Jute Weaving Shuttle less

Comments

Transcription

Jute Weaving Shuttle less
TRAINING MANUAL FOR
JUTE INDUSTRY
.
Part B-3/2: Jute Weaving (Shuttle-less)
,
AUTHORS
Swapan Kumar Ghosh, Dibyendu Mukherjee and
Sambhu Bhattacharya
Compiled &Edited by:
Swapan Kumar Ghosh &Ashis Kumar Samanta
Sponsored by Ministry of Textiles, Government of India
Under Integrated Skill Development Scheme (I.S.D.S)
for Jute Mill Workers and Supervisors Skill Development
under Human Resource Development Programme.
2011-2017
Implementing Agency
DEPARTMENT OF JUTE &FIBRE TECHNOLOGY
INSTITUTE OF JUTE TECHNOLOGY
University of Calcutta
35, Ballygunge Circular Road
Kolkata-700019, West Bengal
Website: www.caluniv.ac.in, www.ijtindia.org
E-mail: [email protected]
Telephone: (033) 2461 5477/5632/5326/5444
Tele fax: (033) 2461 5632
1
2
JUTE SHUTTLE-LESS WEAVING (S4)
Objective
The objective of Weaving is to produce fabric with minimum defects by interlacement of warp and
weft. For the purpose, warp coming from the beam is divided into two layers and weft (cop) is
passed through the opening of the two layers of warp by' means of shuttle.
Motions in Loom
For continuous weaving (interlacement of warp and weft) with minimum defects, the
motionsneeded in a shuttle loom are -
Primary Motion

Shedding: It is dividing of warp into two layers by means of Tappet/wyper or dobby or jacquard.
Tappet or wyper is commonly used for weaving Hessian and Sacking fabric and jacquard is used
for producing carpet. Dobby which is not popular in jute industry may be used for producing
diversified/decorative jute fabrics. The dividing of warp into two layers shall be done according
to the design/structure of the fabric to be produced.

Picking: Picking is the passing of the shuttle from one side/box of the loom to the other side/box
with the weft/cop inside it's cavity through the warp shed. Generally, over pick mechanism is
used in jute looms for picking purpose.

Beating: Beating motion places the last pick to the fell of the cloth by means of reed fitted on
the sley and such motion is derived from the crank shaft by means of crank and crank arm.
Secondary Motions

Let-off: Let-off motion delivers the required length of warp for weaving from the weavers beam
and maintains required warp tension. It is negative and intermittent in nature and the beam is
turned when warp tension becomes more than the beam braking force.

Take-up: Take-up motion withdraws the cloth from the weaving area at a constant rate that will
give the required picks/inch and then winds the cloth on the cloth roller in every loom cycle. It is
positive and intermittent and popularly known as three wheel or five wheel take-up motion.
Auxiliary Motions

