Note: Descriptions are shown in the official language in which they were submitted.
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A SEALING ARRANGEMENT FOR SEALING BETWEEN A FIRST DRUM AND
AN END CASING MEMBER
Technical Field
The present invention relates to a sealing arrangement for sealing be-
tween a first drum and an end casing member included in an apparatus for proc-
essing pulp, especially cellulose-containing pulp, the first drum being
rotatable
about an axis of rotation in relation to the end casing member and the sealing
ar-
rangement. The first drum is provided with a permeable outer surface which
axially
extends between a first end and a second end of the first drum, and at least
at the
first end the first drum is provided with an end surface. The sealing
arrangement
comprises a sealing member, first pressure means for forcing the sealing
member
in a direction towards the first drum to make the sealing member bear against
a
portion of the end surface, a circumferentially extending sealing element held
by a
holder, and second pressure means for forcing at least a first portion of the
sealing
element in a direction towards the first drum to make the first portion bear
against
a portion of the end surface. The holder is arranged to hold the second
pressure
means, and a terminal second portion of the sealing element is in proximity to
the
sealing member. Further, the present invention relates to an apparatus for
proc-
essing pulp comprising a sealing arrangement of the above-mentioned sort.
Background of the Invention
Fibre lines producing cellulose-based products may comprise some type
of washing equipment for separating the liquor of the cooking from the pulp.
Later
on in the process, washing equipment is also provided to separate bleaching
liq-
uors after the bleaching steps. There is a plurality of different types of
washing
equipment operating according to different principles.
When producing cellulose-based products, a roll press is frequently used
for washing and/or dewatering the cellulose-based pulp. The roll press
comprises
two co-operating and counter-rotating press rolls, each having a permeable
outer
surface, a so called mantle surface, whereby the outer surface is permeable to
liq-
uid pressed out of the pulp. The pulp is deposited on the permeable outer
surface
and pressed in the roll nip, or the press nip, between the press rolls,
whereby liq-
uid is pressed out of the pulp. The roll press may also include one or more
wash-
ing zones prior to the press nip. One example of such a roll press is
disclosed in
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US 3,980,518, where the axes of rotation of the press rolls are lying in
substan-
tially the same horizontal plane. The pulp is fed in the direction of rotation
of the
press rolls through the press nip and the pulp passes the press nip between
the
press rolls from below upwards. Another example of a roll press is disclosed
in
W02009/075642.
Another known washing equipment is the drum washer, where the cellu-
lose-containing pulp is deposited and dewatered on a single rotating filter
drum,
which has a permeable outer surface, after the addition of washing liquid,
which
displaces the liquor remaining on the pulp web after the preceding process
step,
for example a cooking step or bleaching step. The static pressure causes the
contaminated liquid, called filtrate, to pass through the outer surface
permeable to
liquid. A further development of the original drum washer is the pressurized
dis-
placement washer, where the filtrate, under overpressure, is forced to pass
through the permeable outer surface.
In general, around at least a portion of the circumference of the permeable
outer surface of the drum or press roll, an axially extending and
circumferential
gap or space may be provided which is sealed off from the atmosphere to
produce
an overpressure in order to force the filtrate from the pulp, which is located
on the
outer surface in said gap, to pass through the permeable outer surface. By
means
of the sealed-off gap, the dewatering of the pulp is enhanced. Sealing arrange-
ments including a plurality of components are generally required to seal off
such a
gap. W02010/036193 discloses sealing arrangements for sealing between a mov-
able side casing member and the outer surface of a rotatable press roll,
between
the movable side casing member and an end casing member, and between the
movable side casing member and a central casing member. Further, sealing ar-
rangements for sealing between each end of a rotatable press roll and the end
casing member may also be required. In the detailed description below, a prior
art
sealing arrangement for sealing between an end of a rotatable drum, or roll,
and a
stationary end casing member is illustrated and disclosed in more detail with
refer-
ence to Figs. 10-11. Further, a drum washer may also be equipped with a corre-
sponding sealing arrangement for sealing between an end of the rotatable
single
filter drum and an end casing member.
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The Object of the Invention
The inventors of the present invention have identified drawbacks in prior
art sealing arrangements for sealing between a rotatable drum and a stationary
end casing member in an apparatus for dewatering pulp, especially cellulose-
containing pulp. One drawback identified by the inventors is that pulp may get
jammed between the rotatable drum and the sealing arrangement for reasons dis-
closed in more detail in connection with Figs. 10-11. The jammed pulp may
result
in leakage of pulp suspension and/or filtrate and may result in increased wear
on
the rotatable drum and on the sealing arrangement. Further, if the sealing
function
is impaired, the pressure within the sealed-off gap or space may not be
maintained
which impairs/deteriorates the dewatering efficiency.
