Page 236 - Basic Principles of Textile Coloration

MACHINES FOR DYEING FABRIC 225

Several ropes of equal length (50–100 m) are usually dyed side by side, being
kept apart by pegs in a long rail below the fly roller. The hinged peg rail lifts if a
tangled rope arrives, automatically turning off the winch drive. Short lengths of
individual ropes require more sewing and more time to locate the seams for
unloading. There is an obvious advantage if one long, continuous spiral of rope
advances through the machine from one side to the other. It then returns to the
start by way of a sloping trough or tube filled with dye solution at the back of the
machine. In this case, a continuous helical metal spiral, whose pitch determines
the loop spacing, replaces the peg rail. This type of loading is more uniform and
allows a lower liquor-to-goods ratio.

12.4.2 Jig dyeing machines
The jig or jigger dyeing machine is one of the oldest types of machine for dyeing a
variety of materials in full width. It is particularly useful for fabrics such as satins
and taffetas that crease readily. The open-width fabric passes from one roller
through the dyebath at the bottom of the machine and then onto a driven take-up
roller on the other side. When all the fabric has passed through the bath, the
direction is reversed (Figure 12.4). Each passage is called an end. Dyeing always
involves an even number of ends.

The bath can be rapidly heated by live steam from an open perforated pipe, the
perforations pointing down and away from the fabric. Closed-coil steam heating is
slower but gives better temperature control during dyeing and avoids dilution of
the liquor. As in winch dyeing, the fabric moves through a stationary bath, which
is stirred only by the movement of the fabric through it. The bulk of the dyeing is
usually carried out with a constant bath temperature. In the widest machines,

Figure 12.4 Illustration of a typical jig dyeing machine (courtesy of MCS SpA)