There is known a configuration in which a transfer apparatus for transferring articles is connected to a ceiling traveling vehicle that travels a track installed on the ceiling. This transfer apparatus includes a main body connected to the ceiling traveling vehicle and a moving unit capable of moving to a side of the main body in the traveling direction of the ceiling traveling vehicle. The transfer apparatus is configured to move the moving unit using a drive mechanism, such as a belt mechanism or gear mechanism, so that the moving unit protrudes from a side of the main body and to transfer an article in this state. After transferring the article, the transfer apparatus returns the moving unit to the main body using the drive mechanism.
If the belt is cut or the gear is disengaged in this transfer apparatus, the moving unit may inadvertently rush out to the other side of the maim body and interfere with an adjacent structure, such as another ceiling traveling vehicle or column. To prevent such inadvertent rush-out of a moving unit, there have been proposed engaging apparatuses that, when a ceiling traveling vehicle is traveling, engage a moving unit with a main body and, when the ceiling traveling vehicle is stopped in order to transfer an article, disengage the moving unit from the main body in order to move the moving unit to a side of the main body, for example, as shown in Patent Literature 1.