Abstract: In a process and a device for shortening the needle thread end at the beginning of sewing and at the end of sewing in two-thread lockstitch sewing machines, the catch thread device (23) of an already existing thread-cutting device (22; 60; 90) is moved into its thread-catching position during the first stitch formation cycle, and it is ensured, either by the selection of a suitable point in time for moving the catch thread device (23) or by a compressed air flow discharged from a compressed air line (81), that at least the reserve-side leg of the needle thread loop will be caught by the catch thread device (23). Part of the needle thread end is cut off during the return movement of the catch thread device (23) into its starting position. Furthermore, the needle thread is clamped either under a leaf spring (44), or is pushed by a sufficiently large feed step under the pressure foot, and is thus held in a frictionally engaged manner.

Abstract: Patterns of two fabric layers are each recognized by a camera and the fabric layers are aligned to make these patterns agree in the transverse and longitudinal directions. According to the invention the influence of speed-related disturbance variables and pattern-related limitations during the generation of the signal is reduced. Two-dimensional images of the two fabric layers are recorded with a matrix camera each during a pause between feeds. The degree of congurence of the fabric layers according to the pattern is determined by two-dimensional cross-correlation analysis of the image points arranged in rows and columns. Aligning correction values are calculated from this degree. The edge distance of the fabric layers is determined with a section of the matrix sensors, which is a separate section in terms of evaluation. Based on the edge distance data, the lower fabric layer is adjusted to the correct distance continuously and the upper fabric layer is adjusted as needed.

Abstract: Method and apparatus for determining and regulating the amount of advance of a plurality of workpiece plies at a sewing machine which is affected by scanning the individual plies while recording the stitches being formed between two separate feed points and actuating top and bottom feed devices to achieve a desirable feed of each ply. Signs present or to be applied at any desired point of the workpiece plies are scanned at two successive points, and pulses generated by a pulse generator connected with the main shaft of the machine are summed during this period of time. The pulse sum is compared with a number of pulses which depends on the mutual spacing of the scanning points and on the adjusted stitch length. For two work plies the pulse sums formed between the recognition of the signs are compared directly. As signs to be scanned are used either imprinted marks, the jags of a pinked workpiece edge, or the bright, dark structure of a surface section of the workpiece.

Abstract: A sewing machine for automatically making edge-parallel seams comprises a scanning device for recognizing the geometric form of the workpiece edge and a pressure piston lowerable laterally of the stitch formation point. For straight workpiece edges extending at an angle to each other, the pressure piston, having been lowered onto the workpiece with the sewing machine stopped, is rotated around the needle which is inserted in the workpiece, the workpiece being taken along accordingly. For a convexly arcuate edge pattern, first the lateral distance of the pressure piston from the needle is readjusted in such a way that it corresponds to the radius of the edge arc (e.g. scallop). Thereafter, with the sewing machine continuing to run, the pressure piston is lowered, whereupon the feed dog of the sewing machine rotates the workpiece around the pressure piston.

Abstract: A sewing machine with guide mechanism for automatically producing a curved edge parallel seam comprises a scanning unit for scanning the edge of a workpiece and sensing when the edge of the workpiece moves away from an edge guide which indicates the presence of a curved edge, a workpiece feeder for feeding the workpiece along the guide edge, a workpiece pressure stamp for applying pressure on the workpiece at a point spaced from the guide to cause rotation of the workpiece about the point when the pressure stamp is activated and a circuit connected between the scanning unit and the pressure stamp for intermittently activating the pressure stamp when the scanner senses the presence of a curved edge area of the workpiece.

Abstract: A device for the automatic guiding of a workpiece on a sewing machine to produce a curved edge parallel seam operates in conjunction with a sewing machine having a reciprocating needle and a presser foot engageable with the workpiece and a feed member engageable with the workpiece to move it relative to the needle. The sewing machine also includes a guide roll disposed in spaced relationship to the needle for guiding the edge of the workpiece and a scanner for scanning the workpiece edge for sensing its position. In accordance with the position sensed, a plunger is mounted above the workpiece and is movable into the engagement with the workpiece to hold the workpiece at a selected point so as to turn the workpiece during the feeding movement of the workpiece by this feed member.

Abstract: The device is for use in a sewing unit including a sewing machine and includes a vertically oriented relatively elongated intermediate plate separating two plies of material in advance of the sewing machine. Guide elements adjacent the intermediate plate support a clasping station for movement longitudinally of the intermediate plate. The clasping station includes a support mounting two clasps each selectively engageable with a respective ply of material. Photoelectric sensing devices are movable with the clasping station, and include respective sensing devices operatively associated with each ply of material and each operable to control engagement of a respective clasp with the associated ply of material responsive to sensing of the trailing edge of the associated ply of material. A counterweight arrangement exerts an adjustable pull on the clasping station in a direction opposite to the feed direction of the plies of material.