MOTION IN WEAVING (Weft feeler):-

As we are discussing about the motions which are used to weaving to stop the machine immediately as the weft yarn breaks or absence in the shed for any reason . Now I am going to give another mechanism to stop the loom which known as WEFT FEELER MECHANISM.

Weft feeler mechanism:-

The function of the weft 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 running.

There are three main type of feelers;

(1) Mechanical.

(2) Electrical and

(3) Photo electronic.

(1) Mechanical weft feeler:-

When the sley moves towards 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 , the blade A is pushed straight back into the feeler casing and no direction of a pirn transfer takes place. With the reserve bunch of weft approximately a length of three pick of yarn is left on the pirn base. The feeler blade contacts the the smooth polished surface of base pirn and slide-way , contacting the trip lever connecting rod B , which in turn raises the trip lever C through the bell crank lever D .

Image of mechanical weft feeler motion.ref fabricclub blogspot.com

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 breast beam, to turn and effect a pirn change at magazine and during the next forward movement of the sley with shuttle on the magazine side box. The return spring in the feeler casing pulls the feeler blade to its normal position as soon as the contact of the pirn is over.

Electrical two pronged feeler:-

This type of weft feeler has designed when the transfer of the fully wound pirn from the weft replenishing unit to the shuttle is initiated electrically. It can be used with advantage on loom weavning delicate weft. The feeler is mounted on a bracket fixed to the near wall of the starting handle casing. The weft pirn is fitted with a metal sleeve on the barrel. A bunch of reserve of weft , sufficient for four pick across the loom must be wound pirn. Under normal running conditions, as the sley, moves forward and is almost at the front center, the weft on the pirn contacts the feeler prongs , which are pushed backward in to the feeler casing, against the pressure of return spring. However when the pirn is empty except for the reserve weft, the metal secure on the pirn barrel is exposed and comes in contact with the feeler prongs.

image of electrical weft feeler. Ref by fabricclub blogspot.com

The feeler prongs are connected to an electrical circuit. The circuit incomplete until contact is affected across the feeler prongs . As soon as the prongs come in contact with the metal sleeve on the pirn barrel, the circuit is completed energizing the solenoid and the electrical magnet box, so that the trip lever is lifted in line with the tripper heel which puts the pirn changing mechanism in action. The electrical circuit is broken when the sley moves backwards to break contact between the metal sleeve on the pirn and the feeler prongs.

Area of contact between the feeler and yarn is very small and does not damage the yarn. But it requires special types of pirns with a metal sleeve.

Optical (photo) electronic weft feeler:-

The weft pirn for this type of feeler is covered with effective strip which has property of reflecting a beam of light back to it source. The light source and the photo cell are housed together in the feeler head and both the searching beam and the reflected ray pass through the same optical system.

imagre of optical electronic weft feeler. ref by fabricclub blogspot.com

Incident light ray is directed on the pirn constantly and as soon as the weft is exhausted the light ray is reflected back to the feeler head . On the reading the photo cell the reflected light is transferred into an electrical impulse and transmitted to the switch box, which contains the whole electrical supply for the feeler and feeds the appropriate selection mechanism in order to initiate the transfer of pirns. Advantage of this feeler is that there is no physical contact between the feeler and the weft yarn. Main disadvantage is that it very expensive. Now a days for filament weaving this feeler is extensively used.

ref:-https://fabricclub.blogspot.com