Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
,~A 0222093~ 1997 ~ 12~ t~r ~ ,7,
WO 96/3S507 ~ 96101l2
I~T~NAT. ~v~,~c~
The present invention relate-c to i~ternal mixers which are used for
mixin~ h~ of compoond incorporating ~i~ferent componentr which
mu~.t be mixed tog ~th~r to provide a h~ 1 mixture,.
Various d~c~ s o~ internal mixers ~.re currently in u~e in for
ex~mple the rubber ~n~ plas¢ic~ industrie~ to produce compound~ for a
wide rallge of product~ ~or e~cample tyres, electrical lnsulation plastics
-~d the li~e~ In such mixerr., cor~ o~ ~lt~ such as r~b~er, ~Illerr.,
reinforcing agent~ ql additiver snd curatives are inl~ .ced into a
m~xing ~hu~nl through an inlet r~ ~ le~ding to an G~e,.i,.~ in a
wa}l of tlle ç~ I-er. At le~st one rotor turns ~itbin the chamber, tlle
rotor ~upporting projections which ~xtcnd toward~ the internal wall of
the t'h~mb~,
The rotor hag to E.L.ru~... a number of functions. Fir~tly bulk
matel;~ls, for ~mrle large pieces OI rubber, must be dr~n i~tn the
chamber and divided into ~maller piece~ or ~t lea~.t r~-r~ared Seçondly,
the t~er~lure of the m~terial within the rhzvnbcr m~st be inc~ ~ s e ~ by
the QpFli~stlrl. of ~ e~ and ~trnin~. The te~nl,er~lurG il.C-e~ f i~
primarily a result of the stre~s ~pplied to the material through contact
with the internsll surface~ of the mixer, that is the ~urfaces of the ~h~rnher
wall~ and of the or each rotor. The major crlteria in applyin~ ~tre~g are
UB~I~E SHEET ~RULE 2~
12 NOV '97 08:47 . ~ ---CA 02220935 1997-11-12 P 7 ~~'-~
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~o 96n55~7 P~ CIO1128
firstly that the lln~t...;dl is in contact ~Yith r"~h;ne surf~ces ~nd secondly
that there is relstive moYement b~ the material and the surf~ces. vT~irdly, the sep~rate components of the mixture mu~t be dfslriLht~J
throughout the ~ e o~ the ch~mber in order to achieve a fine
lr;Lul;~._ of ~e vsrious ingredients. ~or ex~mple, filler ~g~l ~erates
~ust be d;~ , ' and l~roken do~ into a desired fine t~ ' rle ~ize and
then dist~ibuted through the bulk of the compoul~d in t~e mixer.
Fo~ rth~y~ the mL,;ed compound mu~t be plasticized in order to achieye the
r~ ;.iLe final r~eolog~r~ u~ s. ~inally, ~11 of the fully~ mixed
compound must be discharged from fhe Inixer thro~gh ~n ~lltlet whicb
can be opeoed 1~ the c~n-b~r walL
Given the dilie.~ unctions which the mu~er must perform
during a sihgle batch mixin~ operation, snd given tlae ~.h~ s in the
properffes of the mixed materi~l during the course of a batch mixing
ope}-ation, the design of inter~al mixers must be such th~t adequate
perforD:lance i~ ~chieved in all the phases o~ a mixing operation. As a
result it is alwayi n¢ccssary to compromise on certain features of the
de~ign of an irlternai mixer to ensure that the o~çr~ e.ro~mance is
acceptsble. By way o~ example, inter~al mixers with interlocking rotors
are widel~ used in the rubber industr~ such mixers, t~o rotors are
arlan~ed side by s~de within a ~ingle chamber with their axes of rotation
parallel. The rotors comprîse proiections or nog~ supported on gonerally
'P~;'~'''~'!~A ,.0 2r2 2~,0~9, 3 ~i. ~,_.1 ~,~ .
wo 96/35S07 ~ ~1128
~ylindrical shaft~, the radially outer end of the nog~ on one rotor
ex~ to a short distance from the ad~acent inner wall of the cavlty
and a short distance ~rom the surf~ce of the shaft of the other roto~. The
rut,~Liû., of the two ~otors i8 synchrohiged to en~ure that the~no~s on one
rotor do not cor~t~ct the nogs on the other. Wlth an ihterl-~ckln~ rotor
mlser of this type, a single batch miXinX operation ~nvolves three separste
phases. Firstly~ the rotors serve to ingest the ~ate~ i~ls into the ca~ity, to
distr~bute tbem around the ch~mber, and initially to ~ AtP the
~attr;~ls by mean~ of the ~ n~ ~ction taking place bLI.. ~ tbe
rotor~. Secon~ly, a8 the materi~l i8 heated and so~tens, it begins to flow
o~er ~e radially outer ed~es of the nogs, that i~ through the ~p ~etween
the nogs and the chamber ~valls. Becaus~ o~ the lenge~ and width of this
gap, the material is subjected to substantial ~ r ~ir.r,nl ~nd ghear slr~ in;
and stralin~, thereby achieving good di~L~ ~;vll~ while the disposiffon of
the nogs on the roton prov;des a degree of circulatory flow ~vithin the
rh~ l~er, thereby ~s;~ g with the distributive ~ inE, Thirdly, the
rotors ser~e to propel the cou~uu~d do~nward~ 3nd outwards throu~
the outlet ~hen a discharge door is opened at the end or the mixing cycle.
