Improvements in Sifting Apparatus.
Year: 1894

page_text: Date of Application, 31st Oct., 1894
Complete Spécification Left, 31st May, 1895-Accepted, 13th July, 1895
Improvements in Sifting Apparatus.
We, AUGUST ROHRBACH, Engineer, MAX MEYER, Merchant, and WILHELM
BINDEWALD, Patent Agent, all of the Firm of A. Rohrbach & Co., 6 Bahnhof-
strasse, Erfurt, Germany, do hereby declare the nature of this invention to be as
follows:-
It is a well known fact based on the nature of the apparatus, that the material
fed on to the bottom of a rotating flat sieve, moves, after overcoming the frictional
resistance, without further exciting cause, merely in a circular path resulting from
the peculiar motion of the entire apparatus, and that said material has no tendency
to move onwards. Endeavours have been made to produce this very necessary
onward movement of the material in the channels or gutters of flat sieves by means
of various peculiar devices which have however all had more or less considerable
disadvantages. These disadvantages consist mainly in the fact that the construction
of the said devices entails the formation of more or less large angles in which the
material gets caught, is stopped and so becomes fixed, and finally putrefies or
spoils. Special conveyors have also been employed in the sifting channels of the
collecting bottoms, but such conveyors are liable to break down from various causes
and require constant supervision. Now the present invention relates to conveying
means for effecting the onward travel of the material in the horizontal channels of
a Ĥat sieve in an extremely simple manner. The arrangement also has the advantage
that the sifting covering is kept cleaned by reason of the peculiar manner in which
the material being sifted is thrown up by the conveyor; and moreover the onward
movement of the material being sifted can be accelerated to different extents, at
different places
on the sieve. Our conveyor is illustrated in its application to a flat
sieve in the accompanying drawings in which:-
Fig. 1 is a plan, and
Fig. 2 a cross section.
According to our invention bars care arranged at the sides of the channel a above.
the sieve b, parallel to the sifting surface bat a suitable distance from the letter,
These bars care formed with circular, rectangular or other suitably shaped
apertures d. These bars c operate as follows:-
In addition to the circular motion of the ground material on the sieves, the
pendulating movement of the flat sieve produced by its mode of suspension imparts
to the said material an up and down hopping or jerky motion in a direction
perpendicular to that of the circular motion. This hopping or jumping motion is
partly interrupted by the bar c, so that the tangential motion produced by the
circular motion combines with this jumping motion to form a resultant which
first causes the particles of the material to be sifted situated next to the bars
to execute a progressive onward jumping movement. But when the material
being sifted jumps through an aperture d, the said material jumps over the bar
and glides off from the latter in consequence of the circular motion of the flat
sieve.
In this manner the bar c scatters the material falling off it over the sifting
surface. Consequently by arranging the bar e provided with apertures d, there
is produced a movement of the material passing through the apertures in
consecutively connected cycloidal curves. The material to be sifted being thus
[Price 8d7

