Abstract: A direct resistance heating apparatus includes first and second electrodes arranged with a space provided therebetween, a power supply electrically connected to the electrodes, an electrode moving mechanism configured to move, in a state in which the electrodes are in contact with a workpiece and in a state in which current is applied from the power supply to the workpiece through the electrodes, at least one of the electrodes along an opposing direction in which the electrodes are opposed to each other, first and second holders configured to hold the workpiece such that, in a state in which the at least one of the electrodes is moved, a heating target region of the workpiece located between the electrodes is held between the holders in the opposing direction, and a holder moving mechanism configured to move at least one of the holders to pull the workpiece along the opposing direction.

Abstract: A direct resistance heating apparatus includes a first electrode and a second electrode, and a moving mechanism configured to move at least one of the first electrode and the second electrode. A direct resistance heating method includes steps of providing a workpiece having a heating target region, a resistance of which per unit length in one direction thereof varying along the one direction, placing a first electrode and a second electrode on the heating target region, and moving at least one of the first electrode and the second electrode such that a time during which the electric current is applied to each part of the heating target region is adjusted in accordance with a change of the resistance per unit length, thereby heating the workpiece such that the each part of the heating target region is heated to a temperature within a target temperature range.

Abstract: An apparatus for manufacturing a core wire for use in laying optical fibers over a long distance produces a plurality of continuous corrugated deep grooves in a wire that are capable of holding therein the optical fibers longitudinally along the peripheral surface of the wire. An endless raw wire material of circular cross section is formed by the apparatus into a wire of square cross section through plastic processing and thereafter the wire is formed into a core wire of a flower patterned cross section with a plurality of petals having corrugated deep grooves in the periphery thereof continuously longitudinally thereof through a rolling device. In addition, the core wire so constructed is formed into a core wire with spiral corrugated deep grooves formed in the peripheral surface thereof. The rolling means has forming rolls equal in number to the number of ridges of the square wire, and each such roll having two perfect corrugated convex portions formed widthwise on the peripheral surface thereof.