Fig. 14.
Bentley and Jackson's Rag Engine.—This form of engine is shown in Fig. 14. The trough is of cast-iron, and made whole, and the engine can be obtained of any required dimensions. The trough is provided with a sand-well, cast-iron grate, and cock in front of the roll, and a sand-well, cast-iron grate, and brass valve on the back of the midfeather, a brass let-off valve and a brass waste-water valve. The bottom of the trough is "dished," to prevent the stuff from lodging. There are two movable bridge trees, fitted with pedestals and brass steps, and wrought-iron lifting links and screws, worm-wheels, worms, cross-shaft and hand-wheel for simultaneously lifting the roll on both sides. The roll is covered by a polished pitch-pine cover. The drum-washer may have either iron or wooden ends, has strong copper brackets, and is covered with brass backing and covering wires, mounted on a wrought-iron shaft, and carried by cast-iron stands, fitted with improved lifting gear, driving-wheels, and pulley.
When the engine is set in motion by the revolving shaft or spindle, the combined action of the knives of the roll and bed-plate causes the rags, which circulate in the water, to be gradually cut into small fragments, and the operation is kept up until the rags are converted into what is technically termed half-stuff. While this process is going on, fresh water is constantly supplied by a pipe at the end of the washing-engine; and when it is found that nothing but clear water escapes from the drum-washer, this is raised, and the spindle bearing the roll is lowered, so as to bring the respective knives closer together, to enable them to cut the reduced material still finer.
Draining.—When the material is sufficiently broken, as it is termed, the engine is then emptied by means of its valves, and the contents run into large vats or drainers, furnished with perforated zinc floors, in which it is allowed to drain thoroughly; and in order to remove the water more effectually, the pulp is afterwards pressed, either by an extractor or a centrifugal drainer, which dries it sufficiently for gas-bleaching, or for treatment in the potcher or poacher. This is a larger engine than the washer, and instead of the cylinder and bars, has a hollow drum which carries on its periphery a number of cast-iron paddles, which thoroughly agitate the pulp, and thus render it more susceptible of being freely and uniformly acted upon by the bleaching agent. The drum-washer of this engine should have a finer wire than is used for the breaker.
Torrance's Drainer.—This machine, which has been extensively used, is manufactured by Messrs. J. Bertram and Son, of Edinburgh. It consists of a perforated cylindrical box, enclosed in a fixed case, which revolves at about two hundred and fifty revolutions per minute. The machine is capable of treating about 4 cwt. of pulp per hour.
[CHAPTER V.]
TREATMENT OF ESPARTO.