Yarn tensioning and control unit for embroidery machines

The yarn runs over the delivery roll and subsequently goes through a yarn tensioner with an operating element. The operating element follows a path, on which it either cuts the straight connecting line between a normal operation transmitter and a normal operation receiver, or the straight connecting line between an overtension transmitter and an overtension receiver. The straight connecting lines are arranged coaxially in relation to each other. The invention incorporates a synchronised disk, which is fastened on the main machine shaft and works together with a synchronised transmitter and a synchronised receiver. The disk determines the part of the working cycle for the signal for the operating of the stepping engine, which moves the delivery roll in the revolution direction via the torque amplifier. The delivery roll draws the yarn out of the working position until the operating element cuts the straight connecting line between the normal operation transmitter and the receiver.