7. Picking
7.1 Picking (Shuttle Picking Mechanism)
Objective of Picking
Objective of picking is to propel the weft carrying element (shuttle, projectile or rapier) or the weft yarn along
the correct trajectory maintaining requisite velocity through the shed in order to provide lateral sets of yarns in
the fabric. In this module, picking will be discussed with respect to shuttle loom only.
Loom Timing
Loom timing is defined as relative chronological sequences of various primary and secondary motions are
expressed in terms of angular position of crank. The loom timing is shown in the Figure 7.1.
Figure 7.1: Loom timing diagram for shuttle loom (early shedding)
Sley Motion
0° : Beat-up takes place and sley occupies its forward most position
180° : Sley occupies its backward most position
0°-180° : Sley moves backward
180°-360° : Sley moves forward
Picking and Checking
80°-110° : Picking mechanism operates
105°-110° : Shuttle enters in the shed
240°-250° : Shuttle leaves the shed
270° : Shuttle strikes the swell in the shuttle box
300° : Shuttle comes to rest
Shedding (for early shedding)
30° : Shed is fully open
30° -150° : Heald dwell (shed remains fully open)
150° -270° : Shed closes
270° : Shed closed or shed level
270° -30° : Shed opens again (in opposite direction)
Shedding (for late shedding)
120° : Shed is fully open
120° -240° : Heald dwell (shed remains fully open)
240° -360° : Shed closes
360° : Shed closed or shed level
360° -120° : Shed opens again (in opposite direction)
The operations have been delayed by 90 0 in case of late shedding.
Take-Up
0° -10° : Take-up (intermittent type)
Classification of Shuttle Picking Mechanism
Shuttle picking mechanisms are broadly classified as cone over-pick and cone under-pick mechanisms. Several
modification of cone under-pick mechanism manifest as parallel pick and link pick.
Cone Over-Pick Mechanism
The cone-over pick mechanism is shown in the Figure 7.2. A picking cam attached to bottom shaft displaces
the cone (picking cone) which is attached with the upright picking shaft. This causes rotation of the picking
shaft. As a result, the picking stick, which is attached to the uppermost end of picking shaft, swing in a
horizontal plane over the loom and transmits the motion to shuttle through picking strap and picker guided by
a spindle. Picking strap is a leather or polymeric belt which is flexible. Here picker is constrained by the spindle
to move in a straight line which otherwise would have followed a path of arc. Obviously, this restriction of path
is achieved at the expense of some energy. Moreover, pairs of picking cam and follower installed at either end
of the loom have seldom ensured picking of equal strength (force). The cams responsible for impulsive rotation
of the picking stick receive motion through bottom shaft. However, allied system of picking is having varying
elastic behavior (one of them is attached through a “stiff” short shaft while that at the further end through a
long “flexible” one). All these warrant frequent adjustment of picking-strap or picking cam and nose settings. A
system where a different cam and follower pairs are used for each end makes the matter work enduringly with
standardized settings. A cone over-pick mechanism on a loom is depicted in Figure 7.3.
Figure 7.2: Cone over-pick mechanism
Figure 7.3: Cone over-pick mechanism on a loom
Possible Adjustments for Strength and Timing of Over-Pick



Shortening picking-strap increases the shuttle speed, but timing of picking advances.
The picking tappet can be turned over bottom shaft for the adjustment of picking timing.
Lowering the picking cone in the slot increases the shuttle speed but timing of picking is delayed

(Figures 7.2 and 7.4).
Angular adjustment between picking shaft and picking stick also changes shuttle speed and timing

(unpredictable).
Large change in shuttle speed for wider loom can be achieved by changing either nose bit or the entire
picking cam.
Figure 7.4: Adjusting the position of picking cone
With the advent of automatic looms which comes with battery or magazines, the replacement of over-pick
system with cone under pick becomes inevitable. The latter provides space over and at one end of the loom
erstwhile occupied by it’s over pick counterpart.
