KCG COLLEGE OF TECHNOLOGY FASHION TECHNOLOGY – FOURTH SEMESTER

UNIT - II
Shuttle Looms, Dobby and Jacquard
(18 Hours)

 Basic concepts of looms

 Types of Looms – handloom – power loom – Automatic looms
 Primary motions of a loom
 Primary motions of Tappet looms
 Secondary motions of Tappet looms
 Auxiliary motions of Tappet looms
 Basic Principles of Drop box Looms
 Basic Principles of Dobby looms
 Basic Principles of Jacquard looms
 Basic Principles of Card cutting

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2.1 . Basic Concepts of Woven Fabric and Loom

Learning Objectives

In this lesson, you learn about the Classification of Fabric, Definition of Terminologies
related to Woven fabric, Path of Warp in loom, Handloom parts and its function .

Classification of Fabric:
Woven Fabric:
Woven fabric consists of longitudinal warp threads (Ends) and traverse weft threads (Picks) interlaced in
definite order. Examples for few woven fabrics are Shirting fabric, Suiting fabrics. Woven fabrics are
produced using the machine called Loom.

Woven fabric

Knitted Fabric:
Knitted fabric is produced by making loops of yarn and interlocking loops with each other. Examples for
few knitted fabrics are T-shirts and leggings. Knitted fabrics are produced using Knitting machine.

Knitted fabric

Non-Woven Fabric:
Nonwoven fabrics are broadly defined as sheet or web structures bonded together by entangling fiber or
filaments (and by perforating films) mechanically, thermally, or chemically.

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Non-woven Fabric (Non – knitted fabric)

Woven Fabric:
Woven fabrics are produced by the process of ‘Weaving’ in which two distinct sets of yarns are interlaced
at right angles to each other.
The lengthwise yarns are called the ‘Warp’.
The widthwise yarns are called the ‘Weft’.
The individual thread of Warp is called ‘End’.
The individual thread of Weft is called ‘Pick’.
The length wise running edges of woven fabric are known as ‘Selvedges’. The definite order in which the
warp and weft interlaces is called ‘Weave’.
The machine in which the weaving process carried is called ‘Loom’.
Pick

End Down (Pick up) End up (Pick down)

End
Weft

Selvedge
Warp
Elements of woven fabric
The interlacement is of two kinds. 1. End lifted up over the Pick and 2. End lowered down the Pick.
End
End lifted up over the Pick End lowered down the Pick

Pick
Two kinds of interlacement

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2.2. Loom and Types of Loom

Learning Objectives
In this lesson, you learn about the path of warp in loom, different parts and its functions of loom
classification of loom, power loom, automatic looms, shuttle less looms and special type of looms

Path of Warp in loom:

1. Warp Beam 2. Back rest 3. Warp Sheet 4. Lease Rods

5. Healds 6. Reed 7. Shuttle 8. Weft
9. Cloth 10. Front Rest 11. Cloth Beam 12. Treadle
13. Sley
Path of Warp in Loom

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Warp beam (1) ---> Back rest (2) ---> Leas rods (4) ---> Healds (5) ---> Reed (6) ---> Front Rest (10) --->
Cloth Beam (11)
 From the warp beam (1), passing over the back rest (2), the warp (3) starts its journey.
 Then passes into a pair of lease rods (4) to maintain lease in between warp threads.
 The ends are drawn through healds (5) wires as per drafting order (drawing).
 Then all the ends taken through the dents of the reed (6) as per the denting order.
 The warp sheet is divided into two layers with the help of healds and Treadles (12).
 The shuttle (7) carrying the weft (8) get interlaced with warp.
 The cloth (9) is formed by taking the weft near to the previous weft with the help of reed fixed in
the sley (13).
 The woven cloth is passed on to front rest (10) and then wound to cloth beam (11).

Handloom parts and its function:

Weaver’s Beam (or) Warp Beam:
• It is cylindrical wooden (or) metal beam with a pair of flanges mounted on it.
• It is also provided with ratchet wheel and pawl. The warp is wound on the warp beam.
• The wooden flanges help to maintain the width of the warp and avoid slippage of warp yarn at
the edges, there by facilitating to wind longer length of warp.
• The length of warp wound on a warp beam depends upon the count of warp yarn, type of loom,
production capacity and quality of fabric produced.

Back Rest:
• It is a cylindrical wooden (or) metal bar (or) roller placed above the warp beam.
• It guides the warp threads to sley through lease rods.
• It constantly maintains the level of the warp in co – ordination with the front rest.
• Hence longer length of warp can be wound on to the warp beam.
• Level of back rest is raised to insert more picks and to get better cover of fabric.

