Patent ID: 7552580

Claim:
A method of producing a high quality of yarn by an iron-heating apparatus comprising a heating main body and having a twisting triangle area, wherein said method comprises the steps of: (a) guiding a yarn fiber to pass between an upper and a lower roller, wherein said yarn fiber is guided to exit at a front nip in said twisting triangle area; (b) guiding said yarn fiber to enter to a groove of said heating main body of said iron-heating apparatus; (c) heating said yarn fiber along said groove to reduce a rigidity of said yarn fiber so as to allow said yarn to be easily twisted to form an improved yarn fiber with high quality, wherein modulus of said yarn fiber is decreased after said heating so as to allow said yarn fiber to be easily collected and twisted into a predetermined pattern, wherein said yarn fiber is heated at a working temperature between approximately 60° C. and approximately 300° C.; and (d) enwrapping said improved yarn fiber on a spun yarn tube.