U.S. patent application number 14/130803 was filed with the patent office on 2014-05-22 for dirt-repellent cleaning scraper.
This patent application is currently assigned to VOITH PATENT GMBH. The applicant listed for this patent is Juergen Angerler, Alexander Etschmaier. Invention is credited to Juergen Angerler, Alexander Etschmaier.
Application Number | 20140137361 14/130803 |
Document ID | / |
Family ID | 46420231 |
Filed Date | 2014-05-22 |
United States Patent
Application |
20140137361 |
Kind Code |
A1 |
Etschmaier; Alexander ; et
al. |
May 22, 2014 |
DIRT-REPELLENT CLEANING SCRAPER
Abstract
A cleaning scraper for cleaning roller surfaces in paper
machines, wherein the cleaning scraper has a main element and a
coating covering at least part of the surface of the main element.
The coating is formed with a first coating layer and a second
coating layer arranged on the first coating layer. The second
coating layer is formed by a polymer.
Inventors: |
Etschmaier; Alexander;
(Neuberg, AT) ; Angerler; Juergen; (Steyrermuehl,
AT) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Etschmaier; Alexander
Angerler; Juergen |
Neuberg
Steyrermuehl |
|
AT
AT |
|
|
Assignee: |
VOITH PATENT GMBH
HEIDENHEIM
DE
|
Family ID: |
46420231 |
Appl. No.: |
14/130803 |
Filed: |
July 4, 2012 |
PCT Filed: |
July 4, 2012 |
PCT NO: |
PCT/EP2012/062993 |
371 Date: |
January 3, 2014 |
Current U.S.
Class: |
15/256.52 |
Current CPC
Class: |
D21G 3/00 20130101; D21G
3/005 20130101 |
Class at
Publication: |
15/256.52 |
International
Class: |
D21G 3/00 20060101
D21G003/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 6, 2011 |
DE |
10 2011 078 745.3 |
Claims
1-14. (canceled)
15. A cleaning scraper for cleaning roller surfaces in paper
machines, the cleaning scraper comprising: a main element with a
surface; a coating covering at least a portion of said surface of
said main element, said coating including a first coating layer and
a second coating layer formed of a polymer disposed on said first
coating layer.
16. The cleaning scraper according to claim 15, wherein said
polymer comprises an epoxy resin.
17. The cleaning scraper according to claim 15, wherein said
polymer comprises a silicone-polyester resin.
18. The cleaning scraper according to claim 15, which comprises
fillers embedded in said polymer.
19. The cleaning scraper according to claim 18, wherein said
fillers contain polyfluoroethylene.
20. The cleaning scraper according to claim 18, wherein said
fillers contain polytetrafluoroethylene.
21. The cleaning scraper according to claim 18, wherein said
fillers are present in the form of particles.
22. The cleaning scraper according to claim 21, wherein said
particles have average diameters in a range from 0.1 to 5
.mu.m.
23. The cleaning scraper according to claim 15, wherein said
polymer comprises polyfluoroethylene.
24. The cleaning scraper according to claim 15, wherein said
polymer comprises polytetrafluoroethylene.
25. The cleaning scraper according to claim 15, wherein said
polymer comprises a silicone.
26. The cleaning scraper according to claim 15, wherein a material
of said first coating layer comprises hard metal.
27. The cleaning scraper according to claim 26, wherein said hard
metal contains 8 to 10% of cobalt and tungsten monocarbide.
28. The cleaning scraper according to claim 15, wherein a material
of said first coating layer comprises an oxide ceramic.
29. The cleaning scraper according to claim 28, wherein said oxide
ceramic is selected from the group consisting of aluminum oxide,
zirconium oxide, magnesium oxide, chromium(III) oxide, yttrium
oxide and the titanates.
30. The cleaning scraper according to claim 25, wherein said first
coating layer has a surface roughness in a range from 5 to 8
.mu.m.
31. The cleaning scraper according to claim 30, wherein said first
coating layer has a surface roughness in a range from 6 to 7
.mu.m.
32. The cleaning scraper according to claim 26, wherein said first
coating layer has a surface roughness in a range from 5 to 8
.mu.m.
33. The cleaning scraper according to claim 32, wherein said first
coating layer has a surface roughness in a range from 6 to 7
.mu.m.
