A motorized rotary drum supported on a motor housing bears a plurality of yarn loops wound thereon, such loops being adapted to be unwound upon request from a downstream machine. A yarn-unwinding sensor comprises light-emitting elements and light-receiving elements both of which are integral with the motor housing. Light-guiding elements which are integral with the drum guide the light from the light-emitting elements to a window which is defined on the rotary drum in a position such that it is repeatedly engaged by the yarn during its rotary unwinding motion, and vice versa. A reflecting surface reflects the light coming out of the window back towards the window. Light-deviating elements which are integral with the motor housing deviate the light coming back from the window towards the light-receiving elements. The unwinding of a yarn loop from the drum is determined on the basis of the variation of light resulting from the yarn transiting on the window.

Accumulation-type thread feeder including: a body, which bears a rotary drum on which turns of thread from a spool are wound; a tension sensor for detecting value of tension of exiting thread and a detector for detecting thread quantity accumulated on the drum; a light-reflecting element on the drum or functionally associated therewith, such light generated by light a generator borne by a support arranged alongside the drum, the support associated with a detector to detect light reflected by the reflecting element, the reflected light varying as a function of the quantity of thread wound on the rotary drum, the detection allowing detection of such thread quantity. The detector is a light-sensitive member directly receiving the light reflected by the reflecting element along the entire surface of the drum, the member allowing determination of thread density on the drum.

Accumulation-type thread feeder including: a body, which bears a rotary drum on which turns of thread from a spool are wound; a tension sensor for detecting value of tension of exiting thread and a detector for detecting thread quantity accumulated on the drum; a light-reflecting element on the drum or functionally associated therewith, such light generated by light a generator borne by a support arranged alongside the drum, the support associated with a detector to detect light reflected by the reflecting element, the reflected light varying as a function of the quantity of thread wound on the rotary drum, the detection allowing detection of such thread quantity. The detector is a light-sensitive member directly receiving the light reflected by the reflecting element along the entire surface of the drum, the member allowing determination of thread density on the drum.

A yarn feeder is provided with a drum which is driven to rotate by a motor controlled by a control unit for drawing yarn from a reel and winding it upon itself in the shape of loops forming a stock. The control unit estimates the stock on the drum on the basis of an information indicative of the amount of yarn which is unwound from the drum upon request from a downstream machine, and of an information indicative of the amount of yarn which is wound on the drum, and retroactively controls the motor to substantially stabilize the stock on a reference value. The control unit also performs a parallel correction routine in which compares the stock with the reference value to estimate a stock status RES<REF_RES or RESREF_RES, wherein RES is the estimated stock and REF_RES is the reference value.

A method for supplying a thread to a textile machine without creating torsions thereof includes picking up the thread from a reel, winding it on a rotary drum driven by an electric motor thereof and supplying such thread to the textile machine, preferably at constant tension and/or quantity. The method provides for measuring the amount of thread leaving the rotary drum and the amount of thread wound thereon and intervening on the rotation of such drum so the amount of thread leaving the drum is equivalent to the amount loaded thereon to avoid the creation of torsion on the thread. A device for implementing such method is also disclosed.