Note: Descriptions are shown in the official language in which they were submitted.
CA 02794186 2012-11-02
SUPPORTING ELEMENT, SUCH AS FOIL OR WIRE BOARD,
FOR USE IN A PAPERMAKING INSTALLATION
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims the priority, under 35 U.S.C. 119, of
Austrian
patent application AT A1748/2011, filed November 28, 2011; the prior
application is
herewith incorporated by reference in its entirety.
BACKGROUND OF THE INVENTION
Field of the Invention:
[0002] The present invention relates to a supporting element, such as a
foil or
wire board, for use in a papermaking installation which has at least one wire
and
preferably at least one felt which can be moved over supporting elements, the
supporting element, which can be fixed to a supporting frame of the system,
directly
or by means of a supporting element, being formed with wear protection in that
area in which the wire or the felt comes into contact.
[0003] Papernnaking installations are constructed with a wire, which is
moved
along the system, paper stock being sprayed onto the wire in the direction of
movement of the wire at the beginning of this system. The wire is guided over
supporting elements, such as foils and wire boards, the water in the paper
stock
being drawn off, by which means a web or strip of paper is produced.
[0004] As a result, this strip of paper can be transferred to a likewise
moving felt,
being dried further. The felt is also guided over supporting elements, such as
supporting bars and supporting boards.
[0005] In the further course, the strip of paper is smoothed by means of
rolls and
wound up on drums.
[0006] Since the supporting elements over which the wires or the felts are
guided are subjected to very high wear, which is also caused by fibrous
materials
being carried along with the water emerging from the paper stock, they have to
be
constructed with wear protection in that area in which the wire or the felt
comes into
contact.
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[0007] According to the known prior art, the supporting elements are
coated with
at least one layer of ceramic plates in that area in which the wire or the
felt comes
into contact. Ceramic plates of this type, which, for example, consist of
aluminum
oxide, are produced by pressing powdery starting material at high pressures in
a
mold to form plates, which are then sintered. These plates therefore meet the
requirements for wear protection in supporting elements in papermaking
installations, since they exhibit very high hardness and therefore very high
wear
resistance.
[0008] However, when they are used as wear protection in supporting
elements
for wires or felts, the ceramic plates have a number of disadvantages:
[0009] Since these plates can be produced only with small dimensions,
there is
the need, when coating a foil or a wire board, to arrange a multiplicity of
plates
beside one another. It is thereby necessary to ensure that their surfaces are
located
in a single plane, in which the wire or felt is moved.
[0010] Furthermore, because of the intended hardness of these ceramic
plates,
their processing is very complicated and expensive. In addition, because of
the
brittleness of these ceramic plates, there is a high risk of breakage, it
being
possible for the wire or the felt to be damaged in the case of breakages of
plates,
for which reason those supporting elements in which the ceramic plates are
broken
have to be replaced. In addition, foils coated with ceramic plates through
which a
suction action is exerted on the paper stock located on the wire exhibit
different
effects over their length transverse to the direction of movement of the wire
or of
the strip of paper on account of the gaps between the individual plates, as a
result
of which the quality of the strip of paper is impaired because of
inhomogeneities.
SUMMARY OF THE INVENTION
[0011] It is accordingly an object of the invention to provide a
supporting
element, such as foil or wire board, for use in a papermaking installation
which
overcomes the above-mentioned disadvantages of the heretofore-known devices
and methods of this general type and which provides for a supporting element
for a
wire system in which, although it likewise exhibits very high wear resistance,
the
disadvantages of the supporting elements coated with ceramic plates are
avoided.
[0012] With the foregoing and other objects in view there is provided, in
accordance with the invention, a supporting element in a papermaking
installation
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equipped with at least one wire and at least one felt to be moved over
supporting
elements. The supporting element, which is embodied as a foil or a supporting
board, can be affixed to a supporting frame of the papermaking installation,
directly
or by way of a carrier element, and
the supporting element is a composite element formed with wear
protection in a region thereof in which the supporting element comes into
contact
with the wire or the felt; and
the composite element has a layer of a metallic carrier material and a
hard metal layer sintered onto said metallic carrier layer, the hard metal
layer being
formed of a hard metal alloy having hard materials embedded therein.
[0013] European patent EP 446978 B1 describes forming the sliding mounting
of swivel plates as a hard nickel alloy, in which hard materials are embedded.
European published patent application EP 816525 Al describes constructing a
screen plate formed with passage openings for screening granular solid
materials
with a wear protection layer of a hard metallic alloy which is joined
metallurgically to
a protective layer of iron material, hard materials being embedded in the hard
alloy.
