Tappet Shedding

PREPARED BY-
SABUJ BARMAN
FABRIC ENGINEERING
BANGLADESH UNIVERSITY OF TEXTILES (BUTEX)
What is tappet & tappet loom?

 Tappet :
 A tappet is a shedding tool placed on the bottom of a loom in
order to produce a pattern by using a limited number of
healdframe.
 Tappet loom :
 The loom in which shedding is done by tappet is called tappet
loom.
 Scope of tappet :
 Theoretically 12 heald frames (Maximum)
 Practically 8 heald frame (Maximum)
Types of tappet shedding

 1.Negative tappet shedding:

 All negative tappet shedding require the addition of pullers, stocks
and bowls, springs or dead weights to reverse either pulls the heald
down or lifts it.
 Lifting  Top riversing roller
 Lowering  Mechanically
 2.Positive tappet shedding:
 The positive tappet shedding give both upward and downward
movements to healds without the aid of any additional mechanism.
 Lifting and Lowering  Mechanically
 Negative Tappet
Shedding Mechanism
Main parts of tappet loom
 Weaver`s beam
 Back rest roller
 Lease rod
 Drop wire
 Heald frame
 Reed
 Shuttle
 Sley & Race board
 Front rest roller
 Take up roller
 Nip roller
 Cloth roller
Main parts of tappet loom

 Treadle lever
 Bowl
 Tappet
 Lamb rod
 Top reversing roller
 Leather strap
Yarn to fabric path diagram of a
tappet loom
Figure of tappet shedding mechanism
Construction of the mechanism

 Tappet achieve motion from bottom shaft.

 The bowls are placed on the surface of treadle lever.
 Both treadle lever are connected to lamb rod.
 Lamb rods, Heald Shaft, Leather Straps are connected to front side
of treadle lever.
Working principle

 Tappets are receive motion from bottom shaft.

 When tappets rotate the nose of tappet strike on the bowls of treadle lever
which move down with every strike.
 The treadle lever pull the lamb rod when tappet strike on it. Due to the
pulling operation the heald shaft also move downward.
 There is returning spring set up to the top of the loom frame to send back
the heald frame to previous position.
Difference between tappet and
ordinary cam
Tappet Ordinary cam
1. It gives motion to a shaft to 1. It gives a continuous reciprocating
receive a series of lifts with motion
intervals of rests.
2. It is mainly used to produced shed 2. It may be used for many purposes

3. All tappets are cam 3. All cams are not tappet

Conditions of good shedding

 A shed should be as small as the nature of the work to be done.

 Healds should be placed at right angles with the warp threads.
 Exact vertical movement of the heald shafts are required.
 Perfect leveling of the heald shaft .
 The heald shafts must begin to move slowly .
Learning outcomes

What have We learnt from today’s class? let’s discuss

again…………
 Positive Tappet
Shedding Mechanism
PREPARED BY-
SABUJ BARMAN
FABRIC ENGINEERING
BANGLADESH UNIVERSITY OF TEXTILES (BUTEX)
Main parts of positive shedding
tappet
A. Tappet shaft
B. Tappet
C. Track
D. Bowl
E. Tappet lever
F. Fulcrum
G. Link rods
H. Fulcrum
I. Heald wire
J. Heald shaft link
K. Heald shaft
Figure of the positive tappet
shedding mechanism
Construction of the mechanism

 The tappet shaft carries another tappet which has a groove or track
in which a bowl is placed.
 The bowl is connected in turn to a tappet lever with link rods, link J
and a heald shaft.
 Each tappet is separately connected to a heald shaft through link
rods and tappet lever.
 There are two fulcrums for tappet lever and links.
Working principle

 When the tappet is rotated, the bowl is also rotated.

 According to the shape of the groove, the bowl is moved up or
down or remains still.
 If the bowl is moved up, the tappet lever moves to the right through
the links G and J and the heald shaft is lowered.
 If the bowl is moved down, the tappet lever moves to the left and
the heald shaft is raised.
 Since the heald shaft is raised and lowered by means of the
mechanism, this tappet shedding is known as positive tappet
shedding mechanism.
 When the bowl stands still, the heald shaft is in the ‘dwell’ stage.
Tappet driving

 The plain weave tappets are usually place on the bottom shaft as
the former give two picks to the round.
 But in case of weaving a twill or satin, the tappets are always
placed on a short shaft known as counter shaft.
 The bottom shaft imparts motion to the counter shaft either directly
or through a carrier wheel.
 The counter shaft must always rotate once for as many picks as
there are to round.
 The relative speed of the crank shaft and the bottom shaft is 2:1 .
Gearing diagram of a tappet
loom (1)
calculation
 R.P.M of motor : 960
 Motor pulley dia = 3"
 Machine pulley dia = 24"
 No. of teeth of crank shaft wheel = 38
 No. of teeth of bottom shaft wheel=76
 R.P.M of crank shaft = 960 X (3/24) = 120
 R.P.M of bottom shaft = {960 X (3/24) X(38/76)}
= 60
Gearing diagram (2)
Calculation

