Nut runner

A nut runner apparatus for screw-coupling a nut to a bolt, the nut runner apparatus comprising:

• a nut socket into which the nut is configured to be removably inserted;
• a heating device configured to heat the nut to thermally expand the nut;
• an actuating device configured to rotate the nut socket to screw-couple the nut thermally expanded by the heating device, to the bolt;
• and
• a cooling device configured to cool the nut screw-coupled to the bolt to thermally contract the nut,
• wherein the heating device includes a power supply configured to supply power, an induction coil configured to heat the nut by electromagnetic induction using the power and a brush configured to electrically connect the power supply and the induction coil,
• wherein the brush has a first brush electrically connected to one of positive and negative electrodes of the power supply and a second brush electrically connected to the other of the positive and negative electrodes,
• wherein at least a portion of the induction coil is wound around the nut socket to rotate with the nut socket, and
• wherein the induction coil includes first and second portions provided at opposite end portions of the induction coil, the first and second portions being selectively disposed in contact with, or in non-contact with, the first and second brushes.