Improvements in the Method of and Apparatus for Sifting Granular Substances.
Year: 1897

page_text: Date of Application, 16th Nov., 1897-Accepted, 9th Apr., 1898
COMPLETE SPECIFICATION.
Improvements in the Method of and Apparatus for Sifting Granular
Substances.
I, FRIEDRICH GEORG WINKLER, of Zschoppan, Saxony, in the Empire of Germany,
and temporarily residing at No. 108, Grand Street, Jersey City, in the State of New
Jersey, United States of America, Civil Engineer, 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 the sifting of granular materials of various kinds, for
instance flour, meal sugar, tale, graphite, bone dust, and the like, by means of air
currents which pass alternately through the sieve from the outside inwardly and
from the inside outwardly. I have found that in order to render this method of
sifting effective it is necessary that a comparatively large volume of air be set in
motion and that it is also necessary that the material to be sifted should be subjected
to the action of the air currents in the following manner: A long and strong current
is first drawn inwardly through the sieve, whereby the particles which adhere to the
inner surface of the same are detached therefrom, and the sieve surface is cleared for
the succeeding sifting impulse and a large volume of air is drawn into the sieve ;
almost immediately thereafter a strong, sharp and sudden outward current of air acts
upon the material, whereby the fine particles are blown through the sieve; lastly
this outward sifting current is followed by or continued into a strong outward after-
current which blows the sifted particles so far from the sieve that such particles
cannot be caught and returned by the next following inward current. It is also
desirable that these currents should be produced by a device which moves at
comparatively low velocity in order to reduce the required power and the wear and
tear to a minimuin. Furthermore, it is desirable that means should be provided for
varying the velocity of this device which is the part of the machine upon which the
intensity of the stirring effect depends. For soft or moist material the speed of this
device should be higher than for dry or hard material.
The machine which is shown and described herein meets these requirements
and carries out this method of operation very effectively. This machine consists,
essentially, of a sieve, a plurality of concentric gratings, the outer one of which
revolves within the sieve with sufficient intermediate space to admit and carry
along the necessary supply of material to be sifted ; a plurality of fans, and a
plurality of independent vacuum generators arranged one within the other, so
that the vacuums are developed in any succession determined upon and are
regulated to maintain the inward current practically up to the instant when the
sifting blast begins.
The said machine is also so constructed that there are open spaces in the interior
thereof, which are connected laterally, so that the total volume of air brought into
the machine by the aforesaid inward current has sufficient room and does not generate
return currents, which would greatly reduce the volume of air brought in and impair
the efficiency of the machine. Further, the gratings, fans and vacuum-generating
devices, which latter I hereinafter term "suction blocks," are so combined together

page_text: that the inner suction blocks and gratings successively act upon and maintain or even
increase the main inward current of air almost up to the instant when the next
pressure blade or fan generates the next swift, strong and sudden sifting blast. The
strength and velocity of this blast are greatly increased by the movement in opposite
directions of the inner gratings and fans, and especially by the construction and
arrangement of the machine in such a way that a part of said inward current
rebounds or deflects outward with immense velocity and powerful sifting effect.
The fans are also so shaped and disposed as to provide the freest flow possible for the
air and interpose the least possible resistance thereto, so that the air encounters
practically no resistance until it is in contact with the fans. The machine is so
arranged that the devices for generating the outward after-current take their air from
the said inward current, thereby preventing the crowding of the incoming air, and
aiding to maintain the said inward current.
The driving mechanism is so constructed that the speed of the pulsator or air wave
generator can be changed without changing that of the sieve or deflecting grate and
that this change can be made while the machine is running.
In the accompanying drawings consisting of twelve sheets: Figure 1 is a
longitudinal vertical section of a sifting machine provided with my improvements.
Figure 2 is a vertical cross section in line 2-2, Figure 1 on an enlarged scale.
