U.S. patent application number 10/282974 was filed with the patent office on 2003-05-22 for device for cleaning a screen in a papermaking plant.
Invention is credited to Bartelmuss, Heinz, Bartelmuss, Klaus.
Application Number | 20030094255 10/282974 |
Document ID | / |
Family ID | 3689083 |
Filed Date | 2003-05-22 |
United States Patent
Application |
20030094255 |
Kind Code |
A1 |
Bartelmuss, Klaus ; et
al. |
May 22, 2003 |
Device for cleaning a screen in a papermaking plant
Abstract
A device for cleaning the at least one screen in a papermaking
plant enables cleaning of the screen that is guided over rollers.
The cleaning device has at least one vacuum chamber which bears
against the screen. At least one spray nozzle is arranged in the
vacuum chamber to transport a cleaning liquid, in particular water,
to the screen. The at least one vacuum chamber is arranged radially
outside one of the rollers and the screen, in the area of the
vacuum chamber, bears on the roller at least over a major part of
its length.
Inventors: |
Bartelmuss, Klaus;
(Teufenbach, AT) ; Bartelmuss, Heinz; (Teufenbach,
AT) |
Correspondence
Address: |
LERNER AND GREENBERG, P.A.
Post Office Box 2480
Hollywood
FL
33022-2480
US
|
Family ID: |
3689083 |
Appl. No.: |
10/282974 |
Filed: |
October 29, 2002 |
Current U.S.
Class: |
162/275 ;
162/279 |
Current CPC
Class: |
D21F 1/32 20130101; D21F
1/34 20130101 |
Class at
Publication: |
162/275 ;
162/279 |
International
Class: |
D21F 001/32 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 22, 2001 |
AU |
1835/2001 |
Claims
We claim:
1. In a papermaking plant having at least one screen guided over a
plurality of rollers, a device for cleaning the screen, comprising:
a vacuum device adjoining the screen; at least one spray nozzle
disposed in said vacuum device and configured to apply a cleaning
liquid to the screen; wherein said vacuum device is disposed
radially outside one of the rollers, and the screen bears on the
one roller in an area of said vacuum chamber at least over a major
portion of a length thereof.
2. The device according to claim 1, wherein said vacuum device
comprises at least one vacuum chamber bearing against the
screen.
3. The device according to claim 1, wherein the cleaning fluid is
water and said spray nozzle is one of a plurality of spray nozzles
configured to spray the water onto the screen.
4. The device according to claim 2, which comprises a plurality of
sealing strips aligned transversely with respect to a direction of
movement of the screen and disposed to seal said at least one
vacuum chamber with respect to the screen guided over the one
roller.
5. The device according to claim 2, wherein the screen in an area
of said vacuum chamber bears on the one roller over an entire
length of said vacuum chamber.
6. The device according to claim 2, wherein said spray nozzle is
adjustable in terms of an angle of a jet direction in said vacuum
chamber in the direction of movement of the screen.
7. The device according to claim 6, which comprises a spray pipe
supporting and communicating with said at least one spray
nozzle.
8. The device according to claim 1, wherein said vacuum device
comprises at least one first vacuum chamber and at least one second
vacuum chamber radially outside the one roller, and wherein said
second vacuum chamber is disposed, in the direction of movement of
the screen, next to said first vacuum chamber.
9. The device according to claim 8, wherein the screen, in an area
of said first vacuum chamber, bears on the one roller over an
entire length of said first vacuum chamber, and wherein an area of
the screen within an effective area of said at least one second
vacuum chamber bears on the roller over part of a length thereof,
and is lifted off the roller over a further part of the length
thereof.
10. The device according to claim 8, which comprises an extraction
duct commonly connecting said at least one first vacuum chamber and
said at least one second vacuum chamber to a common vacuum
source.
11. The device according to claim 10, which further comprises
control devices arranged between said at least one first vacuum
chamber and said at least one second vacuum chamber and said vacuum
source.
12. The device according to claim 11, wherein said control devices
include flaps, pivotally disposed about respective axes aligned
approximately at right angles.
13. The device according to claim 2, wherein at least a part of
said vacuum chamber is formed with a cross section increasing in
size transversely to the direction of movement of the screen.
14. The device according to claim 8, wherein at least a part of
said first vacuum chamber is formed with a cross section increasing
in size transversely to the direction of movement of the
screen.
15. The device according to claim 14, wherein said at least one
second vacuum chamber is formed with a height increasing in size
transversely to the direction of movement of the screen.