34. The cleaning scraper according to claim 15, which comprises a
bonding layer formed on a surface region of said main element that
adjoins said first coating layer.
Description
[0001] The invention relates to scraper blades for machines for
paper production and relates in particular to the design of
cleaning scrapers for cleaning roller surfaces in paper
production.
[0002] Cleaning scrapers are used in paper machines for cleaning
the surfaces of rollers. Cleaning of a roller surface is effected
by detaching the contaminants by means of one or more cleaning
scraper blades pressing against the surface of the respective
coating of the roller. The contaminants, which are usually formed
by paper residues, paper fibers and particles, lead to local
stressing peaks at the blades, so that cleaning scrapers are
usually made of steel or under corrosive use conditions of
stainless steel and have a cemented hard material coating at the
region provided for contact with the roller in order to achieve a
higher operating life or running time.
[0003] To produce the cemented hard material coating, it is
possible to use a conventional cemented carbide powder comprising,
for example, 8-10% of cobalt and tungsten monocarbide as hard
material. Coating is preferably carried out using thermal spraying
techniques, with the coating material frequently being applied in a
plurality of passes in order to achieve a very homogeneous, in
terms of its composition and physical properties, cemented hard
material coating. Each of the passes applies a thin layer of
coating material to the substrate material of the blade or to the
last coating layer applied thereto. Application of the coating in a
plurality of thin layers ensures that the components of the coating
material cannot demix during buildup of the coating. When the
coating parameters are observed, a macroscopically homogeneous
coating can be produced because of the chemical and physical
identity of the individual layers.
[0004] However, the coating surface has a certain ability to adhere
to the contaminants detached from the roller coating, as a result
of which the particles of dirt are removed with increasingly poorer
effectiveness by the cleaning scraper and the cleaning action of
the cleaning scraper becomes impaired over time.
[0005] It is therefore desirable to provide a cleaning scraper
which has an improved long-term cleaning action.
[0006] In one embodiment, such a cleaning scraper for cleaning
roller surfaces in paper machines has a main element and a coating
covering at least part of the surface of the main element. The
coating here comprises a first metallic coating layer and a second
coating layer arranged on the first coating layer, with the second
coating layer being formed by a polymer.
[0007] A cleaning scraper according to this embodiment presses with
the second coating layer formed by a polymer against the respective
roller surface. Since the adhesion of contaminants to the polymer
is lower than to the metallic coating layer, improved removal of
the contaminants detached from the roller surface and thus improved
quality of cleaning are achieved. Apart from this dirt-repellent
action, the cleaning scraper has improved sliding properties at the
contact surface to the roller, as a result of which the forces
acting on the coating are reduced and the operating life of the
cleaning scraper is thus increased.
[0008] It may be pointed out that the terms such as "comprise",
"have", "include", "contain" and "with" used in this description
and the claims for listing features and also their grammatical
derivatives, should generally be interpreted as nonexhaustive
listing of features, e.g. components, process steps, devices,
ranges, sizes and the like, and in no way exclude the presence of
other or additional features or groups of other or additional
features.
[0009] In embodiments, the polymer comprises an epoxy resin since
in the uncross linked or partially cross linked state this readily
wets the metallic first coating material and thus adheres well to
the latter. In further embodiments, the polymer advantageously
comprises a silicone-polyester resin since this combines an
excellent dirt-repellent action with very good antiadhesion and
sliding properties. To improve the dirt-repellent action and also
the sliding properties of the coating surface, fillers can be
embedded in the polymer; in preferred embodiments, the fillers
contain polyfluoroethylene (PFE) and in particular
polytetrafluoroethylene (PTFE). In advantageous embodiments, the
fillers are present in the form of particles and in particular in
the form of particles having average diameters in the range from
0.1 to 5 .mu.m. Instead of an epoxy resin or silicone-polyester
resin having fillers comprising PFE or PTFE, the polymer can also
be formed directly by polyfluoroethylene and in particular
polytetrafluoroethylene or by a polymer which comprises such a
material.
