Sewing machine lower thread end monitor - has light reflecting surface on looper housing side towards bobbin housing to prevent soiling

The thread monitor at a sewing machine, to detect the end of the lower thread, has at least one opening at the base of the lower section of the bobbin housing, which is larger than the drillings in the bobbin flanges, aligned with a recess in the upper section of the bobbin housing. The reflection surface is on the side of the looper housing towards the lower section of the bobbin housing. The recess in the upper section of the bobbin housing is formed by the enlarged recess for the penetrating needle against the direction of looper rotation. The core of the bobbin has two webs each with drillings which are coaxial to each other and to the drillings in the bobbin flanges. The upper section of the bobbin housing is coated with a light absorbent layer. ADVANTAGE - Soiling of the reflection surface is eliminated to improve the detection of the end of the lower thread