Thread drawoff tube for an open-end spinning unit

Claim 1

In an assembly of a spinning rotor and a thread drawoff tube of an open-end spinning unit, said spinning rotor being capable of rotating about an axis thereof and provided with a ring shaped fiber collecting surface formed at an inside ring shaped wall having maximum rotational diameter, said thread drawoff tube disposed coaxially in stationary condition at a position along an extended line of said axis of said spinning rotor and provided with a hollow yarn guide for delivering a continuous thread from said assembly and a flange portion extending from an inside terminal of said hollow tube toward said fiber collecting surface of said spinning rotor, the improvement comprising an improved thread drawoff tube provided with a thread passage, said thread passage having frictional resistance along a portion of said thread passage contacted by said thread having inner and outer ends for creating a rolling motion of said thread by frictional contact therewith when said thread is being delivered from said assembly, said thread passage provided with a continuous trumpet shaped friction surface in said portion of said thread passage, said portion of said thread passage having surface variations providing an effective coefficient of friction of said frictional resistance that gradually decreases toward the edge of said flange portion, said surface variations extending from said inner and outer ends of said portion of said thread passage and continuously contacting said thread.