Process and apparatus for texturing textile yarns of thermoplastic

Abstract

Apparatus and a process for texturing textile yarn of thermoplastic material are described wherein the yarn is fed through input guide means including a yarn tension sensing unit to the surface of a continuously rotating cylinder having equidistantly spaced annular grooves distributed along its length with an annular friction surface between each pair of adjacent grooves. A series of rod-shaped thread guides, one for each groove, project from a support element into the grooves at points located on a notional helical curve extending along the cylinder. Thus, the yarn is constrained to travel along a helical path in contact with at least a portion of the series of thread guides while in contact with rotating annular surfaces. The yarn leaves the cylinder by way of output guide means including a yarn tension sensing unit. The angle between the direction of movement of the surface of the rotating cylinder and the direction of movement of the yarn along the helical path is a constant, the angle being larger than the twist angle imparted to the yarn. The input and output tension sensing units may mechanically provide an indication of the ratio of these tensions enabling the ratio to be adjusted if it departs from a predetermined value, usually unity. Alternatively, these units may be electrical and control a servo motor that provides the required adjustment by moving an input thread guide for the yarn. This thread guide may be mounted on a member mounted on a plate to rotate about the cylinder and series of rod-shaped thread guides that extend through a hole in a plate. The servo motor moves the plate along the axis of the cylinder while a cam interaction between the rotatable member and the support for the series of thread guides causes the input thread guide to move parallel to the helical curve. When starting, the plate can first be moved to or close to the output end of the cylinder to reduce yarn tension.