Note: Descriptions are shown in the official language in which they were submitted.
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APP~ FOR D J~ ;I~ G~; I~ A LIS~JXD
.
Fi~ld of_the Invention
This i~vention relat~s to apparatus whi~h e~hanc~
the diffuæion of a g~ i~to a liquid ~nd more
particularly ~o app~ratus, ~uch as oxygenators and
aerator~, for diffusing oxygen into a liguid.
Bac~qround of the Inve tion
There are presently many use~ for appara~u~ which
enhances tha ~if~u6ioxl of gas into a ligu~d - ~or
~xa~ple, blood oxyge~ators, cell culture oxyge~a~ors and
aerator6. ~nce ~iffu6io~ is ~ molecular pheno~
which oocur~ at the gas/l~quid inte~ac~, the ~ppara~u~
generally operate~ by i~crea~ing the i~terface area over
which diffu~on take6 place or by ag~ta~ing ~he
ga~liquid inter~a~e.
For exa~ple, an oxyge~ation method commonly u~ed in
~ell cultur~ng ~y~tems to introduce oxygen into liquid
cell growth ~edium i~ to place the liguid m~dium in a
long cylindrical container s~c:h as a ~ottle. The
container is o~ly partially fille~ with the liquid BO
that a gas/liguid inter~ace i~ formed. Air is introdu~Qd
int~ the container ~o that oxygen dif~u6es into the
growth medium at the i~terfa~e. In order to enhance
diffusion, the container is ~lowly rotated around its
long axis by a mechanical device in order to agitate the
gas~ uid inter~ace. One obvious problem with such an
WO 92/l8222 1 0 8 6 6 ;~ Pcr/US92/03199 ~
arrangement is that it is not a continuou process and
the m~dium must be ~ontinually removed and repla~sd in
the con~ainer~. In addition, it is di~fic1llt to mo~itor
the overall proc~ to determine when ~he proper l~el
of gas di~fu~ion h~s occurred. Further, ~he ~utrie~t
supply must be periodically repleni6hed through the
labor-intensi~re proce~;s of diE;moun~ing, opening and
reclosing ~he bo~tle, thereby furth~r ~xposir~g the
eo~tQnt to ~ontami~ation.
In order to ~ercome the problems of ~on-~oIatinuouE;
operation and monitoring, other conven~ional apparatu6
is designed to increase the gas/liguid ~n~erface area.
One k2~0wn technigue involv0~ passing large ~umbers o~
very ~all gas bubbles through ~he l~quid. 8i~ce ~he
bubble~ are small, their surfGce area to volu~e r~io is
uite large as~d the large ~u~ober of bubble~ ~n~;ur~s that
~he cu~ulati~e ~urfai:e area of ~Q ga~ guid islg~rface
i~ ~uite high a~d diffu~ion is ~er~by ~a~ced. qhis
latter method is typically used in blood oxygerla~o~.
~uch a technique allows cor~tinuous opera~io~ in which
the liquid can glow t;hrough ~he ~yst~m in a coatinuous
~tre~n. Howe~er, care ~ust be taken to remove gas
bu~ble~ entrained in the blood prior to it~
reintroduction back into the p~ient in order to avQid
problesns with emboli6m.
The second method of enhancing gas diffusion in a
continuous sy6tem i6 to increa~e the ~urf ace area to
volume ratio of the li~uid by 6preading ~he liquid in a
thin film in an atmcsphere ~ontaining the gas. ~ common
method of achieving a ~hin liguid ~ilm is to use stacked
, ~ Wo ~2/182~8 ? ~ ~ ~ fi ~ ~; PCr/US92/03]99
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trays. Each of the ~rays holds a ~hin lay~r of liguid
and as the liguid flow~ through the tray, i.~ spills oler
to the next lower tray in the stack. The process
continues until the liquid rea~h~s the bot~:om of. ~he
tray 2;tACl~. The eff~c~ive ~;ur~ace are~ o~ the tray
stac~c can therefore be a large multiple of the ~;urface
~rea of each tray.
~ ;till other gas dif~usios~ arra~ge~t~ utilize
rotating parts such ~E; d~E; or oo~e~ ~ou~te~
atmo~phere oo~tai~ing the ga~. Llguid intro~luced o~o
such a moving par~ forms a t:hin film due to the rotation.
