Page 48 - Shawl Weaving Artisan - TT

Textile & Handloom Related Theory for Exercise 1.3.27
Shawl Weaving Artisan - Power Looms and Handlooms

Dobbies used in weaving

Objectives: At the end of this lesson you shall be able to
• describe dobbies used in weaving and their working mechanism.

Dobbies used in weaving, and their working The left-hand dobby is one placed at the right-hand side
mechanism (Fig 1): Dobby is a shedding device of the left-hand loom. The left-hand dobby gets its drive
attached to the loom to increase the design capacity. The from the right end of the loom.
dobby normally controls 12 to 24 hold shafts the dobbies Climax dobby: The Climax Dobby is a double-acting
are classified as negative or positive, single lift, double machine controlled from the bottom shaft, it forms the
lift, crank driven, cam driven, etc. open shade. The lifting of heald is done by the lifting of
The dobby forms a bottom closed, center closed, semi- jacks. The healds are lowered because of springs used
open, and open type of shed. The dobby is also classified on the bottom side. It has 2 jacks. Dobby runs at half the
as left hand and right hand. speed. In the right-hand dobby, the cylinder rotates in a
The right-hand dobby is placed at the left-hand side of clockwise direction. In the left-hand Dobby, the cylinder
the left hand. It gets driven from the left-hand end loom. rotates in an anticlockwise direction.

Working: Dobby gets its drive from the bottom shaft
through a connecting rod. The T-lever gets oscillation
and thereby knives move forward and backward in the
framing machine slot. When the knives are towards the
set of hooks selection of engagement hook and knife is
made feller. The feelers are activated because of wooden
pegs. when the hooks and knives are engaged, then the
hook is pulled, while the other hook and the lever rest
on the stop bar. now the heald is lifted up. Timing and setting of climax dobby (Fig 4)
Cycle of lifting of healed into climax dobby (Fig 2&3) 1 At 270 degrees The heald shaft is leveled, and knives
a The Healds shaft remains down no selection has are in the midway position.
taken place. knives K1 and K2 are about to move 2 The T- lever is horizontal. At 60 to 120 degrees is the
from extreme positions. dwell Period of the dobby.
b Heald is down and the hook is not engaged with the • Heald is stationery • Shed is open
knife on the second pick. 3 At 90 degrees, one arm of the t— lever is outside
c It represents the engagement of the hook and knives and another is inside.
are about to pull the hook to lift the shed.
d Heald is lifted up on the pick. 4 The bottom shaft is at the top or on the bottom center
e The heald is again lifted up on the next pick because At 120 To 360 degrees To 60 degrees is the change
of the engagement of hook and knife. period of the heald shaft.
38