[0010] The material of the first coating layer comprises, in
embodiments, a cemented hard material which combines good
mechanical strength with high abrasion resistance and can be
applied effectively and economically to the main element of the
cleaning scraper by means of modern thermal spraying processes. In
embodiments, the cemented hard material preferably comprises from 8
to 10% of cobalt and contains tungsten monocarbide as hard
material. Other embodiments have a first coating layer whose
material comprises an oxide ceramic. The oxide ceramic or oxide
ceramics of the first coating layer are preferably selected here
from among aluminum oxide, zirconium oxide, magnesium oxide,
chromium(III) oxide, yttrium oxide and titanates.
[0011] To achieve an adhesive bond between first coating layer and
second coating layer, the first coating layer preferably has a
surface roughness at the boundary to the second coating layer in
the range from 5 to 8 .mu.m and in particular in the range from 6
to 7 .mu.m. In further embodiments, a bonding layer is arranged on
the surface region of the main element which adjoins the first
coating layer so as to improve the adhesion of the first coating
layer to the main element. The layer thickness of the first coating
layer is preferably in the range from about 50 to 100 .mu.m, while
the second coating layer preferably has a thickness in the range
from about 20 to 80 .mu.m.
[0012] Further features of the invention can be derived from the
following description of examples in conjunction with the claims
and the accompanying figure. It may be pointed out the invention is
not restricted to the embodiments of the examples described but is
determined by the scope of the accompanying claims. In particular,
in embodiments according to the invention, the features indicated
in the examples described below can be realized in numbers and
combinations deviating from the examples.
[0013] In the following description of some examples of the
invention, reference is made to the accompanying FIG. 1 which shows
a schematic cross section through a cleaning scraper in the region
of its facet.
[0014] The schematic depiction in FIG. 1 shows a cross section
through the front region of a cleaning scraper 10 provided with a
coating, where this front region is provided for contact with a
roller surface. The cleaning scraper blade 10 has a main element
11, which can be made, for example, of steel, preferably of
stainless steel, and a coating built up of a first coating layer 12
and a second coating layer 13 arranged thereon. At the interface to
the first coating layer 12, the main element 11 can, as illustrated
in the figure, have a bonding layer 14. The coating occupies at
least part of the cleaning scraper 10 which comes into contact with
the roller surface of the paper machine. The cleaning scraper 10
also has a chamfer, which is generally referred to as facet, in the
front region provided for contact with a roller surface. In
general, the coating covers the main element 11 in the region of
the facet, as shown in the figure.
[0015] As can be seen from the schematic detail A of the coating in
the region of the facet, the coating has two coating layers 12 and
13, with the first coating layer 12 arranged on the main element
preferably being formed by a metallic material which advantageously
consists of a cemented hard material or comprises such a material.
The material of the second coating layer 13 arranged on the first
coating layer 12 is a polymer.
[0016] In preferred embodiments, a thermal spraying process is used
for producing the first coating layer 12. Spray coating is
preferably effected in a plurality of passes, for example from 10
to 100 passes. Each pass produces a thin sublayer of the coating
material, with the first sub layer being sprayed directly on the
surface of the main element 11 or any bonding layer 14 previously
applied thereto and further sublayers being sprayed onto the sub
layer previously applied in each case. The physical homogeneity of
the first coating layer 12 can be adjusted via the parameters of
the process used. In the spraying process designated by the acronym
HVOF (high velocity oxygen fuel), it is possible, for example, to
avoid the formation of pores in the sublayers by selection of a
suitable ratio of fuel to oxygen and a suitable transport rate of
the powder material used for layer formation.
[0017] As material for forming the first coating layer, it is
possible to use commercial cemented carbide powders comprising
about 8-10% of cobalt and tungsten monocarbide as hard material.
The cemented hard material powder is preferably applied in such a
way that a surface roughness of the first coating layer 12 in the
range from about 5 to 8 .mu.m and in particular in the range from 6
to 7 .mu.m is obtained. The coating is preferably applied to only
part of the main element and, in preferred embodiments, covers an
about 20 mm wide region which adjoins the front edge of the
cleaning scraper and covers the facet.
[0018] In principle, ceramic materials such as aluminum oxide,
zirconium dioxide, magnesium oxide, chromium(III) oxide, yttrium
oxide and titanates can also be used instead of metallic materials
for forming the first coating layer. These too can be applied by
means of thermal spraying processes to the main element of the
cleaning scraper blade 10. Adhesion of ceramic coatings to the main
element 11 is usually ensured in the case of steel substrates by
use of a bonding layer whose material can, for example, be selected
from among aluminum, nickel, chromium or alloys such as AlNi or
NiCr.
