To obviate the necessity of removing the roll, a small machine has been devised whereby the knives can be cut in situ. This machine, which can be firmly fixed between the mid-feather and the side of the beater, consists of a small steam-engine which actuates a movable cutter, which is made to pass to and fro horizontally along the edge of each knife in succession. The engine is supplied with steam by a piece of strong flexible rubber tubing.
The ordinary form of beater contains only one roll, though some have been constructed containing two or even four rolls. In America, beaters of a totally different construction are much in vogue. The most important of these are the Jordan and Kingsland beaters, so called from the names of the inventors. The former consists essentially of a roll in the shape of a truncated cone, fitted with knives in the usual way, revolving in an iron box of corresponding shape, furnished with knives placed in the direction of its length, but at slightly different angles. The half-stuff enters the beater at the narrow end through a box provided with an {122} arrangement for regulating the flow, and is discharged by two or more openings in the cover at the wider end.
The Kingsland engine consists of a circular chamber, the sides of which are covered with knives, and between which a circular plate, also furnished with knives, revolves. The pulp enters through a pipe in the centre of one of the sides of the chamber, and flows out through an opening in the opposite side.
Another form of beater is that invented by S. L. Gould. The only essential difference between it and the Kingsland beater is that, instead of having a plate which revolves vertically against two stationary ones, the plate, which is placed horizontally, is furnished with knives on one side only, and revolves upon but one fixed plate, much in the same way as a pair of millstones.
The half-stuff supplied to these forms of beater is generally disintegrated to a greater extent in the breaker than is the case with those of the ordinary construction, as it is necessary to make it flow easily through them, and this could not be done if the fibres were kept long. A single passage of the pulp through the beater is sufficient to beat it up ready for making into paper. The chief advantages claimed for them is that they are more economical, both of time and power; also that the pulp is more regularly beaten.
Certain new forms of beaters have lately been introduced in this country, and are rapidly gaining in favour, chiefly on account of the saving of driving power, and the space occupied, compared with the amount of “stuff” they are capable of beating. Fig. 35 shows the construction of Forbes’ patent engine, as manufactured by Messrs. G. & W. Bertram, of Edinburgh. This beater is divided into three channels. The rolls, one of which is shown uncovered, are placed in the outer channels, while in the centre one the mixing and circulating wheel a is placed, the peculiar construction of which enables it to throw the pulp alternately into the two outer channels, from whence, after passing under the rolls again, it enters the central channel at the other end of the beater. {123}
In Umpherston’s patent engine great economy of space is effected by causing the pulp to travel over and under the backfall (a, Fig. 36). Another advantage is that the stuff circulates freely with less water than in the ordinary forms, thus increasing its output. It is also claimed that the pulp is beaten with less power, and as it is less liable to lodge in corners it is more evenly beaten.
FIG. 35.
The construction of the engine will be readily understood by reference to Fig. 36. The direction which the stuff takes is indicated by the arrows.