Apparatus for heating workpieces to bond the same

An apparatus for heating workpieces to bond the workpieces together, comprising:

• a workpiece rest;
• an electrode unit including a first electrode rod and a second electrode rod, the first electrode rod being capable of holding the workpieces at one end thereof in cooperation with the workpiece rest and the first electrode rod having another end, the second electrode rod having one end disposed in contact with one end portion of the first electrode rod and having another end, the first and second electrode rods each having a predetermined contact surface at which the first and second electrode rods contact each other;
• cooling means for cooling the first and second electrode rods with a coolant;
• current supply means connected to said another end of each of the first and second electrode rods, the current supply means supplying a predetermined electric current to the contact surfaces of the first and second electrode rods, to cause the first and second electrode rods, which are cooled by the cooling means, to generate heat by means of contact resistance at the contact surfaces;
• actuating means for moving the electrode unit toward and away from the workpiece rest, the workpieces being held between said one end of the first electrode rod and the workpiece rest with a predetermined force when the electrode unit is moved to the workpiece rest;
• and
• control means for controlling supply of the electric current from the current supply means to the first and second electrode rods in accordance with movement of the electrode unit when the electrode unit is moved toward the workpiece rest by the actuating means;
• said control means comprising:
• a sensor for outputting a detection signal when a distance between said one end of the first electrode rod and the workpieces on the workpiece rest becomes equal to a predetermined distance while the electrode unit is moved toward the workpiece rest;
• and
• first switch means for initiating the supply of electric current from the current supply means to the first and second electrode rods to cause the first and second electrode rods to generate heat when said first switch means is supplied with the detection signal from the sensor.