Chapter IX.

Chapter IX.Making Warps for Elastic Fabrics—Quills for Use in Shuttles—Effect of Finishing Processes Must Be Calculated from Beginning of Web Construction—Details of Processes and Machines for Different Styles of Goods—Care to Avoid Acid in Goods—Rubber’s Reaction on Copper

Making Warps for Elastic Fabrics—Quills for Use in Shuttles—Effect of Finishing Processes Must Be Calculated from Beginning of Web Construction—Details of Processes and Machines for Different Styles of Goods—Care to Avoid Acid in Goods—Rubber’s Reaction on Copper

The making of cotton warps for elastic fabrics, particularly for double cloth webs, involves considerable thought and care in view of the number of sections necessary for a properly constructed fabric, and the different weaves employed. Owing to the contraction of the rubber, it is essential at all times that the proper balance be maintained between the face and the back of the goods.

This necessitates a uniform weight of stock where the weaves on the face and the back are identical, no matter how the size of the yarns used may vary, and a variable weight of stock where the weaves are different. All this is determined by experimental work when establishing the grade. These conditions necessitate separate warps for the face and back. Then again the different weaves employed involve a variable length in the take-up and this alone would make it impracticable to combine the various weaves.

It is invariably the plan to use fine stock for the face and a coarser material for the back. Of course it would not be practical to put these together on the same beam. The crowded condition of material used necessitates the further splitting of the face and back sections. The binder, which takes up so much faster than any of the other yarns, also requires a special warp.

The general appearance of the finished product being so dependent upon the character of the selvage, it is advisable to have these threads under special control, so that they may be treated in the best possible manner to produce a satisfactory shed, and allow the filling to get a good clearance. So as to secure a smooth well-rounded edge it is therefore necessary to have this on a special beam.

It will be seen, therefore, that in an ordinary piece of double cloth elastic web there will be required at least five warps: back, face, binder, edge and gut. Figures and fancy effects will often necessitate auxiliary warps. With very fine webs, having six threads to a cord, it is often found necessary further to split up the face to obtain proper working conditions. Figs. 1 and 1A show a six-cord web, together with warp calculations for the goods.

The employment of so many warps to each strip of web, which are automatically delivered by the friction let-off levers described in a previous article, prohibits the use of warps where the threads are equally distributed across the beam, as is the practice in wide fabrics, the method usually being to tape them on the beams.

The required spools for the number of threads in the warp are put in a creel, each thread passing under an electrically connected wire, which is held out of contact by the running thread while the warp is making. Ifthe thread should break, the wire would drop and make an electrical connection which would automatically stop the machine. Fig. 2 shows a view of a warping machine such as is used for this work. They are generally constructed so as to allow for two or four beams, all of which may be run together or started, stopped or run individually, as required.

Fig. 1.—Six-Cord Web

Fig. 1A.—Harness and Chain Draft for Fig. 1

Each beam is friction driven so that a uniform speed is obtained in the delivery of the yarn from the spools. Beams are also so arranged that they will stop automatically on reaching a given size. Each warp thread is passed through a pair of reeds, fitted with dead stops in the center of alternating dent spaces, so that leases may be put in the warps at fixed intervals to assist in keeping them straight in the looms.

In taping the warps on the beams, it is customary in some mills to run the threads over a small steel flanged pulley about one and one-half inches wide, which will keep each thread in its proper position and make the tape absolutely straight and flat as it leads to the beam. A perfect fabric is largely dependent upon how well the warps have been made, but it must not be forgotten that a good warp may be spoiled by a poor beam.

Beam flanges should not lie flat against the warp creel standards, but should be kept clear by the formation of the head near the barrel, which should have enough prominence at this point to keep the flanges clear, and thus reduce the friction to a minimum. The edges of the flanges should be perfectly smooth so as to allow for uniform delivery by the contact lever. Much of the beam abuse which occurs in many mills might be avoided by provision being made for beam racks at convenient points.

Fig. 2.—Warping Machine

The making of proper quills for use in the shuttle is of no small importance, for on this the evenness and uniformity of the selvage very much depends. When flanged wood quills are used, the guides should be carefully adjusted so that the filling is uniformly spread over the entire length of the quill, allowing for perfect freedom at each end without dragging. Quills should not be overloaded. In drum pressure quilling, the automatic stop should be so arranged that the quill will be filled even with the outer edge of the flanges and no more.

Should there be any tendency to hardness in the material used for filling, it may be found advisable to run the thread over a plush pad on which has been applied a light application of cocoanut oil, but great care should be exercised not to overdo this as there is nothing so hurtful to rubber goods as oil.

The quills should only be of sufficient length to allow for uniform delivery from the shuttle without dragging at the ends. To assist in this elongated shuttle eyes are preferable to round ones, so as to shorten the angle at which the filling leaves the quill when running from the extreme end. Thumb bits should be so adjusted that the delivery is uniform from start to finish. The quill flanges should not lie flat against the sides of the quill opening, but should be pointed at the ends so as to reduce the friction. Quill wires should be of hard tempered steel and be perfectly straight at all times. When it becomes necessary to run narrow goods in wide spaces, recoil springs should be provided to gather up the loose filling.

The finishing of elastic fabrics is a process which demands great care, and has to be taken into calculation from the beginning of the web construction. Calculations must always be made as to what effect heat, moisture and sizing will have upon the covered up elastic threads, confined as they are in a multiple of small cavities and under high tension. As soon as the softening influence of heat and steam operate upon the covering of cotton yarn which confines these threads, the rubber strands begin to assert themselves and contraction at once takes place. To what extent this can go must be predetermined in fixing values, and a certain degree of uniformity of contraction arranged for.