Figure 3 is a vertical cross section, partly broken, in line 3-3 Figure 1, and on the
scale of Figure 2. Figure 4 is an end elevation of the machine viewed from the left
in Figure 1. Figure 5 is a vertical section of one of the preferred forms and relative
position of the gratings, suction blocks and fans, as shown in Figure 1, but on an
enlarged scale. Figures 6, 7, 8 and 9 are cross sectional views illustrating
modifications in the arrangement of the gratings, suction blocks and fans, but all
arranged to effect the same method of sifting which is effected by the machine shown
in Figure 1. Figure 10 is a fragmentary perspective view of the wing plate carrying
the fans and suction blocks shown in Figure 1. Figure 11 is a fragmentary
. perspective view of one of the heads, shown in Figure 1, with its plurality of concentric
gratings. Figure 12 is a plan view partly broken, of the cone and belt driving
mechanism shown in Figure 1. Fig. 12 is a detail in end elevation of the cones
shown in Fig. 12. Fig. 13 is a vertical section in line 13-13 Figure 12. Figure 14
is a side elevation of a modified cone and belt driving nechanism. Figure 15 is a
horizontal section of a frictional disc driving device.
Like letters of reference refer to like parts in the several figures.
Referring to Figures 1, 2, 3, 4, 5, 10 and 11, A is the bolting chest within which
are arranged the sieve B, the concentric gratings C C1 C2 C3, the vacuum generators
or suction blocks d d¹ d2 d³, and the fans E E¹ E².
The sieve B may either revolve or be stationary; the gratings preferably revolve
in the direction of the arrow Figure 5,-i.e. in the direction opposite to the revolution
of the sieve B, if said sieve revolves. The said suction block and fans taken together,
I term the "pulsator" or "air wave generator," since they produce the alternating
air current whereby the working of the process is effected. These pulsators preferably
revolve at a comparatively high velocity, 400 to 600 revolutions per minute, in the
direction opposite to the revolution of the deflecting grates.
The sieve B is a cylindrical reel having its peripheral wall formed of a suitable
screen or bolting cloth stretched in any known and usual manner on frame 1, 2
(Figure 2). At one end the said frames are fastened to rims 4 (Figure 1) carried
on the ends of radial arms 5, 5 of a circular head 6, (Figure 3) and the other end of
said frames is fastened to a circular head 7, which is bent and flanged at its outer
part, as shown in Figure 1. Openings 8, 8 between said arms 5, 5, permit the tailings
to pass out to the discharge chute W. A flanged rim 9 on said head 6 revolves with
dust-tight fit in a circular groove 10 formed in the frame in the usual manner, and
said head 6 carries a hollow hub 11 which turns in a box 12 carried by the frame.
The hollow hub 15 of the head 7, and which is of sufficient diameter to serve as the
inlet for the material to be separated, turns in a box 16, and makes a close working
joint with the end of the feed spout X.

page_text: G is a cylindrical basket of wire clot' or other suitable foraminous material carried
by and revolving with said head 7. The material which is fed into the machine
passes through this basket and all substances which are too large to be fed to the
machine are retained thereby and can from time to time be removed through openings
closed by removable plugs 18, 19.
This basket also operates to check the pulsations of the air near the delivery end
of the feed spout. When these pulsations extend into the feed spout with full force
they retard the feed and blow out of the feed spout more or less of the fine material.
The arrangement of a screw between the feed spout and the pulsator or device which
produces the air pulsations overcomes this difficulty.
The gratings are preferably arranged in concentric circles C C¹ C² C³, as shown in
Figure 5. The grates or bars of each circle are arranged in two parts or halves, one
part being fastened to the head 20 and the other part to the head 21 Figure 1 and
if desired, the number and shape of the bars in the one part may differ from those in
the other part.
The bars of the outer circle are each preferably bent, as shown in
cross section in Figure 3, to give the air currents a direction approximately radially
outward, and the bars of the inner circles of gratings C¹ C² C³ may be either curved,
bent or be flat. The bars of said inner circles C1 C2 C3 extend from their respective
heads 20 or 21 nearly to the middle of the machine, but sufficient space is left
between the inner ends of said bars to permit of the free revolution of the wings 25,
(Figure 2) which carry the suction blocks or fans. The bars of the outer circle of
deflecting grates C however extend entirely across from the head 20 to the head 21,
and said bars are preferably held in frames secured on said heads, as indicated in
Figure 1. In the machine illustrated in the drawings all the gratings are driven
from the same shaft or hub, but each circle of gratings, may, if desired, be
constructed so as to be driven independently of all the others. Referring to Figure 1,
the hollow hub 27, on head 20, passes through the hollow hub 11 and turns in a
box 29, and the hollow hub 30 of the head 21 passes through the hollow hub 15, there
being a good space between said hubs 30 and 15, and turns in a box 32. A spiral
conveyor 34 on the hub 30 works the materials towards and into the basket G.