Cone Under-Pick Mechanism
Cone under-pick mechanism is depicted in Figure 7.5. Here also a picking cam attached to bottom shaft
displaces the cone turning the picking shaft (side shaft) located horizontally. The other end of the picking shaft
is connected with upright picking stick through the picking strap (lug strap). This causes the picking stick to
move in a vertical plane and transmits the motion to shuttle by the picker attached at the upper end of it. In
this system the picking stick and other appendages are located below the shuttle trajectory while picking cams
and follower, as usual, below the loom and driven from bottom shaft. The system is naturally suitable for
automatic looms. Here picker slides over its spindle and picking timing is regulated by cam adjustment like in
over pick motion. An almost inextensible lug strap allows shuttle speed adjustment by either raising or lowering
it around picking stick. Absence of stretchable parts in under-pick system ensures the retention of correct
setting over long period in contrast with the cone over-pick mechanism. A cone under-pick mechanism on a
loom is depicted in Figure 7.6.
Figure 7.5: Cone under-pick mechanism
[Courtesy : The Textile Institute, Manchester]
Figure 7.6: Cone under-pick mechanism on a loom
Possible Adjustments for Strength and Timing of under-Pick



Timing of picking is changed by turning the cam on the bottom shaft.
Raising and lowering of the lug strap (picking strap) reduces and increases shuttle velocity respectively.
Two independent adjustments for velocity and timing of shuttle make the under-pick system less
complicated.
Parallel Pick
In a modified under-pick system, picker guiding spindle is eliminated and picker itself is kept attached to the
stick as shown in Figure 7.7. The lower end of the stick is made to oscillate over a curvilinear shoe which rests
upon a plate. The shoe and picker trajectory form the circumference of a semi-circle as shown in Figures 7.8.
This ensures picker movement in a perfect straight line and hence that of the shuttle which is a prime
requirement for high speed looms. Picking stick in its extension passes through the slot of a plate and
connected with loom frame through a spring for proper return.
Figure 7.7: Parallel pick mechanism
Figure 7.8: Principle of parallel pick mechanism
Link Pick
Attempt to increase loom speed further creates one unfavorable situation where contact between shoe and
plate is often disrupted resulting undesirable picker movement which deflects shuttle from its right path or
undue wear of it and even fly-out. Modification through link pick is done to overcome this limitation as shown
in Figure 7.9. Here a metal piece (M) attached to the lower end of the picking stick. M connects itself to a
bracket (B) fastened to the sley sword through two arms (A). Such four bar linkages are, as if, an irregular
quadrilateral whose shape and sizes in relation to the length and angular movement of the picking stick, if
properly designed can deliver very good result in terms of accuracy over a distance of 15-20 cm along shuttle
path and truly exercises positive control in the system even at very high speed.
Figure 7.9: Link-pick mechanism
[Courtesy : The Textile Institute, Manchester]
Catapult Effect
Generally, shuttle picking mechanism operates from 80° to 110° of angular position of crank shaft. Basically,
the picking duration comprises of two halves. In the early half (from 80° to 95°) the strain energy is built up
and in the later half (from 95° to 110°) the strain energy is released. The shuttle picking mechanism has a
close analogy with the action of a catapult. In this context, the shuttle represents the missile, picker represents
the leather part and picking stick and picking strap represent the elastic band. As in catapult, the strain energy
is developed in the first half by bending of picking stick,twisting of picking shaft and stretching of picking strap.
In the later half, the strain energy gets released and it accelerates the shuttle. Therefore, in the light of such
strong analogy the shuttle may be said to be catapulted by picking mechanism.
Experiment Name: -Study on the over pick mechanism.
Introduction:
Picking is the second primary motion in weaving. It consists in passing a pick of weft
between the upper and lower lines of a divided warp. It builds up half of the cloth. The
shuttle is the vehicle of weft for picking in the conventional and automatic looms.
