(192) The carded slivers intended for use in the combing machine are first treated by a special set of machines, the object of which is to draw the fibres into an approximately parallel condition. It was remarked in paragraph 153 that, although the fibres in the sliver as it left the carding engine were in a more or less crossed condition, they were so openly laid that a slight endwise pull would draw them into a practically parallel order. In spinning ordinary yarns this is done by the drawing frames, which are described in the next chapter. Although the sliver eventually delivered from the combing machine is also drawn, it has been found desirable to commence this action before combing commences, and the result is that a sliver is produced which is exceptionally even and strong. The exact operation of drawing will not at this juncture be described, as it will be necessary to go over the same ground at a later stage.
(193) The first machine by which the slivers are treated is known as the Sliver Lap Machine, and as made by Messrs. Dobson and Barlow, is shown in perspective in Fig. 112. It consists essentially of drawing rollers, to the action of which the slivers are fed from the cans. From 12 to 16 slivers are treated at one time, and on their way from the guide plate to the rollers, they pass over the spoons formed at the ends of detector levers, this part of the mechanism being clearly shown. The failure of any one of the slivers causes the machine to be stopped as in the drawing frame, so that any unevenness in the lap is avoided. The slivers in passing the drawing rollers are laid side by side, and are in this way flattened, so that when they are delivered by the rollers, they have assumed the form of a ribbon, which is rolled up into a lap, by means of a specially driven roller. This treatment straightens the fibres, and prepares them for further treatment.
(194) This is given on the Ribbon Lap Machine, which is illustrated in Fig. 113. The laps obtained in previous machines are to the number of six, placed behind the drawing rollers in the machine. Four lines of rollers are provided, as in the drawing machine, and the laps are thus reduced in thickness until they become like a thin ribbon. By this time the various fibres of cotton are pulled into parallel order, and are in a good condition for combing. They are respectively guided round the curved plates shown, and are laid flat upon a highly polished iron plate. The lap which is delivered at the end of the machine furthest from the driving head is laid upon the plate first, and all the others are subsequently imposed upon it. The combined six laps are then passed through a pair of calender rollers at the end of the machine, by which they are compressed, and the combined lap is subsequently wound into rolls of 7-1/2 or 8-1/2 inches wide. These rolls or laps are fed to the combing machine. The chief advantages of this arrangement are those arising from the parallel order of the fibres. These are evenly laid in an uncrossed state, and there is consequently little danger of any rupture of them by the comb teeth. Further, the latter are not strained in the effort to disentangle the fibres, and a fruitful source of breakage is thus avoided. There is another point, to which special reference was made in Chapter V., namely, the equalisation of the thickness arising from the imposition of the laps upon each other.