(148) Messrs. Howard and Bullough adopt a plan by which the pedestal is fitted upon two wedges, or inclined metallic surfaces, placed one above the other. By setting one or both of these wedges in either direction, the pedestal is so adjusted that the cylinder centre can be moved either laterally, vertically, or angularly, as is required. Another plan, adopted by Messrs. Ashworth Bros., consists of the formation on the pedestal of three projections, or claws. The inner surface of these is bored concentrically with the pedestal bearing, so that when the cylinder is in its true position, a cylindrical template, bored to correspond with the diameter of the shaft, and turned on its outer surface the same size as that to which the projections are bored, can be easily pushed up to the face of the pedestal. Unless this can be done the cylinder is not concentric, and the adjustment of the bearing must be made accordingly. Messrs. Dobson and Barlow employ the device shown in Fig. [73], which consists of two eccentric bushes, X Y, surrounding the bush in which the shaft Z revolves. The eccentricity of each of the bushes is equal, and thus by moving one or both the position of the centre of the cylinder can be adjusted at will, either laterally, vertically, or angularly. To facilitate the adjustment, two screwed rods, U V, are attached respectively to lugs formed on the bushes X Y, and pass through brackets formed on the pedestal. By means of nuts placed at each side of the brackets the adjustment of the position of the eccentric bushes can be made at will.
(149) In order to diminish the evil effects of the pull of the strap, as mentioned in paragraph 119, the plan shown in Fig. [74] has been adopted by Messrs. Ashworth Bros. Instead of keying the fast pulley on the shaft, it revolves on a hollow boss C, which has a flange or plate attached to the pedestal F. The pull of the strap on the fast pulley A is therefore taken by the bush or hollow boss C, and not by the shaft. Fixed on the shaft is a coupler D, which is formed with two arms engaging with corresponding recesses in the centre of the boss of the pulley A, something similar to the ordinary driver used in turning. By these means the shaft is rotated without there being any pull upon it, and one fruitful source of forward wear is thus removed.
(150) The three points which it is necessary to bear in mind in regard to carding were indicated at the opening of this chapter. These were the cleansing, parallelisation, and attenuation of the lap, and a few words may be said about each in that order. The velocity with which the teeth of the licker-in strike the end of the lap causes the fibres to be effectually loosened, and shakes a good many of the motes out of the cotton. Others are left on the surface of the fibres held by the licker-in wire, and are removed by the mote-knives as described, while some enter the spaces of the licker-in covering, from which they are easily thrown. On passing to the cylinder, the short fibres are largely thrown off as fly, or when they are subjected to the combing action of the wire teeth on the rollers or flats they are removed, and become fixed in the spaces in the covering. The “neps” are in a similar way taken out of the fleece, and from this cause periodical stripping is desirable of both rollers and flats. By reason of the centrifugal action of the cylinder many short and nepped fibres are driven into the roller or flat wire, but a certain proportion also remain in the cylinder wire, which also requires stripping periodically.
(151) It is somewhat difficult to define the exact action of the wire points by which the crossed and tangled fibres in the lap are laid in approximately parallel order. There is little doubt, however, that the speed of the cylinder plays an important part. The fibres are by the action of centrifugal force thrown out, so that, while held at one end by the cylinder wires, they are rapidly drawn through the wires on the rollers or flats. If the grip of the fibre is slight, as in the case of a short fibre, it will be removed, but, if it is sufficient to hold, it follows that the fibre would be combed by the superimposed wire teeth. In this way the thickness of the fleece on the cylinder plays an important part in determining the amount of parallelisation the fibre receives. If this is thin, each fibre, in all probability, receives its due treatment, while, if it is thick, the fibres are dragged—so to speak—through the wire teeth above, and would be likely to be injured, besides which their arrangement is more difficult. For this reason, the lighter the carding—that is, the less the weight of cotton passing at a given time—the better, provided that this is not pushed so far as to be uneconomical. It has been pointed out that the setting of the flats in the self-stripper lends itself peculiarly to effective combing, as the pitch of the wire teeth and the distance between them and the cylinder teeth can be gradually made finer. In the case of the roller card the fibres are lifted off the cylinder, and, if well held, would be drawn straight in the process. In their transfer by the clearer to the cylinder the fibres are further dealt with, but it is problematical whether the alternate raising and return of the fibres from and to the cylinder, results in a parallel order being obtained equal to that by other machines. A good result arises from the use of a roller card as a breaker, and a self-stripper as a finisher card, and this arrangement is often adopted.
Fig. 73.J.N.
Fig. 74.J.N.
(152) The attenuation of the lap is one of the most important functions of the carding engine, because it is the first stage in the formation of a thread, by reason of the easy condensation or collection of the thin film into a strand. Assuming that the feed roller is 21⁄2 inches in diameter and makes one revolution per minute, it will deliver 7·854 inches of lap. The licker-in being 8 inches in diameter, and revolving at a speed of 400 per minute, is capable of delivering 10053·12 inches. As it cannot get this length of lap, it follows that in its revolution the teeth remove a small portion of the cotton continuously, and thus produce a layer or fleece, which is increased in length and diminished in thickness. The ratio of this increase is that just given, being equal to 1,280 : 1. When the cotton is transferred to the cylinder a further reduction takes place. The cylinder, being 50 inches in diameter and revolving, say, 150 times per minute, is capable of delivering 23,562 inches of cotton, or 2·34 times as much as the licker-in. Thus, up to this stage, the lap is elongated 3,000 times, as compared to its thickness when passing the feed roller. If the lap is 1⁄40 inch thick the fleece on the cylinder, if spread out, will only be 1⁄120000 inch thick. It will be easily seen by a reference to the sizes of the cotton fibres that this is much thinner than the smallest diameter of individual fibres, and it follows, therefore, that if there was only this amount of cotton on the cylinder there would be many bare places. As the work of carding proceeds the cylinder becomes charged with cotton, but is never so full that the fibres cannot be carded thoroughly and individually, unless the rate of feed is excessive or largely increased. As the fleece is deposited on the doffer the reverse process occurs, as the doffer, being 24 inches diameter and revolving only 12 times per minute, would only deliver 904·78 inches, or 1⁄25th of that of the cylinder. Thus, the sliver, when collected, would be about 1⁄115th of the thickness of the lap. These figures are, of course, only approximations. As was previously shown in paragraph 112, the rollers and clearers in a roller card revolve at a much slower speed than the cylinder. The cotton is therefore subjected to a series of condensations and attenuations as it passes round the machine.
(153) An enlarged view of the sliver as it leaves the doffer is given in Fig. [75], and shows that the fibres, although not in parallel order, are arranged so that a slight additional pull is sufficient to straighten them. This the sliver receives partially between the calender rollers and the coiler, but it is in the drawing frame that the greatest effect is obtained. The draught there exercised speedily causes parallel order to be attained in the sliver, which is in good condition for this action. The draught in a carding engine takes place between the feed rollers and licker-in, between the licker-in and cylinder, and between the calender rollers and coiler, the total draught being reckoned between the feed roller and coiler. The question as to the speed of the doffer turns upon the amount of condensation required and the weight it is desired to get through the machine. There is a distinct relation between the speed of the cylinder and that of the doffer, but it has never yet been practically fixed, and carders vary in their speeds considerably.