Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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DEVICE FOR CLEANING AT LEAST ONE WIRE IN A F?LANT FOR PRODUCING
PAPER
The present invention relates to a device for cleaning the at
least one vaire in a plant for producing paper, in which the
wire is led over rolls, comprising at least: one vacuum chamber
which bears against the wire and at least one spray nozzle
arranged in said vacuum chamk;er, through which a cleaning
liquid, in particular water, can be applied to the wire.
In plants for producing paper, a fibrous suspension is applied
to an intrinsically closed wire lecl over rolls. Plants are
also known in which two wires are ~~rovi_ded, between which the
paper web is produced. In all the plants there is the
requirement for the at least one wire, in an area in which it
is lifted off the paper vaeb and led back t.o the start of the
plant, to be cleaned from cornponent;s remaining in and on it,
in particular pulp fibers, and to be dried.
US 6,099,691 A discloses a device for cleaning the wire of a
plant for producing paper, which device comprises four vacuum
chambers, of which ira each case t:wo are arranged on both sides
of a wire and in whic:O there are s~>ray nozzles, through which
water is sprayed onto both s~.~rf:ac:es of the wire, as a result
of which the latter i.s cleaned. The water applied through the
spray nozzles is fed from the vacuum chambers to a separator.
In addition, the wire is acted on by air in one of the vacuum
chambers in order to dry it.
Such known devices for cleaning <~ wire are, however, afflicted
by a number of disadvantages:
Since vacuum chambers are provided on both sides of the wire,
a very great amount of space is necessitated by this device.
Since the wire is led through between at least two vacuum
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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. Tn addition, there
is the requirement to connect the vacuum chambers arranged on
both sides of the wire to separate vacuum sources and, in
addition, to assign water separators in each case to these.
Furthermore, the water applied to t:he wire by the spray
nozzles passes through said wire, carrying the contaminates
with it. However, since the predominant proportion of the
contaminants is located on that side of the wire on which the
paper web rests, this necessitates the water applied to this
side of the wire carrying the contaminants through the wire
into the vacuum chamber arranged on the other side of the
wire. As a result, this c~~.eaning device has a very poor
efficiency and/or is relatively expensive in operation.
The present invention is therefore based on the object of
providing a device for cleaning the at least one wire in a
plant for producing paper by means of which the disadvantages
attached to the known prior art are avoided. According to the
invention, this is achieved in that the at least one vacuum
chamber is arranged radially outside one of the rolls, over
which the wire is led back to the start of the plant, the wire
in the effective area of said vacuum chamber bearing on this
roll at least over a major part of its length.
Therefore, at least one vacuum chamber is provided only on
that side of the wire on whch 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 wire resting
on the roll, and emerges from the wire again on this side,
carrying the contaminants with it. By reducing the number of
vacuum chambers provided an<j the vacuum sources associated
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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 wire is led
over a roll 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 wire on which the paper web comes
to rest. By this means, any damage to the wire resulting from
the edges of the entry and exit openings of the at least one
vacuum chamber is ruled out.
The at least one vacuum chamber is preferably sealed off with
respect to the wire led over the roll by means of sealing
strips aligned transversely with. respect t:o the direction of
movement of t}~e wire. Furthermore, the wire in the area of the
first vacuum chamber preferably bears on the roll over the
length of this vacuum chamber. Tn 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 wire.
According to a preferred embodiment, at least one second
vacuum chamber is provided radially outside the roll in the
direction of movement of the wire, in addition to the at least
one vacuum chamber. In this case, the wire in the area of the
first vacuum chamber can bear on the roll. over its entire
length, and the area of the wire in the effective area of the
at least one second vacuum chamber can bear on the roll over
part of its length and be gifted off the roll over a further
part of its length.
The at least one first vacuum chamber and the at least one
second vacuum chamber are preferably connected to a common
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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 resper.t to the direction of movement of the
wire. 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 wire, at least
some of the edges of the walls of the vacuum chambers,
assigned to the wire and aligned transversely with respect to
the direction of movement of the latter, are sealed off with
respect to the wire by mean; 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 side walls cf the vacuum chambers, and at least
some of the sealing strips cre. as~~mmetrical.
Finally, the spray pipe is preferably formed with needle-jet
nozzles and with flat-jet nuzzles"
The subject of the invention is explained in more detail below
using an exemplary embodiment illustrated in the drawing, in
which:
Fig. 1 shouas a plant for producing paper, in a schematic
illustration;
Fig. 2 shows a device according to the invention, in a
vertical section led in the direction of movement of the wire;
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Fig. 3 shows this device in section along the line III-III in
Fig. 2;
Fig. 4 shows this device in section along the line IV-IV in
Fig. 2 on a scale reduced with respect to Fig. 2;
Fig. 5 shows the detail A from Fig. 2 on a scale increased
4aith respect to Fig. 2;
Fig. 6 shows the detail B from Fig. 2 on a scale increased
with respect to Fig. 2;
Fig. 6a shows the detail B in a design variant on a scale
increased with respect to Fig. 2; and
Figs. 7,7a,7b show a component of this device, in side view,
in plan view and in section.