The suction or vacuum generators D D1 D2 D3, as shewn are formed as blocks d d¹ d² d³
which I term "suction blocks," are which are preferably curved on their rear or
suction side, as shown in Figure 5, but may be constructed in various other ways.
Said suction blocks d d¹ d² d³ are arranged and fastened in the following manner, on
the wings 25, (Figures 1 and 2) which are fixed on the sleeve 35, that is keyed to
the fast running shaft K; said wings 25 are provided with transverse arms 31, flanged
at their outer ends as shewn. On said arms 31 are fastened the concentric
rings 37, 38, and 39, and the centre plate 40. Said suction blocks d d¹ d² d³ are
each made in halves and said halves are fastened to opposite sides of said wings 25,
respectively between said wings and the aforesaid wings 37, 38 39. The innermost
suction block d³ is also made in halves, which are fastened to opposite sides of the
wings 25 and between the saine and said centre plate 40. Thus the several circles of
gratings C1 C2 C3 are arranged and revolve between adjacent circles of suction blocks,
and fans are arranged and revolve between alternate circles of gratings while the
innermost circle of suction blocks d³ and fans 62 64 revolve inside of the innermost
circle of gratings.
The pressure fans E E¹ E² are fastened to their respective rings 37, 38, 39 in
Figure 10. The outer fans E consist of main blades 45, which generate the swift
strong and sudden sifting impulse in combination with the outer deflecting grate C,
and said main fan blades are bent forward at a considerable angle from the radius to
effect the powerful outward rebound of the air currents which is a very important
factor in generating the desired sudden and powerful outward impulse of the sifting
current. These main blades may be curved concentrically at their front ends to cut
through the air with the least resistance. Each of the said main blades 45 is followed
by a group of auxiliary fan blades 48, certain of which blades are preferably bent
forward at a less angle than the main fan blades 45. The number of said auxiliary
blades may be increased or diminished according to circumstances, and said auxiliary

page_text: blades are arranged between the main fans 45 and the advancing side of the suction
blocks d. The purpose of said auxiliary blades 48 is to take up the air furnished by
the inner fan blades 55, 57 and the curved front face 60 of the suction block d³ and
deliver it in a strong outward after current of large volume between said main fan 45
and the advancing face of said suction block d. Said inner fan blades 55, 57 and
curved face 60 may each be either used singly as shown, or be followed or even
replaced by groups of fan blades as indicated at N Figure 6.
The air delivered by said fans 55, 57, and curved face 60 to the auxiliary fans 48,
and by said fans 48 sent through the sieve as a strong outward after-current of large
volume, blows the material which has been sifted by the main outward sifting current,
which was developed by the main fans 45, so far from the sieve that it cannot be
caught and brought back by the next inward current. Said fan blades, 55, 57 and
curved face 60, or their corresponding group of fan blades, are so shaped and
disposed in the machine as to provide the largest possible area for the out-flowing
air and to offer the least possible resistance thereto. Therefore, the passages between
the fan blades are preferably enlarged in the direction of the air flow and in this
manner not only does a large volume of air pass to the point of discharge and form
the outward after-current but said air also powerfully sweeps the under sides of the
fan blades and prevents the accumulation of fine particles of material in the interior
of the machine.
Suction blades 62, 64, auxiliary to the innermost suction block d³ may be fixed
between the centre plates 40 in any desired manner, or such auxiliary blades may be
omitted and the shape of the block d³ correspondingly changed, without affecting
materially the result.
In Figures 6, 78 and 9, I have shewn modifications of the arrangements of the
gratings fans and vacuum generators.
In Figure 6 I employ only two suction blocks F1 F2, preferably shaped, as shown,
and only two gratings J1 J2. L is the main fan to generate the sifting impulse.
