Shedding is the raising of the warp yarns to form a shed through which the filling yarn, carried by the shuttle, can be inserted. The shed is the vertical space between the raised and upraised warp yarns.bThe shedding mechanism separates the warp threads into two layers to form a tunnel known as shed. A shed may be formed by means of tappets, dobby, and jacquard.
Classification: Shed is classified according to the position of the ends:
Closed Shed is classified on two parts.
- Bottom Closed Shed,
- Center Closed Shed.
Open Shed are classified on two parts.
- Semi-open Shed,
- Open Shed.
Shedding mechanism is 5 kinds:
- Paddle shedding
- Tappet shedding
- Dobby shedding
- Jacquard shedding
- Combined shedding
Types of Tappet Shedding Mechanism: Generally there are two types of shedding
- Negative tappet shedding
- Positive tappet shedding
Negative Tappet Shedding: In a tappet shedding mechanism, if the tappet controls only one movement, either an upward or downward movement of the healed shafts, then the shedding is known as “negative tappet shedding”. The healed shafts are returned by some external devices like springs, dead weights, rollers, etc.
Positive Tappet Shedding: In a tappet shedding mechanism, if the tappet controls both upward and downward movements of the healed shafts, then the shedding is known as positive tappet shedding.
Main parts used in shedding:
- Motor
- Motor pulley
- M/C pulley
- Crank shaft
- Crank shaft gear
- Bottom shaft gear
- Bottom shaft
- Tappet
- Connecting rod
- Heald shaft
Top arm Working principle : In our loom tappet gets motion in the following way. At first machine pulley gets drive by belt from motor pulley. Then machine pulley, which is directly joined with the crank shaft, gives motion to bottom shaft. This crank shaft gives motion to bottom shaft via gearing. Two tappets are joined with the bottom shaft. So when bottom shaft moves then the tappets also rotate. When it gets contact with tradle bowl it lifts the tradle levers and the heald shafts are lifted by tradle levers via links. As this is a negative shedding tappet the heald shafts are lowered by their own weight.
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