PROBLEM TO BE SOLVED: To attain a constitution in which a carrier mechanically stops when the carrier collides against a foregoing carrier or an obstacle to enhance the reliability of control and to make complicated control needless in a device arranged in the carrier such as a carriage and switching on and off towing force for the carrier to be towed by a towing rope or to be stopped stopping the towing in the case the carrier is towed by the towing rope such as a conveyer chain.SOLUTION: A power on/off device has a base body 121 facing the conveyer chain and attached to the carriage directing in an advancing direction F1, an actuation piece 122 protruding from the base body 121 in the advancing direction F1 side and retracting to an opposite side of the advancing direction F1 by contacting a foregoing carrier or an obstacle, and an engaging piece 123 which is oscillatably arranged in the base body 121, protrudes from the base body 121 to engage with an attachment of the conveyer chain in a protruding state of the actuation piece 122, and is separated therefrom when the actuation piece 122 retracts by the disengagement of a hook 1222d thereof to be sprung up by the attachment.
