Brother Db2-b714-3 Instruction Manual

							
From  the library  of: Superior  Sewing Machine  & Supply  LLC  
						

							CONTENTS 
~MECHANISM~ ................................ . ~ASSEMBLY~ ...................................... 14 
OJ Upper shaft and needle bar mechanism OJ Needle bar ............................................ 14 
[I] Lower  shaft and rotary  hook [I] Feed mechanism (8706/  8707) .............. 15 
mechanism  .......................................... .. 
I1J Feed mechanism (8714/ 8716/  8747)  .... 16 
[I] Feed mechanism  ( 8714/  8716/ 8747)  .... 2 
[I] Thread trimmer .................................... 17 
[I] Feed mechanism (8706/  8707) ..............  3 
0 Rotary hook......................................... 18 
0 Lubrication  mechanism ........................  4 
[I] Presser mechanism ............................... 19 
[I] Thread trimmer mechanism  .................  6 
[]] Cover.................................................... 19 
[]] Thread tension  release lever 
(8707/8716/8747)................................  9 
~ADJUSTMENTS~ ............................. 20 
[I] Thread wiper mechanism  .....................  9 
[!] Quick-back mechanism ........................  9 
OJ Needle and rotary hook timing 
adjustments  .......................................... 
20 
[]] Automatic presser lifter mechanism  ..... 9 I1J Feed dog height  adjustment  ................. 21 
~DISASSEMBLY~ .............................. 10 [I] Feed timing  adjustment  ........................ 21 
0 Presser height adjustment  ..................... 21 
OJ Cover.................................................... 10 
[I] Synchronizer  adjustment ...................... 22 
I1J Presser.................................................. 10 
[I] Rotary hook ......................................... II 
[]] Thread  trimmer ~djustment .................. 23 
[I] Tension  release lever adjustment  .......... 24 
0 Thread trimmer .................................... II 
[!] Thread wiper adjustment...................... 24 
[I] Feed. mechanism (8706/ 8707) .............. 12 
[]] Automatic  presser foot lifter adjustment 
[I] Feedmechanism(8714/B716j8747) .... 13 ( -900; electromagnetic  type) ............... 24 
[]] Needle bar mechanism  ......................... 13 ~TROUBLESHOOTING GUIDE~... 25 
From  the library  of: Superior  Sewing Machine  & Supply  LLC  
						

							[I] Upper shaft and needle bar mechanism 
I. When  the pulley 0 turns in the  direction  indicated  by the arrow, the movement is transmitted to the upper shaft 
8 and causes the counter weight 8 to turn. 
2. The movement is transmitted to the needle bar connecting  rod 8 via the  needle bar crank 8 connected to the 
counter weight. 
3. The needle bar 8 connected to the  needle bar clamp 8 is moved up and down. 
4. 
The needle bar is guided  by needle bar bushing U 0 and needle bar bushing  D 0. 
[I] Lower shaft and rotating  hook mechanism 
I. When  the pulley 0 turns in the  direction  indicated  by the arrow, the movement is transmitted  by the upper shaft 
bevel 
gear 8 mounted to the upper shaft 8 to vertical shaft bevel gear U 8 mounted on the top of the  vertical 
shaft 
G. 
2. The movement is then transmitted  by vertical  shaft bevel gear D 8 mounted on the bottom of the vertical  shaft 
8 to the lower shaft 0 via the  lower  shaft bevel gear 8. 
3. The rotary hook 0 is then caused to rotate  in a  full  circle  by the  lower  shaft 0. 
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From  the library  of: Superior  Sewing Machine  & Supply  LLC  
						

							[I] Feed mechanism (8714/8716/8747) 
• 
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_...--­----
I. When  the pulley 0 turns  in the  direction  indicated  by the  arrow,  vertical  movement is transmitted  by the  feed 
cam 
8 mounted to the upper shaft 8 to the  forked  connector 8 via the  feed  cam  sleeve G. 
2. The horizontal  feed rocker arm 8 connected to the forked  connector 8 is then moved  in a circular  arc. 
3.  The  feed 
bar 8 is moved  back and forth  by the  horizontal  feed bar shaft 0 mounted to the horizontal  feed 
rocker  shaft 
8. 
4. The crank rod fi) is moved  up and down by the  feed  cam 8. 
5. The horizontal  feed shaft & connected to the crank rod ~ is then  moved in i circular  arc. 
6. The horizontal  feed arm Cl connected to the feed  shaft & is also moved  in a circular arc. 
7. The  movement of the feed  dog mounted to the feed bar 8 is determined  by the  combined  action of steps 3 and  6. 
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From  the library  of: Superior  Sewing Machine  & Supply  LLC  
						

