IMPROVEMENTS IN CENTRIFUGAL BOLTING-MACHINES
Year: 1885

page_text: I, EMIL STREITZ of the town of Freienwalde, in the Kingdom of Prussia and
German Empire, Manufacturer do hereby declare the nature of my invention for,
IMPROVEMENTS IN CENTRIFUGAL BOLTING-MACHINES, and in what manner' thé
same is to be performed, to be particularly described and ascertained in and by the
following statement:—
Many attempts have been made to construct vertical bolting-machines, but it has
always been found that the system was defective.
;
The improvements which form the object of the present invention, not only
provide a thoroughly practical vertical bolting-machine, but also throw light on
the theory of bolting in general.
In order to render the several improvements more intelligible, I shall, in the first
place, refer to the different systems already known, as far as they bear on the
subject, showing, at the same time, how erroneous they are.
'
In the first place it used to be said, that the material to be bolted fell down too
quickly and was, therefore, not thoroughly sifted.
To obviate this evil, all sorts of horizontal discs were introduced between the
beaters, in order to take up the material and continually cast it afresh against the
gauze-sieves.
It was even suggested to introduce the material from below and sift it during
its ascent through the apparatus.
It will appear strange then that, in the present system, it is recommended to
dispense with intermediate discs as far as possible.
When it was found that a satisfactory result could not be obtained in this manner,
the true solution of the question was more nearly approached by taking into
consideration the motion of the air produced during the process of bolting.
The air driven out of the cylinder was again introduced through both ends of
the same.
4
In this manner a continual current of air was obtained, but one evil amongst
others was that the air driven back into the cylinder was strongly impregnated
with flour, which continually returned to the cylinder and, therefore, had to be
bolted afresh, and so the working power of the machine was diminished,
PD
i

page_text: I, therefore, cause the air driven out by the fans to pass through sieves into
straining boxes from which the fans again suck back the air.
Silk gauze has hitherto been employed in two ways; either it was fastened to a
wooden frame divided into several small panels, or it was stretched over the two
end-rings of a kind of drum.
In both cases the gauze was stretched tight, and this, indeed, was indispensable
in order that the gauze should keep at the same uniform distance from the fans.
When the gauze was stretched over rings, a special contrivance for stretching it
had to be employed, as the gauze became slack in such a large piece.
In the present invention, this old method is entirely abandoned, and the gauze is
purposely mounted loosely around the fans.
To prevent the fans from touching the gauze (which would in that case soon be
torn off) a net, made of any suitable material, is stretched between the circle
described by the fans and the silk gauze, and is only intended to prevent the
fluttering gauze from coming in contact with the fans.
To protect the network from being injured by the fans and, at the same time,
allow the latter to sweep as close to it as possible, the outer edges of the fans are
covered with some elastic material, such as cloth, leather &c.
In the accompanying drawing, Figs 1 and 2 represent respectively a vertical and
a horizontal section of a vertical bolting-machine. In Figs 3 and 4, the fans or
beaters are shown on a larger scale, together with the sieve and the network
lying between
The machine consists essentially of a hollow shaft a, provided with an upper
journal b¹, and a lower one b.
These journals are let into the end-caps of the hollow shaft c and c¹ which allow
the air to enter the shaft between spokes or radial arms.
The shaft a itself is pierced with a number of holes or slits a¹.
Several vertical fans or rings f are arranged between two discs t and t¹ fixed to
the upper shaft or axle a.
The upper disc t serves at the same time as a spreading-plate for the material
coming from the feeding aperture.e.
Strips of some elastic material o are adapted to the outer edges of the wings f;
is a frame carrying the network 8, and the sieve g; p is a frame carrying a
number of sheet-iron strips n and the filter or sieve d; v are connecting pipes
between the air-chambers and the shaft a; h represents the discharge-pipes for the
flour and the discharge pipe for the coarser portions conducted to this pipe by
the rake or blade m.
To ensure the air striking the bolting and filtering surfaces as far as possible
perpendicularly, the shaft a is divided by a horizontal partition ; thus the air
forms two different currents, one above and the other below the said partition.
The working of the said machine is as follows:
The material reaches the spreading plate t through the feeder and thence falls
between the beaters or fans which throw it against the gauze sieve and carry it
round the latter in a spiral path, until it is freed from all fine particles and leaves
the machine by the outlet i.
The fine flour, which can pass through the sieve falls out of the machine through
the outlets h, h, h. The vertical beaters act also like a ventilator, sucking in the
air through the openings a¹ of the hollow shaft a, and driving it through the
sieve.
°
Since the ends of the hollow shaft a communicate with the interior of the bolting-
machine, the fan-work again sucks in the air it had driven against the sieve,
through the filter d.
Thus a continual current of air is produced which prevents any excess of pressure
in the interior of the machine, with the exception of the sieve, and thus the process
of bolting is facilitated.
'nin alan contas other important purposes.

