Note: Descriptions are shown in the official language in which they were submitted.
1340a82
An Ar~paratus For Sequentially Drying Both
Sides Of A Paper Web
BACKGROUND OF THE INVENTION
FIELD OF THE INVENTION
This invention relates to an apparatus for
sequentially drying both sides of a paper web. More
particularly, this invention relates to a BEL RUt~'"' type
drying section in which a first drying section dries one
side of the web and then a subsequent drying section dries
the opposite side of the web.
INFORMATION DISCLOSURE STATEMENT
In a conventional drying section of a BEL RUNTM type
configuration, the single felt section may be made up of
four groups of rollers. Typically, these groups include
drying rollers and suction rollers which provide no open
draw in their configuration because the paper web is always
supported by a dryer felt. As the web progresses from one
group of dryers to the next, the same side of the web is
always presented to the successive drying rollers.
However, in order to present the opposite side of the web
to a successive drying roller, it has been necessary in the
past to transfer an unsupported web to a subsequent dryer
felt.
So-called single-felted dryer sections were
subsequently utilized in which a joint run of the web and
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felt successively passed around upper and lower dryer drums
in a sinusoidal configuration. Although this arrangement
provided felt support for the web between successive upper
and lower dryer drums, the lower dryer drums were virtually
redundant in that the felt was sandwiched between the web
and the drying roller thereby greatly reducing any drying
of the web during passage around the lower drying rollers.
Furthermore, such single felted sections still did not dry
from both sides.
In the aforementioned BEL RUNT"' configurations and
single-felted dryers, problems exist in that only one side
of the web is dried during passage of the web through the
first few groups of dryers. Consequently, such arrangement
results in differences in surface strength and properties.
Additionally, the smoothness of the respective surfaces of
the web differ which is a problem when sheet paper is
required in which both sides of the sheet must have similar
characteristics. Also, curl and non-uniform response to
change in humidity have been problems with the
aforementioned dryer sections.
In an article published in WOCHENBLATT FUR
PAPIERFABRIKATIO:~T No. 16 of 1986, J. Linderot: "10 Jahre
Erfahrung mit Geschlossener Bahnfuhrung in der
Trockenpartie", pages 623-628, reference is made, on page
628, to a drying apparatus which includes a single-felted
section consisting of three BEL RUN single-tier dryer groups
and a fourth dryer group which is a single-felted two-tier
dryer group. Each BEL RUN group comprises a plurality of
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top-felted dryer drums and suction transfer rolls disposed
below and between adjacent dryer drums. The fourth dryer
group has top and bottom dryer drums and a single felt which
is sandwiched between the web and the bottom dryer drums .
A two-tier two-felt section for continuing the drying process
by drying the web directly from alternate sides is disposed
downstream relative to the fourth dryer group of the single-
felted section of the drying apparatus referred to in the
afore-mentionesd article. Such a drying apparatus is also
illustrated schematically in Fig. 1 of the accompanying
drawing and is considered to be the closest prior art.
An object of the present invention is to provide an
apparatus and a method which overcome the afore-mentioned
inadequacies of prior art drying apparatuses having BEL RUN
and single-felted dryer groups, and which permit a simple and
positive transfer of the web between successive dryer groups
of the single-felted section of the drying apparatus in a no-
open-draw-configuration such that both sides of the web can
be dried direcaly, thereby providing a paper product having
uniform surface characteristics, surface strength and
smoothness, and no tendency to curl.
According to one aspect of the invention, there is
provided an apparatus for drying a web of paper comprising
a substantially horizontally extending single-felted section
which is made up of a plurality of successively arranged,
substantially horizontally extending single-tier dryer groups
each of which has a plurality of dryer drums and a plurality
of suction transfer rolls which are smaller in diameter than
the dryer drums and disposed between and below or above
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adj acent dryer drums ; and means for supporting the web during
its transfer between adjacent single-tier dryer groups; said
plurality of single-tier dryer groups including a first
single-tier dryer group having its dryer drums rotating in
a first direction for drying the web from only one side
thereof, and having its suction transfer rolls rotating in
a second direction opposite to said first direction, and
including a first dryer felt for conveying the web in a
serpentine path along the dryer drums and suction transfer
rolls of said first single-tier dryer group so that said one
side of the web comes into physical contact with the dryer
drums of said first single-tier dryer group; a second single-
tier dryer group which is disposed substantially horizontally
adjacent to and downstream of said first single-tier dryer
group, said second single-tier dryer group having its dryer
drums rotating in said second direction for drying the web
only from the other side, and having its suction transfer
rolls rotatin~~ in said first direction, and including a
second dryer felt for conveying the web in a serpentine path
along the dryer drums and suction transfer rolls of said
second single-tier dryer group so that said other side of the
web comes into physical contact with the dryer drums of said
second single-tier dryer group; said means for supporting the
web during its transfer between adjacent single-tier dryer
groups including said first and second dryer felts; and felt
guiding means for guiding said first and second dryer felts
in close proximity to each other between said first and
second single--tier dryer groups so as to sandwich the web
between said first and second dryer felts; said felt guiding
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means including a further suction transfer roll for effecting
a controlled transfer of the web from said first dryer felt
to said second dryer felt so that the web is reversed for
bringing said other side of the web into physical contact
with the dryer drums of said second single-tier dryer group.