							. ~ 
(}] Feed mechanism (8706/8707) 
I. When  the pulley 0 turns  in the direction  indicated  by the arrow, the  level  feed connecting  rod 8 is moved up 
and down by the level feed eccentric  wheel 8 mounted to the upper shaft f). 
2. The feed rocker shaft arm 0 is moved  in a circular arc by  the  level  feed arm link assembly 0 mounted to the 
level  feed connecting  rod 
8. 
3. The feed bar 0 is moved back and forth by the  wick  hanger 0 mounted to the feed rocker shaft f). 
4. The vertical  feed connecting rod 6) is moved  up and down by the  vertical  feed eccentric  wheel Gi) mounted to the 
upper shaft f). 
5. The feed lifting rocker shaft arm • is moved  in a circular arc by  the  vertical  feed connecting  rod 6). 
6. The feed bar 0 is moved up and down by the  feed  lifting arm 4D mounted to the feed lifting  rocker  shaft G) . 
7. The movement oft he feed dog G) mounted to the  feed bar 0 is determined  by the  combined  action of steps 3 and 
6. 
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From  the library  of: Superior  Sewing Machine  & Supply  LLC  
						

							[!] Lubrication mechanism 
1. Upper shaft oil supply 
Upper shaft 
(I) The oil from  the pump 8 passes through upper shaft bushing M 8, enters  the center of the  upper  shaft, and 
from there is supplied to upper shaft  bushing L 8 and upper shaft bushing R 8. 
The oil dispersed in the arm column is supplied to the  feed  adjuster. 
(2)  An oil adjusting  valve 
8 is provided at the left  end of the upper shaft, and oil is supplied to the thread take-up 
arm via  the  counterweight and needle bar crank. 
(3)  Felt 
is mounted on the needle bar crank in order to prevent  excess oil discharge or oil clogging, and oil is 
supplied to the  needle bar connecting  rod. 
(4)  The  oil 
that accumulates  in the  thread  take-up  shield is supplied to the needle barO and needle bar bushings U 
and D via  the  oil wick 8. 
(5) The oil is held  inside  by the rubber stopper 8 in the  pulley  presser  screw at the right  end of the upper shaft. 
(6) 
The oil that accumulates at the  dip  in the arm is drawn back to the pump 8 via  a felt and a tube. 
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From  the library  of: Superior  Sewing Machine  & Supply  LLC  
						

							2. Lower shaft oil supply 
Lower  shaft 
(I) The oil is supplied by the pump to the lower shaft and lower shaft bushing L f). 
(2) Part of the oil from lower shaft bushing L f) flows through the lower shaft to the rotary hook. 
Also, the oil ejected from lower shaft bushing L f) is supplied to the horizontal feed rocker shaft 0 and the 
vertical  feed shaft 8 via a wick. 
(3) 
The oil  dispersed  in the ar.,m column is supplied to lower shaft bushing R 0, the horizontal feed rocker shaft 
0, and the vertical feed shaft 8 via the arm channel. 
3. Pump  mechanism 
When the vanes at the bottom of the vertical 
shaft turn, the centrifugal force sucks the oil up 
through the hole in the  center. The oil is then 
expelled from the outlets at the ends of the spinal 
chambers to the various oil tubes. 
In addition, a plunger pump attached to the 
pump body draws oil which accumulates in the 
dip in the arm back to the pump. 
-5-
----Pump body 
____ Rotating 
vanes 
From  the library  of: Superior  Sewing Machine  & Supply  LLC  
						