16. The device according to claim 8, wherein said vacuum chambers
are formed with edges, and a plurality of sealing strips are
aligned transversely with respect to the direction of movement of
the screen and disposed to seal at least some of said edges of said
vacuum chambers against the screen.
17. The device according to claim 16, wherein, on sides associated
with sidewall edges of said vacuum chambers, said sealing strips
are formed with profiled grooves, by way of which said sealing
strips are pushed onto the sidewall edges of said vacuum
chambers.
18. The device according to claim 17, wherein said profiled grooves
are T-shaped.
19. The device according to claim 16, wherein at least some of said
sealing strips are asymmetrical strips.
20. The device according to claim 1, which comprises a spray pipe
supporting and communicating with said at least one spray nozzle,
and said at least one spray nozzle includes needle-jet nozzles and
flat-jet nozzles.
21. A papermaking plant, comprising: at least one screen for
forming a web from fiber pulp; a plurality of guide rollers guiding
said at least one screen, said guide rollers including a given
deflection roller; and a cleaning device for cleaning said screen,
sead cleaning device including at least one vacuum chamber and at
least one spray nozzle disposed in said vacuum chamber and
configured to spray a cleaning liquid onto said screen; said vacuum
chamber being disposed radially outside said given deflection
roller, and said screen bearing on said given deflection roller in
a vicinity of said vacuum chamber at least over a major portion of
a length thereof.
Description
BACKGROUND OF THE INVENTION
[0001] Field of the Invention
[0002] The present invention lies in the papermaking field. More
specifically, the invention relates to a device for cleaning the at
least one screen in a papermaking plant, wherein the screen is
guided over rollers, comprising at least one vacuum chamber which
bears against the screen and at least one spray nozzle arranged in
the vacuum chamber, through which a cleaning liquid, in particular
water, can be applied to the screen.
[0003] In plants for producing paper, a fibrous suspension is
applied to an intrinsically closed screen (also referred to as a
wire, or a forming fabric) that is guided over rollers. Plants are
also known wherein two screens are provided, between which the
paper web is produced. In all the plants there is the requirement
for the at least one screen, in an area wherein it is lifted off
the paper web and led back to the start of the plant, to be cleaned
from components remaining in and on it, in particular pulp fibers,
and to be dried.
[0004] U.S. Pat. No. 6,099,691 to Clarke et al. discloses a device
for cleaning the screen (referred to as a forming fabric) of a
papermaking plant. There, the device comprises four vacuum
chambers, of which in each case two are arranged on both sides of a
screen and wherein there are spray nozzles, through which water is
sprayed onto both surfaces of the screen, as a result of which the
latter is cleaned. The water applied through the spray nozzles is
fed from the vacuum chambers to a separator. In addition, the
screen is acted on by air in one of the vacuum chambers in order to
dry it.
[0005] Such prior art devices for cleaning a screen are, however,
afflicted by a number of disadvantages:
[0006] Since vacuum chambers are provided on both sides of the
screen, a very great amount of space is necessitated by this
device. Since the screen is led through between at least two vacuum
chambers, coming into contact with the edges of their entry and
exit slots, there is additionally the risk that it will be damaged
by the movement over these edges. In addition, there is the
requirement to connect the vacuum chambers arranged on both sides
of the screen to separate vacuum sources and, in addition, to
assign water separators in each case to these. Furthermore, the
water applied to the screen by the spray nozzles passes through the
screen, carrying the contaminates with it. However, since the
predominant proportion of the contaminants is located on that side
of the screen on which the paper web rests, this necessitates the
water applied to this side of the screen carrying the contaminants
through the screen into the vacuum chamber arranged on the other
side of the screen. As a result, this cleaning device has a very
poor efficiency and/or is relatively expensive in operation.
SUMMARY OF THE INVENTION
[0007] It is accordingly an object of the invention to provide a
device for cleaning a screen in a papermaking plant which overcomes
the above-mentioned disadvantages of the heretofore-known devices
and methods of this general type.
[0008] With the foregoing and other objects in view there is
provided, in accordance with the invention, a cleaning device for
cleaning the at least one screen in a papermaking plant, wherein
the at least one screen is guided over a plurality of rollers. The
device for cleaning the screen comprises:
[0009] a vacuum device adjoining the screen;
[0010] at least one spray nozzle disposed in the vacuum device and
configured to apply a cleaning liquid (e.g., water) to the
screen;
[0011] wherein the vacuum device is disposed radially outside one
of the rollers, and the screen bears on the one roller in an area
of the vacuum chamber at least over a major portion of a length
thereof.
