Magnetic tape cassette

Abstract: The present invention is directed to a tape reel in which a thin flange portion is formed by reducing a thickness of each of front and rear flange surfaces of the tape reel and a thick portion having a thickness larger than that of the thin flange portion is formed on a plurality of places of an outer periphery of the flange portion. When the tape reel is molded by using a molding metal mold, a pin is inserted into the molding metal mold at a portion corresponding to a portion where a resin is filled into the thin flange portion last, and air and gas within a cavity are discharged from a spacing formed between the molding metal mold and the pin. Thus, the occurrence of short mold and weld line on the thin portion of the tape reel thus molded can be avoided and a rotational fluctuation of the reel flange surface can be avoided. Also, the present invention is directed to a tape reel in which front and rear surface portions of each of upper and lower flanges are formed as thin flange portions by uniformly reducing the thickness of each of the front and rear surface portions thereof except outer peripheral edge portions thereof and radial tape position restricting ribs 7 are formed on tape contact flange surfaces of the upper and lower flanges. Thus, the flanges can be prevented from being warped even when the thicknesses thereof are reduced. The tape reel can be made light in weight and the material therefor can be saved. Also, the tape reel of the present invention can achieve a similar action to that of the conventional tape reel.

Description: The present invention relates to tape cassettes and, more particularly, to tape reels around which a magnetic tape or the like is wound and a metal mold for manufacturing these tape reels. FIG. 1 of the accompanying drawings shows an example of a conventional tape reel. As shown in FIG. 1, the conventional tape reel comprises a reel hub 3 serving as a tape wrapping shaft and parallel upper and lower flanges 1 and 2 attached to the reel hub 3. These upper and lower flanges 1 and 2 restrict the positions of edge portions of a magnetic tape (not shown) wound around the reel hub 3 and the magnetic tape is wound around the reel hub 3. When the above tape reel is made light-weight or is reduced in cost in accordance with the reduction of material, if the outer diameters of the upper and lower flanges 1 and 2 are the same, then it is proposed that the thicknesses of both surface sides of the upper flange 1 and the lower flange 2, i.e., the thickness of the upper surface side of the upper flange 1 and the thickness of the lower surface side of the lower flange 2 are reduced as shown in FIG. 1. If, however, only the thicknesses of the front surface sides of the upper and lower flanges 1 and 2 are reduced, then the upper and lower flanges 1 and 2 tend to curve to the rear sides whose thicknesses are not reduced, i.e., the upper and lower flanges 1 and 2 warp as shown by phantoms in FIG. 1. This occurs because the upper and lower flanges shrink unevenly as the molded products cool after injection molding. When the upper and lower flanges 1 and 2 warp toward the rear surface sides, a disc rotation fluctuation occurs during the tape reel is rotated. Further, the spacing between the upper and lower surfaces 1 and 2 is reduced so that the edge portions of the magnetic tape wrapped around the reel hub 3 are pressed by the rear surfaces of the upper and lower flanges 1 and 2, which unavoidably damages the tape edge. To eliminate the aforesaid drawbacks, there is proposed a tape reel 11 shown in FIGS. 2 and 3 of the accompanying drawings. As shown in FIGS. 2 and 3, the front and rear flange surfaces are molded as three arcuate thin flanges portions 15 which result from uniformly reducing thickness from an outer peripheral edge portion 12 to a reel bearing shaft 13 while a plurality of (three) radial ribs 14 are left. When the above tape reel 11 is molded by using a metal mold, as shown in FIG. 2 an amount of resin material flowed into the three arcuate thin flange portions 15 is small and the last injection of resin is effected on hatched portions 15c of the outer peripheral sides of the flanges portions 15. Consequently, air within a cavity of the metal mold and gas discharged from the molding material may not be discharged to the outside of the cavity and remain within the cavity. As a result, a so-called short mold or weld line of the flange thin portion is produced in the molded product, which deteriorates the quality of the molded product. Also, the flange can be warped due to the short mold causing considerable fluctuations on rotation of the flange surface. There is then the problem such that the edge portions of the magnetic tape wrapped around the tape reel are damaged. In view of the above-mentioned aspect, it is an object of the present invention to provide a tape reel in which the aforesaid shortcomings and disadvantages of the prior art can be eliminated. According to the present invention, there is provided a tape reel comprising: an upper flange; a lower flange; thin flange portions which result from uniformly thickness reducing front and rear flange surfaces of said upper and lower flanges with respect to the outer peripheral edge in a moulding process; and a plurality of tape position restricting ribs formed on upper and lower flanges at tape contact flange surfaces of thin flange portions such that the plurality of tape position