Thi6 l~tter app~ratus ca.~ operate 6~ontinuou~ly, but
require6 mechanical saal~; to gea1 ~he mo~ring parts and
i~ ~hu~ p~one to geal ~ilure~;, con~mination, azld high
~ai~tsTl~ace co~t~.
Accordingly, it is ~ object of the pres~t
inve~ion to provide a ga~ d~ffug~o~ apparaSu~ ~hich ean
operate co~tinuously.
~ t is another object of the pr~ent inven~io~ to
provide ~ ga6 diffu~ion apparatus which contai~ no
moving mechanical part~.
It i~ still nnother obj~ct of the present t~ve~tion
to provide a gas d~ffusion apparatus which c~n be easily
molded ~rom a polymeric pla6tic material.
It is yet snother ob;ect of the pre6~nt invention
to provide a gas di~fu~ion apparatu~ whi~h is suitable
for use in cell culture apparatus.
It is a ~urther object of the pr~sent inven~ion to
provide a gas di~fusion apparatus in which the chance of
entraining gas bubbles into a li~ui~ is reduced.
w092~822~ ` . PCT/VS92/031ss
~10~6~ 4
.
~ yet a further object of the pre~e~t inv0ntion
to proYide a gas diffu~ion apparatu~ which ifi ea~y to
maintai~ and service.
= ary of the InvQn~ion
The foregoing obj~ct~ are achieve~ ~nd ~he ~or~going
pxoblQms ar~ ~olved in one illu~trative e~bodiment Df
the invention in which a liguid is constrained to ~orm Is
th~n l~yer o~ d flow down, the ver~ical wall~ o~ a
cont~iner ~illed with ~e ga~. The thin li~uid layer i~
subjec~ to e~hanced gas diffu~ion.
More p~r~icularly, the li~uid is applied to a
~pread0r plate which extQnds towards, and forms ~ narrow
gap wi~h, the ~ontainar w~lls. Th~ l~qu~d spre~ds out
in a thin fil~ across the ~preader pl~te, fills ~he
plate/w~ll gap a~d flows down along the co~t~i~er wall~
~nd QXit8 the co~ai~er at the co~ai~er bottom. The
film on the ~ontainer w~116 is sufficiently thin that
gaseou6 d~ffu~ion is greatly anha~c~d.
The device iE suitable for use in the continuous
application ~ince the liquid can ~e continuou61y
introduced at one e~d o~ the container a~d wi~hdrawn at
~he other. 8uffi~ient space ~ a~ail~ble i~ the
container to mount probe6 to monitor ga6 eoncentration
and o~her parameters.
' ~,7 WO 92/18228 ~ fi 5 ~ PCT/~S92/03199
... . . .
:
~rief Des~rip~ion of the Drawinq6
Figure 1 i6 a bloc~ sc~ematic diagram of ~n
illu~trative continuous cell culture ~y~tem in which the
gas di~fu~io~ apparatus of the pr~sent inYention.can be
u~ed.
Figure 2 i6 an axploded per~pe~tive ~iew of one
embod~ment of the inventiv~ gas diffu6ion apparatu6.
Figure 3 i~ a partial cros~-6e~tional diagram of
~he ~mbodiment ~hown in e~plodod form in F~gure 2.
Figure 4 i~ a partial cros~-~ec~ional diagram of
the embodiment shown in Figuras 2 and 3 illu6trating the
liguid flow path.
Figure S i~ a partial ~ross-sectional diagram of an
alternat~ve Q~bodiment of the invent~on.
F~gure ~ i~ a c~o~ eotional diagram of ~ fir~t
alter~ative ~mbodi~ent of the ~preader plate~wall area
of ~he inventive ga~ diffusion apparatus.
Figure 7 i6 a cro~ ectional diagram of a ~ec~d
alternative embodiment of the spreader plate/wall ar~a
of the inventiv2 ga~ diffusion apparatu~.
Figure 8 i~ a cro~s-sectional diagram of a ~hird
alterna~ive embodiment of the s2reader plat~/wall area
of the inventive gas diffu~ion apparatu6.
Figure 9 is a cros~-~ec~ional diagra~ of a fourth
al~ernative embodi~ent of the spreader plate/wall area
of the inventive gas diffusion apparatu~.
Figure 10 i6 a cro6s-~ectional diagram of a fifth
alternative embodiment of the spreader plate/wall area
of the inventive gas dif~u~ion apparatus.
:-
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Figure 11 i6 a cro~;g-;ectiorlal diagr~n of a ~i~th
al~ernative ~mbodiment of ~he spreader plate~wall area
of the inventi~e gas diffu~ion apparatu~.
