Loading device and machine tool including the loading device

A method for transferring workpieces on a machine tool comprising:

• preparing the machine tool comprising:
• a loading device;
• a first main spindle and a second main spindle provided and arranged facing each other on a same axis;
• and
• a stocker portion for workpieces including first, second and third workpieces, wherein:
• the loading device comprises:
• a rail portion extending along a first horizontal axis parallel to the same axis;
• and
• a loader configured to travel along the rail portion;
• the loader consists of a traveling portion that travels along the rail portion, a pivoting portion that is pivoted with respect to the traveling portion, and an arm portion extending and contracting with respect to the pivoting portion;
• the arm portion includes a hand portion;
• the pivoting portion pivots the arm portion about a second horizontal axis parallel to the first horizontal axis;
• the hand portion includes a first hand and a second hand that are adapted to simultaneously hold up to two workpieces among the first, second and third workpieces, and a third horizontal axis orthogonal to the first and second horizontal axes in a plan view of the machine tool;
• and
• the first hand and the second hand are attached to the hand portion in a pivotable manner by 90° about the third horizontal axis so that when one of the first and second hands is facing down, the other of the first and second hands is facing horizontally,
• holding by the first hand the first workpiece received from the stocker portion;
• holding by the second hand facing horizontally the second workpiece that has been processed and is received from the second main spindle to deliver to the stocker portion while the first hand facing down is holding the first workpiece;
• and
• delivering by the first hand facing horizontally the first workpiece to the first main spindle that is vacant due to transfer of the third workpiece processed on the first main spindle to the second main spindle while the second hand facing down is holding the second workpiece;
• and
• wherein the first hand and the second hand are attached to the hand portion in a pivotable manner by 90° about the third horizontal axis so that when one of the first and second hands is facing down, the other of the first and second hands is facing horizontally.