Device for detecting and/or adjusting a tensile force in a yarn

Apparatus for at least one of monitoring and adjusting a tensile force in a yarn, comprising:

• spaced apart first and second yarn deflecting elements;
• a third yarn deflecting element located between the first and second yarn deflecting elements, said third yarn deflecting element having a coefficient of friction that results in a reaction force exerted on a yarn engaging and deflected by the third yarn deflecting element when the yarn is moved across the third yarn deflecting element;
• a swivel arm supporting the third yarn deflecting element, said swivel arm mounted for pivotal movement on a pivot shaft and wherein the third yarn deflecting element is located distally along said swivel arm relative to said pivot shaft, and is at least movable in positions out of alignment with the first and second yarn deflecting elements upon pivotal movement of the swivel arm on the pivot shaft;
• one of said first and second yarn deflecting elements located substantially at the location of said pivot shaft and such that the third yarn deflecting element supported by the swivel arm may engage and deflect a yarn extending from the respective first or second yarn deflecting element located substantially at the pivot shaft location when the swivel arm is pivoted so that the third yarn deflecting element is non-aligned with the first and second yarn deflecting elements, whereby the yarn is substantially aligned with and intersects the pivot shaft;
• an electric motor drive unit connected to the pivot shaft and arranged to respond to either or both torque applied by the swivel arm to the pivot shaft or movement of the swivel arm and the pivot shaft in response to a force exerted on the third yarn deflecting element by a tensioned yarn extending between the three deflecting elements when the third yarn deflecting element is supported by the swivel arm in a non-aligned position between the first and second yarn deflecting elements;
• wherein, due to the location of the pivot shaft relative to the respective first or second yarn deflecting element located substantially at the pivot shaft location, and the third yarn deflecting element, the response of the electric motor drive is not influenced by the friction between the tensioned yarn and the third yarn deflecting element upon motion of the yarn between the first, second and third yarn deflection elements, but only by the tension force in a tensioned yarn portion extending in a single direction upstream or downstream of the third yarn deflecting element with regard to yarn motion when the third yarn deflecting element is non-aligned with the first and second yarn deflecting elements.