Patent ID: 6901782

Claim:
An apparatus for forming a modified cross-section wire material used as piston rings comprising: at least one forming unit ( 15 ), wherein said forming unit ( 15 ) is constructed of a non-powered pre-stage four-roll turks-head stand ( 16 ) and a powered post-staged four-roll turks-head stand ( 17 ) disposed in tandem and downstream of said non-powered pre-stage four-roll turks-head stand ( 16 ) wherein said cowered post-staged turks-head stand ( 17 ) includes a pair of vertically arranged forming rolls ( 18 ) and a pair of laterally arranged forming rolls ( 19 ); and, only one pair of said two pairs of said forming rolls ( 18 , 19 ) is powered to perform a rough rolling operation of said wire material, and wherein at least one pair of driving-roll of said forming rolls ( 18 , 19 ) of said powered post-staged turks-head stand ( 17 ) is constructed of a large-diameter roll having a diameter equal to or larger than 70 times as much as a thickness of said wire material.