Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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Backclround
In products comprising a nun~er of individual in-
gredients i-t is frequcn-tly desirable -to premix these inyred-
ients sufficiently ~o provide a uni~orm slurry which is suit-
able ei-ther for immediate use or for further processing in
other mixing apparatus. Premixing apparatus for this purpose
may include a cylindrical housing with a centrally disposed
rotatable shafk. A nur~ber of rotor blades are mounted on the
central shaft so that they extend outwardly toward the sur-
roundiny housing and a number of cooperatiny stator blades
are mounted about the ou-ter wall of the cylindrical housing
so that they extend inwarclly toward thc sha~t in~erdiyitat-
incJ ~Jith thc~ rotors. :Cn opcratiorl the central shc~t rota~es
causing the atkach~d rotor blades to pass between the stator
blades thereby mixing and beating a mixture of ingredients
introduced into the housing causing these ingredients to
form a uniform slurry.
In prior art devices of this type the individual
rotor and stator blades consisted oE elongated subskantially
bar-like mer~bers oriented at a uniEorm ancJle to the horizontal
plane such that when the shaft rotated the rotors impelled
the ingredients to be miY~ed downwardly within the cylindrical
housing. In such an appara-tus centrifugal force causes a
vortex to form about the central shaft and the ingredients
tends to ride up along the~outer wall of the housing where
they are incomple-tely mixed~ If such apparatus is filled to
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capac~ y, mat~ricll carl spill ou~ oE thc housi.ng. With such
priorart premiY.crs inyredicnts introduced i~ O the top of
the housiny o:Eten failed to mi~ adequLItely within an accept-
able period of mixiny ~cime because of the lack of circulation
of the ingredients within -the housing.
In commercially useablc premixing apparatus of the
t~pe described above, it is important to provide thorough
mixing of a maximum quantity oE ingreclients in a minimum
time without the incorporation of air into the mix-ture. Air
should be excluded during this premixing st~p so that controll-
ed amounts of air may be introduced into the mixture in later
processincJ sl:eps. "
With pri.or art apparal:us tllo usor hacl t:o ~hoos~ be-
tween two equally unCatis~actor~ alternatives. ~Ie could achieve
adequate mixing in a relatively short time if the cylindrical - ;
housing was filled to only approximately 80% of its capacity
or he could fill the housing to its capacity which would re-
quire mixing times up to five times as lony. Since such lony
mixing times were unacceptable most users chose to utilize
only 80% o:E the rated capacity of their e~uipment. Because
of the large vortex about the central shaEt and the tendency
for material to clim~ up along the outer housing wall, such
prior art apparatus also tended to introduce varying amounts
of a ir lnto the s lurry .
~he above 6eiicie~ cies oi the prior art appara.-ls
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are overcome in the present apparatus by utilizing an improved configuration
for the rotor and/or stator blades of the premixer. The use of rotor and/or
stator blades of the inventive configuration results in better overall cir-
culation of the ingredients introduced into the cylindrical housing and pro-
vides more thorough mixing of a larger quantity of material within a far
shorter time than prior art devices as described above while avoiding the
introduction of air into the premixed slurry.
Summary of the Invention
The invention provides mixing apparatus including a housing having
a central axis, a rotatable shaft disposed along said central axis and
adapted to rotate in a predetermLned direction; and a first and second group
of interdigitated members each member having a leading and a trailing edge
when sald shaft rotates ln sald predetermLned dlrectlon, a longltudlnal axls
and Elrst flnd second ends, each of sald fLrst grouy oE members belng attached
at sald flrst end to sald rotatable shaft and extendlng outwarclly from sald
rotatable shaft toward said housing and each of said second group of members
being attached at said first end to said housing and extending inwardly from
said housing toward said shaft, and all of said members of both said ~irst
and said second groups of members comprising shaped men~ers, each of said
shaped members including first and second longitudinal portions ad~acent
respectively to sald first and second ends, sa:Ld Elrst portlon having a first
lateral axis passing through sald longltudinal axis, sald flrst :Lateral axls
sloplng upwardly from sald leadlng to sald tralllng edge, and a second por-
tion having a second lateral axis passing through said longitudinal axis,
said second lateral axis sloping downwardly from said leading to said trail-
ing edge, said first and second lateral axes forming an acute angle.