[0014] By contrast, it has previously not been known to use hard metallic
alloys
with hard materials embedded in the latter as wear protection in supporting
elements in papermaking installations. The reason for this resides in the fact
that,
by way of wear protection plates of a ceramic material as compared with wear
protection plates of hard metallic alloys, substantially longer acting wear
protection
is effected because of the far greater hardness of the ceramic material as
compared with hard metallic alloys.
[0015] The disadvantages of ceramic plates used hitherto as supporting
elements in papermaking installations are avoided, according to the invention,
in
that the supporting element is formed by a composite element which comprises a
layer of a metallic carrier material and a layer of a hard metallic alloy in
which hard
materials are embedded, the hard metal alloy being sintered onto the metallic
carrier material.
[0016] The present invention is based on the finding that, by using a wear
protection material which is known from unrelated prior art in supporting
elements
in papermaking installations, although the wear resistance as such is lower
than in
the case of the ceramic plates used hitherto, as a result of using a hard
metallic
alloy with embedded hard materials as wear protection in supporting elements
in
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wire systems or felt systems, a number of critical advantages are achieved
with
regard to the manufacture, the possible uses and the specific requirements in
papermaking installations.
[0017] The layer of the metallic carrier material is preferably composed
of a
corrosion- and acid-resistant stainless steel alloy, in particular an
austenitic
stainless steel having the material quality WS 1.4571 (AISI 316Ti) or WS
1.4404
(AISI 316L). According to a preferred embodiment, the layer of the hard
metallic
alloy is composed of a nickel-based hard alloy or it contains a nickel-based
hard
alloy. In particular, the layer of the hard metallic alloy is composed of a
mixture of
an iron-based hard alloy and a nickel-based hard alloy or of a nickel-
molybdenum-
based hard alloy. Likewise, the layer of the hard metallic alloy can be
composed of
a mixture of an iron-based hard alloy and a nickel-molybdenum hard alloy.
[0018] The hard materials are preferably formed by chromium carbides,
tungsten carbides, silicon carbides and boron carbides as such or in mixtures,
and
the proportion of hard materials in the basic hard alloy is 50% by weight to
90% by
weight.
[0019] Other features which are considered as characteristic for the
invention
are set forth in the appended claims.
[0020] Although the invention is illustrated and described herein as
embodied in
a supporting element, such as foil or wire board, for use in a papermaking
installation, 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.
[0021] 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 SEVERAL VIEWS OF THE DRAWING
[0022] Fig. 1, Fig. 1A show a wire system in a papermaking installation
in a
schematic illustration, a first sub-area of this wire system being shown in
Fig. 1 and
the following second sub-area being shown in Fig. 1A,
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[0023] Fig. 2, Fig. 2A show a first embodiment of a foil in cross section
according to the line II-II in Fig. 2A and in longitudinal section according
to the line
11A-IIA in Fig. 2A,
[0024] Fig. 3, Fig. 3a show a second embodiment of a foil in cross section
according to the line 111-11I in Fig. 3A and in longitudinal section according
to the line
IIIA-IIIA in Fig.3,
[0025] Fig. 4, Fig. 4A, Fig. 4B, Fig. 4C, Fig. 4D, Fig. 4E show six
embodiments
of foils, each in cross section,
[0026] Fig. 5, Fig. 5A, Fig. 5B show three further embodiments of foils,
each in
cross section,
[0027] Fig. 6, Fig. 6A, Fig. 6B show three further embodiments of foils,
each in
cross section,
[0028] Fig. 7 is a cross-section taken through a further embodiment of a
foil,
[0029] Fig. 8, Fig. 8A, Fig. 8B, Fig. 8C show a supporting element in the
form of
a wire board, in plan view and in sections according to the line VIIIA-VIIIA
in Fig. 8,
each on an enlarged scale,
[0030] Fig. 9 shows a detail of the wire system according to Fig. 1 und Fig.
1A,
on an enlarged scale, and
[0031] Fig. 10, Fig. 10A shows a further embodiment of a foil, in plan view
and in
side view and on an enlarged scale.
