this shutter is formed of a material having high heat-resisting property, the width of the shutter will not increase even if the protective envelope provided with the shutter is stored in a high-temperature atmosphere. A shutter for a protective envelope containing a disc, manufactured by a method in accordance with the present invention can be formed by folding a laminated sheet formed by gluing together a transparent sheet carrying a pattern layer formed by printing or evaporation on one surface thereof and an opaque sheet with the pattern layer sandwiched between the transparent sheet and the opaque sheet. Therefore, the colors of the pattern layer formed by printing or evaporation are relieved on the transparent sheet, and the the pattern layer is protected by the transparent sheet and the opaque sheet sandwiching the pattern layer therebetween. The present invention will be further described by way of example only in the following description taken in connection with the accompanying drawings, in which: Fig. 1 is a partially enlarged sectional view of a shutter in a first embodiment according to the present invention for a protective envelope containing a recording disk; Figs. 2(A) and 2(B) are side view of assistance in explaining the prevention of increase in the width of shutters; Fig. 3 is a perspective view of a protective envelope containing a recording disk and provided with a shutter; Fig. 4 is a partially enlarged sectional view of a shutter in a second embodiment according to the present invention for a protective envelope containing a recording disk; Figs. 5(A) to 5(D) are views of assistance in explaining processes of fabricating a shutter in a third embodiment according to the present invention for a protective envelope containing a recording disk; and Figs. 6(A) to 6(D) are sectional views of modifications of the shutter in the third embodiment according to the present invention. First a protective envelope and a shutter will be described with reference to Fig. 3. A protective envelope 1 is formed of a synthetic resin, such as ABS resin, and contains a recording medium 2 having the shape of a disk, such as a 3.5 in. flexible disk. Slots 3 are formed in the opposite sides 1a of the protective envelope 1, and a U-shaped shutter 4 is put on the protective envelope 1 for sliding in the directions of the arrows a to open or close the slots 3. First Embodiment (Fig. 1) Referring to Fig. 1 showing a shutter 4 in a first embodiment according to the present invention, the shutter 4 is formed by punching out a blank from a laminated sheet 8 and folding the heated blank in a U-shape. The laminated sheet 8 is formed by laminating and gluing together two sheets 5 and 6 with an adhesive 7. The sheet 5 forming the inner layer 4a of the shutter 4 to be in sliding contact with the sides 1a of the protective envelope 1 is formed of a material having low frictional property and high abrasion-resisting property, and the sheet 6 forming the outer layer 4b of the same is formed of a material having high heat-resisting property. The sheet 5 having low frictional property and high abrasion-resisting property may be produced by kneading a mixture of a resin, such as polyacetal resin, polypropylene resin, polyamide resin, polyethylene resin or the like, and a lubricant, such as molybdenum sulfide powder, olefin powder, silicon powder or the like, and forming the kneaded mixture in a sheet. The sheet 6 having high heat-resisting property may be produced by kneading a mixture of a resin, such as polypropylene resin; polyamide resin or the like, and a heat-resistant material, such as talc, mica, glass fibers or the like, and forming the kneaded mixture in a sheet. Since the inner layer 4a of the shutter 4 to be in sliding contact with the protective envelope 1 is formed by the sheet 5 having low frictional property and high abrasion-resisting property, the shutter 4 exhibits improved sliding property in sliding on the protective envelope 1 and hence the protective envelope 1 is abraded scarcely by the shutter 4. Thus, the abrasion of the protective envelope 1 and the production of abraded powder can be suppressed to the least extent. Since the shutter 4 also has high abrasion-resisting property, the shutter 4 is not abraded to produce abraded powder. Accordingly, drop-out in recording information on and reproducing recorded information from the recording medium 2 attributable to the abraded powder entered the interior of the protective envelope 1 through the slots 3 and soiling the recording medium 2 can be prevented effectively. Incidentally, the side walls of a shutter 4 formed by folding a heated sheet in a U-shape are liable to warp in the directions of the arrows b as shown in Fig. 2(B) to increase the width W of the shutter 4 when the shutter 4 is stored in a high-temperature atmosphere. If the width W of the shutter 