Brother B706, B707, B714, B716, B747 Service Manual

CONTENTS

~MECHANISM~

OJ

Upper shaft and needle

................................ .

bar

mechanism

[I] Lower shaft and rotary hook

mechanism ..........................................

[I]

Feed mechanism ( 8714/ 8716/ 8747) .... 2

[I]

Feed mechanism (8706/ 8707) .............. 3

..

0 Lubrication mechanism ........................ 4

[I]

Thread

[]]

Thread tension release lever

(8707/8716/8747)................................ 9

[I]

Thread wiper mechanism ..................... 9

[!]

Quick-back mechanism ........................ 9

[]]

Automatic presser lifter mechanism ..... 9

trimmer

mechanism ................. 6

~ASSEMBLY~

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Needle

[I]

Feed mechanism (8706/ 8707) ..............

I1J

Feed mechanism

[I]

Thread

0

Rotary

bar

trimmer

hook.........................................

......................................

............................................

(8714/

....................................

8716/ 8747) ....

[I] Presser mechanism ...............................

[]]

Cover....................................................

~ADJUSTMENTS~

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Needle

adjustments ..........................................

I1J

Feed

and

rotary hook timing

dog

height adjustment .................

............................. 20

14

15

16

17

18

19

20

21

~DISASSEMBLY~

OJ

Cover....................................................

I1J

Presser..................................................

[I]

Rotary hook ......................................... II

0 Thread

[I]

Feed. mechanism

[I]

Feedmechanism(8714/B716j8747)

[]]

Needle

trimmer

bar

mechanism .........................

..............................

.................................... II

(8706/

8707) ..............

....

10

12

13

[I]

Feed timing adjustment ........................

0 Presser height adjustment .....................

[I]

Synchronizer adjustment ......................

[]]

Thread trimmer

[I]

Tension release lever adjustment ..........

[!]

Thread wiper adjustment......................

[]]

Automatic presser foot lifter

(

-900;

electromagnetic type) ...............

~TROUBLESHOOTING

~djustment

..................

adjustment

GUIDE~...

21

22

23

24

25

[I] Upper shaft and needle bar mechanism

I. When the pulley 0

8

and

causes the

2.

The

movement

counter

3.

The The

4.

weight. needle needle

bar bar

turns

in the direction indicated by

counter

is

transmitted

weight 8

8 connected

is

guided by needle

to

the needle

to

the needle

to

turn.

bar

bushing U 0

the

arrow,

connecting rod 8 via the needle

bar

clamp 8 is

and

moved

needle

[I] Lower shaft and rotating hook mechanism

the

movement

up

bar

is

bar

and

down.

bushing D

transmitted

crank

8 connected

0.

to

the

upper

shaft

to

the

I. When the pulley 0

gear 8 mounted

bevel

G.

shaft

2.

The

movement

8

to

the

lower

3.

The

rotary

hook 0

turns

in the direction indicated by

to

the

upper

shaft 8

is

then

transmitted by vertical shaft bevel

shaft

0 via the lower shaft bevel

is

then caused

to

rotate in a full circle by the lower shaft

to

vertical

the

arrow, the movement

shaft

bevel

gear

D 8 mounted

gear

8.

-I-

gear

U 8

is

transmitted by the

mounted

on

the

on

the

bottom

0.

upper

top

of

the vertical

of

the vertical shaft

shaft

[I] Feed mechanism

•

(8714/8716/8747)

----

---

I. When the pulley 0 turns in the direction indicated by the arrow, vertical movement

cam

8 mounted

2.

The

horizontal feed rocker

3. The feed rocker shaft

4.

The

5.

The horizontal feed shaft & connected

6.

The

7.

The movement

bar 8 is

crank rod fi)

horizontal feed

to

the

upper

shaft 8

arm

8 connected

moved back and forth by the horizontal feed

to

the forked connector 8 via the feed cam sleeve

to

8.

is

moved up and

arm

Cl

connected

of

the feed dog mounted

down

by

to

the

to

the feed shaft &

to

the feed

the feed cam

crank

----

the forked connector 8

rod ~ is

bar 8 is

_...---

is

then moved in a circular arc.

bar

shaft 0 mounted

8.

then moved

is

also moved in a circular arc.

determined by the combined action

in

i circular arc.

is

transmitted by the feed

G.

to

the horizontal feed

of

steps 3 and 6.

