Note: Descriptions are shown in the official language in which they were submitted.
'rl~e inven~i.on relates to improvement:s in paper makinK
macllines, and n~ore pa]. ticularly to improvemellts in dewaterillg a web
by thermal nleans wllich permits tlle ~achine to be run at high speeds.
In the continual striving for increased speed of operation
in paper malcing machines, speeds above 3000 eet per nninute in
exlsting,mncllines hclve enco-lntered d:ifficulty in the occurrence o~
~lu~ter alld breaks in the clryer section One of the reasons is
that the ~eb is insufficiently drled and cloes not have sufficient
strength to carry across the open draws necessary in a standard
dryer where the web is threaded,in a serpentine path back and forth
between dryer drums. It has been discovered,that'if the web is-
dried to on t:lle order of 50% bone dry, it will have the strength
and stability to witllstand an open draw between the dryer rolls.
It is'impractical to attain this dryness in a press section.
. It ls accordingly an object o~ the present invention.to
: provide,a high speed paper malcing machine for the production of
fibrous paper web. particularly such as newsprint, which can oper-
ate at higll speeds on the order of above 3000 feet per minute with-
out enco~mtering breaks or other damage to the web at the beginning
of the dryer section.
In accomplishing the foregoing objective in accoLdance
with the principles of the present invention, the web is carried on
a first dryer run between the press and standard dryer section
being continuously supported so that no,flutter or'wrinkling can
' ' 'occur. During this first dryer run, the web is dxied from about
.
,' 40% bone dry as it is received from the press section and leaves
this run on the order of about 50~/O bone dry at which time it will
llave strengtll and s~a~-ility to withstand an open dràw in passing
through the rc,~gular clryer drum sectlon. The long continuous
.. ~ . ~ .` .
support o~l ~lle run is ~rovide(~ in ~he .~orrn o.~ an endless l~elt.
Difficulties have been encountered in such support in providin~
stability to the belt, accommodating evaporation of the moisture
from tlle web on the belt, imparting thermal energy at a sufficient
temperature to cause meaningful evaporation from the web during
the time it is supported and providing engagement between the web
and tlle ~elt without generating air pockets or 10ating of the web
such as causecl by inaclvertently cap~urin~, air between the.web and
the belt at hi~,h operating speeds.
It is accordingly a further object of the present inven-
tion to provide a mechanism which drives'the web between the press
section and dryer dru~ section by providing a long continuous
support ~or the web and providing for heated air impingement on
the we~b during its term of long continuous support.
~ further.object of the invention is to provide a support
means for the belt whic~h provides a long continuous support for the
web which is capable of stable operation or l.ong periods of time
which eliminates poclcets of alr beneatll the web, permits imparting
themlal energy to tlle web without damage to the ~elt and accommo-
dates satisactory high speed transfer to the belt from the press
section and from the belt to the dryer drums at the end of the
long continuous supported run.
.The invention provides' a continuous looped belt of porous
material capable of wi'thstanding the high temperatures o the
heated air, either i.nherently or by being provided with'a heat
.
- resistant coating on the upper surace and a roll with a suction
gland-on the lead end for transer of the we~ onto the belt without
inducing a cushion of air beneath the web, and a heated air gener-
a~ing means Eor d:irecL-ing a blanket of heated drying air continuously
onto tlle upper surfacF of the web T..Thile it is carried on the belt
--2--
,
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, _, _,, _ _ _ . _ A ~ _ . _ ~ ~ . _ . _ . _-- . ' -- ' ., . ..... _ _
support. 'll~e l)elt i5 SUp~)Or~"~ over a long sliglll:ly arclJ;1te path
on successive porous rolls with suctlon hoxes therebetween. l'hese
suction "bo~.es" Ir,ight more appropria~ely be characterized as suction
zones ~ltllin a single SUCtiOIl box e~tend;ng the length of the first
dryer run ~Inder the support ~)elt. The porous rolls themselves
define the sicles of tllese zones ~ith the ends ~eing constructed of
sheet nletal. '.I'Ilere are no tops since the belt is supported be-
tween successive poro~s roll.s over each zone. The rolls are per-
foratc and have suction ventilati:ng glands therein ~so that alr is
removed beneath the porous belt. Between the spaced parallel rolls
are the suction zones wi~h curved edge surfaces. At the end of
the long continuous run is a roll within the belt, preferably an
ordinary heated dryer drum roll, over which the belt and web pass
immedi.ately beEore the ~eb is tllreaded onto a felt to pass throu~h
the dryer drum section.
