Note: Descriptions are shown in the official language in which they were submitted.
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Docket 6276
AIR SEPAR~TOR METHOD AND APPARATUS
Backgr,ound of the Invention
This invention is directed to the axt of separation
of entrained air and frot~ from pi~mented coatings and the like,
in a paper coater or converter. The invention particularly i.s
directed to apparatus and method for applying clay type coatings
or the like to a moviny web of paper, and to appara-tus and
method by means of which entxained air bubbles are separated,
so that a substantially air-free coatin~ stock is applied ko
the web coating apparatus, and the air and air laden coating
fraction is removed for recirculation to ~he coating supply
tank.
Paper coating materials, such as pi~mented coatings,
ar2 commonly applied by coater apparatus in which an excess
supply of the coating is removed by a doctor blade, air knife,
or the like, and recirculated to a coating supply tank. During
the mixing, pumping, applying and/or doctoring steps, the
coating is likely to pick up entrained air in the form of large
discrete bubbles and fxoth which is returned to the coating
tank. Due to the relatively high viscosity of the coating
0 material commonly used for paper coatingl the bubbles and
: entrained air particles have a ~endency to remain within the
coating for a long period of time. They are not readily sepa-
~: ~ rated merely by settling due to the slow movement of ~he bubbles
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~ through the liqilid.
: ~ 25 When coating materials including entrained air are
redelLvered to t~e coating head, whi~h may be a fountain type
coater, the larger bubbles may cause the coating to skip or
otherwise be applied unevenly.
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Docket 6276 1075163
Various attemptshave been made to break up the
larger bubbles into air bubbles which are sufficiently small
as to cause no problem. Thus, screens have been used to break
up the larger bubbles into smaller bubbles. However, it has
5 been found that a screen tends to compress the air on one side,
and the air has a tendency to expand on the other side o~ the
screPn and recombine again into ]Larger bubbles. It has be~n
vbserved that screens break up orlly the very larye bubbles.
Vortex type separators have been used o~ the type
10 shown, ~or example, in U. S. patents Nos. 2,894,930 o~ 1958,
2,920,761 of 1960 and 3,007,542 of 1961. Such vortex sepa-
rating equipment commonly requires the use of va~uum for
reducing the center pressure and thereby assist in the removal
of the air bubbles. While vortex separation has been success-
15 ful in the separation or deaeration of paper pulp suspensions,it has not proven to h~ particularly successful in the separa-
tion of entrained air from highly viscous coatings. Also, the
fact that the vortex separator is commonly operated at low
pressure requires the imposition of a pump between the separator
20 and the coating head. However, any ~ime viscous clay coating
is agitated, as in pumping, there is an increased danger of
picking up or intxoducing additional air.
Other apparatus for removing or eliminating air has
included elastic ultrasonic wave generators, as shown in U~ S.
25 patents NQs. 3,169,507, 3,169,508 and 3,169,509 of 1965.
8~ _I tbe Invooti~n
As noted, the invention is directed to the art of
coating and particularly for removing air laden or air rich
aoating fractions from papeF coating material. In the method
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Docket 6276
of this invention, a supply of coatiny material having
entrain~d air bubbles is applied to a pump,,and from the
p~mp it is applied to a rotating centrifugal separator undex
'a positive head of pressure. The separator is maintained in
a full condition. Preferably, ~he separator consists of a
rotating, generally vertically oriented cylinder which has
a tangential inlet for directing the flow of air laden
coatings along one inside cylindrical wall in the direction
in which the cylinder is rotating. A first outlet is formed
at or near the top o~ the separator and continuously removes
~rom a region near the axis of the separator an air rich
foam or froth o~ the stock material which has been bxought to
the center region o the separator by centripetai forceu A
non-rotatin~ outlet is near the bottom of the rotating tank
and is arranged to pick up air free coating from a region
adjacent the rotating wall and for direct delivery to the
coater. ~he coating is thus delivered in an air-free state
without ~he imposition of any intermediate pumping apparatus.