4 increases, large gaps are formed between the sides 1a of the protective envelope 1 and the shutter 4. Since the outer layer 4b of the shutter 4 is formed by the sheet 6 having high heat-resisting property, the width W of the shutter 4 increases hardly as shown in Fig. 2(A) even if the shutter 4 is stored in a high-temperature atmosphere. Thus, the possibility of forming large gaps between the sides 1a of the protective envelope 1 and the shutter 4, and dust entering the interior of the protective envelope 1 and causing drop-out can be reduced to the least extent. When the sheet 5 forming the inner layer 4a of the shutter 4 is a sheet of a material having relatively high heat-shrinking property, such as polypropylene, and the sheet 6 forming the the outer layer 4b of the shutter 4 is a sheet of a material having relatively low heat-shrinking property, such as polyester, the side walls of the shutter 4 tend to warp toward each other and the width W of the shutter 4 tends to decrease as shown in Fig. 2(A) to prevent the increase of the width W positively when the shutter 4 is stored in a high-temperature atmosphere, because the heat-shrinkage of the inner layer 4a of the shutter 4 is higher than that of the outer layer 4b of the same. If a highly printable sheet, such as a polypropylene sheet or the like, is used as the sheet 6 forming the outer layer 4b of the shutter 4, the outer layer 4b of the shutter 4 is highly printable by offset printing or the like. The shutter 4 thus constructed has the following advantages. Since the inner layer 4a of the shutter 4 to be in sliding contact with the protective envelope 1 is formed of a material having low frictional property, the shutter 4 has high sliding property, and the abrasion of the protective envelope 1 by the shutter 4 and the resulting production of abraded powder can be suppressed to the least extent. Accordingly, the possibility of occurrence of drop-out in recording information on and reproducing recorded information from the recording disk contained in the protective envelope 1, attributable to the abraded powder adhering to the recording disk contained in the protective envelope 1 can be reduced to the least extent. Since the outer layer 4b of the shutter 4 is formed of a material having high heat-resisting property, increase in the width W of the shutter when the shutter is stored in a high-temperature atmosphere can be prevented and the possibility of occurrence of drop-out in recording information on and reproducing recorded information from the recording disk contained in the protective envelope 1, attributable to the abraded powder entering the interior of the protective envelop 1 through gaps between the shutter 4 and the protective envelope 1 and adhering to the recording disk contained in the protective-envelope can be reduced to the least extents. Second Embodiment (Fig. 4) Referring to Fig. 4, a shutter 4 in a second embodiment according to the present invention is formed by punching out a blank from a laminated sheet 10 and folding the heated blank in a U-shape. The laminated sheet 10 is formed by laminating and gluing together a metal foil 9, such as an aluminum foil, a stainless steel foil or the like, and two synthetic resin sheets (hereinafter referred to simply as "sheets") 5 and 6 with an adhesive 7 with the metal foil 9 sandwiched between the sheets 5 and 6. The shutter 4 has high heat-resisting property because the outer layer 4b of the shutter 4 is formed by the sheet 6 having high heat-resisting property and the metal foil 9 is sandwiched between the sheets 5 and 6. The width W of the shutter 4 increases hardly as shown in Fig. 2(A) even if the shutter 4 is stored in a high-temperature atmosphere. Thus, the possibility of forming large gaps between the sides 1a of the protective envelope 1 and the shutter 4, and dust entering the interior of the protective envelope 1 and causing drop-out can be reduced to the least extent. Since the metal foil 9 sandwiched between the sheets 5 and 6 is subjected to plastic deformation when the laminated sheet 10 is folded, the laminated sheet 10 is highly workable and the shutter 4 can be readily formed by folding. Furthermore, since the metal foil 9 undergone plastic deformation contributes to securely maintaining the shutter 4 in the U-shape, the increase of the width W of the shutter 4 beyond a design value can be surely prevented when the opposite side walls of the shutter 4 are bent toward each other as indicated by the arrows c in Fig. 1(A) in forming the shutter 4 by folding the laminated sheet 10. Third Embodiment A shutter 9 in a third embodiment according to the present invention is formed by folding a laminated sheet formed by gluing together a transparent sheet carrying a pattern layer formed by printing or evaporation on one surface thereof and an opaque sheet with the pattern layer sandwiched