Other objects, advantages and features as well as equiv-
alent structures and methods which are intended to be covered here-
in, will become more apparent with the teaching of the principles
of the invention in connection with the disclosure of the preferred
embodiments in the specification, claims, and drawings, in which:
DI~AII~IGS
- FIGURE 1 is a side elevational view in somewhat schematic
form of a dewatering section of a paper making machine constructed
and operating in accordance with the principles of the present
invention; ~ - :
~ I~UR~ 2 is an enlarged detailed side elevational view,
partially in section, of a portion of the first thermal drying run;
FIGURE 3 is a fragmentary schematic view o~ a suction
arrangement for the rolls and suction box;
~ IGUR~ i.s a ~ragmentary detailed view of the suction
box structure;
.. . _ . . .. _ _ . .. .. _ , . .. . ..
I'ICUK1' S is a fragmentary schematic side elevational vie~
somewllat en3.ar~e~1 lrom ~igurc l illustra~ing the entering end o~
the first dryer section;
~ IGI]RE 6 is a fragmentary dia~ram~atic side elevational
view slightly enlar~ed ~rom ~igure l showing the discharge end of
the ~irst dryer section; and
FIGURE 7 is a ~ragtnentary side e].evational view similar
to Fi~ure 2 showing an alternate form of tlle invention.
DI~SCNPTION -'
As illustrated in Fi~ure l, a we~ web 1~ which has been
formed in a forrning section, is passed through a press section lO.
Therea~ter the web is thermally driecl in a first drying run ll
while being continual].y supported to avoid fluttering and wrinlcling.
Followin~ the n1n ll, t11e web is transferred to the second thermal
run 12 w11ic1~ comprises standard dryer drums. In the first or
intermediate run ll, the web enters rom t1~e press section at a
dryness o~ about ~0~/0 bone dry, and in that condition does not have
su~icient strength to stand the ~lutterin~, to which it will be
subjected i~ it is passed directly to a dryer drum section. The
web, therefore, receives full support in such a manner that air
currents cannot cause flutter when it is drled to a bone dryness
on the order of 50% at which time it has sufficient strength to be
handled by a standard dryer section and can withstand the flutter-
ing which occurs.
The web is i.llustrated leaving the press section, pas~ing
through a last press nip between press rolls 13 and l4 having a
felt 15 passing theough the nip. The elt passes upwardly over
Ielt roll 9 ~or its returll run. The web passes downwardly over
a roll l4a and is laid onto a long continual support belt 16. The
belt ex~ends ~or a suls~ant:ial run beln~ supported in a sli~htly
arcuate path as illustrated so that the bPlt can be tensioned and
held ~ithout any up and down movement or flutter itself.
At the lead end of the long continuous support run of the
belt 16 is a belt support roll 17 having a small suction gland 18
therein to flrmly transfer the web onto the belt. The web passes
over a roll 19 which is adjustable in position as shown by the
dotted lines l9a so as to control the location where the web is
laid onto the belt relative to the suction gland 18, for threading.
