8o

MODERN PAPER-MAKING

arranged that when the bed-plate is worn right down the roll will be about
\ inch away from the backfall.

Another point of importance in the design of the trough is the amount
of rise from the lowest level at the emptying valve to the plate. Some beaters
are quite flat and have no rise at all, and in this case the roll is deeply submerged

[Messrs. Crookes, Roberts and Co.
FIG. 2i.—VARIOUS SHAPES OF BEATER BED-PLATES
in die stuff and whips it continuously, without taking any more stuff through
between the plate and the roll bars.
This whipping, while doubtless aiding the fibrillation of the stuff, consumes
a great deal of power, and has the disadvantage of heating the stuff too much
for all the fibrillation it accomplishes.
Our experience with beaters of this type has convinced us that their circu-
lation is very poor, and that the continual whipping of the stuff dulls the colour
and spoils the purity of the paper.
We have described our ideas of a hollander beater in some detail, but