The ~,unf~ r~tion of the nog~ on the ro~ors of an internal m~xer
with interlocking rotors has been e~olved o~er many year~. A desi~h
which i~ Chr. e~ in genoral use Is de~cribed in E~rope~n Patent
Specification 0170 397. In that desl~n the rotors are ~epar-tLd by a gap
.SU3STITUIE SHEET (RULE 2B~
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W 096/35507 r~ 5/01128
which is l~rge enough to e~ure that snffir;~nt space ~ available to ingest
the msterlal r~l.,Li~rel~ easily, but which is smsll erc!-~ to ensure that ..
adequate ~ ;L--Q1 and ~hear ~ 5 a~d strain rate can ~e spplied to
t~e material in order to obtain di~ Di~ c mi~cin~ of it~ cG~yu"c~1s~ The
larger tlle rotor ~ap, th~ greater the in~e~tion but the less the di~ a;vl~
Accordi~gly the n I t- of the rotor gap must be a compromise given the
competing requireq~ t~ It i5 also necP~Q~y to ta.ilor the ~1 o~l of
o~ ti~ll of the r~sr~ e, to the particular 6tage oî the mixing cycle, for
~mplr to reflect the physical and c~ç~ J~ ion of the ,.,~l~rl~l.
This can inYolve the varia~le~ of speed of rotation, the pressure with
which msterlsl to be i"~- ~tcd jB forced into the ~ er opening, tbe
temperature of the ~.~iA1urc and the time forwhich the mixture is wu~l~cd.
Of th~se ~rariables, tem~r~r~ control is generall~ the most significant.
It is therefore hecA-~Qry to desi~ internsl mixers in ~uch a way as. to
ensure that the required levels of ~yt~rclon~l and shear stres~es, strsins,
and t~ er~ture are achieved at all st~S~eY of the cycle whilst ~je-~ing
minim---n cycle times. Given the ch~ngi~g rheological ~.u~e.li~s of the
mi~ture during the cycle, thesç factor~ camlot be readll~ optimised d~ring
all parts o~ the cycle Thus the design of the know lnternal ml~ers
represents a set uf care~ully e~tab1;shed compr.:
Known internal mi:~ers are conventionaUy drnren in ~ single
direction during the normal mixing proces~. ln mixers with two contra-
~. ~'L ~
. . _
222~93s 1997
wo 96/35~07 E ~ 610l1
rotating rotors, the lç~ edgos of.the two rotors are geometrically
"h~ y i~P~ l l'hu~ each rotor subjects the material to be miXedto the same mixin~ action. It is belie~ed Shat in some Li~ ' it has
~een posF~lr to r.i-c~,e the di,~i-t; .. of rotor movement to 'ra~ ts~te the
release of j5~mTne~ roton but it is not believed that iDternal mixers haYe
e~er been or,~ tL~l in a nûrmal mixing cycle ~vhich indudè~ phases
during the yr~Ce51 0~ miXiDg a ~ingle b~tch during ~vhioh the ~ ecli~. of
rotaffon of the rotor~ is r~ ed.
lt is an object of the ~nJF ~ t i..~c~.ti~n to pro~ide ~n improYed
interual miger.
ACLU~a~ to t~e ~ t in~ t;u.., there is pro~idcd arl internal
mixer cou~r ;-~g at least one rotor supported to rotate about a
predet~....~cd axis within a mixing chamber, at least one projection
mounted on the or each rotor snd RY1Pn~ tow~rd~ an internal wall of
the chamber, ~nd means ~or rotating ~he or each rotor about jts axis, th~
~aid at le~ one rotor defining projection edges of dir~1_~.t geometries
and bei~g rota~ed ~uch that each of the said edge~ us a leadin~ edge is at
lea~t part o~ a mi~hg q~cle, whereby ,..~t..;al within the chaml~er is
s~bjected to different mixing actions ~y the edges of di~rL~ .t ~eometrie~.
In one embodiment of the pre~ent ~DVention, thc rotatlng mesns rotates
-., the or es~ch rotor in either dir~ ~-- about it~ axi~, and the o'r each
proJection i~ formed ~ueh that the ~hapes of its le~din~ and ~r~iling edge~
SU8S~I~U~E SHEFI (RULE 26) .
12 NOV '97 08:49 .. CA 02220935 1997~ 12 P. ll
~o 96n5507 r~ "01128
are ~ .,t, where4y the mixiog action to which material within the
rl~a~hf~ ig l~ubJected is a function of the direction of ~.Jt2.1iu.. of the rotor.
