A tape cassette having front surfaces to guide a tape accommodated therein

Abstract: A tape cassette arranged such that coarse surface areas are formed on guide surfaces used to guide a magnetic tape along the external surface of the front side wall portion formed inside of a cassette lid and that the coarse surface areas are gradually reduced toward the seam 19 of upper and lower parts. Thus, when the upper and lower parts are moulded, the upper and lower parts can be removed from the metal moulds with ease. Also, build-up of static electricity can be prevented from occurring in the magnetic tape or in the upper and lower parts when the magnetic tape is transported along the guide surfaces.

Description: The present invention generally relates to tape cassettes and, more particularly, to a tape cassette in which a pair of tape reels are accommodated within a cassette casing and a magnetic tape is attached at respective ends to the reels and is wrapped about one or both of them. Such tape cassettes are now widely available as a record medium for a video tape recorder (VTR) and are described in Japanese Utility Model Laid-Open Gazette Number 63-153383. When this tape cassette is loaded on a video tape recorder, a loop of the magnetic tape accommodated within the cassette casing is pulled out and wrapped around a rotary head drum. Then, a rotary head obliquely scans this magnetic tape to perform a predetermined recording and/or reproduction on or from the tape. In a tape cassette of the so-called VHS type, in the fast forward rewind modes, a magnetic tape is withdrawn into the cassette casing and the magnetic tape is transported in such a manner as to reduce the resistance exerted upon the magnetic tape. In the fast forward or rewind mode, it is to be noted that the magnetic tape is transported at high speed in the forward direction or in the reverse direction along a guide surface formed on the outer surfaces of the front side wall portions of the cassette casing. Accordingly, it is frequently observed that, when the magnetic tape is slidably transported along the guide surface of the cassette casing, the production of static electricity causes the magnetic tape to be stuck to the guide surface of the cassette casing. To solve this problem of the prior art, it has been proposed to avoid static electricity being generated by forming very small concave and convex portions on the surface of the guide surface so as to reduce the area of contact between the tape and guide surfaces. Japanese Utility Model Laid-Open Gazette Number 63-153383, on which the preamble claim 1 has been based, describes such previously proposed tape cassette. Similarly, equivalent documents DE-A-3618498 and GB-A-2176170 disclose a tape cassette having the features of the preamble of claim 1. However, this type of tape cassette has the disadvantage that, if very small concave and convex portions are formed over the entire surface of the guide surface, when the upper and lower shells or parts forming the cassette casing are removed from metal moulds after the moulding-process, the resistance in the removal process increases considerably, thus making it impossible to remove the moulded products from the metal moulds. It is an object of the present invention to provide an improved tape cassette which can reduce or eliminate the aforementioned shortcomings and disadvantages encountered with the prior art. According to the present invention, there is provided a tape cassette comprising a cassette casing with a front surface side and made up of an upper part and a lower part which are bonded together along a seam, and in which a pair of tape reels are aligned, and a magnetic tape wrapped around the pair of tape reels and attached at each end to respective ones of the tape reels, the magnetic tape and the tape reels being accommodated in the cassette casing, the tape cassette further comprising; a cassette lid attached to the front surface side of the cassette casing so as to be openable and closable; a guide surface formed on the front surface side of the cassette casing so as to oppose the inside of the cassette lid, a run of the magnetic tape extending along the guide surface; and a coarse surface area is formed on the guide surface, in which the coarse surface area is gradually reduced in width toward the seam between the upper and lower parts. The invention will be further described by way of non-limitative example with reference to the accompanying drawings, in which:- Figure 1 is a perspective view of the external appearance of an embodiment of a tape cassette according to the present invention with its cassette lid being opened; Figure 2 is a plan view of the tape cassette of figure 1 with portions broken away and in section and further showing a tape end detection sensor system of a VTR; Figure 3 is an enlarged view illustrating a tape guide surface formed at a front side of the tape cassette according to the embodiment of the present invention; Figure 4 is a longitudinal cross-sectional view taken generally along the lines 4-4 in figure 3; Figure 5 is an enlarged front view of a modified example of tape guide surface of the present invention; Figure 6 is an enlarged front view of a further modified example of tape guide surface of the present invention; and Figure 7 is an enlarged front view of a further modified