all located on the sides of the second guides 912 parallel to the body 90 as the optical disk cartridge 10 is inserted into the optical disk drive 1 the distal end of the optical disk cartridge 10 is as shown in fig2 abutted on the ejection arm 11 when the optical disk cartridge 10 is further inserted into the optical disk drive 1 the ejection arm 11 pivots with the insertion of the optical disk cartridge 10 into the optical disk drive 1 the shutter of the optical disk cartridge 10 is opened by the first shutter opening closing piece 43 described in conjunction with fig7 and fig8 this mechanism does not fall within the scope of the present invention and a description of the mechanism will be omitted the joined state of the spindle motor assembly and sheet loader 9 attained at this time is identical to the state shown in fig2 a because the sheet loader 9 does not move when the optical disk cartridge 10 is further inserted into the optical disk drive 1 the distal end of the optical disk cartridge 10 is abutted on the timing arm 12 this causes the timing arm 12 to pivot when the optical disk cartridge 10 is fully inserted in the optical disk drive 1 the timing arm 12 fully pivots this causes one of the arms of the timing arm 12 to disengage from the engagement portion 95 of the sheet loader 9 that engages with the timing arm consequently the sheet loader 9 is moved towards the insertion port 1 a for the optical disk cartridge 10 due to tensile force exerted by the tension spring 96.