The object of the present invention is thus to provide an improved sealing
arrangement for sealing between a rotatable drum and a stationary end casing
member of an apparatus for dewatering pulp.
A further object is to provide an improved sealing arrangement for sealing
between a rotatable drum and a stationary end casing member of an apparatus
for
dewatering pulp, where the above-mentioned problems in prior art are overcome.
Summary of the Invention
The above-mentioned objects of the present invention are attained by
providing a sealing arrangement for sealing between a first drum and an end
cas-
ing member included in an apparatus for processing pulp, especially cellulose-
containing pulp, the first drum being rotatable about an axis of rotation in
relation
to the end casing member and the sealing arrangement, and the first drum being
provided with a permeable outer surface which axially extends between a first
end
and a second end of the first drum, and at least at the first end the first
drum is
provided with an end surface, the sealing arrangement comprising
a sealing member,
first pressure means for forcing the sealing member in a direction towards
the first drum to make the sealing member bear against a portion of the end
sur-
face,
a circumferentially extending sealing element held by a holder, and
second pressure means for forcing at least a first portion of the sealing
element in a direction towards the first drum to make the first portion bear
against
a portion of the end surface, the holder being arranged to hold the second
pres-
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sure means, and a terminal second portion of the sealing element is in
proximity to
the sealing member, wherein the sealing arrangement comprises means for forc-
ing the second portion of the sealing element in a direction towards the first
drum
to make the second portion bear against a portion of the end surface, and
wherein
the means for forcing the second portion of the sealing element in a direction
to-
wards the first drum are separate from the second pressure means.
By means of the sealing arrangement according to the present invention,
the terminal second portion of the sealing element is efficiently and
sufficiently
pressed against the end surface, thus preventing pulp from getting jammed be-
tween the sealing element and the end surface, and also preventing pulp from
getting jammed between the sealing member and the end surface. Consequently,
the wear on the end surface, on the rotatable drum and on the sealing element
is
efficiently decreased. Further, leakage of pulp suspension and/or filtrate is
avoided, since the sealing function is not compromised by jammed pulp forcing
the
terminal second portion of the sealing element and/or the sealing member away
from the end surface. Thus, by means of the present invention, an improved
seal-
ing between a rotatable drum and a stationary end casing member of an appara-
tus for dewatering pulp is provided, and the processing of pulp in the
dewatering
apparatus is improved.
Each pressure means may be in the form of a pressure member, a pres-
sure unit or pressure equipment. The first pressure means may comprise basing
means, e.g. a compression spring, a leaf spring, a torsion spring or bar, a
volute
spring etc, or may comprise other pressure means, e.g. pressure means actuated
by a pressurized fluid, such as gas or liquid, etc, or other suitable pressure
means.
The sealing member may be rigid, and may, for example, be made of a
polymer material. The sealing element may be made of a polymer material. The
second pressure means may comprise an inflatable tube of a flexible material,
e.g.
a polymer material. The holder may be in the form of a circumferentially
extending
holder, and may e.g. comprise a circumferentially extending groove which may
hold the second pressure means and the sealing element. The sealing element
may be elongated in the circumferential direction. The end surface may be
formed
by a solid circular plate, or by an end ring, or any other structure of the
first drum.
The end surface may be in the form of an annular surface surrounding the axis
of
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rotation or an annular surface portion surrounding the axis of rotation. The
annular
surface or surface portion may be formed by an end ring.
The sealing arrangement may comprise locking means for circumferen-
tially, or tangentially, locking the second portion of the sealing element to
prevent a
5 movement of the second portion and the sealing element in the
circumferential
direction, to avoid a dislocation of the sealing element in the
circumferential direc-
tion. The sealing arrangement may comprise a guide unit for guiding the
sealing
member. The locking means may be arranged to lock the second portion of the
sealing element to the guide unit, to the holder or to the sealing member, for
ex-
ample, or combinations thereof may also be possible. The sealing arrangement
may be defined as an end seal arrangement. The second portion of the sealing
element may be located outside of the holder, or more specifically, the second
portion of the sealing element may be located circumferentially outside of the
holder. The second portion of the sealing element may be located outside of
the
groove of the holder, or more specifically, the second portion of the sealing
ele-
ment may be located circumferentially outside of the groove of the holder.
According to an advantageous embodiment of the sealing arrangement
according to the present invention, the means for forcing the second portion
of the
sealing element in a direction towards the first drum are arranged to push the
sec-
ond portion of the sealing element in the direction towards the first drum. By
means of this embodiment, the sealing between a rotatable drum and a
stationary
end casing member is further improved.
According to a further advantageous embodiment of the sealing arrange-
ment according to the present invention, the means for forcing the second
portion
of the sealing element in a direction towards the first drum comprise biasing
means for biasing the second portion of the sealing element towards the end
sur-
face. This is an efficient manner to force the second portion of the sealing
element
towards the end surface, and the sealing between a rotatable drum and a
station-
ary end casing member is yet further improved.
