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: >>>>>>>>>>