MOLD FOR MOLDING A REEL LOCK MEMBER

Abstract: A mold for molding a reel lock member which member includes a retaining pawl, a sliding body portion and a flexible hinge portion. The retaining pawl locks the rotation of a reel by engaging with engaging teeth of a magnetic tape reel. The sliding body portion is slidable between a reel locking position at which the retaining pawl is engaged with the engaging teeth and a reel unlocking position at which the engagement is released. The flexible hinge portion is provided between the retaining pawl and the sliding body portion. The mold comprises a main core (2) and a slide core (3). The slide core is movable relative to the main core (2) and has a portion for forming at least part of the hinge portion in such a manner that a thickness of the hinge portion is varied by changing a positional relationship between the main mold and the slide core.

Description: SPECIFICATION MOLD FOR MOLDING A REEL LOCK MEMBER [Technical Field] The present invention relates to a mold for molding a reel lock member for locking the rotation of reels fc>y engaging flanges of magnetic tape reels. [Background Art] Among conventional magnetic tape cassettes, there are various forms. For example, in a magnetic tape cassette 50 whose internal structure is shown in Fig. 3, a pair of reels 62 and 63 are rotatably disposed within a lower cassette half 61 (the drawing shows a state in which an upper cassette half is removed) , and a magnetic tape 64 is wound around the reels 62 and 63. The magnetic tape 64 is guided by tape guides 65 and 66 on the front side (the upper side in Fig. 3) of the cassette at left and right sides thereof, and is adapted to pass through an opening 67 on the front side of the lower cassette half 61. Further, engaging teeth 70 and 71 are formed on the entire circumferences of outer edges of lower flanges 68 and 69 of the reels 62 and 63, respectively. Meanwhile, a reel lock member 72 for locking the rotation of the reels 62 and 63 is disposed on the rear side of the cassette so as to prevent the slackening of the magnetic tape 64 when the magnetic tape cassette 50 is not loaded in a recording and reproducing apparatus (not shown), i.e., when the cassette is stored or carried around. Substantially triangular ribs 90 and 91 are provided between the reels 62 and 63 in such a manner as to project from a rear plate portion 74 of the lower cassette half 61. Straight portions 75 and 76 of these ribs 90 and 91 are disposed in face-to-face relation, and the reel lock member 72 is slidably inserted between these straight portions 75 and 76. The reel lock member 72 is urged toward the front side of the cassette by the urging force of a compression coil spring 78 (brake spring) . An insertion hole 79 for inserting an unlocking pin of the recording and reproducing apparatus is provided in a bottom surface of the reel lock member 72. An opening (not shown) corresponding to the insertion hole 79 in the reel lock member 72 is provided in a bottom wall of the lower cassette half 61. The reel lock member 72 is provided with a rectangular sliding body portion 81 which is formed of an appropriate resilient resin, e.g., polyacetal or the like, and has a relatively large bottom area for stable sliding. Engaging pawls 82 and 83 which are engageable with the engaging teeth 70 and 71 of the reels 62 and 63 are formed integrally with a front end face of the sliding body portion 81. As an another example of the reel lock member, a reel lock member 30 of the shape shown in Figs. 4(a) and 4(b) has been proposed. The reel lock member 30 has retaining pawls 32 and 33 for locking the rotation of the reels by engaging the engaging teeth of the reels; a sliding body portion 31 which slides over the cassette half between a reel locking position and a reel unlocking position at which the sliding body portion 31 is retracted from the reel locking position and its engagement with the engaging teeth is canceled; flexible thin-walled hinge portions 35 and 36 respectively provided between the sliding body portion 31 and each of the retaining pawls 32 and 33; and a cruciform spring engaging portion 37 for engaging the compression coil spring. The hinge portions 35 are provided in such a way that the lock of the reels will not be canceled when the magnetic tape cassette is dropped and an impact is applied to the cassette itself . Next, a description will be given of a method of molding the reel lock member 30. As shown in Fig. 5, a cavity 40 for molding the reel lock member 30 is provided by a fixed main core 41 and a movable slide core 42. The main core 41 and the slide core 42 are disposed in face-to-face relation so as to allow the releasing and clamping of the mold, and define the cavity 40 when the mold is set in a clamped state. When the mold is set in the clamped state, a molten resin is injected and charged under pressure into the cavity 40, and the resin is then