Tappet Shedding in Weaving: Details Discussion
What is Shedding in Weaving?
In the textile weaving industry, dividation of warp yarns into two parts for insertion of weft yarn is termed as a shed, and the mechanism of the shed is known as shedding in textile weaving. It is the first primary motion of weaving loom. it is done using treadles dobbies or jacquard, both in handlooms and power looms.
One kind of cam to which a rotary motion is provided to produce reciprocating motion in rods and levers by sliding contact. When the rod is to receive a series of lifts, with intervals of rest and thus forms a shed which is known as tappet shedding.
Major Parts of Tappet Shedding in Weaving:
All the parts of a tappet shedding have listed below:
- Motor pulley,
- Bottom shaft,
- Heald shaft,
- Bottom shaft gear,
- Machine pulley,
- Top arm,
- Connecting rod,
- Crankshaft gear.
Working Principle of Tappet Shedding in Textile:
- A pair of shedding tappet is connected to the bottom shaft or tappet shaft and two treadle levers are pivoted in the figure.
- The nose of the tappets pushes continuously the anti-friction bowl on the treadle lever when two tappets rotate or moves due to rotation of the bottom shaft. As one end of the treadle, the lever is pivoted, the other end of the treadle is lowered.
- This treadle lever is joined with the head shaft or frame by using a chain or rope and the heald shaft is joined with top rollers by rope. For this, the heald frame was lowered with warp yarn.
- The other heald shaft moves upwards due to the lowering of the other heald frame.
- As a result, the warp yarn forms a shed, and continuously shedding operation is performed.
Various kinds of tappet shedding are in use in the textile industry. Those are constructed on two principles, where one is positive tappet shedding and another one is negative tappet shedding.
In the woven fabric manufacturing industry, the positive tappet shedding provides both downward movements and upward movements to healds without the help of any additional mechanism. But pulleys and stocks and bowls are based on compensating principle. Here lifting and lowering are done mechanically.
The positive tappet sheddings are the following:
- Woodcraft section tappet,
- The oscillating or rocking tappet,
- Nutralls chain tappet
- Scroll tappets
- Open shed section tappet.
In textile weaving, all negative tappet shedding needs the addition of stocks, pullers, and bowls, springs, or dead weights to reverse either pulls the head down or lifts it. Here, lifting is done mechanically, and lowering is done by using spring.
The negative tappet sheddings are in the below:
- Jamieson’s tappets.
- The barrel tappet.
- The ordinary twill weave and plain weave shedding tappets.