Objectives:
1. To know the over picking mechanism.
2. To identify the different parts of this mechanism.
3. To learn the construction of over picking mechanism.
Types of picking mechanism:
1. Conventional or negative picking mechanism.
2. Unconventional or positive picking mechanism.
Conventional or negative picking mechanism:
In this mechanism, a carrier known as shuttle carries the weft yarn in a package called
pirn. The main function is:
a) To deliver the shuttle along the correct flight path.
b) To project the shuttle at a predetermined velocity.
Conventional or negative picking mechanisms are two types
1. Over picking
2. Under picking
Unconventional or positive picking mechanism:
In this mechanism, the weft yarn is inserted through the warp shed directly or positively
by air, water, projectile, needle or rapier. This mechanism is known as positive picking
mechanism.
Main Parts:
1. Picking arm
2. Picking strap
3. Picker
4. Bottom shaft
5. Picking spindle
6. Shuttle
7. Picking cam
8. Vertical shaft
9. Cone
10. Bowl
11. Angular
12. Crank shaft
Here,
A - Loom bottom shaft
B - Picking cam
C - Picking cone
D - Picking shaft
E - Picking stick
F - Picking band
G - Picker
Fig: Over Picking Mechanism
Features of Over Picking Mechanism:
1. Picking arm is over shuttle.
2. Suitable for narrow loom.
3. Higher picks per minute.
4. Less power required.
5. Works more smoothly.
6. Shortening the picking strap and changing the shape of the cam can increase picking
force.
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 leatherpicking strap is used to control the picker, which has tendency to stretched slowly in use,
and vary with regard to its elastic property.
The cone over pick motion consist 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 pick 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.
How to Increase PPM:
1. By increasing motor speed.
2. By setting the cone stud nearer to the picking tappet.
3. By decreasing the picking strap.
4. By altering the position of picking arm towards the centre of the loom.
5. By decreasing the length of the stroke of picking tappet.
Uses:
This is used for narrow and fast running looms, weaving light and medium weight fabrics
and for many narrow and wide looms for weaving heavy fabrics.
Conclusion:
The over picking motion is negative one; the exact amount of power is required to drive
a shuttle. By this experiment we learned about the over picking mechanism and how it
works. This experience will help us in our future practical life.
Experiment Name: -Study on the under pick mechanism.
Introduction:
Picking is the second primary motion in weaving. It consists in passing a pick of weft between
the upper and lower lines of a divided warp. It builds up half of the cloth. The shuttle is the
vehicle of weft for picking in the conventional and automatic looms.
Objectives:
1. To know the under picking mechanism.
2. To identify the different parts of this mechanism.
3. To learn the construction of under picking mechanism.
Types of picking mechanism:
1. Conventional or negative picking mechanism.
2. Unconventional or positive picking mechanism.
Conventional or negative picking mechanism:
In this mechanism, a carrier known as shuttle carries the weft yarn in a package called pirn. The
main function is:
a) To deliver the shuttle along the correct flight path.
b) To project the shuttle at a predetermined velocity.
Conventional or negative picking mechanisms are two types
1. Over picking
2. Under picking
Unconventional or positive picking mechanism:
In this mechanism, the weft yarn is inserted through the warp shed directly or positively by air,
water, projectile, needle or rapier. This mechanism is known as positive picking mechanism.
Features of under picking mechanism:
1. Picker arm is placed under the race board.
2. Suitable for wider loom.
3. Under picking work less smoothly.
4. More direct action.
5. Rough in action.
6. More clean mechanism.
7. Consumes more power.
8. Used for heavy weight fabrics in silk and rayon looms.
Under picking mechanism:
Main parts:
A =Treadle lever
B =Bowl
C =Fulcrum
D =Arm
E =Curve metal plate
H =Picking arm
I =Shuttle box
J =Coiled spring
S = Bottom shaft wheel
T =Leather band
P =Loom framing
Fig: Under picking mechanism.
