200

MODERN PAPER-MAKING

the best results the wet felt should be carried well round the roll, and there
should be a strong spray of clean water directed on to the felt immediately
before it goes to the roll, A very high vacuum is required in order to dry
the felt sufficiently to enable it to take up moisture from the paper when it
returns to the press. The chief advantage of this type of cleaner over the
travelling type is that it leaves the felt in the same condition right across the
machine.

The Evans Rota Belt type of suction box (Figs. 78 and 79) was originally
introduced to take the place of the fixed-top suction boxes under machine
wires, but it did not meet with very great success in the early days.

It was then developed for use under wet felts, in which position it has
thoroughly justified itself and become firmly established as an excellent means

[W. P. Evans and Son Ltd.
Rc. 78.—THE EVANS ROTA BELT, WITH THREE SUCTION BOXES,
HTTED BENEATH A WET FELT
of drying the wet felt, preventing blowing, and generally improving the per-
formance of the press rolls, besides increasing considerably the life of the wet
felt.
It has been considerably improved lately, and is now being used with success
in place of the fixed-top suction boxes under the machine wire.
It consists of suction boxes, usually in sets of three, each of which can be
ii&tivkbalfy amtroHed, Over these a grooved and perforated endless rubber
belt passes, driven through friction with the under side of the wire.
Toe vacuum in tJbe boxes draws water through the belt, and delivers
it to tiie fcadcwater system in exactly the same way as the ordinary
suction box.