Singer 591UTT User manual

SINGER
591 UTT
Service
Manual
From the library of: Superior Sewing Machine & Supply LLC

CONTENTS
Page No.
Description 1
UnderbedThread Trimmer 2-15
Principal Parts 2-3
DriveSystem of Thread Trimmer 2
Pullingand TrimmingUnit 2
Tension Releaseand MovableSlack Thread Regulator 3
Descriptionof TrimmingOperation 3-6
Timing and Setting 6-15
Adjustment of NeedleStop Positions 6-8
Timing—Actuation of Trimmer Solenoid 8
Timing —Completion of Actuation of Trinuner Solenoid 8-9
Setting of Trimmer Solenoid 9
Setting of Stationary Knife 9
Setting of Thread Puller 9-10
Adjustment of Pressure of Thread Puller Against Stationary Knife 10-11
Timing and Setting of Thread Puller Action Cam 11-12
Timing of Tension Release Action Cam 12
Setting of Thread PuUerAction Cam AdjustingPlate 13
Adjustment of Gap Between Tension Discs 13-14
Timing of Tension Release 14
Adjusting the Length of Needle Thread End 14-15
Adjustment of Thread Wiper 15
Back Tack Device 16-21
Principal Parts 16-17
Description of BackTacking Operation 18
Setting and Adjustment
of BackTack Device 18-21
Setting of Back Tack Solenoid 18
Setting of Feed Rock Shaft DrivingFrame 19
Setting
of Feed Rock Shaft DrivingFrame Action Shaft and Collar 19
Setting of Feed Rock Shaft DrivingFrame Action Lever 19-20
Feed Rock Shaft DrivingFrame Spring Tension 20
Setting of Feed Rock Shaft Driving Frame Stopper Spring 20
Setting of Push Button Switch 20
Adjustment of Push Button SpringTension 21
Cords and Connections 21
* A Trademark of THE SINGER COMPANY
Copyright© 1981 THE SINGER COMPANY
All Rights Reserved Throughout the World
From the library of: Superior Sewing Machine & Supply LLC

