Storage yarn feeder with rotary drum and yarn-unwinding sensor

摘要

A motorized, yarn-winding rotary drum (12) rotatably supported with respect to a motor-housing (16) is adapted to have a plurality of yarn loops (Y) wound on itself, which are adapted to be unwound upon request from a downstream machine. A yarn-unwinding sensor counts the yarn loops unwinding from the rotary drum (12) and comprises light-emitting means (42) and light-receiving means (44), both integral with the motor-housing (16), one of which has an annular configuration operatively facing an annular surface (30a) of the rotary drum (12) from which the yarn is unwound. Light-guiding means (66) integral with the rotary drum (12) guide the light from the light-emitting means (42) to the light-receiving means (44) through a light passage (30c) defined on the annular surface (30a). The unwinding of yarn from the rotary drum (12) is determined on the basis of the light dimming resulting from the yarn transiting on the light passage (30c).