RAPIER LOOM

RAPIER WEAVING

SCHEME OF WEFT INSERTION

RAPIER WEAVING

RAPIER WEAVING

RAPIER WEAVING

Rapier Weaving Machine- ClassificationRapier Loom

Types ofRapier

Weft InsertionPrinciple

Single Double

Dewas Gabler

Flexible TelescopicRigid

Number ofRapier

RAPIER LOOM• A rapier loom uses a rapier to pull the weft yarn across the loom.

• It can be a single rapier or double rapier.

• For a single rapier, a long rapier device is required to extend across the full width of warp.

• For a double rapier loom, two rapiers enter the shed from opposite sides of the loom and transfer the weft from one rapier head to the other near the centre of the loom

• The advantage of two rapier system is only 50% of the rapier movement is utilized in the weft insertion of single rapier loom

• Very light fabrics with 20 GSM to heavy fabrics with around 850 GSM.

• Rapier machines are widely used for household textiles and industrial fabrics.

• Rapier machines are designed for universal uses like

– Weave classic Wool, Cotton, Man-made fibres, fine Silk and Fancy yarns.

RIGID RAPIER

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Thin-wall tubes,~ 10 to 15 mm Ø, or hollow bars of rectangular cross section

•Advantages

• They do not require guiding across the warp sheet; the rapier head slides on the warp, or on the raceboard.

• High mass and rigid construction ensure straight movement of rapier heads.• A great diversity for both warp and weft threads in yarn count and character.

•Disadvantages

• Large floor space requirement at least twice the fabric width.• Half of their movement is wasted.

FLEXIBLE RAPIER Tapes of rectangular cross section, 25 x 10 mm, made of spring

steel or plastic.

They require guiding across the shed especially for larger workingwidths.• The ribbed guide is similar to that used with the gripper projectile

weaving machines• Directing the flexible-rapier band through a fixed housing on the

loom frame just outside the reed (no guide mounted in the sley)

FLEXIBLE RAPIERAdvantages:

• Less floor space requirement, spatial productivity is higher.

• Flexible rapier band are wound on wheels or placed in a semi- circular channels

when they are withdrawn outside the shed, and the result is wide working widths

up to 5 m.

Disadvantages:

• Guiding system may lead to the end breakages due to knot failure.

• Using fancy yarns in warp direction is almost impossible.

• By eliminating guides, there is the advantage of reducing end- breaks due to knot

failure, and the weaving of fancy yarns becomes much easier because the

obstructions are removed from the warp shed.

TELESCOPIC -RAPIER

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• The disadvantage of the large floor space requirements of rigid rapiers is removed

on weaving machines equipped with telescopic rapiers.

• Space can be saved on this type of rapier drive if a compound rapier operating on

the principle of telescopic expansion is used.

• This system is used on the Vamatex, Versamat loom.

• The main outer body of the rapier is driven by the eccentric, but the inner body is

fastened to a tape at its outer end. The tape is attached to a fixed point on the

loom, and it passes round four pulleys.

• When the rapier is out of the shed, the inner rapier is withdrawn inside the outer

rapier but, as the outer rapier is driven towards the center of the loom, the tape

slides round the rollers so that the inner rapier moves in the same direction at an

even faster rate.

SINGLE RAPIER WEAVING MACHINE

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The rigid rapier is a metal or composite bar usually with a circular cross section

The rapier enters the shed from one side, picks up the tip of the weft yarn on

the other side and passes it across the weaving machine while retracting

Single rapier carries the yarn in one way only and half of the rapier movement is wasted

Rapier length is equal to the width of the weaving machine

Requires high mass and rigidity of the rapier - to ensure

straight movement of the rapier head

Single rapier machines are not popular

Advantage

• Problem of weft transfer does not arise and normal range of fabric can be

woven.

Disadvantage

• One movement of rapier is wasted.

• Loom speed is very slow. The maximum weft insertion rate is 400 m/min

DOUBLE RAPIER WEAVING MACHINE

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They may be rigid or flexible.

Two rapiers enter the shed from the opposite sides and meet at the center.

The double rapier weaving machines are subdivided into:

• One-sided weft insertion. One rapier is the transmitting rapier the other is the

taker rapier.