M represents the auxiliary fans to generate the outward after current and N inner
blades which co-operate with the grating J2 to deliver the air to the said auxiliary
fans M. 01 02 are auxiliary suction blades fixed on the heads which carry the
blocks FF. The air currents generated by this machine agree in their general
character with those generated by the machine illustrated in Figures 1 to 5, and
operate the same process of sifting.
In the machine shewn in Figure 7, I employ only one set of suction blocks F3 and
one deflecting grate J³. L' is the main fan, M¹ the auxiliary fans for aiding in
generating the outward after-current, as hereinbefore described. P P are blades
revolving in the same direction as the deflecting grate J³, and either driven from the
same hub or separately as desired. I now prolong the suction blocks F3 backwardly
by plates f³, as shewn, whereby I increase and prolong the inward current and in 4
co-operation with said blades P P prevent the injurious action of return currents.
The machine shewn in Figure 8 is analogous to that shewn in Figure 7, but I now
replace the blades by the grating P¹, which revolves in the same direction as the
deflecting grate J³, and may be driven from the same hub, or separately, as desired.
The bars of said grating P₁ may be wider than shown in any desired degree. Both 4
of these machines generate substantially the same air wave as the machine shown in
Figures 1 to 5, and operate the same process.
Figure 9 illustrates a cross section of the preferred machine wherein the
arrangement of "pulsators" is in general similar to that of Figure 5. It differs
however from the last named machine in two respects. First the suction 5
blocks de d d d are lengthened out as shewn, to effect the control of the volume
and distribution of the air referred to above. Second, the centre of the machine is
open between the inner suction block and the hub, with only a single grating between
said suction block and hub. The opening in the centre is also shewn in Figure 8,
and the machines of Figures 8 and 9 both demonstrate the fact that the use of 5
pockets or cells open only toward the periphery but closed toward the centre is not
essential in this machine,

page_text: In each of Figures 5-9, I have indicated the direction of the air currents and
approximately their strength by arrows on one half the figures. The distribution of
the air currents is the same on the other half of the figures, but the arrows are there,
omitted to permit clear representation of the parts of the machine.
The machine operates as follows:-
The material to be sifted, having been fed through the chute X works into the
basket G and falling thence is worked by the spiral blade 75 Figure 1 into the
annular space between the deflecting grate and sieve. Now the long and strong
inward air current clears the sieve of adhering particles of the material and brings a
large volume of air into the machine. A certain proportion of this air is crowded
upon and rebounds powerfully outward from the main fan blades 45, developing a very
strong swift and sudden outward current which drives the finer particles of the
material through the sieve. The remaining part of the inbrought air flows freely into
the interior of the machine, as described, and to the auxiliary fans 48, between the
said main sifting fans 45 and the front side of suction blocks d, and is here expelled
as a long and strong outward after-current, blowing the sifting particles far from the
sieve. Then follows the next inward current, and so the cycle repeats itself con-
tinuously all around the sieve. The aforesaid inward and outward currents may be
considered to be due to the crests of high pressure and the hollows of low pressure of
an air wave of peculiar nature, which is produced by my apparatus and propelled
around the sieve a wave which I believe to be essentially unlike any heretofore
generated in sifting machines.
The efficiency of this apparatus depends upon the facts that the machine is so
constructed that there are open spaces in the interior which are connected together
laterally in such manner that the inwardly drawn current or volume of air has
sufficient room and therefore does not generate return currents which would greatly
reduce the volume of inflowing air and impair the effect of the inward current; that
the wave generator contains or is combined with a plurality of vacuum making
devices arranged concentrically within and successively behind each other, so that the
inner vacuum making devices successively act upon and increase or maintain the
inward current previously generated almost to the very instant when the next pressure
blade or device generates the next strong and sudden outward sifting current; that
the sifting impulse generator is succeeded by plates or groups of fans which generate
a prolonged and strong outward after-current which projects the sifted material far
from the sieve; that the wave generator is so opened on the interior that the devices
for said outward after-current get their air from the inward current, thereby preventing
the crowding of the incoming air and aiding to maintain the inward currents; and
that the air which passes from the inward currents to the outward after currents, as
aforesaid, sweeps under and keeps the inner surfaces of the blades thoroughly clean
and prevents the accumulation of fine dust in the interior of the wave generator.