DESCRIPTION
An electro-mechanical underbed thread trimming unit, which is an integral part of the machine, is incorporated in the "B"
variety machines.
The machine is driven by a needle positioner motor, and its sensor and controlbox relay the electronic commands to the
built-in solenoids of the machine.
The needle and bobbin threads are trimmed below the throat plate after the sewing operation.
A threadwiper "Wipes" the needle thread to proper positionfor startingthe next sewing operation.
In addition to the under bed thread trimming unit, a back tackingsystem is incorporatedin the "G"
variety machines. The
automatic back tack switch and control box relay the electronic commandsto the built-insolenoidfor automatic back tacking
at start and at end of stitching. The push button switch provided adjacentto the needle barpermitsback tacking in the midst
of the sewing operation.
This manual should be used in connection with the Service Manual Form U3208 for the regular 591 machine. It informs
especially regarding the operation and maintenance of the underbed thread trimmer and back tacking device and their drive
systems.
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UNDERBED THREAD TRIMMER
PRINCIPAL PARTS
Drive System of Thread Trimmer
THREAD PULLER ACTION LEVER LINK
THREAD PULLER ACTION LEVER
THREAD PULLER
THREAD PULLER ACTION CAM ADJUSTING PLATE
TENSION RELEASE ACTION PLATE
STATIONARY
KNIFE
/WVW/
ROTATING
HOOK SHAFT
THREAD PULLER BRACKET
THREAD PULLER ACTION
CAM FOLLOWER
TENSION RELEASE ACTION CAM
THREAD
PULLER
ACTION
CAM
THREAD PULLER ACTION PLATE
Fig. 1
Pulling and
Trimming Unit
STATIONARY KNIFE
Fig. 2
THREAD PULLER
TENSION RELEASING WIRE
TRIMMER SOLENOID
THREAD PULLER ADJUSTING BLOCK
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Tension Release and Movable Slack Thread Regulator
SLACK THREAD REGULATOR
ACTION PLATE
MOVABLE SLACK
THREAD REGULATOR
Fig. 3
DESCRIPTION OF THE TRIMMING OPERATION
1. When the foot treadle is returned to its neutral position
upon completion of the sewing cycle, the machine
stops approximately Smm (.118") beyond the bottom
dead center of the needle (Fig. 5, hook point in the
loop of needle thread) when the sensor plate A (red)
reaches a point shown in Fig. 6.
2. Heeling the foot treadle will start the machine to run
at the trimming speed (200 r.p.m).
SENSOR PLATE A
TENSION RELEASING
CAM
TENSION RELEASING WIRE
Fig. 4
Fig. 5
Fig. 6
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The trimmer solenoid is energized when the sensor
plate B (yellow) reaches a point shown in Fig, 7.
SENSOR PLATE B
Fig. 7
When the cam follower on the thread puller action plate slips into the recessed portion of the thread puller action cam
adjustingplate, the thread puller is activated to move through the loop (Fig. 8) to a point shown in solid line in Fig.9,
and the needle and bobbin threads are positioned as shown also in Fig. 9. Simultaneously, the thread puller action plate
pushes the tension release action plate making its pin ride on the tension release action cam. Immediately when the pin
rides on the tension release action cam,the electroniccommandrelayedfrom the sensorplate C (yellow,Fig. 10) cuts off
the current supply to the trimmersolenoid. The above motion makes the tension releasing camrotate untiljust beforethe
tension discs are released.
Fig. 8
NEEDLE
THREAD
BOBBIN
THREAD
©
Fig. 9
n
SENSOR PLATE C
Fig. 10
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5. As the needle thread is cast off the rotating hook, it
catches on the hook portion of the thread puller.
(Fig. 11)
6. The tension release action plate pin reaches the inclina
tion on the tension release action cam and starts re
leasing the tension discs immediately after the needle
thread catches on
the thread puller.
Fig. 11
7. While the above takes place,the camfolloweron the thread pulleraction plate reachesthe inclinationon the thread puller
action camand the thread puller beginsto pull the bobbin and needlethreads toward the stationary knife.
8. The bobbin and needle threads are severed when the
cutting edge of the thread puller closes in against the
cutting edge of the stationary knife. (Fig. 12 and 13)
9. When the threads are trimmed, the spring biased
tension release action plate moves back to its rest
position disengaging its pin from the tension release
action cam and thus completesits function of releasing
and holding the needle thread tension open.
10. The trimmer and tension releasing mechanisms return
to their rest positions upon completion of the
trimming operation and the machine stopsin the upper
needle position. When the sensor plate D (yellow)
reaches a point shown in Fig. 14.
200 type - Approximately 1mm (.039") before take-
up leverreachesits upper dead center.
300 type — Take-up leverat its upper deadcenter.
SENSOR PLATE D
Fig. 14
CUTTING EDGE OF
THREAD PULLER
Fig. 12
CUTTING EDGE OF
STATIONARY KNIFE
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11. Upon completion of the trimming operation, the
thread wiper makes a swivelling movement to place
the needle thread in proper position for starting the
next sewing operation.
TIMING AND SETTING
When checking the operation of the trimmermechanism by manual actuation of the mechanisms.
a. Be sure to tum machine pulley over toward front of machine.
b. Push thread pulleraction plate toward cam when take-upleveris almost at its lower dead center.
NOTE: The thread puller may strike the needle and damage itself and the needle unless the thread puller action plate it
pushed toward the cam as described above since the rotatinghook shaft makes two revolutions against onecycle
of the needle bar.
Be sure to check that the machine is correctly adjusted before making adjustments to the trimmer mechanism. (Refer to
ServiceManual Form U3208 for regular 591 machine).
Check and adjust the trimmer mechanism in the order instructed in this manual since it is interlocked with many other area.
Adjustment of Needle Stop Position
When checking and making adjustments of needle stop positions, be sure to disconnect the trimmer and wiper connectors
from the control box.
Needle Stop Positions
a. Lower Needle Position
The lower needle position is approximately 3mm (.118") beyond the bottom dead center ofthe needle. This 1st position
does not call for absolute accuracy and minor adjustments may be made ifthe threads cannot be properly trimmed dueto
skip stitching.
b. Upper NeedlePosition
The upper needle position of the 200 type machine is approximately 1mm (.039") before the take-up lever reaches its
upper dead centerand the upper needle position of the 300 type machine is when the take-up lever is at itsupper dead
center.
Adjust upper needle positionas accurately as possible by running andstopping machine several times to checkfor correct
position.
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Adjustments
AH sensors are correctly timed andset before leaving the factory. If, however, this timing or setting has been disturbed and
retiming or resetting becomes necessary, adjust bycorrectly positioning the sensor plates.
1. The positions of the sensor plates (for upper and lower needle positions and for controlling the trimmer solenoid) in
relation to the sensor set screw should be as shown in Fig. 15. To adjust the position of a sensor plate, loosen screw on
end of the sensorandturn sensor plateasrequired,then tightenthe screw.
SENSOR PLATE C —
(TRIM. SOLENOID "OFF")
SENSOR SET SCREW
Fig. 15
39'
SENSOR SET SCREW
SENSOR PLATE D
(UPPER NEEDLE POS.)
149'
SENSOR PLATE A
(LOWER NEEDLE POS)
SENSOR PLATE B
(TRIM.SOLENOID "ON")
Position sensor on hub of machine pulley so that its second set screw (set screw which appears immediately after the first
set screw when sensor is rotated over toward the operator) is alignedwith the second set screw of the machine pulley and
firmly tighten the two set screws. (See Fig. 16)
ALIGN SET SCREW
MACHINE PULLEY
MACHINE PULLEY SET SCREW
SENSOR SET SCREW
Fig. 16
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3. Use sensor retainer supplied withthe machine andbe sure it is correctly secured in position.
Note: The sensor plate for upper needle position should not be reset inorderto solve the problem of tension releasing
mechanism not being released when needle stopsin the upper needle position.
Thisadjustment
should bemadeby resetting the sensorunit on the hub of machine pulley asinstructed below.
a. Loosen the two set screws holding the sensor unit and while holding the sensorwithonehand,turn machine pulley
slightly over toward the front of machine.
b. Hold sensorin this position and temporarily tighten the first screw.
c. Run machine and checkwhether the tension releasing mechanism is released when the needle stops in the upper
position. Repeat above, if necessary.
d. Firmly tighten both first and second set screws.
Timing — Actuation of Trimmer Solenoid
The trimmer solenoid is actuated when the take-up lever reaches a point lOmm (.394") before its lower dead center. The
timing of this actuationis controlled by the sensor plateBin the sensor unit. (Referto item3 underDescription of Trimming
Operation).
Timing — Completion of Actuation of Trimmer Solenoid
The current supply to the trimmersolenoid is cut off completing its actuation when the tension release action plate pinis in
the
range fi shown in Fig. 17.Thistimingis controlledby the sensorplate Candwhenadjustmentisnecessary, reset thissensor
plate.
Turn machine pulley until the clearance between tension release action plate pin and tension release action cam is approxi
mately 1mm(.039") (Fig. 17) and whileholdingthe machinepulley in this position, set sensorplate C asshownin Fig. 18.
TENSION RELEASE ACTION CAM
TENSION RELEASE ACTION
PLATE PIN
APPROX. 1.0 mm
Fig. 17
Fig.
18
SENSOR PLATE C
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