Pfaff 900 Service Manual

PFAFF

-900

Thread

Special

and

467/469

Service

List

Trimmer

Mechanism

High-Speed

Manual

Spare

for

Pfaff

and

Parts

461,

Seamers

463, 465,

467,

469

G.M.

PFAFF

AG•KAISERSLAUTERN

BRANCH

Operation

General

Since

the

high

sewing

great

demandsonthe

tion

can

onlybeachievedbyreducing

Fittingahigh-speed

both

threads

between

This

mechanism,

installedinmachines

not

interfere

in conjunction with a special motor with automatic needle positioner, this thread trimmer

eliminates

and

pulling

manipulate

action is triggered off and the threads are cut to the proper

threads

have

desired,

torsto sew

in the Stop motor starting lever.

Housing

of the machine (Fig. 27).

Arranged

the

Knife cam 2 imparts an oscillating motion to shaft Avia roller lever 9. fhis motion is trans

mitted to thread catcher11via clutch fork 7, trimmerengaging shaft 36. crank 10 and connec

tion the left pedal 26,the motorrotates the

point of its stroke and thread catcher11swings forward to trim the needle and bobbin

threads. Both threads are

and the thread catcher returns to its starting position.

The rear end of the left pedal 26 mustbe kept depressed

pleted.

A end of the seam

the machine or impairing the trimming action.

8 of the

right

endoflower

10.1.

mechanical

as a

with

the

all

superfluous

up,

positioningorholding

the

work.Bysimply

been

trimmed,

subcl.

-900

stitch-by-stitch

thread

concentrically

Each

trimming

interlocking

while

and

speeds

manual

seamer

withasubclass

sewing

hook

special

equipped

attachmentofspecial

movements,

Maintenance

attainedbymodern

dexterity

feature,isarranged

and

the

handling

and

machine

with

all

kindsoffeeding

feet,

suchasreaching

the

threads.Itleaves

depressing

the

work

can be

exchanged

machines

main

the

canbesupplied

at the

beginning

trimming

on the

action calls for an oscillating

trimmed

device

mechanismisscrewed

sewing

shaft

when the take-up lever has reached the top of its stroke

makes

machineisrunningatfull

and

hook,

machine

it possible to triggeroff the

high-efficiency

skillofthe

time.

-900

thread

feed

reduces

below

feed

dogs

forthe scissors or the balance

the

rear

and

withaninching

end

ofa

thread

catcher11is

motion.

pulley

until

speed,

sewing

machines

operators,

trimmer

the

which

the

handling

machine

any

increaseinproduc

automatically

time

toa

feed

and,

minimum.

hence,

mechanism.Inaddition,itdoes

and

needle

plates.

Supplied

both

endofthe

length.

the operator's

left

pedal,

Immediately

hands

the

trimming

after the

sewingberesumed,

device

which

enables

seam

and is

controlledbya

to the

undersideofthe

drivenbyknife

On depressing the rear end of

the needle has passed the lowest

until

the

trimming

without

causing

contact

bedplate

cam

action is

action at the

any damage to

make

trims

can

only

wheel

free

opera

2 at

com

Operation

(For Illustrations,

ensure

passed

through

To trim both threads, depress the causes

the right pedal 24 to swing down likewise, thus engaging the motor brake. In order

to relieve the left foot, it is advisable to depress both pedals with both feet simultaneously.

that

please

both

the

refer to pp. 18—20)

threads

additional

will be trimmed securely, check to

holeinthe

see

that the bobbin

bobbin

case.