DETAILED DESCRIPTION OF THE INVENTION
[0032] Referring now to the figures of the drawing in detail and first,
particularly,
to Figs. 1 and 1A thereof, there is shown a wire system in a papermaking
installation with an intrinsically closed wire 1 with an upper run 11 and a
lower run
12, which is guided over a plurality of guided drums or deflection drums 13
and
which is moved in the direction of the arrows A. At the start of the upper run
11 of
the wire 1, a device 14 is provided by means of which paper stock is sprayed
onto
the upper run 11 of the wire 1 over the width of the latter. The upper run 11
of the
wire 1 is guided over a plurality of differently constructed suction boxes 2,
which are
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formed with foils or wire boards and which are used to extract the water in
the
paper stock or to wipe off the water on the underside of the wire 1 and to
support
the wire 1.
[0033] In the further course of the movement of the wire 1, the latter is
assigned
a second intrinsically closed wire la located above it, which is guided over
deflection drums 13a and which is assigned a suction box 2a likewise formed
with
foils. In that area in which the lower, first wire 1 is assigned the upper,
second wire
la, the paper stock applied to the wire 1 is located between the two wires 1
and la,
and the water in the paper stock is extracted through the suction boxes 2 and
2a
assigned to said wires.
[0034] At the end of the upper run 11, the strip of paper 15 located on the
wire 1
is detached from the latter and, if appropriate, processed further in a felt
system.
[0035] The construction of the supporting elements, in particular the foils
and the
wire boards, is explained below:
[0036] Fig. 2 and Fig. 2A illustrate a foil 3 which has a supporting bar 31
which,
on its underside, is formed with an undercut groove 30, by means of which, in
a
wire system according to Fig. 1 and Fig. 1A, it can be pushed onto a
supporting bar
fixed to the frame such that the foil 3 extends at right angles to the
direction of
movement A of the wire 1.
[0037] On the side facing the wire 1, the foil 3 is formed with a metallic
carrier
layer 32 for a wear protection layer 33, with which the wire 2 comes into
contact.
On the side facing away from the wear protection layer 33, the metallic
carrier layer
32 is formed with bolts 34 which are welded or screwed to the carrier layer
32,
project into recesses 35 which are provided in the supporting bar 31 and which
are
anchored in the recesses 35 by means of a plastic compound 36 containing glass
fibers.
[0038] The carrier layer 32 is composed of a corrosion- and acid-resistant
stainless steel alloy. The wear protection layer 33 is composed of a hard
metallic
alloy, in which hard materials are embedded. The wear protection layer 33 is
joined
to the metallic carrier layer 32 by being sintered on.
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[0039] As can be seen from Fig. 2A, the metallic carrier layer 32 on which
the
wear protection layer 33 is located extends over part of the length of the
foil 3, at
least one further metallic carrier layer 32 having a wear protection layer 33
adjoining said foil 3 and, furthermore, the carrier layers 32 lying on one
another
being joined to each other by means of a welding strip 37. By means of this
welding strip 37, the two carrier layers 32 are drawn so firmly against each
other
that the wear protection layers 33 arranged on the latter adjoin one another
virtually
without any joint.
[0040] The embodiment of a foil 3 shown in Fig. 3 and Fig. 3A has virtually
the
same construction as the foil 3 shown in Fig. 2 and Fig. 2A. These two foils 3
differ
from each other only in the fact that the two carrier layers 32 abutting each
other
are not welded directly to each other, but that a joining plate 38 covering
the
abutting surfaces is provided, which is joined to the two carrier layers 32 in
each
case by means of a welding strip 37. By means of these two welding strips 37,
the
two wear protection layers 33 are also drawn against each other such that they
merge into each other virtually without any joint.
[0041] The foils 3 shown in Fig. 4, Fig. 4A, Fig. 4B, Fig. 4C, Fig. 4D and
Fig. 4E
have all the supporting bars 31, on which carrier layers 32 which are provided
with
wear layers 33 are fixed, the wear protection layers 33 being composed of hard
metallic alloys in which hard materials are embedded, and the wear protection
layers 33 being joined metallurgically to the carrier layers 32 by being
sintered on.
[0042] The foils 3 according to Fig. 4 to Fig. 4E differ from the foils 3
according
to Fig. 2, Fig. 2A and Fig. 3, Fig. 3A only by way of different formations of
the
supporting bars 31, by means of which they are fixed to supporting bars fixed
to the
frame, and by way of different types of fixing the carrier layers 32 to the
supporting
bars 31.
[0043] In the foil according to Fig. 4, the fixing bolts 34a are formed on
their
circumferential surfaces with annular recesses, into which the plastic
material 36
located in the recesses 35 penetrates, which reinforces the fixing of the
bolts 34a.
