PURPOSE: To efficiently transfer the power from the 1st gear to the 2nd gear rotated with the power at the drive source side and to secure the discharge operation when the cassette is discharged by composing to install the coil spring coiled for the cylinder part of the 2nd gear and coupling the end to the 1st gear.

CONSTITUTION: When a gear 64 is rotated in the clockwise direction by the power at the drive source side when a cassette 2 is discharged, a flange 60 and a coil spring 62 are rotated in one body in the clockwise direction, the slip torque is generated with the friction force located between a coil spring 62 and a cylinder part 65, a cylinder part 65 is rotated in the clockwise direction in one body with a gear 59 and a rack 29 is sent in the arrow B direction. Since a coil spring 62 is composed to rotate for a cylinder part 65, the transfer efficiency of the torque is larger, and consequently the slip torque increases and a gear 59 can be more securely rotated.