Yarn-feeding/recovering method for textile machines, and apparatus for carrying out such method

Abstract

A textile machine receives yarn from a yarn-feeding device via a yarn-recovering device provided with a motorized reel having a passage for the yarn, which extends between an inlet port open to the middle of the free end of the reel and an outlet port formed on the lateral surface of the reel; the tension of the yarn being maintained constant on a reference value by adjusting elements, on the basis of a measured tension signal generated by a sensor; a consumption indicator being obtained to detect an interruption in the delivery of yarn, the adjusting elements being temporarily disabled and the yarn-recovering device being temporarily enabled to rotate at a speed modulated on the basis of the measured tension signal for maintaining the tension of the yarn constant on the reference value, if an interruption in the delivery of yarn is detected.

What is claimed is: 
     
         1 . A yarn-feeding/recovering method for textile machines, in which a textile machine receives yarn from a yarn-feeding device via a yarn-recovering device provided with a motorized reel having a passage defined therein which is passed through by the yarn and extends between an inlet port open to the middle of the free end of the reel and an outlet port formed on the lateral surface of the reel, said yarn-recovering device being operable for temporarily recovering an amount of yarn already delivered to the machine and for giving it back at a later time, and in which the tension of the yarn, with said reel in a position of minimum interference with the yarn, is maintained substantially constant on a reference value by adjusting means on the basis of a measured tension signal generated by sensor means, wherein it comprises the steps of obtaining a consumption indicator, which is indicative of the delivery of yarn from said yarn-feeding device and is independent from any operative signals from said textile machine and, if said consumption indicator indicates an interruption in the delivery of yarn, temporarily disabling said adjusting means and temporarily enabling said yarn-recovering device to rotate at a speed modulated on the basis of said measured tension signal for maintaining the tension of the yarn substantially constant on said reference value. 
     
     
         2 . The method of  claim 1 , wherein it comprises the steps of monitoring the position of said reel with respect to said position of minimum interference with the yarn and, if said reel comes back to the position of minimum interference while said yarn-recovering device is enabled, disabling said yarn-recovering device and re-enabling said adjusting means. 
     
     
         3 . The method of  claim 1 , wherein it comprises the steps of monitoring the position of said reel with respect to said position of minimum interference with the yarn, and stopping said reel at the achievement of a predetermined maximum number of recovery revolutions. 
     
     
         4 . The method of  claim 1 , in which said yarn-feeding device is provided with a stationary yarn-winding drum, from which the yarn is unwound upon request from the textile machine, and said adjusting means consist of an electronic yarn-braking device arranged downstream of said yarn-feeding device and controlled by a control unit, and in which the withdrawal of yarn from said stationary drum is monitored by sensor means, wherein said consumption indicator consists of a consumption signal based on the signals generated by said sensor means. 
     
     
         5 . The method of  claim 4 , wherein it comprises the steps of monitoring the position of said reel with respect to said position of minimum interference with the yarn and, if said consumption signal indicates that yarn is withdrawn while said yarn-recovering device is enabled, automatically moving said reel to its position of minimum interference, disabling said yarn-recovering device, and re-enabling said adjusting means. 
     
     
         6 . The method of  claim 1 , in which said yarn-feeding device is provided with a motorized yarn-winding drum having yarn wound theron which is to be fed to said downstream machine, and said adjusting means comprise a control unit which is programmed to adjust the speed of rotation of said yarn-winding drum, wherein said consumption indicator is the speed of rotation of said yarn-winding drum, and that the zeroing of said speed of rotation is construed as indicative of the interruption in the delivery of yarn to said textile machine 
     
     
         7 . An apparatus for feeding/recovering yarn to/from a textile machine, comprising a yarn-feeding device arranged to feed yarn to said textile machine, a yarn-recovering device arranged between said yarn-feeding device and said textile machine and provided with a motorized reel having a passage defined therein which is passed through by the yarn and extends between an inlet port open to the middle of the free end of the reel and an outlet port formed on the lateral surface of the reel, adjusting means controlled by a control unit for maintaining the tension of the yarn substantially constant on a reference value on the basis of a measured tension signal generated by sensor means, with said reel in a position of minimum interference with the yarn, said yarn-recovering device being operable for temporarily recover an amount of yarn already delivered to the machine and for giving it back at a later time, wherein said control unit is programmed for processing a consumption indicator, which is indicative of the delivery of yarn from said yarn-feeding device and is independent from any operative signals from said textile machine, and, if said consumption indicator indicates an interruption in the delivery of yarn, temporarily disabling said adjusting means and temporarily enabling said yarn-recovering device to rotate at a speed modulated on the basis of said measured tension signal for maintaining the tension of the yarn substantially constant on said reference value. 
     
     
         8 . The apparatus of  claim 7 , in which said yarn-feeding device comprises a housing supporting a motorized yarn-winding drum as well as said sensor means, wherein said reel is also supported by said housing between said yarn-winding drum and said sensor means and is arranged with its axis parallel to the axis of the yarn-winding drum. 
     
     
         9 . The apparatus of  claim 8 , wherein said inlet port has an axis which is oblique with respect to the axis of the reel. 
     
     
         10 . The apparatus of  claim 8 , wherein said inlet port and said outlet port have respective inner beveled surfaces.