In other words, coating is continously removed from a radial
outer region of th~ rotating separator by a non-rotating
pickup which defines a second outlet for ~he tank. This
pickup is preferably spaced from ~he lower end of the tank for
extraction of air free coating and is preferably positioned to
intercept the rotating coating liquid which is ~urning sub-
2S stantially at the same velocity as the tank itself. In this 'mannert an addi1;ional head of pressure is applied to the
coating liquid in that the energy of the xotating mass is
translated into a static pressure head at the pickup. This
head is in addit:ion to the pressure head exerted upon the
material within the tank by the pumping means positioned upstream
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of the tank. Only so much of ~e air laderl or air rich coating
is removed from the central region by the ~irst outlet as is
necessary to assure an air ~ree ~oating at the second outlet.
Thus, the rotating tank is operated at all times in a filled or
substantially filled condition.
It is accordingly an important object of this in~ention
to provide a method of applying :liquid coatinys and the like to a
moving web o~ paper including particularly the steps o~ provid~
ing a quantity of liquid coating material which may have a
quantity of entrained air bubbles therein, supplying said
liquid coating material to a rotating centrifuga~ separator
and maintaining the separa~or in a substantially full condition,
continuously removing air laden coating material from a
radially central region of said separator, continuously
removing su~stantially a;r ~ree coating material from a
radially outer region o~ said separator, and conveying said
air free coating material directly to said coater inlet without
the imposition of intermediate pumping apparatus for
application by said coater to a moving web of ~aper.
Another object of the invention is the provision of
a rotating tank separator, as outlined abo~e, which is adapted
to be opera~ed in a filled or substantially ~illed condition
and from which air laden coating is removed for recirculation
to a supply tank and air free coating is removed from an outer
region o~ the tank fGr delivery to a coater.
The above aspect of the invention provides
a separator for separating an air-laden coating
fraction from paper ~oating liquid, comprising a ~enerally
cylindrical tank, means mounting said tank ~or rota~ion
about a generally ~extical axis~ me~ns in ~he upper end
o said tank defining an inlet for a~mitting coa~ing liquid
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into said tank including discharge means arranged to direct
coating liquid from said inlet tangentially of an inside
wall of said tank, means defining a first outlet opening
into a radially central region of said tank at the top
thereof for withdrawal of separated air-rich coating fraction
therefrom, a non-rotating pickup adjacent the lower end of
said tank having an inlet posit:ioned adjacent an inside wall
of said tank for intercepting a:ir-free coating liquid adja-
cent said wall, an outlet pipe connected to said pickup ~or
deli~ery of said air free liquid from said tank, and means
or rotating said tank about said axis in the direction of
flow from said discharge means into said tank.
These and other objects and advantages of the invention
will be apparent from the following description, the
accompanying drawings and the appended claims.
Brief Description of the Drawings
Fig. 1 is an eleva~ional side view, partially broken
away, of a rotating separator construc~ed according to this
invention;
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Docket 6276
Fig. 2 is an elevational front view thereof, also
partially broken away;
Fig. 3 is a transverse section through the separa~or
taken generally along the line 3-3 of Fiy. l;
Fig. 4 is an enlarged vertical fragmentary view of
the detail of the inlet at the top of the separator;
Fig. S is an enlarged fragmentary view showing
details o the outlet at the bottom of the separator; and
Fig. 6 is a flow diagram showing the method of
this invention.
Descript~n ~ Preferred Em~odi~ent
A rotary separator constructed according to this
invention is illustrated in Figs. 1 and 2 as including a
generally verticall~ oriented, cylindrical tank lOo The tank
lO has a cylindrical wall lOa, a top closure wall 11 and a
bottom closure wall 12. The tank lO is mounted for rotation
on a support structure which includes a pair of spaced I-beams
13 and 14, forming a base. A pair of box beams 15 and 16
(Fig. 2) extend upwardly on the beams 13 and 14.