The inventlon al~o proYides a method hr operatin~ an iDte~nal
.ml~er comprising at least one rotor ~ ~~ 1 to rotate about a
predet~ axi~ withln a chamber, and at lenst one projection
mounted on the rotor and e!x¢rnrl;n~ IU~ D an internal ~ ll of the
rl~hçr~ the or each projection, be~ng formsd such that the ~hapes of it~ -
in~ and trailing ed~es are differ~nt, wherein a ~atch of m~terial is
deli~ l to the cavity, the or ~ch rotor ls rotated in a first direction to
~ubject the material to a fir~t mixin~ progrnmme in which the mixing
action i~ to it~ initial con~ inn, and the di~ lio,. of rotation
of the or each rotor is revex~ed at le~st once h ~ubjec~ the material to st
least one furt~er mixing programme in which the mixi.n~ sction i5
appropriate to tbe condition of the material affer completion of the ilrst
mixing pro~r~mme.
In ~n alternative elnbor~ ert of the pre~ent invention, in which at
least one rotor is proYided ~efin;nE~ at lea~t two proje~;l;u.,s, the or es.ch
rotor i~ rotated in only one direction duri~g a mixing cycle, the l~ in
edge of s~t least one projection i~ relntivel,Y steep so as to grip material to
be ingested ~nd iorce it into the ch~mber, and the leading edge of at lea~t
one other projection i8 relatiYely le~ ~teep so as to encourage li~at~ l to
now o~el the radially outer surface of the projection.
"~A,~ ~Or ,2~2,~2~0 9 3 5 ~ 9 9 7
WO 96135507 ~ 6/01128
The ~ t invention i~ ~ased upon the realisation that in sn
internsl mixer it i5 the leading ed~e of the pro3ection which largely
determine~ the ~ixi~g action to which material within the rh~n her is
s~bjected. Thus by arrangin~ for the rotor to be re~ersible ~nd r~
the ~lir~-lion Or rotation of the rotor during the mixing of a single batch,
u~d perform~nce can be ~ e~ by d. i~ln~ the k~ g edge of
the projections when the rotor turn~ in one direction to be Dppropriatei. for
the condition of m~erials at one ~tage of' the mixing cycle, and d~
the leading edge of the projections when the rotor turns in the o~pG~ite
directloD to be ~ pri,-tt for the condition of the material to be mixed
at another stago of the mixing cyde. Altern3tively, in a double rotor
r~ e in which the rotors turn in only one dil cc~;u~ du~ng a ~
mi~ing ~cle, one rotor can have a leading edge which ensures rapid
in~ of material at the l~e~ g of :~ ~nixjng cycl~ and t~é othe
rotor a leading ~dge appro~ ute to a latel~ stage in the Dame mixing cycle.
1D a mar~ine with reYersible rotor di.~ io~., the rotor directi-,A
may be r~ DcJ two or rnore times during a single batch cycle~ for
eYs~nrlc to assist in ma~erial ~ jL~ or ~o ensure ~ood
disl,.;.~ion/distril: ution of in~çredient~ added to the c.~ .d durin~ the
course of the mixing cyde. Thus the designer can produce an i.~l~.. I
~nixer With chal~cteristic~ that in the prior art would ha~ve re~uired two
sep~rate mixers used ~equentially to proce~s a single batch.
' SUBS~llUI~ SHE~ (Rl)LE 2Bj .
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12 NO~ '97 08:50
CA 02220935 l997-ll-l2 P.13
W096~5507 ~ 96~1128
A first edge of the o~ each projection which i~ ehe ~- ~jn~ e~ge
when the rotor is rotated in one direction may be relati~ely steep so as to
grip ~-~t~ .l to be i~ d ~nd thereby ~orce mat~rial into ~he ch~n~_ ~
whereas a second edge of t}le or e~ch pro3ection w~icS is the l~,q~in~ edge
when the rotor is rotaffllg in the other dlr~,.liu~ i~ rolati~ y les9 steep ~o
as to encourage material to flow over the radially outer :-ur~ ~ of the
pro3ection, thereby providing for optimal ~xt~r~ion nO~v into the ~ap and
s~ear flow w~thin the gap. The first edge is thô !~ ng edge during ill~tl~
lo~ ge~inr and plasti~ ~ti~ and t~e second edge is &e l~r';"~
edge during a ~ubsequent stage in the mixing cycle It would of cour~e be
po~ible in a further stage of the mi~ing cycle to again reverse the
direction of rotatio~ of the rotor.
Thô fir~t leading ~dge may be inclined at an angle o~ les~ than-45~
to a rsdiu5 dr~n ~rom the axis of rotation. The small~l this angl~, the
~itC~.EiLr the surface o~ the proiection advan~in~ towards ~he material to be
m~xed. That steep edge may be provid~ with an undcrcut so as to
~o:~;L;~ grip introduced material and in addition could have sharp
co~ner880 as to a~sist in bre:lking up initially introduced ns~terials.
