To attain an extruding stroke sufficient for ejecting a cartridge, to prevent the popping out of the cartridge and to dispense with considerable force needed for the insertion of the cartridge by energizing an ejecting member with plural springs whose spring constants are different from each other.

The ejecting member 9, are ejecting shaft 10 and a stopper 11 are provided and the respective spring constants K1 and K2 of the first and second springs 12 and 13 are set to be K1<K2. In the early stage of the extruding stroke at the time of ejecting the cartridge, great ejecting force required for releasing the engagement of an engaging member with the cartridge 4 is generated by the spring 13 having the large spring constant K2. On the other hands, in the last stage of the extruding, stroke, a long extruding stroke by the ejecting member 9 is secured by the spring 12 having the small spring constant K1 and small ejecting force is exerted on the cartridge 4, to prevent the cartridge 4 from popping out of a cartridge chamber 1. Further, inserting force in the early stage of a stroke at the time of inserting the cartridge is made small.