AUTOMATIC SHUTTLE LOOMS

AUTOMATIC SHUTTLE LOOMS

Automatic shuttle looms are essentially simple power looms to which has been added means of automatic weft replenishment.

However, in order to gain full advantage of this latter feature, thus enabling a weaver to look after more looms, shuttle looms should also be equipped with an automatic warp let-off motion and an automatic warp-stop motion (which immediately stops the looms if a warp thread break occurs).

PROBLEMS OF NON-AUTOMATIC SHUTTLE LOOMS

Frequent replenishment of weft bobbin into the shuttle.

Loss of production.Weaver is not able to attend more looms. So

more weavers are required which adds to wage bills.

Manual adjusting of dead weight on the warp let-off motion, so varying warp tension.

Non-automatic warp stop motion, which stops the loom after some picks after end breaks, hence leading to defects in fabrics.

Poor quality of fabric.

ADVANTAGES OF AUTOMATIC SHUTTLE LOOMS

Automatic weft replenishing mechanism.Less loss of production.Weaver is able to attend more looms. So less

weavers are required and hence less wage bills.

Automatic let-off motion. So the warp tension is maintained constant throughout the fabric.

Automatic warp stop motion, which stops the loom within 2-3 picks after end breaks.

Better quality of fabric compared to non-automatic looms.

THERE ARE TWO TYPES OF SHUTTLE LOOMS:

1. PIRN CHANGING LOOMS – the empty weft package i.e. pirn, is ejected and immediately replaced with a new full pirn of weft.

2. SHUTTLE CHANGING LOOMS – ejecting the empty shuttle as some convenient time in the loom cycle and a new shuttle is inserted with a full weft package.

PIRN CHANGING LOOMSPARTS OR ATTACHMENTS ESSENTIAL

FOR PIRN CHANGING MECHANISM:◦Large shuttle and pirn with few

modifications◦Change in the design of shuttle boxes and

sley◦Rotary magazine to accommodate 24 – 30

fully wound pirn.◦Feeler mechanism on the starting handle

side to detect the almost exhausted pirn.◦Mechanism to push the fully wound pirn

from magazine into the shuttle and at the same time eject the empty pirn.

PIRN CHANGING LOOMS

◦Self threading device in the shuttle◦Device to cut the two ends of weft at the

selvedge of the cloth at the pirn changing side.

◦Shuttle protector mechanism, to prevent the changing mechanism from trying to insert a new fully wound pirn in the shuttle, if the shuttle fails to be exactly in the correct position for receiving the bobbin.

SHUTTLE

The shuttle used in automatic pirn changing loom is large in size in order to carry large quantity of weft yarn.

If small shuttles are used, the pirns will carry a smaller quantity of weft yarn, leading to greater number of pirn changes in a given time.

This will give greater wear and tear of the mechanism.

Also, a greater amount of waste yarn will result arising from the bunches on the pirns.

The work of battery filler will also increase.The shuttle is big, heavy and has thicker side

walls.

A shuttle should be provided with self threading device. The threading has to be done while the loom is running.

When the shuttle is picked from the magazine side, the weft thread is held on the top of the eye because the weft end is wrapped round the mandrel of the magazine front and gives sufficient tension for the first pick after the transfer.

On the second pick, the weft thread settles down in the groove of the self-threading device.

Since, most of the automatic looms are left handed, the self threading eye on the shuttle is fitted at the right hand end when viewed from the front of the shuttle.

The shuttle is provided with a slot at the front wall near the spring jaw. This slot allows the feeler blade of the weft feeler mechanism to pass through and touch the weft pirn.

Shuttle has a wide mouth at the top for entry of the pirn and wide opening at the bottom for ejection of empty pirn.

Shuttle is provided with spring jaw to hold the prin.

PIRN

The pirn base is fitted with suitable rings whereby it could be clipped in the spring jaw in the shuttle.

Most pirns are fitted with three rings.When the fully wound pirn is

transferred into the shuttle, it should lie perfectly at center for correct unwinding.

SHUTTLE BOXFollowing are some of the modification

in shuttle box:◦No picker spindle since cone over picking is

not suitable for pirn changing system.◦The bottom metal plate on the battery end

has a wider opening for an empty pirn to pass through.

◦The front plate on the starting handle side has a slot corresponding to the slot in the shuttle front for the feeler blade to pass through.

◦The front plate on the battery side has a slot for shuttle eye-cutter to pass through.

ROTARY MAGAZINE (BATTERY)

ROTARY MAGAZINE (BATTERY)

The rotary magazine which can accommodate 24 – 30 full pirns is mounted on the right hand end of the front rest, so that its bottom center is above the shuttle when the sley is at the beat up position and the shuttle is in its box.

The magazine consists of three main circular plates.

One plate is used for holding the pirn bas, the second for holding the tip of the pirn and the third to guide the unwound thread before it is anchored by wrapping it around a boss on the magazine front.

Each fully wound pirn is placed individually in the magazine, where it is held by a spring clip at its tip.

A little length of weft unwound from the pirn is anchored by wrapping it around a boss on the magazine front so that it will not be taken into the cloth when the first pick is inserted into the warp shed after a pirn change.

WEFT FEELERSThe function of the feeler mechanism is

to sense the weft on the pirn and initiate the pirn changing mechanism to act when the weft has been almost exhausted on the pirn.

If the weft is present on the pirn the feeler will allow the loom to continue working.

There are three main types of feelers:1. Mechanical2. Electrical3. Photo electrical

MECHANICAL FEELER

MIDGET SIDE SLIP FEELER

WEFT FEELERSThe function of the feeler mechanism is

to sense the weft on the pirn and initiate the pirn changing mechanism to act when the weft has been almost exhausted on the pirn.

If the weft is present on the pirn the feeler will allow the loom to continue working.

There are three main types of feelers:1. Mechanical2. Electrical3. Photo electrical

MECHANICAL WEFT FEELERSMIDGET FEELER

◦When the sley moves forward the feeler blade A, passes through the slots in the front plate of the box and front wall of the shuttle and contacts the pirn.

◦If there is sufficient weft yarn on the pirn, the blade A is pushed straight back into the feeler casing and no indication of a pirn transfer takes place.

◦With the reserve bunch of weft, approximately a length of three picks of yarn is left in the pirn base.

◦The feeler blade contacts the smooth polished surface of base pirn and slides side-ways, contacting the trip lever connecting rod B, which in turn raises the trip lever C through the bell crank lever D.

◦A tripper heel E attached to the weft fork hammer F, oscillating to and fro along with the weft fork hammer, comes in contact with the raised trip lever C and pushes it back in the direction of the arrow shown in the figure.

◦This will cause the change shaft G which runs across the width of the beam, to turn and effect a pirn change at the magazine and during the next forward movement of the sley with the shuttle on the magazine box side.

◦The return spring in the feeler casing pulls the feeler blade to its normal position as soon as the contact of the blade with the pirn is over.