Note: Descriptions are shown in the official language in which they were submitted.
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Cl~nin~ Device
The invention pertains to a device for cle~nin.~ a conveyor belt in a paper
s m~chinP, for e~mrle an endless circ~ ting wet or dry screen belt or felt band,with at least one nozzle that can be directed towards the fabric belt, particularly
in a direction perpendicular to the fabric belt, to apply air or liquid to the fabric
belt.
o Many fabric belts, particularly woven fabric belts, are used in paper m~chines.
In the course of paper machine operations, these fabric belts become dirty; for
example, the meshes or pores of these belts are filled with paper fibres, glue or
other residual material. Cleaning of the fabric belt is required in order to
ensure flawless operation of the fabric belt, particularly in the dry section ofS paper mA~hin~s.
A cleaning device of the type mentioned above and that can be used for ~is
purpose is known from publication G 92 08 909.7 Ul. That publication
mentioned the idea of arranging adjustable nozzles so that they can also rotate,20 perpendicular to the operating direction of the fabric belt, so that the jet, in
ition to describing a linear path due to the adjustability perpendicular to the
direction of movement of the fabric belt, is also capable of a circular motion
superimposed on this linear motion. The advantage of a cleaning device
clesi n~ in this way is that the liquid sprayed onto the fabric belt to be cleaned
25 can be applied more evenly and on a larger area of the fabric belt. In other
words, the rotary nozzle covers a relatively wide band of the fabric belt instead
of a linear one. Tllclcrol~, this fAt'-ilitAtes UllirUllll cle~nin~ of the entire surface
of the circulating fabric belt.
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With the known cleaning device, the fabric belt is sprayed with cleaning fluid
from above and from the side opposite to the carriage side, after a 180~ turn.
The rotary nozzles are thus arranged within a loop of the endless fabric belt.
Gutters are provided underneath the fabric belt in order to collect and drain
s away the cleaning fluid and the dirt picked up. However, use of this device
creates spray water and/or waste water due to the jet that leaves the rotating
spray nozzle under high pressure and hits the fabric belt. It is also a
disadvantage that residual water remains in the fabric of the belt, thus wettingthe paper path which comes in contact a little later with the circulating fabriclO belt. This can hamper the production process, particularly with paper paths that
have surface weights of less than 50 g/m2.
It has already been proposed to add a blow-out device after a cleaning device
with liquid nozzles, whereby the liquid rem~ining within the fabric belt would
lS be blown out by means of compressed air. This solution, however, has the
disadvantage that it creates spray water or mist that, in turn, ends up wetting the
paper path of the paper machine. Nor does a known vapour blow-out device
with a suction device arranged after it on the same side of the fabric belt
provide s~ti~f~ctory results (DE 43 22 565 Al).
It is l~ crole the objective of the invention to im~?rov~ a cleaning device of the
above-mentioned type in such a way, that the above-mentioned drawbacks are
elimin~t~-l that the device is compact and in particular economical to produce,
while being reliable in operation.
According to the invention, this objective is achieved by providing a suction
chamber immediately ~ ou-lding the nozzle in such a way that the dirt
loosened from the conveyor belt and/or the water spray or residual water can
be sucked into and discharged from the suction chamber over the shortest path
30 possible.
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Within the framework of a preferred cleaning device, the suction chamber
consists of a suction bell that ~ ds the nozzle like a cloak. This makes it
possible to create a compact, solidary nozzle and vacuum device combination
5 structure. The suction bell can consist preferably of a basically cylindrical
nozzle ~h~th, which - as mentioned earlier - moves laterally across the
conveyor belt. Instead of a sheath of circular cross-section, an elliptical or
oval-shaped sheath may also be used. The nozzle or nozzle-head can be
positioned eccPntri-~lly with respect to the sheath, perpen~ r to the direction
o of conveyor belt advance.
Within the rldll~work of a plcr~l~d impl~ ;on mode of the invention, the
suction bell at its ~ n~ity aimed at the conveyor belt widens conically or
~imil~rly to a bell. This increases the conveyor belt area covered by the suction
15 bell or the suction chamber.
