Study on over picking mechanism.
Picking is the second primary motion in weaving. The action of inserting weft yarn through the warp yarns is called picking. It may be done by hand or by using devices like shuttle, gripper, rapier, air jet or water jet.
The functions of picking mechanism are:
- To deliver the shuttle along the correct flight length.
- To throw the shuttle at a predetermined speed.
- To know the over picking mechanism.
- To identify the different parts of this mechanism.
- To learn the construction of over picking mechanism
Features of over picking mechanism:
- Picking arm is over shuttle.
- Suitable for narrow loom.
- Higher picks per minute.
- Less power required.
- Works more smoothly.
- Shortening the picking strap and changing the shape of the cam can increase picking force.
Main parts of over picking mechanism:
- Picking arm
- Picking strap
- Bottom shaft
- Picking spindle
- Picking cam
- Vertical shaft
- Crank shaft
Mechanism of over picking:
Over picking mechanism is used on cotton and jute loom. It is robust and easy to adjust and maintain. The spindle is situated over the shuttle box and is essential to guide the shuttle along the correct path. It is normally set slightly up and slightly towards the front of the loom and its inner end.
The back end of the shuttle will thus receive a similar lift at the end of the stroke, so that its leading end will receive correct delivery down and into the shed. A flexible leather-picking strap is used to control the picker, which has tendency to stretched slowly in use, and vary with regard to its elastic property.
The cone over pick motion consists a vertical shaft placed either inside or outside the loom framing. The shaft serves as fulcrum of the picking arm, it is held against the loom frame. There is a spiral spring at the picking shaft, which causes the picking arm and picker to move back after the delivery of the pick.
At the two end of the bottom shaft, two picking cams are fixed. In revolving its nose the tappet strikes the cone shaped ant frictional roller strut, positively rotates the shaft and causes the pick to move inward with sufficient velocity to drive the shuttle across the loom. The timing of the picker begins to move can be attend by turning the picking tappet on its boss.
This is used for narrow and fast running looms, weaving light and medium weight fabrics and for many narrow and wide looms for weaving heavy fabrics.
How to increase PPM:
- By increasing motor speed.
- By setting the cone stud nearer to the picking tappet.
- By decreasing the picking strap.
- By altering the position of picking arm towards the center of the loom.
- By decreasing the length of the stroke of picking tappet.
The over picking motion is negative one; the exact amount of power is required to drive a shuttle. By this experiment we learned about the over picking mechanism and how it works. This experience will help us in our future practical life.
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Founder & Editor of Textile Learner. He is a Textile Consultant, Blogger & Entrepreneur. He is working as a textile consultant in several local and international companies. He is also a contributor of Wikipedia.