example of tape guide surface of the present invention. Referring to the drawings in detail, and initially to figures 1 and 2, a first embodiment of the tape cassette according to the present invention will be described hereinafter. It will be seen in figures 1 and 2 that this tape cassette has a cassette casing 10 which is shaped substantially as a flat rectangular solid. The cassette casing 10 is comprised of a pair of upper and lower shells or parts 11 and 12, respectively. The upper and lower parts 11 and 12 are moulded by a synthetic resin moulding-process and fastened together by some suitable means such as a bonding-process or the like. A pair of left and right tape reels 13 and 14, respectively, are accommodated within the cassette casing 10 in alignment with each other. A magnetic tape 15 is wrapped around the pair of tape reels 13 and 14 with each end of the tape being attached to a different one of the tape reels 13 and 14. In operation, the magnetic tape 15 is pulled out to the front wall side of the cassette casing 10 through opening portions 16 formed at the left and right sides of the front wall of the cassette casing 10 and extended along guide surfaces 18 formed on the surface of a front side wall portion 17. An openable and closable front lid 21 is provided at the front side of the front side wall portion 17 having the guide surfaces 18 along which the magnetic tape 15 is extended. As shown in Fig. 2, a circular opening portion 22 is formed through the bottom portion of the cassette casing 10, and a cylindrical-shaped guide portion 23 is elongated within the cassette casing 10 so as to communicate with the circular opening portion 22. When the cassette casing 10 is loaded on a video tape recorder (not shown), a lamp 24 is relatively inserted into the cylindrical-shaped guide portion 23 as shown in Fig. 2. A small aperture 26 in each side wall 5 of the cassette casing 10 allows separate light receiving elements 27 provided outside of each of the small apertures 26 to sense the tape ends in a manner known per se to those skilled in the art. The guide surface 18 of the front side wall portion 17 and along which the magnetic tape 15 is extended will be described next with reference to Figs. 3 and 4. As shown in Figs. 3 and 4, a plurality of triangular coarse surface areas 30 are formed on the guide surfaces 18. Each coarse surface area 30 is shaped as a triangle such that its triangular area is gradually reduced toward the seam 19 where the upper and lower parts 11 and 12 are bonded together. The magnetic tape 15 is transported along the guide surface 18 having the coarse surfaces 30 as shown in Fig. 4. The coarse surface 30 corresponds to the surface of the metal mold from which the upper and lower parts 11 and 12 are molded and which is obtained by forming concave and convex portions on the surface of the metal mold by treatment with chemicals. That is, when the upper and lower parts 11 and 12 are formed on the corresponding surfaces by metal molds having concave and convex portions, the coarse surfaces 30 are formed. In addition, as shown in Fig. 4, the guide surface 18 on which the coarse surface 30 is formed is formed as a gently inclined surface and its depth becomes largest at the seam 19 of the upper and lower parts 11 and 12. In the above-described arrangement, when the tape cassette shown in Figs. 1 and 2 is loaded onto the video tape recorder (not shown), the cassette lid 21 is opened as shown in Fig. 1, whereby the magnetic tape 15 extended over the guide surfaces 18 of the front side wall portion 17 is exposed to the outside. This magnetic tape 15 is pulled out by a tape pulling pin (not shown) of the video tape recorder and is wrapped around the rotary head drum (not shown) of the video tape recorder in a manner known per se to those skilled in the art. Then, the magnetic head mounted on the rotary head drum is rotated at high speed and the magnetic tape 15 is urged against a capstan by a pinch roller (not shown) and transported at constant speed, thus the predetermined recording and/or reproduction being performed. That is, in the recording mode or in the reproduction mode, the magnetic tape 15 is pulled out from the cassette casing and wound around the head drum of the video tape recorder. On the other hand, in the fast forward mode or in the rewind mode, as shown in Figs. 1 and 2, the magnetic tape 15 is transported directly along the guide surfaces 18 of the front side wall portion 17. The reason for this is to reduce the resistance applied to the magnetic tape 15 in order to move the magnetic tape 15 at high speed. In the fast forward mode or in the rewind-mode, the magnetic tape 15 is supplied from one tape reel, transported along the guide surfaces 18 of the front side wall portion 17, and is rewound by the other tape reel at high speed. To detect the tape ends, they are fixed to the tape reels 13 and 14 via transparent leader tapes so that, when the magnetic tape 15 is thoroughly rewound by the other tape reel, the light from the lamp 24 is sensed by one of the light receiving elements 27 by way of the transparent leader tape, thereby detecting the tape end. When the tape end is detected as described above, the driving of the tape reels 13 and 14 is stopped simultaneously in a manner known per se by those skilled in the art. As mentioned above, in