Device and method for feeding an elastomeric yarn to a textile machine

Abstract

A method and device for controlling the feed of an elastomeric yarn ( 11 ), of known elastic characteristics, withdrawn from a bobbin (B) and fed to a textile machine ( 10 ) such as a knitting machine, a stocking machine, a bobbin winder or other textile machine, the yarn possessing an intrinsic elasticity and being fed to the machine with an intrinsic speed, there being provided elements ( 18 ) for sensing the tension of the yarn ( 11 ) and elements ( 3, 12 ) for measuring and modifying this speed, both associated with a single body ( 2 ) of the device ( 1 ) and both connected to elements ( 20 ) for controlling and regulating the tension and speed parameters; elements for compensating the variation in the elongation of the yarn being provided to maintain the diameter and the quantity of the yarn fed to the textile machine constant.

1 . A device for controlling the feed of an elastomeric yarn ( 11 ), of known elastic characteristics, withdrawn from a bobbin (B) and fed to a textile machine ( 10 ) such as a knitting machine, a stocking machine, a bobbin winder or other textile machine, said yarn possessing an intrinsic elasticity and being fed to said machine with an intrinsic speed, there being provided means ( 18 ) for sensing the tension of the yarn ( 11 ) and means ( 3 ,  12 ) for measuring and modifying this speed, said sensing means ( 18 ) and said measuring and modifying means ( 3 , 12 ) being both connected to means ( 20 ) for controlling and regulating said tension and speed parameters, said control and regulating means ( 20 ) continuously measuring the values of both said parameters during the feed of the yarn ( 11 ) to the textile machine, characterised by comprising compensator means ( 30 ) arranged to compensate the variations in the dimensional characteristics of the elastomeric yarn ( 11 ) withdrawn from the bobbin (B) before the yarn ( 11 ) cooperates with the tension sensing means ( 18 ) and with the speed measurement means ( 3 ,  12 ) to enable a yarn with constant dimensional characteristics to be fed to said textile machine ( 10 ) for the entire duration of an article production.  
   
   
       2 . A device as claimed in  claim 1 , characterised in that the compensator means ( 30 ) comprise a member ( 31 ) in contact with the yarn and arranged to modify, if necessary, its speed of movement during its path from the bobbin ( 1 ) to the tension sensing means ( 18 ) and speed measurement means ( 3 ,  12 ), said member being connected to actuator means ( 33 ) which enable the member ( 31 ) to act on the yarn when necessary.  
   
   
       3 . A device as claimed in  claim 2 , characterised in that the member ( 31 ) is a wheel means such as a pulley or the like.  
   
   
       4 . A device as claimed in  claim 2 , characterised in that the member ( 31 ) is a yarn braking member.  
   
   
       5 . A device as claimed in  claim 2 , characterised in that the actuator means ( 33 ) are an electric motor, an air-operated motor or the like.  
   
   
       6 . A device as claimed in  claim 5 , characterised in that the member ( 31 ) is connected to the output shaft of the electric motor defining the actuator means ( 33 ).  
   
   
       7 . A device as claimed in  claim 2 , characterised in that the actuator means ( 33 ) are commanded and controlled by a control unit ( 34 ) cooperating with the control means ( 20 ) for the tension sensing means ( 18 ) and for the speed measurement and modifying means ( 3 ,  12 ), said control means ( 20 ) exchanging information with said unit ( 34 ) relative to the speed with which the yarn ( 11 ) is fed to the textile machine ( 10 ), to enable said control unit ( 34 ) to cause the actuator means ( 33 ) to act on the member ( 31 ) in contact with the yarn ( 11 ) in order to modify the yarn speed and, vice versa, to enable said control means ( 20 ) to regulate the speed of the yarn ( 11 ) fed to the textile machine ( 10 ) on the basis of the yarn speed modification effected by the said member ( 31 ), said control unit ( 34 ), the actuator means ( 33 ), the member ( 31 ) controlled by said actuator means ( 33 ), the control means ( 20 ), the tension sensing means ( 18 ) and the speed measurement and modifying means forming a control loop for the constant tension and constant speed feed of the elastomeric yarn of the textile machine.  
   
   
       8 . A device as claimed in  claim 7 , characterised in that the control means ( 20 ) cooperate with means ( 27 ) for controlling the operation of the textile machine.  
   
   
       9 . A device as claimed in  claim 1 , characterised in that the sensing means ( 18 ) and the measurement and modifying means ( 3 ,  12 ) are both associated with a single support defining the body ( 2 ) of the device ( 1 ).  
   
   
       10 . A method for feeding an elastomeric yarn to a textile machine such as to obtain an article of constant quality in each of its parts, said method comprising measuring the tension and speed or quantity of the yarn ( 11 ) fed to the textile machine and unwinding from a bobbin (B), said method being characterised in that the yarn ( 11 ), after being unwound from the bobbin (B), is acted upon in such a manner as to modify its flow speed to the textile machine, said action being effected at a point on the path of the yarn upstream of the measurement of its speed and tension, while continuously measuring the speed of the yarn downstream of said point on the path, and acting on the yarn on the basis of said measured speed so as to maintain a dimensional, i.e. diameter and elongation, stability of the yarn ( 11 ) fed to the textile machine.  
   
   
       11 . A method as claimed in  claim 9 , characterised in that the action on the yarn ( 11 ) is a braking action.  12 . A method as claimed in  claim 9 , characterised in that the action on the yarn ( 11 ) is an acceleration action.