Take up motion:
The process of withdrawing fabric from the weaving zone at a constant rate and then winding the woven cloth on the cloth roller with the continuous progress of weaving is called take-up. Take-up is to draw a fabric to the cloth roller regularly as it is woven. In this article, we will know about the calculation of the 7-wheel take-up mechanism.
7-wheel take up mechanism:
The 7-wheel take-up mechanism is a typical take-up mechanism which is generally used in cotton weaving.
Construction and working principle:
- A = Rachet wheel = 24 T
- B = Standard wheel = 36 T
- C = Change wheel = XT
- D = Swing pinion = 24 T
- E = Compound wheel = 89 T
- F = Compound pinion = 15 T
- G = Take up wheel = 90 T
- H = Take up roller = 15.05″ (circum)
- K = Retaining catch
- L = Pawl
- M = Finger
- N = Take up lever
Take-up lever N is centered at ‘I’ and has a pawl L pivoted upon it
A finger M is bolted and adjustable to a sley sword and passed through a slot in N
A swing motion is given to N and this will cause the pawl L to drive the Rachet wheel A and wet the train of wheels in motion. The amount of movement in L depends upon the position of M in the slot of N
The cloth is wound onto the cloth roller, as the sley falls back or as the sley moves forward.
Calculation:
PPI calculation:
For one revolution of one tooth of Rachel wheel (A)
= 1 pick take-up
…………………………………………………G x E x C
Then, No. of revolution of A = 1 x ………………..
………………………………………………….F x D x B
……….90…….89………X
= 1 x …… x ……… x …..….
……….15……..24……..36
…………………………………………….90 89 X
No. of picks for 1 rev. of H = 1 x ….. x …… x ……. x 4
…………………………………………….15 24 36
…………………………….90 89 X 24
Picks per inch = 1 x …… x …… x …… x ……….
…………………………….15 24 36 15.05
………90 89 60 24
= 1 x …… x …… x ……. x ……….. [C=60]
……….15 24 36 15.05
= 59.13
Pick spacing:
Pick spacing is the reciprocal of the pick density
…………………………….1
i.e. pick spacing = ……..
…………………………..PPI
………………………….B D F H
Pick spacing = 1 x …… x …… x …… x ……..
………………………….C E G A
…..36 x 24 x 15 x 15.05″
= ………………………………
……..60 x 89 x 15 x 24
= 0.0169 inch
Or pick spacing = X = 0.0169 inch
Loom Constant:
To find out the loom constant, the no of teeth in a change wheel is always = 1 i.e X = 1
…………………G x E x C x A
PPI = 1 x ………………………….
………………F x D x B x 15.05
…………..90 x 89 x X x 24
= 1 x ………………………………
………..15 x 24 x 36 x 15.05
…………………………………90 x 89 x 1 x 24
Loom constant = 1 x ………………………………
………………………………15 x 24 x 36 x 15.05
= 0.9836
Hence, PPI = Loom constant x change wheel
= 0.9856 x 60
= 59.136
In the loom, the fabric remains under tension. When it is out of the loom, it becomes relaxed. So in a relaxed state lengthwise contraction of the fabric increases the PPI of fabric and normally contraction is 1.5%
………………………..G E C . .A .. 100 + 1.5
Hence, PPI = 1 x ….. x …… x …… x ………… X ……………..
………………………..F D B .15.05 . 100
……….90 89 60 .,.24
= 1 x ……. x ….. x …… x ……… x 1.015
……….15 24 36 15.05
= 60.02
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Author of this Article: Rofiquzzaman Raju Fabric Technologist, B.J.Group, Mawna, Gazipur Chittagong Textile Engineering College Contact: 01714419681