the fast forward mode or in the rewind mode, if the guide surfaces 18 are flat, electrostatic charging tend to occur in the magnetic tape 15 or in the upper and lower parts 11 and 12. There is then the substantial possibility that the magnetic tape 15 will stick to the guide surfaces 18. However, in the cassette according to the present invention, the triangular coarse surface areas 30 are formed on the guide surfaces 18 of the upper and lower parts 11 and 12, and the points of the triangular coarse surface areas 30 are brought in contact with each other at the seam 19 of the upper and lower parts 11 and 12. In the tape cassette of this embodiment, the guide surfaces 18 of the front side wall portion 17 are gently inclined inwardly toward the seam 19 of the upper and lower parts 11 and 12 shown in Fig. 2, and the triangular coarse surface areas 30 are successively formed on the guide surface portions 18. Therefore, according to the thus arranged guide surface, electrostatic charging of the magnetic tape 15 or the upper and lower parts 11 and 12 is reduced, 20 and the magnetic tape 15 is prevented from being stuck to the guide surfaces 18. Since the coarse surface areas 30 are gradually reduced in width toward the seam 19 of the upper and lower parts 11 and 12, it becomes possible to considerably reduce the resistance of the guide surfaces 18 when the upper and lower parts 11 and 12 are removed from the metal molds as compared with the case in which the entire surface is made coarse. Accordingly, it is possible to obtain a tape cassette in which the magnetic tape 15 can be prevented from being stuck to the guide surfaces 18 and also the upper and lower parts 11 and 12 can be easily removed from the metal molds. The shape of the coarse surface area 30 formed on the guide surface 18 of the front side wall portion 17 is not limited to that of Fig. 3 and may be a trapezoidal-shape as shown in Fig. 5. Also in this case, the width of the trapezoidal-shaped coarse surface area is reduced toward the seam 19 of the upper and lower parts 11 and 12. Further, two sides of a triangular shape may be curved in an arc-fashion as shown in Fig. 6. Furthermore, as shown in Fig. 7, the coarse surface areas 30 may be shaped substantially as semicircles and their upper and lower semicircular portions may be contacted to each other at the seam 19 of the upper and lower parts 11 and 12. As described above, according to the present invention, the coarse surface areas are formed on the guide surfaces of the front side of the cassette casing and which are inside of the cassette lid, and each of the coarse surface areas is gradually reduced in width near the seam 19 of the upper and lower parts. Therefore, according to the coarse surface areas, it becomes possible to effectively prevent electrostatic charging from occurring in the magnetic tape or in the upper and lower parts when the magnetic tape is slidably transported along the guide surfaces of the upper and lower parts. In addition, since the width of each of the coarse surface areas is gradually reduced near the seam 19 of the upper and lower parts, increased resistance of the coarsened guide surfaces when the upper and lower parts are removed from the metal molds can be avoided.

Claims: A tape cassette comprising a cassette casing (10) with a front surface side and made up of an upper part (11) and a lower part (12) which are bonded together along a seam (19), and in which a pair of tape reels are aligned, and a magnetic tape (15) wrapped around the pair of tape reels (13,14) and attached at each end to respective ones of the tape reels (13,14), the magnetic tape (15) and the tape reels (13,14) being accommodated in the cassette casing (10), the tape cassette further comprising: a cassette lid (21) attached to the front surface side (17) of the cassette casing (10) so as to be openable and closable; a guide surface (18) formed on the front surface side (17) of the cassette casing (10) so as to oppose the inside of the cassette lid (21) a run of the magnetic tape (15) extending along the guide surface (18) and a coarse surface area (30) being formed on the guide surface (17); and; characterised in that the coarse surface area (30) gradually reduces in width toward the seam (19) between the upper and lower parts (11,12). A tape cassette according to claim 1, in which the guide surface (18) is inclined so as to be deeper at the seam (19) of the upper and lower parts (11,12). A tape cassette according to claim 1, in which the coarse surface area (30) is shaped as at least one area portion, gradually reducing in width toward the seam (19) of the upper and lower parts (11,12). A tape cassette according to claim 1 or 2, in which said at least one area portion is of at least approximately triangular shape gradually reducing in width toward the seam (19) of the upper and lower parts (11,12). A tape cassette according to claim 4, in which two sides of each triangular coarse surface area portion are curved as arcs. A tape cassette according to claim 3, in which there are a plurality of said area portions shaped as semicircles contacting each other at the seam (19).

Inventors: MAKINO MASAHIRO C O SONY MAGNE, MAKINO, MASAHIRO, C/O SONY MAGNETIC PRODUCTS INC.
Applicants: SONY CORP, SONY CORPORATION
Application year: 1990
Main classification: G11B23
IPC codes: G11B23