Patent ID: 7383751

Claim:
An articulated robot comprising: a base unit having a predetermined first pivotal axis and capable of turning about the first pivotal axis; a first arm having a base part fixedly connected to the base unit, and a front part having a second pivotal axis parallel to the first pivotal axis; a second arm having a base part connected to the front part of the first arm, and a front part having a third pivotal axis parallel to the first pivotal axis, and capable of turning about the second pivotal axis; a third arm having a base part connected to the front part of the second arm, and a front part having a fourth pivotal axis parallel to the first pivotal axis, and capable of turning about the third pivotal axis; an interlocking means interlocking the second arm and the third arm such that the third arm turns about the third pivotal axis relative to the second arm in one of opposite directions through an angle twice as large as an angle through which the second arm turns about the second pivotal axis relative to the first arm in the other direction; a base unit driving means for turning the base unit about the first pivotal axis; and an arm driving means for turning the second arm about the second pivotal axis; wherein a distance between the first pivotal axis and the second pivotal axis is equal to a distance between the second pivotal axis and the third pivotal axis; wherein respective effective lengths of the first arm, the second arm and the third arm are selectively determined such that a radius of a circle occupied by the first, second and third arms and having its center at the first pivotal axis is at a minimum in a state in which the first arm, the second arm and the third arm are in angular positions such that a direction from the base part toward the front part of each of the second arm and the third arm is opposite to a direction from the base part toward the front part of the first arm; and further comprising: an end effector that comes into contact with a workpiece, having a base part connected to the front part of the third arm, and a front part; the end effector having a length such that the end effector is contained within the circle when (1) the radius of the circle is at the minimum in the state where the first arm, the second arm and the third arm are in angular positions such that the direction from the base part toward the front part of each of the second arm and the third arm is opposite to the direction from the base part toward the front part of the first arm, and (2) the end effector is in an angular position such that the direction from the base part of the end effector toward the front part of the end effector is the same as the direction from the base part of the first arm toward the front part of the first arm; an end effector driving means for turning the end effector about the fourth pivotal axis; and the first arm is capable of turning about the first pivotal axis at least 180 degrees.