[0044] In the foil 3 according to Fig. 4A, the supporting bar 31 is formed
with a
rib 30a, which has lateral undercuts and with which it can be pushed into a
groove
of complementary cross section aligned transversely with respect to the wire
in a
supporting frame and can be clamped in this groove.
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[0045] In the foil 3 according to Fig. 4B, the supporting strip 31 is
formed with a
triangular cross section.
[0046] In the foil 3 according to Fig. 4C, the carrier layer 32 is
formed with an
undercut groove 32a on the side facing away from the wear layer 33, the
supporting
bar 31 is formed with a rib 31 approximately complementary in cross section to
the
groove 32a, and an adhesive material 39 is introduced into the interspace.
[0047] In the foil 3 according to Fig. 4D, the carrier layer 32 is
provided on the
side facing away from the wear protection layer 33 with two undercut grooves
32a,
which are assigned two ribs 31a of complementary cross section projecting from
the supporting bar 31.
[0048] In the foil 3 according to Fig. 4E, the carrier layer 32 is
provided on the
side facing away from the wear protection layer 33 with a projecting rib 32b
which
has lateral undercuts, and the supporting bar 31 is formed with an undercut
groove
31b.
[0049] In the foils according to Fig. 4C, Fig. 4D and Fig. 4E, in each
case
adhesive materials 39 are introduced between the undercut ribs 31a, 32b and
the
undercut grooves 31b, 32a.
[0050] In the foil 3 according to Fig. 5, bolts 34b provided with a
thread are
welded onto the carrier layer 32 and pass through drilled holes 40 located in
the
supporting bar 31, and nuts 40a are screwed onto the bolts 34b.
[0051] In the foil 3 according to Fig. 5A, the carrier layer 32 is
formed with
threaded holes 41 and the supporting bar 31 is formed with drilled holes 42,
through which machine screws 43 pass and are screwed into the threaded holes
41, by which means the carrier layer 32 is fixed to the supporting bar 31.
[0052] The foil 3 according to Fig. 5B is formed with a width enlarged
substantially as compared with the foil 3 according to Fig. 5, it being formed
over its
width with a plurality of bolts 34b welded to the carrier layer 32, which pass
through
drilled holes 40 provided in the supporting bar 31 and are screwed by means of
nuts 40a.
[0053] In the foil according to Fig. 6, the metallic carrier layer 32
is fixed to the
supporting bar 31 by means of lateral welding strips 44.
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[0054] In the foil 3 according to Fig. 6A, the supporting bar 31 is formed
with
drilled holes 40, within which there are annular welding strips 44a, by means
of
which the carrier layer 32 is fixed to the supporting bar 31.
[0055] The foil 3 according to Fig. 6B differs from the foil 3 according
to Fig. 6A
in that it has a substantially greater width and in that the supporting bar 31
is
formed over its width with two drilled holes 40, in which there are annular
welding
strips 44a. In addition, the supporting bar 31 is formed with a trapezoidal
cross
section wherein it can be pushed into a groove formed with a complementary
cross
section in a supporting bar of the supporting frame and locked in this groove.
[0056] The foil 3 according to Fig. 7 differs from all the foils
illustrated and
explained above in the fact that the carrier layer 32 for the wear protection
layer 33
is used only for direct fixing to a supporting frame of the wire system. For
this
purpose, the carrier layer 32 is formed with an undercut groove 32a, by means
of
which it can be pushed onto a supporting bar of complementary cross section
fixed
to the frame and belonging to a supporting frame and can be fixed to the
latter.
[0057] The supporting element 3a according to Fig. 8 and Fig. 8A, which is
formed as a wire board, is formed by a metallic carrier layer 32 which, on its
side
facing the wire or felt, is provided with a wear protection layer 33, which is
composed of a hard metallic alloy with embedded hard materials, the carrier
layer
32 and the wear protection layer 33 being formed with a large number of
drilled
holes 45. Welded to the carrier layer 32a on the side facing away from the
wear
protection layer 33 are bolts 34b provided with a screw thread, which pass
through
drilled holes 51 located in a support 50 fixed to the frame. Here, the fixing
of this
wire board 3a to the support 50 fixed to the frame is carried out by means of
nuts
40a screwed onto the bolts 34b. The direction of movement of the wire is
indicated
by the arrow A.
[0058] In the supporting element 3a according to Fig. 8B, which is
likewise
formed as a wire board having a multiplicity of drilled holes 45, the carrier
layer 32
is joined to a support 50 fixed to the frame by means of welding strips 44.
