Modern Cotton Spinning Machinery, Its Principles and Construction

by Joseph Nasmith

CHAPTER VII.
CARD CLOTHING, GRINDING, AND STRIPPING.

(154) As was shown in the preceding chapter, the cylinder, doffer rollers, &c., of carding engines are covered with a wire clothing, the proper construction of which is of high importance. It forms a sort of wire brush, in which the points are fixed in a special matrix, or “foundation,” as it is called. Formerly it was the universal practice to make the foundation of leather, but various considerations have led to its abandonment, except in the case of woollen cards where an oily or greasy material requires dealing with. In lieu of leather three specially prepared materials are now employed, one being what is called a cotton-wool-cotton, another cotton, and the third a natural rubber foundation. The first of these consists of two thicknesses of cotton cloth specially woven with a wool fabric cemented between them. The rubber foundation consists of a thin sheet of natural india-rubber imposed upon and securely cemented to a back of cotton and wool. Great care is taken that the india-rubber shall be pure, and in some cases the manufacturers of card clothing also produce their rubber sheets. The object aimed at in each case is to obtain a foundation which shall be strong enough to hold the wires securely, and at the same time be possessed of some elasticity, so as to aid the wires to recover their position when bent during work.

(155) It was at one time the practice to make the cards in sheets four inches wide, and long enough to cover the width of the machine, but this has been abandoned in favour of a plan by which they are made in long strips or “fillets.” These are long enough to completely cover the cylinder, on which they are wound in a way which will be hereafter described. Having obtained the fillet for the foundation, the next step is to introduce the wires. These are produced from a reel of specially drawn steel wire, which is frequently hardened and tempered by a continuous process. It is essential in conducting the latter that the wire should be free from scale, and, in the great majority of cases, this is attained. In fixing the wires into the foundation the preliminary step is to cut off from the wire carried on a reel a sufficient length, and bend it up into the form of a right angled staple, having two parallel arms joined by the third side. The extremities of these arms constitute two of the points to be fixed in the foundation, so that it will be seen these are always introduced in pairs, and not singly. In order to facilitate their passage through the foundation, two holes, pitched to correspond with the distance of the two points apart, are pierced in it, and immediately on the withdrawal of the piercer the staple is pushed in, and forced up to its place. Almost simultaneously with this operation it is set—that is, is bent to an angle as shown in Fig. [85]. After one pair of wire points are fixed the fillet is traversed, so as to introduce another pair at the required distance from the last one. When the width of the fillet has been filled with teeth it is moved a little lengthways, far enough to begin the next line, and the direction of the carriage is reversed. It is highly important that the wire points should be set equidistant over the whole of the surface, so that when the cylinder is clothed, the regularity of the carding points will be unvarying. The whole of the operations of feeding, cutting, and bending the wire, piercing the fillet, forcing in the teeth, traversing and reversing the carriage, and traversing the fillet longitudinally, are automatically performed by a machine of great ingenuity, originally invented by Mr. J. C. Dyer. It is one of the best examples in the whole range of mechanics of the power of the cam, and works with great rapidity, being capable of fixing over 300 pairs of wire points per minute.

Fig. 76.

(156) The teeth can be set in the foundation in three ways—either plain, twilled, or ribbed, these settings being shown in Fig. [76], the dots representing the wire points, the back of the teeth being shown by the dotted lines. In the first case the teeth are in straight lines; in the second they are, as the name implies, set diagonally; while in the third they are in straight lines, but set so that they are in sets of three, each of which overlaps its predecessor. Generally, plain setting is very little used, fillets being commonly made ribbed, except in the case of the flat covering, which, when mild steel wire is employed, is usually twilled. In manufacturing cards for covering the flats it is common to commence with a large sheet equal in width to the length of the flat. The teeth are then set for a space equal to the width of the flat, when the sheet is rapidly traversed longitudinally until the point for starting a new flat strip is reached. These strips are cut out of the sheet, and thus leave the necessary margins for fastening to the flat. In America twilled setting is preferred, but, in this country, it is objected that spaces are left between each lap when fixed on the cylinder, which is very objectionable. This fault does not occur where ribbed fillets are used, and it is now almost the universal practice to use this setting for cylinder and doffing coverings. However the teeth are set in this respect, they vary also in their distance from each other, and this variation depends on the “counts” of the wire. This phrase is used to indicate the fineness of the pitch of the wire teeth, and the method of counting is based on the number of teeth in the width of the sheets formerly made. Thus, if there were 100 teeth in a sheet four inches wide, the counts were said to be 100’s, the same rule being applied to-day. Longitudinally, the pitch of the teeth was ten “crowns,” or points, to the inch, this being also retained as a standard of measurement. In this way it is possible, by knowing the counts of wire, to calculate easily the number of teeth per square inch. Thus, in the instance named, there would be 100 × 10 = 1,000 teeth in the four inches of width by one inch in length, which is equal to 250 teeth in every square inch.

Fig. 77.J.N.

(157) In clothing the various parts of the machine experience has shown that there can be wise variations made in the kind used. Every spinner has ideas of his own, and as there is a wide difference in the class of material treated no rule can be laid down. In clothing the licker-in, a tooth which is known as the “Garnett” is universally used. An illustration of this is given, in full size, in Fig. [77], the finer tooth shown being used when no undercasings are fitted, and the coarser when they are. It will be noticed that the former is a little more hooked than the latter, which enables it to carry round the cotton without flinging it below the licker-in. The presence of an undercasing obviates much of the necessity for this carrying power, and the tooth is only required to beat off the cotton from the lap and thus throw down the motes, etc. In covering the cylinders of roller carding engines, where medium counts of yarn are being spun, clothing with 90’s to 100’s wire is used, the rollers being covered with the same counts, the clearers with a finer wire, and the doffers from 100’s to 120’s. These, of course, are sizes which are commonly employed, and indicate the usual limits, but, as has been observed, practice varies considerably in this respect. In revolving flat carding engines the cylinders are covered with 110’s, and doffers and flats with 120’s for medium counts of yarn. It may be generally stated that the finer the counts of yarn spun, all other things being equal, the finer the wire clothing employed; but it can only be settled by practice what are the best counts to use in any individual case.

(158) As has been observed, the wires are, in the process of setting, bent to an angle, or, rather, a double angle, after leaving the foundation. A reference to Fig. [85] will show that they leave the foundation at an angle in one direction, and afterwards bend sharply in the opposite direction. The diagram given in Fig. [78] illustrates this construction. The foundation is shown by the letter D, to which the line A B is perpendicular, leaving the upper surface of D at E. The tooth is indicated by the line A C E B¹, and it will be noticed that the point of the tooth at A is perpendicular to the point E where it leaves the foundation. This is the correct setting, or nearly so, for the following reason. Some makers, it may be stated, prefer to let the point A be a little behind the perpendicular line A E. In working, the wire point is pressed by the material and is sprung backward, in which case it—when set as shown—will radiate round E and move in the circle shown by the letters F A G. Thus, if another set of wire points are imposed upon the lower ones, the flexure of the latter, in either direction, is followed by their recession from the former, and no danger exists of any interlocking, which, if it occurs, is injurious to both sets of teeth. As the relative positions of the upper and lower teeth are of the character described in the previous chapter, the adoption of the method of setting the teeth indicated is of considerable importance. It is, of course, possible to vary the angularity or “keen” as desired, and the more acute the angle E C A the more fibre caught and retained. Thus the proportion of waste made in a machine during work is largely dependent on the angular setting of the wires, and this is a point specially worth noting. The essential element is the approximate perpendicularity of the point A of the wire to that (E) where it leaves the foundation.