In a locking device for the fixation of a lid (1) on an opening (8) of a pressure container with at least two locking segments (5) displaceable at right angles to the axis of the opening 98), which segments (5) bear protrusions (6) and groove-like recesses along their circumference, which in the locked position cooperate with recesses (7) and protrusions along the brim of the opening (8), the displacement actuator (4) of the segments (5) is linked to the segments (5) and to at least one point of application that is on the lid (1) or on a member (3) connected to the lid (1). The segments (5) are arranged in the direction of the circumference of the lid (1) and are pivotably supported on the lid (1) by a swivel arm (16), separate from the displacement actuator (4), being interposed.