allowed to cool and solidify, thereby molding the reel lock member 30. With the above-described reel lock member 30, it is necessary to alter the thicknesses of the hinge portions 35 and 36, as required, in correspondence with appropriate values for locking the reels. However, when fabricating the reel lock members having different thicknesses of the hinge portions, it has been necessary to prepare exclusively-used main cores for the respective types and set them in the molding machine in correspondence with the types to be manufactured. With such a molding method, the troublesome operations of disassembling and reassembling the main core and setting the main core in the molding machine have to be repeated consecutively on each occasion of the alteration of the type to be manufactured, so that the operating efficiency declines appreciably. Moreover, as the kinds of main cores to be prepared increase, the facilities cost also increases, so that there has been a problem in that a higher production cost is entailed. [Disclosure of the Invention] Accordingly, the present invention has been devised in view of the above-described problems, and its object is to provide a mold for molding a reel lock member which makes it possible to improve the operating efficiency in the manufacture and curtail the manufacturing cost. The above-described problems of the present invention can be overcome by a mold for molding a reel lock member which includes : a retaining pawl for locking the rotation of a reel by engaging with engaging teeth of a magnetic tape reel; a sliding body portion slidable between a reel locking position at which the retaining pawl is engaged with the engaging teeth and "a reel unlocking position at which the engagement is released; and a flexible hinge portion provided between the retaining pawl and the sliding body portion, the mold comprising: a main core; and a slide core movable relative to the main core and having a portion for forming at least part of the hinge portion in such a manner that a thickness of the hinge portion is varied by changing a positional relationship between the main mold and the slide core. In the above-mentioned mold, it is preferable that a parting line between the main core and the slide core is located at the hinge portion. In accordance with the present invention, a cavity can be changed by fitting a slide core corresponding to the molding thickness of the hinge portion, and it is possible to mold a desired reel lock member. Accordingly, since it is unnecessary to set main cores of the mold for each type, it is possible to improve the operating efficiency in the manufacture and reduce the manufacturing cost. [Brief Description of Drawings] Fig. 1 illustrates a mold for molding a reel lock member in accordance with an embodiment of the present invention; Fig. 2 illustrates a slide core of the mold for molding a reel lock member in accordance with another embodiment of the present invention; Fig. 3 illustrates an internal structure of a conventional magnetic tape cassette; Figs. 4(a) and 4(b) respectively illustrate a front elevational view and a side elevational view of a reel lock member; and Fig. 5 illustrates a conventional mold for molding a reel lock member. [Best Mode for Carrying Out the Present Invention] Hereafter, referring to the accompanying drawings, a detailed description will be given of the embodiments of the present invention. It should be noted that since the shape of the reel lock member is identical to the one shown in Figs. 4(a) and 4 (b) , a description thereof will be omitted. Fig. 1 shows a mold for molding a reel lock member in accordance with an embodiment of the present invention. As shown in Fig. 1, a mold 1 for molding a reel lock member in accordance with this embodiment is comprised of a fixed main core 2 and a movable slide core 3. The main core 2 and the slide core 3 are disposed in face-to-face relation so as to allow the releasing and clamping of the mold, and define the cavity 5 when the mold is set in a clamped state. When the mold is set in the clamped state, a molten resin is injected and charged under pressure into the cavity 5, ad the resin is then allowed to cool and solidify, thereby molding the reel lock member 30. The parting line between the main core 2 and the slide core 3 is located at the hinge portion 35 of the reel lock member 30. When the slide core 3 is slid to set the mold in the clamped state, and the molten resin is charged under pressure into the cavity 5 and is allowed to cool and solidify, the hinge portions 35 and 36 of the reel lock member 30 are formed as shown by the broken lines in Fig. 1. Unlike the conventional arrangement, the slide core 3 performs its role of forming the spring engaging portion 37 (shown in Figs. 4 (a) and 4 (b) ) of the reel lock member 30 and also performs its role of forming the hinge portions 35 and 36. Further, when it is necessary to alter the