Lease Rod:
• Two rods used in warp sheet in between back rest and healds are called as lease rods.
• The Individual warp threads are alternatively passes up and down the lease rods, there by divide
the ends individually in the order of odd and even alternatively.
• 2 or 3 or 4 rods are used according to the requirement. It is bamboo stick or Aluminum pipe.
• It helps to locate the broken end and their respective position for mending correctly.

Healds:
• Heald are used to draw the ends through them as per the drafting order.
• The healds are knitted or mounted on heald frames for producing shedding.
• Types of helad are: Single clasped heald (used in primitive looms), Double clasped heald (used for
finer count yarn), Varnished heald (used for medium count yarn).
• The heald wires are mounted on a pair of rods and attached to the Heald frame.
• In the middle of each Heald wire, there is a heald eye, through which the ends are drawn.
• Heald shafts are known by other names such as staves and heddles etc.
• Healds keeps the warp thread as per the drafting order. It helps to form the design/weave.
• It helps to form shedding according to the peg – plan.

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Reed:
• It is a comb made of wires and the open space between the wires is termed as ‘dent’.
• The ends after it is drawn through the healds are again taken through the dent of the reed.
• It keeps the warp threads in respective positions and keeps it in required width.
• It decides the Ends per inch which can be changed by using different reed count of reed and
denting order.
• By moving the reed towards front rest, beats the last pick of weft to the cloth.
• Bamboo and steel reed are available.

Front Rest:
• It is a cylindrical wooden roller (or) metal bar (or) squared beam placed in front of the loom in co-
ordination with back rest to maintain the level of warp.
• In pit looms, it also used to wind the smaller length of cloth woven and act as cloth roller.
• In frame loom, it guides the cloth on to the cloth roller.

Cloth Beam:
• It is a cylindrical wooden roller (or) metal pipe, fit in front of the loom just below the front rest in
frame looms.
• The cloth is wound on it after weaving.
• It is also provided with ratchet wheel, pawl take – up arrangement or any other take up
mechanism enabling winding the cloth.

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Classification of Loom:

Loom

Hand Power
Loom Loom

Automatic Shuttle
Primitive Pit Frame Ordinary Special
less

Primitive Loom:
Primitive or Loin Loom are being used in the North Eastern States of our Country. Loin looms are very
simple in its structure. Loin loom is the first domestic loom. The main parts of a loin loom are its warp
roller and cloth roller. The warp is held spread on a light weight roller and is tied on a pillar or on a heavy
object in the house. The opposite side roller is attached with a belt which is wrapped around the waist of
the weaver at sitting poster extending the leg in the ground. This loom is having the minimum shedding
and picking devises. With the help of these devises the weaver, mostly women, work on this loom. The
length and width of warp used to be very less. Every house has a loom and weaves at least for their
domestic requirements.

Pit loom:
Digging a small pit in the ground to a depth of say about 3 feet to accommodate the treadles is the
specialty of this loom. Loom frame structure is built around the pit. Hence, once the Pit loom structure is
fixed around the pit, it is not possible to move. Using this loom, fine varieties of fabrics like Sarees, Dhoties
and also coarser varieties of fabrics like Durries and Blankets could be woven because of rigidity of frames
fixed in the floor.

Frame loom:
Instead of fixing it in the floor, the entire structure of the frames of the loom is made with wooden frame,
interconnected and made as structure of framed box of movable. Frame looms are more suitable for
weaving medium and coarser varieties of fabrics.
The height of roof required for pit loom is less than the height of roof required for frame loom loom. The
pit loom, once set up, cannot be moved to other place. But, the frame looms can be moved from one
place to another place within the shed.

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Ordinary Power Loom:

A power loom is a mechanized loom, and was one of the key developments in the industrialization of
weaving during the early Industrial Revolution. In Power loom, all the mechanisms of weaving viz.
shedding, picking and take – up are get operated by a motor and synchronized with each other. The
operator of the loom, has to look after whether all the motions of weaving are systematically carried or
not. In ordinary power loom, when the end in the warp sheet breaks, the pick of weft in the shuttle break
or exhaust and the shuttle get trapped in the middle of shed, the operator has to notice the occurring of
these faults and stop the motions of weaving on his own.

Automatic Power Loom:

In automatic power loom, all the primary and secondary motions of weaving are performed by running
the motor. Apart from this, additional auxiliary motions are also set –up to stop the running of loom when
the end in the warp sheet breaks, the pick of weft in the shuttle break or exhaust and the shuttle get
trapped in the middle of shed.

Shuttle less Loom:

In handloom, ordinary power loom and automatic power loom, the weft wound in the pirn is carried
through the shuttle across the shed formed. The shuttle is big and heavy. The speed of loom is low and
noisy. The pirn contains small amount of weft and must be replaced often for continuous operation. In
shuttle less loom, instead of shuttle a small gripper or rapier belt or air jet or water jet is used for inserting
the weft. The weft is supplied from the cone placing at the side of loom. Because of this the speed of loom
is increased.

