US Patent 10186442 Carrier buffering device and storage method

The interference between overhead travelling vehicles and a local vehicle is prevented, in a situation where an overhead travelling vehicle has trouble, and the overhead travelling vehicles and the controller cannot communicate. Carriers are temporarily stored between the overhead travelling vehicles and the load port. The local vehicle travels along a travelling rail for the local vehicle located below a travelling rail for the overhead travelling vehicles and over a load port, and plural buffers are provided. The overhead travelling vehicles and the local vehicle communicate with a controller via a terminal, and a sensor is provided at a height without interference with the local vehicle and detects an element of a hoist of the overhead travelling vehicles or a carrier raised/lowered. The local vehicle is restricted from travelling when the sensor detects an element of hoist or the carrier.