Method and apparatus for controlling the thread joining process in an open end rotor spinning machine

Method for controlling a thread joining process having several thread joining steps and occuring by starting a rotor of an open end rotor spinning machine, which comprises performing a first thread joining step, adjusting the speed of the rotor in a narrow limited range for the beginning of a starting process of another thread joining step which occurs after the first thread joining step, selectively starting and finishing additional thread joining steps in substantially constant given intervals before and after the beginning of the starting process, determining at least one measured numerical variable based on rotor acceleration during rotor starting, starting the first thread joining step in dependence on the value of the measured numerical variable, selectively starting and finishing the additional thread joining steps at given intervals, counting the number of revolutions of the rotor during starting, and starting the first thread joining step after a given point in time is reached, the at least one measured numerical variable being a first measured numerical variable having a value and a second measured numerical variable having a value being smaller than the first measured numerical variable, expressing the number of revolutions of the rotor with the first measured numerical variable, and multiplying the given rotor speed for the beginning of the starting process of the thread unwinding by the square of the starting time and the sum of the given time intervals between the start of the first thread joining step and the beginning of the starting process of the thread unwinding and the starting time of the rotor forming a second measured numerical variable.

Apparatus for controlling a thread joining process having several thread joining steps and occuring by starting a rotor of an open end rotor spinning machine, comprising at least one spinning unit of the open end rotor spinning machine, a control device connected to said at least one spinning unit for controlling pre-feeding of a fiber quantity required for thread joining and for controlling fiber feeding to the rotor, for returning the joined thread end to the rotor and for at least temporarily controlling thread unwinding from the rotor for the duration of the joining process, a thread unwinding device and a sliver drawing-in device connected to the control device at least for the duration of the thread joining process, said control device including an adjustable timer connected to said thread unwinding and sliver drawing-in devices for timing the sequence and duration of individual thread joining steps of the thread joining process, means disposed in vicinity of the rotor for production of electrical rotor signals proportional to the speed of the rotor, means connected to said signal production means for evaluating at least one measured numerical variable from the rotor signals based on acceleration of the rotor, and an electrical start switch having an input connected to said evaluating means for responding to a selectable value of said measured numerical variable and an output connected to said timer for starting a first thread joining step.