Special Looms:
Box loom:
A loom having two or more shuttles used for weaving fabrics containing weft yarns different as to size,
twist or color.

Magazine loom:
This is the type of automatic loom in which the loom takes the empty bobbin from the shuttle and
automatically replaces it with a new, full bobbin into the same shuttle. This exchange is made without
stopping the loom. In this case, the weaver is restricted to one shuttle and one color warp yarn (called
battery type). Another new type can use four colors in the warp.

Ribbon loom:
This is the type of loom used for making narrow fabrics.

Swivel loom:
This is the type of loom meant for narrow fabric such as ribbons and tapes, the picking is done by a special
type of small shuttle controlled by a swivel.

Circular Looms:
These looms are particularly used for making tubular fabrics rather than flat fabrics. A shuttle device in it
circulates the weft in a shed formed around the machine. A circular loom is primarily used for bagging
material.

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Multiphase loom:
The multiphase loom can form many different sheds at different places, thereby enabling insertion of a
number of filling yarns, one behind the other.

Needle loom:
This is the type of shuttleless weaving machine in which the weft is drawn from a stationary supply and
introduced into the shed in the form of a double-pick by a weft inserter needle. The weft is retained at
the opposite selvedge by the action of knitting or by the introduction of a locking thread from a separate
supply.

Pitloom

Primitive Loom

Frameloom

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Ordinary Power loom Automatic power loom

Shuttle less looms

Circular loom Multi phase weaving

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2.3. Motions of Loom

Learning Objectives
In this lesson, you learn about the motions of weaving; Primary mechanism – Shedding,
Picking, Beating; Secondary mechanism – Let-off and Take-up; Auxiliary motion –
Temple, Stop motions

Mechanism / Motions of Weaving:

Loom:
Loom is a Machine / Equipment used to interlace warp and weft threads in a definite order. The process
of interlacing is called weaving. The order in which the warp and weft threads are interlaced is called
weave. The weaving process involves different motions performed in sequential order.

Motions of
Weaving

Primary Secondary Auxiliary

Shedding Picking Beating Let - off Take - up Stop

Temple
Motions

Primary motions:
Shedding:
Shedding is the motion of separating the warp sheet into two layers one above the other called shed, so
that pick of weft can be inserted in between the two layers. Heald and Treadle are used for forming the
shed of ends for plain weaving.

Picking:
Picking is the motion of inserting /propelling the weft in between the shed formed, from one selvedge to
another selvedge, so that it can be beaten to the previous pick. Shuttle with Weft Pirn is used for picking
the weft.

Beating:
Beating is the motion of taking the pick of weft nearer to the pick already woven called Fell of cloth. Reed
and Sley are used for beating the pick.

Weaving and Loom:

Weaving is the process of performing these three motions in the order of Shedding, Picking and Beating
one after the other by keeping the warp sheet in tension, using the machine called Loom. By weaving, the
length of fabric gets produced in between the gap of cloth roller / front rest and the reed.

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Secondary motions:
Let – off and Take – up:
After weaving certain length of cloth, the gap between the cloth roller / front rest and reed get reduced.
To have the new gap, the warp kept under tension is loosened and the cloth length woven is taken up in
the cloth roller so that new gap is formed. This process of letting off the warp loose and talking up cloth
is called Let- off and Take-up. After doing let – off and take –up, again the warp is kept under tension to
continue the process of weaving.

Primary and Secondary Motions of Weaving

Shedding performed by using Healds and Treadles

Picking by right hand, Shuttle passing

through the shed, Beating by left hand Poker Rod Take - up

Primary and Secondary Motions of Weaving

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Hand Loom and Power Loom:

In the loom, if the motions of weaving is carried by Human Power using hands and legs, it is classified as
Hand Loom or Foot Loom. The man weaving the fabric is called ‘Weaver’.
In the loom, if all the motions of weaving is carried by Motor Power, it is classified as Power Loom. The
man has to look after whether all the motions of weaving in the Power Loom are systematically carried or
not. He is called as ‘Operator’.

Pit - Hand Loom Ordinary Power Loom

Auxiliary motions:
Temple motion in Loom:
While weaving, the width of cloth shrinks than the width of warp in reed. But it is necessary to keep the
width of cloth stretched equal to width of reed while weaving to avoid breaking of selvedge ends. For
stretching the cloth on the loom, a simple wooden frame is used across the width of cloth called ‘Temple’.
After 1/ 2 inches of cloth are woven, the temple is shifted / moved near to fell of cloth. This Moving /
Shifting of Temple is an Auxiliary motion of weaving.