A slant of the nozzle relative to the perpendicular to the conveyor belt surfacewas found to be particularly advantageous. As an example, there could be
several nozzles ~l~nte-l in different directions; they could be arranged without20 rotating in the suction bell that moves across the conveyor belt. However, there
should preferably be at least one rotary and one slanted nozzle, as this enablesthe jet to better loosen the dirt stuck to the conveyor belt, since the rotation of
the nozzle provides a cleaning jet that hits the conveyor belt from different
directions. It was found that the cle~nin~ effect is most effective within a rotary
25 motion that provides the nozzle or jet with a velocity component opposite to the
direction of advance of the conveyor belt. It is therefore proposed to deactivate
the nozzle by means of flow techniques within the other section, where the
rotary nozzle jet has a velocity component parallel to the direction of advance
of the conveyor belt. A baffle could be provided for this purpose in order to
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~U~ ss the impact of the nozzle jet. With a view to achieving economical use
of water, it may also be feasible to provide advantageously nozzle adduction
piping that impin~s dirr~.cnlially by section. It should also be noted here that,
instead of a rotary nozzle, there could be a rotary nozzle head with several
5 nozzles, one or more of the said no77l~ being designed as drive nozzles for the
rotation of the nozzle head. It is also feasible to provide at least one additional
nozzle, the output flow direction of which is oriente~l away from the conveyor
belt, so that the sole purpose of the additional nozzle is to act as a rotation
drive.
In order to expand the invention further, it is proposed, in order to produce
underpressure in the suction chamber, to provide a compressed air injector that
can be connected to the suction chamber by means of flow technology.
15 In order to achieve as effective a suction action as possible, it was found
particularly advantageous to have the opening of the suction bell that is aimed
at the conveyor belt well-adapted to the surface structure of the conveyor belt
or to the cylin-lric~l form of a roller supporting the conveyor belt.
20 The best results were achieved with a cle~ning device that could produce water
pleS:~llLeS of 100 bar - 1000 bar. In order to ~ the amount of liquid used,fluid nozzles with a nozzle diameter of less than 0.3 mm were used. Di~mon-l,
ruby or ceramic materials were used as nozzle materials.
25 The ~tt~ch~ drawing as well as the following description of various
advantageous implem~nt~tion formats of the cleaning device according to the
invention provide further characteristics, details and advantages of the
invention. The following is shown in the drawing:
~ CA 02213100 1997-08-1~
Figure 1 an implementation type of the cleaning device according to the
invention;
Figure 2 a cross-section of a nozzle head to be used with the device as per
s Figure l;
Figure 3 a bottom view of the nozzle head as per Figure 2,
Figure 4 a partial cross-section of the cleaning device according to the
o invention, according to an additional implement~tion example;
Figure S a top view of the cleaning device as per Figure 4;
Figure 6 a cross-section through a cleaning device in accordance with an
additional implement~tion example, and
Figure 7 a schematic representation of a dry section with the cleaning
devices according to the invention.
20 Figure 1 shows an impl~--P~ lion mode of the cleaning device 2, designed for
cleaning a dry screen belt 4 within range of roller 6 of a paper m~c~hine (not
shown). The cle~ning device 2 comprises a rotary nozzle 8 with a rotary nozzle
head 10, that exhibits a nozzle arrangement that is not shown. This nozzle
arrangement may comprise one or more tangential flow drive nozzles for the
25 production of rotary motion in the range of 2000-3000 revolutions per minute,as well as one or more cle~ning nozzles, used to apply an impact jet upon dry
screen path 4.
lition, a cylindrical suction bell 14 is provided, ~ oullding nozzle 8 and
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nozzle head 10. The interior of suction bell 14 is connected flow-wise to a
s~ ti~ n pipe 16, and it constitutes a suction chamber lS ~.c.cign~d to the nozzle.
The cleaning device 2 comprises an energy chain for the supply of the liquid
s medium, and the illustration shows basically that portion which comprises a
high ples~ pipe 20, connectable to a high pressure pump for supplying the
nozzle with fluid in a L~l~s~ range of preferably 150 bar - 300 bar, as well as
suction pipe 16 for the disposal of water spray or mist together with the dirt
particles therein, from suction chamber 18.
The components of cleaning device 2 described up to this point are positioned
on a traversing carrier 11 in a direction that is adjustable cross-wise to the
direction of advance of the dry screen 4. The traversing carrier 11 is seated oncross-supports 12 and it can be driven at an adjustable speed by a Llavel~illg
lS motor, not shown, with the traversing speed being generally in the range of 3
m/min.
