METHOD OF MAKING SELF-TIGHTENING STRAPS FROM ANNULAR CORD Russian patent published in 1998 - IPC

FIELD: plastic metal working. SUBSTANCE: method comprises steps of holding part of annular contour of cord and twisting its another part with tension onto rotary cone mandrel moving relative to said cord and having inlet portion. After said inlet portion of mandrel twists around cord, it is removed out engagement with cord. Formed loops are increased up to necessary size and loop turns are drawn one to another as closely as possible. Increase of loop size and drawing together their turns are realized by moving them along helical groove of rotary cone (said groove has regressive pitch) or by drawing them up onto smooth surface of mandrel. Tool for making self-tightening straps includes stem, inlet portion and cone mandrel. Said inlet portion is in the form of helix joined with mandrel. Said cone mandrel has helical groove. Helix of inlet portion and said helical groove have regressive pitch. Mandrel includes transition and sizing portions with different cone angles or different pitch of helical groove. Annular cord is twisted onto tool for forming double-turn closed helix and for sizing inner diameter of strap. EFFECT: enhanced efficiency. 6 cl, 24 dwg , 1 tbl