Temple motion

Auxiliary motions in Automatic Power Loom:

While weaving, there may be chances of end in the warp sheet breaks, the pick of weft in the shuttle
break or exhaust and the shuttle get trapped in the middle of shed. In hand loom, the weaver has to notice
the occurring of these faults and stop the motions of weaving on his own. In automatic power loom, all
the motions of weaving are performed by running the motor. Hence, when the said faults occur, the motor
has to be stopped automatically by a mechanism / motion. The motions which stops the loom i) when the
end in the warp sheet breaks ii) the pick of weft in the shuttle break or exhaust and iii) the shuttle get
trapped in the middle of shed are called auxiliary motions in Power Loom.

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2.4 –Primary motions of Tappet Looms

Learning Objectives
In this lesson, you learn about the mechanism and working principle of Primary motions of Power
loom viz. Shedding, Picking and Beating

Path of warp yarn and cloth through loom

Motor and shaft connection

The loom pulley (machine pulley) gets motion directly from the motor pulley. The crank shaft, which has
a special design, is connected with the loom pulley. The revolution per minute (r.p.m.) of the crank shaft
is equal with the loom speed (number of picks inserted per minute or picks/minute). The beat up operati
on is done by the reed which is carried by the sley and the latter is connected with the crank shaft. One
revolution of crank shaft causes one beat up. Therefore, if 200 picks are being inserted per minute, 200
beat ups are required in one minute. Thus the r.p.m. of the crank shaft has to be 200.

Crank shaft is connected with the bottom shaft through gears. As the name implies, bottom shaft is
positioned near the floor. Picking motion is originated from the bottom shaft in case of shuttle looms.
Two picking cams are mounted on the bottom shaft, one on each side. Therefore, one revolution of
bottom shaft ensures the insertion of two picks. So, for inseting 200 picks per minute, bottom shaft should
rotate at 100 r.p.m. The r.p.m. of bottom shaft is always half as compared to that of crank shaft.

In case of plain weave, the healds return to the same position after every two picks. Therefore, two
shedding cams can be mounted on the bottom shaft for controlling the healds. However, for other weaves
where more than two healds are required, a cam shaft (also known as tappet shaft) is used. For example,

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in case of 3×1 twill weave, shedding cycle extends over 4 pick. In this case, 4 shedding cams are mounted
on cam shaft which rotates at 50 r.p.m. The primary motions, their frequency and controlling loom shaft
for plain weave and 3×1 twill weave are given in Tables.

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2.4.1 – Shedding Motion

Object of Shedding Mechanism
A shedding mechanism separates the warp threads into two layers or divisions to form a tunnel known
as “shed”. The shed provides room for passage of the shuttle. A shed may he formed by means of tappets,
cams, dobbies, jacquards etc.

Types of Tappet Shedding Mechanism

Generally there are two types of shedding:
1. Negative shedding
2. Positive shedding.
In plain looms, tappets are used to form sheds.

Negative Tappet Shedding

In a tappet shedding mechanism, if the tappet controls only one movement, either an upward or
downward movement of the heald shafts, then the shedding is known a “negative tappet shedding”. The
heald shafts are returned by some external device like springs, dead weights, rollers etc.

Positive Tappet Shedding

In a tappet shedding mechanism, if the tappet controls both upward and downward movements
of the heald shafts, then the shedding is known as positive tappet shedding.

Tappet Shedding Mechanism

Construction
Figure shows a negative tappet shedding mechanism. A pair of tappets A and B is fixed to the bottom shaft
C at 180 degrees to each other. Two treadle levers D and E are connected to the loom back-rail by a
bracket F. The bracket acts as a fulcrum for the levers. The two treadles have teeth to carry the lamb rods
G and H respectively. Two heald shafts J and K are connected to the lamb rods. A top reversing roller shaft
Q carries two rollers of different diameters. The roller of small diameter N is connected to leather strap L
to which the front heald shaft J is connected. The roller P of large diameter is connected to leather strap
M to which the back heald shaft K is connected. The tappets A and B touch the anti-friction bowls or
followers R and S respectively, which are fixed to the treadle levers.

The heald shafts have heald eyes T and U through which the war p threads pass X is the war p sheet and
Y is the cloth. The odd ends are passed through one heald shaft while the even ends are passed through
the other heald shaft.

Working Principle
When the bottom shaft is rotated in the clockwise direction as shown in the figure, the tappets are also
rotated. The tappet will depress the anti-friction bowl and the treadle. Since the treadles are fulcrum at
one end, the front portion of the treadle moves down. This action is transferred to the lamb rod, the heald
shaft and the leather strap. So one heald shaft is lowered and the threads connected to this heald shaft
are lowered and form the bottom layer of the shed.

