MACCHINA PER CUCIRE CON UN DISPOSITIVO PER COMANDARE UN PUNTO FINALE PRESTABILITO DI UNA CUCITURA

A sewing machine with at least one feed means, the feed amount of which is variable by means of a positioning device acting on at least one positioning gearing; with a system for approaching a predeterminable end point of a seam in spaced relation to the edge of a workpiece; with a sensor disposed before the needle which during passage of the edge triggers the process for the positioning of the needle in the end point; with a pulse generator coupled with the main shaft of the sewing machine for the delivery of counting pulses for a pulse counter and a microcomputer which interrupts the action of the feed means as a function of the pulses emanating from the sensor and from the pulse generator in the end point. For the exact control of the insertion of the needle into the predetermined end point, the microcomputer is connected with a displacement system for an abutment for the presettable limitation of the movement deflection of a follow-up element coupled with the positioning gearing and with a servo system moving the latter against the abutment. For feed reversal immediately after execution of the stitch formation in the end position, the follow-up element is coupled with the positioning gearing through a freewheel coupling. To prevent displacement of the abutment by reaction of the forces occurring when the stitch length is shortened, the displacement system is connected with the abutment through a self-locking gearing.