8
3.4 Thread tensioners and limiter
3.4.1 Description
The main tensioners (1) serves for creating the tension of the
thread hen tightening the stitch. The auxiliary tensioner (2)
reduces the risk of pulling out of the thread after the thread
trimming hen removing the se n material, hen the thread
is passed through this material and hen the main tensioner
is relieved. The main tensioner is relieved by the mechanism
controlled by the shaft of the presser bar lifting (3) holding
the lever (4) ith a pulley. The motion is then transmitted by
the lever (5) and the tie rod (6) on the thread tensioner plate
(7) hose displacement (motion) relieves thethread tensioner
springs (8). In machines provided ith a thread trimming
device, the main tensioners (1) are relieved as ell upon the
s itching on of the electromagnet (10) hose electromagnetic
field ill attract the thread tensioner plate (7). The mechanism
of the adapting spring (12) maintains the upper thread in its
tensioned state hen passing through the hook and hen
entering the needle into the se n material. The thread limiter
(13) limits the length of the thread fed by the take-up lever
hen moving from the upper to the bottom dead centre to get
a controlled passing of the thread through the hook. The
auxiliary guide (14) maintains the upper thread in front of the
needle in a tensioned condition and helps against pulling the
thread from the needle after thread trimming.
3.4.2 Setting the tension of the main and auxiliar
tensioners
The tension of the main thread tensioners is regulated by
means of the nuts (1). The force of tensioning the thread is
measured by the dynamometer (2) as it is sho n on the
illustration. The size of this force differs according to the
category, and its orientation value is indicated in the par. 11.2.
The tension of the auxiliary tensioner is regulated using the
nut (3). It should be the least possible, but sufficient for
unthreading the thread from the se n material hen removing
the se n material from the pressing element ithout leaving
the tensioner.
3.4.3 Setting the tensioning mechanisms
of the main tensioners
In the rest position of the tensioners, hen pushing the plate
of the tensioners on the spot A 3.4.1, this plate must have
the socalled dead travel of about 0,5 mm. At this lifting, the
tension discs of the tensioners must not be relieved. This can
be attained by a suitable shaping of the relieving disc of the
tensioners - this has been set up in the manufacturing factory.
In the maximum opened position of the tensioners, the plate
of the tensioners, hen pushing it at the spot A 3.4.1, must
still have the minimum lifting. This can be attained hen axially
shifting the lever (3) ith the roller (5) on the shaft (4).
The disengagement of the main tensioners must be
coordinated ith the top roller lift. To achieve this, turn the
lever (3) ith the roller (5) on the shaft (4). The movement of
the roller (5) on the slanting surface (6) of the lever (7)
disengages the tensioners. In this ay, also alag of the upper
thread tension disengagement after the top roller lift can be
obtained.
Caution ! Danger of injur !
S itch off the main s itch! Before starting the
setting operation, ait until the motor stops!
-Remove the rear cover ith the top roller lift magnet.
- Loosen the scre s (1) and (2) of the lever (3).
3
4
5
610
A
7
2
1
13
12
14
8
2
3
1
4 1 7
3 2 5
8
0,1
6
9