In under picking mechanism a race board is situated over picking arm. Under picking is
controlled by picking cam which is fixed on the bottom shaft. At first the motion comes from
motor and m/c pulley.
Then the motion comes in to the bottom shaft and thus picking cam. When picking cam rotates
and its nose portion comes in contact with treadle lever and pushes it then the treadle lever
pushes the angular lever. The picking arm gets motion from angular lever which is connected
with picking arm. A picker is placed in the picking arm which pushes the shuttle. When shuttle
gets motion by picking arm then shuttle begins to move to and fro on the race board. Thus
picking is done.
A spring is situated which causes the picking arm and picker to move back after the delivery of
the pick. At the two end of bottom shaft, two picking tappets are fixed. By increasing nose length
picking
speed
may
be
increased.
How to increase PPM:
1. By increasing motor seed.
2. By increasing the nose shape of picking tappet.
3. By decreasing the length of picking arm.
Uses:
This mechanism is used in all non-automatic cotton looms. It is also used in jute looms.
Conclusion:
This picking mechanism is very important for loom. In the loom under picking is directly done by picker
and picking arm. Again under picking is necessary for weft yarn insertion. So we should learn about this
mechanism very carefully, this experience will help us in our future practical life.
picking mechanism
Extracts from the book "Woven Fabric Production - I."
published by the NCUTE, giving the technical information
about weaving, for the benefit of the members.)
(continued from Issue No. 10)
PICKING
3.1 Object of Picking Mechanism
The object of picking is to insert the weft yarn through the warp shed during weaving.
3.2 Types of Picking Mechanism
Picking mechanisms are classified into two main types. These are :
1. Conventional picking mechanism or negative picking mechanism
2. Unconventional picking mechanism or positive picking mechanism
3.2.1 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”.
A - Warp shed
B - Weft
C - Shuttle
Figure 3.1 Conventional picking
Figure 3.1 indicates the insertion of weft yarn by passing the shuttle through the warp
shed.
The main functions of the conventional or negative picking mechanism are :
a. To deliver the shuttle along the correct flight path and
b. To project the shuttle at a predetermined velocity.
3.2.2 Unconventional Picking Mechanism or Positive Picking Mechanism
In this mechanism, the weft yarn is inserted through the warp shed directly or
positively by air, water, a projectile, a rapier or a needle. Figures 3.2 to 3.6 illustrate
weft insertions of the direct, positive type. These mechanisms are therefore known as
“positive picking mechanisms”. Looms which do not use shuttles for weft insertion are
known as “shuttleless looms”.
A - Warp shed
B - Weft
C - Airjet
Figure 3.2 Weft insertion by means of an air-jet
Advantages of positive picking
1. In positive picking, a small depth of shed will be sufficient, because the picks
are passed through the shed by an air-jet, a water-jet, a projectile, a rapier or
a needle.
2. The risk of shuttle flying out of the shed is avoided in the positive picking
mechanism. In a shuttle loom, there is little control over the shuttle traversing
the shed. So there are chances of its flying out. But in positive picking, the
weft thread is controlled positively.
3. Positive-picking looms run at comparatively higher speeds.
4. Warp thread breakage is minimised due to smaller depth of sheds.
5. Mental and physical strain of the weaver is reduced appreciably.
6. Pirns are not required. So the pirn winding section is eliminated.
7. There is saving in floor space and labour.
8. Loom stoppages are minimised and so loom production and cloth quality are
improved appreciably.
A - Warp shed
B - Weft
C - Waterjet
Figure 3.3 Weft insertion by means of a
water-jet
A - Warp shed
B - Weft
C - Projectile
Figure 3.3 Weft insertion by means of a
Projectile
A - Warp shed
B - Weft
C - Rapier
Figure 3.5 Weft insertion by means of a
Rapier
A - Warp shed
B - Weft
C - Needle
Figure 3.6 Weft insertion by means of a
Needle
Disadvantages
Proper selvedges are not obtained in the cloth.
