On the arrival of each bar at the end of the top screw f, it drops from its position, the slides being purposely cut short to allow of this, upon the two bottom screws f, into the threads of which, its bevilled extremities enter, as in the top screws. These screws are adjusted accurately, so as to receive the bars correctly. They are cut to the same hand as the top ones, but with a much quicker thread. They revolve in a direction opposite to those of the top, by which action, they carry back the bar to the position whence it started at the oppo site end of the frame. The thread of the bottom shafts terminates in a projecting cam g, by which the bar is lifted again into the top shafts, the gill-pine in its elevation penetrating the sliver in process of delivery by the retaining rollers : thus commencing its journey anew.
At the front of the machine, where the sliver is delivered by the gills, are two rollers; the lower one h being composed of steel, about 21 in. in diameter, and called the drawing-roller. The super incumbent one j is of cast iron, covered with leather, about 8 in. in diameter, and is called the pressing-roller. These rollers are pressed together by weighted levers, and revolve at a speed 6 or 7 times greater than that of the retaining-rollers c, or the movement of the travelling bare. The effect of this is that the sliver is seized by these rollers as the travelling bars drop from the top to the bottom screws, and drawn away from the pills of the gills, and that it is greatly attenuated, the gills which have not fallen retaining a sufficient bold of the sliver, and acting as a comb, holding the fibres back, and preventing them entering the rollers in a tangled state. After passing these, the sliver goes over a guide-plate between the delivery-rollers, and is again received into a can.
The above parts constitute one division of a drawing-frame. The travelling bar is 3 ft. long, and fixed upon it are 4 gills, which are 6 in. wide at the pins. Each set of bars and gills, with their complement of retaining-, drawing-, and delivery-rollers, form a carriage ; and frames are usually oomposed of two, three, or four of these carriages. In a drawing-frame of two carriages, containing four gills per carriage, there are eight sets of gills. Two slivers from the finisher-card are put up to each gill, the number of slivers required to supply such a frame therefore being 16. The card sliver being about 9i yd. to the lb., and the draught of the rollers as 6 to 1, with two slivers for each gill, the drawing-sliver as delivered from the rollers will be about 28} yd. to the lb. But as there
are still inequalities in the sliver, it is usual to double them after leaving the gills, by passing two of them together over one guide-plate, aud through the above-mentioned delivery-rollers into one sliver-can, as, in that form, they are more convenient for the second drawing, to which they are next conveyed. The sliver, having thus been doubled, is, at this stage, about 14 yd. to the lb.
The second drawing-frame is of similar construction to the first, the only differences being that the gill-pine are finer and more closely set, and that the slivers are delivered singly from the drawing- to the delivery-rollers, and thence to the cans. Two slivers having again been put up to each gill, and the draught being 6 to 1, the strand is here attenuated to a length of 42 yd. to the lb.
As in the case of almost every other textile fibre, the object of these preparatory processes is to clean, comb, and attenuate the fibres, so as to fit them for the last operation of spinning into a thread, of dimensions suitable for the purpose to which it is intended to be applied. The roving-frame is the next to receive the sliver, and its function is to further attenuate it, and deliver it in a form convenient for the next stage of treatment.
Roving.—In its chief parts, the roving-frame resembles the drawing-frame, the sliver-cans delivering their contents over a guide-plate to a set of three retaining-rollers, thence to the gills on the travelling bars, which carry it to the drawing-roller, between which and the presser, it passes to a flier-spindle, carrying a large bobbin, upon which the rove is wound, instead of, as in the preceding operations, being deposited in a can. Owing to the attenuation which the sliver has undergone, all the preceding parts of the machine are reduced in dimensions. One sliver only being put up to each gill, in this instance, the latter are made much smaller, the gill-pins being finer and more closely set than in the preceding machines, which enables eight gills to be mounted ou one travelling bar, in place of four, as previously.. The draught in this case is usually as 7 to 1, so that the roving is greatly reduced in dimensions, measuring about 294 yd. to the lb. This necessitates the introduc tion of the flier-spindle, and the use of the bobbin as a receptacle for the roving.