19
4. Thread trimming
4.1 Description of the trimming mechanism
During the trimming cycle, the moving trimming knife (1), in
an opportune moment, hooks up the sewing threads and pulls
them in the sense of the arrow (A) against the fixed knife (2)
until the threads are trimmed. The spring (3) holds the hook
thread after being trimmed off. The moving knife (1) is mounted
on the shaft (4) which turns by means of the lever (5) under
the effect of the fork (6) fixed on the shaft (7) which is shifted
by the electromagnet (8) from its starting position in the sense
of the arrow (B). When moving back in the sense of the arrow
(C), the shaft (7) is shifted by the cam (9) through the pickup
roller (10) into the starting position. The spring (11) maintains
the mechanism in its starting position. The electromagnet
(12), in an opportune moment, loosens the main thread
tensioner. At the end of the trimming cycle, both electromagnets
(8 and 12) are switched off.
4.2 Setting the pickup roller
The holder of the pickup roller (1) is to be fixed in such a way
that it is positioned, in its starting position, between the shaft
(2) and the shaft (3), the respective gap A = 0.2 to O.4 mm.
Caution! Danger of injury!
Switch off the main switch! Before starting the
setting operation, wait until the motor stops!
- With the loosened screw (4), put the holder of the pickup
roller (1) up to the stop against the bracket (5) and, at the
same time, the shaft (2) up to the stop against the shaft
(3).
- With the holder (1) held on the stop, shift the shaft (2) in
such a way that there appears the gap A = 0.2 to 0.4 mm,
and tighten the screw (4).
- Check the gap A in shifting the armature (6).
4.3 Setting the cam
The position of the cam (1) against the shaft (2) is to be such,
so that when the adjusting pin is in contact with the shaft (4),
the protractor scale of the handwheel (6) shows just the angle
of 108
°
. If the pickup roller (5) is in its starting position of
rest, the clerarance between the roller (5) and the cam (1)
should be as small as possible but sufficient to prevent the
cam from getting into accidental contact with the roller.
Caution! Danger of injury!
Switch off the main switch! Before starting the
setting operation, wait until the motor stops!
- Set the angle of 108
°
on the handwheel (6) and lock it with
the screw (7) which is included in the accessory of the
machine (tighten with care).
- Shift the pickup roller (5) in the sense of the arrow up to the
stop.
- Insert the adjusting pin (3), which is included in the
accessory, into the cam and turn the cam, until the pin (3)
gets the contact with the shaft (4).
- Insert a gauge having the thickness of 0.1 mm between the
cam (1) and the pickup roller (2) and shift the cam against
the gauge up to the stop. Tighten then the screw (8).
- Loosen the blocking of the handwheel, turn a bit the cam
and tighten the second fastening screw of the cam too.
2
A
1
3
6
4
5
8
11
5
7
B
1
9
A
C
4
2
10
3
6
12
6
7
108
o
2
4
5
1
3
8
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