restricting ribs radially extend from a central portion of the tape reel to an outer peripheral edge thereof, characterised in that said tape position restricting ribs are only formed on said tape contact flange surfaces and not on the opposed flange surfaces. Thus with the present invention the reel flanges can be prevented from being warped even when the thickness of each of the flanges is reduced while the reel can be made light in weight and the material therefor can be reduced. Thick portions which are thicker than the thin flange portions may be formed at a plurality of places in the vicinity of an outer periphery of the thin flange portions. With this aspect the occurrence of short mould and weld line on the tape reel provided as a moulded product can be avoided and it is possible to avoid a rotational fluctuation of reel flange surface. The invention also provides a tape cassette including such reels. According to another aspect, the present invention, provides a tape reel manufacturing metal mould which comprises a tape reel moulding metal mould for moulding a tape reel as defined above which has a plurality of gas and air discharging pins provided on a portion where a resin is filled into the thin flange portions last in the manufacturing process of the tape reel. This aspect of the present invention can provide a tape reel manufacturing metal mould in which the occurrence of short mould and weld line on the tape reel provided as a moulded product can be avoided and also rotational fluctuation of reel flange surface may be avoided. The present invention will be further described in the following detailed description of illustrative embodiments thereof to be read in conjunction with the accompanying drawings, in which like reference numerals are used to identify the same or similar parts in the several views, and in which:- FIG. 1 is a longitudinal cross-sectional view showing an example of a conventional tape reel; FIG. 2 is a plan view showing an upper flange of another example of the conventional tape reel; FIG. 3 is a cross-sectional view showing the upper flange of another example of the conventional tape reel; FIG. 4 is a plan view showing a front surface of an upper flange of a tape reel according to a first embodiment of the present invention; FIG. 5 is a plan view showing a rear surface of the upper flange of the tape reel according to the first embodiment of the present invention; FIG. 6 is a longitudinal cross-sectional view of the tape reel according to the first embodiment of the present invention; FIG. 7 is a plan view showing an upper flange of the tape reel according to a second embodiment of the present invention; FIG. 8 is a cross-sectional view taken along the line VIII - VIII in FIG. 7; FIG. 9 is a cross-sectional view of a metal mode for molding the upper flange according to the second embodiment of the present invention; FIG. 10 is a plan view showing a rear surface of a molded surface of the upper flange molded by a female metal mold according to the second embodiment of the present invention; FIG. 11 is a plan view showing a molded surface of the upper flange molded by a male metal mold according to the second embodiment of the present invention; FIG. 12 is a plan view of the rear surface of the upper flange and illustrating the condition such that the last resin injection process is effected in the second embodiment of the present invention; and FIG. 13 is a cross-sectional view of a metal mold which molds a lower flange according to the second embodiment of the present invention. A first embodiment of the present invention will hereinafter be described with reference to the drawings. FIG. 4 of the accompanying drawings shows a plan view of a surface of an upper flange of a tape reel according to the first embodiment of the present invention. FIG. 5 of the accompanying drawings is a plan view showing a rear surface of the same upper flange and FIG. 6 of the accompanying drawings shows a longitudinal cross-sectional view of an overall arrangement of the tape reel according to the first embodiment of the present invention. As illustrated in FIGS. 4 to 6, a tape reel 20 of the first embodiment comprises an upper flange 21, a lower flange 22 and a reel hub 23. The lower flange 22 and the reel hub 23 are molded as one body and the upper flange 21 is coupled to the concave portion of an upper end portion of the reel hub 23 by some suitable process such as a caulking or the like. A lower reel receiving shaft 24 is formed at a central lower portion of the lower flange 22. Through the lower reel receiving shaft 24 and on the inside of the reel hub 23, there is formed a hub driving concave portion 25 into which a hub drive shaft (not shown) is inserted. The upper flange 21 and the lower flange 22 will be described more fully. The upper and lower flanges 21 and 22 are uniformly reduced in thickness from their front and rear flange surfaces by the same thickness except outer peripheral edge portions 26 thereof to thereby form thin flange portions 21a and 22a. That is, the respective flange portions 21a and 22a are molded so as to be located at the central positions in the thicknesses of the upper and lower flanges 21 and 22 as shown in FIG. 6. On the flange surfaces on the rear surfaces of the upper and lower flanges 21 and 22, i.e., flange surfaces, with which a magnetic tape T is brought in contact, of the upper and lower flanges 21 and 22, there are formed a plurality of (three ribs in