Note: Descriptions are shown in the official language in which they were submitted.
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CA 02247920 1998-08-31
COMBINATION SAVEALL AND BLOWBOX SYSTEM
AND ASSOCIATED METHOD
Bac round of the Invention
This invention relates generally to papermachines
used in the making of paper and relates, more particularly,
to the means and methods for preventing separation of a web
of paper from a carrier fabric following the passage of the
carrier fabric and web around the surface of a cylindrical
roll, such as a pick-up roll, of a papermachine.
It is known that a blowbox can be utilized to reduce
the likelihood of separation of a running web of paper from
a carrier fabric as the carrier fabric and web move off of the
surface of a pick-up roll. In this regard, a blowbox can be
positioned adjacent the off-running side of the pick-up roll
for directing air from a source generally away from the
surface of the carrier fabric on the side thereof opposite the
running web to create a vacuum zone on the fabric-side of the
fabric and web arrangement. The resulting difference in air
pressure between the web side and the fabric side of the
2o fabric and web arrangement biases the web against the carrier
fabric and helps to prevent separation of the web and fabric
from one another as the carrier fabric and web are moved past
this vacuum zone . Examples of blowboxes used for altering the
air pressure adjacent selected regions of a carrier fabric and
running web moving through a papermachine are shown and
described in U.S. Patents 4,516,330, 4,628,618 and 4,551,203.
Commonly, the air which is directed out of a blowbox
for the purpose of creating a vacuum zone at a selected region
is discharged from the environment of the papermachine before
additional benefits are obtained from the air. It would be
desirable to obtain additional work from the air which is
directed out of a blowbox before the air is discharged from
the papermachine environment.
Accordingly, it is an object of the present
invention to provide a new and improved means for obtaining
additional benefits from the air which is directed from a
blowbox and an associated method.
Another object of the present invention to provide
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such a means which utilizes air which is directed out of a
blowbox for conditioning the surface of a pick-up roll
following the passage therearound of a carrier fabric and web.
Still another object of the present invention is to
provide such a means which utilizes air which is directed out
of a blowbox for removing water from the surface of a pick-up
roll following the passage therearound of a carrier web and
web by dislodging water droplets and other contaminants from
the surface of the pick-up roll.
A further object of the present invention is to
provide such means which collects water droplets and other
contaminants which are dislodged from the surface of the pick-
up roll for disposal.
A still further object of the present invention is
to provide such means which is uncomplicated in construction,
yet effective in operation.
summary of the Invention
T his--~nventi6~- asides -ire ~--sy~te~cr-~-~d--methed--for
use on the off-running side of a pick-up roll of a
papermachine around which a carrier fabric and paper web are
moved wherein the carrier fabric is disposed between the web
and the surface of the pick-up roll.
The system of the invention includes a blowbox
section positionable adjacent the pick-up roll on the off
running side thereof for directing air from a source away from
the surface of the carrier fabric opposite the web to reduce
the likelihood of separation of the web from the carrier
fabric. The means for directing air from the source also
directs at least a portion of the air generally around the
surface of the pick-up roll so that water droplets and other
contaminants which cling to the surface of the pick-up roll
following the movement of the carrier fabric and web off of
the off-running side of the roll are dislodged from the
surface of the roll by the directed air portion. The system
also includes a saveall section associated with the blowbox
section including means for collecting the water droplets and
other contaminants which are dislodged from the surface of the
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pick-up roll by the directed air portion.
The method of the invention includes the steps
involved in using the aforedescribed system of the invention.
In particular, a vacuum zone is created adjacent the surface
of the carrier fabric on the side thereof opposite the web and
adjacent the off-running side of the pick-up roll by directing
air generally away from the surface the carrier fabric, and
then utilizing at least a portion of the air which is directed
generally away from the surface of the carrier fabric to
dislodge water droplets and other contaminants from the
surface of the pick-up roll. The droplets and contaminants
which are dislodged from the surface of the pick-up roll by
the utilized portion of the air are subsequently collected for
disposal.
grief Description of the Drawinc~s_
Fig. 1 is a schematic side view of a fragment of a
pick-up section of a paper machine within which an embodiment
of a combination blowbox/saveall system is incorporated.