							(}] Thread trimmer  mechanism 
1 . Thread  trimmer  mechanism 
As shown in the  illustration,  the thread  trimmer 
mechanism  consists 
of the movable  knife 0, the 
fixed  knife 
0. a lower  thread  finger 8. the 
movable  knife holder 
G. the knife  holder 
assembly 
8. the  trimmer  forked shaft 8. the 
trimmer  cam lever  assembly 
8, the trimmer cam 
0, and the  trimmer  solenoid 8. 
2. Operation  of the  trimmer  mechanism(The  following illustrations  are with  the high-speed  rotating 
hook removed.) 
(I) Condition during high-speed  operation 
* Because the trimmer  cam lever  assembly 8 is kept pressed  toward the trimmer  solenoid 8 by the  cam  lever 
return  spring 
f), the trimmer  cam lever  assembly 8 does not engage  with the trimmer cam 0 and the movable 
knife  holder 
8 does not function. ,. 
In addition,  the trimmer  lever 8 is pressed by the  trimmer  lever spring CD so that the movable  knife holder 8 
does not move. 
(2)  Condition  when a trim  signal 
is input 
* When  the foot  Pedal is depressed  again and the trim  signal is input,  the trimmer  solenoid 8 pushes the trimmer 
cam  lever  shaft 
G). The roller  shaft (right  side) of the trimmer cam lever  assembly 8 that is connected to the 
trimmer 
cam lever  shaft G) moves around the outside of the  trimmer cam 0. 
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From  the library  of: Superior  Sewing Machine  & Supply  LLC  
						

							(3) Movement of the trimmer holder 
* When the lower  shaft turns and the trimmer cam 0 pushes  the roller shaft (right  side) upward, the movement is 
transmitted to the trimmer forked shaft 8 via the trimmer cam lever  assembly 8. 
* The movement is transmitted to the trimmer connecting rode and the movable  knife holder 8 via the trimmer 
lever 0 mounted to the trimmer forked shaft 8. 
* The movable  knife 0 mounted to the  movalbe  knife holder 8 moves in the  direction  indicated  by the arrow and 
overlaps  with the fixed  knife 8. 
(4) Trimming completion and stop 
* When the trim signal  stops, the trimmer solenoid 8 returns,  the trimmer cam lever assembly 8 is pushed  by the 
cam lever return spring G), and the  toller shaft oft he trimmer cam lever  assembly 8 separates from the trimmer 
came. 
* The trimmer connecting  rod fD and the movable  knife holder 8 are returned to their original  positions  (in the 
directions  indicated by the arrows) by the trimmer lever spring CD. 
(5) Thread trimmer safety  device 
0 
* If the  moving  knife 0 does not return to its original  position,  the return pin (left  side) of the trimmer cam lever 
assembly 
8 and the trimmer cam 8 function to return the movable  knife 0 to a position  where it will not come 
in contact with the needle. 
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From  the library  of: Superior  Sewing Machine  & Supply  LLC  
						

							----~~ 
---
(I) The needle rises to a point  2.2 mm  above  the 
lowermost  point and the tip 
of the rotary hook the 
loop  formed  by the  needle.  (2) 
The trim 
signal is input. and the trimmer cam 
causes  the movable  knife to move. The needle 
thread 
is caught by  the rotary hook and passes 
through the  inner  hook. 
Bobbin thre~~ 
~ Movable  knife 
~ Needle thread I I  Fixed knife r 
(3) The tip of the movable  knife goes into the triangular loop formed  by the  needle  and bobbin threads  divided  by 
the  tip 
of the  rotary  hook at the needle  hole plate, and spreads  the needle and bobbin  threads. 
At this time,  the thread  take-up is slightly  above the lowermost  position and the needle thread is separated  by 
the  movable  knives 
as shown in the illustration. 
If the timing  for the  above  operation is too early.  it will  affect  the loop  spreading of the movable  knives and 
errors in thread trimming  may occur. · 
Needle  thread 
(4) The needle and bobbin threads  hooked  by the  movable  knife in step  (3) are spread out to a fan  shape  by the 
shape 
of the  knife. and as they are spread out gradually  by the  thread  spreader, they are cut by the  tip of the 
fixed  knife. 
At  this  time,  the thread  take-up 
is almost at the uppermost  position. 
At  the  same  time 
that the knife is spreading out the thread,  the tension  release lever functions  to let  the  needle 
thread 
out smoothly and prevent  excessive  slack. 
Note 
that the amount of thread determined at the  movable  knife becomes  the length of thread remaining  for the 
needle  thread 
and in the  bobbin  case after thread trimming, and this in turn influences  the composition of the 
stitch  the next  time sewing 
is begun. 
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From  the library  of: Superior  Sewing Machine  & Supply  LLC