Durkoppwerke Gmbh

Kurt Reinke

Eberhard Kastrup

Kurt Biermann

Heinz-Rolf Oberschelp

The disclosure concerns a drive device for a double thread chain-stitch buttonhole sewing machine. The machine has a first drive shaft for driving the sewing needle and for moving the cloth support plate for sewing. It has a separate worm shaft for moving the cloth support plate to the sewing position and also for operating a knife for cutting the buttonhole. A first respective electromagnetic clutch operates the sewing needle drive shaft, and a second respective electromagnetic clutch operates an intermediate shaft which then operates the worm shaft for operating the cloth support plate and knife operating shaft are provided. A drive shaft is connected with the armature part of the first electromagnetic clutch on the sewing needle driving shaft. That armature part is gear connected with an armature part of the second clutch on the intermediate shaft. Activation of the clutches controls which of the shafts operates, as the clutches include rotors which rotate with respect to their respective shafts or are clutched to cause rotation of the shafts.

Drive device for a two-threaded chain-stitch buttonhole sewing machine

A photoelectric device on the head of a sewing machine detects the trailing edge of a fabric workpiece and initiates a count of pulses representing increments of the steps of displacement of the workpiece in stitch formations. Each step is subdivided into a plurality of segments which are represented by respective multiplicities of increments so that from a count of increments after detection of the reference point to a particular angular orientation of the arm shaft, a stitch combination can be drawn from a memory which will include stitches of an original length and stitches of a length reduced from the original by a fixed amount so that in the number of stitches of the selected combination the row will be completed to a certain distance from the reference edge.

Stitch correction method and apparatus for a sewing machine

An attachment for a sewing machine comprises a looper bar positionable for horizontal oscillation underneath a vertically reciprocating needle, at a level determined by a workpiece feeler engaging the upper surface of a fabric being sewn, which is swingably carried on the stem of a presser foot resting on the workpiece while the latter is intermittently advanced by a bottom feeder periodically rising from a slot in a stitch plate and a reciprocable gripper foot synchronized therewith to act as a top feeder. A first sensor detects a rise in the presser foot, to an extent indicating the presence of resilient padding between an upper and a lower fabric layer, to activate the looper bar; a second sensor temporarily deactivates the first sensor whenever the bottom feeder projects above the stitch plate. The first sensor can also be used to change the stroke of the top feeder relatively to that of the bottom feeder whenever the workpiece thickness is found to surpass another threshold indicative of the need for providing one fabric layer with an excess of material compared with the other layer.

Sewing-machine system for continuously monitoring workpiece thickness

A device for feeding to a sewing machine a strip of fabric, in particular a longitudinally folded band to serve as a pocket welt, comprises a generally oval-shaped guide mountable on the sewing-machine base and provided with sides shaped as U-profiles and with a tongue at an output end for folding a fabric strip upon passage thereof along a feed path to a sewing station at the machine. A beam of light from a gallium-arsenide source traverses the feed path in the region of the tongue to energize a photocell upon passage of a workpiece, the photocell being connected to a stitch counter for activating the same upon energization by the source. The guide has a length scale with graduations spaced in the direction of the feed path for implementing the manual positioning of a fabric strip prior to the feeding thereof to the sewing station, while the stitch counter is operationally coupled to the reciprocating sewing-needle drive to arrest the same upon counting a predetermined number of stitches. The positioning of a fabric strip via the scale and the automatic stopping of the sewing-machine drive by the photocell-activated counter ensure a precise positioning of a final stitch relative to a sewn welt.

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Bielefeld, Germany

Kurt Reinke