The or each projection ~n~y be proYidOd with in~lerit~tions and
d~ ~,,,sions thst sre sloped in the helical, axial or c;~ ~rcntial
cliG~ so as to impro~e material distribution. It ~vlll be ~ e~;..l~d
that in contrast to p~ior art mixcrs which during a mi~ing cyclO rotated in
lZ NO~ '97 09:06 CA 02220935 1997-11-12~ P-47 .~ .
,,' ,.' ~
only onc ~lir.,_liol~ it would 4~ pos~ible in ~ccordance with the p~escnt
invention to pro~ide projections ~IP~ ;ng sp~ce~ which are "de~d", th~t i~
to ~ay which are not ~wept out by tl-e flo~ of l,la~ vithin the mixelt
when the roto- tUrn5 in one direction, providi~g thos~e area~ a~e swept out
. . .
when the di~ectiop df rot~tion i~ ed.
The ~ in~ention i~ npplicable to a variet~ of intern~l mixer
;grc b~t is particul~rly applic~ble to mix~rs hAving fwo rotors locslted
with the nip between them beneatll ~ m~l~e~ial inlet a~d ~ove q mnterial
outlot, the rotor 5upporting interlocking projections sha~ed such that t~
e~rli"a edges of the proJections when th¢ rotors are rotnte~ to move the
.. . . . .
proje~-~ion~ down~ ds at the nip grip thntenal h~ luced thro~gh the
inlet, and such that tl~o leadin~ e~ges of the projections ~hen the rotors
are rotate~l to move the proje~tions up~Yards at ~he ni~ force mnteri~l
wit~i~ the chambe~ against the i~fernal wnll of the char~ber.
~ mbo~imehf~ of the present in~ention will now be descrihed, by
way o~ ox~mple, with reference to the accompanying dra~rin~s, in which;
Figure 1 ~ a Yiew from abo~e of t~o rotor~ of a con~ertion~l
internal ~i~er in ~vhich such rotors are arranged side b~ ~ide within a
mi~ing chamber;
Figure ~ 8ec~ iew Oh the line ~-2 of Figure l;
Figur~ 3 is a ~e on~l Yie~Y corre~pollding to that of Figure 2
-~howing the ingestion of material to be mixedt,
~ 12NOV '97 0EI:51 - ~ CA 02220935 l99i- ;; i2 ~~
WO 961~SS07 ~ 610~128
Figure 4 illustrates a later stage in t~le mixing process shown In
Figure 3;
Figure 5 ill~L~te3 the ~tructure of a~ alter~lative inter~lal mixer of
çonYpnti~r~ql form;
Figure 6 is a v~ew simil~r to that o~ Figure 2 but sho~ving
--~if; ~ s made to the .. . se -nn Or a rotor. in accordance with the
pre~ellt i--~_..t,o.-; and
~ igure 7 illu:~t~ at~ 5~ n the rotors of ~ rever~ible mixer
in whiçh each rotor ~as been ~nrlif~Ptl in the same mqnnPr a5 the rotor of
~igure ~i;
Figures 8 ~nd 9 ~ P~ti~Q~ly re~ ent rno~ifir~tion~ which ma~
be made to a rotor in accordance w~th the present invention; and
Fi5~ure 10 illu~.1r2.1.s in ..0~3 ~tion the rotors of a mu~er h ~hich
each rotor rotates in only ohe direction b~t the ~otors have ~een motlifi~l
in dif~erent ~ays such that the rotors ~ubject material ~vithin tbe mixer to
.lir~iut mixi~ ~rtlon~,
R~s~r~ , to Figures 1 and 2, the illustrated con~entional inter~al
nlixer is ~ ct~red by the applicsnt~ ~nd is sold as the ~'Intermix1'
interllal mixer. The il~ led mixer eon~ s ~ Lasin~ drfi~ n
internal w811 1 ~vithin which rotors Z snd 3 are ~upported. The rotor 2 i~
supported on a shaft 4 and in use is rotate~l in the direction of arrow ~
The rotor 3 i~ ~upported on ~haf~ ~ and In use is rotated in the dlr~_Gon of
S~D.~ ;7~
12 NOY '97 08:51
_ 02220935 l997 ~
WO gC13S507 r~ 96/0~128
11
srro~r 6, The r~tor 2 ha~ a cylindrlcal outer surface from whicl
r projection~ 7, 8 and 9 extend toward~ the wall 1. The rotor 3 sqpl G~l~
projections 10, 11 and 12 which also extend towards the wall 1. The
proje ~rll 7 and 10 deime portioIIs of a hclix and t~e ~otor~ are ar.s~
such th3t the p,rojection 7 is r~e.,;.ed in the spsrin~ bLI.~e- proj~ ".s
11 and 12 a~ the ~wo rotor~ are tu~ned and the projection 10 is r~c.~
l,eh. ~L~ the two proje~t~ 8 and 9 ~ the rotors turn. Thus the
proje t.r 1- of the h~o rotors are in~erlocked and such mi~er~ ~re
~enerally t.er..fe~ to q~ h~in~ interlockhg rotors. ~t the nip ~P~Pd
Leh..;~.~ the t~o rotor~ there is a small clearaDce ~pt~ the radiall~
outer snrface of tbe ~ojc.t;~Ys on one rotor ar~d tbe adjslcent cylindr~cal
SL~r~w of the other rotor.