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Description of the Drawings
Figure 1 is a partially sectional side elevational view of the
premixer of this invention.
Figure 2 is an enlarged side elevation of a portion of Figure 1.
Figure 3 is a cross sectional view taken along plane 3-3 of Figure
1.
Figure 4 is a cross sectional view taken along plane 4-4 of Figure
2.
Description of the Invention
Figure 1 shows a pre-mlxing apparatus utilizing the improved rotor
and stator blades of the present invention. The apparatus 10 includes a
substantially cylindrical housing 12 and a centrally mounted rotatable shaEt
14. Means, such as a motor and assocLated drLve train, which are not shown
but are welL known ln the art n~ay be prov:Lded to turn the rotatabLe ~hclft L4.
A n~lmber oE ~tator blades :L6 are attactlcd to cyllndrlcal houslll~ 12 at a
first end 16a by welding or other suitable means and extend inwardly in a
substantially horizontal plane in the direction of shaft 14. The inner ends
16b of the stators 16 are positioned a short distance from the rotatable
shaft 14. A number of rotors 18 are attached at a first end 18a to the
rotating shaft 14. An aperture 11 having the same inside diameter as the
outside diameter of
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shaft 1~ ma~ be fo.~ned in t}le end l~a oE each rotor 18 and
the wall of thc aperture lL may be attaciled to shc~ft 14 b~
weldin~ or o-ther suitclble mcans. The rotors 18 extend out-
t~ardly rrom the shaft 14 i.n a substantiall~ horizontal plane
in the direction of thc housing 12. The outer ends 18b of
rotors 18 are spaced a short clistance from the housing 12 to
permit rotation.
- As can best be seen in Fiyures 2, 3 and 4 each of
the stator blades 16 includes a first longi-tudinal portion
20 which is adjacent to housiny 12 and a second lonyitudinal
portion 22 which is spaced from the housing 12. As best
seen in Fiyure ~ the lateral axis 21 o~ t:he firc,t lonyitudinal
portion 20 is or.i~ntccl at an ang:L~ with rQsp~ct: to a horiY,on~
tal plane 13 pa~s:incJ throucJh th~ stator 16. The :Lateral axis
23 of the second portion 22 of stator lG is oriented at an
approximately equal and opposi-te angle wi-k~ respect to the
horizontal plane 13. Within a central portion 25, the stator
blacle 16 chanyes from the first to the second orientation
with respect to the horizontal plane 13.
A st~tor blad~ 1~ as described abovQ may be ~ormed by
bending a sinyle member o~ substantlaLly rect~ngular cross section
about its longitudinal axis until the desired orientation of por-
; tions 20 and 22 is achieved, by casting the member in -this shape
or by fixedly attaching two separa-te parts constituting respectivel
portions 20 and 22, Eor example, by t~elding these portions toge-ther
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within th~ ccntral por-tion 25 to fo.~n a unitary rnel~er. In
either case the la-teral aY~es 21 and 23 of portions 20 and 22
of the completed ~-kator 16 fo~n an acute angle which is pre-
ferably bisected b~ the horizontal plane 13. It has been
found that an angle o~ approxima-tely 40 between the lateral
axes 21 and 23 WhiCIl iS bisected by the horizontal axis 13 so
that axes 21 and 23 are each oriented at an angle of 20 with
respect to the hori~ontal axis provides a-stator of superior
mixing characteristics.