According to another aspect of the invention there is
provided a method of drying a web of paper, said method
including the steps of: guiding the web through a
substantially horizontally extending single-felted section
which is made up of a plurality of successively arranged,
substantially horizontally extending single-tier dryer groups
each of which has a plurality of dryer drums and a plurality
of suction transfer rolls which are smaller in diameter than
the dryer dn~ms and disposed between and below or above
adjacent dryer drums; and supporting the web during its
transfer between adjacent single-tier dryer groups; said step
of guiding the web through a substantially horizontally
extending single-felted section including the sub-steps of:
guiding said web through a first single-tier dryer group
having its dryer drums rotating in a first direction for
drying the we:b from only one side thereof , and having its
suction transfer rolls rotating in a second direction
opposite to said first direction, conveying said web
contiguously with a first dryer felt such that the web and
said first dryer felt follow a serpentine path along the
dryer drums and suction transfer rolls of said first single-
tier dryer group so that said one side of the web comes into
physical contact with the dryer drums of said first single-
tier dryer group; guiding the web through a second single-
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tier dryer group which is disposed substantially horizontally
adjacent to and downstream of said first single-tier dryer
group, said second single-tier dryer group having its dryer
drums rotating i:n said second direction for drying the web
only from the other side, and having its suction transfer
rolls rotating in said first direction, conveying the web
contiguously with a second dryer felt such that the web and
said second dryer felt follow a serpentine path along the
dryer drums and suction transfer rolls of said second single-
tier dryer group so that said other side of the web comes
into physical contact with the dryer drums of said second
single-tier dryer group; said step of supporting the web
during its transfer between adj acent single-tier dryer groups
including the su.b-steps of : guiding said first and second
dryer felts in close proximity to each other between said
first and second single-tier dryer groups so as to sandwich
the web between said first and second dryer felts; and
guiding said second dryer felt around a further suction
transfer roll for effecting a controlled transfer of the web
from said first dryer felt to said second dryer felt so that
the web is reversed for bringing said other side of the web
into physical contact with the dryer drums of said second
single-tier dryer group.
The present invention seeks to overcome the
aforementioned problems associated with the BEL RUIN''" and
other single-fE~lted dryer section configurations by
providing a web transfer section defined by a first and
second felt such that the web is sandwiched between the
felts during pa:~sage through the transfer section so that
during movement of the web around a subsequent drying
roller, the
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opposite side of the web comes into physical contact with
the heating surface of the subsequent drying roller.
Therefore, it is a primary object of the present
invention to provide an apparatus that overcomes r_he
aforementioned inadequacies of the prior art proposals and
which makea a significant and non-obvious contribution to
the paper clrying art.
Another object of the present invention is the
provision of an apparatus in which a first felt is a
continuous loop which extends in sinusoidal configuration
past alternate drying and suction rollers and in which the
second felt: is a continuous loop which extends in sinu-
soidal coni:iguration past alternate drying and suction
rollers such that the first plurality of drying rollers
physically contacts the first side of the web and the
second plurality of drying rollers physically contacts the
second side of the web so that alternate sides of the web
are sequentially dried.
Another object of the present invention is the
provision of a method of sequentially drying alternate
sides of the web which includes guiding a joint run of the
web and a first felt around a first drying roller such
that the web is sandwiched between the first felt and the
first drying roller for heating a first side of the web.
The joint run is thereafter guided around a first suction
roller such that the first felt is sandwiched between the
web and the first suction roller. A second felt is guided
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from a second guide roll around a second suction roller
such that the first and second felt define therebetween a
web transfer section so that the web, supported by the
first felt, is guided into the web transfer section with
the web being disposed between the first and second felts,
drawing they web emerging from the web transfer section
around the second suction roller such that the second felt
is disposed between the web and the second suction roller
and thereafter directing the joint run of the web and the
second felt around a second drying roller such that the
web is sandwiched between the second felt and the second
drying roller for heating a second side of the web.
Other objects and advantages of the present invention
will be apparent to those skilled in the art by a con-
sideration of the detailed description taken in conjunc-
tion with the annexed drawings and the appended claims.
