Abstract: Tensioning device for the energy store of an electrical switch, the energy store including a drive spring and the switch having a turn-on lock provided with a blocking latch of the turn-on lock of the switch, the device including:a rotatable drive shaft having a crank articulated to the drive spring, the drive shaft being rotatable into an end position at which the spring is tensioned and the drive shaft is supported at the blocking latch;a rotatable tensioning shaft and a displacement-producing mechanism carried by the tensioning shaft;a directional coupling device disposed on the drive shaft and coupled to the displacement-producing mechanism for rotating the drive shaft in steps in a selected direction in repsonse to rotation of the tensioning shaft;a spring member disposed for maintaining the coupling operative engagement with the displacement-producing mechanism;a setting member associated with the drive shaft for uncoupling the directional coupling device from the displacement-producing mechanism when t