Lock with a lock cylinder for a floor lid of a motor vehicle

The application relates to a lock having a closing cylinder for a drop door of a motor vehicle, with the free end of the rotor being provided with a locking projection. To enable the drop door to be slammed shut even when the lock is closed, a ring is provided which can be turned through a certain angle about the rotor longitudinal axis against spring force and is mounted on the end of the rotor remote from the insertion opening for the key. A rotary latch body which is acted upon by a spring is coupled to the ring in hinged manner. The rotary latch body, in a base area, has a central passage opening for the free end of the rotor and a recess for the passage of the locking projection at a certain angular position. The rotary latch body has a projection with a bevelled side face which interacts as a mating piece with an inclined plane fixed to the vehicle to be movable against spring force when the door is slammed shut, to then be returned by the spring force to the locked position.