Brother DB2-B705-100 User manual

SERVfCE MANUAL
FOR
BROTHER MODEL DB2-B705
-1 00·-200·-400·-500
(
BROTHER INDUSTRIES, LTD.,
NAGOYA, JAPAN .
\
r ----
From the library of: Superior Sewing Machine & Supply LLC

•
PREFACE
Thi s service ma nual is made for the purpo se of ge tting acquai nted with our n ew ly de signed thread
tr imm er se ri es, BROTHER Model 08 2-8705-100 Se ries.
No r ma l troubl es oc cur in your sew ing r oo m will be so lved wi th the kn ow l edge of in st ruction manual
enclosed
wit h th e machine, however, in or der to get much m ore pe rf ec t kno wl edge on this machine,
this
se rvi ce manua l ma y be helpful for your bette r maintenance. We duly h ope that you get fu ll
know l ed ge on t hi s machine by t hi s se rvi ce manual as we ll as in struction man u als and part s cata l og ues.
Incide
nt a ll y, this covers the d es cription on our newly developed BROTHER Needle Positioning Motor,
however, if you u
se wit h ot her br an's , pi ease refer to one pub li shed by tho se manufa cture r.
We sincerely hope th at you wi ll ove r co me the tro ubles which may ar i se in your factory wi th this
pamp hl et.
BROTHER I NDUSTR IES, LTD .
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CONTENTS
1. Features.......................................................................................................................... 1
2. Specifications................................................................................................................... 2
3. Narne of major components.............................................................................................. 3
4. Thread trimming mechanism............................................................................................. 3
5. Construction chart of Brother N. P. Motor .... .. ...... .. ............................................ .. ... .. .. .. ... 8
6. Electric circuits................................................................................................................ 9
7. Setting up the machine ....................... .. ................................................. .. ........................ 13
8. Test running ................................................................................................................... 17
9. Sewing tensions................................................................................................................ 18
10. Adjusting on sewing machine ............................... .. ................................ .. ........................ 20
(1) Adjusting thread trimming mechanism .......................................................................... 20
(2) Adjusting tension releaser .................................................................. .. ........................ 24
(3) Adjusting thread wiper ................................................................................................ 25
(4) Adjusting qichback device............................................................................................ 25
(5) Adjusting presser lifter ................................................................................................ 26
(6) Adjusting synchronizer................................................................................................. 27
11. Adjusting motor ............................................................................................................... 28
12. Maintenance of motor ...................................................................................................... 31
13. Trouble shooting ........................... .. ... .. ......................... .. ...................... .. ........................ 35
(1) In relation with the sewing machine bead..................................................................... 35
(2) In relation with control box and N. P. Motor .... .. .. ..... .. .......... .. .......... .. ................... .. ... 37
From the library of: Superior Sewing Machine & Supply LLC