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The leather straps attached to the reversing rollers are connected in opposite directions, i.e. when leather
strap is pulled down; it is unwound from its roller. The shaft therefore rotates in the clockwise direction
and the other leather strap is wound on to its roller. The heald shaft is raised and therefore the lamb rod
and treadle lever are also raised. The threads connected to the heald shaft are also raised and form the
top layer of the shed. For the next shed, the other tappet works with the other set of bowl, treadle, lamb
rod, heald shaft, strap and roller and the other heald shaft is lowered. The first heald shaft is raised by the
top reversing rollers, and the positions of the healds shafts are thus interchanged. Thus, for one rotation
of the bottom shaft, two sheds are formed. In this type of tappet shedding therefore, one tappet
depresses the concerned treadle and the corresponding heald shaft is lowered. But the other heald shaft
is raised by means of the top reversing rollers. So this type of shedding mechanism is known as “negative
tappet shedding mechanism”.

A and B –Tappets
C - Bottom shaft
D and E - Treadle levers
F – Fulcrum
G and H - Lamb rods
J and K - Heald shafts
L and M - Leather straps
N - Top reversing roller (Smaller dia)
P - Top reversing roller (Bigger dia)
Q - Reversing roller shaft
R and S – Bowls
T - Heald eye
U - Heald eye
V - Weft yarn
W - Lease rods
X - Warp sheet
Y – Cloth

Reversing Motions in Negative Tappet Shedding

Negative shedding requires external devices known as over and under motions to reverse the direction of
movement of the heald shafts. If the shedding tappets are placed under the heald shafts an over motion
is required. If the tappets are placed over the heald shafts then an under motion is required. In over
motion, bowls or pulleys are used. In under motion, springs or dead weights or elastic cords are used.
These motions are classified as single acting and compound acting types.

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Over Motions or Top Reversing Motions

Normally in negative tappet shedding motions, top reversing motions are used. The following types of top
reversing motion are used.
1. Roller reversing motions
2. Spring reversing motions.
Single and Compound Acting Types

Single acting type

In this type, each heald shaft is connected to a roller and spring arrangement. Therefore each heald shaft
is controlled separately.

Compound acting type

In this type, rollers connect the heald shafts, which work complementary to each other. The rollers will
not work independently of each other.
Examples
For two heald shafts
Figure shows the top-rollers arrangement for plain cloth using two heald shafts. Leather straps connected
to the heald shafts pass over rollers A and B. When the tappet lowers one heald shaft, the other is raised.
For three heald shaft
Figure shows the top-rollers arrangement for three heald shafts. The diameter of roller B must be twice
that of A; the diameter of C is immaterial. The reason for having the diameters of B and A in the ratio 2:1
is that when the first heald shaft is taken down, either the second or the third one must be taken up the
same distance.
Suppose the first heald shaft is taken down by a distance of 4”, the strap D will be taken up only by 2”.
This is due to roller A being half the size of B. The tappets are so constructed as to allow only one heald
shaft to go up for each pick. If this heald, shaft is the second one and the third is immovable, the second
will be taken up 4”or the same distance as the first was taken down. If the strap D is fastened to the heald
shaft, it would be taken up 8” instead of 4”. This arrangement of rollers is suitable for 2/1 twill or 1/2 twill
weaves.

2.4.2 – Picking Motion

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Object of Picking Mechanism

The object of picking is to insert the weft yarn through the warp shed during weaving.

Conventional Picking Mechanism or Negative Picking Mechanism

In this mechanism, a carrier known as shuttle carries the weft yarn in a package called the “pirn”.
Conventional Picking Mechanisms
The two main types of conventional picking mechanisms are:
I .Over pick mechanism - Cone over pick mechanism
2. Under pick mechanisms - a) Side-lever under pick mechanism
b) Side-shaft under pick mechanism
c) Cone under pick mechanism.

Cone Over pick Mechanism

If the fulcrum of the picking stick is above the level of the shuttle box, then the picking mechanism
is known as an under pick mechanism.
Construction
As shown in Figure the picking tappet A is fixed to the bottom shaft B. The picking tappet A consists of
three parts, the boss A1, shell A2 and nose A3. The boss is keyed on to the bottom shaft and it carries the
shell portion. The shell is provided with two slots A4 that can be adjusted concentrically on the bottom
shaft for changing the timing of the picking. The nose portion of the tappet is bolted to the shell; different
sizes of noses may be used. The picking nose bit A3 touches a tapered cone C, which is connected to a
vertical shaft D by a stud. The vertical shaft D is held in the vertical position by two brackets namely the
top bracket E and the foot step bearing F. these two brackets are adjusted on the loom frame in such a
way that the vertical shaft when rotated, will rotate freely and smoothly. The vertical shaft carries a collar
which has a leather strap H and spring I fixed to the loom side-frame by a hook.
The top of the vertical shaft carries two corrugated plates J and K. The bottom plate J is fixed rigidly. The
top plate K is placed upon the bottom plate such that its position can be altered to change the strength
of the pick. The picking arm or stick, made wood is fixed to the top plate by a grooved cup M and nut N.
A picking strap or picking band O, made of leather, is connected to the stick or arm by a pin P. The band
wound around the arm two to four coils spirally and then around the slot provided at the front end of the
picking arm. From here, the picking band passes down and is connected to a picker Q, which is loosely and
freely mounted on a spindle. The picker touches the tip of the shuttle R. A similar arrangement is provided
on the other side of loom. But the nose portion of the picking tappet is tilted by 180 degrees.

