Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
CA 02078~74 1997-10-20
~evice for C1~An~n~ a Revolv~np Pa~er M~hine Uire
The invention concerns a tevica for cleaning a revolving paper 9~hine
wire
Such or similar devices have becom- known from US-PS 3,265,559. They
were successful specifically in the cleaning of felts.
In selecting a cleaning system, various aspects need to be observet.
Uhat matters first of all is the cleaning effect itself, which must be
simultaneous and uniform across the entirc rsrhin~ width. Besides,
however, also th- energy consumption plays an important role. Further-
more, attention must be pait to low wear of the participating compo-
nents. Lastly, also waste water problems need to be avoided.
In wire cleaning, water ~ets have so far been employed primarily; these
are thrown at high pressure from spray nozzles at the wire to be
cleaned. ~hile the cleaning effect is very good, it is striped though,
at the spacing of the spray nozzles. The expense is rather high, espe-
cially the energy demand.
CA 02078~74 1997-10-20
Other problems join in, for in~t~nre the waste water problem.
The problem underlying the invention is to design a device in a way such that the cleaning
effect will be improved and that also all other problems, associated with the air nozzles,
will be solved in satisfactory fashion.
According to the present invention there is provided a device for cleaning a wire web, the
wire web supporting a fiber material web and defining a running direction, said device
comprising: two elongated members disposed parallel to each other and ext~n-ling cross-
wise to the running direction of the wire web, said two elongated m~rnbers comprising an
elongated approach member and an elongated d~p~l~ue member, said elongated approach
member and said elongated departure member each having a wire guide surface cont~cting
the wire web; a blowing slot disposed between said elongated approach member and said
elongated dep~lure member, said blowing slot adapted to be connPcted to an air supply; a
wedge-shaped space defined by and between said elongated approach member and the wire
web, said wedge-shaped space tapering in the running direction of the wire web; and a
water spray system, said water spray system all~rted to spray water into said wedge-
shaped space.
The inventional introduction of water into the wedge-shaped gore between the approach
slat and the wire causes the wire - although only rather slightly - to lift off the approach
slat. At the same tirne, a water film forms on the inside of the wire, of the sprayed water,
which water film more or less covers this inside and, thus, also blocks the wire meshes.
Thus, there are no longer any free wire meshes, but the air discharging from the blow
nozzle impinges on a practically continuous wall of water.
Contrary to the prior embodiment - blowing air through the wire - the air jet thus can no
longer choose the path of least resistance through open wire meshes. It must penetrate the
entire wall of water. In the process, it entrains of n.oces~ also the dirt particles clinging
to the wire, which are embedded in the water and deposited on the mesh
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wires. At any rate, tests have shown that the share of entrained dirt
particles increases abruptly if according to the invention water is
introduced only in the wedge-shaped gap between wire and approach slat.
The screen is simultaneously cleaned across the entire width.
In several applications, various additional requirements are imposed on
the wire cleaning system, which are cited hereafter:
1. To be avoided is the deposition of dirt on the system in continu-
ous operation, which impairs its effectiveness.
2. In order to save energy, a ~lIy low water pressure should
suffice for the water spray system while nevertheless achieving a
' ~lly uniform spray water distribution across the wire width.
3. It should be possible to adapt the system to various wire running
speeds, thus keeping the cleaning effect equally high at different
wire N nning screens.
4. The system should be usable also where the web formed is in normal
operation lifted of~ the wire (for instance by means of a pick-up
suction roll) and where during the start-up phase the web must be
passed from the wire to a scrap dissolution system.
CA 02078574 1997-10-20
- 4 -
Th- i~vention will b- morc fully explain-t with tho aid of the trawing,
which in detail~ shows in
~ig 1 through 4, schematic illustrations of variow wire sections for
for paper ~rhin~;
Fig 5, scaled up, th- actual system according to the invention,
with high-pressure blow nozzle and a water spray system;
Fig 6, schematically, part of a paper ~ n- wire section with a
wire cleaning systs2;
Fig 7, a partial view of th- wire cleaning systcm in the direction
of arrow II in Fig 6;
Fig 8, scal-d up and motifiet as compar-d to Fig 6, a partial
cross section of the wir- cleaning system
The wire section illustrated in Fig 1 features a wire 1 wrapping around
a number of rolls and mo~ing in th- dir-ction of the arrow The actual
cleaning de~ic- comprisas espacially the high-pressure blow nozzle 2 and
a spray pipe 3 for application of water ~-ts Further cleaning organs
are arranget aheat, for instanc- another spray pip- 4, which shoots
water ~ets through tha wire 1 The water ~etQ are collectet in a suction
hood 5
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Coordinated with the actual, inventional cleaning system 2, 3 is a
suction system 6 with a lateral vacuum connection.