Fig. 2 is a view similar to that of Fig. 1 of the
Fig. 1 fragment, but drawn to a slightly larger scale.
Detailed Description of an Illustrative Embodiment
Turning now to the drawings in greater detail , there
is shown in Fig. 1 an environment within which an embodiment,
generally indicated 20, of a combination blowbox/saveall
system is utilized. More specifically, the depicted
environment includes a pick-up section of a papermachine 18
having a cylindrical pick-up roll 22 mounted for rotation
about an axis 24 (e.g. for counterclockwise rotation about the
axis 24 as viewed in Fig. 1) and further includes a carrier
fabric 26 and a running web 28 which are moved into engagement
with one another and around the roll 22 in the direction of
the arrow 36 during the rotation of the roll 22. The pick-up
roll 22 has a peripheral surface 30 comprised, for example,
of stainless steel, and which may (or may not) be perforated
and employ vacuum or vacuum-enhanced sections to help transfer
the web 28 to the fabric 26. By comparison, the carrier
fabric 26 is comprised of a soft, air-permeable material, such
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as felt, which is adapted to engage the web 28 as the web 28
is guided around the roll surface 30. In the illustrated
fragment of the depicted paper machine 18, the fabric 26 is
disposed between the web 28 and the roll surface 30 as the
fabric and web are moved together onto and then off of the
roll surface 30.
The side, indicated 34, of the pick-up roll 22 off
of which the web 28 and fabric 26 are moved is referred to
herein as the "off-running side" of the roll 22 to
differentiate this side of the roll 22 from the side thereof
onto which the web 28 and fabric 26 are moved. The region of
airspace provided between the roll surface 30 and the carrier
fabric 26 on the off-running side of the roll 22 is commonly
referred to as a nip 32, and as will be apparent herein, the
combination blowbox/saveall system 20 is disposed adjacent
this nip 32 for the dual purpose of preventing separation of
the web 28 from the fabric 26 as the web and fabric are moved
off of the roll surface 30 and for collecting water droplets
and other contaminants which are dislodged from the surface
30 of the roll 22 ( in a manner described herein) following the
movement of the fabric 26 and web 28 off of the roll surface
30.
With reference still to Fig. 1, the system 20
includes a blowbox section 40 situated adjacent the off
running side of the roll 22 and disposed adjacent the carrier
fabric 26 on the side thereof opposite. the web 28. As best
shown in Fig. 2, the blowbox section 40 includes a series of
walls 42, 44, 46 which are joined together to provide an
interior 48 for the blowbox section 40 and also includes a
partition 50 which separates the blowbox interior 48 from the
fabric 26. Each of the walls and partition 50 of the blowbox
section 40 are constructed, for example, of appropriately-
shaped sheet metal, and the interior 48 is sized to span
substantially the entire width of the fabric 26. The
partition 50 of the blowbox section 40 is arranged generally
parallel to the surface of the fabric 26 for an appreciable
distance therearound so a narrow air space 52 (best shown in
CA 02247920 1998-08-31
Fig. 2 ) is provided between the partition 50 and the upper
surface of the fabric 26. Nozzles 54 and 56 are disposed at
the opposite (longitudinal) ends of the blowbox interior 48
for receiving pressurized air from an air supply (e.g. a high-
s pressure industrial fan) and for discharging the air through
elongated slots formed along the length of the nozzles 54 or
56. A pair of nip plates 57 (only one shown in phantom in
Fig. 2) are mounted upon the blowbox section 40 at the
opposite ends of the pick-up roll 22 to separate and seal the
nip 32 from the regions of airspace situated outboard of the
roll 22.
