Buttonhole sewing machine thread brake - has a control rod linking both brakes with stop and zigzag mechanisms

摘要

The thread braking mechanism for a sewing machine working stitches is gps., such as sewing button holes, has a control rod in the kinematic linkage connecting two thread brakes, the stop mechanism and the zig-zag setting unit. The control rod slides axially with the stop mechanism and is attached by a rotary connection to the centre line of the zig-zag setting unit. There are two control paths, with one acting with the first thread brake by a stepped surface with equicentred curved sections towards the control rod. The other path acts with the second thread brake with stepped surfaces arranged together smoothly in a longitudinal plane. Each axial setting of the control rod is aligned with a surface section of the control paths. The system controls the movement of the upper thread so that the sewing machine is automatically prepared for the next sewing cycle, after a stitching sequence, without the operator having to making any changes.