Assembly for lower thread tension adjustment of sewing machine

摘要

An assembly for adjustment of lower thread tension for a sewing machine having a loop taker and a bobbin carrier which is held by the loop taker and carries a bobbin loaded with the lower thread. The assembly comprises a base plate and a resilient member, one end of which is connected to the base plate. A tension is given to the lower thread while the thread is passed between the base plate and the resilient member. A substantially L-shaped presser element having an upper vertical and a lower horizontal portion is provided for the assembly and is turnably attached to an inner wall of the bobbin carrier. The vertical portion of the presser element is adapted to press a free end of the resilient member against the base plate. A permanent magnet or electromagnet acts on the horizontal portion of the presser element without contact thereto. The magnet is manually operated from outside of the sewing machine to vary a magnetic force of the magnet against the horizontal portion of the presser element, upon which the presser element is turned to adjust the lower thread tension. The resilient member may be omitted and in this case the L-shaped presser element is designed to directly press the lower thread against the base plate.