Abstract: A thread tensioning device comprising a stationary electromagnet mounted on a sewing machine arm and a tensioning wheel having a relatively low mass. The tensioning wheel is rotatable concentric to a longitudinal axis of the electromagnet and is mounted on the electromagnet so as to be moveable only slightly in the direction of the longitudinal axis. A friction disk is positioned at one end of the electromagnet so as to be between the electromagnet and the tensioning wheel. A current flows through an excitation winding in the electromagnet and its value is varied within given limits by a suitable current control device, thereby causing the electromagnet to pull a flat side of the tensioning wheel with corresponding force against an application side of the friction disk, whereby a corresponding variable thread tensioning force is applied to a sewing thread passing through the tensioning wheel to the sewing machine.

Abstract: A thread-chain separating head, in particular for a double chainstitch sewing machine, comprising a heating wire for thermically separating the thread chain and comprising a suction tube for leading the thread chain towards the heating wire. Said heating wire is arranged laterally and outside of the suction tube in order to achieve advantageous conditions during the heating and separating operation.

Abstract: A device for controlling the looper thread of a double chainstitch sewing machine has a looper which can be oscillatingly driven in the sewing direction. A link mechanism is provided to drive the spreader, said link mechanism being designed as a six-bar linkage mechanism with a four-bar linkage and a secondary two-link group. The basic linkage and the two-link group are arranged in such a manner that two links are guided during a movement of the spreader in an extreme position in which it does not spread the looper thread. Thus a spreader movement is produced which is particularly adapted to the sewing process.

Abstract: A throat plate of an automatic sewing arrangement producing a double lockstitch and having a feeding device for generating a feed motion in any direction in a sewing plane as a relative movement between the needle and a workpiece. The throat plate is formed at the surface turned towards the workpiece with a closed needle aperture area, and is formed at the surface turned away from the workpiece with an opened needle aperture area profiled with a thread guiding edge affecting the hook thread leaving the double lockstitch hook. The thread guiding edge controls the position of the hook thread with respect to the needle so as to avoid a double interlocked stitch formation.