After passing between the roll and the bed-plate, the pulp flows down the “back-fall” D′, and finds its way round to the other side of the mid-feather. On the inclined part of the floor, and immediately in front of the bed-plate I, a small depression is made, covered with an iron grating, for the purpose of catching buttons, small pieces of stone, and other heavy substances that may have found their way into the rags. There is generally a similar grating with rather finer openings on the other side of the mid-feather. The engine is constructed of iron, generally made in one casting.
The dirty water from the rags is removed by the “drum-washer” C. It is divided into compartments by the partitions shown by the dotted line c. The centre of the drum is formed of a conical tube, the narrow end of which is towards the mid-feather. The ends of the drum are generally made of mahogany, as this is found to stand the action of alkali better than any other wood. The periphery is covered with fine copper or brass wire-cloth, laid on to a backing of a much coarser material. An improved form of backing has been introduced lately, which is much more durable than wire. It is formed of brass cut into the form shown in {87} Fig. 20. The drum can be raised or lowered by the small wheel F, and it is driven by a belt on the shaft that bears the roll.
FIG. 20.
The wash-water passes through the wire cloth into the compartments formed by the partitions c, and finding its way down to the narrow end of the inner conical tube, flows out through the side of the drum into a trough which is placed across the washer to receive it. Or it may, as shown in the drawing, be conducted through the mid-feather itself, which is made hollow at this part for the purpose.
Another form of drum-washer, called the siphon-washer, is sometimes used. Its construction will be understood by reference to Figs. 21 and 22.
The drum is simply a hollow cylinder of wire cloth, the ends of which are formed of wood. Inside the cylinder is the siphon tube A, into which the water passing through the wire cloth flows. The continuation of the siphon tube B (Fig. 22) is made of flexible tubing. The action of the siphon is commenced by filling it with water through the cock C (Fig. 22). The water then flows in the direction indicated by the arrows. The tube A is fixed, and passes through a hollow journal fitted on to the end of the drum. {88} The other end is connected with the rod E, on which the driving pulley D is placed.
FIG. 21.