Rotating support for the tank lO includes an upper
joint and bearing assembly 20 shown in enlarged cross sectional
detail in Fig. ~ and a lower joint and bearing assembly 24
shown in enlarged detail in Fig. 5. The assembly 20 includes
- an enlarged collar 30 mounted directly on a cross member 31,
extending between the upright beams 15 and 16. The collar 30
internally supports a bearing 32 and a grease seal 33 by means
of which the upper end of the tank lO is supported for rotation.
; For this purpose~ the upper closure wall ll of the tank lO
supports an upwar~dly extending hollow shaft 36. The lower end
of the shaft 36 extends through an opening formed in the wall ll
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Docket 6276 1~7516~
and is welded thereto, while the upper end of the shaft 36
is supported for rotation within the hearing 32. As shown
in Fig. 1, the shaft 36 intermedi.ate its ends supports a
pulley 37 for belt drive by a motor 38 mounted on the upright
beams 15 and 16.
The hollow shaft 36 provides the means by which the
coating liquid is admitted into the interior of the cylindrical
tank 10, and also provides the means by which a foam laden or
foam rich lightweight coating fraction is removed fxom the
tank lO. Inlet means for admitting coating into the tank lO
for separation of air therefrom includes a depending non-
.rotating inlet pipe 40 which extends downwardly through the
collar 30 and through the hollow shaft 36. The pipe 40
terminates at its lower end in offset relation to the central
axis of the cylinder lO, and defines a tangential outlet orifice
43. The orifice 43 is positioned in such a manner that the
direction of fluid flow into the tank 10 is in the same
direction the adjacent tank wall lOa is rotated by the motor 42.
The upper end of the inlet pipe 40 is supported on
2G the collar 30 by a sleeve 44 and is secured to the sleeve by
an expanding annular pipe clamp 45. The p.ipe clamp 45 may
be of the type sold under th~ trademark "Ringfeder" by Rlng-
feder Gmb~, Krefeld-Uerdingen, Germanyt and sold in the
Unitad States by Adam Kreuter Associates, Pittsford, New York
14534. The outside diameter of the inlet pipe 40 is less than
the inside diameter of the shaft 36 to define an annular tank
outlet 50 therebetween. The annular outlet 50 communicates
wikh an axial passage 51 and radial passage 52 formed in the
sleeve 44. This, in turn, opens into a threaded ou~let pipe
54 in the sleeve 30. The annular passage 50, passages 51 and
52; and the pipe 54, define a ~irst outlet which opens into
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Docket 6276
the tank 10 substantially at a radially central region
thereof in surrounding relation t:o the inlet pipe, and
provides means for the extraction from the tank of a
separated air-rich coating and entrained air bubbles from
the top of the tank at a radially central region thereo~.
An end face rotating seal assembly 60 is mounted
on a flange portion 61 of the sleeve 44 and cooperates with a
fixed ring 61 carried on the shaft 36. The rotating seal
assembly 60 further includes a spring-biased annular washer
63 bearing on the ring 61, a compression spring 64 and a
sealing diaphragm 65. The seal assembly 60 may be a "type
21" seal manufactured by Crane Packing Company, Morton Grove,
Illinois. The assembly 60 forms a fluid tight rotating
coupling betwsen the shaft 36 and the sleeve 44.
~he lower end of the tank 10 is supported for rota-
tion in the assembly 24 similar to ~he manner which has be~n
d,escribed in the connection with the assembly 20 at the upper
end. For this purpose, a collar 80 i5 provided with a bearing
82, the latter being ro~atably mounted on a hollow lower
extension shaft 84. The shaft 84 is received within a ~entral
opening formed in the lower tank wall 35, as sh'own in Fig. 5,
': and is welded to the wall 35. A non-rot'ating coating outlet
pipe 90 extends into the interior of tank 10 at the lower end
s thereo~ and extends downwardly through the collar 80. The
pipe 90 is retalned on the collar 80 by a sleeve 92 and
is secured by an expanding pipe clamp 93 identical to the
clamp 45 above.