As Figure 1 shows, end section 22 of suction bell 4, directed at the dry screen
4, is adapted to the circular-cylindrical shape of roller 6, so that between
20 suction bell 14 and dry screen 4 there is a certain adjustable gap or crack, which
is basically constant along the edge 24 of end section 22.
During operation of the cleaning device, cleaning fluid, particularly high-
pressure water, impinges through high-pressure pipe 20 on rotary nozzle 8, or
25 on the nozzle arrangement in nozzle head 10. This creates a rotary motion of
nozzle head 10 with the nozzle arrangement, due to the reaction effect of drive
nozzles. The fluid jet of the cle~ning nozzle, which is positioned at a specificangle to the longi~l~lin~l nozzle axis 26, follows a conical path 27, thus
impinging at an angle on the dry screen 4, thereby loosening the dirt from its
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surface. Due to the juxtaposition of the traversing motion and of the rotary
motion of the cleaning nozzle, the dirt particles are hit by the fluid jet of the
c1~ning nozzle from dirr~ell~ directions, and they can thereby be loosened
more easily than when using a nozzle travelling parallel to the l~ngitu-lin~l axis
s direction 26. An additional effect of the slant of the cleaning nozzle or fluid jet
is that the impin~ing fluid jet is reflected into suction chamber 18, thus m~king
it possible to elimin~te through suction pipe 16 the water mist thus created
together with the dirt particles and residual water connected with it. A suctioneffect or stre~ming, represented by the arrows, is therefore created. No spray
lO water therefore occurs around the suction bell 14, and dirt or water release can
th~ l~,fol~ be ~u~L~lLially prevented. It was found particularly advantageous toproduce the underpressure in suction chamber 18 and suction pipe 16 by means
of a compressed air injector. It was also found advantageous to have an
adjustable underpressure in suction chamber 18 in order to be able to adapt to
diverse opelaLillg conditions.
Figures 2 and 3 show dirrelenL views of nozzle head 10' corresponding to a
rotary nozzle head 10. Nozzle head 10' is attached in rotatable fashion to a
flange 30 by means of bearing 28. Inside flange 30 there is a fixed nozzle
20 adduction pipe 32 that ends at a pressure chamber 34, the walls 36 of which lie
tightly, but able to slide, against the inside of a cylindrical component 38. The
cylindrical component 38 has four openings arranged at an angle of 90~ to each
other. CnnnPct~l to them are nozzle ~ u~tion pipes 40, which are positioned
outward radially, and the end section of which is bent preferably at 90~, as
25 clearly indicated in Figure 5. The nozzle adduction pipes 40 finally termin~te
in bent cle~nin~ nozzle end sections 42. The drive nozzles, also provided, are
not illustrated. As Figures 2 and 3 also show, at all times only one of the
nozzle adduction pipes 40 is under jet pressure, while the rem~ining nozzle
adduct;on pipes 40 are without pressure. Pressure chamber 34 is positioned in
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such a way that the fluid jet contains a velocity component opposite to the
direction of advance of the dry screen 4, so that the cleaning effect is
particularly strong. At the same time, however, the nozzles the fluid jet of
which would have a velocity component in the direction of advance of the dry
s screen belt 4, are without plCS~ulc and thus deactivated with a view to reduce water con~llmrtion.
The cleaning nozzles are designed for a pressure range of 150 bar - 300 bar,
and have a nozzle diameter of 0.3 mm. Sapphire or ceramic materials are the
o pler~l~ed nozzle materials.
Figures 4 and 5 show schematically a second impleml--nt~tion example of a
cl~ning device. This corresponds basically to the cle~ning devices described
with lcr~lculce to Figures 1 to 3, and a repeat explanation of the corresponding5 parts is thelcro-c omitted here. One difference is the oval cross-section of
suction bell 14, whereby the nozzle head 10 is positioned eccentrically against
the direction of advance of the belt (arrow P). This improves the suction
exerted upon the water mist (charged with dirt).
20 An additional difference between this cle~ning device and the one shown in
Figure 2 is that there is no pressure chamber 34. The water pipe 32 is
connected to all four nozzle adduction pipes 40 shown in Figure 5. Pressure
therefore impinges upon all four nozzle adduction pipes 40.