[0012] According to the invention, this is achieved in that the at
least one vacuum chamber is arranged radially outside one of the
rollers, over which the screen is led back to the start of the
plant, the screen in the effective area of the vacuum chamber
bearing on this roller at least over a major part of its
length.
[0013] Therefore, at least one vacuum chamber is provided only on
that side of the screen on which the paper web has come to rest and
on which the major part of the contaminants is found. By means of
the at least one spray nozzle located in this vacuum chamber, the
cleaning liquid is sprayed onto the screen resting on the roller,
and emerges from the screen again on this side, carrying the
contaminants with it. By reducing the number of vacuum chambers
provided and the vacuum sources associated with the latter, a
decisive constructional simplification is achieved, although the
effectiveness of the cleaning is increased. In addition, the
operating costs are decisively reduced by this means. Since, in
addition, the screen is led over a roller in the area of the at
least one vacuum chamber, its movement path is defined, as a result
of which the side edges of the vacuum chambers are at a defined
distance with respect to that side of the screen on which the paper
web comes to rest. By this means, any damage to the screen
resulting from the edges of the entry and exit openings of the at
least one vacuum chamber is ruled out.
[0014] The at least one vacuum chamber is preferably sealed off
with respect to the screen led over the roller by means of sealing
strips aligned transversely with respect to the direction of
movement of the screen. Furthermore, the screen in the area of the
first vacuum chamber preferably bears on the roller over the length
of this vacuum chamber. In addition, the angle of the jet direction
of the at least one spray nozzle arranged on a spray pipe in the
first vacuum chamber is preferably adjustable in the direction of
movement of the screen.
[0015] According to a preferred embodiment, at least one second
vacuum chamber is provided radially outside the roller in the
direction of movement of the screen, in addition to the at least
one vacuum chamber. In this case, the screen in the area of the
first vacuum chamber can bear on the roller over its entire length,
and the area of the screen in the effective area of the at least
one second vacuum chamber can bear on the roller over part of its
length and be lifted off the roller over a further part of its
length.
[0016] The at least one first vacuum chamber and the at least one
second vacuum chamber are preferably connected to a common vacuum
source via an extraction duct, and, furthermore, control devices
are arranged between the at least one first vacuum chamber and the
at least one second vacuum chamber and the vacuum source and, for
example, are formed as flaps which can be pivoted about axes
aligned approximately at right angles, and at least part of the at
least one second vacuum chamber is formed with a cross section
which increases in size transversely with respect to the direction
of movement of the screen. The at least one second vacuum chamber
is preferably formed with a height which increases in size
transversely with respect to the direction of movement of the
screen, at least some of the edges of the walls of the vacuum
chambers, assigned to the screen and aligned transversely with
respect to the direction of movement of the latter, are sealed off
with respect to the screen by means of sealing strips, on their
sides associated with the edges of the walls of the vacuum
chambers, the sealing strips are formed with preferably T-shaped
profiled grooves, by means of which they are pushed onto the edges
of the sidewalls of the vacuum chambers, and at least some of the
sealing strips are asymmetrical.
[0017] Finally, the spray pipe is preferably formed with needle-jet
nozzles and with flat-jet nozzles.
[0018] In further summary, and with the above and other objects in
view there is also provided, in accordance with the invention, a
papermaking plant, comprising:
[0019] at least one screen for forming a web from fiber pulp;
[0020] a plurality of guide rollers guiding the at least one
screen, the guide rollers including a given deflection roller;
and
[0021] a cleaning device for cleaning the screen, sead cleaning
device including at least one vacuum chamber and at least one spray
nozzle disposed in the vacuum chamber and configured to spray a
cleaning liquid onto the screen;
[0022] the vacuum chamber being disposed radially outside the given
deflection roller, and the screen bearing on the given deflection
roller in a vicinity of the vacuum chamber at least over a major
portion of a length thereof.
[0023] Other features which are considered as characteristic for
the invention are set forth in the appended claims.
[0024] Although the invention is illustrated and described herein
as embodied in a device for cleaning the at least one screen in a
papermaking plant, it is nevertheless not intended to be limited to
the details shown, since various modifications and structural
changes may be made therein without departing from the spirit of
the invention and within the scope and range of equivalents of the
claims.