Working
As seen in Figure, when the bottom shaft rotates, the nose of the tappet also rotates. When the nose
comes against the cone, it strikes the cone. This causes a partial rotary movement of the vertical shaft.
The picking arm or picking stick thus swings inward with sufficient velocity to drive the picker.

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The shuttle being in contact with the tip of the picker is pushed across the shed. The picking arm is
returned to original position by the spring. The cone is always kept in contact with the shell portion by the
spring. For the next pick, the tappet on the other side is set in motion and the shuttle will be pushed out
of the other box. So, for every rotation of the bottom shaft two picks are inserted.

A- Picking tappet
A1- boss,
A2- Shell
A3- Nose
A4-Slots
B-Bottom shaft
C- Tapered cone
D-Vertical shaft
E- Top bracket
F- Foot stop bearing
C-Collar
H -Leather strap
I-spring
J-Bottom corrugated plate
K - Top corrugated plate
L -Picking arm or stick
M-grooved cap
N-Nut
O-Picking strap or band
P-Pin
Q-Picker
R-Shuttle

Mechanism of Over Picking

Over picking mechanism is used on cotton and jute loom. It is robust and easy to adjust and maintain. The
spindle is situated over the shuttle box and is essential to guide the shuttle along the correct path. It is
normally set slightly up and slightly towards the front of the loom and its inner end.
The back end of the shuttle will thus receive a similar lift at the end of the stroke, so that its leading end
will receive correct delivery down and into the shed. A flexible leather-picking strap is used to control the
picker.
The cone over pick motion consists a vertical shaft placed either inside or outside the loom framing. The
shaft serves as fulcrum of the picking arm, it is held against the loom frame. There is a spiral spring at the
picking shaft, which causes the picking arm and picker to move back after the delivery of the pick.
At the two end of the bottom shaft, two picking cams are fixed. In revolving its nose the tappet strikes the
cone shaped ant frictional roller strut, positively rotates the shaft and causes the shuttle to move inward
with sufficient velocity to drive the shuttle across the loom. The timing of the picker begins to move can
be attend by turning the picking tappet on its boss.

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Under pick mechanism

If the fulcrum of the picking stick is below the level of the shuttle box, then the picking mechanism is
known as an under pick mechanism.
The types of under pick mechanism are
I. Cone under pick mechanism
2. Side-lever under pick mechanism
3. Side-shaft under pick mechanism.
Of the above types, the side-lever under pick mechanism is the one mostly used.

Cone Under pick Mechanism

Construction

A - Picking tappet
B - Bottom shaft
C- Nose
D – Cone
E- Side shaft
F-Lug strap
G -Picking stick
H - Picker
I - Shuttle
J- Spring and pivot

As shown in Figure, a picking tappet is fixed

to the bottom shaft B. The picking tappet
has a nose bit C. A cone D is fixed to a side
shaft E, which in turn is connected to a lug
strap F. A picking stick G is looped by the lug
strap. The top of picking stick carries a
loosely mounted picker H, which is free to
move on a spindle. A shuttle I is in contact
with the picker. The bottom of the picking
stick is pivoted and connected to a spring J.
A similar mechanism is fitted on the other
side of the loom. But the picking tappet
nose is tilted by 180°.

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Working
When the bottom shaft rotates in the direction shown, the picking tappet also rotates. When the nose of
the tappet comes against the cone, it strikes the cone. This causes a partial rotary movement of the side
shaft. The end of the side shaft thus pulls the leg strap and hence the picking stick moves inward with
sufficient velocity to drive the picker. As the shuttle is in contact with the picker, it moves out and reaches
the opposite box. The picking stick is returned to its original position by its spring. So for every rotation of
the bottom shaft, two picks are inserted. For the next pick, the tappet fitted on the other side of the loom
will work and the shuttle will move out of the shuttle box.
The timing of the picking can be altered by appropriately tilting the tappet on the bottom shaft. The
strength of pick can be altered by raising or lowering the lug strap. By lowering it, the strength of pick is
increased and vice-versa.