page_text: caused to fall back upon the sifting surface causes said surface or covering to
vibrate or oscillate and thus effects the cleaning of the same. The material to be
sifted is fed in ate and passes very quickly to the outlet f, and may thence be
conducted on to a grating 9 which allows the finer portions to fall through it, and
serves to guide the remainder to the discharge h. According as the apertures d are
made larger or smaller, the speed of the onward movement of the material being
sifted may be caused to vary at determined points of the flat sieve; increase in the
size of the apertures acting to diminish the speed of the onward movement of the
material being sifted.
Improvements in Sifting Apparatus.
We, AUGUST ROHRBACH, Engineer, MAX MEYER, Merchant, and WILHELM
BINDEWALD, Patent Agent, all of the Firm of A. Rohrbach & Co., 6 Bahnhof-
strasse, Erfurt, 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 :-
It is a well known fact, based on the nature of the apparatus, that the material
fed on to the bottom of a rotating flat sieve, moves, after overcoming the frictional
resistance, without further exciting cause, merely in a circular path resulting from
the peculiar motion of the entire sifting apparatus, and that said material has no
tendency to move onward in the direction of the length of the sieve. Endeavours
have been made to produce this very necessary onward movement of the material
in the channels or gutters of flat sieves by means of various peculiar devices all
of which however had more or less considerable disadvantages. These disadvantages
consist mainly in the fact that the construction of the said devices entails
the formation of more or less large angles in which material is caught, and
becomes fixed, so that it finally putrefies or spoils. Special conveyors have also
been employed in the sifting channels of the collecting bottoms, but such conveyors
are liable to breakdowns from various causes and require constant supervision.
Now the present invention relates to conveying means for effecting in an extremely
simple manner, the onward travel of the material in the horizontal' channels of a
flat sieve. The arrangement also has the advantage that the sieve bottom is kept
cleaned by reason of the peculiar manner in which the material being sifted is thrown
up by the conveyor; and moreover the rate of onward movement of the material being
sifted can be accelerated to different extents at different places on the sieve. Our
conveyor is illustrated in its application to a flat sieve in the drawings filed with our
Provisional Specification,
Fig. 1 being a plan, and
Fig. 2 a cross section.
The conveyor consists of bars e arranged at one side a of each of the
longitudinal channels above the sieve b, parallel to the sifting surface band at
a suitable distance say one inch therefrom; these bars c are each formed with
circular, rectangular or other suitably shaped apertures d, and operate as
follows:-
In addition to the circular motion of the ground material on the sieves, the
pendulating or vibrating movement of the flat sieve produced by its mode of
suspension, imparts to the said material an up and down hopping or jerky motion

page_text: in a direction perpendicular to that of the circular motion. This hopping or
jumping motion is partly interrupted by the bar c so that the tangential motion
produced by the circular motion combines with the jumping motion to form a
resultant motion which causes the particles of material being sifted situated next
to the bar, to execute a progressive onward jumping movement. But when material
being sifted jumps through an aperture d, it falls over the bar c from which it glides
off in consequence of the circular motion of the flat sieve.
In this way the bar c scatters the material falling off it over the sifting surface.
Consequently by the use of the bar c having the apertures d, there is produced a
movement of the material passing through the apertures, in consecutively connected
cycloidal curves. The material to be sifted being thus caused to fall back upon
the sifting surface, causes the said surface to vibrate or oscillate, and thus effects
the cleaning of the same. The material to be sifted is fed in at e and passes very
quickly through the longitudinal channels to the outlet f, and may thence be
conducted on to a grating 9 which allows the finer portions to fall through it, and
serves to guide the remainder to the outlet h.
According as the apertures d are made larger or smaller, the speed of the
onward movement of the material being sifted will be caused to vary at
determined points of the flat sieve, increase in the size of the apertures acting to
diminish the speed of the onward movement of the material being sifted.
As will be obvious our invention can be applied to sieves of the kind referred
to having only one longitudinal sifting channel, and also to sieves having more
than two such channels there being one conveying bar or device to each channel.
Having now particularly described and ascertained the nature of the said inven-
tion and in what manner the same is to be performed we declare that what
we claim is :-
-
1. In sifting apparatus provided with flat sieve to which motion is imparted in
a closed path, the use for the purpose of causing onward movement of the material
being sifted, in the longitudinal channel of the flat sieves (sieve frames or collecting
bottoms), or in each such channel when two or more are used, and for keeping the
sifting surface or surfaces clean, of one or more bars c formed or each formed with
apertures d and arranged above and parallel to the sifting surface so as to act
substantially in the manner herein before described.
2. In the sifting apparatus specified in the preceding claim, making the
apertures. d in the bars c of different sizes at different points in the length of
the bars for the purpose of varying the rate of onward movement of the material
being sifted.
Dated this 214 1
100