-2-

(}] Feed mechanism

(8706/8707)

.

~

I. When the pulley 0 turns in

and

down

by

the

level feed eccentric wheel 8

2.

The

feed rocker

level feed connecting rod

3.

The

feed

4.

The

vertical feed connecting

upper

shaft

5.

The

feed lifting

6.

The

feed

7.

The

movement

6.

shaft

bar 0 is

f).

rocker

bar 0 is

oft

arm

moved back

shaft

moved up

he feed

dog

the

direction indicated by the

mounted

0 is moved in a circular

8.

and

forth by the wick hanger 0 mounted

rod

6)

is

moved up

arm

• is moved in a circular

and

down

by the feed lifting

G)

mounted

to

the feed

and

arrow,

to

arc

by the level feed

down

by the vertical feed eccentric wheel

arm

bar 0 is

the level feed connecting rod 8

the

upper

shaft

f).

arm

link assembly 0 mounted

to

arc

by the vertical feed connecting rod 6).

4D

mounted

determined by the combined action

to

the feed

the

rocker

shaft

Gi)

mounted

feed lifting rocker shaft

of

is

moved up

to

f).

steps 3

to

the

G)

and

.

-3-

[!] Lubrication mechanism

1.

Upper shaft oil supply

(I)

The

oil from the from there The

oil dispersed

(2) An oil adjusting valve

arm

via the counterweight

(3) Felt

(4) The oil

(5) (6)

is

mounted

supplied

and The The

to

that

D via the oil wick

oil

is

oil

that

pump

is

supplied

in

on

the needle the needle accumulates in the thread take-up shield

held inside by the

accumulates

8 passes

to

upper

the

arm

8

is

provided and

bar

connecting rod.

8.

rubber

at

the dip in the

through

shaft bushing L 8

column

needle

bar

is

supplied

at

the left end bar

crank

stopper

upper

crank.

in

8 in the pulley presser screw

arm

shaft bushing M

and

to

the feed adjuster.

of

the

order

to

prevent excess oil discharge

is

supplied

is

drawn

8,

upper

shaft bushing R

upper

shaft,

to

the needle

back

to

enters the center

and

oil

is

barO

at

the right end

the

pump

8 via a felt

of

8.

supplied

or

oil clogging,

and

Upper shaft

the upper shaft,

to

the

thread

and

needle

bar

bushings U

of

the

upper

and

a tube.

and

take-up

oil

is

shaft.

-4-

2.

Lower shaft oil supply

Lower shaft

(I)

The

oil

is

supplied

(2)

Part

of

the oil

from

Also,

the

oil ejected

vertical feed The

(3)

0,

oil dispersed in

and

shaft

the

vertical feed

8 via a wick.

3. Pump mechanism

When

the

vanes

at

the

shaft

turn,

the

centrifugal

through expelled chambers

In

pump dip

the

hole

in the center.

from

the

outlets

to

the

various

addition, a plunger

body

draws

oil which

in

the

arm

back

by

lower

from

the

to

the

pump

shaft

lower

ar.,m

column

shaft

bottom

force

sucks

at

the

ends

oil tubes.

pump

attached

accumulates

pump.

to bushing

shaft

8 via

of

the

The

oil

of

the

lower

bushing

is

supplied

the

vertical

the

oil

is

the

spinal

to

in

L

f)

arm

up

then

the the

shaft

and

flows

L

f)

is supplied

to

lower

channel.

lower

through

shaft

the

lower

to

the

bushing

shaft

horizontal

R

0,

L

f).

to

the

feed

the

horizontal

rotary

rocker

----Pump

____

hook.

shaft 0 and

feed

rocker

body

Rotating vanes

the

shaft

-5-

(}] Thread trimmer mechanism

1 . Thread trimmer mechanism

As shown mechanism consists

fixed knife

movable knife holder

assembly

trimmer cam lever assembly

0,

2.

Operation of the trimmer mechanism(The following illustrations are with the high-speed rotating

hook

(I)

Condition during high-speed operation

in

the illustration, the thread trimmer

0.

a lower thread finger

8.

the trimmer forked shaft

and

the trimmer solenoid

removed.)

of

the movable knife

G. the knife holder

8,

the trimmer

8.