this embodiment) tape position restricting ribs 27 which are radially extended from the reel hub 23 side to the outer peripheral side (see FIGS. 4 and 5). The tape position restricting ribs 27 are formed on the same plane as the outer peripheral edge portions 26 of the upper and lower flanges 21, 22 so that the thin flange portions 21a, 22a formed on the rear surfaces sides of the upper and lower flanges 21, 22 are formed as arcuate portions, respectively as shown in FIG. 5. No ribs are formed on the other side of the flanges. According to the tape reel 20 thus arranged, when the magnetic tape T is wrapped around the reel hub 23 as shown by a phantom in FIG. 6, the tape edges of the magnetic tape T are positionally restricted by the tape position restricting ribs 27 and aligned regularly. Accordingly, although the spacing between the flange surfaces of the upper and lower flanges 21, 22 is relatively increased as compared with the tape width of the magnetic tape T because the upper and lower flanges 21, 22 are formed as the thin flange portions 21a, 22a, the magnetic tape T can be accurately wound around the reel hub 23 by a plurality of radial tape position restricting ribs 27 formed on the rear surfaces of the upper and lower flanges 21, 22, similarly to the conventional tape reel. The thin flange portions 21a, 22a of the upper and lower flanges 21, 22 are molded so as to be located at the central portions of the thicknesses of the upper and lower flanges 21, 2 so that, even when molded products are shrunk because the molded product is cured after the product tape reel was molded by the injection molding process, the upper and lower flanges 21 and 22 are shrunk equally. Therefore, it is possible to obtain the tape reel in which the upper and lower flanges 21, 22 can be prevented from being warped. As a result, when the tape reel is rotated, the rotational fluctuation of the upper and lower flanges 21, 22 can be avoided and the tape edge of the magnetic tape T can be prevented from being urged against the flange surfaces, which can prevent the tape edges from being damaged. Furthermore, since the upper and lower flanges 21, 22 are reduced in thickness, the tape reel of this embodiment can be made light in weight and the material for making this tape reel can be saved. Of conventional tape reels, there is known a tape reel in which a flange portion comprises only an outer peripheral edge portion and a plurality of radial ribs. In the case of this type of conventional tape reel, the thickness thereof must be increased in order to obtain a predetermined strength of the tape reel. There is then the problem that such tape reel cannot be decreased in weight. In the case of the tape reel according to this embodiment, the thicknesses of the outer peripheral edge portion 26 of the tape reel and the tape position restricting ribs 27 need not be changed and may be ordinary. Therefore, the tape reel can be reduced in weight overall. While the three tape position restricting ribs 27 are formed in a radial fashion as described above, the present invention is not limited thereto and the number of the tape position restricting ribs 27 may be varied freely. Furthermore, the tape reel according to the first embodiment can be applied to a wide variety of cassette tape reels. A second embodiment of the present invention will hereinafter be described with reference to the drawings. FIG. 7 of the accompanying drawings shows a plan view of an upper flange of a tape reel according to a second embodiment of the present invention, and FIG. 8 of the accompanying drawings shows a cross-sectional view taken along the line VIII - VIII in FIG. 7. As illustrated, a surface side (tape opposing side) of an upper flange 31 is molded as an annular thin flange portion 38a which is reduced in thickness by a predetermined thickness except an outer peripheral edge portion 36 of a predetermined width. A rear surface side (tape side) of the upper flange 31 is molded as three arcuate thin flange surfaces 38b which are reduced in thickness in such a fashion that a plurality of tape position restricting ribs 37, each having a predetermined width, radially extend from the outer peripheral edge portion 36 and a reel bearing receiving shaft 39. The tape position restricting ribs 37 are flush with the outer peripheral edge portion 36. These thin flange surfaces 38a, 38b constitute a flange portion 38 where the upper flange 31 is reduced in thickness by the same thickness from the front and rear surfaces thereof. According to this embodiment of the invention three thick portions 40 are integrally molded with the outer peripheral edge portion 36 at an equal interval on the thin flange surfaces 38a of the surface side of the above flange portion 31. The thick portions 40 are each a portion in which the last resin injection is effected when the tape reel is molded by using the metal mold. According to the second embodiment of the present invention, the thick portions 40 are formed as semi-circular thick portions and flush with the outer peripheral edge portion 36. Since the thick portions 40 are provided on the outer peripheral portions of the thin flange surfaces 38a, the outer peripheral portions of the thin flange surfaces 38a, 39b which are weak in strength can be given a sufficient strength. Consequently, the rotational fluctuation of the upper flange 31 can be avoided during rotation of the tape reel. Therefore, the tape edge of the tape wrapped