Yarn Feeders

Yarn feeders can be divided into “positive” or “negative” types depending on the possibility of controlling the yarn feeding speed and uniformity.

A yarn feeder is the negative type when the needle takes the yarn directly from the package during the stitch formation step, and the feeding tension of the yarn cannot be controlled.

This feeding technique can generate differences in the yarn length used for stitch formation.

This is due to the variable tension of the yarn since a new spool has a certain diameter, which gradually reduces as more yarn is unwound and fed into the machine. In addition, the spool can be too hard or too soft.

Circular knitting machine manufacturers have eliminated this problem by implementing two distinct solutions:

1. The motorised yarn accumulator levels off the yarn tension when rotating, it accumulates a certain quantity of yarn on a constant-diameter pulley and then stops. The yarn wound on the accumulator is then conveyed to the thread guide always maintaining the same tension. The machine takes up the yarn, gradually emptying the accumulator, which is then restarted automatically to replenish its yarn reserve.

This solution is particularly indicated when the same type of feeding technique cannot to be applied to all the feed systems due to the structure of the knit stitches. Therefore, yarn accumulators are mainly used on machines for the manufacturing of fabrics of pre-set length, or also of continuous cloths with Jacquard patterns.

Positive feed systems control the tensions of the yarn fed by means of a drive wheel or a drive belt system.

The drive wheel systems, which in the past were much more widespread than today, consist of two conical toothed wheels. The thread passes between the two wheels and the quantity of yarn can be adjusted by approaching or withdrawing the wheels. This positive system grants a smooth feeding of the yarn on all the feed systems.

Today, the belt system has become the most common positive feeding system. The belt makes the spool rotate, and the number of rotating spools corresponds to the number of feed systems.

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