shaft 27 via a second miter gear 26 the gears 25 and 26 form a right angle gear drive if the sliding carriage 11 is to be transported from the position shown on the right hand side of the figure at the tilting device 16 to the inner tilting device 9 the rack 20 is first turned so its gripper 31 enters the slot 32 of the sliding carriage 11 as shown then the rack 20 is moved for one advance stroke by turning the pinion 29 at the limit of that stroke the rack is turned to release its gripper 31 and by a reverse stroke is brought back so its gripper can engage in the back carriage slot 36 then by a repeat forward stroke the carriage is moved further through the lock the sliding carriage travels twice the stroke of the rack 20 up to the position 34 in two steps when the sliding carriage 11 runs into the lock chamber from the right to the left the inner lock gate 38 is initially closed but can be opened after the initially opened outer lock gate 39 is closed now the inner rod drive 14 is actuated in the same manner as the outer drive 15 thereby the sliding carriage is pulled from the lock tube 3 onto the tilting device 9 the movement of the carriage in one direction of travel is thereby ended the sliding carriage 11 can be secured on the tilting device 9 so that it can be tilted for operating the securing arrangement.