[0059] In the supporting element 3a according to Fig. 8C, which is
likewise
formed as a wire board having a multiplicity of drilled holes 45, the metallic
carrier
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layer 32 is formed with threaded holes 41 for fixing to a support 50, fixed to
the
frame, by means of threaded screws.
[0060] On account of the formation of the supporting element as a metallic
carrier board 32, on which a wear protection layer 33 of a hard metallic alloy
with
embedded hard materials is located, said carrier board 32 is sufficiently
elastic that
it can be curved in the direction of movement of the wire, as is illustrated
in Fig. 8B
and Fig. 80.
[0061] By using Fig. 9, firstly two suction boxes 21 and 22 which are
assigned to
the upper run 11 of the first wire 1 and over which the upper run 11 of the
wire 1 is
guided and supported, and, secondly, the suction box 2a assigned to the second
wire la are explained in more detail. The suction box 21 is formed with a
plurality
of foils 3 aligned transversely with respect to the direction of movement of
the wire
1, over which plurality of foils 3 the wire 1 is guided and is supported
thereby.
Likewise, the suction box 2a assigned to the second wire la is formed on its
underside with a plurality of foils 3, over which the second wire la is guided
and is
supported thereby. The last foils 3 of the upper suction box 2a in the
direction of
movement A of the two wires 1 and 1a are arranged and formed in such a way
that
the two wires 1 and la are guided on a slightly curved movement path. As a
result
of a movement path curved in this way, an improvement in the suction action
and in
the quality of the strip of paper is achieved. In order to divert into a
horizontal
movement path again in the course of this movement path, the second suction
box
22 is formed on its side facing the wire 1 with a wire board 3a which,
according to
Fig. 8B and Fig. 80, has a curved surface.
[0062] A wire board having a curved surface with a wear protection layer of a
hard metallic alloy in which hard materials are embedded, and which is
sintered
onto a supporting layer of a stainless steel metal, can be manufactured
substantially more easily than is true of wear protection layers which are
manufactured from a ceramic material.
[0063] The supporting element 3b illustrated in Fig. 10 and Fig. 10A
comprises a
supporting frame 6 which, on the side facing the wire or felt, is formed with
a
plurality of foils 61 which are aligned transversely with respect to the
direction of
movement A of the wire or felt and which each comprise a carrier layer 32 of a
stainless steel alloy and a wear protection layer 33 of a hard metallic alloy
with
embedded hard materials sintered onto said carrier layer.
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[0064] In all the exemplary embodiments explained above, the carrier layer 32
is
preferably composed of a corrosion- and acid-resistant stainless steel alloy,
preferably having a material quality WS 1.4571 (AISI 316 Ti) or WS 1.4404
(AISI
316L), and the wear protection layer 33 is composed of a hard metallic alloy
in
which hard materials are embedded, the wear protection layer 33 being joined
metallurgically to the carrier layer 32 by being sintered on.
[0065] The hard metallic alloy 33 can be composed of a nickel-based hard alloy
or can contain a nickel-based hard alloy. Furthermore, the hard metallic alloy
can
be composed of a mixture comprising an iron-based hard alloy and a nickel-
based
hard alloy, of a nickel-molybdenum-based hard alloy, and of a mixture of an
iron-
based hard alloy and a nickel-molybdenum hard alloy.
[0066] The wear protection layer can have a thickness of 1.5 mm to 10 mm.
The wear protection layer is joined to the metallic carrier layer by means of
sintering
under vacuum or under a protective atmosphere.
[0067] The hard materials located in the hard metal alloy can be formed by
chromium carbides, tungsten carbides, silicon carbides and boron carbides, on
their
own or in any desired mixtures. The hard materials in the hard metal alloy can
make up 50% by weight to 90% by weight.
[0068] The hard metal alloy can contain characteristic hard materials with
hardnesses of 600 HV0.3 to 900 HV0.3 or special hard materials with hardnesses
of
1200 HV0.3 to 1900 HVO 3.
[0069] Since wear protection layers according to the invention have relatively
high thicknesses, the supporting elements exhibit long service lives.
Furthermore,
as a result of sintering the wear protection layer onto the metallic carrier
material,
optimal joining of the wear protection layer to the metallic carrier layer is
effected.
[0070] The sintering of the wear protection layer 33 onto the carrier layer 32
is
carried out at a temperature from 870 C to 1300 C. In this regard, it is
pointed out
that the melting point of a corrosion- and acid-resistant stainless steel
alloy with a
material quality of 1.4571 (AISI 316 Ti) or 1.4404 (AISI 316L) lies at around
1400 C.
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