SUMMARY OF THE INVENTION
This invention relates to an apparatus and method for
sequentially drying both sides of a paper web. The
apparatus includes a first drying roller in which the web
extends around a portion of the circumference of the first
drying roller. The first felt extends around the portion
of the first drying roller such that the web is sandwiched
between the first felt and the first drying roller for
heating a first side of the web. A first suction roller
is disposed downstream relative to the first drying roller
with the first suction roller having an axis of rotation
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disposed parallel and spaced relative to the rotational
axis of the first drying roller. The first felt and the
web extend around a portion of the circumference of the
first suction roller such that the first felt is sand-
wiched between the web and the first suction roller. A
first guiding means guides the first felt away from the
first suction roller and a second suction roller is
disposed acljacent to the first suction roller with the
second suction roller having an axis of rotation parallel
and spaced relative to the axis of rotation of the first
suction roller. A second felt extends around the second
suction roller and a second guiding means guides the
second felt towards the second suction roller such that
the first and second felts define therebetween a web
transfer section so that the web is sandwiched between the
felts during passage through the transfer section. A
second drying roller is disposed downstream relative to
the second suction roller with the second drying roller
having an axis of rotation parallel to the axis of rota-
tion of the second suction roller such that the web is
sandwiched between the second felt and the second drying
roller for heating a second side of the web.
In a more specific embodiment of the present in-
vention, the first felt is a continuous loop which extends
in sinusoidial configuration past alternate first drying
and suction rollers.
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Furthermore, the second felt is a continuous loop
which extends in sinusoidal configuration past alternate
second drying and suction rollers such that the first
drying rollers physically contact the first side of the
web and thE~ second drying rollers physically contact the
second side of the web so that alternate sides of the web
are sequentially dried.
The first guiding means includes a first guide roll
for guiding the first felt and the second guiding means
includes a second guide roll for guiding the second felt.
The present invention also includes a method for
sequentially drying alternate sides of a paper web wherein
the method includes the steps of guiding a joint run of
the web and a first felt around a first drying roller such
that the web is sandwiched between the first felt and the
first drying roller for heating a first side of the web.
Thereafter, the joint run of the web and first felt is
guided around a first suction roller such that the first
felt is sandwiched between the web and the first suction
roller. The first felt is then guided around a first
guide roll and a second felt is guided from a second guide
roll around a second suction roller such that the ffirst
and second felts define therebetween a web transfer
section so that the web supported by the first felt is
guided into the web transfer section with the web being
disposed between the first and second felts. The web
emerging from the web transfer section is drawn around the
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second suction roller such that the second felt is disposed
between the web and the second suction roller. Thereafter,
the joint run is directed around a second drying roller
such that the web is sandwiched between the second felt and
the second drying roller for heating a second side of the
web.
Although the present invention is described with a
certain degree of particularity in the detailed description
contained here=_inafter, it will be apparent to those skilled
in the art that many modifications and variations of the
concept of the present invention can be carried out without
departing the spirit and scope of the present invention as
defined by he appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a side-elevational view of a prior art BEL
RU1~'" type drying section showing the first four groups of
drying rollers drying a first side of a paper web.
Figure 2 is a side-elevational view of a BEL RUNz'~' type
drying configuration according to the present invention
showing the means for transferring the web without open
draw from a first to a second felt, and
Figure _s is an enlarged side-elevational view of
Figure 2 particularly showing, in detail, the web transfer
section enabling the opposite side of the web to come into
physical contact with a subsequent group of drying rollers.
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Similar reference characters refer to similar parts
throughout the various figures of the drawings.
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DETAILED DESCRIPTION OF THE DRAWINGS
Figure 1 is a side-elevational view of a conventional
BEL RUN type drying section including groups A,B,C and D
for drying a web of paper 1. As shown in figure 1, the
web 1 is guided in sinusoidal configuration around a
plurality of drying rollers 2, 2' and 2" and suction
transfer rollers 3, 3' and 3". A first felt 4 loops
around a plurality of guide rolls 5, 5',5",5"' and 5"" and
supports the web 1 as the web moves alternately past
drying and suction rollers 3, 2, 3' , 2' , 3" and 2" . A
second group B of drying rollers 6, 6', and 6" have
suction rollers 7, 7' and 7" disposed alternately
therebetween such that a second felt 4' loops around the
suction ancf drying rollers 7, 6, 7', 6', 7" and 6" in
sinusoidal configuration. The web 1 is unsupported by the
felt 4 as the web 1 supported by the drying roller 2"
rotates adjacent to the second felt 4' so that the web 1
is transferred to the second felt 4' and around the
suction roller 7. However, as seen in figure 1, the same
side 8 of the web 1 is brought into contact with the
heating surfaces of the drying rollers 2, 2' , 2", 6, 6'
and 6" so that the same side 8 is dried.