The upper end of pipe 90 supports a coating pickup
~:~ : tube 95. As sho~wn in Fig~ 1, the tube 95 extends radially
outwardly and axially upwardly, and terminates in an inlet 96
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Docket 6276
(FLg. 1). The inlet 96 is positioned somewhat above the
bottom 12 o~ the tank 10, and is positioned adjacent the
inside surface of the tank wall lOa. The inlet 96 opens
toward the direction of rotation of liquid coating within
S the tank 10 as shown by the arrow 97 in Fig. 3. In this
: manner the energy of the rotating coating liquid is trans-
ferred into pressure as it impact:s against the inlet 96
and flows therein and downwardly through the pickup tube
95 and the connected pipe 90 for extraction from the tank
10. The spacing of the inlet 96 somewhat axially above
tha bottom wall 12 assures that the opening therein is in
a region of rotating li~uid and above any possible stag-
nated layer due to impedance to rotation of the iiquid
caused by the non-rotating tube 95.
The outside diameter of the outlet pipe 90 i5
less ~han the inside diameter of the shaft 84 to provide
an annular drain outlet 100 (Fig. 5). The drain outlet
100 may be connected to a radially extending drain pipe
102 through an annular passage 103 and a radial passage
104 in the sleeve 92 by means of which a tank 10 may be
completely drained for puxging or cleaning. A rotating
end face seal assembly 110, similar to the assembly 60,
is received on the sleeve 92 and forms a rotating seal
with the shaft 84.
In Fig. 6, a coati~g system is shown according
: to the method of this lnvention by means of which air free
coating may be applied to a moving web of materialO
the practice of the method of this invention,
Fig. 6 illustrates the use of three identical separator
:~ 30 tanks 10 connected in parallel for the delivery of air
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Docket 6~76 10751~
free coatiny to a coater, which is diagrammatically illus-
trated at 120, from one or more of the tanks. The coater
120 is illustrated in Fiy. 6 as being of the fountain type
(as described in U. S. patents Nos. 3,418,970 and 3,521,602)
to apply the li~uid coating to a web 121. The excess coating
is removed by a doctor blade 125 and returned to a catch pan
or basin 128. The apparatus and method o the present inven~
tion may be used with any type of coater, including trough
type applicators, fountains, or roll type applicators with
doctor blade, air knife or metering bar apparatus. Typically,
a substantial excess coating is applied by the apparatus,
and up to ninety per cent or more o~ the applied coating may
be removed by a doctor blade. It is common to apply an excess
of coating material so that there is a sufficient excess of
coating doctored off to wash the doctor blade and prevent the
o~currence of dry areas, or the build up of drie~ coating,
on the doctor blade. Thus the coating which is caught and
returned is subjected to subskantial mechanical agitation and
is often subjected to a certain amount of atomiæation or
breaking up of the coating particles, so that a substantial
quantity of air may be mixed in with the coating ma~erial.
~ he coating itself may vary widely in character-
istics~ Typically, the coating includes clay pigments and
a starch base and may hava a low viscosi~y o 400 CPS or
less (as measured by Hercules and Brookfield) at 110 F
up to 3,500 CPS or more (Hercules and Brookfield). Such
coatings may contain as little as-twenty per cent solids,
or less, up to seventy per cent solids or more.
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Docket 6276 ~
Typically,,a variable flow rate pump 130 returns
the air laden coating to a main supply tank 140. In the
process of the invention, a varialble flow rate supply pump
14~ delivers coating through a fi,lter 143 and a cor~mon
supply line 144 to the inlet 40 of one or more of the tanks
lOa, lOb and lOc as illustrated l,n Fig. 6. The tank or
tanks being used will be subject to continuous rotation by
their motors 38 for separation of the lighter and air laden
fraction and for delivery of a subskantially air ~ree
coating fraction through the outlet pipe 90. The coating
outlet pipe 90 of each respective tank is applied through
valves 145 to a common coa~ing supply line 150, which
applies the air free coating directly to th~ coating head
120. Individual valves 160 are preferably inserted within
the outlet pipes 54 to a common return line 162. The valves
160 control the static pressure of the coating liquid within
the tanks 10 by controlling the rate at which the lighter,
air laden coating is xemoved from the respective tanks.
