Experiment name : Study on let off
mechanism of tappet loom.
Introduction: The motion which delivers the
warp yarns from the warp beam at the required rate that a suitable constant
tension by unwinding it from a flanged bobbin called let off motion.
Types of let off motion:
- Positive let off motion.
- Negative let off motion.
Objective:
- To learn about let off mechanism.
- To Calculate PPI.
- To write a report according to this experiment.
Related machine parts:
- Sley sword
- Key
- Connecting rod
- Let off lever
- Hook rod
- Side lever
- Cam
- Back rest
- Dead weight side lever
- Pushing pawl
- Ratchet wheel
- Gear:
a.
Warm gear.
b.
Bevel gear.
c.
Helical gear.
- Beam driving wheel
- Beam flange
- Weaver beam
Figure:
Construction of the mechanism:
1.
A driving rod attached with
sley sword contains pushing pawl. Which may adjusted by hook rod which one
connected with lever and back rest.
2.
Pushing pawl push the ratchet
wheel which connected with one set of bevel gear.
3.
Bevel gear transfer motion by a
complex gearing method.
Working principle:
1.
The ratchet wheel received
motion from the pushing pawl which push the ratchet wheel with every beat up.
2.
A Bevel gear achieved motion
from ratchet wheel and transfer it to worm gear.
3.
Worm gear transfer motion to
helical gear which transfer motion to beam driving wheel.
Calculation:
PPI
= (116 X 17 X 37 X 10) /
(23 X 1 X 25 X 23)
=
55.17 PPI
Pick spacing = 1/
55.17 = 0.01812 inch/pick
Conclusion:
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