According to another advantageous embodiment of the sealing arrange-
ment according to the present invention, the biasing means comprise at least
one
compression spring. This is an efficient way to force the second portion of
the
sealing element towards the end surface, and the sealing between a rotatable
drum and a stationary end casing member is still further improved.
Alternatively,
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the biasing means may comprise other springs, e.g. a leaf spring, a torsion
spring
or bar, a volute spring etc, or may comprise other pressure means, e.g.
pressure
means actuated by a pressurized fluid, such as gas or liquid, etc.
According to yet another advantageous embodiment of the sealing
arrangement according to the present invention, the means for forcing the
second
portion of the sealing element in a direction towards the first drum comprise
the
first pressure means. This is an efficient manner to force the second portion
of the
sealing element towards the end surface, as the first pressure means already
pre-
sent to force the sealing member are used, and thus, no additional pressure
means are required. Thus, the sealing between a rotatable drum and a
stationary
end casing member is further improved. Alternatively, the means for forcing
the
second portion of the sealing element in a direction towards the first drum
are
separate from the first pressure means. The means for forcing the second
portion
of the sealing element in a direction towards the first drum may comprise
third
pressure means acting on the second portion of the sealing element. The third
pressure means may e.g. be structured in a corresponding way as the first pres-
sure means, and may be separate from the first pressure means.
According to still another advantageous embodiment of the sealing
arrangement according to the present invention, the sealing member and the sec-
ond portion of the sealing element comprise complementary guiding means en-
gaging one another, and the guiding means are arranged to guide the second por-
tion of the sealing element in a direction towards the first drum. This is an
efficient
way to force the second portion of the sealing element towards the end
surface,
and the sealing between a rotatable drum and a stationary end casing member is
still further improved.
According to an advantageous embodiment of the sealing arrangement
according to the present invention, the guiding means comprise a recess and a
projection engaging the recess. This is an efficient way to force the second
portion
of the sealing element towards the end surface, and the sealing between a ro-
tatable drum and a stationary end casing member is further improved. However,
other guiding means are possible, e.g. two projections in engagement with one
another.
According to a further advantageous embodiment of the sealing arrange-
ment according to the present invention, the sealing member is provided with
the
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recess, and the second portion of the sealing element is provided with the
projec-
tion. This is an efficient way to force the second portion of the sealing
element to-
wards the end surface, and the sealing between a rotatable drum and a
stationary
end casing member is still further improved. Alternatively, the sealing member
is
provided with the projection, and the second portion of the sealing element is
pro-
vided with the recess.
According to another advantageous embodiment of the sealing arrange-
ment according to the present invention, the end surface forms an angle with
the
axis of rotation, the first pressure means are arranged to force the sealing
member
in an axial direction towards the first drum, the second pressure means are ar-
ranged to force the first portion of the sealing element in an axial direction
towards
the first drum, and the means for forcing the second portion of the sealing
element
are arranged to force the second portion of the sealing element in an axial
direc-
tion towards the first drum. By means of this embodiment, the sealing between
a
rotatable drum and a stationary end casing member is further improved.
According to yet another advantageous embodiment of the sealing
arrangement according to the present invention, each of the sealing member and
the sealing element is arranged to bear against a portion of an end surface
which
is substantially perpendicular to the axis of rotation of the first drum. By
means of
this embodiment, the sealing between a rotatable drum and a stationary end cas-
ing member is yet further improved. Alternatively, the end surface may be sub-
stantially parallel to the axis of rotation, the first pressure means may be
arranged
to force the sealing member in a radial direction towards the first drum, the
second
pressure means may be arranged to force the first portion of the sealing
element
in a radial direction towards the first drum, and the means for forcing the
second
portion of the sealing element may be arranged to force the second portion of
the
sealing element in a radial direction towards the first drum.
According to still another advantageous embodiment of the sealing
arrangement according to the present invention, each of the sealing member and
the sealing element is arranged to bear against a portion of an end surface
which
is in the form of an annular surface surrounding the axis of rotation or in
the form
of an annular surface portion surrounding the axis of rotation.
Further, the above-mentioned objects of the present invention are attained
by providing an apparatus for processing pulp, comprising at least one first
drum
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rotatable about an axis of rotation and provided with an outer surface
permeable to
liquid, the outer surface axially extending between a first end and a second
end of
the first drum, the apparatus is adapted to receive the pulp on the outer
surface of
the first drum and to process the pulp situated on the outer surface while
rotating
the first drum, and the apparatus is adapted to process the pulp by at least
dewa-
tering the pulp, the first drum being rotatably mounted to two end casing
members,
at least at the first end the first drum being provided with an end surface,
and at
least one of the end casing members holds a sealing arrangement for sealing be-
tween the first drum and the respective end casing member, the first drum
being
rotatable in relation to the sealing arrangement, wherein the sealing
arrangement
comprises the features mentioned in any of the claims 1 to 11, or the features
of
any of the above-mentioned embodiments of the sealing arrangement. By means
of the apparatus according to the present invention, an improved sealing
between
the rotatable drum and the stationary end casing member of the apparatus is
pro-
vided, and the processing of pulp in the dewatering apparatus is improved.
