Robot system

Claim 1

A robot system for use with a machine tool having a spindle, comprising: a robot having a body for being mounted on the machine tool, an arm pivotally mounted on said body and rotatable in a plane transverse to an axial direction of the spindle of the machine tool, and a hand mounted on a distal end of said arm for gripping a workpiece and transferring the workpiece to the machine tool; a workpiece feeder disposed adjacent to said robot and movably supporting a succession of pallets for carrying unmachined and machined workpiece thereon, said workpiece feeder including a first mechanism for moving said pallets along a path on said workpiece feeder and for positioning said pallets, one at a time, in a first position in which an unmachined workpiece can be picked up from the pallet by said hand or a machined workpiece can be unloaded from said hand onto the pallet, and a second mechanism for moving the pallet toward said hand in said first position for allowing said hand to pick up the unmachined workpiece and unload the machined workpiece, and for moving said pallet away from said hand, and a DC motor for driving said second mechanism; a first circuit for controlling said DC motor; and a second circuit for controlling said first circuit on the basis of a distance L of movement of said pallet toward and away from said hand, said distance L being derived from the number N which is the maximum number of workpieces carried on said pallet, the distance Zn that said pallet with the N workpieces carried thereon moves until an uppermost workpiece reaches a second position in which the uppermost workpiece can be picked up by said hand, the distance Z1 that said pallet moves until a lowermost workpiece reaches said second position, and the number m of workpieces currently being carried on said pallet, said second circuit being capable of storing, in advance, data on said number N and said distances Zn, Z1 and monitoring said number m.