[0025] The construction and method of operation of the invention,
however, together with additional objects and advantages thereof
will be best understood from the following description of specific
embodiments when read in connection with the accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0026] FIG. 1 is a schematic illustration of a papermaking
plant;
[0027] FIG. 2 is a vertical section, taken along a direction of
movement of the screen, through a device according to the
invention;
[0028] FIG. 3 is a section taken along the line III-III in FIG. 2
showing the device;
[0029] FIG. 4 is a section of the device taken along the line IV-IV
in FIG. 2 and illustrated on a scale that is reduced with respect
to FIG. 2;
[0030] FIG. 5 is a magnified view of the detail A diagrammatically
indicated in FIG. 2;
[0031] FIG. 6 is a magnified-view of the detail B diagrammatically
indicated in FIG. 2;
[0032] FIG. 6A is the detail B in a design variant of the
invention; and
[0033] FIG. 7 is a side view of a component of the device;
[0034] FIG. 7A is a plan view thereof; and
[0035] FIG. 7B is a sectional end view of the component.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0036] Referring now to the figures of the drawing in detail and
first, particularly, to FIG. 1 thereof, there is shown a plant
according to the invention for producing paper. The plant is
illustrated with a first screen 1 and a second screen 2. These two
screens 1 and 2, which are intrinsically closed (i.e., they are
endless belt screens) are moved over a plurality of guide and
deflection rollers 11 and 21 associated with them at the same speed
of, for example, about 40 m/sec, being led on each other in the
area of the rollers 11a and 21a and separately from each other in
the area of the rollers 11b and 21b. In the region wherein the two
screens 1 and 2 are moved resting on each other, there is provided
a spray nozzle 3. Furthermore, a plurality of suction boxes 4 are
provided on both sides of the screens 1 and 2. In addition, a
further spray nozzle 3a and a suction box 4a are arranged in the
further course of the first screen 1. Finally, cleaning device for
the two screens 1 and 2 are arranged in the area of the guide
rollers 11c and 21c.
[0037] Additional cleaning devices of this kind may be assigned to
the first screen and the second screen 2.
[0038] During the operation of the papermaking plant 1, in the area
of the two rollers 11a and 21a, the pulp prepared for the
production of a paper web is introduced uniformly over the width of
the two screens 1 and 2 in the direction of the arrow C between the
two screens 1 and 2. By means of the suction boxes 4 that are
provided along the two screens 1 and 2, the liquid contained in the
pulp is extracted, as a result of which a paper web 6 is formed
which, after the second screen 2 has been lifted off the first
screen 1, remains on the latter, being dried further by the further
suction box 4a. Finally, in the area of a deflection roller 16, it
is lifted off the first screen 1 and fed to further processing.
[0039] The spray nozzles 3 and 3a are used to wet the screens 1 and
2 when no pulp is resting on them.
[0040] Since the two screens 1 and 2 have to be cleaned of
cellulose fibers and the like adhering to them, the cleaning
devices 5 are provided in their further movement paths, and are
explained as follows:
[0041] As can be seen from FIG. 2, radially outside the guide
roller l1c and at that point of the screen 1 on which the paper web
6 is laid, there are two vacuum chambers 51 and 52 following one
after the other in the direction of movement of the screen 1, whose
suction openings are sealed off with respect to the screen 1 by
means of sealing strips 53, 54 and 55. Inside the first vacuum
chamber 51 there is a spray pipe 56 constructed with nozzles 57,
via which water can be sprayed onto the associated side of the
screen 1. Furthermore, control flaps 62 and 63 are assigned to the
vacuum chambers 51 and 52.
[0042] As can further be seen from FIG. 3, a common suction duct 61
is connected to the two vacuum chambers 51 and 52, which leads to a
water separator and to a vacuum source. The control flaps 62 and 63
are located at the connection between the suction duct 5 and the
two vacuum chambers 51 and 52, it being possible for the control
flap 62 to be pivoted about the axis 62a and the control flap 63 to
be pivoted about the axis 63a at right angles to the axis 62a. By
means of the control flaps 62 and 63, the vacuum prevailing in the
chambers 51 and 52 can be controllered. As is additionally
indicated by a double arrow D, the spray pipe 56 can be displaced
to and fro in an oscillatory manner, the amplitude of the
oscillatory movement being approximately equal to the spacing from
one another of the spray nozzles 57 provided in the spray pipe
56.
[0043] As can further be seen from FIG. 4, the second vacuum
chamber 52 is constructed with a base 52a running obliquely. This
ensures that the suction action of the second vacuum chamber 52 is
approximately the same over the width of the screen 1.
[0044] As FIG. 5 shows, the screen 1 bears on the roller 11c over
its entire length in the suction area of the first vacuum chamber
51. Since, in addition, the spray pipe 56 can be rotated about its
longitudinal axis, the direction of the water jets emerging from
said spray pipe can be adjusted over the angular range of about
.alpha.=30.degree. in the direction of movement of the screen
1.