Warp protector motion (Fast reed type):To protect the warp from breakage by stopping the
loom when shuttle is trapped inside the shed or fail to reach the other shuttle box.
Auto cop change or Automatic Cop loading:To load the shuttle with a new cop when earlier cop is
emptied in running condition of the loom. It improves the efficiency of the loom and mainly used in
sacking loom.
3
What is Shuttleless Weaving?
As discussed earlier, jute cloths are still woven mostly on the age-old non-automatic over pick
shuttle looms. This results in low productivity and high labour complement at weaving. Moreover,
much improved qualities of cloths can hardly be expected from these looms. Constant efforts are
therefore, being made to produce the cloths at faster rates and thereby, to achieve higher weaving
productivity at reduced cost of production by adopting the various methods where the conventional
method of weft insertion by shuttle is no longer used. These non-conventional methods of weaving,
are known as shuttleless weaving and such looms are called the shuttleless looms or shuttleless
weaving machines.
What is the Problem with Shuttle?
The productivity of a loom can be increased by increasing its speed that is, picks/minute. Weight of a
shuttle with cop is about 1.5 kg. Increasing the loom speed means increasing the number of traverse
of this heavy mass, the shuttle, in a minute, which in other words indicates increasing the forces
needed for picking and checking of the shuttle in addition to considerable increase in power for
picking. This increase in forces will cause severe wear and tear of the picking and checking
mechanisms of the loom and ultimately failure of the mechanisms unless substantial mechanical and
design modifications of the loom are made which again may not be cost effective.
To solve these problems the SHUTTLELESS LOOMS have been developed.
4
Weft Insertion Systems in Shuttleless Looms
Projectile loom - a number of projectiles is employed to insert thepicks. The projectile is a thin and
light metal piece with 90 mmlength, 14 mm width and 6 mm thickness and weighs about 40g.
It grips the tip of weft at its rear end and traverses through thewarp shed to insert the pick. In the
projectile loom the projectiletraverses from left to right to pick the weft.
In projectile picking system more than one type of weft can be used
Rapier loom - rigid rods or flexible tapes fitted with gripperat the ends hold the weft and traverse
through the warp shedto insert the pick. The former called the rigid rapier and thelatter the flexible
rapier.
Again two systems of weft insertion by rapier – Tip Transfer and Loop Insertion – are adopted for
jute weaving. In the former, one of the two rapiers grips the weft by the tip and transfers it to the
other rapier in the middle of the warp shed to insert the pick. In the other system, one rapier is used
and it does not grip the weft but pushes it in the form of a loop. Loop insertion system isadopted for
weaving sacking cloth.
In the tip transfer system more than one type of weft can beused
In the loop insertion system only one type of weft can be used
5
Pneumatic loom – The only pneumatic loom (where weft is inserted by air) employed for jute
weaving is the Pneumatic Rapier Loom. In this, the pick of weft is inserted by continuous blowing of
air through a hollow pipe from thepicking side and continuous sucking of air through anotherhollow
pipe from the other side. Two pipes meet at the middleof the warp shed and the pick of weft is
transferred from onepipe to the other under the air current.
Here only one type of weft can be used.
Comparison of Rapier Head and Projectile with Shuttles
6
Why are Improved Qualities of Yarn Needed for Shuttleless Looms?
 Depth of warp shed required in a shuttleless loom is much smaller than that required in a shuttle
loom. The warps in the shuttleless looms are however, woven under comparatively higher tension in
order to ensuring clear warp shed. As a result, while the smaller shed depth imposes less strain on
the warps, higher warp tension demands stronger yarns.
 In regard to the weft, the shuttle merely lays the weft in the warp shed and there is no axial
movement of the weft during insertion. The projectile, rapier or air on the contrary, drags the weft,
which therefore, travels at fairly high velocity during insertion. For these reasons improved qualities
of warp and weft yarns along with properly prepared warp beams and weft packages are essential
for satisfactory performance of the shuttleless looms.
Common Features of Shuttleless Looms
 In all these systems the weft is inserted from one side of the cloth from a cross wound cone,
placed at a suitable position outside the warp shed. Weft yarn is usually inserted as a single pick, but
in some special cases with the rapiers, a double pick is inserted in each warp shed.
 Since the weft insertion element in any shuttleless loom does not carry the weft package and
usually single or in some cases double pick is inserted in each warp shed, a separate selvedge
forming device is needed on both or at least on one side of the cloth.
 Since no cop is used in the shuttleless looms the entire cop winding process is dispensed with.
This results in enormous savings in the production cost and working space.
Another important aspect of the shuttleless loom is thereduction in noise level. Noise levels of the