The web is carried on the upper surface of the belt, and the
belt is formed of a porous material and has a surface extending
across the full width of the web and providing full and complete
support therefor. While on the belt, the web is subjected to a
flow of drying air from above from a mechanism of the type known
in the art as an air cap. Inasmuch as the web is supported only
from below, the possibility of scuffing which could occur if the
web is carried between two belts is avoided. The porous belt is
preferably coated on its upper surface with a heat resistant
material of a type which can withstand air drying temperatures up
to 500F, 245C. The belt is preferably maintained at a tension
to reduce the possibility of wrinkling or ~luttering, and tensions
up to 30 pli are preferred. These tensions are maintained by
stretch rolls, not shown, within the looped belt. By training the
belt over an arcuate surface, this tension is readily maintained in
such a manner so that the web receives continual nonfluttering
support. It will be noted that with the effect of training the
belt over an arcuate path, that is, over an upwardly curved convex
path, the web is maintained taut or under a slight tension as it
is bowed upwardly on the belt to thereby help insure that no
wrinkles or fluttering occur in the web~
Above the belt are arranged air caps 22. These are supplied
with a flow of heated air to be able to deliver air of a temper-
ature o~ a ~uficient degree that can be~withstood by the belt and
and temperatures of up to 500F have been utilized successfully,
, ;~,
"~
v ... .
and it is believed under certain conditions that temperatures up
to 900F, 480C may be used.
The air caps are constructed as enclosures with perforate
lower surfaces 24 as illustrated in Figure 2. The air caps are
arranged to extend the full width of the belt and web, and arrange-
ments can be provided so that cooling air may be directed against
the belt surface at the exposed edge of the beltno-t covered by the
web to prevent its being damaged by being directly exposed to the
heated air.
Support for the continuous belt is provided by a series of
spaced horizontal support rolls 20. These rolls have a hollow
construction as shown in Figure 2 with a compartment 26 therein
extending for the length of the roll, and the roll has a perforate
outer shell surface. Suction is applied to the compartment 26
through a suction line 27 so that a continual slight vacuum will
be applied to the lower surface of the belt preventing any build
up of air therebeneath due to the induced flow of air with rotat-
ion of the rolls 20 or to the layer of air carried by the travel-
ing belt.
Between each of the rolls is a suction box 21 with the first
box meeting the oncoming web being tilted toward the oncoming
direction of the belt. Inasmuch as the belt is under tension, it
will tend to be stretched tangentially between its points of
contact with the upper surface rolls butwill depend slightly in a
catenary curve. The top edges 28 of the sides of suction boxes 21
are curved to conform substantially to the curvature o~ the belt
between the rolls~ The end walls of the suction box are made of
sheet metal, and at the upper edges 28 of the end walls are plastic t
shoes 29 for nonwearing engagement with the belt.
Suction is applied to the compartment 26 within the rolls and
into the interior of the suction box 21 provided by separate
suction pumps 30, 30a, Figure 3, wHich connects through suitable
lines 31, 31a to the rolls and suction boxes. Control of the
- 6 -
, .
. ..
applied suction is accomplished by a valving axrangement shown
somwhat schematically at 32 and 37. The suction which is applied
beneath the belt is rela-tively light an on the order of 1" - 2"
H2O, although at threading a higher suction is applied. When
threading a web through the machine, the web will have a leading
tail which will be less width than the full width web and to in-
sure retention of the tail and threading of the web, a higher
suction on the order 4" H2O is applied. This is done by setting
of the valves 32 and 37 to the higher suction during threading
and then shifting to a position of the regular suction during
normal operation. The web is dewatered and begins at 35% to 45%
bone dry at the beginning of a run and is dried to 45% to 55% bone
dry at the end of a run.
With this arrangement, two important objectives are provided
in that the web is being dried from about 40% bone dry at the run
beginning to about 50% bone dry at the end of the run while
simultaneously being continually supported without any possibility
of flutter or wrinkle. The other objective which is served is the
support of the web on a belt with the spoiling of any induced air
cushion which might tend to form between the web and supporting
belt and between the belt and supporting rolls 20. This is achiev-
ed by the fact that there is no open draw which supports the
objective of continuous support and avoids the inducement of air,
and the spoiling of air layers is additionally achieved by the
application of suction beneath the porous belt.
Preferably, the suction compartments 26 in rolls 20 are
slightly tilted toward the oncoming felt so this additionally
functions to spoil any wedge of induced air which tends to be
carried between the felt and pass up to cushion the web on the
belt.
