The present invention relates to a magnetic tape cassette case. More particularly, the invention relates to an improved magnetic tape cassette case in which a magnetic tape cassette for an audio machine or the like is stored.
When a magnetic tape cassette for an audio machine or the like is stored, the cassette is usually put in a magnetic tape cassette case made of plastic. The front portion of the cassette has an opening into which the magnetic head of the record/playback apparatus is inserted. A magnetic tape is provided in the cassette arranged so that the tape extends along the opening of the front portion of the cassette. The cassette case is used to prevent dust from entering the cassette through the front opening thereof and to protect the cassette and the magnetic tape at the opening.
FIG. 1 shows the basic constitution of a conventional cassette case 31. The case 31 includes a lid 32 having a pocket 34 into which a cassette 20 is inserted, and a body 35 having a pair of rotation-preventing projections 7 on which the shaft insertion holes 22 of the cassette are fitted. Pins projecting from the insides of the right and left portions of the body 35 are fitted in through-holes of the right and left portions of the lid 32 at the pocket 34 thereof so that the lid and the body are pivotally coupled to each other so that they can be opened and closed with respect to each other. Since the distance between the covering portions 33 and 36 of the case 31, which face the observe and reverse sides of the cassette 20, is set to correspond to the thickness of the thick part 21 of the cassette, the thickness l.sub.1 of the case is made considerably larger than that l.sub.2 of the other portion of the cassette. For this reason, it takes a considerably larger space to store the cassette 20 in the case 31 than to store the cassette without placing the cassette 20 in a case. As a result, if it is desired to store as large a number of the cassettes 20 as possible is stored in a limited space such as the interior of a motor vehicle, the cassettes are often intentionally not put in cases. However, if the cassette 20 is stored without being put in a case, dust is more likely to enter the cassette, promoting deterioration of the record/playback properties of the magnetic tape of the cassette.
The present applicant earlier proposed cassette cases of a smaller thickness, as disclosed in U.S. Pat. Nos. 4,648,507 and 4,627,534. Each of these cases has recesses in which the thick portion of a cassette is accommodated. For this purpose, the front opening of the cassette is located at the edges of the case which open and close, which is reverse to the conventional cassette case shown in FIG. 1.
The improved cassette case 11 disclosed in U.S. Pat. No. 4,627,534 will be described in more detail with reference to FIG. 2. In the case 11, a lid 12 having a pocket 14 and a body 15 are pivotally coupled to each other in the same manner as the cassette case shown in FIG. 1. The covering portion 13 of the lid 12 which faces the obverse or reverse side of the cassette has a recess 18a in which the thick portion 21 of the cassette, in which is formed the front opening of the cassette, is accommodated. Another recess 18b to accommodate the thick portion 21 of the cassette is formed in the covering portion 16 of the body 15 which faces the reverse or obverse side of the cassette. A pair of rotation- preventing projections 7 on which the reel shaft insertion holes 22 of the cassette are fitted are provided in the same manner as the cassette case shown in FIG. 1. The recesses 18a and 18b are provided in the inside of the case 11 facing each other. Each of the recesses 18a and 18b is shaped as a trapezoid, for example, diverging toward the opening and closing edges of the lid 12 and the body 15 to accommodate the thick portion 21 of the cassette. The right and left portions 19 of the body 15 and those of the lid 12 at the pocket 14 thereof have hollows and projections on the mutually facing sides of the portions so that when the lid and the body are closed relative to each other, the projections are fitted in the hollows to prevent the lid from unexpectedly opening while the cassette is stored in the case 11. When the lid 12 and the body 15 are in the closed position, the distance between the covering portions 13 and 16 of the lid and the body is just slightly larger than the thickness l.sub.2 of the cassette 20 except for the thick portion 21 thereof, and the distance between the recesses 18a and 18b is just slightly larger than the thickness l.sub.5 of the thick portion.
The thickness of the improved cassette case shown in FIG. 2 is thus made considerably smaller than that of the cassette case shown in FIG. 1, reducing the required storage space and improving the portability of the cassette and case. However, as shown in FIG. 3, when the reduced-thickness case 11 accommodating the cassette 20 is carried or transported, the thick portion 21 of the cassette is likely to come into contact with the case at the recesses 18a and 18b to make scratches in the case because the distance between the recesses is not much larger than the thickness l.sub.5 of the thick portion. Particularly, during the formation of the scratches chipping dust is likely to be produced due to the mutual rubbing of the thick portion 21 of the cassette 20 and the case 11 at the peripheral portions 18c and 18d of the recesses 18a and 18b near the front wall 10 of the case. Such dust can enter the cassette through the front opening in the thick portion and cling to the surface of the magnetic tape in the cassette, causing dropout in recording on the tape.
These cassette cases are usually manufactured using an injection molding process. Since the recess 18a of the lid 12 having the pocket 14 is formed in the lid in the manner of an undercut portion as shown in FIG. 4, a slide core 103 movable in the direction of the thickness of the covering portion 13 of the lid 12 is required to form the recess. The lid 12 is molded through the use of three movable dies 101, 102 and 103 and a fixed die 100, which constitute a complicated die assembly. Since the slide core 103 for forming the recess 18a of the lid 12 is moved in such a direction as to expand the molding cavity defined by the dies and the movable die 102 corresponding to the inside surface of the pocket 14 of the lid is thereafter moved along the inside surface of the covering portion 13 of the lid, the molding process is lengthy, making the productivity for the case 11 lower than that for the cassette case 31 shown in FIG. 1. Moreover, frequent maintenance of the dies 100, 101, 102 and 103 is required because the constitution of the dies is complicated.