In the system according to Fig. 2, blow nozzle 2 and spray pipe 3 - in
this case a flat jet spray pipe ~ are again the ma~or c. ,ol~ents of the
cleaning system. These two components are arranged on the inside of the
wire, i.e., inside the loop formed of the wire 1. Provided on tha out-
side is a hood 5 which features a water drain 10 and is hooked to a suc-
tion pipe 11. Preceding the flat jet spray pipe 3 is a needle jet spray
pipe 4. While this is helpful, it is not decisive though. The embodi-
ments according to Fig. 3 and 4 represent modifications. Essential here
are also high-pressure blow nozzle 2 with preceding spray pipe 3. The
suction hoods 5 serve at the same time to collect the splash water and
to provide suction. They feature appropriate connections, the same as
the embodiment according to Fig. 2.
Fig. 5 depicts very exactly the structure of the high-pressure blow
nozzle. It comprises an approach slat 20, a departure slat 21 and a
pressure tube 22. Forming an assembly, these three said components
extend across the entire -~h~n~ width, so that the wire 1 is cleaned
across its entirs width. Approach slat 20 and departure slat 21 form a
blowing slot 23, which without interruption can extend across the wire
width. But it may also be interrupted. It may be replaced, e.g., by a
number of bores, which as well extend across the entire wire width.
207~74
Decisive is the shape of the approach slat 20 and the routing of the
wire 1. As can be seen, these two form an angle ~ with each other. In
the present case, the angle ~ amounts to about 30~. The wedge-shaped
bore 24 forming between these two tapers thus in the wire running direc-
tion.
Preceding the gore 24 is a spray pipe 30 arranged in such a way that it
supplies directly or indirectly spray jets 31 of water to the gore 24.
The supply may occur at a more or less high pressure.
The two slats 20 and 21 are made, at least on their surface touched by
the wire, of wear-resistant material, for instance ceramic.
The wire runs on the approach slat 20, which at this point has a radius
of about 10 to 50 mm. Due to its reversal, the wire is already dewatered
at this radius, due to eccentric force.
The blowing slot 23 has a width of 1 to 10 mm.
The departure slo~ 21 forms in the departure area as well a radius. It
ensures that the wire will not be lifted off this slat by the air pres-
sure, so that the blowing air cannot escape. The radius required on the
departure slat 21 depends on operating parameters such as air pressure,
wire permeability, wire tension and others. The radius is so selected
that the r~ining contact pressure of the wire on the reversal surface
2~7~74
of ehe departure slat 21 will be min~ -1 keeping the slat wear and wire
wear as well in; ~1
The design of the control is such that the air will be turned off imme-
diately in case of water failure and that the blowing nozzle will swing
out of the wire - with a slight time delay~
Fig. 6 depicts a ~continuous revolving wire 1 which in known fashion runs
across a wire suction roll 35 and from there across a wire cleaning
system 40 and to a wire guide roll 36. The paper web appro~ching on the
wire 1 (and still wet) is in normal operation picked off the wire and
passed to the successive (not illustrated) press section, with the aid
of a continuous felt 38 and a pick-up suction roll 37. During the start-
up phase or upon operational bréakdown, the pick-up suction roll 37 is
with the aid of hydraulic cylinders 39 lifted off the wire 1 in known
fashion (as illustrated by dash dot lines). In this state of operation,
the web runs with the wire 1 up to the wire cleaning system 40, is
separated by it from the wire and runs then approximately along the
broken line S downwart into a not illustrated scrap dissolution system.
As can be seen best from Fig. 8, the wire cleaning system 40 has an
approach slat 41 and a departure slat 42, each touching the revolving
wire 1 with a wire guide surface. The width of the wire guide surface of
the approach slot 41 is marked a, the width of the wire guide surface of
the departure slat is marked b. The two wire guide surfaces are approxi-
2~78~7'1
mately eq~ally wide, while the overall width A of the approach slat isnearly twice as large as the overall width B of the departure slat. The
wire guide surfaces may be pred~ nAntly flat (with rounded edges) or
have a slightly convex curvature. The slats 41 and 42 are fastened to
the support body 43 in such a way that an air blowing slot 44 L.- -~nQ
between the two slats. The support body is fashioned as a hollow body
serving to supply blowing air. Forming between the approach slat 41 find
the wire l is a wedge-shaped gore 45 (with angle w) tapering in the wire
running direction. A water spray system 46 sprays water jets across the
entire wire width into the gore 45.
At the point where the wire l leaves the wire guide surface, the depar-
ture slat 42 features a stepped clearance 47; the latter forms with the
wire guide surface a relatively sharp teparture edge, which the wire
must touch. This configuration achieves that the surfaces of the depar-
ture slat 42 which are not in contact with the wire tend less than here-
tofore to A~ te dirt that might impair the proper functioning of
the wire cleaning system 40.
