13. Thread trimmer (Class 767-FA-...)
13.1 Function sequence
When, during sewing, the pedal is stepped completely back in order to
trigger the trimming sequence, then the needle is positioned in the 1.
position. The drive stops briefly.
The magnet presses the roller lever 1 against the lowest point of the
guide curve 2. The thread knife 4 is swung completely away from the
counter knife 3 thereby.
The sewing machine runs with a cutting speed of 150
min-1
.
When the guide curve 2 swings the thread pulling knife 4 to the counter
knife 3, then the thread pulling knife is swung to just in front of the nose
of the bobbin case in the 1st movement phase. Through this, the thread
pulling knife is outside of the movement range of the bobbin case
opener finger.
At the beginning of the 2nd movement phase the thread pulling knife
first catches the hook and then the needle thread. The thread tension is
opened. In due course the thread pulling k nife pulls thread from the
spool. Just before the thread lever high position the threads are cut and
the underthread clamped.
When the thread lever high position and thus the 2nd position are
reached, the drive stops. The magnet for the thread tension opening
and the magnet for the thread trimmer are turned off.
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