1. Field of the Invention
The present invention relates to a tape cassette for use in a magnetic recording and reproducing device such as a videotape recorder and more particularly to a tape cassette having a mouth capable of accommodating a head drum therein and a front lid that can be opened to admit the head drum and then closed, the head drum then being contained within the mouth and a magnetic tape being wound around the head drum. A magnetic recording and reproducing device that employs the tape cassette may have a low profile, since the lid in its closed state does not protrude in the height or thickness dimension of the tape cassette.
2. Description of the Prior Art
There have been proposed tape cassettes for use in magnetic recording and reproducing devices including video tape recorders (VTRs) and the like, the tape cassettes being designed particularly for recording information during a relatively short period of time. The proposed tape cassettes have a cassette housing that accommodates a magnetic tape wound in coils of small diameter, thereby enlarging a mouth in which a head drum can be inserted, so that the magnetic recording and reproducing device may be reduced in size. Reference should be made to Japanese laid-open patent publication No. 60(1985)-171684 and Japanese utility model application No. 62(1987)-14573 filed by the assignee of the present application.
One such tape cassette will briefly be described with reference to FIGS. 9, 10, 11A and 11B. The tape cassette has a cassette housing 51 comprising an upper portion 52 and a lower portion 53 joined together. The upper and lower housing portions 52, 53 accommodate therein a pair of rotatable tape reels 54, 55 with a magnetic tape T wound therearound. The magnetic tape T has a portion unreeled from the tape reels 54, 55 and guided by guides 56a, 56b disposed in spaced positions at the front of the lower housing portion 53, the unreeled tape portion being kept taut and exposed in a front opening in the cassette housing 51. The cassette housing 51 has a mouth (opening) 57 formed in a lower panel of the lower housing portion 53 between and somewhat forwardly of a position between the tape reels 54, 55.
The diameter of the tape reels 54, 55 is smaller than the reel diameter of a conventional, standard tape cassette, and therefore the mouth 57 is correspondingly larger.
A front lid 58 is mounted for angular movement in a vertical plane at the front of the cassette housing 51 by laterally spaced shafts 59 to selectively open and close the front opening of the cassette housing 51. When the front opening of the cassette housing 51 is closed by the front lid 58, the front lid 58 protects the face of the magnetic tape T, which extends under tension between the guides 56a, 56b. When the tape cassette is not in use, the front lid 58 is closed to cover the face of the magnetic tape T. When the tape cassette is in use, the lid 58 is turned upwardly to expose the magnetic tape T at the front of the cassette housing 51.
A back lid 60 for protecting the back of the magnetic tape T is disposed behind the front lid 58. The back lid 60 has shafts 61 on respective opposite side edges thereof, the shafts 61 being pivotally supported by respective supports 62 which project from the rear surface of the front lid 58. The back lid 60 is thus angularly movably coupled to the front lid 58. The back lid 60 also has engaging pins 63 projecting from respective opposite ends thereof. The engaging pins 63 are movably received in respective cam grooves 65 defined in the inner surfaces of vertical walls 64, respectively, which are located in laterally spaced positions at the front of the lower housing portion 53. When the front lid 58 is opened or closed with respect to the cassette housing 51, the engaging pins 63 are guided by and along the cam grooves 65 to cause the back lid 60 to be opened or closed in coordination with the front lid 58.
When the tape cassette is in use, the front lid 58 is opened, and a head drum 71 and various tape transport members 72 including an impedance roller 73, tape guides 74, 75, 76, loading posts 77, 78, a capstan 79, and a pinch roller 80 are inserted into the mouth 57. The magnetic tape T is now wound or loaded around the head drum 71 for recording and reproducing signals on the magnetic tape T.
Since the tape reels 54, 55 are smaller in diameter and the mouth 57 is correspondingly larger, the head drum 71 and the tape transport members 72 can be inserted deeply into the cassette housing 51. As a result, the magnetic recording and reproducing device can be reduced in size.
Although employment of a magnetic tape cassette of the type described above makes it possible to insert the head drum and other members deeply into the mouth, signals are conventionally recorded on and reproduced from the magnetic tape while the lids are open. In the open position, the lids protrude well beyond the contour that the cassette housing has when the lids are in the closed position. Recording or reproducing signals on or from the magnetic tape when the lids are in the open position therefore imposes a severe limitation on efforts to make the magnetic recording and reproducing devices more compact.
More specifically, when the lids are open, the entire thickness of the tape cassette is increased by a dimension h (FIG. 11B), which corresponds to the raised portion of the lids. The increase in the thickness of the tape cassette presents an obstacle to attempts to make the magnetic recording and reproducing device lower in profile. One solution would be to close the lids after the tape has been loaded around the head drum, thereby eliminating any increase in the thickness of the tape cassette. However, if the lids were to be closed after the tape has been loaded, the back lid moving in coaction with the front lid would physically interfere with the magnetic tape drawn into the mouth. Therefore, it is impossible to close the lids of a conventional tape cassette after the magnetic tape has been loaded.