A stock-controlling method for a storage yarn feeder with rotary drum

摘要

A yarn feeder is provided with a drum (12) which is driven to rotate by a motor (14) controlled by a control unit (CU) for drawing yarn from a reel (R) and winding it upon itself in the shape of loops forming a stock. The control unit (CU) estimates the stock (RES) on the drum (12) on the basis of an information indicative of the amount of yarn which is unwound from the drum (12) upon request from a downstream machine (M), and of an information indicative of the amount of yarn which is wound on the drum (12), and retroactively controls the motor (14) to substantially stabilize the stock (RES) on a reference value (REF_RES). The control unit (CU) also performs a parallel correction routine in which it compares the stock (RE) with the reference value (REF_RES) to estimate a stock status RES < REF_RES or RES ‰¥REF_RES, wherein RES is the estimated stock and REF_RES is the reference value, and compares the estimated stock status with a presence signal generated by sensor means (16) adapted to generate an absolute binary information (RES_PRES) indicative of the presence/absence of yarn in a monitored area of the drum (12), and in case of inconsistency between the estimated stock status and the presence signal, corrects the stock (RES) so that it converges toward the monitored area of the drum (12).