The operating principles of the blowbox section 40
are well known so that a detailed description of such
principles are not believed to be necessary. Suffice it to
say that as streams of air are discharged from the nozzles 54
and 56 in directions generally away from the upper surface of
the fabric 26 , a vacuum zone ( i . a . a region of sub-atmospheric
pressure j - -is - cz=e-abed-- within- the -air--space- -52-. ~'he- resulting
difference in air pressure which exists between the air space
52 and the air space disposed on the side of the web 28
opposite the fabric 26 (i.e. between the air space regions
defined above and below the fabric 26 and web 28 as shown in
Fig. 2) biases the web 28 upwardly against the downwardly-
facing surface of the fabric 26 and thereby helps to prevent
a separation between the web 28 and the fabric 26 as the web
and fabric move off of the roll surface 30. Thus, the blowbox
section 40 of the system 20 reduces the likelihood that the
web 28 will separate from the carrier fabric 26 as the web 28
and fabric 26 move off of the roll surface 30, and the blowbox
section 40 is advantageous in this respect.
In the depicted environment, the fabric 26 and web
28 move for a relatively lengthy distance from the moment that
they move past the blowbox section 4o until they move onto the
surface of a subsequent roll (not shown) located, for example,
in a press section. To prevent separation of the fabric 26
and web 28 during this lengthy run downstream of the blowbox
section 40, one or more additional blowboxes 58 (only one
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shown in Figs . 1 and 2 ) can be positioned adjacent the surface
of the fabric 26 at a location situated downstream of the
blowbox section 40. It will be understood, however, that
these additional blowboxes 58 are optional and probably would
not be needed if the run of the fabric 26 and web 28 which
extends between two adjacent rolls was relatively short.
With reference still to Fig. 2, the system 20 also
includes a saveall section 60 which is joined to the blowbox
section 40 in a single device. The saveall section 60
includes an open receptacle 68 which is positioned in such a
relation to the pick-up roll 22 so as to open generally toward
the surface 30 of the roll 22. To this end, the receptacle
' 68 depicted in Fig. 2 is provided by top and back walls 66 and
64, respectively, and shares a wall 44 with the blowbox
section 40 wherein this shared wall 44 provides a bottom for
the receptacle 68. As best shown in Fig. 2, the receptacle
68 of the saveall section 60 extends for a substantial
distance around the periphery of the roll surface 30.
Since the fabric 26 and web 28 are both relatively
wet as they move in concert through a substantial portion of
the pick-up section of the papermachine 18 , it is not uncommon
that the surface 30 of the roll 22 will become wet with water
in the form of droplets 72 (Fig. 2) or other contaminants from
the fabric 26 and web 28 as the fabric 26 and web 28 move
around a portion of the roll surface 30. Furthermore, in the
instance in which the roll surface is perforated, these water
droplets and contaminants can cover the openings of the
perforations and become detrimental to the operation of an
attending vacuum-enhanced section of the roll. As will be
explained herein, these water droplets 72 and contaminants are
dislodged from the surface 30 of the roll 22 and are collected
within the receptacle 68 of the saveall section 60.
Associated with the receptacle 68 is a drain 70 which
accommodates the evacuation and disposal of water and
contaminants which have been collected within the receptacle
68.
It is a feature of the system 20 that at least a
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portion of the air which is used by the blowbox section 40 for
the purpose of creating a vacuum zone within the air space 52
is also used to dislodge water droplets 72 and contaminants
from the surface 30 of the roll 22. To this end, the wall 42
of the blowbox section 40 of the system 20 includes a
partition surface 74 which is disposed generally parallel to
the surface 30 of the roll 22 for an appreciable distance
along the off-running side 34 of the roll 22. This partition
surface 74 provides, along with the adjacent fragment of the
surface 30 of the roll 22, an air channel 76 through which air
is conducted along the roll surface 30 as it leaves the
blowbox section nozzle 54. It will be understood that air is
directed through the channel 76 substantially tangentially
around the roll surface 30 in a direction which corresponds
with the direction of movement of the pick-up roll 22 past the
channel 76. It will also be understood, however, that the
velocity of the air which exits the nozzle 54 is much greater
than the velocity of the surface 30 of the roll 22 past the
channel 76 (and preferably is at least about one and one half
times greater than the speed of the roll surface). In
addition, an exhaust 78 can be provided in one wall 66 of the
saveall section 60 through which air is permitted to escape
therefrom.
