Numerous improvements have since been made in the wool-combing machines, but all have been based upon the inventions of Heilmann and Lister & Donisthorpe. It is unnecessary to trace these further, as the principle will be thoroughly understood from what has already been stated. Fig. 1469 is a perspective view of a wool-comber which is highly eateeraed in the trade.
The introduction of mechanical combing has been a main cause of the great development of the worsted trade. as a single machine will comb a greater quantity of wool than 100 men could do by hand, and that in so much better a manner in every respect as to make it exceed the hand procesa as much in quality as it does in quantity.
Drawing.—The process of drawing is partly intended to complete or perfect that of combing, namely to secure the parallel arrangement of the fibres of the wool, and to take from them their wavelet or undu lating form, and, by elongating the fibres in that man ner, to secure the greatest length. This is accom plished by the ap plication of heat in the drawing pro cesses, The sliver is also attenuated and reduced to fit it for the spinning process.
The " set" of drawing machi nery usually con sists of 6 franles or screw-gills. The screw-gill draw ing-frame is com posed of an iron reservoir or steam chamber placed in advance of the feed-rollers, the latter of which deliver the sliver to a series of gill bars which travel from the feed-rollers in the grooves of two screws laid parallel to each other. These gill-bars are furnished with two or three rows of plus. When they have arrived at the end of their traverse, they drop into the grooves of two other parallel screws arranged below the first pair for their reception, and by which they are carried on their return to a point below that from which they started, when they ar, elevat LI into the first position by the action of two cams, ocie en each screw. The ecrew-gill drawing-frame being fully described in the article (see pp. 1180-1) on Jute Manufactures, the reader is referreAl thereto for fuller particulars. The differences are in points et detail merely, occasioned by the respective natures of the material they are constructed to work. The steam-chamber is ono of these.
As soon as the slivers leave the combing-machine, a given number, say about 16, are placed upon food-tahle and divided into two seta, each of which is passed first over the heated chamber by which the slivers are softened and better adapted for the drawing process, then through two seta of coarsely-fluted rollers which serve as feed-rollers. Aa the wool is delivered from these, the gill
bars rise, and the pins entering it conduct the rnaterial to the drawing-rollers. These rollers move with a velocity considerably greater than the feed-rollers, say 5-6 times or more, taking the wool from the latter in an even and regular manlier ; and attenuating the combined slivers from their original volume by its many times as the drawing-rollers exceed the feed-rollers in surface velocity. The several drawings are passed into 11 coiling-can, by which they are loosely twisted into one. Eight of these drawings aro next passed through the second frame, and elongated in the same manner, the process being repeated a third time. Iu the fourth passage through it similar machine, the material ie received and wound upon two bobbins, carried upon two large spindles, having large fliers, by which the drawing is slightly spun or twisted, after which it is called a " dubbing." In the fifth frame, the travelling gills are replaced hy four sets of rollers, through which the wool le passed, 16 slubbinge being arranged in seta of 4, each set being,' further attenuated, slightly twisted, and wound upon four bobbins. The sixth is the last and finishing process of drawing. In this, three of the slubbings from the last frame are ag,ain attenuated, twisted slightly, and wound upon bobbins as before.
The set of drawing-frames thus consists of 4 gill-boxes, the last of which delivers its material in spindles, and two roller drawing-frames, which receive it in the same manner.
Boving.—The " slubbing," having been sufficiently prepared, is ready for the roving process. This is simply a further attenuation of the coarse and loosely-twisted strand of wool to fit it for spinning. In this set, there are again machines, all alike in priuciple, each doubling and delivering the preparation finer than its predecessor. A slight twist is imparted iu each case to secure cohesion. After having passed these machines, the roving is sufficiently reduced, sad yet possesses strength enough to pass into the next atsge without parting asunder.