Single side heating apparatus

A single side heating apparatus equipped with a pair of electrodes for heating a workpiece from one side of the workpiece, the apparatus comprising:

• a base portion;
• the pair of electrodes each having a contact portion configured to contact with the workpiece in one direction, the contact portion having a single continuous contact surface or a plurality of spaced-apart contact surfaces;
• an electrode holder, to which the pair of electrodes are fixed;
• and
• a four-bar linkage provided between the base portion and the electrode holder and configured to rotate to tilt the electrode holder around an axis orthogonal to the one direction by a reaction force received by the electrodes from the workpiece,
• wherein the four-bar linkage comprises a first link located closer to the electrode holder, a second link located closer to the base portion, a third link, and a fourth link, the first link being shorter than the second link, and the third link and the fourth link being equal in length.