Pittsburg dispatch. [volume] (Pittsburg [Pa.]) 1880-1923, 1892-03-20

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Purifier for Mddanos.
rollers give satisfactory results, but thei,
employment is limited; chilled iron II
watch the first pair of rollers at work We
observe that one of them revolves fastel
than its mate SO that grain Of wheat
caught on the projection of q slow roller i.
stretched out or unfolded by the projection
Of the quick one. This action it is which
| opens the grain 20 as to shell out the mid.
dlings, without at the same time making
more than a trifling quantity of -four. A
point just here to which. the miller payl
particular attention is keeping these rollers
at the right distance apart.
The Size OF tho Grains.
If too far from each other they take nc
hold Of the wheat; If too near, they mash II
into flakes which resist the four preparing
process following up the rollers work.
| Clearly, then, it Is desirable that the grain
submitted to the rollers should be as nearly
Of size as possible. As rule spring wheat
is small, and winter wheat large, but what
ever the variety of the grain it is usual to
| divide it into two sizes before reduction be-
gins. For this purpose rotating sieve, OF
| revolving cylinder, is employed. Through
Its meshes the smaller grain falls into a
| trough leaving the larger witheut.
When wheat has passed through the first
pair of rollers the product is conducted to q
scalping reel This reel is revolving
cylinder, covered with wire having about
324 openings to the square inch. As the
meal is carried up its ascending side The
Anr1r md - So11
of the cylinder is inclined, and the portions
of wheat stock which cannot get through its
meshes gradually find their way to the
cylinders end or "tail," there to be taken
to second pair of rollers for second re-
duction, in principle essentially the same
as the first. To the second pair of rollers
succeed others, until a fifth or even sixth
pair 10 reached Each pair has more CORFU
cations to the inch than its predecessors,
and has its two rollers placed nearer to-
gether
Fine siiks Used gos Betting.
In following the partly broken wheat to
the second pair Of rollers, we left behind us
for a moment the -four and middlings due to
the first pairs action. These two products,
the miller reminds Us, were delivered BY
the scalping reel as mixture. He now
submits them to boiling reel, a frame clad
with silk, having hundreds Of thousands of
apertures to the square inch. This reel Is
cylindrical, form much preferable to the
six-sided shape of old patterns Through
its apertures the -four readily passes, leav-
ing the middlings in the reel In this wav
scalping and boiling reels follow up each
successive pair of rollers, their meshes
gradually becoming finer and finer. How
much finer depends upon the character of
the wheat and the general conditions under
which a mill is operated. As a rule the
silks run one number or size finer at each
reduction.
We are shown a variety of cloths, all of
European make. ranging from 576 to %, 900
meshes to the square inch. The durability
Of these silks is astonishing. With soft
wheat reel will serve six or seven years
and remain in good condition. Wheat
attracts moisture SO readily from the
atmosphere that its darnpness foretells
coming storm as certainly as q falling
barometer. On muggy days boiling is 50
much retarted that, if possible, the miller
slows down operations. Under his guidance
we now retrace our steps to where we left
the bolting reels delivering their middlings.
We are now to see what becomes of them.
Mixed as they are with particles of bran,
fiber, and other impurities they 70 to q
separator, contrived upon a principle as
SIMPLE as 1t Is eHectlve.
The Process OF Purinoation,
In windy weather if we inspect the dust
borne to the window-sills at the various
levels of tall building we will find de-
cided difference in Its quality Tho dust
which has risen to the top story is much
finer than the dust deposited at the ground
floor. The wind has carried light particles
farther than heavy ones This action is i'm
itated in the aspirators and purifiers of our
mill. A sharp blast of air Is directed against
the mixture of middlings, bran, and fiber; as
the finer and lighter fragments can be blown
farther than the heavier and coarser they
are separated into their special boxes or
chutes. Purifiers are made in a variety of |
designs; the illustration gives an idea of the |
main features in which they agree. Machines |
of this type are also set at the task of divid- |
ing middlings into coarse, fine and low |
grades, incidentally freeing them from any
admi1ture OF bran and germ they may con- |
tain. These repeated operations are neces-
.ary because no single one of them is per-
Fect in Its results The processes of separa-
lion and publication thus 60 on hand in |
hand, but there remains an important class
If them to which we are now brought
As the rollers have gradually turned out
! finer and finer product point is reached
where middlings, germ and bran are de-
ivered In particles very similar in their
minute size and weight The differences
which exist between them are too slight tor
my process Of separation to seize upon,
The silk Of the bolting reel can divide
mall particles from large; the aspirator, or
'urifer Of other type, can disunite light
PARTICLES from heavy ones Here the et.
ective working limit of both is passed.
Tho Use OF Smooth Rolls.
Now, by bringing his final mixture of
niddlings, germ and bran to rolls of smooth
urface the miller sets up precisely such
Inference of structure among them as 0
eparating process demands. He breaks ND
he middlings into still finer fragments,
lattens the germ and thoroughly detaches
he bran from the niddlinga This last and
inest yield Of middlings can now be sepa-
ated by bolting reels Of somewhat coarse
mesh. When the wheat is of the hard,
pring variety grown on the prairies of
Dakota and the, Northwest gen.
rally, the middlings in the last reduction
re sometimes too fine and tough for rollers,
ither corrugated or smooth, to have any
seful effect upon them. At this point
here is nothing to do but have recourse to
he milestone to effect the final manufacture
nto -four. Rollers do quite as well on
,ellower wheats, less tough in texture, and
n winter wheats A good many large
Minnesota mills rely entirely on rollers;
he employment of millstones for the last
eduction is. taking the Union as whole,
teadily declining.
Although millers have succeeded in taking
rom their bran almost every particle Of |
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