Detailed DQ~CriPtiOn of ~he Preferr~ EDbodiment~
Although the present iI~v~ntion ca~ b~ us~d ln ma:rly
applicatio~ in which it i~; de ir~d to di:~u~e ga5 into
a liquid, orl6 such ap~lication for which the ~:a~ention
is particularly su~ted i~ ~ conti~uou~ c~ll culture
~ystem in which ox~en must be diffu~ed :;~to ~
contirluou~ly-~lowing l~quid cell culture ~nedium i~ oxder
to induca enhanced cel 1 gro~,rth . For ex~mple, th2
inventive gas diffusion ~pparatus can be provided a6
part of a co~t~nuous cell ~ulture sy~t~m ~0 as shown in
~igure 1.
8ys~n ~0 i~ a clos~d-lo~p sy~em whi~h inaorpor~te~
a cell oul~ure ~s~sel 120, ~ gas dif~usio~ app~ra~us and
r~ervoir 110 which may illu~ratavely be t~e i~Yentive
appa~atus and a plurali~y o~ fluid co~duits which co~vey
a conve~tional cell cul~ure medium b~t~een the variou6
~lemen~ o~ the ~ystem. 6uch ~edium may, for exam~le,
be a rea~ly-available, ~tandard ~iological medium for
cell ~ultura. Cel} culturing actuslly ta~s plac~ in
culture ve6sel 120 which i~ supplied with replac~mQ~t
liquid medium ~rom apparatu6 110 ~ia conduit 88. As the
medium i~ pas6ing through apparatu~ 110, oxygen i6 added
by mean6 of gas difu~ion.
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More particula~ly, outlet port 8~ of alppara~u~i llO
i~ connected ~o the inlet port 86 o~ the culture ve~el
120 ~ia f luid supply co~duit 88 . Outlet por~ 90 of cell
cultur~ vas~el 120 i~, in turn, in fluid co1~iG~tion
with an inlet port 92 cf 2~ppal:a~u~; llO via fluid return
conduit 9~. A pump ~16 i6 po~itior~ed alo~g fluid supply
conduit 88 to co~tinuously p~mp ~luid mediuM from
apparatus llO through culturE~ ~re~s~l 120 a~d ba k to
appar~tu6 llO .
I~ ~rder to add ~luid ~e~ium to ~he appara~us, a
~utrie~t ~upply line 98 i6 con~ectad to ~he fluid sup~?ly
co~duit 88 be~woen pump 96 a~d t~ulture Ye~sel 120 so
that addi~ional medium and nutrie~ts may be a~ded~ to
~lu~d supply cc~nduit 8~. A separat0 pump lO0 is provided
for pu~p~ng ~he nut:rie~ts into the s~luid ~upply co~uit
88 via ~upply line 98.
Apparatu~ 110 i8 al~o provide~ with ~ ~roduct
withdr~wal co~duit 102 conn~ted to a wi~hdr~wnl ~u~p 104
~or r~ovi~g ~luid medium and ~ul~ured cells down~tre~m
from the culture ve~el, preferably ~o~inuously.
~ a~ di~fusion app~ratu~ lla is provided for
continuou6 ~e~upply af oxygen ~nd for carbon ~iox~de
rff~oval or add~tion to ~he culture ~alum. ~ptionally,
gas ~if~usion apparatu~ 110 may i~clude probe~, suQh a~
gas and t~mperature probes (~ot show~), which are
conn2Gted, ~ia el~ctrical leads 1}4, to a controller 112
which can co~rol the conc~ntration o oxygen, ~arbon
disxide and other ga6es introduced into ~he diffu~ion
apparatus as will hereinafter be described to
automatically maintain the oxygen or carbon dioxide
levels in the medium at a predetermined value.
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.
An additional probe 106 may be provided on return
conduit 94 in order to sense variou6 condit:ion~ of the
medium and cell mixt:ure. This probe, in turr~, may be
connect2d to a control devia~ 108 (or alternativ~ly,
control device 112) which d~vic~ control~ t:he ~rar~ous
pumps for pH balan~ing the ga~ conce~trations in the
medium/c~ll mixture. ~exlerally, the 6ystern i~ designed
80 that ~re~h ~e~ium iEi conE;tantly ~eing introduc:ed into
the circulating 6y~ and t~e c:ul~ured cell pro~uct is
co~ti~uously bei~g wi~hdrawn ~rom ~che system at ~ rate
of circulation d~termined by the control device 1û8. An
illustrative ~y6tem such as t:h~t illu~trated i~ Figure 1
i6 shown in detail in TJ,S. Patent Application 8erial ~o.
