Atlanta 4500A, Technical Manual & Parts Lists, Page: 73 / 166

Technical Manual & Parts Lists
65
l. On looper thread cam
As shown in the figure, when the No. 3 carved line of the needle bar comes to the bottom
surface of the needle bar lower bushing, make it so that the wire can be seen through the hole of
the matching hole of the cam. The timing of the looper thread cam can be adjusted by loosening
the screw B and after the position is determined tighten the screw securely.
After all adjustments are completed, verify the following:
Verify that when the looper thread came off from the protruded end (A) of the looper thread
cam, the needle point has completely entered the triangle of the looper thread.
To especially avoid the puckering, adjust the looper cam so that the bottom end of its matching
hole is aligned with the lower side of the wire with a little earlier timing, when the looper thread
will not be drawn too much and a favorable thread
tension will be obtained.
m. On the position of the take-up thread tension lever
When the needle bar is at the lowest point, if the
needle thread is pulled in by hauling motion by the
take-up thread tension lever, the needle thread
loop becomes big at the scooping time of the needle
thread. In case of normal fine thread, lower the needle to
the lowest dead point.
n. On the frame thread eyelet
The thread tightening changes according to the
positions of the frame thread eyelet. When the frame
thread eyelet is lowered, the tightening of the looper
thread becomes weaker and if it’s raised up, the
tightening becomes stronger.
o. Function of the thread take-up tension plate
The thread take-up tension plate, which moves with
the needle bar, prevents the needle thread from forming an unnecessary loop in the opposite side
of the looper when the needle bar goes up to its highest position. A large loop is undesirable to
form uniform stitch. Therefore, the tension plate must apply the least amount of tension to the
thread only for surpassing the resistance produced between the thread and the cloth.
p. Function of the thread take-up tension disc
The take-up thread tension disc functions especially for preventing the stitches from skipping
during reverse stitching and production of chain-off threads.
It is very important to pull in the slack of the needle thread especially when the feed direction
is reversed. If a slackened needle thread remains on the cloth, it may be cut by the returning
needle or it may form an idle loop which results in stitch skipping. Another function of the take-