Article transport facility and a method of operating the facility

1. An article transport facility comprising:

a plurality of mobile bodies movable along a single track for transporting articles;

an article storage rack disposed beside said track and including a plurality of storage units arranged vertically and in juxtaposition in a direction along said track;

a plurality of load support tables arranged in juxtaposition in the direction along said track at positions adjacent said article storage rack in the direction along said track;

a control means capable of executing an individual moving operation for controlling movements of said mobile bodies individually of each other where the mobile bodies are separated from each other;

wherein said control means executes a joint moving operation for controlling respective running of two of said plurality of mobile bodies to cause these two mobile bodies to run together provided said two mobile bodies are running in a same direction and being under normal operating conditions and provided a distance between said two mobile bodies is less than a predetermined distance;

wherein, in the joint moving operation, a first mobile body as one of said two mobile bodies which is located rearwards in the running direction pushes a second mobile body as the other of said two mobile bodies which is located forwards in the running direction; and

wherein said predetermined distance is either a distance between said two mobile bodies when these bodies are located at positions corresponding, respectively, to two of said storage units which are directly next to each other in the direction along said track, or a distance between said two mobile bodies when these bodies are located at positions corresponding, respectively, to two of said load support tables which are directly next to each other in the direction along said track.

2. An article transport facility as defined in claim 1 , wherein said control means executes said joint moving operation by causing a driving torque of a propelling wheel of said first mobile body to be greater than a driving torque of a propelling wheel of said second mobile body.

3. An article transport facility as defined in claim 1 , wherein:

each of said mobile bodies is a stacker crane including a carriage having a pair of front and rear wheels for running along said track, a lift unit vertically movable along a vertical mast erected on said carriage, and an article transfer device mounted on said lift unit;

said vertical mast is erected in an area substantially remote from an end of said carriage closer to an adjacent mobile body; and

one of the pair of front and rear wheels of said carriage, located remote from the adjacent mobile body, acts as a propelling wheel.

4. A method of operating an article transport facility, the article transport facility having a plurality of mobile bodies movable along a single track for transporting articles, and comprising:

an article storage rack disposed beside said track and including a plurality of storage units arranged vertically and in juxtaposition in a direction along said track;

a plurality of load support tables arranged in juxtaposition in the direction along said track at positions adjacent said article storage rack in the direction along said track;

a control means capable of executing an individual moving operation for controlling movements of said plurality of mobile bodies individually of each other where the mobile bodies are separated from each other;

the method comprising the steps of:

deciding to execute a joint moving operation for controlling respective running of two of said plurality of mobile bodies to cause these two mobile bodies to run together provided said two mobile bodies are running in a same direction and being under normal operating conditions and provided a distance between said two mobile bodies is less than a predetermined distance; and

executing, in response to the decision, a joint moving operation, to cause a first mobile body as one of said two mobile bodies which is located rearwards in the running direction to come into contact with and then push a second mobile body as the other of said two mobile bodies which is located forwards in the running direction;

wherein said predetermined distance is either a distance between said two mobile bodies when these bodies are located at positions corresponding, respectively, to two of said storage units which are directly next to each other in the direction along said track, or a distance between said two mobile bodies when these bodies are located at positions corresponding, respectively, to two of said load support tables which are directly next to each other in the direction along said track.

5. A method as defined in claim 4 , wherein, in the step of causing said first mobile body to push said second mobile body, causing a driving torque of a propelling wheel of said first mobile body to be greater than a driving torque of a propelling wheel of said second mobile body.

6. A method as defined in claim 4 , wherein

each of said mobile bodies is a stacker crane including a carriage having a pair of front and rear wheels for running along said track, a lift unit vertically movable along a vertical mast erected on said carriage, and an article transfer device mounted on said lift unit;

said vertical mast is erected in an area substantially remote from an end of said carriage closer to an adjacent mobile body; and

one of the pair of front and rear wheels of said carriage, located remote from the adjacent mobile body, acts as a propelling wheel, and

the step of moving said first mobile body includes a step of controlling drive of said propelling wheel.