Further
positive effects resulting from the apparatus according to the present
invention and
its embodiments correspond to the effects mentioned in connection with the
vari-
ous embodiments of the sealing arrangement according to the present invention.
A
sealing arrangement according to the present invention may be provided for
each
end of the first drum.
According to an advantageous embodiment of the apparatus according to
the present invention, at least at the first end the first drum is provided
with an end
surface which is in the form of an annular surface surrounding the axis of
rotation
or in the form of an annular surface portion surrounding the axis of rotation.
According to a further advantageous embodiment of the apparatus accord-
ing to the present invention, the apparatus comprises a second drum rotatable
about an axis of rotation and provided with an outer surface permeable to
liquid,
the first and second drums defining a press nip between them, in which press
nip
the pulp is pressed, and the apparatus is arranged to feed the pulp through
the
press nip in the direction of rotation of the press rolls. The innovative
sealing ar-
rangement is particularly advantageous for an apparatus having two counter-ro-
tating press rolls forming a press nip. The sealing element may
circumferentially
extend, in the direction of rotation of the first drum, from the sealing
member to the
press nip, or past the press nip to a region after the press nip. A sealing
arrange-
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ment according to the present invention may be provided for each end of the
first
drum and the second drum, respectively. Thus, in a roll press with two drums,
four
sealing arrangements may be provided, where two sealing arrangements may be
held by the first end casing member and two sealing arrangements may be held
by
the second end casing member.
According to another advantageous embodiment of the apparatus accord-
ing to the present invention, at least one of the end casing members holds a
sec-
ond sealing arrangement for sealing between the second drum and the respective
end casing member, the second drum being rotatable in relation to the second
sealing arrangement, and the second sealing arrangement comprises the features
mentioned in any of the claims 1 to 11, or the features of any of the above-
men-
tioned embodiments of the sealing arrangement.
The above-mentioned features and embodiments of the sealing arrange-
ment and the apparatus, respectively, may be combined in various possible ways
providing further advantageous embodiments.
Further advantageous embodiments of the sealing arrangement and the
apparatus, respectively, according to the present invention and further
advantages
with the present invention emerge from the detailed description of
embodiments.
Brief Description of the Drawings
The present invention will now be described, for exemplary purposes, in
more detail by way of embodiments and with reference to the enclosed drawings,
in which:
Fig. 1 is a schematic side view of an apparatus provided with
an em-
bodiment of the sealing arrangement according to the present
invention;
Fig. 2 is a schematic top view of the of the vat segments of
Fig. 1;
Fig. 3 is a schematic perspective view of the first side casing
mem-
ber of the apparatus of Fig. 1 provided with sealing means ac-
cording to prior art;
Fig. 4 is a schematic partial view of the first end casing member of
Fig. 2 provided with an embodiment of the sealing arrange-
ment according to the present invention;
Fig. 5 is a schematic view of the first end of the first drum
of Fig. 1;
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Fig. 6 is a schematic partial top view of the sealing
arrangement of
Fig. 4 bearing against the first end of the first drum;
Figs. 7-9 are schematic partial perspective views of the sealing arrange-
ment of Fig. 4; and
5 Figs. 1 0-1 1 are schematic partial perspective views of a sealing
arrange-
ment according to prior art.
Detailed Description of Preferred Embodiments
Fig. 1 shows an embodiment of the apparatus for dewatering cellulose-
containing pulp provided with an embodiment of the sealing arrangement accord-
10 ing to the present invention. The apparatus may also be arranged to wash
the
pulp. The apparatus may have a substantially symmetric configuration with
regard
to a symmetry plane 101, and in Fig. 1, the left side of the apparatus, i.e.
to the left
of the symmetry plane 101, illustrates the apparatus in an opened position,
whereas the right side of the apparatus, i.e. to the right of the symmetry
plane 101,
illustrates the apparatus in a closed and operating position. The apparatus
may
comprise a first rotatable drum 102 or press roll and a second rotatable drum
104
or press roll, each drum 102, 104 having a permeable outer surface 106, 108.
