Picking--- 1 Lecture 3

Define picking In a woven fabric weft inserted through a shuttle or without shuttle. The process of weft insertion process is called picking.

Classification of picking

Essential features of picking The weight of a shuttle & the time taken to move it. Kinetic energy in the picking mechanism should remain constant. A shuttle should begin to move slowly , develop a speed until it reaches the middle of the sley center & from the center to the opposite side corresponding decrease should take place. This will give low & uniform acceleration radiation value. A shuttle should be under complete control through out its movement and loom should be starting & stopping together.

Over picking & Under picking If the picking is done due to picking arrangement situated upon the shuttle box then it is called over picking. Under picking:- If the picking mechanism is done due to picking arrangement is situated under the shuttle box is called under pick.

Difference between the two pick mechanism Over picking Under picking The position of picking arm above the shuttle box The position of shuttle arm under the shuttle box Higher loom speed Lower loom speed. Less power consume Consume more power Less clean mechanism More cleaning mechanism Gentle action Rough in action Less wear & tear Higher wear & tear

Over picking mechanism Follow figure book (weaving byM.k. Talukder page 44)

construction It contains a vertical picking shaft, placed either inside or outside of the framing. The picking shaft consists of a shuttle spindle which is passed through a slot in picking shaft. Picking tappet placed in contact with picking cone. The picking tappet mounted on bottom shaft. A spiral spring is connected to the picking shaft returns the cones to the surface of the picking tappet after every throw. The picking tappet is made up of three parts Boss, shell, nose. Three leather straps namely check strap, spindle strap, & control strap used to ease the impact of the incoming shuttle.

Working principle Bottom shaft drives the picking tappet. In revolving picking tappet nosse, stick the cone shaped antifriction roller on the stud & partly rotates the picking shaft & lever. picker gets angular movement from the to & fro movement of picking arm which is responsible drive with sufficient velocity to drive the shuttle across the loom. When picker strikes the shuttle the shuttle moves into the open shed through race board. Picking is done. The spring causes the picking arm & picker to move back after the delivery of pick

Under picking

Under picking The important change in this mechanism is the elimination of picking spindle. In this mechanism picking stick remains under the shuttle, picker slides on a spindle which is positioned in front of the shuttle box. When the picking stick moves from the bottom of the box & fulcrum of the stick is below it is called under pick motion. The only disadvantage of this mechanism is the tendency for the shuttle to fly out.

Side lever Under picking

Construction A wooden side lever A fulcrum at O. A picking shoe B fixed on the side lever. A wooden picking stick C fixed to an iron shoe D. The forward end of the side lever is resting on that this shoe. The picker E is loose on the picking stick & is guided between the bottom groove of the shuttle box and a projected part along the top edge of the box. The side lever is struck down by a bowl F as it revolves with the striking disc G fixed to the bottom shaft. The picking stick is fulcrum at Q is mounted on a casting that is fixed to the rocking rail. A spiral spring is attached at the bottom of the iron shoe D which returns the picking stick after each forward stroke.

Working principle Picking starts when the sley is about 60 mm back from the dead center (85 degree crank shaft revolution) & the picking bowl comes in contact with the nose. Stroke of the picker occurred when the loom is rotated by hand depends upon the width of the loom. Picking stick return the spring should be just sufficient to bring the stick back after picking.

Faults of picking Early picking. Late picking Harsh picking Shuttle trapping Shuttle fly out. Etc fault. Follow books weaving M.K Talukder. Weaving –1 Ali haider shiblu