1. Field of the Invention
The present invention relates to an information recording/reproducing apparatus which is designed to be loaded with a cartridge having an information recording medium such as an optical disk and an opto-magnetic disk, and to conduct recording and/or reproduction of information in and from such a recording medium. More particularly, the invention is concerned with an information recording/reproducing apparatus having a mechanism which acts to open and close a shutter of a cartridge in response to insertion and ejection of the cartridge.
2. Description of Related Art
One typical example of conventional disk cartridges will be explained hereinunder with reference to FIG. 1A which is a schematic perspective view of the disk cartridge in an inoperative state with its shutter 158 held in a closed position, as well as to FIGS. 1B and 1C which are schematic perspective views of the disk cartridge in operative states with its sides "A" and "B" respectively presented for recording or reproduction and with its shutter held in the open position. The cassette has two major opposite surfaces, one of which is referred to as side "A" while the other is referred to as side "B" in this specification.
As will be seen from FIGS. 1A, 1B and 1C, the disk cartridge generally designated by reference numeral 150 has a rectangular thin box-like housing 152 which accommodates an information recording medium which is, in this case, a disk. In FIGS. 1B and 1C, the surfaces of the housing 152 corresponding to the side "A" and the side "B" are represented, respectively, by 154a and 154b. Apertures 156a and 156b are formed in the surfaces 154a and 154b, respectively, of the housing 152.
The conventional disk cartridge 150 is provided with a shutter 158 which is slidable on the cartridge housing 152. As will be seen from FIG. 1A, the shutter 158 closes the apertures 156a and 156b when the cartridge is not used. When the cartridge 150 is used with its side "A" presented for recording or reproduction, the shutter 158 is moved to the position illustrated in FIG. 1B so as to open the aperture 156a. Conversely, when the side "B" is used, the shutter 158 is moved to the position illustrated in FIG. 1C so as to open the aperture 156b.
Thus, in this known disk cartridge, the direction of movement of the shutter 158 relative to the side "A" of the disk cartridge is the same as that of the shutter 158 relative to the side "B". In other words, the shutter 158 is required to move both to the right and left sides of the central closing position with respect to the housing 152 of the disk cartridge.
This inevitably limits the size of the aperture on each side of the housing 152 and requires a complicated mechanism for driving the shutter.
In particular, when an opto-magnetic disk is used as the recording medium, the disk cartridge is required to have a space large enough to accommodate a biasing magnet. Unfortunately, however, it is very difficult to obtain such a space in the conventional disk cartridge having the illustrated construction.
FIGS. 2A, 2B and 2C show a disk cartridge which also has been known, but improved to obviate the described shortcoming of the disk cartridge shown in FIGS. 1A, 1B and 1C. The disk cartridge, which is generally designated at 8, has a cartridge housing 8 and a shutter 82 which is slidable on the cartridge housing 9. When the disk cartridge 8 is not used, the shutter 82 is placed at a central shut-off position as shown in FIG. 2A. When the side "A" or the side "B" of the disk cartridge is presented for use, the shutter 82 is set at positions shown in FIG. 2B or 2C so as to allow the aperture 22a or 22b to open. It will be understood that the direction of movement of the shutter 82 with respect to the cartridge housing 8 from the central closing position shown in FIG. 2A to the opening positions shown in FIGS. 2A and 2B is the same, regardless of whether the side "A" or the side "B" is used. It will be understood that this arrangement enables the disk cartridge 8 to be designed to have an ample area of each aperture 22a, 22b.
The disk cartridge of the type shown in FIGS. 2A to 2C has been used, for instance, together with a flexible magnetic disk, and has been designed such that the shutter is automatically moved from the shut-off position and the open position in response to the action for inserting and ejecting the disk cartridge. For instance, Japanese Utility Model Laid-Open No. 101355/1983 discloses a swingable lever which is adapted to be actuated in response to the action for inserting or ejecting the disk cartridge and engageable with the shutter so as to open and close the shutter. Usually, this type of disk cartridge is used in an apparatus which is provided with independent recording/reproducing heads disposed on both sides of the disk and adapted for conducting recording and reproduction on the side "A" and the side "B" of the disk. This means that the disk cartridge 8 need not be inverted and the recording and reproduction on both sides of the disk are possible with the constant orientation, e.g., with the side A directed upward, of the cartridge.
In some cases, however, it is not advantageous that a single apparatus has two sets of recording/reproducing heads which are intended for conducting recording/reproducing on the respective sides of the disk. This is true, particularly in the case of an optical recording/reproducing apparatus, because such a type of apparatus employs a large-size and expensive optical head. Provision of a pair of such optical heads will raise the cost of the apparatus and will make it difficult to reduce the thickness of the apparatus.
The most practical method for overcoming such a problem is to invert the disk cartridge depending on the side to be used. In such a case, however, the shutter has to be moved with respect to the cartridge in different directions, depending on the side of the cartridge to be used.
For instance, if the disk cartridge is designed such that the shutter 82 is moved to the right with respect to the cartridge housing when the side "A" denoted by reference numeral 10a is presented for use as viewed in FIG. 2B, the shutter 82 has to be moved to the left with respect to the cartridge housing as viewed in FIG. 2C. Unfortunately, the known shutter operating mechanism disclosed in Japanese Utility Model Laid-Open No. 101355/1983 could not meet such a demand.