Each permeable outer surface 106, 108 extends axially between a first end 503
and a second end of the respective drum 102, 104. The first drum 102 is
rotatable
about a first axis of rotation 107, and the second drum 104 is rotatable about
a
second axis of rotation 109. The drums 102, 104 may comprise a plurality of
fil-
trate channels 110 radially inwards of the outer surface 106, 108 to lead
evacu-
ated filtrate away. The two drums 102, 104 define a press nip 112 between
them,
in which press nip the pulp is pressed, and are arranged to rotate in opposite
di-
rections, as indicated by arrows R1 and R2. The apparatus may be arranged to
feed the pulp through the press nip 112 in a substantially vertical direction
from be-
low upwards, however, the pulp can be fed through the press nip 112 in other
di-
rections.
The apparatus may comprise a casing which includes a vat 114, 116, 118,
in which the drums 102, 104 are installed, the vat 114, 116, 118 partly
enclosing
the outer surface 106, 108 of each drum 102, 104, whereby a space or gap 124,
125 for each drum 102, 104 is defined, limited by the vat 114, 116, 118 and
the
outer surface 106, 108 of the respective drum 102, 104. The vat 114, 116, 118
may be built up of a first side vat segment 114 which partly encloses the
outer
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surface 106 of the first drum 102, a second side vat segment 116 which partly
en-
closes the outer surface 108 of the second drum 104, and a central vat segment
118 partly enclosing the outer surface 106, 108 of the drums 102, 104 between
the
press nip 112 and the side vat segments 114, 116. The central vat segment 118
may be movable in a substantially vertical direction for providing additional
acces-
sibility to the region in proximity to the press nip 112. In Fig. 1, on the
left side of
the apparatus, the central vat segment 118 is shown in an inoperative opened
po-
sition, whereas on the right side of the apparatus, the central vat segment
118 is
shown in an operative closed position.
As mentioned above, a gap 124, 125 may be formed between the vat 114,
116, 118 and the outer surface 106, 108 of the drums 102, 104. In Fig. 1, only
the
right side of the apparatus illustrated the apparatus in a closed and
operating posi-
tion, and thus, only the gap 124 with regard to the second drum 104 and the
vat
116, 118 is shown, whereas the gap 125 with regard to the first drum 102 and
the
vat 114, 118 is not present in Fig. 1. However, a corresponding gap 125 with
re-
gard to the first drum 102 is illustrated by a broken line in Fig. 1. When the
left side
of the apparatus is in a corresponding closed and operating position, the gap
125
is provided between the first drum 102 and the vat 114, 118.
Said casing may comprise a first side casing member 115 which extends
between the ends of the first drum 102 and to which the first side vat segment
114
is mounted, and a second side casing member 117 which extends between the
ends of the second drum 104 and to which the second side vat segment 116 is
mounted. The side casing members 115, 117, together with their side vat seg-
ments 114, 116, may be pivotable about a pivot axis 121, 123, and movable be-
tween a closed position and an opened position for providing access to the
drums 102, 104. In Fig. 1, on the left side of the apparatus, the first side
casing
member 115 is in the opened position, whereby access to the drum 102 is pro-
vided, whereas on the right side of the apparatus, the second side casing
member
117 is in the closed position. Alternatively, only one of the side casing
members
could be movable, whereas the other could be stationary, or both side casing
members could be stationary. The movable side casing member could also be
movable in other ways than by pivoting about the respective pivot axis 121,
123.
Further, the casing may include a central casing member 140, in the form
of a stationary base unit 140 positioned substantially below the first and
second
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drums 102, 104, a stationary first end casing member 210 in the form of a
first ga-
ble, and a stationary second end casing member 212 in the form of a second ga-
ble (the end casing members 210, 212 being shown in Fig. 2). The drums 102,
104 may be pivotally mounted to the end casing members 210, 212, and thus be
rotatable in relation to the end casing members 210, 212. The central casing
mem-
ber 140 may be mounted to the end casing members 210, 212. Each side casing
member 115, 117 may be pivotally attached to the central casing member 140,
and each side casing member 115, 117 may also be connected to the central
casing member 140 via a respective hydraulic cylinder 178, 179 for controlling
the
movement of the respective side casing member 115, 117. The central vat seg-
ment 118 may be mounted to the central casing member 140.
Sealing means 404 (see Fig. 3) may be provided between each movable
side casing member 115, 117 and the central casing member 140, and between
each movable side casing member 115, 117 and the end casing members 210,
212. Further, axial sealing units 180, 182 may be mounted to each side casing
member 115, 117, each axial sealing unit 180, 182 extending along to the
longitu-
dinal extension of the respective drum 102, 104 and is adapted to abut the
outer
surface 106, 108 of the drum 102, 104 when the side casing member 115, 117 is
in its closed position. The sealing means and the axial sealing units 180, 182
are
adapted to seal off the gap 124, 125 from the external surroundings, i.e. the
at-
mosphere, at the position where the pulp is distributed to the gap 124, 125.
Each
axial sealing unit 180, 182 may be in the form of a scraper. Thus, by way of
the
above-mentioned sealing means and axial sealing units 180, 182, the gap 124,
125 and the surfaces defining the gap 124, 125 are sealed off from the atmos-
phere.