The strength and velocity of the sifting current are greatly increased by the
movement in opposite directions of adjacent alternate inner gratings and inner
pressure blades, and especially by the construction of the apparatus in such manner
that a part of the inward current which is developed and controlled by the successive
vacuums rebounds and deflects outward with immense velocity and powerful sifting
effect. The intensity and force of this rebound are greatly increased by the aforesaid
movement of the inner gratings in a direction opposite to the movement of the inner
pressure fans, for the effect of these opposite motions is that the incoming air is
deflected and impelled in a direction opposite to that of the fan blades which generate
the sifting impulse and the air encounters no resistance until it is actually upon the
said fan blades. The consequence is an extremely powerful outward sifting impulse
or current following almost immediately upon the stoppage of the inward current.
The grate which is arranged inside of the path of the blast fan and suction block
shifts the air in a direction opposite to that in which these parts rotate, that is to
say,
it moves the air from the suction space in advance of the blast fan or blast
generator to the blast space adjacent to the same, and this is true whether the grate

page_text: rotates in a direction contrary to that of the blast and vacuum generator, as shown,
or whether it rotates in the same direction but at less speed, or whether it is
stationary. This shifting of the air inside of the path of the blast and vacuum
generator in a direction contrary to that in which these devices rotate prevents the
formation of under currents in the suction or vacuum spaces, it also prevents the air
from rotating with the speed of the pressure fan or fans inside of the path of the
latter and it increases the blast effect.
Any suitable driving mechanism may be used but I prefer a mechanism which
permits of the variation of the speed of the pulsator or wave generator while the
machine is running and irrespective of the speed of the deflecting grate and sieve.
Several suitable driving mechanisms of this kind are shown in the drawing. The
mechanism which I regard as most desirable is shown in Figures 11, 12, 12 and 13
and is constructed as follows:-
A shaft 80 provided with tight and loose pulleys 801, 81 and driven from any
suitable source of power carries a cone 84 and driving pulleys 85 and 86. A half
turn belt 88 drives from said pulley 85, a worm 90 which meshes with a worm
wheel 91 on the hub of the rotary sieve B, thereby imparting a slow rotary motion
to said sieve, usually about ten revolutions per minute. A belt 95 drives from the
pulley 86 a pulley 98 fixed on the hub 27 of the gratings. A cone 100 is arranged
with its axis parallel with that of the cone 84 but inclined in the opposite direction
and is driven from the latter by an endless belt 101 which can be shifted axially on
the cones, so as to increase or reduce the speed of the driven cone and shaft and of
the pulsators driven therefrom. This belt is shifted by any suitable belt shifting
device, for instance, by that shown in Figures 12 and 13, which consists of a
shipper 106 operated by a screw 107 and guided on a rod 108 which is secured at its
ends in lugs 109. By turning the screw by means of its hand wheel 107* the shipper
is moved in one or the other direction. The bearings 110* of the shaft 103 are made
adjustable toward and from the shaft 80 for instance by wedges 110 connected to an
adjusting rod 111, so that by adjusting these bearings and the shaft supported
therein toward and from the other shaft the tension of the belt running around the
cones can be regulated. A pulley 102 fixed on the shaft 103 of the driven cone 100
drives a pulley 105 on the fast running shaft K of the pulsators or fans and vacuum
generators. By shifting the belt 101 the speed of said fans and vacuum generators
may be varied without changing the speed of the sieve or gratings.
The pulleys by which the sieve, the gratings and the pulsator are driven are of
such relative sizes as to normally develop proper relative speeds in the pulsator and
gratings and the further regulation of the velocity of the pulsator is obtained by the
variable speed driving gear consisting of the above described cone gear or some other
suitable mechanism.
In the variable-speed driving gear mechanism represented in Figure 14, the cones
112 and 113 are connected by the belt 114 as in the first described construction but.
two belt shippers 115 and 116 are employed which are attached to an endless belt 117
running around guide pulleys 118. Hand ropes 119 are attached to the belt at con-
venient places. By pulling one or the other of these hand ropes both shippers will be
moved in the same direction, thereby shifting the belt on the cones and changing the
speed of the pulsator correspondingly, as the driven shaft is connected with the
pulsator.