25 Between nozzle head 10 and dry screen belt 4, there is a baffle 61, the
uul~ ost edge 63 of which is angled. This edge 63 acts as a fixation edge for
ribs 65, which are in turn connected to the internal wall of suction bell 14.
Between the individual ribs 65, the wall of the suction bell 14 and the baffle
edge 63, openings or cracks 67 are created, which connect suction chamber 18
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to the outside.
~ baffle 61, there is a passage 69 located within the action radius of the rotating
cle~nin~ nozzle 71. The ~limPn~ioning and position of this passage 69,
s particularly in the perimeter direction of baffle 61, are such that at all times at
least one cleaning nozzle 71 runs through this area with the nozzle jet direction
here being opposite the direction of advance of the belt (arrow P).
In accordance with the function already described of pressure chamber 34, this
lO makes is possible at any rate to have only one cleaning nozzle 71 impinge upon
the dry screen belt 4. The three additional cle~ning nozzles shown in Figure 5
do indeed operate as well, but the fluid jet does not impinge on dry screen belt4 but on baffle 61. This fluid is aspirated into suction chamber 18, as indicated
by the arrows shown in Figure 4, and the edge 63 of baffle 61 has an additional
lS deviation function.
The fluid mist reflected from dry screen belt 4 is aspirated into the suction
chamber through baffle 69 or through the previously mentioned crack 67.
20 As with the first implem~nt~tion example, the rotor head 10 is driven by the
nozzles 73. Figure 4 shows that these nozzles 73 are designed in such a way
that the output flow has an axial flow component that is opposed to the axial
components of the fluid jet. This compensates the axial reaction forces, thus
relieving the bearing 28.
Howt;v~;l, the cle~ning process itself corresponds to that described in connection
with Figures 1 to 3. Therefore, no further details are provided here in this
respect.
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Figure 6 shows another implementation example of a cleaning device in
accordance with the invention, which does not, however, involve rotating
cleaning nozzles. Tn~te~d, the cleaning nozzles 81 are firmly ~tt~hP.l to the
suction bell 14. The cleaning nozzles 81 are positioned in such a way in the
5 middle of the suction bell 14 that the fluid jets 83 preferably meet at a point that
is o~osile the opening area of the suction bell 14. When that point is located
&c~ y on the conveyor belt, a focussed point impact can be achieved. If the
~lict~nre between the nozzles and the conveyor belt is modified, the intersection
point of the fluid jets is also changed. There is an impact surface instead of ao focussed point impact.
The fluid mist bouncing off the dry screen belt 4 is aspirated into suction
ch~l,t~L 18 as in the previous instances. The suction effect is strengthened by
the suction bell that contimles underneath the nozzles 18, and that ends tight
lS against the conveyor belt. Air streams through the crack 85 created between
the suction bell 14 and the conveyor belt 4, and it drags along the fluid mist.
As explained in the implemP-nt~tion examples already described, the layout of
the cleaning nozzles 81 is such as to ~ illli7e the component aimed in the
20 direction of advance of the dry screen belt 4.
Although only 3 cleaning nozzles 81 are shown in Figure 6, more than three
such cle~ning nozzles can be provided.
25 Figure 7 shows schematically a partial view of a dry section, indicating two
single-row dry sets 91 and 93. Each of these two dry sets 91 and 93 consists
in known f~hi~n of several dry cylinders 95 and deflection rollers 97. The dry
cylinder 9S and the deflection rollers 97 are arranged so that the paper path
passes alternately through the dry cylinders and the deflection rollers, and the30 dry set meanders through.
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To each dry set 91 and 93 is ~.eei n~l a dry screen belt 4 that enters the paperpath at the be~innin~ of each dry set, and is removed and returned back at the
end of the dry set.
s Figure 4 shows that a cleaning device 2 works each time together with a dry
screen belt 4. The two cleaning devices 2 are each time positioned at a dry
screen guide roller 6 within the initial section of the return of dry screen belt 4.
This allows the cle~nin~ fluid that is still on the dry screen belt 4 to evaporate
before the dry screen belt comes once again into contact with the paper path.
o l~e return guide rollers that follow roller 6 also contribute to removing fluid
from the dry screen belt 4, firstly through the overpressure that is created by
any "riser throat", and secondly through the centrifugal force exerted upon the
fluid particles travelling around the roller.