molded thicknesses of the hinge portions 35 and 36 in-correspondence with appropriate values for locking the reels, it suffices if the slide core 3 is fitted after being changed appropriately. That is, if, for example, there has arisen a need to make the thicknesses of the hinge portions larger than those of the aforementioned hinge portions 35 and 36, it suffices if, as shown in Fig. 2, thickness forming portions 7a and 7b of a slide core 7 are made smaller than the thickness forming portions of the aforementioned slide core 3. As a method of providing a slide core for changing the thicknesses of the thickness portions to be molded, for example, a method is conceivable in which hinge-thickness forming portions 3a and 3b of the aforementioned slide core 3 are cut to desired dimensions, i.e., a method in which the slide core is remodeled, and a method in which a slide core is fabricated separately in correspondence with the thicknesswise dimension. In any case, the thicknesses of the hinge portions of the reel lock member can be altered simply by changing the slide core. Accordingly, it is possible to improve the operating efficiency in the manufacture and reduce the manufacturing cost. It should be noted that because of the need to form the spring engaging portion on the reel lock member, the sliding direction of the slide core for forming the hinge portions should preferably be in the same direction as the sliding direction of the slide core for forming the spring engaging portion. If such an arrangement is adopted, the slide core for forming the hinge portions and the slide core for forming the spring engaging portion can be formed integrally. However, in the case of a reel lock member having a structure in which the spring engaging portion is not provided, the sliding direction of the slide core may be set in the thicknesswise direction of the hinge portion or in a direction perpendicular to that thicknesswise direction. [Industrial Applicability] As described above, in accordance with the ' present invention, since the portion of the mold for forming at least the hinge portion is a slide core, and a slide core corresponding to the molding thickness of the hinge portion is fitted to effect injection molding, the molding thickness of the hinge portion can be changed by means of the slide core, and it is unnecessary to set main cores of the mold for each type. Accordingly, it is possible to improve the operating efficiency in the manufacture and reduce the manufacturing cost. While there has been described in connection with the preferred embodiment of the invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from the invention, and it is aimed, therefore, to cover in the appended claim all such changes and modifications as fall within the true spirit and scope of the invention.

Claims: CLAIMS 1. A mold for molding a reel lock member which includes : a retaining pawl for locking the rotation of a reel by engaging with engaging teeth of a magnetic tape reel; a -sliding body portion slidable between a reel locking position at which said retaining pawl is engaged with said engaging teeth and a reel unlocking position at which the engagement is released; and a flexible hinge portion provided between the retaining pawl and the sliding body portion, said mold comprising: a main core (2); and a slide core (3) movable relative to said main core (2) and having a portion for forming at least part of said hinge portion. 2. The mold according to claim 1, in which a parting line between said main core and said slide core is located at said hinge portion. 3. The mold according to claim 1, in which said reel lock member further includes a spring (78) for urging said reel lock member toward said reel locking position and said sliding body portion includes a spring engaging portion (37) for receiving said spring, wherein said slide core has a function for forming said spring engaging portion and said hinge portion. 4. The mold according to claim 1, in which in such a manner that a thickness of the hinge portion is varied by changing a positional relationship between said main mold an said slide core . 5. The mold according to claim 1, in which in such a thickness of the hinge portion is varied by changing a configuration of a hinge forming portion (3a, 3b) of said slide core . 6. The mold according to claim 1, in which a thickness of the hinge portion is varied by machining a hinge forming portion (3a, 3b) of said slide core. 7. The mold according to claim 1, in which a thickness of the hinge portion is varied by replacing said slide core with another slide core having a hinge forming portion a configuration of which is different from that of said slide core.

Inventors: ASHIKAWA TERUO, ASHIKAWA, TERUO
Applicants: ASHIKAWA TERUO, FUJI PHOTO FILM CO LTD, ASHIKAWA, TERUO, FUJI PHOTO FILM CO., LTD.
Application year: 1998
Main classification: B29C33
IPC codes: B29C33, B29C45, G11B23