Patent ID: 7926168

Claim:
A method of manufacturing a coil with a polygonal cross section, the method comprising: first winding a circular cylindrical coil with a cylinder axis and a circular ring cross section; and then reshaping the circular cylindrical coil into the coil having the polygonal cross section, wherein the reshaping is accomplished at least in part by inserting a plurality of fingers of an expander, each of the fingers having a portion having an axis, the axes being arranged substantially parallel to the cylinder axis, into a coil interior of the wound circular cylindrical coil for a reshaping of the wound circular cylindrical coil; wherein after the fingers have been inserted into the coil interior, the fingers make a relative movement transverse to and diverging from the cylinder axis, so that the previously circular cylindrical coil is expanded into the coil having the polygonal cross section; and wherein, after the reshaping, the coil having the polygonal cross section is subjected to elongation by further expansion.