The apparatus may comprise a first pulp distribution device 126 for distrib-
uting pulp on the first drum 102 and a second pulp distribution device 128 for
dis-
tributing pulp on the second drum 104. Pulp to the distribution devices 126,
128
may be supplied in various ways known to the skilled person. The pulp
distribution
devices 126, 128 may be arranged to distribute pulp to the gap 124, 125 along
the
whole axial length of each drum 102, 104. The pulp distributed on the outer
sur-
face 106, 108 of the drum 102, 104 may form a mat on the drums 102, 104. From
the pulp distribution devices 126, 128 to the press nip 112, the pulp is fed
in the
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gap 124, 125 in the direction of rotation R1, R2 of the drums 102, 104 while
being
dewatered , or dewatered and washed.
Fig. 2 shows the central vat segment 118 in the apparatus as viewed from
above with the drums excluded. The apparatus may rest on the ground via four
legs 186, 187, 188, 189 (only two legs are shown in Fig. 1). In Fig. 2, the
end cas-
ing members 210, 212 of the casing are schematically shown.
The apparatus may also includes a pulp transport screw 152, which for
example can be in the form of a pulp disintegrating screw or a shredder screw,
towards which the pulp which has been pressed in the press nip 112 is
conveyed.
The pulp transport screw 152 may extend in an axial direction and may be ar-
ranged to disintegrate the pulp and transport the pulp axially away from the
press
for further processing. Each drum 102, 104 may be provided with a respective
doctor bar 154, 156, and each doctor bar 154, 156 may be provided at the
bottom
thereof with a respective doctor blade 158, 160 for scraping the outer surface
106,
108 of the respective drum 102, 104.
Fig. 3 schematically shows the first side casing member 115 of Fig. 1 pro-
vided with the sealing means 404 mentioned above. The surfaces 406, 408, 410,
412, 414 of the first side casing member 115 to be sealed against opposite sur-
faces are peripheral surfaces of the first side casing member 115, and the
sealing
means 404 may extend along the entire extension of the peripheral surfaces
406,
408, 410, 412, 414. The sealing means 404 may be adapted to seal between sur-
faces 406, 408, 410, 412, 414 provided on the first side casing member 115 and
surfaces opposite said surfaces 406, 408, 410, 412, 414 of the first side
casing
member 115. The surfaces 406 and 414 are adapted to be sealed against oppo-
site surfaces provided on the end casing members 210, 212 of the apparatus,
and
the surfaces 408, 410 and 412 are adapted to be sealed against opposite
surfaces
provided on the central casing member 140 of the apparatus. The second side
casing member may be provided with corresponding sealing means 404. How-
ever, a pulp dewatering apparatus provided with the sealing arrangement accord-
ing to the present invention may have a casing without movable side casing mem-
bers.
With reference to Figs. 4 to 9, aspects of the sealing arrangement 500 ac-
cording to the present invention are schematically illustrated. Fig. 4
schematically
shows a part of the inside of the first end casing member 210 as viewed from
the
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14
first drum 102, where the first end casing member 210 is provided with an em-
bodiment of the sealing arrangement 500 according to the present invention.
The
first drum 102 may be mounted to the first end casing member 210 by means of
bearings 502 and the first drum 102 is rotatable in relation to the sealing
arrange-
ment 500. In Fig. 5, a first end 503 of the first drum 102 is schematically
shown,
which may be provided with an end member 505 arranged to be journalled in the
bearings 502. At the first end 503, the first drum 102 may be provided with an
end
ring 504 which defines an end surface 506. The end surface 506 may be in the
form of an annular surface 506 surrounding the first axis of rotation 107, or
an an-
nular surface portion surrounding the first axis of rotation 107. The end
surface
506 may extend along the entire circumference of the first drum 102. The first
drum 102 may also be provided with the end surface 506 without the end ring
504.
The end surface 506 may be substantially perpendicular to the axis of rotation
107
of the first drum 102. The sealing arrangement 500 is arranged to seal between
the end surface 506 and the first end casing member 210. The sealing arrange-
ment 500 comprises a circumferentially extending sealing element 508 and a
sealing member 510. The sealing member 510 is provided in the region where
pulp is deposited onto the outer surface 106 of the first drum 102 by the
first pulp
distribution device 126. The sealing element 508 may extend along the
circumfer-
ential extension of the end surface 506 from the sealing member 510, along the
circumferential extension of the gap 125 for the first drum 102 and to the
press nip
112, or past the press nip to a region after the press nip 112. Thus, the
sealing
element 508 may be elongated in the circumferential direction C. The sealing
ar-
rangement 500 may comprise a circumferentially extending holder 512 arranged
to
hold the sealing element 508, and the holder 512 may comprise a
circumferentially
extending groove 514 which is at least partially engaged by the sealing
element
508. The holder 512 may comprise at least two circumferentially extending
walls
515, 517 defining the groove 514 (see Fig. 4). Each circumferentially
extending
wall 515, 517 could be divided into a plurality of units circumferentially
spaced
apart. First pressure means 516, e.g. biasing means, are provided for forcing,
e.g.