3.3 Conventional Picking Mechanisms
The two main types of conventional picking mechanisms are :
1. Overpick mechanism - Cone over pick mechanism
2. Underpick mechanisms - a) Side-lever underpick mechanism
b) Side-shaft underpick mechanism
c) Cone underpick mechanism.
1. Cone overpick mechanism
A picking tappet, driven by the bottom shaft and carrying a nose bit, hits a
cone, which in turn drives a vertical shaft. From here, the motion is
transmitted to the picker through a picking stick and picker. The picker pushes
the shuttle into the shed.
2.
a. Side-lever underpick mechanism
In this mechanism, a circular disc carrying a bowl is driven by the
bottom shaft. The bowl hits a shoe, which in turn depresses a side lever,
and the picking stick is driven. So the picker is pushed and the shuttle is
pushed out of its box into the shed.
b. Side-shaft under pick mechanism
A disc carrying a bowl is driven by the bottom shaft. The bowl hits a
shoe, which in turn drives the picking stick though a side-shaft lever and
connecting lever. The picker is pushed and the shuttle is shot out of the
shuttle box into the shed.
c. Cone underpick mechanism
The nose of a picking tappet, driven by the bottom shaft, hits a cone,
which in turn drives a side shaft. This in turn pulls a lug strap and
picking stick. The picker, connected to the picking stick, is pushed and
so the shuttle emerges from the shuttle box and traverses the shed.
3.4 Overpick Mechanism : The Cone Overpick Mechanism
Construction
As shown in Figure 3.7 the picking tappet A is fixed to the bottom shaft B. The picking
tappet A consists of three parts, the boss A 1 , shell A 2 , and nose A 3 . The boss is
keyed on to the bottom shaft and it carries the shell portion. The shell is provided
with two slots A 4 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 bite A 3 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 G, 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 of 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 is 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 the loom. But the nose portion of the picking tappet is tilted by
180 degrees.
Working
As seen in Figure 3.7, 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. The shuttle being in contact
with the tip of the picker is pushed across the shed. The picking arm is returned to its
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
A 1 - Boss A 2 - Shell A 3 - Nose
A4 - Slots
B - Bottom shaft
C - Tapered cone
D - Ver tical shaft
E - Top bracket
F - Foot step bearing
G - 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
Figure 3.7 Cone overpick mechanism
Timings and settings
1. The picking cone should always have contact with the picking tappet.
2. The nose bit of the picking tappet and the shell bevel should coincide with the
taper of the picking bowl.
3. If the cone is below the centre line of the picking tappet, a harsh and jerky
pick will result.
4. If the picking stick is far behind, there will be a loss in power of picking
because the stick will move some distance without moving the picker. If the
picking stick is very much forward, the stick is liable to hit the heald frames.
With the loom crank at the top centre, the part of the stick from where the
picking band leaves should be just above the spindle axis. When the picking
stick has moved three-fourths of its total traverse, it should be parallel to the
loom frame. The picking stick can be moved forward or backward by slackening
the nut at the top of the vertical shaft and turning the stick holder on the
corrugated plate.
5. The angle between the back plate of the shuttle box and its base should be
true to the bevel and correspond with the angle between the back and the
base of the shuttle (this is normally 87 - 90 0 ).
6. The reed and back plate of the shuttle box should be in line.
7. The groove in the front plate of the shuttle box should coincide with the groove
in the shuttle.
8. A broken or poorly fitted picker will cause a weak or erratic throw of the
shuttle. it will also give rise to weft breaks.
9. The central axis of the spindle should coincide with the central axis of the base
of the box.
10. Front plate setting.
With the shuttle in its box, the setting at the mouth end of the box should be
greater than at the back end by 2mm. Thus the shuttle should have free play at
the mouth side. See Figure 3.8.
Figure 3.8
11. The ver tical shaft should rotate freely when mounted.