SUCTION BOXES

183

is no probability of their being made greasy, and well away from the work
going on, until they are replaced. If spare straps are kept, and this is a wise
precaution, they must be stored in a cool damp place, and kept in such a posi-
tion that they have not to take any acute bend or twist, as after a time this will
become permanent and render them useless.

When changing deckles, the pins holding the deckle pulleys may be slacked
off and the pulleys assisted to move in the required direction. If the strap
runs off the pulleys, the wire may be scored and the strap damaged. It must
not be forgotten to tighten up the pins again; they may drop out and be carried
through the couch rolls, with disastrous results.

The deckle pulleys ought to be oiled and wiped clean at ever)7 opportunity.
A stiff-running pulley will make
the strap jerky and cause a lot f

of breaks before the source is dis-
covered.

Suction Boxes.—Many machines
have only two suction boxes. For
making paper from rag stock, when
we sometimes get very wet stuff,
two boxes are insufficient In any
case, three or more boxes are better
than two. Even if the paper we
make could be worked with two,
it is wiser to have a little suction
on each of three or four than a
strong suction on two, for then less
pressure is put on the wire, which
lengthens its period of use.

The usual type consists of an air-tight, oblong box (Kg, 65), very solidly
built of some hard, durable wood or brass. It is divided down the centre by
an open frame, which supports one or more bars according to its width. The
top edges and the bars are covered with very hard wood to take the wear of
the wire. The bars arc usually about i| inches apart and should not be more,
or the wire will be drawn down and over their edges. At the ends where the
edges of the wire travel, brass plates a few inches in length are let in to take
the wear of the rough edges. A pipe from the suction pump is connected to
the centre of the box at die bottom or the side. Movable ends are provided
to enable various widths of deckle to be followed. These are adjusted by a
heavy brass screw extending through the outer end of the box. The box »
made as rigid as possible, and is bolted and very firmly wedged in place «tt

FIG. 65.—SUCTION Box PLAN AKD SECTION