shuttleless looms are, in general 85 – 100dB(A) which are much below that of shuttle loom which
ranges between 92 – 107 dB(A) and they therefore, provide a more friendly working environment
to the workers.
It is customary that the sley remains stationary during picking so that the element with the help of
which the weftis inserted can traverse through the warp shed undisturbed.
Hence, the sleys in most of the shuttless looms are driven by cams and not by cranks like in shuttle
looms.
Does Shuttleless Picking Need Changes in Other Loom Mechanisms?
Replacement of the shuttle by other means for inserting the weft does not cause any change in
the fundamental sequence of loom operation –shedding, picking and beating up.
Because of the changes in the mechanism used for picking there may be consequential changes in
shedding and beating up but many of the other loom mechanisms need not differ from those
employed in shuttle loom.
Since shuttle is not used in the shuttleless loom for inserting the weft,smaller depth of warp shed
with consequently smaller sweep of sley can be arranged and hence, mass of the sley and the
distance through which the sley reciprocates can be reduced considerably.
Picking by projectile, air and in some cases, rapier compels the sley toremain stationary during the
insertion of weft and the sley is therefore,driven by matched cams with dwells.
7
In regard to the other loom mechanisms the shuttleless loom makers take the opportunity in
making improvements in the design of these devices which are made to operate positively and more
precisely.
Positive Shedding Mechanism
 In positive shedding the heald shafts are both raised and lowered by thegrooved or matched
shedding cams.
 In case of grooved cam a frictionless roller or cam follower attached to a lever connected to the
heald shaft moves inside the groove machined in the face of the cam and each cam thus moves the
heald shaft both upward and downward.
 In case of matched cams, which are more popular, a pair of matched cams is used for each heald
shaft. The frictionless followers, one for each cam, are carried by a lever and always stay in contact
with the cams. During the rotation of the cams the followers oscillate the lever about its fulcrum and
transmit the reciprocating movements to the respective heald shaft.
PROJECTILE LOOM
Projectile looms of two manufacturers, Sulzer of Switzerland and Textilmash(STB Loom) of Russia are
used in weaving jute fabrics. The principles of weft insertion and other operations are identical in
both the makes.
8
Projectile Picking System
In this type of weaving machine, picking is executed by torsion bar. The mechanism is situated at the
left hand side of the loom. The picking cam fitted on the picking shaft rotates once every pick and
gradually displaces the toggle lever about its pivot. The toggle lever is fastened at one end of the
torsion bar and at the other end the bar is fixed on the loom frame. The rotation of the picking cam
twists the torsion bar and strain energy is developed in it. During picking the energy is suddenly
released and the projectile is picked at a high velocity of about 24 m/sec.
1 Torsion Bar
2 Splined End
3 Picking arm
4 Picking shoe
5 Projectile
6 Projectile Spring Opener
7 Side Shaft
8 Picking Shaft
9 Toggle Plate
10 Toggle Plate Centre
11 Pivoted lever
12 Picking Cam
13 Toggle
14 Roller on Picking Cam
15 Hydraulic Brake (body)
16 Hydraulic Brake (plunger)
9
PROJECTILE LOOM
10
Projectile Guide
The projectile is much lighter and traverses at much higher velocity than shuttle. As a result, the
projectile may be easily deflected from its path by the slightest obstruction on its passage. To avoid
such possibility the projectiles are propelled through a series of thin metal guides called the
projectile guides, mounted on the sley. The guides are spaced at intervals with their axial planes in
the warp direction and the warp is not touched by the projectile or the weft. During entire period of
weft insertion the sley remains stationary at back centre.
 The projectile grips the weft with the help of spring loaded grippers at its rear end and traverses
through the guides. As the projectile passes through the guides it lays the weft inside the guides.
When the sley moves forward to beat up the weft slips out of each guide through its aperture facing
the reed and is beaten to the fell of the cloth.
11
12
Projectile
Feeder
Weft Insertion Sequence by Projectile
13
14
Sometimes more than one cloth is woven side by side on the wide looms. The wefts floating
between the successive cloths are then cut and the free ends are tucked in at the selvedges by the
tucking devices placed between the cloths at suitable intervals across the width of the loom. The
loom is equipped with weft patterning system for weaving weft way stripes with two or more
different qualities or colours of weft. In this, separate weft package, tensioner, compensator and
feeder are used for each type of weft, but the principle of weft insertion is the same.
Like shuttle the projectile is basically a missile and so it needs checking at the completion of weft
insertion as well as the warp protector mechanism. The projectile loom is the only shuttleless loom
provided with warp protector mechanism. The checking and protector mechanisms are located at
the right hand side of the loom, while picking takes place from left hand side of the loom.
Timing Diagram of Projectile Loom
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29