Method of winding self-supporting bobbin and self-supporting bobbin with cheese package of lower thread for sewing machines

摘要

The thread is wound from an inside diameter (di1) of the bobbin package at a higher initial gear ratio between the speed of the bobbin being wound and a winding device split drum or a cam until a preset diameter for a gear ratio jump is achieved. After the preset diameter (di2, di3, di4) of the package for a jump change is achieved, the gear ratio is decreased in jumping manner, wherein all over the interval of the package diameter increase up to the next jump change of the gear ratio, the gear ratio continuously increases or decreases by controlled winding in order to maintain constant the axial distance between the adjacent coils equal to the thickness of the wound thread. A self-supporting bobbin with cheese package of lower thread for sewing machines is characterized in that between the inside diameter (di1) of the bobbin package and the outside diameter (di5) of the bobbin package is at least one jump change in the winding ratio. In the interval between the winding ratio changes, the thread coils (30) following each other are put side by side with zero gap, which is maintained in the interval between the jump changes of the winding ratio by continuous increase or continuous decrease of the winding ratio within a small range. The jump change of the winding ratio is caused by a jump change of the winding device gear ratio.