between the transparent sheet and the opaque sheet. Therefore, the colors of the pattern layer formed by printing or evaporation are relieved on the transparent sheet, and the pattern layer is protected by the transparent sheet and the opaque sheet sandwiching the pattern layer therebetween. The properties and performance of the materials forming the transparent sheet and the opaque sheet are similar to those of the corresponding sheets forming the shutters 4 in the first and second embodiments, and hence the description thereof will be omitted. A method of manufacturing the shutter 9 in the third embodiment will be described hereinafter with reference to Figs. 5(A) to 5(D). Referring to Fig. 5(A), a laminated sheet 13 is formed by putting together a transparent sheet 11 of a synthetic resin, such as polypropylene, polyacetal, polyamide, polyethylene or the like, and an opaque sheet 12. The transparent sheet 11 is a light-transmissive sheet, such as a colorless, transparent sheet, a translucent sheet or a colored, transparent sheet colored in light red, light yellow or the like, and the opaque sheet 12 is a colored opaque sheet colored in black, dark blue, dark red or the like. Referring to Fig. 5(A), the transparent sheet 11 and the opaque sheet 12 are pulled out respectively from rolls 11a and 12a. A pattern layer 15 showing manufacturer's name and item designation is printed on the lower surface, as viewed in Fig. 5(A), by a first transfer printing unit 14, the pattern layer 15 is dried by a first drying unit 16, a background layer 18, a printed layer or an evaporated metal layer, is formed by a second transfer printing unit (or an evaporating unit) 17 on the same surface of the transparent sheet 11 so as to coat the pattern layer 15, and then the background layer 18 is dried by a second drying unit 19. An adhesive layer 21 is formed on the upper surface, as viewed in Fig. 5(A), of the opaque sheet 12 by an adhesive application unit 20. Then, the transparent sheet 11 and the opaque sheet 12 are pressed together by a pair of pressure rollers 22 to produce the laminated sheet 13. As shown in Fig. 5(B), the laminated sheet 13 thus manufactured has the pattern layer 15 and the background layer 17, i.e., a printed layer or an evaporated metal layer, sandwiched between the transparent sheet 11 and the opaque sheet 12. Referring to Fig. 5(C), blanks 9a, i.e., am unfolded shutters 9, are punched out successively from the laminated sheet 13 by a press. In punching out the blanks 9a, the laminated sheet 13 is positioned through the detection of positioning marks 23 printed on the transparent sheet 11 in forming the pattern layer 15 or the background layer 18 by photoelectric detectors in order that the blanks 9a are punched out correctly. Then, as shown in Fig. 5(D), each blank 9a is folded by a press in a U-shape with the transparent sheet 11 forming the outer surface and the opaque sheet 12 forming the inner surface to form a shutter 9. The colored pattern layer 15 and the colored background layer 18 (or an evaporated metal layer) sandwiched between the transparent sheet 11 and the opaque sheet 12 can be seen in relief through the transparent sheet 11, which enhances the aesthetic value of the shutter 9. Since the pattern layer 15 and the background layer 18 (or an evaporated metal layer) are sandwiched perfectly between the transparent sheet 11 and the opaque sheet 12, the durability of the pattern layer 15 and the background layer 18 (or an evaporated metal layer) is scarcely a problem and inks for printing the pattern layer 15 and the background layer 18 can be readily selected. Modifications Modifications of the laminated sheet 13 used for forming the shutter 9 in the third embodiment will be described hereinafter. A laminated sheet 13 shown in Fig. 6(A) is formed by forming a background layer 18, i.e., a printed layer or an evaporated metal layer, on the upper surface of an opaque sheet 12, forming a pattern layer 15 showing manufacturer's name, item designation and the like on the background layer 18 and gluing a transparent sheet 11 to the upper surface of the opaque sheet 12 with a transparent adhesive 21a. A laminated sheet 13 shown in Fig. 6(B) is formed by printing a pattern layer 15 showing manufacturer's name, item designation and the like on a transparent sheet 11, forming an evaporated metal layer 24, such as an evaporated aluminum layer, over the upper surface of the opaque sheet 12 and gluing together the transparent sheet 11 and the opaque sheet 12 with a transparent adhesive 21a. The evaporated metal layer 24 of this laminated sheet 13 can be seen through the transparent sheet 11 and the transparent adhesive 21a to give the laminated sheet 13 a metallic appearance. A laminated sheet 13 shown in Fig. 6(C) is formed by printing a pattern layer 15 showing manufacturer's name, item designation and the