around the tape reel can be prevented from being damaged. FIG. 9 of the accompanying drawings shows a cross-sectional view of a metal mold which is used to mold the upper flange 31. FIG. 10 of the accompanying drawings shows a plan view of a female metal mold which serves as a cavity side and is seen from the cavity surface side. FIG. 11 of the accompanying drawings shows a plan view of a molding flask under the condition such that a male metal mold which serves as a core side is seen from the cavity surface side. As illustrated, the molding metal mold comprises a female metal mold 41 and a male metal mold 42. A molding mold 41a of the female metal mold 41 and a molding mold 42a of the male metal mold 42 constitute a cavity 43 that serves as a molding room for the above upper flange. More specifically, an annular-shaped insert or liner 44 that is used to mold the thin flange surfaces 38a (see FIGS. 7, 8) is incorporated into the female metal mold 41, while a plurality of arcuate inserts or liners 45 that are used to mold the thin flange surfaces 38b (see FIGS. 7, 8) are incorporated into the male metal mold 42. In the female metal mold 44, there is provided a sprue 46 which serves as a mouth through which a resin is injected into the cavity 43. Three pins 47 that are used to discharge gas or air within the cavity 43 to the outside are inserted into the female metal mold 41 at its portions corresponding to the above thick portions 40 of the upper flange 38. A molding portion 43a of the thick portion 40 is formed on the top end portion of each pin 47. That is, the gas or air within the cavity 43 is discharged through a spacing 48 formed between the female metal mold 41 and the pin 47. The spacing 48 formed between the female metal mold 41 and the pin 47 in the diametrical direction is, for example, about 2/100 mm. In FIG. 9, reference numeral 19 depicts a so-called core pin of the male metal mold 42. A molding process for molding the upper flange 31 by using the molding metal mold thus arranged will be described with reference to also FIGS. 7 and 8. Initially, a resin is filled to the molding metal mold from the sprue 46. The resin filled into the molding metal mold from the sprue 46 travels from the reel receiving shaft 39 through the ribs 37 each having a relatively wide path and then fills in the outer peripheral edge portion 36. Since the path of the thin flange portion 38 is narrow, the resin there flows slowly. Therefore, as shown by a hatched area in FIG. 12 of the accompanying drawings, a resin a is filled toward the outside from the surrounding of the reel receiving shaft 39. Finally, the resin is filled into the thick portion 40 of the pin 47 as shown in FIG. 12. An amount of resin filled into the thick portion 40 is relatively large so that, after being discharged at the portion of the thick portion 40 where the final filling is effected, air or gas within the cavity 43 is discharged through the spacing 48 between the female metal mold 41 and the pin 47 to the outside. Therefore, in the final stage of the molding process, the air or gas within the cavity 43 is thoroughly discharged so that defects such as the short mold or the like on the flange thin portion can be avoided and that the weld line can be prevented from being produced on the molded product. Thus, the quality of molded product can be enhanced. In the tape reel thus arranged and molded by the molding metal mold as described above, since the thick portions 40 are molded on the outer peripheral portion of the thin flange portion 38 which is the final filling portion, the outer peripheral portion of the thin flange portion 38 can be reinforced and the rotational fluctuation of the flange surface can be avoided. As a result, the tape edge can be prevented from being damaged. Furthermore, the occurrence of defects such as a short mold or the like and the occurrence of weld line can be removed from the flange thin portion provided as the molded product, which can be improve the quality of the product. FIG. 13 of the accompanying drawings shows a cross-sectional view of a molding metal mold that is used to mold the lower flange. As shown in FIG. 13, this molding metal mold comprises a female metal mold 50 serving as a cavity side and a male metal mold 51 serving as a core side. A molding mold 50a of the female metal mold 50 and a molding mold 51a of the male metal mold 51 constitute a cavity 52 that serves as a room in which a lower flange unitarily formed with the reel hub is molded. In the case of the lower flange, similarly to the upper flange, radial-shaped ribs are formed on the front surface side (tape side) of the flange surface. Accordingly, the front flange surface is reduced in thickness so as to provide arcuate thin portions. Inserts or liners 53 and 54 that are used to mold the thin portions are incorporated within the female metal mold 50 and the male metal mold 51, respectively. Into the female metal mold 50, there is inserted an air or gas discharging pin 55 having a predetermined spacing 56 between it and the female metal mold 50 in association with the thick portion molded on the portion where the resin is filled last similarly to the above upper flange. A thick portion molding portion 52a is formed on the top end side of the pin 55. In FIG. 13, reference numerals 57 depicts a sprue used to fill a resin into the cavity 52, 58 an insert or liner used to mold a hub of the lower flange and 59 a so-called core pin. Also in the thus