The projection 10 defines a leading edgç 13 ~hich subtend~ ~n
an~le 14 of about 53~ with a r~diu~ dr~wn from the axu of rut~tiul. of the
rotor. That sam¢ pro3ection defines ~ tr~ilin~ edge 15 ~hich defines a~
~ngle 16 rel&t;Yc to a radius. The angles 1~ and 1~ are ~ s~ tl~,lly the
same. Similarb, t~e projection 11 define~ a leading ed~e 17 ~èfi~in~ an
angle 18 of about 47D~ and a tr~iling edge 19 defining sh angle 20 ~vhich i~
~nh5tu~tisllly the same as the angle 18. Thus the shape of the 1 - ~ing edge
of each proJection ic substantially the same ~s the shape of the trailin~
ed~e of each pro3ection. ~he ~hape i~ not alway~ identical ~nd in some
form~ o~ the h.t~...dA internal mi~er manu~actur~d by the applicants
SUBSrITUl~ S~IEET IRULE 26) - . -
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lZ NO~ '97 ~9:06 CA 02220935 1997-11-12 '~ - -~ 4
thç~-e are minor JifL,~ ce3 I~.,h. c~ tlle ~h3pe3 of the l~ n~ and tr~iling
edges a6 c~ be ~pp~e.i3ted from the tisclosure of.l~uropes~n Patent
S~ O 170 397. Thes¢ di~erencu between the shape of the
l;n~ and tl~ailing edge are rdath~ely minor ho. .,.el and ~re generally
co~ce~ed with.:~~ooth~g he nOw of mate~i31 over the project~ons in.
~egions ad~acent the ~s of the rotors. ' -~ ~
The casing ineor~or~t~s an inlet Zl in which a ~ Z2 is ~lidably
recyi~ eL The casing also COlTlpriseS an o~tlet beneath the nip between the
rotors. Thc.outlet is not shown in Figures 1 snd ~ but it will be
ap~ tcd that ff cu~~ 3 a doo1r which i~ llorm~lly fixed in position
~nd ~hich c~n be opened to dlsch~rge a batch of miYed material from the
chs n~l e~ ~ - ,
~ igure 3 i}lu~lr~tLs ~e oper~tio~ of the mi~ture of F~gur~s I and 2
when ~ batch of raw polymer is ingested. The polymer is ~enerally
~upplied in r~ el~ large pieces nnd must be broken down withi~ the
mixer. The ~troduced mate~i~l may be ~ s~e.l dow~ by the ra~n into the
nip of the rotor~ and the m~terial is gradu~ drawn into the m~ g
ch~mber through the narrow gap betwecn the rotors. The ~ap be~veen
the rotors ~nd the degree to which the m~teri~l to be l~ d is gripped
by the roton ~i~nil~ .tl~, affect the r~te ~t whic~ material can be
ingested~
CA 0 2 2 2 0 9 3 5 1 9 9 7 ~
W0 96/35507 ~ r _ '01 128
Re~erring ta Figure ~, thi~ lllùsl~ the disl,o.,i1iu,. of the mate~ial
being m~ed ~hortly beiore the end of the }~ ng of a bat~h of'
materiaL It will be se~n th~t ram has been l.,..~r.d considerably a~
compared with Fig. 3 and material no~Y~passes over the radially Outer
surface~ of the projectj~C The mate~ial is al80 worked bet~ A. the
rotors. The ~heolûgical c~nrlit;orlC ~Ithin the ~h~ber aré clearl~ ~very
dirf~ t at the l.~ of a ~atch l,.uces~i..g as illustrated in Figure 3
and at the end of the same batch as illu~t~LI in Figure 4. At the
be~;nr~ing of the proçess, it would be sdv~Dhg_ûLi. to widen the gap
L~ n the rotor~ so as to speed up ingestion and increase the us~ble
volume of the mlxer. The ~ap cannot be too lar~e however if the
compo~lents of the material to be m~ed ~re to be adeyullt~l~ sl~ ~; ~r 1 ~nd
distributed. At tbe end of the procesY, when the material to be m~bced is
warm and r~ 80~ it iS desirable for the m~terial to be forcèd
I.el..e~ the radia}ly ollter sur&ces of the projectlo~s snd the chamber
wal~ ~o as to en~ure adequ~te P~ ~n~jnnal shear 4tr~,~3~.~ snd strain r~tes to
obtah~ di;.~er.i~ ml~in~ of the componenb. T~e pres~ure u~Js1r~am o~
the proj~ n~ i5 p~rtly a filnctinn of the st~l,.,c,.;. of the I -rl;n~ edge ~f
the proiectjonc- As the material ~oftens, it i~ desirable that the proportion
of the material which i5 circulated between the helical projections rather
than forced o-ver the radi311~ outer surface o~ tho~e projection~ tend~ to
de~r~c, slld hence in later stages of the mixing process it would be
~ 12 NOV '97 08:5~ - ~CA 02220935 l997-ll-l2 .,, . P.l~
,
W O 96135507 r~ll~b96lotl28
desirable to mal~e the IPa~l;ng edges of the projc_ti~ less stBep so ~g to
encoura~e more materl~1 to pa66 o~er the radially outer ellges oF the -'
projections ~ r~ L. z~t;~g Cigr~ ht ç,y~n~ E5 and shear
Stl'~,3~ of thé mater~al. The 'r~ , rheolo~ic~ ~,rur_.1' o~ the
mahrial to l~e 'mi~ed hence ~orce~ the mixer de~l~ier to adopt a ~r~ole
series oi' c~ e~ when it comes to the cnr~ ;3Li~.- oi the rotors.
