Locking device for a plug-in connection

The invention relates to a locking device for a plug-in connection between a plug and a socket. According to the invention, an actuator (4) and a blocking slide (6) are provided, wherein the actuator (4) can be rotated about an axis of rotation, the blocking slide (6) can be moved between an unlocking position and a locking position in the longitudinal direction of the blocking slide, and the actuator (4) and the blocking slide (6) are designed in such a way and interact with each other in such a way that a rotation of the actuator (4) is always accompanied by a longitudinal movement of the blocking slide (6) and vice versa, wherein a longitudinal movement of the blocking slide (6) by means of a rotation of the actuator (4) is always possible, while conversely a rotation of the actuator (4) by means of a longitudinal movement of the blocking slide (6) is possible only outside of the locking position. Thus, simple and economical axial locking that cannot be manipulated is enabled.