Side-Iever under pick Mechanism

Construction
A side-lever under pick mechanism is shown in Figure, A circular disc A is fixed to the bottom shaft B. The
disc contains slots. A bowl C is fixed in one of the slots. Side lever D, which is below the disc, carries a
picking shoe E at the centre and is connected to a bracket F and spring G at the back end. The bracket acts
as a fulcrum for the side lever. A guide H is used to guide the side lever during its motion. The lower front
end of side lever touches an elbow J, which carries the picking stick K. A picker L is loosely mounted on
the picking stick. The elbow is connected to a coiled spring M, which is in a housing bracket. The elbow is
connected at the bottom to a rocking shaft N. A buffer is fixed to the side frame of the loom and a check
strap is in the slot of a bracket provided below the shuttle box. The picker is kept in contact with the tip
of the shuttle O, when it is in the shuttle box.
A- Circular disc
B - Bottom shaft
C- Bowl
D - Side lever
E - Picking shoe
F - Bracket
G - Spring
H- Guide
J- Elbow
K - Picking stick
L- Picker
M- Spring
N - Rocking shaft
O- Shuttle

A similar arrangement is provided on the other side of the loom. But the position of the bowl on the
circular disc is shifted by 180 degrees. So, for the first 180 degrees the rotation of the bottom shaft, the
shuttle is delivered from one side and for the next 180 degrees, it is delivered from the other side. Thus
one revolution of the bottom shaft introduces two picks.

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Working
When the bottom shaft rotates in the direction shown in the figure, the bowl also rotates with the circular
disc. As the bowl comes against the shoe, it strikes the shoe and thus lowers the forward end of the side
lever. This in turn hits the elbow down and the picking stick moves towards the centre of the loom. The
picker, loosely mounted on the stick, moves and pushes the shuttle into the shed. At the end of the motion
the stick and the side lever are returned to their original positions by their spring respectively.
A similar arrangement of parts is provided on the opposite side of the loom to enable the return of the
shuttle for the next pick. When the pickings parts on one side of loom are in action, those on the other
side are out of action. The check strap is used to reduce the speed of the shuttle and prevent it from
rebounding. The guide-bracket guides the lever while it is moving. There is also a buffer to absorb the
shock create during the motion of the picking stick.

Side shaft under pick mechanism

Construction
As shown in Figure, a disc A is fixed to the bottom shaft B. A bowl C is fixed in the slot of the disc. Below
the disc, a curved shoe D is connected to a side shaft lever E. The side lever is in turn connected to a lug
strap G by a connecting lever F. A picking stick H is in the loop of the lug strap G. The top of the picking
stick carries a loosely mounted picker I. The shuttle K is in contact with the picker. The bottom of the
picking stick is pivoted at L and connected to a spring J. A similar mechanism is fitted on the other side of
the loom. But the position of the bowl on the disc is titled by 180 degree.

A- Disc
B - Bottom shaft
C - Bowl
D-Shoe
E- Shoe-shaft lever
F- Connecting lever
G - Lug strap
H-Picking stick
I- Picker
J- Spring
K - Shuttle
L – Pivot

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Working
When the bottom shaft rotates in the direction shown, the disc also rotates in the same direction. When
the bowl comes against the shoe it strikes the shoe. This causes the side shaft lever to depress and pull
the leg strap through the connecting lever. So the picking stick is pulled inward with sufficient velocity to
drive the picker. As the shuttle is in contact with the picker, it is pushed. The shuttle thus reaches the
opposite box. The picking stick and side shaft lever are returned to their original positions by return
springs. For the next pick, the disc on the other side of the loom will work and the shuttle will come out
of the opposite box.
Thus, for one rotation of the bottom shaft, two picks are inserted.
The timing of picking can be altered by changing the position of the bowl in the disc slot.
The strength of pick can be altered by raising or lowering the lug strap. By lowering the lug strap the
strength of the pick is increased and vice-versa.

