lding
a full mixing batch. The above diagram explains this setting. The mixed
coffee in the discharge bin is either drawn out into bags or sent by an
elevator to a milling machine or direct to the coffee roasters. A batch
ready for mixing can always be accumulated in the feed bin while the
previous batch is being mixed or discharged.

The fan is usually hung to the ceiling over the mixer as indicated, and
connected to the suction box by a 1-in. round pipe. The fan outlet can
be carried directly out-of-doors; but the dusty discharge is
objectionable in most installations, and this pipe is usually carried to
a dust collector from the top of which the roof outlet is connected.]

The efficient roaster-executive equips his entire plant with approved
labor-saving devices. In the better establishments, the coffee is
carried along by mechanical conveyors through all the operations from
the first cleaning machine to the final packaging.

_Separating_

As already mentioned, a machine frequently found in wholesale plants is
the separator, or grader. This apparatus, which is the same in principle
in all countries, but varies in size and form according to local
requirements, consists of a series of perforated screens. The
perforations differ in size; and as the coffee is shaken on them, the
small beans drop through the holes, the larger ones passing across the
screen and dropping into a receptacle or chute ready for the next
operation. The screens are made to grade the beans into large and small
peaberry; large, medium, and small flat beans; brokens; and other
commercial sizes. The average separator will grade fifteen to twenty
bags of coffee in an hour.

[Illustration: Green-coffee-milling machine having a capacity of forty
bags of green coffee per hour; with sifter, feed-pipe suction, and a
final separate suction at the discharge hopper]

[Illustration: Green-coffee separator without fan; with feed elevator,
discharge chutes, and motor drive. View of right-hand side and feed end]

[Illustration: GREEN-COFFEE SEPARATING AND MILLING MACHINES]

_Milling_

Milling machines, for cleaning the green coffee, operate on practically
the same principle the world over, varying in capacity and details of
construction. A popular type used in the United States has two metal
cylinders, one set within the other, and revolving in opposite
directions. The inner cylinder is ribbed with flanges, and the outer one
is lined with wire clot