PASSAGE OF MATERIAL THROUGH A PLAIN POWER LOOM

A plain power loom is a machine used in the weaving process that automates the
interlacing of warp and weft threads to produce fabric. It uses a simple up-and-down movement
of heddles to create a basic weave pattern, making it efficient for producing plain or simple woven
fabrics.

WORKING
In a plain power loom, the warp sheets are released from the weaver's beam (Let off
mechanism) over the backrest, before passing through a drop wire (which can stop the loom if a
thread breaks) on their way to the heddles. The heddles separate into harnesses to create a shed
(opening) for the weft yarn (Shedding Mechanism). The shuttle is pushed into the warp shed by
a picker (Picking mechanism). The warp threads then pass through a reed which spaces them
evenly and beats up the newly inserted weft yarn to create the fabric's density (Beat-up
mechanism). The fabric then travels over a fell of the cloth, guided by temples to maintain its
width, before reaching a front rest. Finally, a take-up or emery roller pulls the finished cloth and
winds it onto the cloth roller (Take-up mechanism).

1. Weaver's Beam:

• Function: Holds the warp threads in a parallel and tensioned manner.

• Source: The warp threads come from the sizing process (for grey cloth) or from sectional
warping process (For stripe/checked design).

2. Drop Wire (Warp Stop Motion):

• Function: Detects breaks in any of the warp threads.

• Purpose: Stops the loom automatically when a warp thread breaks.
• Mechanism: Each warp thread passes over a drop wire. If a thread breaks, the
corresponding wire drops, triggering the machine to stop.

3. Heald Shafts:

• Function: Divide the warp threads into two layers (shed) to allow the weft yarn to pass
through.
 • Components:
o Heald frames: Upright frames that hold the heald shafts in position.
o Heald eyes (mail eyes): Loops or holes in the heald shafts through which warp
threads pass.
o Lifting mechanism: Connected to a Tappet or Dobby or Jacquard mechanism that
controls the movement of the heald shafts to create the weaving shed.

4. Reed:

• Function: Spaces and aligns the warp threads evenly and beats the weft yarn into place.
• Components:
o Reed frame: Holds the reed dents in place.
o Reed dents: A series of thin, flat metal strips with narrow spaces between them.
o Beating mechanism: Connected to the crank shaft and drives the reed forward to
beat the weft yarn.

5. Race Board:

• Function: Supports the reed and guides it during its movement.

6. Sley Sword:

• Function: Connects the reed to the sley (beating mechanism).

• Purpose: Transfers the beating motion from the crank shaft to the reed.

7. Fell of the Cloth:

• Function: Refers to the area where the weft yarn is beaten into the warp threads, creating
the woven fabric.

8. Front Rest:

• Function: Supports the woven fabric as it exits the loom.

• Location: Positioned in front of the take-up roller.

9. Take-up Roller (Emery Roller - Optional):

• Function: Winds the woven fabric onto the cloth roller, maintaining tension and creating
a uniform roll.
o Emery roller: May have a slightly abrasive surface to help grip the fabric during
take-up.

10. Nip Roller:

• Function: Applies additional pressure to the fabric with the take-up roller for smoother
winding.

11. Cloth Roller:

• Function: The final destination where the woven fabric is collected as a continuous roll.
TAPPET SHEDDING MECHANISM

Tappet shedding mechanism is the simplest shedding mechanism using cams and tappets to
form ‘shed’ that provide the room for passage of shuttle.

There are two types of Shedding

1. Negative Tappet Shedding:

A shedding mechanism where a tappet presses a treadle lever, but only controls the lowering of
one heald shaft (group of warp threads). The other heald shaft is raised by a separate mechanism,
often using a reversing roller and strap system.

2. Positive Tappet Shedding:

A shedding mechanism where a tappet directly raises and lowers heald shafts (groups of warp
threads) through bowls or levers connected to the tappet and heald shafts. The tappet actively
controls both the up and down movement of the heald shafts.

WORKING OF NEGATIVE TAPPET SHEDDING MECHANISM WITH A LINE DIAGRAM

Working Principle
In negative tappet shedding, the tappet mechanism primarily controls the lowering of heald
shafts. The raising of the other heald shaft is accomplished by a separate mechanism, often
involving reversing rollers and leather straps.

Components

• Bottom Shaft: This shaft carries the tappets and rotates continuously.
• Tappets: These are cams mounted on the bottom shaft, with their profiles designed to
depress treadle levers at specific intervals.
• Treadle Levers: These connect the tappets to the lamb rods.
• Lamb Rods: These connect the treadle levers to the heald shafts.
• Heald Shafts: These hold the heald frames and control the raising and lowering of warp
threads.
• Reversing Rollers: These are used to raise one heald shaft while the other is lowered by
the tappet.
• Leather Straps: These connect the reversing rollers to the heald shafts.

Working Process

1. Rotation of Bottom Shaft: The bottom shaft rotates continuously, driving the tappets.
2. Tappet Depression: As the tappets rotate, they depress the corresponding treadle
levers.
3. Treadle Lever Movement: The depressed treadle lever moves downwards, pulling the
connected lamb rod down.
4. Heald Shaft Lowering: The lamb rod is connected to one heald shaft, causing it to
lower.
5. Reversing Roller Action: Simultaneously, the other heald shaft is raised by the
reversing roller mechanism.
6. Shed Formation: The lowered heald shaft forms the bottom layer of the shed, while the
raised heald shaft forms the top layer.
7. Weft Insertion: The shuttle passes through the formed shed, inserting the weft yarn