120 is converted into opposing translational movements of the shutters 130 130 u2032 in the positive and negative z direction through the engagement of the bezel 39 s teeth 121 in the racks 131 131 u2032 of the shutters 130 130 u2032 the shutters are thereby shifted to their open position to prevent the closure device 100 from being opened by misuse without a plug by rotating the rotary bezel by hand or with a tool the rotary bezel 120 tapers off on the inside contour of the through opening 126 to be very narrow the rotary bezel therefore provides scarcely a surface for a finger or a tool and can be safely operated only by the front end of a plug that exactly matches to the inside contour to further prevent unauthorized operation of the rotary bezel in the closed position locking means are additionally provided which will now be explained in more detail with reference to fig6 through 9 the locking means block the rotational mobility of the rotary bezel 120 and shutters 130 130 u2032 in the closed position for as long as the blocking is not released by a specific operating step merely rotating the rotary bezel 120 is therefore insufficient to open the closure device 100 in the embodiment shown in the figures the locking means are realized by arranging protrusions in the form of locking pins 123.