Ceiling conveyance system, and relay conveyance apparatus and conveyance method used therefor

1. An overhead transport system comprising:

a first traveling rail on which overhead transport vehicles that include a first hoist to transfer articles to and from a first buffer and a second buffer travel, the first traveling rail including at least a straight segment and at least a curved segment connected to the straight segment;

a second traveling rail for a local vehicle, provided below the first traveling rail, allowing the articles to pass upward and downward, including one end under the straight segment, extending straightly from the one end parallelly to an extended line of the straight segment, passing over a transfer position at a ground side, and further extending straightly to another end outside an area under the straight segment;

the first and second buffers to support the articles, provided under the straight segment and also under the second traveling rail; and

the local vehicle, traveling on the second traveling rail, and provided with a second hoist to transfer the articles between the transfer position at the ground side and the first and second buffers; wherein

the first and second buffers are slidable along a direction in a horizontal plane perpendicular to a lengthwise direction of the traveling rail for the local vehicle;

the overhead transport system further includes another first traveling rail for the overhead transport vehicles, the another first traveling rail being provided over the straight segment and being parallel to the straight segment;

the overhead transport vehicles to travel on the another first traveling rail are provided with a lateral transfer apparatus to transfer the first hoist along a direction in a horizontal plane perpendicular to a traveling direction of the overhead transport vehicles and are structured to transfer the articles to and from the first and second buffers; and

the first buffer is located at a higher position than the second buffer.

2. The overhead transport system according to claim 1 , wherein the second traveling rail is provided over the transfer position at the ground side except for an area under the straight segment.

3. The overhead transport system according to claim 1 , wherein the another end is located under the curved segment and over the transfer position at the ground side.

4. The overhead transport system according to claim 1 , wherein the first and second buffers are structured to support a plurality of the articles and extend from the one end parallelly to and under the traveling rail for the local vehicle.

5. The overhead transport system according to claim 1 , further comprising an inter-bay route including a plurality of additional traveling rails for the overhead transport vehicles such that the overhead transport vehicles travel on the additional traveling rails in a same direction; wherein

the straight segment is connected, via the curved segment, to at least one of the additional traveling rails.

6. An overhead transport system comprising:

a first traveling rail on which overhead transport vehicles that include a first hoist to transfer articles to and from a first buffer and a second buffer travel, the first traveling rail including at least a straight segment and at least a curved segment connected to the straight segment;

a second traveling rail for a local vehicle, provided below the first traveling rail, allowing the articles to pass upward and downward, including one end under the straight segment, extending straightly from the one end parallelly to an extended line of the straight segment, passing over a transfer position at a ground side, and further extending straightly to another end outside an area under the straight segment;

the first and second buffers to support the articles, provided under the straight segment and also under the second traveling rail; and

the local vehicle, traveling on the second traveling rail, and provided with a second hoist to transfer the articles between the transfer position at the ground side and the first and second buffers; wherein

the first and second buffers are slidable along a direction in a horizontal plane perpendicular to a lengthwise direction of the second traveling rail; and

the overhead transport system further comprises another first traveling rail for overhead transport vehicles, passing over the first and second buffers when laterally slid, and being parallel to the straight segment; and

the first buffer is located at a higher position than the second buffer.

7. A transport method using a first traveling rail for overhead transport vehicles including at least a straight segment and at least a curved segment connected to the straight segment, and the overhead transport vehicles traveling on the first traveling rail and including a first hoist to transfer articles to and from a first buffer and a second buffer, the method using:

a local vehicle including a second hoist to transfer the articles between a transfer position at a ground side and the first and second buffers, and to travel on a second traveling rail for the local vehicle, the second traveling rail being provided below the first traveling rail, allowing the articles to pass upward and downward, including one end under the straight segment, extending straightly from the one end parallelly to an extended line of the straight segment, passing over the transfer position at the ground side, and further extending straightly to another end outside an area under the straight segment; and

the first and second buffers to support the articles, provided under the straight segment and also under the second traveling rail; and

the method comprising:

transferring the articles by the overhead transport vehicles in the straight segment between the buffer; and

making the local vehicle transfer the articles to and from the first and second buffer, travel on the second traveling rail, and transfer the articles between the transfer position at the ground side at a position outside the straight segment; wherein

the first and second buffers are slidable along a direction in a horizontal plane perpendicular to a lengthwise direction of the traveling rail for the local vehicle;

the overhead transport system further includes another first traveling rail for the overhead transport vehicles, the another first traveling rail being provided over the straight segment and being parallel to the straight segment;

the overhead transport vehicles to travel on the another first traveling rail are provided with a lateral transfer apparatus to transfer the first hoist along a direction in a horizontal plane perpendicular to a traveling direction of the overhead transport vehicles and are structured to transfer the articles to and from the first and second buffers; and

the first buffer is located at a higher position than the second buffer.