Apparatus for running a wire through a pipe

An apparatus for running a coil of wire through a pipe, comprising:

• a feeding mechanism for feeding a coil of spring wire into a pipe and for retracting the coil out of the pipe while rotating the coil;
• a driving mechanism for applying a driving force resulting from the rotation of the coil to the coil in directions of movement thereof at a position where the coil is caught by the pipe both when the coil is fed into the pipe and when the coil is retracted out of the pipe;
• and
• wherein said coil is formed of a spring wire material having a rectangular or trapezoidal cross-sectional shape such that it has a dimension diametrically of the coil designated as l.sub.2 which exceeds its dimension longitudinally designated as l.sub.1 and in which the dimensions l.sub.1 and l.sub.2 are in the following relationship:
• l.sub.1 <l.sub.2 <3l.sub.1, whereby the coil spring has a geometrical moment of inertia with respect to a bending force acting diametrically of the coil which exceeds a geometrical moment of inertia with respect to a bending force acting longitudinally thereof so that the coil spring has sufficient flexibility to run through bends in the pipe without breaking or deforming.