Ceiling traveling vehicle and method for preventing protrusion from ceiling traveling vehicle

A method for preventing projection from an overhead travelling vehicle including a travelling unit, an elevation device lifting and lowering articles, and a lateral movement mechanism including a base member supported by the travelling unit and a moving unit laterally moving while supporting the elevation device, the method comprising:

• a step for moving the moving unit between a state in which the moving unit laterally protrudes from the travelling unit and a state in which the moving unit is retracted to a position under the travelling unit;
• and
• a step for engaging the moving unit or the elevation device with the base member or the travelling unit in the state in which the moving unit is retracted to the position under the travelling unit,
• wherein the moving unit or the elevation device has a member provided with a hole for engagement, and
• the engagement device includes at least one pin that is advanced and retracted between a state in which the pin is engaged in the hole and a state in which the pin is disengaged from the hole, and a mechanism for advancing and retracting the at least one pin,
• wherein the moving unit includes a top unit supporting the elevation device and a middle unit disposed between the base unit and the top unit,
• each of the top unit and the middle unit has the member provided with a hole for engagement, and
• the engagement device engages and disengages the at least one pin in and from the respective holes for engagement of the top unit and the middle unit.