0,

8.

the the

the

cam

* Because the trimmer cam lever assembly 8

f),

return spring knife holder

In addition, the trimmer lever 8

does not move.

(2) Condition when a trim signal

* When the foot Pedal

cam lever shaft trimmer

cam

the trimmer cam lever assembly 8 does not engage with the trimmer

8 does

lever shaft

not

function.

is

pressed by the trimmer lever spring

is

input

is

depressed again

G).

The roller shaft (right side)

G)

moves

around

and

is

kept pressed toward the trimmer 'solenoid 8 by the cam lever

the trim signal

of

the trimmer

the outside

of

cam 0 and

,.

CD

so

that

the movable knife holder 8

is

input, the trimmer solenoid 8 pushes the trimmer

cam

lever assembly 8

the trimmer

cam

0.

that

the movable

is

connected

to

the

-6-

(3) Movement

*

When transmitted

*

The

movement

lever 0

*

The

movable knife 0

overlaps with the fixed knife

(4)

Trimming

the

lower shaft

to

mounted

completion

of

the

trimmer

is

transmitted

to

trimmer

turns

the

mounted

holder

and

the

trimmer

forked

trimmer

shaft

to

the

trimmer

forked

to the movalbe knife

8.

and

stop

cam

0 pushes the roller

8 via the

connecting

shaft

8.

shaft

(right side)

trimmer

holder

cam

rode

lever assembly

and

the movable knife

8.

8 moves in the direction indicated by the

upward,

holder

the

movement

8 via the

arrow

is

trimmer

and

* When

*

(5)

the

trim signal stops, t'he

cam

lever

return

spring

G),

came.

The

trimmer

directions indicated by the

Thread

connecting rod

trimmer

safety device

0

* If the moving knife 0 does

8

and

the

trimmer

needle.

assembly in

contact

with

trimmer

and

the toller

fD

and

arrows)

not

return

cam

solenoid 8 returns, the

shaft

oft

he

the movable knife

by

the

trimmer

to

its original position, the

8 function

to

return

trimmer

lever

cam

holder 8 are

spring

the

movable knife 0

trimmer

cam

lever assembly 8

lever assembly 8 separates

returned

to

their original positions (in

CD.

return

pin (left side)

to

a position where it will

of

the

is

pushed by the

from

the

trimmer

cam

lever

not

come

the

-7-

---

(I)

The

needle rises to a point 2.2 mm above the lowermost point and the tip loop formed by the needle.

----~~

of

the

rotary

hook

the

(2)

The

trim signal

causes the movable knife

is

thread through

Bobbin

caught

the inner hook.

thre~~

is

input.

by the

and

to

rotary

the

move.

hook

trimmer

The

and

cam

needle

passes

(3)

The

tip

of

the movable knife goes

of

the tip At the movable knives

If

the timing for the above operation

errors in

the rotary hook

this time, the thread take-up

as

thread

trimming may occur.

into

at

the needle hole plate,

is

slightly above the lowermost position

shown

in

the illustration.

~

Needle thread

I

Fixed knife r

the

triangular

is

too early. it will affect the loop spreading

loop formed by the needle and and

spreads the needle

'

and

Needle thread

Movable knife

bobbin

and

bobbin threads.

the needle thread

of

·'

threads divided by

the movable knives

is

separated by

and

(4)

The

needle

and

bobbin threads hooked by the movable knife in step (3)

shape

of

the knife.

fixed knife.

At this time, the thread take-up At the same time

thread

Note needle thread stitch the next time sewing

out

that

smoothly

the

and

as

that

the knife

and

amount

and

of

thread

in the bobbin case

they

are

spread

is

spreading

prevent excessive slack.

determined

is

begun.

out

almost

at

out

at

after

thread trimming,

gradually by the thread spreader, they

the uppermost position.

the thread, the tension release lever functions to let the needle

the movable knife becomes the length

and

this in

-8-

are

spread

turn

influences the composition

out

of

thread

to

a fan shape by the

are

cut by the tip

of

the

remaining for the

of

the

Brother B706, B707, B714, B716, B747 Service Manual

Specifications and Main Features

Frequently Asked Questions

User Manual