As can best be seen in Figures 3 and 4 individual
skator blades 16 may be tapered from a maximurn width at the
first end 16a ~hich ic: attached to the housinc~ wall 12 to a
minim~n width at th~ sccond ~ncl 16b which is adjacent to thc
rotatiny shaft 14. This taper provides a maxim~n widkh at
the point of attachrnent to the housing 12 and provides a
lesser width at the end 16b spaced froTn-khe housing. This
taper results in a decrease in the vertical spacing between
the rotors and stators, thus allowing more mixing elements
in a given height of unit. This increases the mixing.capa-
~0 city of the unit and at the same t.ime gives ma~irnum strength
to the blades. It has been found that an angle o~ taper of
approximately 2 along each of the longitudinal sides of the
stator 16 provides a superior stator from the point of view
of both strength and element spacing.
Fiuu~es ., 3 and 4 also sllow th~ rotor memb-r- 18
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in detail. The rotol- blade.-, :L~ includc a first end 18a having
a groovc 11 :Eormed therein. The groove 11 has substantially
the same insid~ ~iametcr as the ou~sicle diameter of cylindrical
shaft 14 so that rotor member 18 may be fixedly attached to
shaft 14 by weldi}lg or other suitable means along groove 11.
Rotors 18 exkend outwardly from the shaEt 14 in a subs-tantially
horiæontal plane such as 31 in Figure 4 terminating in end 18b
which is adjacent to, but spaced from, the housing 12 to permit
rotation of the rotors 18 when shaft 14 is rotated.
The rotors 18 include a first lon~i-tudinal portion
30 which is adjacent to end 18a and a second longitudinal por-
tion 32 adjac~nt to end 18b and located at the outcr cncl of
the ro~or~ ~5 in the cca~c o~ stator 1~ the ~irs~ porti.on 30
is slanted so l-hat its lat~ra~ axis 34 orms an anc31e with
the horizontal plane 31. The second por-tion 32 is slan;ted
in a direction opposite to portion 30 with respect to the hori-
zontal plane 31 so that its lateral axis 36 ~o.rms an anyle
which is opposed to and preferably substantially equal to the
angle formed by the lateral axis 34 of the ~irst portion 30.
It has been found t~lat providincJ an ancJle o:E approximately ~0
between the lateral axes 3~ and 36 which is approximately bi-
sected by the horizontal plane 31 results in a ro-tor of
superior mixing qualities.
As in the case oE stator 16, the rotor 18 further
includes a central portion 28 in which the rotor lateral
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axis chancJes from ~he orierltcltion in the first portion 30
to that in the second po~tion 32. A'; in the case o~ stators
16, rotors 18 may he formed Frol~ a sinyle bar me~ber by bend-
iny the mernber to provide the desired confiyuration by cast-
ing a member in that confiyuration or by fixedly joining two
separate mer~ers comprising rcspectively por-tions 30 and 32
in a manner known in the art, such as welding, within portion
28 to forrn a unitary member.
As can best be seen in Figur~s 3 and 4 the rotors
18 are tapered from a maximum wi.dth at end 18a where they are
attached to shaft 14 to a minimurn width at their outer end
18b. As in the casc of stators 16 this res~lts in a rotor
of sup~rior str~ngth whilc permi.ttlncJ a maxi.mum n~er oE
rotors and s~ators to be Inoulltecl with:in tlle ava:Llabl~ space
in the premixer apparatus. As in the case of stators 16, the
rotors 18 are tapered at an angle of approxirnately 2 along
each longitudinal side oL the rotor to provide a superior
rotor configuration haviny maxim~un width and therefore strength
a-t their point of attachment to shaft 1~. rraperiny both the
xotors and stators permits th~ :incl.usion of an oxtra set oE
blades and can provide up to 25% better rnixiny.
As can best be seen in Figure 2, the rotors 18
interdigitate with the s-tators 16 as they are rotated by .
sha-ft 14 so that the smaller second por-tion 32 of the rotor
passes over the laryer first por-tion 20 of the stator. Por-
tion 32 of each rotor 16 slants downwardly at a first anyle
approximately equal and opposite -to the anyle ~t which the
2~ first portion 20 of the stator is orien-t~d upward with
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respect to ~he horizontal axes passing t~oucJh them. The
shaft 14 rotates in clockwise direction as sho~/n by arrow 50,
Figure 3, so that the rnaterial -to be mixed tends to be im-
pelled down~lardly by portion 32 of the rotor across the sloping
surface of p~rtion 20 of thc adjacent stator in areas adjacent
to housiny 12 yiviny rise to the downt1)ard circulation of ma-
terial in this area shown by arrows 52.