page_text: In all other bolting-machines, the fan-work produces a great deal of wind which
tries to find an outlet through every crack and crevice, and may cause the sifted
material to be mixed up together.
The present arrangement prevents all dust, for the machine admits as much
wind as it expels, and there is, therefore, no excess of wind to blow through
accidental openings.
A most important point is, that the bolting-machine sucks in no more fresh air
through the feeder, so that no moisture reaches the interior of the machine, and
thus all sweating is avoided without having recourse to suction.
So that the air may allow the flour borne by it to fall easily, the current of air
is divided into two opposite directions in the hollow shaft a, which is divided into
two compartments by the above-mentioned partition.
Since the air is sucked in through the filter equally from above and from below,
the direction of the current is about normal to the filtering surface.
In order to avoid clogging the filter too rapidly with flour, strips of sheet iron
are placed before the former, but they are only accessories, since the filter only
takes up a certain quantity of flour, and then lets it fall, so that the process is
continuous.
An important part of this improvement consists in the employment of a slack
gauze sifter, combined with a grating which prevents the wings from coming in
contact with the gauze.
As the gauze is slack, it is moved backward and forward by the current of air,
and is thus always kept free from any particles of flour which might otherwise
adhere to it. The gauze can be mounted slack in several ways; for instance, as
shown in the drawing, frames may be employed forming large panels with a
minimum of cross-bars.
The gauze is glued on to the round frames at the top and at the bottom, and
then can be also fastened to a pair of longitudinal bars.
In order to provide convenient access to the machine, the four sides are provided
with doors, which also serve to close the suction-chambers. The filters and the
luffers are also fitted in removable frames and the sifting gauze is mounted or
glued on frames consisting of two parts.
The details shown in the drawing can, of course, be varied; for instance, the
current of air need not pass through a hollow shaft, but a solid axle may be
employed, and the air can have access to the fan-work through a concentric
opening cut out of the spreading-plate t or t¹.
The currents of air must then be separated by a partition reaching almost to the
edges of the vertical wings or beaters."
The upright wings can also be placed in any position, for instance, if they are
made of metal, they can be so shaped as to offer as little frictional resistance to the
current of air as possible, or they may assume a helical form.
Having now particularly described and ascertained the nature of my said
invention, and in what manner the same is to be performed, I declare that what
I claim is
1. The method of bolting in centrifugal bolting machines which consists in
causing a continuous and endless current of air produced by fans or beaters to pass
through the sifting surface, and, after being purified by a strainer or filter, to be
again sucked in by the said fans or beaters.
2. The separation of the continuous current into two currents by means of a
partition a.
3. In vertical bolting-machines a fan-work consisting simply of vertical wings or
beaters, and in which horizontal intermediate discs are only used for the purpose of
securing the said wings.
4. In centrifugal bolting-machines, the employment of slack gauze sifters, which
can have an undulating motion while the machine is at work, for the purpose of
cleaning themselves automatically.

page_text: 5. A grating.consisting of longitudinal or. cross-bars, and placed in. centrifugal
bolting machines between the wings and the sifter to prevent the former from
coming in contact with the sifter.
.. 6. In centrifugal bolting-machines, the employment of wings the outer edges of
which are provided with some elastic material, such as cloth, leather &c.