The us~ of two or more separators as shown at lOa t lOb and
lOc of Fig. 6 permlts a selection in the capacity of air-free
coating required and also permits one of the units to be
shut down for cleaning while the others,are in operation.
I~ the operation of the invention, coating whlch
contains entrai~ed air is applied to the interior of the
cylindrical tank 10 through the inlet pipe 40 and outwardly
thxough~the tangential outlet 46. The tank is at all times
illed or substantially filled with coating. The tank is
rotated in the direction of fluid flow from the outlet by
; the motor 38, and the entire mass of li~uid rotates with
the tank~ The material is thus delivered to the interior
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Docket 6276
of the tank under a positive head of pre.ssure from the
variable supply pump 142. The air bubbles being substantially
lighter than the coating, tend to conc0ntrate at the top vf
the tank near the closure wall 35 and also at the radially
cantral region of the tank, and are removed together with a
quantity of the coating through the annular outlet 50 and
the outlet passages 51 and 52 to the pipe S4. This foam
laden material is thus returned to the supply ~ank 140 pre-
ferably through the valve 160 as described above.
The relatively air free coating is picked up hy
the inlet 96 and pickup tube 9S positioned adjacent the
inside wall of the tank 10 in spaced relation to the bottom
wall 12, and is delivered directly to the coating head 120
under the cumulative head of the pump 142 and an additional
head induced by the rotation of the coating liquid within
the separator. The drain passages 190, 102 and 104 may be
employed when it is desired to completely drain out and clean
the tank 10.
In the operation of ~he invention, and as an
example, a tank 10 was constructed which was 42" long and
9" inside diameter with a capacity of approximately fifteen
;~ gallons. The motor rotated the tank about its ver~ical axis
at from 500 to 600 revolutions per minute. Coating material
of 1,700 CPS (110 F Hercules and Brookfield) having 56 per
cent solids was applied to the tank at a rate of approximately
~ twelve gallons per minute and coating free of air was extracted
; at a rate of approximately eleven gallons per minute while
approxim~tely snle gallon per minute of fo~m laden overflow
was permitted to flow out of the tank through the outlet
passages 50, Sl and 52 into the pipe 54 back into the supply.
The tank was rotated at about 600 xpm. The output of the
pipe 102 was free of any visible entrain0d air, and was
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Docket 6276 ~ 7~
directly applied to a fountain coater which t in turn, applied
the coating to a moving web of material at about .B yal./inch/
min. at 2,000 fpm, fxee of any skips and separations in the con-
tinuity of the coating. In another test, ~20 CPS, 42% solid
coatiny was applied to the tank in excess of twenty gallons per
minute and air free coating was applied at about 19.5 gallons
per minute to the coater which applied to the coating to ~ 2,000
fpm web at the rate of .7 gal./inch/min~ free of skips.
The rate of rotation of the tank 10 may be varied within
wide limits as necessaxy to effect a separation of the entrained
air and foam towarcl the center of the tank by centripetal force,
but not at such a rate as to cause a separation of the constitute
components of the coating itself.
It will thus be ~een that the invention provides method
and apparatus for the skip-free coating of paper webs and the like
by the separation in a rotating tank of th~ air-rich fraction of
the coating without attempting to break the air bubbles down into
smaller bubbles. Since the tank is maintained in a full or sub-
~tantially full condition, it is operated under a positive head
of pressure, and this pressure is augmented by the pumping effect
o the rotating liquid coating impinging upon the static pickup
tube 65 sufficient to permit application of the coating directly
fxom the tank to a coating head. The rate at which foam is ex-
tracted through the pipe 54 may be used advantageously to control
the pressure head within the tank, while the return coating foam
mixtuxe is delivered to the holding tank for reuse.
While the method herein described, and the form of
apparatus for carrying this method into effect, constitute pre-
ferred embodiments of this invention, it is to be understood
that the _nvention is not limited t~ this pxecise method and
form of apparatus, and that changes may be made in either
without departing fxom the scope of the invention.
What is claimed is:
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