Electrical Positive Yarn Feeding Device

Abstract

A yarn delivery device is provided with a motor-driven yarn delivery wheel, wherein the rotated position of the yarn delivery wheels is detected with high precision by means of an angle encoder. The angle encoder has at least a resolution s which is greater than the circumference of the yarn delivery wheel, measured in millimeters. The resolution s is preferably greater than five times (preferably 5.24 times) the value of the diameter of a winding of the yarn delivery wheel. The yarn delivery wheel is preferably looped by several (three to twenty) windings.

1 . A yarn delivery device ( 1 ), in particular for knitting machines, 
 having a yarn delivery wheel ( 5 ), around which the yarn ( 9 ) to be delivered loops in at least one winding ( 12 ) for conveying the yarn ( 9 ),    having an electric motor ( 14 ) which has a shaft ( 13 ) which is connected, fixed against relative rotation, with the yarn delivery wheel ( 5 ),    having an angle encoder ( 17 ) for detecting the rotated position of the yarn delivery wheel ( 5 ), wherein the angle encoder ( 5 ) has an angular resolution (s) which is at least so large that the ratio (s/d) between the angular resolution (s) and the diameter (d) of the yarn delivery wheel ( 5 ) is greater than 3 mm −1 .    
   
   
       2 . The yarn delivery device in accordance with  claim 1 , characterized in that the angle encoder ( 17 ) is connected with the shaft ( 13 ).  
   
   
       3 . The yarn delivery device in accordance with  claim 1 , characterized in that the shaft ( 13 ) is a shaft extending through the electric motor ( 14 ), at one of whose ends the yarn delivery wheel ( 5 ) is fastened, and on the other end ( 16 ) the angle encoder ( 17 ).  
   
   
       4 . The yarn delivery device in accordance with  claim 1 , characterized in that the angle encoder ( 17 ) is an incremental encoder.  
   
   
       5 . The yarn delivery device in accordance with  claim 1 , characterized in that the angle encoder ( 17 ) is an encoder.  
   
   
       6 . The yarn delivery device in accordance with  claim 1 , characterized in that the angle encoder ( 17 ) is an optical step sensor.  
   
   
       7 . The yarn delivery device in accordance with  claim 1 , characterized in that the angle encoder ( 17 ) has an angular resolution (s), which is at least so great that the ratio (s/d) between the angular resolution (s) and the diameter (d) of the yarn delivery wheel is greater than 5 mm −1 .  
   
   
       8 . The yarn delivery device in accordance with  claim 1 , characterized in that the angle encoder ( 17 ) is connected to an actual value input of a control loop ( 29 ).  
   
   
       9 . The yarn delivery device in accordance with  claim 8 , characterized in that the control loop ( 29 ) has a desired value input which is designed for receiving external desired position signals.  
   
   
       10 . The yarn delivery device in accordance with  claim 8 , characterized in that the control loop ( 29 ) is a PD regulator.  
   
   
       11 . The yarn delivery device in accordance with  claim 8 , characterized in that the control loop ( 29 ) is connected a tension regulator ( 38 ) with a device for disturbance variable compensation.  
   
   
       12 . The yarn delivery device in accordance with  claim 8 , characterized in that control loop ( 29 ) is connected with a yarn tension sensor ( 37 ) for detecting the yarn tension.  
   
   
       13 . The yarn delivery device in accordance with  claim 12 , characterized in that a comparator circuit ( 32 ) is connected to the yarn tension sensor ( 37 ), which compares the detected yarn tension with a desired yarn tension and determines a desired position signal from the comparison.  
   
   
       14 . The yarn delivery device in accordance with claim  1 , characterized in that the electric motor ( 14 ) is connected to a regulating circuit ( 34 ) which is set up for a dragging mode of operation, in which the current supply to the electric motor ( 14 ) causes a torque insufficient for independent yarn conveyance.  
   
   
       15 . The yarn delivery device in accordance with  claim 14 , characterized in that a control circuit ( 34 ) is provided, which registers the revolutions of the electric motor ( 14 ) in the dragging mode of operation by means of the angle encoder ( 17 ).  
   
   
       16 . The yarn delivery device in accordance with  claim 15 , characterized in that an allowance for the positive delivery mode of operation is obtained from the registered revolutions.  
   
   
       18 . The yarn delivery device in accordance with  claim 16 , characterized in that the allowance is obtained from the registered revolutions of several yarn delivery devices ( 1 ,  2 ,  3 ).