As the high-velocity air is forced through the
channel 76 by the blowbox nozzle 54, the air moves along the
surface 30 of the roll 22 in a manner which sweeps and scrubs
the roll surface 30 and strips (thereby dislodging) water
droplets and other contaminants from the surface 30. The
water droplets 72 and contaminants which are dislodged from
the roll surface 30 exit the channel 76 with the air, yet are
confined within the cavity encompassed by the walls 44, 64,
66 of the receptacle 68 so as to be prevented from being blown
back or fall back onto the surfaces of the web 28 and fabric
26 situated downstream of the off-running side 34 of the roll
22'. Instead, the dislodged droplets and contaminants are
collected within the receptacle 68 of the saveall section 60
and are permitted to migrate gravitationally to the bottom of
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the receptacle 68 for removal through the drain 70.
Exemplary dimensions of the illustrated combination
saveall/blowbox system 20 for use adjacent a pick-up roll 22
having a diameter of about three feet, eleven inches are
provided here as follows: The entrance to the channel 76 is
spaced about four inches from the upper surface of the fabric
26; the length of the channel 76 as measured between its
entrance and exit is about six inchest and the receptacle 68
of the saveall section 60 extends around about one-fourth of
the circumference of the pick-up roll 22.
It follows from the foregoing that a combination
blowbox/saveall system 20 has been described which serves the
dual function of reducing the likelihood of separation of the
web 28 from its carrier fabric 26 downstream of the off-
running side 34 of a pick-up roll 22 and for dislodging water
droplets and contaminants from the surface 30 of the roll 22
for collection and disposal following the passage therearound
of the fabric 26 and web 28. Moreover, a method has been
described which utilizes a portion of the stream of air used
for preventing the separation of a web 28 from a carrier
fabric 26 following the movement of the carrier fabric and web
around the surface of the pick-up roll 22 for dislodging water
droplets and other contaminants which cling to the surface 30
of the pick-up roll 22 following the movement therearound of
the carrier fabric 26 and web 28. By utilizing the blowbox-
generated air to scrub and thereby dislodge water droplets and
contaminants from the surface of the pick-up roll 22,
additional benefits are obtained from the blowbox-generated
air before the air is discharged from the papermachine
environment.
It will be understood that numerous modifications
and substitutions can be had to the aforedescribed embodiment
without departing from the spirit of the invention. For
example, although the aforedescribed system 20 has been shown
and described as including a blowbox section 40 and a saveall
section 60 which share at least one common wall, the blowbox
and saveall sections of a system in accordance with the
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broader aspects of the present invention may not share any
common walls. As a practical matter, however, in order fcr
the saveall section to collect water and contaminants which
have been dislodged by the blowbox-generated air, the saveall
section and the blowbox section are likely to be situated
relatively close to one another. Still further, although the
aforedescribed system 20 has been shown and described as
including a saveall section 60 which is disposed generally
above the blowbox section 40 , the saveall and blowbox sections
of an alternative system can possess an alternative
disposition.
Further still, although the aforedescribed system
has been described for use in conjunction with a roll 22
of a pick-up section of a papermachine, a system in accordance
15 with the present invention can be utilized downstream of other
rolls of a papermachine, such as those situated within the
press section of a papermachine. Along these lines, it is
believed that a system in accordance with the present
invention can be advantageously employed downstream of a roll
20 wherein the run of the fabric and web between adjacent rolls
is long enough that separation of the web and fabric from one
another is likely and wherein the percentage of water within
the paper web is within the range of about sixty to eighty-
five percent so that the surface of the roll is wetted
appreciably by the passage of the fabric and web therearound.
Accordingly, the aforedescribed embodiment is
intended for the purpose of illustration and not as
limitation.