The l~n~j~ g edgeg of the projections are not ~s ~teep a~ would be ideal for
the ihitial pha~es of a Inixiug process for in~;....tiu~ and d~s~ JuLlon but
are ~teeper t,han ~ould be desirsble for the flnal sta~es of that process for
dis~ei D;G~.
The problems of ~ef~;lerl ro~or designs as~oc~tP~ ~ith ~rt-rlocl~
rotor mi~ers oT the type illustrated in Figure~ 1 to 4 ire encG~ d in
other mixer~, for e~ample the Banbu~y-type mixer sel~m~tica~ly
illustrated in Figure 5 ~n that ~ er a rotor 23 turIIs about axi5 24 within
A chamber 25. Material 2~ to l~e mLl~ed is tr~pped l..~,.e.n thè cha~ber
wall and tbe rotor and as a l~esult the material is smesred a~ainst the
chamber ~all. Give~l that the rheological pr~.~t. 1;.6 of the material to be
mixed ~ary o~er time due to hea~in5~ and pl~ tion the profile of the
rotor i~ once a~ain a compromise, the sln~lc b?tn~L~.. the rotnr surface
a~jaçent the ch~ er ~vall ~n~ the wall itself being :..~rr..,.~tl~ large to
en~ure that a fresh batch o~ material can be in ~Yte~ but 5nff~ tly~sma
to ensure that the softened material i~ a~eq~ately stressed. Once again, in
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~A 02,2,;2,~0.~935 199 "~
WO9~ .7 }~ .......................................................... ,,f~01128
internal mL~:ers of the ~ype s~h~ ffr~lly illu~trated in Figure 5 the rotor
. is turned in one dirL.hon only and there io no slgnific~nt dirr.... ~L~e
L_l. ._~ the ~o~ 6 r~liu-- o~ the rotor ~urface a~ l.h.e>,". the ~ m
~nd downstream s1des of tha~ ~urf~ce.
It ha~ .~een know~ to pro~lde an inter~lal mi~er Or the type
il~u;~lr~ted in Figure~ 1 to 4 with a r~ . 5iLle motor to enable the roton to
be dri:ven in reYer~e to assi~t in r~l~oci~ mmed mixer. No propo~al~
haYe been m~de hc.~..,.~Y ~o drire the rotor~ of an internal mixer in both
Ji~.i~t;o~s during ~ no-mal mu~in~ ~ru~ gcle.
The present Is~v~ntion relie~ upo~ a re~ Hon that a rQtor. can be
~ri~d to p~o~ide a first ~et of cor~lit;nn~ ~ithin a mixin~ c~a~nher
when rotated in one dir~. lic~ ~nd ~ Isecond set of c~ndjtio~ when dri~eD
In the o~Gg;l~: di. ~- tion. By sh~ping the ci~ fL. ~ ially spaced ~ides of
the pro~c_~iul~s in an approprS~te m~nnPr~ ~ rotor c~n be de~igned whlch
p~o~ide~ br~ance equivalent to t~at ~hich would be achieved by
using separate fir~t and second mi~erg sequentia~ly, the first mi~er in the
sequence bein~ rl to optimi~e ~c~fu~ al~ce in ~ first phase of a
b~tch miYlng pr.,c~s and the ~ecorld ~xer being dL.~ d to optimi~e
performan~ ~or the completion of that process. All th8t is ~ u;r~.l to
pUt the ;U~GUt;On into practice is a rededgn of the c;ren..lferentially
paced ~urfaces of the projections snd the ~ru~tls.on of 8 drive rnecl~
SllBSr~TlJTE S~lEFr ~RULE 261.. . .