The present invention, as shown in figure 2, enables
the web lA to be reversed from a first section A1 to a
second section B1 so that during passage of the web lA
through the first section A1, a first side 8A of the web
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lA comes into physical contact with the drying rollers
2A, 2A' and 2A". In the second group, B1, a second side
9 of the web lA comes into physical contact with the
heating surface of drying rollers 6A, 6A' and 6A".
Figure' 3 is an enlarged, fragmentary view of the
transfer section shown in figure 2 to show how the web lA
is reversed. More particularly, with reference to figure
3, the apparatus generally designated 10 for sequentially
drying both sides 8A and 9 of a paper web lA includes a
first drying roller with the web extending around a
portion of: the circumference of the first drying roller
2A". A first felt 4A extends around a portion of the
first drying roller 2A" such that the web lA is sandwiched
between the first felt 4A and the first drying roller 2A"
for heating a first side 8A of the web lA. A first
suction roller 3A"' is disposed downstream relative to the
first drying roller 2A". The first suction roller 3A"'
has an axis of rotation which is disposed parallel and
spaced relative to the rotational axis of the first
drying roller 2A". The first felt 4A and the web lA
extend around a portion of the circumference of the first
suction ro:Ller 3A"' such that the first felt 4A is
sandwiched between the web lA and the first suction roller
3A"'. Fir;>t guiding means 5A, as shown in figure 2,
guide the first felt 4A away from the first suction roller
3A"'. A second suction roller 7A is disposed adjacent to
the first ruction roller 3A"', the second suction roller
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?A having an axis of rotation parallel and spaced relative
to the axis; of rotation of the first suction roller 3A"'.
A second felt 4A' extends around the second suction roller
7A and a second guiding means 12 shown in figure 2 guides
the second felt 4A' towards the second suction roller 7A
such that the first and second felts 4A and 4A'
respectively define therebetween a web transfer section
generally designated 14 so that the web lA is sandwiched
between the felts 4A and 4A' during passage through the
transfer sE~ction 14. A second drying roller 6A is
disposed downstream relative to the second suction roller
7A with the second drying roller 6A having an axis of
rotation parallel to the axis of rotation of the second
suction roller ?A such that the web lA is sandwiched
between the second felt 4A' and the second drying roller
6A for heating the second side 9 of the web lA.
As shown in figure 2, the first felt 4A is a
continuous loop which extends in sinusoidal configuration
past alternate drying and suction rollers 3A, 2A, 3A', 2A'
3A", 2A" and 3A"' such that the drying rollers physically
contact the first side 8A of the web lA and the second
plurality of drying rollers 6A, 6A' 'and 6A" physically
contact the second side 9 of the web lA so that alternate
sides of the web lA are sequentially dried.
More specifically, the first guiding means includes a
first guide roll 5A for guiding the first felt 4A and the
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second guiding means includes the second guide roll 12 for
guiding the second felt 4A'.
In opEeration of the present invention, alternate
sides 8A and 9 of the paper web lA are sequentially dried
by the following process steps:
1. The joint run of the web lA and the first felt 4A are
guided around the first drying roller 2A" as shown in
figure 3 such that the web lA is sandwiched between
the first felt 4A and the first drying roller 2A" for
heating the first side 8A of the web lA.
2) Thereafter, the joint run of the web lA and the first
felt 4A are guided around a first suction roller 3A"'
such that the first felt 4A is sandwiched between the
web lA and the first suction roller 3A"'.
3. The first felt 4A is guided around a first guide roll
5A and a second felt 4A' is guided from a second
guide roll 12 around a second suction roll 7A such
that the first and second felts 4A and 4A'
respectively define therebetween a web transfer
section 14 so that the web lA supported by the first
felt 4A is guided into the web transfer section 14
with the web lA being disposed between the first and
second felts 4A and 4A' respectively.
4. The web lA emerging from the web transfer section 14
is drawn around the second suction roller 7A such
that the second felt 4A' is disposed between the web
lA and the second suction roller 7A.
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5. Thereafter, the joint run of the web lA and second
felt 4A' is directed around a second drying roller 6A
such that the web lA is sandwiched between the second
felt 4A' and the second drying roller 6A for heating
the second side 9 of the web 1A.
The pre~~ent invention provides a simple means for
positively transferring the web between successive groups
of dryers in a BEL RUNT"' configuration such that alternate
sides of the web may be dried thereby providing a paper
product having uniform surface characteristics, surface
strength and smoothness, and no tendency to curl.
In the :First dryer group, the suction rollers are
disposed below the drying rollers whereas in the second
group of dryers, the suction rollers are disposed above the
drying rollers. This configuration enables the provision
of the aforementioned simple web transfer section such that
the web may be transferred from the first to the second
felt.
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