Carding.—This is one of the most important processes in cotton-spinning. The object of those preceding it has been to cleanse the raw material from gross impurities, such as leaf, seed, sand, dust, and heavier objects, that may accidentally or otherwise be introduced. Carding is the final stage of cleansing. As far as the carding-engine is capable of accomplishing it, all short, tangled, and " neppy " fibre is removed in this operation. To make clean yarn, cotton should be selected free from immature seed, which the gin often fails to remove, owing to dcfective seeds being so small as to pass ite blades, and get drawn in by the short and imperfectly developed fibre that covers them. Neither opening nor scutching abstracts them completely, and those that escape pass ioto the card, and are broken up. The particles are carried through the succeeding operations without being markedly visible, until the spinning is reached, when the twining brings them to the surface of the thread, where a great proportion are retained by the adhering fibres. In other respects, the cleansing funotion of the machine is very efficient.
In carding, the construction of the thread is cornmenced. TJp to this point, there has been no effort to arrange the fibres in any given order. Here the attempt is first made to place them pezallel. The thick sheet of cotton composing the lap is reduced to a thin cloud-like film, which is drawn through a cone tube, and condensed into a " sliver," a round, soft, and untwisted strand of cotton.
Tbe carding-engine is the machine by which this is accomplished. Some difference of opinion exists amongst practical men as to the best principles of construction, and in consequence there are several forms of the machine. Good arguments can be adduced in favour of each, and probably the diverse opinions that exist originated in dealing with different classes of raw material, and genii:1g various results.
To trace the development of the card would be interesting, but would need a volume for its elucidation. All that is necessary is to describe representative forms as now in use. Of these, there are three :—the roller, the Wellman, and the revolving flat card.
A section of the roller card, with a portion of the side, is shown in Fig. 532. Its chief parts are the following :—A, main cyb'nder or swift, which has a surface speed of about 1600 ft. a minute ; the roller B is termed the " licker-in," from its function of taking the cotton from the feed-roller C, and delivering it to the swift. The small cylinder D is the doffer ; E, the coiler ; F, the can in whioh the sliver is coiled ; and G, the lap, resting upon G', the lap-roller. Arranged over the main cylinder, are a number of small rollers, r and s. The former are carding rollers or " workers " ; the latter are " strippers" or " clearers." The cylinder, licker-in, doffer, workers, and clearers,
have their surfaces covered with " cards," the fineness 'of which is varied according to the class of work to be performed.
Cards are composed of small bits of wire, inserted at au angle, into a foundation of leather, cloth, or a oomposite material wbich inoludes a layer of indiarubber. They are usually made in the form termed " filleting "—a strip about in. wide, which is carefully wound in a spiral manner upon the cylinders and rollers. Sometimes they are made in what are termed " sheets." Fig. 533 shows the first card with which the cotton comes into contact, that clothing the " lieker-iu " roller. The card for this roller is pufposely composed of strong wire, of short cut. The kind now generally employed is flattened, and cut diagonally at the required angle. It is extremely strong, and by its action, without injury to itself, will destroy any foreign matter that may be likely to come from the lap, and which, if it passed this point, would subsequently injure the fine clothing of the cylinder and rollers. Thia apecimen showa the fineneaa required for uae in the longer ataples of cotton. Fig. 534 exhibits the card uaed for clothing the main cylinder, when fine cottons are used ; its count or degree of fineness is 100.a. No. 80'a lensed for low cottons, making coarse yarns ; 90'a, for general purposes ; and 100's, for fine work. The clothing upon the doffer cylinder is nearly always 20 counta finer than that upon the main cylinder. The dirt-roller card, Fig. 535, ia of a coarae vvire openly aet, eo that it may readily receive into the interstices the motes, seed, leaf, or other description of refuae, lying upon the aurface of the main cylinder. Ita cut is aimilar in depth to that of the " licker-in" roller. The carding rollera, or "workers" and " clearers," are both covered with cards of the same fineness', or neszly so, aa the main cylinder. The curved form of t,he illustra tions shows the cards as when actually ready for work.
Good carding very greatly depends upon the careful adjustment of all the rollers to the surface of the cylinder, the cards of which, while aet closely and evenly, ehould at no point touch each other. The rollers and clearera, in order to admit of this being done with the utmost nicety, are mounted upon two flexible " bends," very accurately turned, and fitted to the aides of the frame. The main cylinder, and all the rollers, are now usually composed of iron, which ia leas susceptible to the influence of damp or dty atmospheres than wood, the material formerly used. The beariuga should be made of the moat durable metal, and be kept carefully oiled. Every part should be set to work without oscillation, which, if permitted, soon rendera good work impossible.