The first portion 30 of rotor 18 passes over the
second portion 22 of the stator. Portion 30 of the rotor,
slants up~lardly at an approximately equal and opposite angle
to the dowm~ard slope of stator port:ion 22 with respect to the '
horizontal axes passiny throucJh ~'hem. ~5 the shaft 14 rotates
in a cloc~wis~ directlon a~ sho~ln 'by ~;'igur~, 3 the mat~rial to
be mixed is impe~led upward aloncf shaft 1~ by rotatincJ rotor
' 15, portion 30 across the under surface of stator portion 22 giv-
ing rise to an overall upward movernent of material along shaft
14 as shown by arrows 52. The combination of these two mo-tions
provides an overall circulation of the material to be mixed as
shown by a.rrows 52 and provides sup~rior mi~incJ capabllity
without th~ incorporation o~ a:L.r into th~ slurry.
By crea-ting the circulation shown by arrows 52 the
improved rotor and stator configuration offsets the tendency
of the ma-terial being mixed to climb up -the housing wall~
. The upward force along -the shaft 1~ also minimizes the tend-
ency of the material to form a vortex along the shaft 14.
By preven-ting' material from riding up -the housing wall and
decreasing the vortex adjacent to the ,shaft 14 the improved
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apparatus cJreatl~ clccreases tl-le anlount o~ undcsil-clble ~ir
wnich is in-troduccd in~o the ~ c;redicn~s during premixing.
By providing a ~encral ci.rculati.on of mcltcrial within housing
12 as illustrated by arro~s 52 of Figures 1 and 2 all in-
gredients move throuyh the various levels within housing 12
and are thoroughly mixed off-settincJ -khe tcndency found in
prior art apparatus ~or material to remain at the top of the
housing and not be mixed with other inyredients.
Although the above preferrecl embodiment has been
described as utili~ing both stators and rotors of applicant's
improved configuration considerable improv~ment over prior
art premixers can be achieved i~ either the .rotors or l-.he
sta~ors u~ilize thc improved con:E.igurat:ion while the other
members are made ln the prior art bar-like shape. A greater
1- 15 improvement is realized if the rotors alone are made in the
improved configuration rather than the stators alone being
made in this con~iguratior- but some improvement is realiæed
in either case. If desired only some o~ ~le rotors and/or
stators can be made in ~he -improved coniguration while
others are made in accordance witll the prior art. This
again will result in improvement ove.r prior art apparatus. .
In prior art premixers of the same size using con-
ventional rotor and stator blades only 800 pounds of material
to be mixed could be loaded into a mixer rated at 1,000 pound
capacity if mixing was -to be completed witllin 2-1/2 minutes.
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If a full 1,000 pound~ wae placed in the housing 12 of the
mixer a ~ubstantially longer period wa~ required to achleY0
adequate mixing in prior art mixer3~ By co~traet, the im~
proved premixQr of thi~ invantion utilizing applica~t~s im~
proved rotors and stators provide~ ~uperior mixing of loads
of up to 1,000 pounds, or full rated capacity, ln ander 2 minut~
with no sub~tantial incorporation of air i:n the mixture.
The improved c~rculation provided by the conflguration and
arrangement of rotor and ~ta~or blade~ in this premixer al~o
prevent~ dry material~ from remaining at the top o~ th~ mix-
ing conSainer and cause~ tham to m~x in with the remainder
of the mixture.
Although the present in~ention has been descr:Lbed
in oonjunct;Lon with preferred embodiments, lt i~ to b~
under~tood that modiflcations and variations may be r~sorted
to wlthout departing from the spirik and scope of the ~nven-
tion as those ~killed in the ark will readily under~tand.
Such modif~catione and variations ar~ considered to be within
19 the purview and scope of the inven~ion and appended claim~.
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