rear

end of the left pedal 26. This pedal has a stop which

thread

the

rear

endofthe

cam 30 which

cone

21. The

engagement

switch ES, which is holder

17 and

nects

the

proper

rate required for the trimming action. Whiie the machine is still running at high

causes

amountoftension

with the control slot in knife cam 2. At the

synchronizer

motor

centrifugal switch 18 delays the trimmer engaging action until the machine

reduced to a The machine

safe

keeps

left

pedal

26 is

and

located

the

a spring to be

thus

accumulatedinthe

underneath

siip ring 16,

machine via a worm

depressed,

compressed

this

engages

pedal

the

gearing

connection

between

the

spring

same

and, in electromagnetic

and

conjunction

reduces

rotates

trimmer

cam and tension

is sufficient to bring roller 6

time, pedal 24

clutch. This clutch

the

machine

with

actuates

carbon

speedtothe

speed

level at which the trimming mechanism is not likely to be damaged. running at this reduced

speed

until the needle has reached the lowest

engaging

release

limit

brush

con

speed,

has been

point of its stroke and the left carbon brush in holder 17 contacts the left switch-off track on slip ring 16. This is the point at which the thread trimming action starts (Fig. 27). Cen trifugal switch 18 actuates pin 19 which, in turn, pushes interlocking latch 5 down so that it clears crank 20. This permits shaft 4. together with roller lever 9 and roller 6, to be moved

toward

knife

cam

2 by

the

slotofthe

At the

same

cam

(Fig. 28).

time,

cone21releases

actionofthe

released

pressure

spring,

causing

roller 6 to

engage

the needle thread tension and the right carbon brush in

holder 17 moves to the right switch-off track of synchronizer slip ring 16. while the motor keeps driving the machine at low speed. Then knife cam 2 imparts an oscillating motion

roller

lever

9 which is

transmittedtoshaft4.crank

10,

connection

10.1

and

thread

catcher

11. causing the latter to trim the threads. The machine stops now with the take-up lever at

its

highest

position.

As thread catcher 11 swings forward, its tip

enters

the needle thread loop so

that

the bobbin

thread and the left leg of the needle thread loop contact its left flank, while the right leg

the

needle

thread

loop

contacts

its right fiank.

The thread catcher ceases to swing forward when the two threads passing to the left of its

tip have entered the

is pulled

tautbyneedle

recess

back of heel 11.1 (Fig. 1) and the thread on its right-hand

thread

retaining

edge

11.2.

side

Fig. 1

As thread catcher t1 returns to its starting position, the threads caught in the

pulled back under knife 12. Both

thread

catcher

(Fig. 1) and

the tip of the thread catcher has reached cutting

When

the

threads

and

the right switch-off track of synchronizer siip ring 16

are

severed,

can now take her foot off the left pedal. If both are

permitted to return to their inoperative position simultaneously. It is advisable to let the

are

not

the

threads

sheared

take-up

are

protected in a groove on the

off until

lever

the

somewhat

edge

S 2 of the knife (Fig. 2).

has

reached

stops

pedals

were

depressed,

the

the machine. The

raised cutting

highest

make

recess

surface

edge

point of its

sure

are

of the S 1 at

stroke

operator

that both

right pedai return to its starting position slightly ahead of the left because the needle will

starttodescend

ordertoenable

again if the right

operators

to switch from forward to

treadle

is not returned to its starting position promptly.

backward

stitching by

foot

action

Pfaff machines 461-900. 463-900 and 465-900, an additional feed reversing mechanism has

been mounted on feed regulating shaft (Fig. 27). When the front end of pedal 26 is depressed,

connection 27

causes

trimmer engaging cam 30 to turn forward and this motion is transmitted

to feed reversing crank 33 by means of a two-part connection.

On Pfaff machines 467-900 and 469-900, the top or differential feed can be controlled by de pressing the front end of the left pedal. The reverse feed control of these machines must be

operated

by hand.

Maintenance

A careful adjustment of the trimming mechanism

ensures

trouble-free operation.

Ail screws must be tightened securely. This applies especially to the screws on knife cam 2, roller lever 9 and thread catcher driving crank 10 since these parts are subjected to abrupt

stress.

Special

especially between sewing hook and needle plate, are

care

should be taken that

the

dust

and lint which accumulate in this mechanism,

removed

with

a soft brush each day

the machine is in operation. By the same token, ail moving parts should be oiled daily.

