7. Low LR jet dyeing machines and aerodynamic jet dyeing machines

The necessary amount of dye liquor for complete immersion of the material for dyeing depends on the kind of material (weight, density and bulkiness etc.) and loading method, and without a mechanical squeezing system, the minimum LR may be 1:2.

However low LR jet dyeing cannot be achieved by a conventional dyeing machine immersing the fabric in the dyebath, and at least 1:4～1:8 is necessary even employing a sophisticated design. The lowest LR is generally 1:10 for jet dyeing machines with complete immersion of fabric.

If low LR dyeing is carried out using this machine at a LR =1:3～1:6, the fabric cannot be fully immersed in the retaining tub and a part of the fabric is left out of the dyebath (exposed) and the fabric is transferred through the steaming part bearing the dye liquor.

The newly developed low LR jet dyeing machine or aerodynamic jet dyeing machine is designed to dye under these conditions.

Figure 3 Low LR jet dyeing machines
Fully immersed Partly immersed		Advancing lower LR leads to increase of exposed part

In these machines, the effective area decreases leading to a decrease of levelness. However, level dyeing can be achieved if the decreased effective area can be compensated for by an increase of area exchange.