Sewing machine, with separate fabric advance drives for the upper and lower fabrics, has a thread tensioner set by a control according to the level of fabric curling to maintain a constant tension

摘要

The sewing machine, with transport systems to move the upper and lower fabrics, has a mechanism to vary the movement speeds of the two fabrics to control any curling. A thread tensioner (1) is operated by an electrical drive (20) to vary the thread tension. A control sets the thread tensioner, according to the level of fabric curling. The thread tensioning system, at a sewing machine, has an adjustment unit to set the thread tension according to the level of fabric curling, operated by the control. A monitor registers the angular position of the sewing machine shaft which gives the reciprocating needle movements, for the control to set the thread tension according to the angular shaft position. An independent claim is included for a sewing machine thread tensioner, with a press disk and a drive (18), including a drive shaft (4) to push the press disk against the thread tensioning disks. The press disk is mounted to give oscillation at the drive shaft. Preferred Features: The setting control has one position for the press disk, when the thread tensioning disks (2) are open, so that there is no pressure on one of the tensioning disks (2A).