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~;5ro 96/3ss07 r~,~B~510
16
which i~ capable of driYing the rotors In both di.~,_hu~s over ~ -t
r~ u of a mLxing cycle. n
Figure 6 illustrates a rotor modlfied in acco~dance ~ith the ~ nt
inventio~, and Figure 7 illu~ lLs in c~c4s ~e~ion the ~o rotor~ of the
~ machine in whi'ch each rotor h~ the same co~ ;unq~ s that of Flgu~e
6. The general structure of the rotor of Fi~ure 6 l~ identical to ,that of the ',
rotor to the left hand ~ide of ~Igures 2 to 4 but It ~iU be 6een th~t the
upstream edge~ of the ~rojection~ ~Yhen the rotor turns in the dir~_lic.l of
3rro~ 17 h~ve been made morc steep ~here~s tbe u~lr~..m edg~s of the
~ro~e-t~r~ ~Yhen the rotor i~ rotating in the direction of arrow 28 hay~e
l;leen m~de les~ steep. The sh~pe of the surface~ be~ore mo~ ir-l; n in
accor~ance with the present invention i~ fed in Figure ~ by the
doffed ~Ines 29. ~iven the modifirQffoD of the rotor as shown in F~gure 6
and equivalent modifi~ations to the right hand rotor ~s ~ho~vn in Figure~
2 to 4, to produce the ~r.2~ e-..ent shown in E~igu~e 7, and a~uming
r~ of the dirc~lio~ of rotation of the rotor~ appropriate time~,
Yariou~ berefi~ arise. Firstly, by incre~sing the ~teepn~s~ of the le9~A;n~
edges of the projections ~lvhen turning in the direction of arrow 27 the
m~teri~l within the mixer can be more positively gripped by the rotors to
impro~e i~ i, transport of material within the ch~ber, and
~e of mate~ial from the r~her. In particular, the ~peed of , ,.-
in r~ , ls in.~ as- ' and the gap between the rotors ma~ be in-;t~ to
~ ~ 0222093~ l997-1~
WO scr~L / '
17 -
furthcr ih.l,r.,ve the speed of ~ ,il fi~ ~nd di~cbarge snd to increase the
us3ble vt/~ u a of tbe mi~or. .Sec~n~lly, by de.,..,a~:..F. the steepne~ of the
IrA~ ed~ses of the projections when turning in the Jir ,~ho-. of arrow 28
uan¢ltles of ~ t~;~;al are subjected to high stre~ ~nd strsin.
Figure ~ illu~lr~t~;. one simple modlfic~tion to a proiection whSch
c~n be made~in ac~ lance with the ~r~ t i~ .tlc~. To ~impli~ the
tio~, ~Igure 8 shows the pro~ection~ having ~traightened out the
curvature due to the grlindrical o~br surface of the ~nain rotor body.
The full line In ~igure 8 repre~ents th~ co~L~r .t; of the pro~ect~on of a
~on,~t~.LiG~al m~in~ machine of the type sho~n in Figures 2 to 4, whereas
the doffed line sho~s the c~ nf:g~rytion of a h~o~ifi~ projection in
accordsnce with the ~ l inYention. The arrow 30 represents the
direction of movement of the prnjection during the initial pha~e~ of the
mlxing ~ro in which the ~eIatively steep leading edge enables $he
l~tr~Jd~ced material to be po.,;ti..l~ gripped and forced into the ch~mher
interior. The arrow 31 re~r. ~nts the directIon of movement of thc
projectioh after reversal of the mixer dr~ve such t1tat the relatively gently
slop~ng l~e~ ed~e of the projection encourage~ tb~LI to tra-~el up
~h3t l~ in~ edge and over the upper portion of the projection during
which time it is subjected to high stre~s.
Fig~e 9 illu~tra~es yet another conceivable configuration ~or a
modified projection for I~Se ih ~n embodiment of the pre~ent in~ention.
lZ NOV '97 08:54~ ' CA 02220935 1997-11-12 r.2~
.
W 096/3550~ 96/OI12
Again the dotted line represent~ the ~O~ ;ur~tiOn of the mo~ified
projection, whereas the ~u11 line shows fhe ~t~ rd cGur~ r~tion~ It ~Yill
be seen that the leading edge (in the direcliu~ of arrow 30) i~ undercut so
~g to prû~r~de a vely secure ~'~,ripp;~g" of material durin~ the ing~ n~
phsse. A ~in &e IP~ g cdge t~n the di. ~,I;on of arrow 31) i~ ~ relati~ely
gerltle ~lope ~o as to plovide ~ l nO~ ~vithin the co~lv~ and
dl~erging gap~ and to ~ ul~r~g~ material to flow onto the radially outer
surfacc of thc pruJection. It m~ bc thae the undercut ~ul.r~;.Jr~tion as
~hown in Figure 9 would res~ lt in "dead" or ~t~gr ~nt sp~ce which ~ould
-not be adequately swept out if the rotor alway~ turned in the directlon of
arrow 31. ~his lleed not be a problcm ho.~ r providing during the final
~tage~ of a mL~ing cycle the rotor turn~ in a direction which ~voids any
dead ~paces o...~r.;r~ or eYample, during fhe initi~l in~e~tion pha~e
the projection could move in t~e direction of àrrow 3n, the rotor direetion
could then be reversed until imm~ tely before the completion of the
mixing cycle, ~nd tne di~ch~rge portion of the cycle could be L~f~ct~d after
a Ç~ er reversal of the direction of r~tz.tio~ of the rotors ~uch that
during the dischar~e phaYe the projection move~ ~n the dlrcctiu~ of arrow
3D.
