Klauder-Weldon Hank-dyeing Machine.--This is illustrated in figure 15, which shows the latest form. It consists of a half-cylindrical dye-vat built of wood. On a central axis is built two discs or rod carriers, which can revolve in the dye-vat, the revolution being given by suitable gearing which is shown at the side of the machine. On the outer edge of the discs are clips for carrying rods on which one end of the hanks of yarn is hung, while the other end is placed on a similar rod carrier near the axle. The revolution of the discs carries the yarn through the dye-liquor contained in the lower semi-cylindrical part of the machine previously alluded to. At a certain point in every revolution of the discs the rods carrying the yarns are turned a little; this causes the yarn to move on the rods, and this motion helps to bring about greater evenness of dyeing. The most modern form of this machine is provided with an arrangement by means of which the whole batch of yarn can be lifted out of the dye-liquor. Arrangements are made by which from time to time fresh quantities of dyes can be added if required to bring up the dyed yarn to any desired shade. This machine works well and gives good results. Beyond the necessary labour in charging and discharging, and a little attention from time to time as the operation proceeds, to see if the dyeing is coming up to shade, the machine requires little attention.
Many other forms of hank-dyeing machine have been devised. There is Corron's, in which an ordinary rectangular dye-vat is used. Round this is a framework which carries a lifting and falling arrangement that travels to and fro along the vat. The hanks of yarn are hung on rods of a special construction designed to open them out in a manner as nearly approaching hand work as is possible. The machine works in this way. The lifting arrangement is at one end of the vat, the hanks are hung on the rods and placed in the vat. Then the lifter is set in motion and moves along the vat; as it does so it lifts up each rod full of yarn, turns it over, opening out the yarn in so doing, then it drops it again in the vat. When it has travelled to the end of the vat it returns, packing up the rods of yarn in so doing, and this motion is kept up until the dyeing is completed. This machine is very ingenious.
A type of machine which has been made by several makers consists of an ordinary rectangular dye-vat surrounded with a framework carrying a number of sets of endless chains, the links of which carry fingers. The hanks of yarn are hung on rods at one end of which is a tooth wheel that when in position fits into a rack on the side of the vat. The action of the machine is this, the hanks are hung on the rods and placed at the entrance end of the vat, by the moving of the chains it is carried along the vat and at the same time revolves, thus turning over the yarn, which hangs in the dye-liquor; when it reaches the opposite end of the vat, the rod full of yarn is lifted out, carried upwards and then towards the other end of the vat when it is again dropped into the dye-vat to go through the same cycle of movements which is continued until the yarn is properly dyed.
Piece Dyeing Machines.--Wherever it is possible it is far more preferable to dye textile fabrics in the form of woven pieces rather than in the yarn from which they are woven. During the process of weaving it is quite impossible to avoid the material getting dirty and somewhat greasy, and the operations of scouring necessary to remove this dirt and grease has an impairing action on the colour if dyed yarns have been used in weaving it. This is avoided when the pieces are woven first and dyed afterwards, and this can always be done when the cloths are dyed in one colour only. Of course when the goods are fancy goods containing several colours they have to be woven from dyed yarns.
The most common form of machine in which pieces are dyed is the jigger, commonly called the jig, this is shown in figure 16. It consists of a dye-vessel made long, sufficiently so to take the piece full width, wide at the top, narrow at the bottom. At the top on each side is placed a large winding roller on which the cloth is wound. At the bottom of the jig is placed a guide roller round which passes the cloth. In some makes of jigs there are two guide rollers at the bottom and one at the top as shown in the illustration, so that the cloth passes several times through the dye-liquor. In working the cloth is first wound on one of the rollers then threaded through the guide rollers and attached to the other winding roller. When this is done dye-liquor is run into the jig, and the gearing set in motion, and the cloth wound from the full on to the empty roller. With the object of keeping the piece tight a heavy press roller is arranged to bear on the cloth on the full roller. When all the cloth has passed from one roller to the other it is said to have been given "one end". The direction of motion is now changed and the cloth sent in the opposite direction through the jig and the piece has now received another "end". This alternation from one roller to the other is continued as long as is deemed necessary, much depending on the depth of colour which is being dyed, some pale shades may only take two or three ends, deeper shades may take more. When dyeing wool with acid colours which are all absorbed from the dye-liquor, or the bath is exhausted, it is a good plan to run the pieces several ends so as to ensure thorough fixation of the dye on the cloth.
It is not advisable in working these jigs to add the whole of the dye to the liquor at the commencement, but only a part of it, then when one end is given another portion of the dye may be added, such portions being always in the form of solution. Adding dyes in powder form inevitably leads to the production of colour specks on the finished goods. The reason for thus adding the dye-stuff in portions is that with some dyes the affinity for the fibre is so great that if all were added at once it would be absorbed before the cloth had been given one end, and, further, the cloth would be very deep at the front end while it would shade off to no colour at the other end. By adding the dye in portions this difficulty is overcome and more level shades are obtained, but it is met with in all cases of jigger dyeing. It is most common in dyeing wool with basic dyes like Magenta, Auramine, Methyl Violet or Brilliant Green, and with acid dyes like Acid Green, Formyl Violets, Azo Scarlet or Acid Yellow.