Parallel Motions
Necessity for parallel motions:
In under pick mechanisms, the picker is mounted loosely on the picking stick. As the picking stick moves
with its fulcrum at the bottom, the picker adjusts itself with the shuttle box and moves in a straight path.
So there is a greater wear and tear of the picker and it is not suitable for high-speed looms. The stick
moves along an arc if the picker is fixed rigidly. So the shuttle could fly off.
Automatic looms of the wider type and heavy looms require more power for picking. In these looms, it is
necessary to have higher strength of pick. So the picker is fixed tightly on the picking stick.
Hence to get a straight horizontal path for the picker and to improve the life of the picker the parallel
motions were introduced.
Principle:
The principle of parallel motion involves varying the height of the fulcrum of the picking stick during
picking. So the picker will follow a straight and horizontal path.
Methods:
There are two methods of achieving horizontal movement of the picker. These are:
I. Parallel pick method and
2. Link pick method.
I. Parallel pick method:
This is also called Steam’s parallel motion. This method was invented to rectify the above defects in the
under pick mechanism.
Steam’s Parallel Motion:
This motion consists of mounting the picking stick A on a curved shoe B that rocks evenly on a flat surface
C so that the top of the stick does not move along the arc of a circle but maintains a straight line. The
picker D is also screwed firmly to the top of a stick so that the spindle and box guide plates are removed,
C is the flat surface fixed parallel to the loom-rocking rail E at the foot on the sley. The shoe B is slotted at
the front to engage with the projection F. A lug strap G drives the picking stick.
A metal bracket H is bolted to the front of the stick. A coiled spring I in the drum J is coupled to the picking
stick. The strap K returns the stick after picking. The curved shoe changes the fulcrum of the picking stick
as it advances to eject the shuttle. This enables the picker to move parallel to the base of the box. So, the
shuttle L moves in a horizontal plane. After this the picking stick comes back to its original position by
means of the strap K and the coiled spring I. The parts are shown in Figure.

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A-Picking slick
B- Curved shoe
C - Flat surface
D-Picker
E-Rocking rail
F-Projection
G-Lug strap
H-Metal bracket
I- Spring
J-Drum
K-Strap
L-Shuttle

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2.4.3 – Beat-up Motion

Object of Beat-up Mechanism
The object of the beat-up mechanism is to push the last laid weft thread into the fell of cloth by means of
a reed.

Beat-up Mechanism
Crank and Crank Arm Beat-up Mechanism
Construction
In Figure, A is a reed fixed at the top by a reed cap B and at the bottom in between a reed case C and race
board J. Crank shaft E carries a crank F. The crank is to a connected to a arm G, which is in turn connected
to a sley sword D by a gib and cotter joint and a connecting pin H. There are two sley swords on either
side of the race board connected by a rocking rail I
Working:
A-Reed
B-Reed cap
C-Reed case
D-Sley sword
E - Crank shaft
F-Crank
G-Crank arm
H-Sword pin or Connecting pin
I-Rocking shaft or Rocking rail
J-Race board

As the crank shaft rotates, its rotary motion is converted

into a to-and-fro motion of the connecting arm.
Therefore the sley swords move forward and backward
and so does the reed.
When the sley comes to the front centre the sley is at its
forward most point of movement.
The reed that is connected to the sley swords at the top
is in contact with the cloth. As the sley moves forward,
the reed beats the just-laid pick into the fell of the cloth.

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Eccentricity of Sley
Definition
It is defined as the unequal spaces travelled by the sley in equal units of time. This means that the forward
movement of the sley is faster than its backward movement.
1. In equal units of time the distances travelled by the sley are unequal.
2. The speed of the sley at beat-up is faster than its speed at the time of picking.
The amount of eccentricity in the sley’s motion depends upon:
1. Length of crank
2. Length of crank arm

Simple Method for Calculating Eccentricity of Sley

A – Position of the connecting pin when the sley is in contact with the cloth (Front centre)
B – Position of pin at Back centre
D – Top centre
C D – Crank arm
E D - Crank

In figure, C D is the crank arm and E D is the crank at the top centre. A is the position of connecting pin
when the sley is in contact with the cloth, that is when the crank is in the Front centre. B is the position of
connecting pin when the sley is in backward position that is when the crank is in the Back centre. C is the
position of connecting pin when the sley is in midway, that is when the crank is at the Top centre.
Consider that the crank is 3” length and crank arm is 12” length. The connecting pin moves 6” from front
to back and back to front, from A to B and B to A.
In the right angled triangle CDE, CE2 + DE2 = CD2 or
CE2 = CD2 - DE2 that is CE2 = (122 - 32) = (144 – 9)
CE2 = √135 that is CE = 11.61”
AB = 6” and AE = 12” + 3” = 15”, Therefore
AC = (AE – CE) = (15” – 11.61”) = 3.39” = distance covered from centre to forward and again to centre
CB = (AB – AC) = (6” – 3.39”) = 2.61” = distance covered from centre to back and back to centre
This proves that the distance covered from centre to forward and again to centre is more; but the distance
covered from centre to back and back to centre is less with the given amount of time. Hence the speed of
sley from centre to forward and again to centre is more for beat –up and the speed of sley from centre to
back and back to centre is less. This proves that in equal units of time the distances travelled by the sley
are unequal which is called eccentricity.

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Timing of primary motions in tappet loom

The circle of timing, shown in the figure, is typical on most tappet looms. The direction of the rotation of
crank shaft is as shown by the arrow. The order of the rotation of the crankshaft may also be reversed as
is generally done on the American looms. In the figure, the positions for the timing of the sley, shedding
and picking have been located in over pick and in under pick tappet looms.

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