like on the lower surface of a transparent sheet 11, coating the pattern layer 10 with a lightly colored intermediate transparent layer 25, such as a light yellow transparent layer, by printing, forming an evaporated layer 24, such as an evaporated aluminum layer, on the upper surface of an opaque sheet 12 by evaporation, and gluing together the transparent sheet 11 and the opaque sheet 12 with a transparent adhesive 21a. The evaporated metal layer 24, similarly to the evaporated metal layer 24 of the laminated sheet 13 shown in Fig. 6(B), gives the laminated sheet 13 a metallic appearance. A laminated sheet 13 shown in Fig. 6(D) is formed by forming a holographic pattern 26 in the lower surface (or the upper surface) of a transparent sheet 11-, printing a pattern layer 15 showing manufacturer's name, item designation and the like on the lower surface of the transparent sheet 11, forming an evaporated metal layer 24, such as an evaporated aluminum layer, by evaporation on the upper surface of an opaque sheet 12, and gluing together the transparent sheet 11 and the opaque sheet 12 with a transparent adhesive 21a. This laminated sheet 13 has a holographic effect. The pattern layer 15 showing manufacturer's name, item designation and the like may be printed on the upper surface, i.e., the outer surface, of the laminated sheet 13 as indicated by alternate long and short dash lines in Figs. 5(B) and 6(A) to 6(D). The pattern layer 15 may be printed by silk printing or pad printing on the outer surface of the shutter 9 formed by punching a blank 9a from the laminated sheet 13 and folding the blank 9a in a U-shape. The method of manufacturing a shutter for a protective envelope containing a disk has the following advantages. Since a shutter is formed by folding a blank punched out from a laminated sheet provided with a pattern layer and a background layer formed by printing or evaporation and sandwiched between a transparent sheet and an opaque sheet, the colored pattern layer and the colored background layer can be seen in relief through the transparent sheet, which gives the shutter an aesthetically improved appearance. Since the pattern layer and the background layer are sandwiched protectively between the transparent sheet and the opaque sheet, the durability of the inks forming the pattern layer and the background layer is scarcely a problem and appropriate inks can be readily selected. A shutter having a relieved metallic appearance can be readily produced at a reduced cost by forming an evaporated metal layer, such as an evaporated aluminum layer, between the transparent sheet and the opaque sheet. Although the invention has been described in its preferred embodiments it may be practiced otherwise than as specifically described herein without departing from the scope of the attached claims.

Claims: A method of forming a resin shutter (4) to be mounted slidably on a protective envelope (1) containing a recording disc (2) to cover slots (3) formed in the opposite side walls of the protective envelope (1), by folding a synthetic resin sheet (4), characterised by forming said synthetic resin sheet (4) as a laminated sheet (4) by laminating a first resin sheet (6) having a high heat resisting property with a second resin sheet (5) having a low frictional property, and folding said laminated sheet (4) to form the shutter with the first sheet (6) forming the outer surface (46) of the shutter (4) and the second sheet (5) forming the inner surface (4a) of the shutter (4). A method of forming a resin shutter according to claim 1, wherein the first and second sheets (5,6) of the laminated sheet (4) are glued together by an adhesive layer (7). A method of forming a resin shutter according to claim 1 or 2, wherein the laminated sheet (4) includes a metal layer (9,18,24). A method of forming a resin shutter according to claim 1, 2 or 3, wherein the laminated sheet (4) is folded to have a substantially U-shaped cross-section with a pair of side walls for closing the slots (3) formed on the protective envelope (1), and a wall connecting the pair of side walls. A method of forming a resin shutter according to claim 1, 2, 3 or 4, wherein the first sheet (6,11) is transparent, and the second sheet (5,12) is opaque. A method of forming a resin shutter according to claim 5, including the step of sandwiching a printed layer or an evaporated layer (15,18) between the transparent first sheet (6,11) and the opaque second sheet (5,12). A method of forming a resin shutter according to claim 5, including the step of forming a holographic pattern between the transparent first sheet (6,11) and the opaque second sheet (5,12).

Inventors: KIKUCHI SHUICHI, KIKUCHI, SHUICHI, Kikuchi, Shuichi, c/o Sony Magnetic products Inc.
Applicants: SONY CORP, SONY CORPORATION
Application year: 1992
Main classification: G11B23
IPC codes: G11B23, B29C53, B32B27