In the variable speed driving mechanism shown in Figure 15 the main driving
shaft 120 carries a bevelled friction disc 121 which drives the bevelled friction
pulley 122 on the counter shaft 123, which latter is arranged at right angles to the
driving shaft. This counter shaft is provided with suitable pulleys, not shown, for
driving the sieve and the gratings. The disc 121 also drives from its flat face a flat
faced friction pulley 124 which is mounted on a shaft 125, so as to be capable of
movement lengthwise on the shaft while being compelled to turn therewith. The
shaft 125 is provided with a pulley, not shown for driving the pulsator. The
pulley 124 can be shifted on its shaft toward and from the centre of the disc 121 by

page_text: an arm 126 which engages with the hub of the pulley and is moved by an adjusting
hand screw 127. The arm 126 is guided on the frame 128 in which the adjusting
screw is journaled. By moving the pulley toward and from the centre of the disc
the speed of the pulley and of the pulsator driven therefrom is correspondingly reduced
or increased.
The sieve and the gratings may also be driven by variable-speed driving mechanism
although this is not ordinarily necessary.
It is not necessary, although it is convenient, to have two diametrically opposite
wave generators as shown but only a single one may be used, or more than two may
be used, as may be preferred.
The shape of the inner deflecting grates is not material and may be changed in
various ways, as well as the construction of the suction blocks, which latter need not
have the form of blocks but may be constructed in the form of chambers, or otherwise,
as may be most convenient.
While I have described and shown various machines whereby my invention may
be practised I do not wish to limit myself to the same as the mechanical appliances
may be changed in many ways without departing from my invention.
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 process of sifting granular materials herein before described, consisting in
first clearing the sieve by long and strong inward currents of air of large volume, then
propelling a part of this air in a strong swift and sudden blast outward through the
sieve, whereby the finer particles of the material are sifted through the sieve, and
following this blast with a long and strong outward after-current of the remainder of
the air whereby the sifted particles are blown far from the sieve and out of reach of
the next inward current and causing said several currents to travel successively over
all parts of the sieve.
2. A sifting machine embodying a sieve, one or more vacuum generators or suction
devices whereby a copious current of air is drawn inwardly through the sieve for
clearing the sieve from adhering particles, one or more main fans or blast devices
whereby a swift sifting blast is generated which drives the fine particles outwardly
through the sieve, and one or more auxiliary fans or blast devices whereby a long and
strong outward after current is generated which blows the sifted particles out of reach
of the next inward current.
3. A sifting machine embodying an enclosing sieve, a rotatable deflecting grate
within the sieve, one or more rotary suction blocks or vacuum generators and one or
more rotary main fans within said grate and one or more rotary auxiliary fans
arranged between the main fan or fans and the suction block or blocks.
4. A sifting machine embodying an enclosing sieve, a rotary blast and vacuum
generator arranged within the sieve, and an air shifting device or grate which is
arranged inside of the path of said blast and vacuum generator and mounted indepen-
dently thereof, either stationary or so as to rotate with less speed or in a contrary
direction, and which operates to shift the air in a direction contrary to that in which
the vacuum generator rotates.
5. A sifting machine embodying an enclosing sieve, a rotary deflecting grate
within and adjacent to the sieve, a rotary suction block or blocks and a fan or fans
within said grate, a rotary grating within said suction block or blocks and said fan or
fans, and an air chamber in the centre of the machine.
6. A sifting machine embodying an enclosing sieve, a rotary air wave generator
arranged within the sieve and producing blast and suction pulsations of the air within
the sieve, and a screen which is interposed between the feed spout and the pulsator
and which checks the air pulsations before they reach the feed spout.
7. A sifting machine embodying a sieve, a grating or air shifting device arranged
within the sieve, a rotary pulsator also arranged within the sieve, and producing

page_text: blast and suction pulsations of the air within the sieve, and a variable speed
driving mechanism whereby the pulsator is driven and by which the speed of the
same can be changed independently of the speed of the other moving parts of
the machine while the machine is running.
Dated this 16th day of November 1907
HASELTINE, LAKE & Co.,
45, Southampton Buildings, London, W.C., Agents for the Applicant.