Yarn control mechanisms and the like

A rotatable control system for yarn or like material comprising in combination:

• an element having an outer cylindrical peripheral surface extending substantially parallel to said element's axis of rotation, said surface being accessible to the yarn to make continuous contact therewith for the length of yarn along the surface, said surface having a number of discrete guide surfaces, at least in part, staggered about an imaginary reference plane which is perpendicular to said axis of rotation of said element, alternate ones of said number of said discrete guide surfaces providing a first set of such surfaces each of which bend only in a first direction relative to said reference plane, and the intervening ones of said guide surfaces providing a second set of said surfaces, each of which bends only in the opposite direction to said first direction, the divergence of adjacent surfaces relative to said reference plane increasing with increasing distance from said axis of rotation to define, for the material, a zig-zag path which degenerates with increasing distance from said axis of rotation of said element into a line path lying in said reference plane of said element;
• and
• control means for varying the distance of the yarn from said element axis of rotation to thereby vary the tension applied by said element as it is rotated including:
• a guide member pivoted on one end, and means for guiding said yarn after leaving said control element attached to the other end of said guide member so that the position of said guidance means and member vary as a function of the tension in said yarn to vary the distance between the yarn and said element axis.