CENTRIFUGAL CLEANING MACHINES

147

time he makes the change and be prepared for the results, which, unless under-
stood, may mislead him into altering his stuff gate. The best method for
keeping in touch with the weight is to follow the change by altering the driving
speed.

At one time it was considered necessary to have an elaborate 'mixing
box' where the stuff and water emerge from their respective gates. This
opinion still persists, but many machines have none, and never experience any
difficulty from their absence. The best mixing may be obtained by causing
the water to strike the flow of stuff as it
leaves the stuff gate at right angles on an
inclined plane, or the water may be
made to fall on it from above. The
force of the water effectually breaks
clumps of fibres and carries them well
mixed into the shutes. Any good that
a mixing box may accomplish in the
way of retaining sand or metal is counter-
balanced by the fact that it is usually
under the level of the shutes, and in an
awkward position for being cleaned.
Also it has to be emptied, and this means
losing stuff. The shutes should have a
fall of about 2 feet into the strainers,
and this will be ample for mixing the
fibres and water.

CENTRIFUGAL CLEANING MACHINES

Most mills nowadays which make [BL&jnmEHsfnemgC*.

fine papers rely almost entirely for the Rc- 4-2.—THE ERXENSATOR, SIZE iv, SHOWING

cleaning of their stock and the freeing of _____

it from foreign matter such as metal,

sand, shive, rubber, etc., on centrifugal machines, such as the Erkensator, which
was the first of these machines. These machines depend for their efficiency
on the action of centrifugal force. The fact that ceEdose, water, and to a less
extent loadings in general, have specific gravities sufficiently near to each
other, enables these to pass through the machine together, while heavier and
lighter substances are retained behind projecting rings, or in the case of lighter
particles are removed by skimmers.

The machine (Fig. 42) consists of the following parts: An outer container
with lids for access, and a trough running right round the top for receiving the