by pushing or biasing, the sealing member 510 in an axial direction A towards
the
first drum 102 to make the sealing member 510 bear against a portion of the
end
surface 506. The first pressure means 516 may comprise a compression spring
518. However, other pressure means are possible as previously mentioned above.
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The sealing member 510 may be in the form of a block and may be made of a
rigid
material, e.g. a polymer material. The sealing member 510 may be in the shape
of
a parallelepiped, e.g. a substantially rectangular parallelepiped or cuboid,
or even
a cube. The sealing element 508 may also be made of a polymer material, or any
5 other suitable material. The sealing arrangement 500 may comprise a guide
unit
520 arranged to hold and guide the sealing member 510. The guide unit 520 is
arranged to prevent a dislocation of the sealing member 510 in the direction
of ro-
tation R1 of the first drum 102. With reference to Fig. 9, the holder 512
holds sec-
ond pressure means 522 for forcing, e.g. by pushing, at least a first portion
524 of
10 the sealing element 508 in an axial direction A towards the first drum
102 to make
the first portion 524 bear against a portion of the end surface 506. In Fig.
9, the
sealing element 508 has been removed for illustrative purposes to show the sec-
ond pressure means 522. The first portion 524 may form the major portion of
the
sealing element 508. The second pressure means 522 may comprise a tube 526
15 adapted to be pressurized and inflatable by a fluid, e.g. gas, and may
extend along
the longitudinal extension of the sealing element 508 and may be positioned be-
tween the sealing element 508 and a bottom surface of the groove 514.
The sealing member 510 is arranged to withstand greater forces com-
pared to the sealing element 508. These greater forces may be caused by pulp,
which after the press nip 112 and after the scraping of the doctor blade 158,
still
remains on the drum 102 and in the region of the end ring 504 of the drum 102,
and thus re-enters the gap 125. These greater forces may also be caused by
pulp
moving in an axial direction A toward the end ring 504 after being deposited
on the
outer surface 106 of the first drum 102. Further, one end of the axial sealing
unit
180 may also be arranged to partially bear and seal against the sealing member
510, which also apply an axial force on the sealing member 510. Further, the
sealing member 510 is located in a region where the axial sealing unit 180,
the
sealing means 404 of the first side casing member 115 and the circumferential
sealing element 508 meet, which makes the region complex with regard to
sealing.
The sealing means 404 of the first side casing member 115 may bear against an
outward-curving surface 525 of the holder 512 and against a first side wall
527 of
the guide unit 520. The axial sealing unit 180 may axially bear against a
second
wall 529 of the guide unit 520 and axially against the sealing member 510.
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A terminal second portion 528 of the sealing element 508 is in proximity to
the sealing member 510 for sealing against the sealing member 510. The second
portion 528 of the sealing element 508 may be located circumferentially
outside of
the holder 512. The second portion 528 of the sealing element 508 may be
located
circumferentially outside of the groove 514 of the holder 512. The sealing ar-
rangement 500 may comprise locking means 530 for circumferentially, or tangen-
tially, locking the second portion 528 of the sealing element 508 to prevent a
movement or dislocation of the sealing element 508 and its second portion 528
in
the circumferential direction C. The locking means 530 may be arranged to
circumferentially lock the second portion 528 of the sealing element 508 to
the
guide unit 520. The locking means 530 may comprise complementary means en-
gaging one another, e.g. a recess 532 and a projection 534 engaging the recess
532. The guide unit 520 may be provided with the projection 534, and the
second
portion 528 of the sealing element 508 may be provided with the recess 532.
How-
ever, other locking means for preventing the dislocation of the sealing
element 508
and its second portion 528 in the circumferential direction C are possible.
The sealing member 510 and the second portion 528 of the sealing ele-
ment 508 comprise complementary guiding means 536 engaging one another.
