Durkoppwerke Gmbh

Siegmund Balke

Gunter Lutkemeyer

A sewing machine adapted for moving a workpiece in a downstream direction for sewing a seam therein, and for automatically terminating the seam at a predetermined point a selected distance from a trailing edge of the workpiece. An edge sensor on a base is located a predetermined distance upstream of the sewing point for sensing the downstream passage of the trailing edge, and generating edge sensing signals in response thereto. A stroke sensor on the base senses the length of the strokes of the feed dog and generates stroke length signals which are indicative of the stroke length and of the length of the stitches. A stopping device is provided on the base for being actuated to engage the workpiece to stop its movement when the sewing needle is at the predetermined point for terminating the seam; and a control system receives the edge sensing signals and the stroke length signals, determines therefrom a time when the sewing needle will be at the predetermined point, and generates a stopping signal for actuating the stopping device at that time.

Sewing machine having means for terminating seams at a predetermined

A workpiece fed to a stitching point of a sewing machine, consisting of one or more layers of fabric, is transluminated by a source of visible or infrared radiation which is intercepted by two photoelectric sensors following each other in the direction of motion. The sensors work into respective radiation/frequency converters whose output voltages, after rectification, are compared in a window discriminator to provide an indication of the passage of a leading or trailing edge of a fabric layer manifesting itself in a jump in one of the voltages. The jump is intensified by a threshold circuit in each converter, comprising a Zener diode which for highly light-transmissive fabric layers can be short-circuited by an optocoupler.

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Spenge, Germany

Siegmund Balke