Page 234 - Basic Principles of Textile Coloration

MACHINES FOR DYEING FABRIC 223
use of radio frequency dryers has become popular. As much water as possible is
removed by centrifuging and the packages then go into the RF dryer. The
oscillating electromagnetic field causes oscillation of the polar water molecules in
the package at the field frequency. This generates much heat. The degree of
heating depends on the amount of water at a given point in the package so that
drying is more uniform than in hot air. The power of the RF field is sufficiently
high that drying only takes a few hours.

12.4 MACHINES FOR DYEING FABRIC
12.4.1 Winch dyeing
The winch or beck dyeing machine is quite simple and serves for all scouring,
bleaching, dyeing, washing-off and softening processes. The machine contains a
length of fabric with the ends sewn together, which is compressed to form a
continuous rope. This rope passes from the dyebath over two elevated reels and
then falls back into the bath (Figure 12.3). The first roller is free-running (jockey
or fly roller). The second (winch reel) is driven and controls the rate of rope
transport and the extent of pleating where the rope accumulates below and behind
the winch. Both reels extend the full length of the machine and accommodate
several fabric ropes running side by side. The fabric rope is held on the winch by

Figure 12.3 Illustration of a winch dyeing machine with Autoloda