When

oiling

all

moving

parts of the

trimming

mechanism each day, check to see that cen

trifugal switch 18, pin 19 and latch 5 move freely. Make particularly sure that synchronizer

slip ring 16 is

suretooil

kept

the

free

from oil.

somewhat

concealed

roller6on

roller

lever

Adjustment

It is

recommendedtouseagauge

catcher

No. 129 567,

which is available under No. 129 499. A

canbesupplied

for

In checking the various settings, be

Adjusting

the

Interlocking

needle

plate

compound-feed

suretoproceed

Latch

14 (Fig. 30) for

gauge

feed dog, which is identified by

machines.

in the

sequence

the

adjustmentofthe

indicated below:

thread

Raise the needle to its highest point and

cam

30 in

its

inoperative

Push trimmer engaging

your

thumb,

and

be a

clearanceofabout

crank

20 (Fig. 3). Adjustment is made by eccentric roller stud 31 which

trimmer

about

engaging

.04",or1.0

check

cam

mm,

position).

shaft

4 to the right by pressing

whether

interlocking latch 5 fits

.004", or 0.1 mm, between interlocking latch 5 and driving

30.

After

the

between

the

disengage

adjustment,

faceofeccentric

check to

the thread trimmer (trimmer engaging

slot in trimmer engaging cam 30 (Fig. 4).

Fig. 3 Fig. 4

against

carbon brush holder 17 with

over

crank20securely.

see

that

roller

stud31and

j©l

engages

there

There

in the slot of

is a

clearance

the

bottomofthe

should

Endwise

Set knife cam 2 on lower main shaft 3 so that there is a clearance of about .02", or 0.5

Adjustment

of Knife

Cam

mm,

between knife cam and bedplate (Fig. 5). After this adjustment, check to see that the slip

washer

contacts

the

knife

cam

hub.

O.Smm

Fig. 5

When the needle Is at its lowest point, the pointed lobe of knife cam 2 should point toward

the lower front

edgeofthe

bedplate (Fig. 6).

Fig. 6

a/ oT^

Adjusting

the

Roller

Lever

Raise the needle to its highest point and

cam

30 in its

inoperative

position).

Move roller lever 9 to the right on trimmer engaging ed inner

(Fig. 7). Bring

the

surface

needle

of knife cam 2, and mark this position on trimmer engaging

to its

lowest

position.

disengage

the thread trimmer (trimmer engaging

shaft

4 until roller 6

contacts

the

recess shaft

Engage roller lever 9 in the slot of knife cam 2 and rotate trimmer engaging cam 30 until

set

its stud contacts

above-mentioned mark

screw 29 of stop 28 (Fig. 28). Push roller lever 9 to the left until the

becomes

visible on trimmer engaging

shaft

4. Continue pushing until

roller lever 9 is positioned about 02", or 0.5 mm, beyond this mark. Pull out thread catcher driving crank 10 as far as it will go and hold it there. Push roller lever 9 against the outer

wall of

the

slot

in knife

cam2and

tighten

its

set

screws

securely.

Fig. 7 Fig. 8

4. Double-checking

Adjustments

1-3

Bring the needle to its lowest position. As you rotate trimmer engaging cam 30 in either

direction, the roller of roller lever 9 should fit into the slot of knife cam 2 easily, without

making

any

radial

movement.

Raise the needle to its highest point.

engaging

beaclearance

cam

30 until its

of .02",or0.5 mm,

stud

contacts

stop

between

Hold

interlocking latch 5 steady and turn trimmer

28. As you turn the

the

rolleronroller

balance

lever9and

wheel,

the

recessed

there

should

surface of knife cam 2 (Fig. 9).

Bring

the needle to its highest point and turn

position.

Insert

roller

lever

9 into

the

sharp

bend

trimmer

of the

engaging cam 30 to its inoperative

slot

of knife

cam

2 and check

whether

the roller lever returns to its starting position as you rotate the balance wheel. When at

this position, the roller should still be

(Fig. 10). Make sure the clearance between guide fork

about

.06", or 1.5 mm, inside the slot of knife cam 2

17.1

and carbon brush holder 17

does not exceed .004"—.008", or 0.1—0.2 mm (Fig. 29).

inner

Fig. 9

Fig. 10

]Sfnm

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