Needle Strikes Upper Thread Trimmer - Brother LH4-B800E Service Manual

5-11. Needle strikes upper thread trimmer

Cause
Upper thread Upper thread trimmer
trimmer assembly position
assembly
Upper thread scissors
operating force
Longitudinal Longitudinal feed arm
feed arm position
Thread take- Upper shaft pulley
up position in stopping position
stopped
condition
Cam Upper thread scissors
opening timing
adjustment
Opening cam Upper thread scissors
gradual opening timing
Presser foot Presser foot home
home position sensor
position position
sensor
Upper thread Upper thread trimmer
trimmer lever lever operating force
Check
Refer to "5-8. Needle thread runout"
Adjust so that scissors
M open when the
projection is pressed
with a force of 4 N or
less, and remove any
scratches and burrs.
Adjust properly
Refer to "5-8. Needle thread runout Machine stopping position"
The cam should open
the stop plate properly.
Refer to "4-13-7. Adjusting the upper thread scissors gradual opening
timing"
After setting to the
home position, press
the RESET key to
lower the presser foot,
and adjust so that the
distance from the
upper thread trimming
scissors to the center
of the needle is 5.5 -- 6
mm at this time.
The upper thread
trimmer lever should
gently open when the
stop plate is separated
from the stopper.
Solution
Move the upper thread trimmer
driving link so that it stops at the
face plate.
In this position, tighten the eye bolt
so that the small slot in the upper
thread trimmer lever and the edge
of the washer are aligned.
Refer to "4-13-8. Adjusting the upper thread
scissors opening timing"
LH4-B800E
5. Troubleshooting guide
page
4 N
4-13
Aligned
Upper thread
trimmer lever
Washer
4-5
5.5 - 6 mm
-
-
5 - 11