1. Features
(Head)
1.. It ensures high graded sewing conditions and perfect durability at maximum high speed of 4,500
stitches per minute.
2. It is equipped with built-in bobbin winder with compact design and high performance.
3. Belt cover is equipped with as standard accessories, thus it ensures operators' safety.
4. Plunger pump is adopted on this machine, thus it ensures perfect oil return to oil reservoir even
at slow speed operation. This pump can be easily disassembled by the mechaics.
(Thread trimming mechanism)
5. Simple thread trimming mechanism is adopted on this machine, so that it is quite easy adjustment
and maintenance and it also features very safe construction.
6. Stable thread trimming jobs can be obtained because of the thread trimming mechanism driven
by lower shaft.
7. Rotary knife around rotary hook is adopted to do faster trimming jobs and thread tails are
shortened considerably
in co~parison with the conventional machine.
8. All accessories including feed dogs, presser feet and needle plates can be used with this machine
in other words, such parts are common with other lock stitch sewing machines.
9. Built in thread wiper ensures much productivity. (-200)
10. The solenoid reverse mechanism operates with a soft touch and permits even the beginner to sew
backward easily. (Type
400 specifications)
11. The pneumatic thread cutter sewing machine has a presser lifter which can be controlled with a
single pedal operation and thus prevents operator fatigue. (Type
500 specifications)
(N.P. Motor)
12. This motor is newly designed with clutch mechanism on slow speed motor with the speed of
215 r.p.m., thus it ensures faster actions of thread trimming and stopping jobs.
13. Even the beginner can use this machine with single treadle pedal for inching, sewing, needle up
and down position and thread trimming.
14. Synchronizer is designed with "Lead Switch" and all control circuits are not used with relays, thus
its reliability and durability are very high.
15. Printed Circuit Boards (P.C.B.) are very easy to change and all components are designed to do so,
which ensures easy maintenance.
- 1 -
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Spacifications
DB2-B705-100 DB2-B705-200 DB2-B705-400 DB2-B705-500
Means of thread trimming Electro-magnetic,
rotary knife system thread trimming device.
Means of thread releasing Electro-magnetic solenoid
Thread wiper Nil Equipped
Quick back Nil Nil Solenoid
type Air type
Aut refuter presser foot Nil Nil Nil
Air type
High speed: 4,500 s.p.m.
Sewing speed
Slow speed:
215 r.p.m.
Rotary hook Specially designed hook
"BROTHER" Needle Positioning Motor; or the like.
Motor
MD-931-811 MD-931·812 MD-931-814 MD-931-815
3 phase 400W
(NOTE)
1. Single phase motor is of different specs.
2. Specs. on machine head is referred to the instruction manual of Model DB2-B705.
- 2-
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3. Name of major components
This machine is componed of the following
components.
(1) Head
a. Head
b. Thread trimming mechanism
c. Treadle pedal
d. Tension releaser
e. Synchronizer
f. Thread wiper (Optional parts for -200)
(2) Control box
(3) Needle Positioning Motor
4. Thread trimming mechanism
(1) Construction
As per Fig. 1, there are composed of thread
trimmer clutch
0. Holder fj, Knife 0. Lower
thread finger
G. Holder plate e. Stopper C),
and Solenoid fj.
(2) Procedures
I) At high speed
As per Fig.
2·1, stopper presses down
cam and holder is stationed.
- 3-
Fig. 1
1~1-
Fig. 2·1
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II) At thread trimming signal comes from synchro-
nizer
With your heel, when you presses down the
treadle pedal, synchronizer will order to get
thread trimming signal, solenoid is going to pull
its plunger and stopper, then cam jumps up with
the aid of the spring action. (Fig.
2-2)
III) Holder's rotation
When the cam jumps up, its pin 0 is located in
the same circumference with the projected portion
of clutch
(li), thus holder rotates together with
clutch.
At
that time, solenoid is already disengaged and
stopper is positioned
at its original position and
it contacts with the face of holder. (Fig.
2-3)
N) Just before ending thread trimming
As holder is rotating to the position of afore-
mentioned position ( I
), stopper is climbing up to
cam, thus cam is pressed down. (Fig.
2-4)
-4-
I>"<: I_.
I>< I.
Fig. 2-2
Solenoid OFF
I:>< I ..
Fig. 2-3
Solenoid OFF
0
c><L
r><J"'
Cam begins to press down
Fig. 2-4
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V) At ending thread trimming
Cam gradually pressed down is
out of the
circumference of clutch, then holder stops.
At
that time, the inertia of holder is absorbed
by stopper. (Fig.
2-5)
(3) How to be trimmed upper and lower threads
As per the afore-mentioned procedures, upper and
lower threads
are trimmed as follows:
I )
The hook point gets upper thread
At this time. needle comes up
2.2 mm from
its lowest position, but the signal for thread
timming is given
at its lowest position.
(Fig.
3-1)
II) Knife moves
Signal for thread trimming is given and by
the action of clutch, knife moves with
rotary
hook's rotation. (Fig. 3-2)
- 5 -
Solenoid OFF
1><1 ..
1><:1"'
Fig. 2-5
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III) Knife catches upper thread and lower thread
finger gets lower thread
The point of kinfe comes into upper and lower
threads which is separated by the
rotary hook
and the tringle-shaped loop which is formed by
needle hole of the needle plate, thus the upper
and lower thread is separated. (Fig.
3-3)
At this time, the thread take-up lever is positioned
at a bit higher point from its lowest position,
(upper shaft angle; appr. 330·) and
as per Figs.
3-4 and 3-5, the threads are separated.
In case of sooner or
later timing, it affects on
separation of upper and lower threads, then it
causes error of thread trimming.
- 6-
.. ")
Fig. 3-4
Fig. 3-5
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N) Upper and lower threads are trimmed
As per the above procedure, the upper and
lower threads which are caught by knife
holder are timmed by the sharp edge of knife
gradually expanded by their own shape.
At this time, the position of thread take-up
lever is up highest. Due to the shape of the
knife, not so as to be pulled the upper thread
with excessive tension, the tension releaser
is
functioned to release the upper thread without
any resistance.
The threads which were caught by knife and
holder are very much affected on the length
of threads out of needle eye and bobbin case,
and finally on the formation of the first stitch
at the beginning of the next stitch. (Fig. 3-6)
(4) Tension releaser
In case that the signal for thread trimming is
given, the tension release solenoid 0 is functioned,
pulled tension release lever
f), pushed tension
release bar 8 with the intermediate action of
connecting
bar 0 and plate 8 and opened tension
discs
(t.
In case that the signal for needle up position is
given the tension release solenoid is off, thus
tension discs
are closed. (Fig. 4)
(5) Thread wiper
In case that the signal for needle up position is
given, with the interval of 10-lOOms, the thread
wiper solenoid 0 is
on, thus thread wiper 0 is
functioned with the intermediate action of lever
0 and grooved link O·
In case that the thread wiper solenoid is off,
thread wiper returns to its original position with
the aid of spring. (Fig.
5)
- 7-
I>;=~=='
~--......._
Fig. 3-6
Fig. 4
Fig. 5
From the library of: Superior Sewing Machine & Supply LLC