[0019] After application of the first coating layer 12, a polymer
is applied as second coating layer 13 to the surface thereof. The
polymer fills the depressions formed by the surface roughness of
the first coating layer 12, as a result of which a physical locking
of the two coating layers is obtained in addition to an adhesive
bond.
[0020] Suitable polymers are thermo sets and thermoplastics, which
can be produced on the basis of one-component and two-component
systems. Thermo sets whose decomposition temperature is so far
above the use temperature of the second coating layer 13 that the
thermo set behaves elastically are particularly suitable. In an
analogous way, thermoplastics whose glass transition temperature is
so far above the use temperature of the second coating layer 13
that no troublesome softening of the polymer can occur during use
of the polymer-coated cleaning scraper 10 are suitable. A rough
guideline value for the minimum difference between use temperature
and decomposition or glass transition temperature is 20.degree. C.
Use temperature is understood as meaning the operating temperature
of the second coating layer 13 during correct use of the cleaning
scraper blade 10.
[0021] Suitable polymers are, in particular, epoxy resins and epoxy
resins comprising filler particles, for example particles of a
polyfluoroethylene (PFE) and in particular of
polytetrafluoroethylene (PTFE), embedded therein. Since epoxy resin
in the uncross linked or partially cross linked state displays good
wetting of the first coating layer 12, it has good adhesion
thereto.
[0022] The viscosity of the epoxy resin can be reduced by addition
of solvents, for example alcohols or ketones, in order, for
example, to make spraying-on of the polymer possible. In the case
of relatively high viscosities, application of the polymer by means
of painting tools such as brushes or blades is preferred. When a
dipping bath is used, coating of the surface of the first coating
layer can also be carried out by dipping into a still liquid
polymer.
[0023] In a preferred embodiment, a mixture of epoxy resin and
isobutanol containing PTFE particles having average diameters of
from 0.1 to 5 .mu.m is used as polymer starting material. The
proportions of the epoxy resin in the polymer starting material are
in the range from 40 to 70% by weight, those of the isobutanol are
in the range from 10 to 60% by weight and those of the PTFE
particles are in the range from 2 to 20% by weight. The
polymer/solvent mixture is preferably sprayed onto the first
coating layer.
[0024] Another preferred embodiment differs from that described
above in the choice of the polymer starting material, using a
silicone-polyester resin mixed with isobutanol and containing PTFE
particles having average sizes of from 0.1 to 5 .mu.m. The
proportions of the silicone-polyester resin in the polymer starting
material are once again in the range from 40 to 70% by weight,
those of the isobutanol are in the range from 10 to 60% by weight
and those of the PTFE particles are in the range from 2 to 20% by
weight. The polymer/solvent mixture is preferably sprayed onto the
first coating layer.
[0025] After application of the polymer based material to the first
coating layer 12, it is preferably thermally cross linked, which
concludes the formation of the polymeric second coating layer
13.
[0026] Instead of or in combination with the above-described
polymer materials, it is also possible to use silicones for forming
the second coating layer 13. Polymer starting materials having a
low viscosity are preferably used for forming comparatively thin
second coating layers, for example for thicknesses of from 20 to
about 50 .mu.m, while polymer starting materials having a
relatively high viscosity are used for correspondingly thicker
second coating layers of, for example, up to 80 .mu.m.
[0027] The polymeric surface of the cleaning scraper coating
reduces the adhesion of dirt on the cleaning scraper, so that this
dirt can be more easily removed from the cleaning scraper blade 10
and does not accumulate there. This significantly improves the
cleaning action of the cleaning scraper 10 compared to conventional
designs. Since the polymeric surface also reduces the friction
against the roller surface, the improved cleaning action is also
retained over a longer period of time. Furthermore, owing to the
different optical properties of first and second coating layers,
damage to the coating or an end to the running time of the cleaning
scraper characterized by wear of the second coating layer can be
recognized more easily and more quickly than in the case of
conventional cleaning scrapers.
* * * * *