25
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 tensioner (13). 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.
B
C
11
10
8
6
5
12
13
9
7
2
A
1
3
6
4
5
5
1
3
8
2
4
6
7
108
o
13
2
3
1
4
A
