the main ratchet gear 5 to lock the rotation of the take up shaft whereafter the pivotable cam member 15 can be pivoted clockwisely as viewed in fig3 thereby releasing the lock in the manner previously described prior to release of the lock when the ratchet lever 11 is engaged by the auxiliary ratchet gear 6 and the rear portion 11b thereof is in its raised position it strikes against the projected portion 9b of the main locking member which returns upon release usually the ratchet lever 11 is made of synthetic resin while the main locking member 9 is made of a metal and therefore if the pivotable cam member 15 is forced to pivot while portions 9b and 11b are in engagement there will be a danger of damaging the ratchet lever 11 therefore in the present invention the design is such that with the pivotal movement of the pivotable cam member 15 the ratchet lever 11 is also retracted to a position in which it is not engageable with the main locking member 9 as a structure for achieving this the bar member 10 supporting the ratchet lever 11 is supported by the side plates 2 and 3 for movement axially of the take up shaft 4 a compression coil spring 27 is provided around the bar member 10 between a snap ring.