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Calculation of 7-Wheel Take Up Mechanism

Calculation of 7-Wheel Take Up Mechanism
Rofiquzzaman Raju
Fabric Technologist,
B.J.Group, Mawna, Gazipur
Chittagong Textile Engineering College
Contact: 01714419681



Take up motion:
The process of withdrawing fabric from 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.

7-wheel take up mechanism:
7-wheel take-up mechanism
Construction and working principle:

A = Rachet wheel = 24T
B = Standard wheel = 36T
C = Change wheel = XT
D = Swing pinion = 24T
E = Compound wheel = 89T
F = Compound pinion = 15T
G = Take up wheel = 90T
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:

1. PPI calculation:
For one revolution of one teeth 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

2. 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

3. Loom Constant:
To find out 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 loom, it becomes relaxed. So in relaxed state lengthwise contraction of fabric increases the PPI of fabric and normally contraction is of 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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