PURPOSE: To prevent the subject double clutching by preventing backward rotations of a door shaft in the direction of focusing detection using the function of a contact cam and removing the contact restraint by the cam at a point of time when disconnection operation of the rotating clutch carried out.

CONSTITUTION: Even when a needle drive shaft 11 advancedly rotated due to a force of inertia by synchronous gearing with a discharge arm, etc., of a binding unit before disconnection of a rotating clutch 13, a rotating body 32 for restraint equipped with a contact cam 33 is rotated synchronously with the needle drive shaft 11. The contact cam 33 acts on a restraint arm 34 without delay from returning of a door 6 therefor.