The air caps have a perforated plate on the bottom, as
shown at 24 in Figure 2, and the holes in this plate are on the
~ ~ 2 ~
order oF al)proximl~tely 3/3" in diame~er. ~ir -is blown throu~h the
distribution of holes onto tlle web at a velocity o~ about 24,000
feet per minute at the temperature of abo~ 500F. This temper-
ature, oE course, will be increased in accordance with the-ability
of the bel~ ~o witlls~and hea~. At the downstream or terminal end
of the Eirs~ run where the web is supported on the belt, inside
tlle belt is a heated roll 33 ~hich provides additional drying heat,
but pri.marily ~unctions as a driving roll for the belt. For
heatin~ the roll, a steam li.ne 34 is connected to a gland at the
end of the hollow roll. At the location of the roll 33, an upper
felt 35 comes down onto the web and the web is transferred onto
the felt to pass down with the felt over a roll 36. A lower felt
37 receives the web and the ~elts pass over dryer rolls 38 and 39
in serpentine fashion in a normal manner. At this point the web
~ill have heen dried to substantially 50% bone dry so it will have
the strength to be carried through the dryer.drums.
. With thls arrangement, speeds on the order o 4,000 feet
per minute and higher can be accomplished without damage to the
web. The drying o the web in the irst or intermediate run be-
tween the press and tlle dryer drums does no~ only dry the web to
a degree where it has strength because o~ its dryness, but has
dried it in a fashion while under continuous suppor~ without ~lex-
ure which increases its strength.
Figure S shows in greater detail the manner in which the
paper web i5 ~ed from the press section onto the ~irst dryer: -
secti.on. In initial threading, tbe web is run through the press
section by feeding a tail (a narrow strip of web) as ~ed through
the press xection and passed directly downwardly following the
last press nip orF o~ the pre.ss roll 14 A doctor blade 41
against tlle surEace oF thc press roll 1.4 de1ects the web tail 40
,t..
.
. .. _. _
do~nwardly in~o tlle broke pi~ hen ~he web is established full
wicltl~, tlle tail is cut an(l tlrea(led tl.lrou~ll tl~e dryer. For this
threadin~,, thc roll 19 is in tl~e ri~hthand dotted line position
l9a shown in ~igure 5. ~hen ~lle tail has been established through
the drycr, roll ].9 is tllen movecl to lts solid li.ne position and
the web i.s expanded to its Eull wi.dtll. The web tension over the
rolls in tlle drver is aided by the fact that tlle dryer section is
operated at a aster linear speed than the press section.
Fig. 6 illustrates the path of the web and the position
. .
oE rolls at the running position an~d threading position at the
finishing of the Eirst dryer section where the weo is Eed to thé
second dryer section.
~ s illustrated in Figure G, Eor threading~ the felt roIl
42 is brougl~t into the lower solid line positlon, and the tail
led across ~he space to the dryer rolL 36 it~tediately following the
felt guide roll 44. The dryer roll 36 is sometimes reerred to as
a "baby dryer" and operates to secure the web to the felt 35. A
large dryin~, capacity is not neecled for tllis dryer roll because of
the small wrap. The web then continues do~n on the upper felt
where it is received by the lower felt ~7. ~fter threaciing, the-
roll 42 is moved up to the dotted line positlon which is its normal
operating position.
As illustrated in Figure 7, a structure differen~ from
.
Figure l t~lay be employed in that instead~of the suction rolls,
grooved rolls 46 are employed between each of the suction zones
21 supporting tlle belt 15. The grooved rolls have a plurality of
adjacent circumEerential grooves 45 along their surface, and it
has been discovered that the.se operate to remove air from beneath
tlle belt 16 prevetltin~, any li~ting oE the web carriecl on the upper
surface of the belt.
'ri~us, it will be Seetl tllat we llavc provided an improved
metho(i an~ mecllanism whicll meets ~le objectives set ~orth and is
capable of improved use in a paper making machine or achieving
high speeds particularly in the making of newsprint.
. . .
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t
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