Fig. 1 shows a plant according to the invention for producing
paper, which has a first wire 1 and a second wire 2. These two
wires 1 and 2, which are intrinsically closed, are moved over
a plurality of guide and deflection rolls 11 and 21 associated
with them at the same speed of, for examp7_e, about 40 m/sec,
being led on each other in the area of the rolls 11a and 21a
and separately from each other in the area of the rolls llb
and 21b. In that area in which the two wires 1 and 2 are moved
resting on each other, there is a spray nozzle 3. Furthermore,
a plurality of suction boxers 4 is provided on both sides of
the wires 1 and 2. In ac.idition, a further spray nozzle 3a and
a suction box 4a are arranged in the further course of the
first wire 1. Finally, cleaning device 5 for the two wires 1
and 2 are arranged in the area of the guide rolls llc and 21c.
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Additional cleaning devices of this; kind may be assigned to
the first wire and the second wire 2.
During the operation of this plant 1, in the area of the two
rolls lla and 21a, the pulp prepared for the production of a
paper web is introduced uniformly over the width of the two
wires 1 and 2 in the direction of t:he arrow C between the two
wires 1 and 2. By means of the suction boxes 4 provided in the
course of the two wires 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 wire 2 has been lifted off the
first wire l, remains on the latt:e:r, being dried further by
the further suction box 4a. Finally, in the area of a
deflection roll 16, it is lifted off the first wire 1 and fed
t:o further processing.
The spray nozzles 3 and 3<3 are used to wet the wires 1 and 2
when no pulp is resting on them.
Since the two wires 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:
As can be seen from Fig. 2, radially outside the guide roll
llc and at that point of the wire 1 on which the paper web 6
i_s laid, there are two vacuum chambers 51 and 52 following one
after the other in the c~ire~:tion of movement of the wire 1,
wt,:ose suction openings wire :pealed off with respect to the wire
1 by means of sealing strips 53, 59 and 55. Inside the first
vacuum chamber 51 there is a spray pipe 55 constructed with
nozzles 57, via which water can be sprayed onto the associated
side of the wire 1. Furthermore, control flaps 62 and 63 are
assigned to the vacuum chambers 57_ and 52.
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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 t=he 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 h3 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 controlled. 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 providE:d in the spray pipe 56.
As can further be seen from Fig. 9, 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 samf:~ over the width of the wire 1.
As Fig. 5 shows, the wire 1 bears on the roll llc 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 a = 30° in the direction of movement of the
wire 1.
As can further be ~.een from figs. 5, 6 and 6a, the upper edges
of the side walls 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
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edges of the side walls 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, them sealing strip 55 is
asymmetrical as compared with its groove. Depending on the
position in which the sea:Ling strip 55 is pushed on to the
associated side wall, the effective width of the area of the
second vacuum chamber 52 which is effective with respect to
the wire 1 can be adjusted with the values s and s1.
As illustrated in figs. 7, as 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° with one another.
Furthermore, the planes of '.he jei~s of the flat-jet nozzles
57b form an angle of about 5° with the plane formed by the
jets of the needle-jet nozzles 57a.
The mode of action of the cleaning device 5 is explained below
by using the first .wire l:
The wire l, which is constructed as an intrinsically closed
belt, is placed over the guide and deflection rolls, 11, 11a,
11b and 11c, bearing on these rolls with that side which does
not come into contact with the paper web 6. The cleaning
device 5 assigned to the rcell 11c: has two vacuum chambers 51
and 52 which follo~,~~ each other in the direction of movement of
the wire 1. In the active area of the first vacuum chamber 51,
the wire 1 bears completel~,~ on the roll 11c, the vacuum
chamber 51 being oru that side 4ait:h which the wire 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 wire 1
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by means of the sealing strips 53 and 54. Since the wire 1 is
guided by the roll 11c, it is ensured that it does not rub on
the sealing strips 53 and 54. This is critical because the
wire 1 is very susceptible to mechanical damage.
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 wire l, but does not pass through the wire 1 but
instead, because of the centrifugal force which occurs as a
result of the deflection of the wire 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 too 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 Gnire 1 can be adjusted in the range of the
angle a. In additicn, the spray pipe 56 executes an
oscillating displacement transversely with respect to the
direction of movement of the wire l, as a result of which the
wire 1 is covered over its entire width by the cleaning
Liquid. Contaminants are removed from the wire 1 by the
cleaning liquid. The wire 1 t?~en passes into the area of the
second vacuum chamber 52, which comes to act on said wire
between the sealing strips 54 and 55. Tn this area, the wire 1
rests on the roll llc only in a first part, whereas it is
lifted off the wire 11c: in the second part. In this area,
firstly the v.~ater i.n tie wire 1 i.s extracted and, secondly,
air is sucked in from tre outside, as a result of which the
wire 1 is dried.
The action of the vacuum chambers 51 and 52 is controlled by
means of the control flaps 62 and 63. Since the second vacuum
chamber 52 is constructed with a cross section which widens in
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the suction direction, a uniform suction action is achieved
over the width of the wire 1.
By means of the needle-jet nozzles 57a, the surface of the
wire 1 is cleaned in the first vacuum chamber 51, dirt
particles which have been deposited and dried on to said wire
being removed there. By means of t:~e flat-jet nozzles 57b, the
cavities in the wire 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 wire 1.
A device is therefore provided which, as compared with known
cleaning devices, has a simplified constructional design, as a
result of Gahich it is cheaper to ~~roduce and also takes up
lass space, 4.'hlCh is far mora effective and economic and
cheaper in operation and in which damage to the wire which is
very susceptible to damage, is avoided to the greatest
possible extent.
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