Continuous casting of stringers for sliding clasp fasteners

Claim 1

In an improved method of continuous casting a row of thermoplastic slide fastener interlocking elements upon a longitudinal edge of a stringer tape of indefinite length by an extrusion nozzle having an orifice and supplying thermoplastic material in advance of a nip between a pair of rotatable casting rollers, each having peripheral cavities for the casting of said interlocking elements, said improved method comprising the steps of: driving said pair of casting rollers at a relatively high speed while at the same time insuring adequate solidification of said interlocking elements before removal therefrom by drawing said stringer tape between said nozzle and a first one of said rollers and to a first side of said nip during extrusion of said thermoplastic material, from said orifice initially into the cavities of said first roller in advance of said nip for initially solidifying the portions of said interlocking elements on the upper surface of said stringer tape and subsequently into the cavities of the second one of said rollers, and delaying the removal of said stringer tape by recovering said stringer from the other side of said nip at such an angle with respect to said second roller of from about 30° to about 45°, such that said interlocking elements cast on said stringer tape are separated from the cavities of said first roller before they are separated from the cavities of said second roller and said interlocking elements further remaining in the cavities and in contact with said second roller for the 30°-45° angular segment portion of its rotation, thereby providing sufficient time for hardening of the portions of the interlocking elements on the lower surface of said stringer tape.