07~361,141 entitled "Continuous High Density Cell
C:ultur~ 8~r~tem~ ~ile~ by ~3ric 9erry on June 1, 1g89, a~d
licensed to ~he as~ig~se of the present invention.
8in~ the d4tails of thi~ sy~t~m are not importan~ for
an u~derstanding of the operation of the ga~ di~fu ion
apparatu~ o~ the pre~ent invention, th~y will ~ot b~
di~cussed further h~rein.
Figur~s 2 and 3 illustrate one embodiment o~ ~he
ga6 diffusion apparatu~ 110 ~on6truct~d in accordance
with the inve~tive principl~s dis~losed hera~n. ~s shown
in Figure 2, the ~pparatus consists of a body 10 which
is illustrated as hav~ng a cylindrical cross-sectio~,
however, other cro~s-fiectional shape~ may be used in
accordance with th~ prin~iples of the invention without
altering the operation of the device. Body lo ~s
fabricated from a material which is iner~ with respec~
to the liquid and gas flowing through it. A suitabl~
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material is ~las~, ~u~ other ma~erials may al60 3~e u~ed.
As will be disoussed in more detail ~elow, ~he i~ner
wall 11 of body lo is 6peciaily treated so that it i6
"w~ttable" by the liquid flowing through th~ t. In
~he ca~e where body 10 i~; fa~ricated of glas~, i~er
wall 11 may illustra~ively be plasma treated, ~cid
~leaned or ch~ically etch~d.
Body 10 i provided with a cover 12 which is
clamped to body 10 ~y m~an6 of a ~la~i~g ring 14. Ri~g
14 i6 con~tructE~d with a plurality o~ ~hraad~d ~tud~ 16
mouslted thereon ~hic~ project through holes in ~ ver 12
into nuts 18 which c:an be threaded o~o the stud6 to
attach cover 12 to ring ~4 . A 1 ip 13 of body 10 i~
ptured be~ween cover 12 and ~:ing 1~ to ho~d the
a~se~bly together. Arl ~nul~r elastomerio cush~on 20 is
provided between clamp~ng rirlg 1~ and body lip 13 to
prevent da~age to bo~y lo ~ould the nut~ 18 b
overtighte~d. In addi~ion, lip 13 iE; 6ealed to coVQr
12 by ~ s o~ ri~g 22 (show~ Fig. 33.
Attach~d to ~he underside of cover 12 i~ a ~preade:c
plate 24, the pu~pose of which i~ to eve~ly dis~ribute
liquid flowing i2lto the appa~a~us via inl~t 26, a~ will
hereina~er ~e d~sc:ribed. Li3Euid moving ~hrough the
~pp~ratus leave6 by mean~ of exit 30.
Ring 14 i8 suppor~ed on a circular base 34 by means
of three upright supports 36. The ends of support~ 36
have threaded holes 38 into which bolts 40 snd 42 can be
~crewed to fasten ~upports 36 to ring 1~ and base 34.
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~.~08~6~
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The diffusion appara~u~ may al80 ~e ~ ed with
~ariou~ probes which project ~hrough the cover 12 in
order to monitor variou~ co~dition~ of the ga6 and
liquid i~ide ~ody lo. ~or example, a p~ probe.44 and
an oxygen probe 4~ are illu~tr~t~d, how~ver o~her probe~
and metering devi~es may also be i~er~ed ~hrough cGver
12. 8uch probe~ may bæ sealed ~o c~ver 1~ by ~eans o~
cl~mp nut~ S5 or O-ri~gs ~4 (~æ ~how~ in ~igure 3) or ~y
other means ~o tha~ they project into ~he body 1~.
Th~ operation of the diffu~ion ~ppara~u~ hown
sch~m~tically in Figure 4. In thi~ ~gure, pro~e~ ~4
and ~ a~d the gtrU~ure surrcu~ding body 10 have b~Qn
eliminatad to clari~y the drawing. During op~ration,
ligu~d iB introduced i~to the deviae through i~let ~6
and flow~ i~to ~pace 70 be~wee~ the cov~r 12 ~nd ~pre~dar
plat~ 2~. Due ~ocw~ ao~ surface t~nslon.~ffects,
the liquid spread~ o~t ~venly acros6 tha e~ a plate 2
until it reac:he~ the g~p 50 be~cween th~ ~uter-periphery
of plate 24 and ~ha ian2r wall 11 of body 10.
