Brother LH4-B800E Service Manual page 18

[Tack tension control]
!0
1. When the pulse motor q operates, the gear w that is installed to the pulse motor shaft engages with the presser
driving arm e so that the guide bracket r moves along the guide shaft t and moves the presser driving arm e
in the direction of the arrow.
2. The presser driving arm e causes the presser foot lifter connecting rod y to move in the direction of the arrow.
3. The movement of the presser foot lifter connecting rod y is transmitted via the knee lifter lever u to move the
upper thread trimmer driving link i in the direction of the arrow.
4. The needle roller !0 that is secured to the end of the tension release driving lever o is linked to the cam groove of
the upper thread trimmer driving link i, so that when the upper thread trimmer driving link i operates, the
tension release driving lever o that is secured to the tension release shaft !1 moves in the direction of the arrow.
5. The tension release cam !2 is secured to the end of the tension release shaft !1 , and so the tension release cam
!2 moves in the direction of the arrow.
6. When the tension release cam !2 presses against the tension release pin !3 , the tension release pin !3 presses
against the tension disc presser !4 to release the tension discs.
o
!2
!1
!3
!4
i
r
u
0 0
q
LH4-B800E
1. MECHANISM DESCRIPTION
t
w
y
e
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