Platform truck apparatus, workpiece transfer method, and workpiece conveyor equipment

1. A cart apparatus for transporting a workpiece, the cart apparatus comprising:

a cart configured to travel on a closed transportation path, the workpiece being placed on the cart;

a left sub-cart provided along a left side of the cart, and towed by the cart;

a left parts shelf placed on the left sub-cart;

a right sub-cart provided along a right side of the cart, and towed by the cart; and

a right parts shelf placed on the right sub-cart,

wherein the left parts shelf is transferred from outside of the closed transportation path to the left sub-cart, and the right parts shelf is transferred from the outside of the closed transportation path to the right sub-cart, and

wherein at least one of the left sub-cart and the right sub-cart is attached to the cart so as to be movable relative to the cart in a travel direction of the cart.

2. The cart apparatus according to claim 1 , wherein each of the left parts shelf and the right parts shelf has a caster;

upper surfaces of the left sub-cart and right sub-cart are at same level with an upper surface of the cart; and

the cart includes a guide rail configured to guide the left parts shelf when the left parts shelf moves toward the right sub-cart or guide the right parts shelf when the right parts shelf moves toward the left sub-cart.

3. A method of transferring a workpiece by loading the workpiece on or unloading the workpiece from a cart configured to travel on a closed transportation path, the method comprising the steps of:

using a cart apparatus, the cart apparatus comprising the cart, a left sub-cart provided along a left side of the cart and towed by the cart, a left parts shelf placed on the left sub-cart, a right sub-cart provided along a right side of the cart and towed by the cart, and a right parts shelf placed on the right sub-cart, the left sub-cart being attached to the cart movably in a travel direction; and

at time of transferring the workpiece, moving a sub-cart positioned outside the transportation path backward to load the workpiece on or unload the workpiece from the cart, from outside of the transportation path.

4. The method of transferring the workpiece according to claim 3 , wherein at the time of replacing a parts shelf positioned inside the transportation path, among the left parts shelf and the right parts shelf, the left sub-cart is positioned on a left side of the cart and the right sub-cart is positioned on a right side of the cart, and the parts shelf positioned inside the transportation path is moved to the sub-cart positioned outside the transportation path via the cart.