JUKI lbh-1790 series Engineer's Manual page 37

Adjustment Procedures
Adjust and fix the position of bobbin winder driving wheel 2 with
the setscrew so that a clearance of 0.5±0.2 mm is provided
between rubber ring 1 and bobbin winder driving wheel 2 in the
state that the bobbin thread is not wound.
(Caution) When using the bobbin winder for a long period of
time, rubber ring 1 will wear down and slip. As a
result, bobbin thread may not be wound. At this
time, adjust and fix the position of bobbin winder
driving wheel with the setscrew.
Adjustment Procedures
1. Adjust so that thread breakage detecting plate 1 comes in
contact with thread take-up spring 2 without fail when the
machine head is not threaded. (Slack of the thread take-up
spring has to be 0.5 mm.)
2. When the stroke of thread take-up spring 2 has been changed,
loosen screw 3 and be sure to adjust thread breakage detecting
plate 1.
(Caution) Adjust so that thread breakage detecting plate 1
does not come in contact with any metallic part
(thread tension disk, etc.) other than thread take-
up spring 2.
Results of Improper Adjustment
™ If the pressing pressure is low,
rubber ring 1 slips and bobbin
thread may not be wound.
™ If the pressing pressure is high,
wear of rubber ring 1 is
increased.
Results of Improper Adjustment
™ If the detecting plate does not
come in contact with the spring,
the needle thread breakage
cannot be detected and the cloth
cutting knife works.
™ If the contacting force is too
strong, early breakage of the
thread take-up spring 2 will
occur.
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