Device for feeding an elastically extendable yarn to hosiery knitting machines

摘要

A device for feeding an elastically extendable yarn to hosiery knitting machines comprising a positive yarn feeder (2) composed of two mutually opposite contrarotating rollers (3,4) which have parallel axes and between which the yarn (5) to be fed passes. Elements are provided for rotationally actuating at least one of the rollers (3,4) about its own axis with a rotation rate which can vary on command. The device comprises, downstream of the positive feeder (2) along the yarn feed direction, elements (7) for detecting the tension of the yarn (5) and a programmable control and monitoring unit (8) which is operatively connected to the detector elements (7). The control and monitoring unit (8) is suitable to compare the yarn tension detected by the detector means (7) with a yarn tension which is preset in the control and monitoring unit (8). The control and monitoring unit (8) is also operatively connected to the rotary actuation means in order to vary the rotation rate of the roller of the positive feeder (2) in order to maintain within a preset tolerance range the difference between the detected yarn tension and the preset yarn tension.