• Double-sided weft insertion. Each rapier acts alternately as the giver and the

taker.

The giver picks up the yarn from the accumulator at one side, brings it to the

center of the shed, transfers it to the second rapier (taker).

As the taker retracts, carries the yarn to the other side.

In a twin-rapier system, two rapiers move together from the same driving

• source, as is necessary in face-to-face (i.e., double-plush) weaving.

TIP AND LOOP TRANSFER SYSTEMTip System

• Package is equipped with a spring

loaded tip and is transferred has a

spring loaded clamp

• The tip of the weft yarn is firmly

gripped by the rapier heads during the

entire period of weft insertion.

• Firmly gripped by the rapier heads.

• spring-loaded clamp presses to

trap the weft.

Loop transfer system

• weft from supply package exhibits a fork-

like opening

• Weft insertion in the form of hairpin.

• Weft yarn is not firmly gripped, merely

threaded round the rapier head.

• extends the yarn in the form of ‘ U’ shape

(loop) to the center

• During retraction of the receiving head, the

loop of weft gets unfolded over the

corresponding part of warp shed After

transfer of loop the thread is retracted to

straighten back.

Tip Transfer

• spring-loaded clamp has a cam profile

that meets a fixed point on the loom.

• The possibility of weft breaks at

transfer is minimized.

• There is minimum chance of the

weft’s being pulled out of the receiving

spring.

• Basically for softer and higher english

count yarn

• yarn thickness, its compressibility and

coefficient of yarn-metal friction govern

reliability of tip-to-tip transfer.

Loop transfer

• Both rapier extends to the outside of

the weaving machine, the space

requirement is high

• Transfer of weft yarns at loom centre

thus imposes a severe restriction on

velocity

• Rigorous abrasion during weft transfer

and shed opening.

• suited for rough and robust yarns and

yarn paprameters do not significantly

affect the system.

DEWAS SYSTEM - (TIP TRANSFER) Tip to tip weft insertion principle (Tip transfer principle)

The tip of the weft yarn is firmly gripped by the rapier heads during the entire

period of weft insertion

Type of weft transfer at the center

• negative transfer: all flexible rapiers

• positive transfer: Dornier rigid rapier (gentle treatment)

The giver grips the tip of the yarn, brings it to the center and transfer it to the taker

which retracts and carries the yarn to the other side of the weaving machine

RAPIER HEAD FOR DEWAS SYSTEM The gripping unit: a fixed point against a spring-loaded clamp presses to trap the

weft. The spring-loaded clamp has a cam profile that meets a fixed point on the loom or sley-

mounting. These points open the clamps when the weft is to be picked up or released outside the selvedge.

The right-hand head thus traps the weft at A and pulls it through the shed until the rapiers meet. The thread is then guided round point B and, as the left-hand head withdraws, the thread is trapped at C and pulled across the loom to complete insertion.

In some looms, at time of transfer clamping points in the rapier heads are positively controlled and opened. The possibility of weft breaks at transfer is minimized. Furthermore, there is no chance of the weft’s being pulled out of the receiving spring.

PRINCIPLE OF GABLER SYSTEM (LOOP TRANSFER)

Weft insertion in the form of hairpin – Loop transfer principle The weft yarn is not firmly gripped, merely threaded round the rapier head. After its transfer at the center, it is straightened as the taker retracts the

shed. The giver extends the yarn in the form of ‘ U’ shape (loop) to the center of the

weaving machine The yarn is then transferred to the taker, which extends the yarn to the

other side of the weaving machine by straightening it Both rapier extends to the outside of the weaving machine, the space

requirement is high

RAPIER HEAD FOR GABLER SYSTEM

The weft is never gripped. It is threaded round the cut-out A in the right-hand rapier head. As the rapier advances towards the center of the loom, the yarn

is introduced in the form of a hairpin. When the two rapier heads meet at the center of the loom, the

smaller left-hand rapier head enters the yarn-carrying right-hand head.

The thread at A is passed under the spring-loaded cover guide at B, and, as the left-hand rapier is withdrawn, it repositions the weft at C.

The yarn can then slide through the left-hand rapier head as it is withdrawn so that the hairpin is straightened out.