The guiding means 536 may comprise a recess 538 and a projection 540 engag-
ing the recess 538. The recess 538 may have at least one wall 542 which forms
an angle with the axis of rotation 107 of the first drum 102. The projection
540 may
have at least one wall 544 which forms an angle with the axis of rotation 107
of the
first drum 102. The sealing member 510 may be provided with the recess 538,
and
the second portion 528 of the sealing element 508 may be provided with the pro-
jection 540, or vice versa. Other designs of the complementary guiding means
may also be possible. The sealing arrangement 500 comprises means 545 for
forcing the second portion 528 of the sealing element 508 in a direction
towards
the first drum 102 to make the second portion 528 bear against a portion of
the
end surface 506 (see Fig. 8). The means 545 for forcing the second portion 528
of
the sealing element 508 in a direction towards the first drum 102 may comprise
the
first pressure means 516. The first pressure means 516 are arranged to force,
by
pushing, e.g. biasing, the second portion 528 of the sealing element 508 in an
ax-
ial direction A towards the first drum 102 to make the second portion 528 bear
against a portion of the end surface 506. The guiding means 536 are arranged
to
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17
guide the second portion 528 of the sealing element 508 in the axial direction
A
towards the first drum 102. The means 545 for forcing the second portion 528
of
the sealing element 508 in a direction towards the first drum 102 to make the
sec-
ond portion bear against a portion of the end surface 506 may be located
outside
the groove 514 of the holder 512, and may be separate from the second pressure
means 522.
When the end surface 506 is in the form of an annular surface 506 sur-
rounding the first axis of rotation 107, as illustrated in Fig. 5, or in the
form of an
annular surface portion surrounding the first axis of rotation 107, each of
the seal-
ing member 510 and the sealing element 508 is consequently arranged to bear
against a portion of the annular surface 506 surrounding the axis of rotation
107 or
a portion of the annular surface portion surrounding the axis of rotation.
In Figs. 4 and 6, only half of the end casing member 210 is illustrated. It is
to be understood that the other half of the end casing member 210, which is lo-
cated on the other side of the symmetry plane 101, may be provided with a cor-
responding sealing arrangement 500 for the first end of the second drum 104.
It is
to be understood that the apparatus shown in Fig. 1 may be provided with one
sealing arrangement 500 for each end of the respective drum 102, 104. Thus,
the
apparatus may be provided with four sealing arrangements 500, each end casing
member 210, 212 holding two sealing arrangements 500.
To further illustrate the drawbacks overcome by the sealing arrangement
500 according to the present invention, a prior art sealing arrangement 700
for
sealing between an end of a rotatable drum, or roll, and a stationary end
casing
member is now illustrated with reference to Figs. 10-11. The prior art sealing
ar-
rangement 700 shown comprises a guide unit 720, first pressure means 716, a
holder 712, second pressure means 722, locking means 730 and a first portion
724 of a sealing element 708 which may correspond to the corresponding
features
shown in Figs. 4-9. However, in the prior art sealing arrangement 700, the
terminal
second portion 728 of the sealing element 708, which is in proximity to the
sealing
member 710, is not supported by any means for forcing the second portion 728
of
the sealing element 708 to make the second portion 728 bear against a portion
of
the end surface 506. The pressurized tube 726 of the second pressure means 722
which is held by the groove 714 the holder 712 has a sealed end adjacent to
the
second portion 728 of the sealing element 708, and the sealed end cannot be in-
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18
flated. Consequently, the pressurized tube 726 cannot apply a sufficient axial
force
on the second portion 728 of the sealing element 708 in the direction toward
the
first drum, and the second portion 728 of the sealing element 708 does not
bear,
or does not sufficiently bear, against the end surface. As a result of this,
pulp lo-
cated in the region of the sealing member 710 and the sealing element 708 may
easily force the second portion 728 of the sealing element 708 away from the
end
surface 506 and may be wedged or jammed between the sealing element 708 and
the end surface 506 when the drum rotates. The jammed pulp may result in leak-
age of pulp suspension and/or filtrate, as media may pass between the sealing
element 708 and the end surface 506. The jammed pulp may also dislocate the
sealing member 710, which also may result in leakage of pulp suspension and/or
filtrate. The jammed pulp may also result in increased wear on the rotatable
drum,
e.g. the end ring of the drum, and on the sealing member 710 and sealing
element
708. Leakage of pulp suspension and/or filtrate and wear on the seals and on
the
drum impair the processing of pulp in the dewatering apparatus. Further, if
the
sealing function is impaired, the pressure within the sealed-off gap or space
may
not be maintained which impairs/deteriorates the dewatering efficiency.
By the sealing arrangement 500 according to the present invention, the
second portion 528 of the sealing element 508 is sufficiently forced in an
axial di-
rection A toward the end surface 506 to make the second portion 528 of the
seal-
ing element 508 sufficiently bear against the end surface 506. Consequently,
no
pulp, or only a reduced amount of pulp, is allowed to enter between the end
sur-
face and the second portion 528 of the sealing element 508 and no pulp is
jammed therebetween, or the amount of jammed pulp is radically reduced. Thus,
leakage of pulp suspension and/or filtrate and wear on the rotatable drum 102
and
on the sealing element 508 and sealing member 510 are efficiently avoided by
means of the sealing arrangement 500 according to the present invention.
The invention shall not be considered limited to the embodiments illus-
trated, but can be modified and altered in many ways by one skilled in the
art,
without departing from the scope of the appended claims.