Gap 50 i8 0~ 6u~h a size that ~urface tea~ion of
the liquid eauses it ~o bridge the gap an~ ~orm a thin
film along the i~er wall.ll of body 10. T~e wi~th of
gap 50 iE dspendent on the ~i~co~ity and compo~tion of
the liquid with which the apparatu~ operat~ and may
illu~tratively be in ~he range of .020-.0~0 inahe~. For
example, gap 50 may be approximately 0.020 inches when
~he diffu~ion appara~u~ i~ u~ed with standard biological
cell ~ulture médium of the type that may be u~ed in ~he
cel} ~ulturing syst~m shown in Figure 1.
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,.,
As previously mentioned, the inrler wall 11 o body
10 mu~t be ~r~ated to make it ~wet~ble" wi.th s:esp~c~ to
the liguid ~o ~hat the liguid will ~low down the wall in
a thi~, even l~yer. q~his tre~ t may be dorle i~ ~
convention~ ashio~, for example, ~y pl~sma tre~ g,
chemically etchi~g or a::id ~tchi~g the i~sr surfac~ 11
of a glas~ body 10.
Wharl the liquid ~arges ~rom g~? 50 it ~orm~ ~ thin,
~ven ~ilm 72 over the ~ire ~ody wall 11. Thus, ~he
surface area of the liquid is ~fecti~rely ~e ~res of
the isuler wall 11. Thi~ area ~ ~p~ded by si~?ly
mak~g thQ ~evice diameter l~rger. A large surface
nreA/volurne r~tio i~ establiE~hed due to the t~ film 72
an~ the large l~urace area/volume ratio enha~ces
diffus~o~ i~ a ~awn ma~er. The l~lL~id in ~he f~lm 72
run~ dow~ the wall 11 into a collecti2lg pool 74 whie~h
forms i~ th~-botto~ part of body 10. ~he liguid i~ ~he
~ollect~g 3?ool t~ler~ s by meu~ of ~ lo~r eoci~ 30.
as to be diffused ~into ~ quid i6 i~trodu~ed
in~o body 10 by ~san~ o~ ga6 inle~c 60 where i~ rapidly
di~use~ i~tc~ ~ilm 72. Ul~dif~u~ed ga~ exits body 10 ~y
~ean6 of gas outle~ 62 80 tha~ g~s ~o~ti~ually eslt~rs
~nd exit6 t}le apparstu6 m~int~i~ing a ~on~tan~ g~s
conce~trntios~ body which c~m be ~onitored by mQans of
~he aorementioned pro~es shown in Figure 3. ~ince
liguid constantly ent~rs the apparatus at inlet 26 and
exits, via ~xit 30, the entire de~rice ~an op~rate in a
continuous fashion without arly movi~g parts or rotating
seals that require maintenance.
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-12-
Fig. 5 shows an alternative embodiment of the
pr2sent inven~ion in which the ~preader pla~e 24 i6
fabricated in th~ ~hape of a di~k rather ~.han the annular
~hape ~hown in ~igur~ 2 and 3. In thi~ odimen~, p~
probe ~4 and oxyg~n probe 46 ~xtend through both ~o~er
12 and ~pr~ader p~at~ 24. Prcbes ~4 an~ ~6 are pro~id~d
with adapter ~ub~ 100 and 112, r~pectiv~ly. ~dapter
~ube 100 seals to the top of cover 12 by ~e~s of
thr-~aded ring 102 a~d 0-rir~g 104. A spac~r 106 and
0-ring 108 8e~1 adaptQr tu~e 100 again~t ~h2 bottom o
cover 12. ~preader pl~te 24 i8 held against ~pacer 106
by threaded ring 110. ~imi~arly, adapter tub~ 112 ~eal~
to the top of co~er 12 by means o~ thr~aded ring 11~ and
0-ring 116. A spacer 118 and 0-ring 120 Eeal 3dspter
tube 112 again~t the bottom of co~er 12. 6preader plate
24 is h*ld ~gai~st spa~er 118 by threaded ri~g 122. In
any ca~e, the probes 4~ and 46 must be sealed ~gainst
~preader plate 44 80 that ~o liquid runs down the prob~s.