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RAPIER DRIVES

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• The rapier motion is mechanically linked with the machine motion

• The rapier motion is completely under control, thus the position of the weft yarn

at any instant during picking is exact

• There are various attempts and alternatives to drive the rapier Systems are still

changing to obtain a smooth picking operation at high loom speeds

(acc/dece/acc/dece)

• The rapier drive should ensure a gentle treatment to the weft yarn while it is being

picked up by the giver rapier or while it is being transferred between rapier heads.

• The rapier head acceleration and its speed are important since the type of motion

results in high forces acting in the body of the yarn.

• If the forces exceed acceptable limits, the weft yarn breaks off.

• The unwinding speed of the weft yarn is determined by the rapier movement.

FLEXIBLE RAPIER DRIVE FROM OSCILLATING SPROCKET

• The teeth of the sprocket pass through holes in a driving

• band.• The reciprocating movement may be given to the

sprocket by• a crank arrangement

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FLEXIBLE RAPIER DRIVE GROOVED CAM OPERATED MOTION

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FLEXIBLE RAPIER DRIVE : CRANK & RACK OPERATED

MOTION

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RAPIER DRIVE FROM ECCENTRIC

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RAPIER DRIVE FROM CYCLOIDAL GEARS

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TELESCOPIC RAPIER DRIVE

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RAPIER DRIVE : RADIAL CAM OPERATED MOTION

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SALIENT FEATURES OF MODERN RAPIER LOOM

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1. Loom speed have been achieved upto 700 PPM and WIR of upto 1400 MPM.

2. The drive assemblies are with no back lash and gearings are made largely redundant. This has reduced vibrations, floor loading and noise emission.

3. Speed variation within a loom can be achieved by means of frequency controlled DC or stepping motor.

4. There are electronically coupled individual drives for all the motions.

5. Starting marks have been prevented because of improvement in start up and acceleration.

6. Both warp and weft designs can be changed whilst the loom is running.

7. There are controlled weft tensioners to make optimum weft tension and give best performance.

SALIENT FEATURES CONT…

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8. The size of rapier heads have been reduced, so that the warpthread tension also reduced.

9. It is made possible to have automatic repairing of weft breaks.10. Loom design is made suitable for quick style change (QSC).11. Versatility of the loom has been increased to weave as many types

of yarns and fabrics.12. Power consumption has been reduced comparatively when

compared to that on old model.13. The selvedge waste has been reduced.14. There is increase in application of double shed weaving

technique for production of flat woven fabrics.15. Two-phase weaving has led to a very high production rates even

at low loom speed.16. Flexibility of the loom has been greatly improved by making it

easy and quick to change style.

SELVEDGE FORMATION IN RAPIER WEAVING M/C

Leno Selvedge:Leno selvedge is obtained by binding the wefts with strong additional threads working in gauze weave and by eliminating through cutting the protruding weft ends.

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LENO SELVEDGE FORMATION

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WEFT INSERTION RATE OR WEFT VELOCITY

Average velocity, v = distance/time

For Single Rapier Example:•A single rapier loom having a reed space of 180 cm and running at 225 picks/min will not have excessive velocities if the rapier can be made to enter the shed at 600 and leave at 3000. Calculate the average velocity of the rapier and WIR.

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WEFT INSERTION RATE OR WEFT VELOCITY

For Double Rapier Example:• If we consider a 2.0m double rapier machine

running at 500ppm and 1000m/min WIR with 22%, 6% and 22% respectively acceleration, dwell, and retardation for each rapier. calculate the avg. velocity, Max. velocity and acceleration of rapier.hints:-

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WEAVING PRODUCTION

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• The weaver frequently wants to know the productivity of a weaving machineexpressed in terms of square meters of fabric produced per hour. (P).

• Fabric production rate of a single-phase weaving machine:

60 x n ηP1 = x ……………..(m/h)

D x 100 100

P2 = P1 x b ............................................ (m2/h)

Where,• n is the machine speed in r.p.m.,• b is the fabric width in m,• η is the machine efficiency in percent (%),• D is the pick density per cm (ppc),• P1 is the productivity of the weaving machine in

terms of meters of fabricproduced per hour(m/h).