Workpiece conveying apparatus for a pressing machine with two robots

A workpiece conveying apparatus for a pressing machine, comprising:

• two robots arranged symmetrically with respect to an XZ plane passing a workpiece conveying center, each of the two robots comprising:
• a raising and lowering frame supported on a stationary frame so as to be movable in a Z-axis direction that is an up-and-down direction, the stationary frame being mounted to extend along a Y-axis direction that is a width direction orthogonal to an X-axis direction that is a workpiece conveying direction of a passage space for conveying a workpiece;
• a first arm supported at a proximal end side thereof by the raising and lowering frame through a first joint so as to be freely rotatable within a horizontal plane;
• a second arm supported at a proximal end side thereof by a distal end side of the first arm through a second joint so as to be freely rotatable within the horizontal plane;
• a first arm driving mechanism configured to drive the first arm to rotate about the first joint with respect to the raising and lowering frame;
• and
• a second arm driving mechanism configured to drive the second arm to rotate about the second joint with respect to the first arm;
• two raising and lowering mechanisms arranged to correspond to the two robots, respectively, and configured to enable the corresponding raising and lowering frames to mutually independently move in the Z-axis direction, so that the two robots moves in the up-and-down direction independently of each other with respect to the stationary frame;
• a cross arm configured to couple distal ends of second arms arranged on both sides across the XZ plane so as to be freely rotatable within the horizontal plane through a third joint and freely rotatable within a vertical plane through a fourth joint while a plane within which the first and second arms rotate is kept in the horizontal plane, the fourth joint is an axle bearing which has a rotation axis crossing a longitudinal-length direction of the cross arm;
• and
• a workpiece holding unit connected to the cross arm and configured to releasably hold the workpiece;
• wherein respective rotation planes of the first and second arms are respectively kept in the horizontal plane, even when the cross arm is inclined in a YZ plane by changing mutually independently the respective heights in the Z axis direction of the two robots.