Patent ID: 8404986

Claim:
A manual drive for stepped, power-free actuation of a tap changer of a tapped transformer, the manual drive comprising: a drive shaft at which a plurality of revolutions for each tap change are manually executed; a control transmission reducing these revolutions to exactly one revolution of a gear per tap change; and a locking unit having a blocking pawl that blocks the drive shaft and that is detented in a blocking groove of the drive shaft as long there is no manual unlocking by an external rotatable control part, a rotatable internal key connected with the external control part, and a pawl pivotable about an axis of rotation and having a blocking pawl cooperating with the blocking groove of the drive shaft and a blocking cam cooperating with a groove of the gear of the control transmission and such that through actuation of the internal key the pawl is so pivotable out of the locking position that the blocking pawl and the blocking cam come out of engagement with the respective grooves.