PURPOSE: To prevent defects such as the cracking on the surface of a cord member and the deterioration of its material by heating a planar steel, hot- bending a top force and a bottom force and conducting dipping, heating and leaving under a cooled state in heating and cooling water tanks in succession.
CONSTITUTION: A planar steel 2 is heated, and hot-bent by a projecting arcuate top force 6 and a recessed arcuate bottom force 7, thus forming a cord material 8. The cord material 8 is left as it is cooled up to room temperature in atmospheric air, heated, dipped in a cooling water tank, pulled up from the cooling water tank, further heated and left as it is cooled in atmospheric air. Beveling cutting sections 12 in the cord material 8 to which heat treatment is completed are removed, thus obtaining a large-sized arm 9. The large-sized arms 9 are held mutually from both ends centering around a rack material 13, and joining sections among the large-sized arms 9 and the rack material 13 are welded, thus forming a rack-and-cord. Accordingly, defects such as the cracking of the surface and the deterioration of the material can be prevented.
IDA NORIAKI
WATARI HIDEJI