[0045] As can further be seen from FIGS. 5, 6 and 6A, the upper
edges of the sidewalls of the vacuum chambers 51 and 52 are
profiled in a T-shape, and the sealing strips 53, 54 and 55 are
formed with oppositely profiled grooves. By this means, the sealing
strips 53, 54 and 55 can be pushed on to the upper edges of the
sidewalls of the vacuum chambers 51 and 52. In order to be able to
adjust the width of the effective area of the second vacuum chamber
52, the sealing strip 55 is asymmetrical as compared with its
groove. Depending on the position wherein the sealing strip 55 is
pushed on to the associated sidewall, the effective width of the
area of the second vacuum chamber 52 which is effective with
respect to the screen 1 can be adjusted with the values s and
s1.
[0046] As illustrated in FIGS. 7, 7a and 7b, according to a further
embodiment, the spray pipe 56a is constructed with a first group of
needle-jet nozzles 57a and a second group of flat-jet nozzles 57b,
which are offset with respect to one another in the longitudinal
direction of the spray pipe 56a, and whose jets form an acute angle
of about 10.degree. with one another. Furthermore, the planes of
the jets of the flat-jet nozzles 57b form an angle of about
5.degree. with the plane formed by the jets of the needle-jet
nozzles 57a.
[0047] The operation and functionality of the cleaning device 5
will now be explained with reference to the first screen 1:
[0048] The screen 1, which is constructed as an intrinsically
closed belt, or an endless belt, is placed over the guide and
deflection rollers, 11, 11a, 11b and 11c, bearing on these rollers
with that side which does not come into contact with the paper web
6. The cleaning device 5 assigned to the roller 11c has two vacuum
chambers 51 and 52 which follow each other in the direction of
movement of the screen 1. In the active area of the first vacuum
chamber 51, the screen 1 bears completely on the roller 11c, the
vacuum chamber 51 being on that side with which the screen 1 is
laid on the paper web 6. This is accordingly that side on which the
predominant part of the paper fibers and the like are located. The
vacuum chamber 51 is sealed off with respect to the screen 1 by
means of the sealing strips 53 and 54. Since the screen 1 is guided
by the roller 11c, it is ensured that it does not rub on the
sealing strips 53 and 54. This is critical because the screen 1 is
very susceptible to mechanical damage.
[0049] By means of the spray pipe 56 in the vacuum chamber 51, a
cleaning liquid, in particular water, is sprayed onto this side of
the screen 1, but does not pass through the screen 1 but instead,
because of the centrifugal force which occurs as a result of the
deflection of the screen 1 being moved at high speed, emerges again
on the same side and is led away via the vacuum chamber 51 and the
extraction line 61. Since the cleaning liquid is applied to that
side on which the contaminants are found, a very high efficiency is
achieved. In order to achieve an optimum cleaning effect, the
direction of the jets of the cleaning liquid with respect to the
direction of movement of the screen 1 can be adjusted in the range
of the angle .alpha.. In addition, the spray pipe 56 executes an
oscillating displacement transversely with respect to the direction
of movement of the screen 1, as a result of which the screen 1 is
covered over its entire width by the cleaning liquid. Contaminants
are removed from the screen 1 by the cleaning liquid. The screen 1
then passes into the area of the second vacuum chamber 52, which
comes to act on said screen between the sealing strips 54 and 55.
In this area, the screen 1 rests on the roller 11c only in a first
part, whereas it is lifted off the screen 11c in the second part.
In this area, firstly the water in the screen 1 is extracted and,
secondly, air is sucked in from the outside, as a result of which
the screen 1 is dried.
[0050] The action of the vacuum chambers 51 and 52 is controllered
by means of the control flaps 62 and 63. Since the second vacuum
chamber 52 is constructed with a cross section that widens in the
suction direction, a uniform suction action is achieved over the
width of the screen 1.
[0051] By means of the needle-jet nozzles 57a, the surface of the
screen 1 is cleaned in the first vacuum chamber 51, dirt particles
which have been deposited and dried on to said screen being removed
there. By means of the flat-jet nozzles 57b, the cavities in the
screen 1 are filled with water. In the second vacuum chamber 52,
this water is sucked out and, with the latter, the fine particles
out of the screen 1.
[0052] A device is therefore provided which, as compared with known
cleaning devices, has a simplified constructional design, as a
result of which it is cheaper to produce and also takes up less
space, which is far more effective and economic and cheaper in
operation and wherein damage to the screen which is very
susceptible to damage, is avoided to the greatest possible
extent.
* * * * *