 R.P.M of motor : 960

 Motor pulley dia = 3"
 Machine pulley dia = 24"
 No. of teeth of crank shaft wheel = 38
 No. of teeth of bottom shaft wheel=76
 R.P.M of crank shaft = 960 X (3/24) = 120
 R.P.M of bottom shaft = {960 X (3/24) X(38/76)}
= 60
 R.P.M of counter shaft =60 X (40/80) =30
Chart of different shafts

No. of
division
Ratio Ratio
Crank Bottom Counter Tappet tappets
PPM between between
shaft shaft shaft Design /No. of loom
T.S. & C.S. B.S. & C.S.
cycle in
tappet

200 200 100 0 𝟏 2 × ×

𝟏
300 300 150 100 𝟐 3 3:1 3:2
𝟏

400 400 200 100 𝟐

,
𝟑
4 4:1 2:1
𝟐 𝟏
 Tappet
Construction
PREPARED BY-
SABUJ BARMAN
FABRIC ENGINEERING
BANGLADESH UNIVERSITY OF TEXTILES (BUTEX)
Points to be taken under
consideration
 Weave design: 1/1 plain
 Lift of the tappet: 4″
 The distance from the center of the driving shaft to the nearest point
of contact with the treadle bowl - 2″
 Diameter of the treadle bowl - 2″
 Dwell period =1/3 of a pick
Construction
 A circle ‘A’ is drawn of 2 in radius representing the distance from the
centre of the driving shaft or bottom shaft to the nearest point of
contact with the treadle bowl.
 A circle ‘B’ is drawn by adding radius of treadle bowl with A i.e. A =
2, B=A+1=3
 A circle ‘C’ is drawn of 7. 4 are added for the lift of the tappet. i.e.
C=B+4=7
 The pattern being a plain one, the circles must be divided into two
equal parts and each half circle will then represent one pick
indicated by the line DE .
 Each half circle is divided into three equal parts by lines FK, GH
 Each of FH and GK is divided into six equal parts.
Construction

 A semicircle L is drawn between B and C at a radius of half of the lift

of the tappet (i.e. 2)
 Divide the circumference of the semicircle into six equal parts.
 Draw perpendicular from the dividing points of the semicircle on the
line GH. This gives six unequal divisions on the lift to obtain the
desired eccentric shape of the tappet.
 From the corners of these unequal spaces and with the radius of the
treadle bowl, the drawn circles represent the position of the treadle
bowl at different parts of its movement.
 The curved lines are drawn touching the extremities of the treadle
bowl. This gives the outline of the plain weave tappet.
Figure of tappet construction
What is dwell period?

Dwell is the stationary period when

the heald frames do not change their
position and the shade remains open
to allow the passage of the shuttle
from one shuttle box to the other.
Factors affecting dwell of tappet

 If the loom width is lower, then dwell period will lower.

 Weave structure: complex structure  DP↑
Simple structure  DP↓
 Reed space lower and dwell period lower
 Higher picking force – Shorter dwell period
 Type of yarn: for, Finer yarn, shorter dwell period
And for, coarser yarn, higher dwell period
Loom Cycle and Timing

 Loom cycle :
 Loom cycle includes shedding, picking, beat up motions.
 Loom timing :
 Loom timing is defined as relative chronological sequences of
various primary and secondary motions are expressed in terms of
degree of crank shaft.
 Time available for Shedding…((60/PPM) * (Angle/360))
 Time available for Picking…..Same
 Time available for Beat uo….Same
Advantages of tappet shedding

 Simplest shedding.
 Cheapest of all shedding motions.
 If conveniently employed, it gives the best result within its capacity.
 It is capable of lifting heavy weights with less wear and tear of the m/c
than other shedding appliances
 Less wear and tear
 It can move healds at high speeds .
 Dwell period may be adjusted to suit the type of fabric to be woven
 Puts less strain upon the warp threads
 Consumes less power and give greater output
 It causes fewer defects to the fabric
Defects of tappet shedding

 Over shedding strains and breaks the warp threads.

 Under shedding does not permit the passage of the shuttle through
the shed .
 Sometimes unequal shedding by lifting one end of the shaft more
than the other .
 Missed shedding
 Unsuited dwell period
 May impart jerky motion
Learning outcomes

What have we learnt from today’s class? let’s discuss

again…………