Improvements in Sifting Machines for Granular or Pulverulent Substances.
Year: 1894

page_text: Date of Application, 17th Sept., 1894-Accepted, 20th Oct., 1894
COMPLETE SPECIFICATION.
Improvements in Sifting Machines for Granular or Pulverulent
Substances.
I, HEINRICH SECK, of No. 15 Leubnitzer Strasse, Dresden in the Kingdom of
Saxony, and Empire of Germany, do hereby declare the nature of this invention,
and in what manner the same is to be performed, to be particularly described
and ascertained in and by the following statement :-
This invention relates to sifting machines, and more particularly to machines
of the class generally known as centrifugal sifting machines, said machines usually
embodying a rotatable frame or casing spanned with bolting cloth, and a frame
rotatably mounted therein and provided with wings or beaters which upon the
said frame being rotated, act, in conjunction with the centrifugal force, to throw
the material to be sifted against the inner surface of the bolting cloth. As is
well known the said wings may either extend spirally in a longitudinal direction,
or they may be twisted, pitched or "set" so as thereby to cause the material to
be conveyed through the machine, in a longitudinal direction.
The sifting machines of this class as heretofore generally constructed, have
presented this objection that the wings while propelling the material outwardly
and, at the same time, conveying the same through the machine, would allow a
comparatively limited portion only of the surface of the bolting cloth to perform
a proper sifting action whilst by far the greater part of the sifting surface would
remain out of contact with the material to be sifted.
The object of my present invention is to remove this objection and to provide
means for securing a more efficient sifting effect in machines of this class, and,
at the same time, to secure other advantages which will be more fully hereinafter
referred to.
My invention, therefore, consists in providing between each two of the pro-
pelling wings of a centrifugal sifting machine, one or more additional or auxiliary
elevating or sucking wings or blades, the said auxiliary wings being so arranged
as to properly seize the material and to allow it to slide down along the inner
surfaces to be thereunder seized by the propelling wings and thrown against the
sifting surface, the said auxiliary wings also acting to produce an air draft and,
thus, regular pulsations of air which assist in causing the material to be properly
brought under the action of the propelling wings, and which produce a most
efficient sifting action, the material being by these means equally distributed
over, and brought into thorough contact with, the entire sifting surface.
In the accompanying drawing illustrating my invention
Figure 1 is a vertical longitudinal section of a sufficient portion of a sifting
machine provided with my improvements, to render the arrangement and operation
thereof properly understood.
Figure 2 is a corresponding vertical transverse section, and
Figure 3 an enlarged sectional view of a peripheral portion of the drum
showing the arrangement of the propelling and of the auxiliary wings thereon.
A illustrates the frame or casing spanned with bolting cloth. Within the same
is journalled the drum B, the latter being either of cylindrical shape, as shown,
or having a polygonal or other suitable cross section, and having rotary movement
imparted to it by any suitable and well known means. The said drum is provided
with the propelling wings a each of which may be either slotted or formed with
a continuous surface, as may be desired. Between each two of these propelling
wings a are mounted the auxiliary elevating or sucking wings b the same being
preferably secured to the drum in the manner illustrated more particularly in

page_text: Figure 3, and otherwise essentially conforming in shape to the wings a. c are
air slits or apertures provided in the walls of the drum B.
The operation of the drum provided with my improved arrangement of wings
as described, is as follows, that is to say :-
Upon the drum B being rotated the auxiliary elevating wings b will lift the
material to be sifted and will then, during their upward movement, allow the
same to slide down along the same along their inner surfaces, as indicated in
Figure 2. The said material will thereupon be seized by the propelling wings a
and thrown against the inner surface of the sifting or bolting cloth on the frame A.
The auxiliary wings b acting. to displace the air from within the space d
contained between themselves and the said propelling wings a, will produce
within such space a certain rarefication of the air, thereby causing a current of
air which will convey the material to the lifting or elevating wings a. The
latter will, at the same time, produce a pressure current of air moving in a
radially outward direction. A continual change of air will thus take place between
the drum B and the sifting surface, producing regular pulsations and causing a
most efficient sifting action while, at the same time, tending to keep the sifting
surface open.
It will be seen that by this compound arrangement of wings in a sifting machine,
as described, the material to be sifted will be thoroughly distributed over the
entire sifting surface so that the entire area of its inner peripheral surface will be
brought into action, whilst with the arrangement of wings as heretofore generally
employed by far the greater part of the said surface would remain practically out
of action and a comparatively limited portion only would be utilized for actual
sifting.
Having now particularly described and ascertained the nature of my said inven-
tion, and in what manner the same is to be performed, I declare that what I
claim is :-
1. In a sifting machine the combination, with a rotary drum surrounded by the
sifting surface and provided with propelling wings, of auxiliary elevating or sucking
wings, such as b, arranged between the said propelling wings, substantially as and
for the purpose specified.
2. The drum B having the propelling wings a and intermediate auxiliary elevating
or sucking wings b, as described.
3. In a centrifugal sifting machine, the arrangement of one or more elevating or
sucking wings between the propelling wings a applied to a rotary drum having
the air slits c, substantially as and for the purpose described.
Dated this 17th day of Santambo- 1004
HASELTINE, LAKE & Co.,
45, Southampton Buildings, London, W.C., Agents for the Applicant.