arranged molding metal mold of the lower flange, similarly to the upper flange metal mold, air or gas within the cavity 52 can be discharged to the outside through the spacing 56 formed between the female metal mold 50 and the pin 55. While the above thick portions 40 are flush with the flange outer peripheral edge portion 36 in thickness as described above, the present invention is not limited thereto and the thickness of the thick portion 40 may be larger than that of the thin flange portion 38. Further, while the thick portion 40 is formed as the arcuate shape as described above, the present invention is not limited thereto and the shape of the thick portion 40 may be varied freely. Furthermore, while the thick portion 40 is formed on the surface side of the upper flange 31, the present invention is not limited thereto and the thick portion 40 may be formed on the flange outer peripheral portions of the front and rear thin flange surfaces 38a, 38b of the upper flange 31. As described above, according to the present invention, since the front and rear surface portions of the upper and lower flanges are molded as the thin flange portions which result from uniformly reducing the thickness of their front and rear surface portions by the same thickness, the molded product can be prevented from being warped and the rotational fluctuation of the flange surface can be avoided during the tape reel is rotated. Consequently, the tape edge of the magnetic tape can be prevented from being damaged. Also, since the upper and lower flanges are reduced in thickness, the tape reel can be reduced in weight and the molding material for molding the tape reel can be saved. Since the radial tape position restricting ribs are formed on the flange surfaces at which the upper and lower flanges are brought in contact with the magnetic tape, the magnetic tape can be prevented from being wound around the tape reel irregularly. Hence, the quality of the tape reel can be prevented from being deteriorated. Further, since a plurality of thick portions which are thicker than the flange portion can be formed on the outer peripheral portion of the thin flange portions which result from reducing the thickness of the front and rear flange surfaces of the reel flange, the outer peripheral portion of the thin flange portion can be increased in strength. Consequently, the reel flange can be prevented from being warped and the rotational fluctuation of the flange surface can be avoided. Therefore, the tape edge of the magnetic tape wrapped around the tape reel can be prevented from being damaged. Furthermore, since the thick portion formed on the outer peripheral portion of the thin flange portion is the portion where the resin is filled last in the molding process and the pin for discharging the gas or air is formed on the metal mold portion of this portion, the gas or air within the metal mold in the final stage of the molding process can be discharged completely. Therefore, the occurrence of defects such as the short mold or the occurrence of weld line on the flange thin portion as the molded product can be avoided. Thus, the quality of the tape reel as the molded product can be improved considerably.

Claims: A tape reel comprising: an upper flange (21,31); a lower flange (22,32); thin flange portions (21a,22a,28a) which result from uniformly thickness reducing front and rear flange surfaces of said upper and lower flanges (21,22,31,32,38a) with respect to the outer peripheral edge (26,36) in a moulding process; and a plurality of tape position restricting ribs (27,37) formed on upper and lower flanges at tape contact flange surfaces of thin flange portions (21a,22a) such that the plurality of tape position restricting ribs (27,37) radially extend from a central portion of the tape reel to an outer peripheral edge (26,36) thereof, characterised in that said tape position restricting ribs (27,37) are only formed on said tape contact flange surfaces and not on the opposed flange surfaces. A tape reel according to claim 1, further comprising: a thick portion (40), which is thicker than said thin flange portions (37) formed at a plurality of places in the vicinity of an outer periphery (36) of said thin flange portions (37). The tape reel according to claim 2, wherein said thick portions (40) are formed on the flange surfaces opposite to the tape contact flange surfaces. The tape reel according to claim 1, 2, or 3, wherein said tape position restricting ribs (27,37) are flush with the outer peripheral edge portion (26,36). A tape cassette having a tape reel according to any one of the preceding claims. A tape reel manufacturing metal mould comprising: a tape reel moulding metal mould (41,51) for moulding a tape reel in accordance with claim 2, the mould (41,51) comprising: a plurality of gas and air discharging pins (47,55) provided through said metal mould (41,51) at portions where a resin is filled into the thin flange portions (21a,22a,38a) last in the manufacturing process of the tape reel. The tape reel manufacturing metal mould according to claim 6, wherein the final filling portions are the thick portions (40).

Inventors: AOKI MAKOTO, MAKINO MASAHIRO, SAKURAI SATOSHI, AOKI, MAKOTO, MAKINO, MASAHIRO, SAKURAI, SATOSHI, Aoki, Makoto, c/o Sony Corporation, Makino, Masahiro, c/o Sony Corporation, Sakurai, Satoshi, c/o Sony Corporation
Applicants: SONY CORP, SONY CORPORATION
Application year: 1992
Main classification: G11B23
IPC codes: G11B23