Webs which are perfectly flat and straight when taken from the looms are liable to be transformed into unshapely products and completely ruined by unsuitable finishing. For instance, take a web with a twill center and a plain border which is apparently flat and satisfactory at the loom. The effect of heat and steam upon such a web will be to contract the soft woven center more than the harder woven plain border, which will cause the web to be long-sided and curl. Such a condition must be anticipated in the construction of the web and provision made to offset its occurrence. Sometimes it must be met by a change in the size of some of the yarns used, or number of threads employed at given points, or perhaps added gut threads must be introduced to stop contraction in certain places. It must always be remembered that we are dealing with a very much alive element when we are finishing rubber goods, and that unexpected results may at any time arise.

Finishing machines vary both in design and capacity, but the general principle is the same in all. A series of drying cans are arranged for the application of the sizing mixture. Some machines are laid out horizontally and some are upright. In the longitudinal layout the machines are more easily accessible in their different parts and under better control, while the upright machines are more compact and occupy less floor space. Fig. 3 shows a horizontal machine of the latest type. It has a drying capacity of eleven cylinders, 24 inches wide, 36 inches in diameter, allowing for a web contact of about 100 feet. These cylinders are arranged in two decks so as to economize in floor space.

The goods first pass through a pair of independently driven circular brushes, fixed at the feed end of the machine, to clear them from lint and dirt before being steamed and dried. They next pass between two pairs of nip rolls between which are fixed the steaming and sizing attachments. The goods pass through dry high pressure steam which is confined in a steam chest. They pass into and out of this chest through slots underneath the cover. A trough carries the condensed steam away from the goods and prevents dripping, otherwise they would be spotted.

Fig. 3.—Narrow Fabric Finishing Machine

The steam pressure must be carefully controlled so as to get uniform shrinkage of the goods. The steaming process softens the cotton, and the rubber threads, which are under considerable tension, gradually creep up and contract the goods. The steaming also makes the web more absorbent and thus prepares it for the size bath, through which it is passed under submerged brass rollers. The size is kept at a uniform heat by steam heated copper coils. The web then passes through the second pair of nip rolls, which are worked under pressure so as to squeeze out the size before the web reaches the drying cans.

The first of the dry cans is usually covered with cloth, so as to absorb any size which may remain on the surface of the goods and allow it to penetrate by further softening. As the goods continue to pass over the hot cans a gradual process of contraction takes place. This contraction is provided for by a corresponding regulation of the speed of the cans. Intermediate expansion pulleys are provided for this purpose, so that the speed adjustments can readily be made to meet the requirements of different kinds of web.

The two pairs of front rubber nip rolls are likewise independently driven, so as to provide for the shrinkage which takes place at the steam box and size bath. At the delivery end of the machine the goods pass through a set of nip rolls which are belt-driven from cone pulleys, so as to be able to deliver the goods at the speed they leave the last drying cans. From these last nip rolls, which are fixed quite high, they drop into receiving cans or boxes.

Ten to twenty-five strips running side by side are finished at one time. Adjustable guides are provided at different places on the machines to keep the goods running in proper position. The speed of the machine is usually governed by a Reeves transmission, and the delivery of the goods ranges from 10 to 15 yards per minute, according to the requirements of finishing. Three inches per yard is generally allowed for shrinkage, but this again is determined by the goods. Neglect at any point in this process may so interfere with the calculated shrinkage that values and costs are materially changed.

New patterns and grades should be tested for shrinkage as soon as the goods come from the loom, as short lengths made in sample looms are not at all times reliable. Frequent tests are also advisable to see that original conditions are maintained, as changes made by heat, steam and speed are always liable to occur.

The immersing process is used mostly for single cloth garter webs. Double cloth webs having a warp pile on the face are sized on the back only. Exceptions are made on double cloth white webs used for the corset trade, which are bathed with a very light size and often tinted in this bathing process to the desired tone of white to match the cloths they are to be associated with. Where the goods are sized on the back only the effect of this has to be considered when they are constructed, and provision made to maintain a proper balance under such conditions.

In frilled webs the elastic portion only is sized, so as not to interfere in any way with the soft flutings of the frill. This is done by guiding each strip over narrow pulleys which are run through the size bath. The size accumulated on these pulleys is absorbed by the web passing over them.

The requirements of the trade are so varied, and the types of web so numerous, that no formula for size is suitable for general use. Care must be taken, however, to avoid any sizes containing acids. Results from the use of such preparations may seem excellent at the machine but later on, when the goods are made up and come in contact with metal parts, the metal is quickly tarnished, and the result may be heavy claims for damage.

It may be well to note here that the sulphur used in the process of vulcanizing the rubber has the effect of blackening the copper cans and the rolls over which the goods must pass. This can be effectively prevented by having the cans nickel plated, thus doing away with much risk of dirty goods, and of constant scourings and washing of the different parts.

Fig. 4.—Narrow Fabric Singer

Provision should be made for sufficient depth in the sizing pans so that they will hold a liberal supply of size. Replenishment should be made at regular intervals and the heat maintained at a uniform temperature to get satisfactory results. It is advisable to make provisions to travel the web over the top of the machine for a distance after immersion in the size bath, and before it strikes the hot cans, so as to allow for proper absorption of the size.

All these details are best worked out by experience. Webs are generally fed into the machine from racks after being properly wound up, and great care must be taken to avoid any variable tension on the webs when entering the machine.

On lisle webs, a process of gassing or singeing takes place prior to finishing for the purpose of removing any fuzz or fibre from the goods. Fig. 4 shows a gassing machine used for this purpose. It is run at a high rate of speed and several strips are gassed at once. When the machine is running the flames are close to the web, but upon the stopping of the machine the flames are carried away out of contact. In gassing white and colors, great care must be exercised to have the gas mixture correct and free from any carbonizing effect on the goods.

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