Abstract: A safety lock is provided with two plate assemblies, the first to be mounted on the outside of the door leaf and the second on the inside thereof. Each one of these plate assemblies comprises a first plate adapted to be placed on the side of the door leaf and having a first opening for receiving an actuating mechanism, a second opening housing a transmission gear mechanism, and corner holes for passing fasteners which hold the two plate assemblies together. A second plate is on the outer face of the first plate which comprises holes providing bearings for each gear of the transmission mechanisms as well as holes wider than the ends of the fasteners for housing the same therein. A third plate is spot welded on the outer face of the second plate and prevents access to the transmission mechanism. In the outer plate assembly, this third plate covers the ends of the fasteners and has only one hole, shaped in correspondence with the respective key hole opening of the cylinder lock.

Abstract: A bolt assembly used for locking and unlocking a door-leaf, which comprises a bolt movable from the outside by a key introduced into the barrel of a safety cylinder, the housing of the barrel comprising a flange which can be immobilized in rotation and translation by three plates fixed to the outer surface of the door by bolt means, a fourth plate covering said bolt means. This plate is treated against drilling, and the last three plates are soldered to each other and lodged in a housing.By loosening the bolt means and removing the first plate, the safety cylinder can be replaced.