In the embodiment ~how~ in Figure 5, ligu~d inl~t
26 is loc~ted in th~ ce~ter of ~h~ appara~us; ~his
location ha~ the adva~tage that liquid introdu~Qd i~to
inlet 26 will ~pread more uni~ormly over plate ~4. To
accGmmodate ~he new location of liguid inl~t 26, gas
inlet 60 may be mo~ed to the 6ida and mu~t al60 pass
through plate 24. ~as outl~t 62 (not 6hown in Figure 5)
may al~o b~ placed in an o~f-~enter location.
Figure~ 6-11 show al~ernative embodiments of ~he
spreader plate edge~wall area 52 shown in Figure 3. For
example, in ~igure 6, ~he edge of ~he spreader plate 24
is provided with a ~mall dam 80 which aid~ in maintaining
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-13- .
a thin "pool" of liquid on the top of spreader plate 24
60 that the liquid will ~pread more evenly over pla~e
24. During operation, liquid will spill o~er ~he top of
dam ~0 into gap 50 and the appara~us would perform
sub~tantially a~ previou~ly described.
Figure 7 ~how~ an additional embodiment i~ which
dam 80 has bsen exte~ded i~ heigh~ ~o orm a ~arrow gap
82 bQtween the upper e~d of dam 80 and cover 12. In
this csse gap 5D i6 le~ ~ri~ieal ~inc~ gap ~2 (which
may be smaller than gap 50) control~ ~he release of
liquid from 6preader plate 24.
An additional ~mbodiment is ~hown in Figure 8 in
which a knie edge 84 i6 pro~ided a~ the outer periphery
of pl~te 24 ~o prosride ~he cleararl~e in gap 50 between
plate 2~ and the wall 11 o~ bo~ 10.
Anoth~r embod~ment ~ show~ in Fi~ure 9 in which a
drip lip 86 i8 provt~ed along the outer periphery of the
lower edg~ of ~pread~r pla~e 24. Lip a6 preY~rlt~ uid
pa6sing through gap 50 from running alor~g the bo~tom
surface of plate 24 and dripping from plate 2~ directly
i~to the pool of liguid a~ the bottom of the appar~tu6.
A further embodims~t is shown in Figure 10, in
which the radius of the curved upper lip of ~ody 10 is
increased and the di~meter of plate 2~ is i~creased from
tha point where body 10 is 6ealed b~ O-ring 22 located
in circular s~otch lS ~o that the outer edge of spreader
plate 24 fi~ into the 6pace between the ~ur~red wall
portion and the cover 12 as shown. In this embodiment,
liguid spills off the edge of plate 24 against ~he
WO 92/18228 Pcr/us~2/03199
~i
2108~6~ -14-
curved portion 86 of body 10 and ~hen run~ along ~he
curved portion and down the in~ide wall o~ body 10 a6
schematically illustrated by arrow 100.
Anoth~r ambodiment is ~hown in Figure 11, which
2mbodimQnt utili~e~ a ~l~ghtly di~erQnt ~ody wall
configuration. In particular, ~otch 15 in cov~r 12
( ~hc>w~ in Figure lC ) has been eliminated a~d a
corresponding cir::ular notch 19 has ~en molded i~to the
top edg~ of body 10 to r~ceiYe tha ~eali~g 0-ring 22.
I~ ad~ition, the upp~r in~ida wall of body 10 ha~ a
~apered rection 102 which provides a 61a~ted sur*ace.
8prsader plate 24 has a tongue 108 which extend6 int~
the ~ap 106 b~tween the body 10 and cover pla~e 12 ~ormed
by 0-ri~g 22. Bpreader plate 2~ ha~ circul~r rlot~hes
102 and 104 cut into its unders~de. ~lotch 102 re~lirect~ ~
liquid flowi~g along the ~ders~de o~ tongue lQ8 to
provide b~th vertical &nd horizo~tal flow ~:ontrol.
~otch 104 ~cts as a drip gap to pr~ven~ 1i5ruid ~rom
running ~long the under~ide of ~preader plate 24 ~d
dropping off directly into the liquid po41 in the dQvice.
Although only a ~ew e~odime~t~ of ~he inve~tive
apparatus have been desc:ribed, many modifiGatio~s a~d
changes will be immediately apparent ~o those skilled in
the art. These mc)difica~io~s ~nd ol:her obvious ch~ges
are intendQd tc) be covered by the following claims,
W~at is claimed is.
