Yarn-feeding apparatus and method for controlling it

In a yarn feeding apparatus for the selective positive feeding of several yarns to a knitting machine, including sensor means for generating sensor signals,, the sensor signals representing the respective feeding condition or non-feeding condition of the yarns, and an error detection unit connected to the sensor means for turning off the knitting machine in response to predetermined sensor signal combinations representing a yarn breakage and/or a yarn over-feed and/or a yarn change fault, the improvement comprising wherein the error detection unit includes a working position sensing unit for generating actual position data representing the working position of the knitting machine, a logic circuit for deriving a yarn changing signal from the sensor signals, the yarn changing signal indicating the changing of yarns, and a memory means storing yarn changing position data which are dependent on the working position of the knitting machine when the yarn changing signal indicates the changing of yarns, wherein the error detection unit determines whether the actual position data fall within a data range when the yarn changing signal indicates the changing of yarns, the data range being defined by the stored position data, and wherein the error detection unit disables the turning off of the knitting machine in response to the predetermined sensor signal combination if the actual position data fall within the data range.