Abstract: A magneto-optic disk unit comprises a casing having an opening through which a disk cartridge is inserted into and extracted from the casing, a cartridge holder having an inserting opening for receiving the disk cartridge which is inserted through the opening of the casing, and an erroneous insertion preventing mechanism which is provided on the cartridge holder. The erroneous insertion preventing mechanism comprises an erroneous insertion preventing part which is provided in an inserting path of the disk cartridge and confronts a sloping surface of a magneto-optic disk cartridge which is inserted through the opening of the casing in a correct position for permitting the insertion of only the magneto-optic disk cartridge to a predetermined position within the cartridge holder when the magneto-optic disk cartridge is inserted in the correct position.

Abstract: A mechanism for actuating a shutter of a cartridge accommodating an optical disk so as to expose a window defined in the cartridge responsive to an insertion of the cartridge into the apparatus and so as to cover the window responsive to the withdrawal of the cartridge from the apparatus. The mechanism comprises a base provided in a body of the information recording/reproducing apparatus. The base comprises a top plate defining a space for accepting the cartridge when the cartridge is inserted into the apparatus. An arm is held in said space so as to rotate freely relative to the base in a plane generally parallel to said top plate. The arm carries a projection adapted to engage with a corresponding depression formed on a front face of the shutter located at a front side of the cartridge which enters first into the space when the cartridge is inserted. A coiled spring urges the arm in a first direction opposing the rotation of the arm when the cartridge is inserted into said space.

Abstract: A clamping mechanism for clamping a carriage of an information recording/reproducing apparatus recording and/or reproducing an information signal on and from a disk-shaped rotary recording medium accommodated in a cartridge comprises a clamping device provided movably on the body of the recording/reproducing apparatus between a clamped state in which the clamping device is engaged with the carriage so that the cartridge is fixed to the clamping device and a released state in which the clamping member is disengaged from the carriage so that the cartridge is free to move relative to the clamping device, and an actuation device provided movably on the body of the recording/reproducing apparatus between a first state and a second state such that the actuation device urges the clamping device to the clamped state when the actuation device is in the first state and the actuation device urges the clamping device to the released state when the actuation device is in the second state.

Abstract: A recording head of a magneto-optical disk apparatus for recording and/or erasing an information signal on and from a magneto-optical disk mounted on the apparatus comprises optical pickup device disposed at a first side of the magneto-optical disk for producing an optical beam such that the optical beam is focused on the first side of the magneto-optical disk, pickup feeding mechanism provided on a frame of the magneto-optical disk apparatus for moving the optical pickup device along a path extending in a radial direction of the disk, a stepping motor disposed at a second side of the magneto-optical disk, the stepping motor having a housing containing a rotor magnet and a stator winding surrounding the rotor magnet, the rotor magnet including a plurality of elongated magnetic parts magnetized to either one of the N-pole and S-pole and arranged with alternate polarity about a rotary axis of the stepping motor such that each of the elongated magnetic parts extends parallel to the rotary axis, the rotor magnet