It wil1 be appreciated ~hat in addihor to the control of the
dir~_llO~ of rotatiûn of the rotor~, a mixing cyc}e Cah 9180 be controlled by
adjusting the speed of rotatlon, the ~m pressu~e, coolant tem~_.alurb
wos6nsso7.. . ~ 1128
l9
and miYing ~cle dLr~liGL. The em~o~ Pnt of the pre~ent i~e~,l;on
described in Fi~ 6 to 9, in proposing the revers~l of the directiûn of
rotqtion of the rotor~ in as ~ :- t;on wlt}l a ~o~fi~tir~n to the shapc of the
rotor projectlons, add~ a furtber ~ari~ble which can be used to control tbe
mi~ing cycle, l The rotor~ c~n be dPal~rPd to optimlse inge~tion,
di~tribution 3nd di~charge o~,e~lion~ while the rotors o~c.~L~: in one
dir~ iu~ o.. ~.~. ..r.ls at t~e nip) ~nd to optimi~e dispersion and
pl~-~ir~tin~ while the rotors turn in the ~~k~ ~P ~lir.cti~ (upwards at the
hip).
The r.,l~ steep ed~e~ o~ the projections m3y be given su~face
fe..tur~s to i~,~u. e the gripping of ~aterial during the ingestion ph~se.
As il1..~.l~tt,.1 In Figllre 9 ~~nt~ ;ut~ may be fo~med hut al~ u~ti..a are
~r a~ihl~ or example the ~vviblon of relatively ~harp corners on the
projection edge~. Ih ad~ , the ~.~rr~cc3 of the projectiorls and of the
rotor L~ n the prù~ection~ may be provided with indenhtioD~ ~nd
depr. :- ~ that sre sloped in the helical, axial or circumferential
diree~in~ Experlmc.~l~t; will be nece~sary to define the op~i4~u
c~r ~ r~
In a double rotor mixer with contrs-rotating rotors, during the
i~ 1.û~ phase hi~gh pre~sure develops above the nip between fhe rotor~
and be~ the ram. When the rotor~ are r~ d, high pr~ ur~
develops benesth t~e nip in the re~ion of the chalnbe~ dischsrge door.
.
- 's~lJBSrl,TU~E S~E~ ~RUIE 2B~
..---. ---'lZ NOV '97 08:~5 CA 02220935 1997 il 1~.. . . P.25,~
~
WO 9G/355n7 P~ ;b~-loll28
The ~ char~e door i~ flxed in 1 o- if;~ nd t~us ser~ea ~ a high ~r~_lJr~
ram to ensure that the m~terlal to be mix~d is suhjccted to high stress. - '
The çol~cept of rotor direction reversal with rno~ of the
pr~3ectloh ~utr~ee~ provides an extra control variable wh~ch can be u~ed
for e~r~rnrle to achieYe shorto~- cycle time~ and/or greater mi~in~ capacity
a result of the clo~er match L_h.~l. the h~s~rhinc çonfigurat~on ~od
6~ .JC~ need~.
An alternative embo~imP~t o~ the invention ~s illwtrated in Figure
10. This embodiment compri~es contra-rOtating rotors 32 and 33 but the
rotor~ turn in only one dirci~liOI~ ~s in~l;rqte~l by arrow~ 34, The leadi~g
edges 35 and 36 of t~e projection on rotor 32 h~Yc been m3de r~l..ti~el;~
more ~teep by cl~n~in~ their shape from that intl~rptpd by dotted line~
The tra~lhg edge~ 37 ~nd 3E~ are of conventional shape, corre~por~;ng to
the shapes ~hown in Figures 3 and 4, in contrast, the leadin~ edges 39,-40
of the proiPeti~n~ on rotor 33 havc been made relatively le~s steep by
~h~ngjng their ~hape frorn that in~ir~tP~I by dott~d lines. The trsiling
edges ~1 and 42 are of conventjor~l ~hape.
In the embodiment o~Fig~re 10, the relaei~el~ steep lead~ng ed~s
3~i, 36 of the projectiono on rotor 3a en~ure rapid in~estion of material
into the mixer. The leadin~ edges 3g~ 40 oE the projections on totor 33
then ensure that the material is sobjected to high stregs and sbra~n.
~ ~ . ~ . .
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