A yarn feeding apparatus for a yarn processing textile machine, such as a circular knitting machine, having
- a holder (1, 1') adapted for attachment to the machine;
- yarn guide monitoring means (27, 28, 29;
- 30, 31, 310, 311) secured to the machine for guiding and monitoring feed of yarn (25, 25a);
- an electric motor (10) secured to said holder;
- and at least one yarn feed element (14, 14', 514) feeding yarn, in a slip-free manner, from the circumference thereof to a yarn utilization position,
- wherein said electric motor is a stepping motor (10);
- electric energy pulse supply means (60-66) are provided, for energizing the stepping motor to rotate at a predetermined speed;
- and supplying, continuously stepping motor supply pulse trains;
- said at least one yarn feed element (14, 14', 514) is coupled, in driving relation, to the stepping motor;
- the yarn guide and monitoring means (27-29;
- 30-33, 310, 311, 330, 330a) include a movable yarn run-off yarn guide-and-feeler (330, 330a) located with respect to the yarn guide element to sense the tension condition of yarn being supplied from the yarn feed element to the yarn utilization position of the textile machine, said run-off yarn guide-and-feeler being assigned to the respective at least one feed element (14, 14', 514) for guiding and monitoring yarn being fed and supplied thereby;
- and switch means (S, 70, 70a) are provided, controlled by the run-off yarn guide-and-feeler (330, 330a), controlling, during operation of the textile machine, in an ON-OFF manner, as a function of sensed yarn being required by the sensed yarn being required by the textile machine at the yarn utilization position, selectively, either
- (a) interrupting of transmission of rotary power from the stepping motor to the feed element upon termination of requirement of yarn by the textile machine at the yarn utilization position,
- (b) continue transmission of rotary power from the stepping motor to the associated feed element (14, 14', 514) as determined by said pulse supply means, upon requirement of yarn by the textile machine at the yarn utilization position.