Due to the larger overall width A of the approach slat 41, the wedse-
shaped gore 45 (in the direction of wire travel) is longer than hereto-
fore. This gives rise to the possibility, more so than heretofore, that
the wire l accelerates the water jets coming from the water spray system
46. Thus, the pressure of the supplied water can be reduced as compared
to formerly, thus saving energy. To allow the adjustment of optimum
. ' 207~7~
conditions in this respect, the angle w between wire 1 and approach slat
41 is suitably changed, specifically to thereby adapt it to the wire
travel speed. The support body 43 is for that purpose pivotably support-
ed in bearing blocks 47. Additionally or alternatively to it, the sup-
port body 43 can be shifted toward the wire 1 or away from it, along
with the bearing blocks 47.
According to Fig. 8, the water spray system, referenced 46' overall, is
formed of two mutually parallel chambers exten~in~ transverse to the
direction of wire travel; these are a distribution chamber 48, to which
a water supply line 50 is hooked, and a nozzle chamber 49. Distributed
across the length of the chambers, several channels 51 connect the dis-
tribution chamber 48 with the nozzle chamber 49. This ensures that the
water discharge velocity is uniform across the width of the wire 1. In
variation from Fig. 3, the di~tribution could be replaced by a pipe
which through several lines corresponding to the channels 51 is con-
nected to the nozzle chamber 49.
A series of individual spray nozzles may be provided on the nozzle cham-
ber 49. Alternatively to it, a water discharge gap 52 forms according to
Fig. 8 between two walls of the nozzle chamber. If a variability of the
amount and/or discharge velocity of the water is desired, a wall 53 of
the nozzle chamber 49 (which at the same time is a defining wall of the
distribution chamber 48) can be shifted back or forth in the direction
of double arrow 54, thereby varying the clearance of the gap 52.
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According to Fig. 6 and 7, the water spray system 46 comprises a spray
pipe 56 which extends across the entire wire width, and additionally, in
the area of the two web edges, an edge spray pipe 57 each (of which only
one is visible in the drawing). The edge spray pipe 57 has per centime-
ter of wire width a greater number of spray noz~les, which are arranged
distributed across the width R of the edge strip. As is known, an edge
strip is normally trimmed off the paper web formed in the wire section,
on each of the two edges, which edge strip must in normal operation be
picked off the wire 1 by means of the wire cleaning system 40~ Only the
r~-ining paper web with the width P continues to be advanced by means
of the felt 38.
Now and then it happens that the width P of the paper web to be produced
needs to be changed. To enable the adaptation of the wire cleaning
system 40 to different web widths P, the following is provided for: The
edge spray pipe 57 can be moved parallel to the blowing slot 44. Be-
sides, the length (P + 2R - measured crosswise to the wire travel direc-
tion) of the blowing slot 44 is variable with the aid of adjustable edge
slides 58.
Fig. 6 also shows the control of the hydraulic cylinders 39 of the pick-
up suction roll 37 and the control of the air and water supply to the
wire cleaning system 40. Illustrated is a central control unit 60, a
water pump 61 and a compressed air supply 62. The compressed air line 63
with pressure control valve 64 connects the compressed air supply 52 via
2078~ 7~
-- 11
the hollow support body 43 to the blowing slot 44. The water pump 61
connects directly to the edge spray pipe 57, through a line 65. Addi-
tionally provided is a line 66 with pressure control valve 67 for sup-
plying the spray pipe 56. A com~on control line 6~ connects the control
center 60, for one, with the pressure control valves 64 and 67 and, for
another, with a transmitter 69 controlling the hydraulic cylinders 39.
The following can be accomplished thereby: During normal operation
(pick-up suction roll 37 tou~ing the wire 1) air and water are supplied
to the wire cleaning system 40 at relatively low pressure. An exception
are only the edge spray pipes 57, to which water is fed at high pressure
through the line 65, so that the edge strips will be safely removed from
the wire l. As soon as the control center 60 emits a signal for liftoff
of the pick-up suction roll 37 from the wire l (or shortly before), the
pressure control valves 64 and 67 ad~ust automatically to the effect
that now the air pressure and water pressure will be raised. Consequent-
ly, the wire cleaning system 40 is immediately able to separate the en-
tire web (with width P + 2R) from the wire 1. What this control achieves
is that in normal operation the air and water coY,s~ ,tion will be rela-
tively low and that the wire cleaning system 40 can automatically be put
in a state where it carries a higher operating pressure, which is re-
quired in lifting the pick-up suction roll 37 off the wire l or separat-
ing the entire web.
Another possibility for reduction of the air and/or water consumption in
normal operation is given by the following: A time relay 70 can be con-
2078~7~
nected through lines 71 and/or 72 with the pressure control valves 64and/or 67. This time relay can in adjustable time intervals initiate a
temporary pressure increase in the lines 63 and/or 66. Achieved thereby,
temporarily, is an increased clenn~'ng e~fect at, on average, low air and
water consumption.
