IMPROVEMENTS IN CENTRIFUGAL FLOUR SIFTING OR BOLTING MACHINES
Year: 1878

page_text: PROVISIONAL SPECIFICATION left by William Robert Lake at the Office of
the Commissioners of Patents on the 12th June 1878. [A communication from
abroad by Wilhelm Seck, of Bokenheim, near Frankfort-on-the-Main, Germany.]
WILLIAM ROBERT LAKE, of the Firm of Haseltine, Lake, & Co., Patent Agents,
Southampton Buildings, London. "IMPROVEMENTS IN CENTRIFUGAL FLOUR SIFTING
OR BOLTING MACHINES." [A communication from abroad by Wilhelm Seck, of
Bokenheim, near Frankfort-on-the-Main, Germany.]
In order that the principle on which the said Invention is based may be fully
understood I will first refer to the flour bolting or sifting machines heretofore
ordinarily used.
Setting aside the oldest form of apparatus, that is to say, the bolter bag, which
was of very rude construction, and taking into consideration the hexagonal and
cylindrical bolter covered with silk gauze, I find that the stuff which has been
ground and is to be sifted or bolted is rolled into the inner sides of the bolter in a
kind of spiral line, chiefly by reason of the corresponding position of the cylinder,
and also partly because the particles are moved amongst each other when one of
the six sides lifts a portion of the ground material and lets it fall down on the next
flat side below it.
The ground material consists of particles of the most varied shapes, coarse grain
of round shapes, the outside hard particles of the grain of all possible irregular
shapes; amongst these also are pointed elongated pieces, and also particles of bran
of different shapes.
When the material which is to be bolted or sifted in the cylindrical bolter strikes
the bolter surfaces the fine portion will be passed through the meshes of the bolter
or the gauze; the pointed and elongated portions of the flour will also often enter
into one of the meshes by the points, and then will be forced through by the mass
behind them. The same may happen to particles of bran of like shape, and con-
sequently the flour becomes discolored.
The employment of a finer sort of bolter would only remedy the evil to a certain
extent, and hardly supply flour of a better quality, but on the other hand would
reduce the yield..

page_text: The cylindrical bolter in its original form and application is therefore not an
advantageous form of bolting machine. Cylindrical bolters with internal vanes or
shovels, so-called centrifugal bolting machines, serve the desired purpose somewhat
better, but in them a large portion of the ground material, and principally the
coarser part, remains a long time in contact with the surfaces of the bolter, and
rubs against it; therefore this construction also allows a considerable portion of
pointed and elongated particles to escape, and as these are chiefly particles of bran
and shells they spoil the appearance of the flour and deteriorate its quality.
Now let it be understood that the ground material ought to be thrown against a
fixed vertical bolter surface in the greatest possible division, and consider the effect
of such an operation.
When a ground material, just as it comes from the mill, is thrown in a wide
division from a certain distance against a vertical bolter surface, then all the
particles will receive a certain velocity, and each grain receives a certain momentum
corresponding to its velocity and its mass.
The heaviest particles consist chiefly of the best flour, will possess the greatest
momentum, will be dashed against the bolter with the greatest force, and con-
sequently will pass through its meshes. As they thus strike the bolter surface
vertically, or nearly so, such particles only as can escape freely through the exposed
meshes will pass through the same. The remainder fall down behind the bolter.
The particles of bran which though of large volume are light in weight, will, by
reason of their small weight, only possess a small amount of momentum, and will
soon be stopped, because their great volume encounters considerable resistance from
the air. They will therefore not fly far, and will either not reach the bolter at all
or will reach it with only a small velocity and force, so that they will not pass the
meshes of the same. The ground material will thus not only be separated according
to the shape and size of each single particle, but also according to the specific
gravity of the particles.
The more widely the ground material thrown against the bolter surface is caused
to diverge or spread the more successful will be the operation, that is to say, the
greater the bolter surface is in proportion to the quantity of the material thrown
against it the more certainly will the desired result be attained.
I am aware that bolting machines have already been made with stationary
bolters or sieves, but these act in a very incomplete manner, because they only
work with a proportionally small bolting surface, wherefore these are soon destroyed,
and the bolting is imperfectly performed.
In my improved bolting machine all of these considerations have been taken
into consideration, as will appear by the following description:-
In a square box I arrange vertically a cylinder provided with bolting gauze. The
framework of the same is made of vertical ribs and light horizontal hoops. The
gauze is fixed at the top on a cover, and at the bottom it is stretched over the ribs
and hoops, and forms a complete cylinder. In this bolting cylinder is placed con-
centrically with the same a hollow wooden cylinder, which revolves rapidly around
its axis. This cylinder has fixed to its circumference scoops or wings, which are so
arranged one above another that they form a double spiral. A wire funnel is
placed at the top of said cylinder. If, while the said drum or cylinder is revolving
rapidly, ground material falls through a wire funnel into the top coil or part of the
said spirals, they will, by the centrifugal force, be thrown against the sides of the
bolter, whereby a portion of it will pass through the meshes of the bolter.
The coarse part, and, as above explained, the lighter portions rebound from the
gauze to the next coil of the spirals, again to be thrown to the outside. The part
that rebounds from the gauze falls again on the next coil of the spirals, and so
on, until the ground material either has passed through the meshes or reaches the
bottom of the machine.
As the said ground material is thrown many times against the bolter it will take
a long time to reach the bottom, and only such portions will arrive there as are

page_text: too coarse to be able to pass the meshes or particles of bran, which because of their
large size are not able to penetrate the meshes, partly by reason of their small
specific gravity they did not come into contact with the bolter, or had so little
force that they glanced off from the fabric.
I consequently obtain a perfect bolting with due regard to the nature, shape,
and specific weight of the matter to be bolted. The fine bolted flour is collected
in sacks. The coarse parts and the particles of bran are discharged by an expeller
into a tube, and are collected to be re-ground.
An apparatus is provided for shaking the frame of the gauze cylinder, and
thereby keeps the meshes of the bolter open.
The ground material is by this improved machine not only sorted or separated
according to the shape and size of the particles of bran, but also with regard to
their specific weight, as the drum to a certain extent acts as a winnowing
apparatus.