The axial direction B of the spindle 64 for supporting the movable pulleys 58 and 59 is arranged at a position rotated about the axis of the shaft relative to the axial direction of the spindle 56. The axial direction B of the spindle 64 is arranged in a state of being inclined by a predetermined angle with respect to the axial direction A when the movable pulleys 58 and 59 are in the lifted position. This allows the movable pulleys 58 and 59 to be automatically moved to a position at which no stress is applied to the first wire rope 54.