U.S. patent application number 09/207947 was filed with the patent office on 2002-02-07 for method and device for the manufacture of dimensionally stable, liquid impermeable, flexible pressbands, especially for shoepresses of paper making machines.
Invention is credited to SCHON, WERNER.
Application Number | 20020016115 09/207947 |
Document ID | / |
Family ID | 7851266 |
Filed Date | 2002-02-07 |
United States Patent
Application |
20020016115 |
Kind Code |
A1 |
SCHON, WERNER |
February 7, 2002 |
METHOD AND DEVICE FOR THE MANUFACTURE OF DIMENSIONALLY STABLE,
LIQUID IMPERMEABLE, FLEXIBLE PRESSBANDS, ESPECIALLY FOR SHOEPRESSES
OF PAPER MAKING MACHINES
Abstract
The invention relates to a method of and a device for the
manufacture of dimensionally stable, liquid-impermeable, flexible,
elastic pressbands, particularly for use with broad-nip shoepresses
of paper making machines. The method comprising pouring a flowable
mixture of a prepolymer onto a substrate moved by a distance
maintaining device over a cylindrical mandrel and maintained during
this movement in an adjustable distance from the surface of said
mandrel, and being coated during this movement by a coating device
with a flowable prepolymer, wherein during this coating of the
substrate threads or wires are laid down onto the substrate in the
direction of rotation of the mandrel and are coated with the
polymer substance. In order to provide a method of the initially
specified kind in such a way that the manufactured pressbands have
the required high strength and tensile stability and that they are
able to maintain both over long times of operation, the invention
proposes that a net, texture, knitted fabric or a similar structure
is used as substrate tensioned over the surface of the mandrel and
consisting of non-woven threads located transverse to the
longitudinal direction of the pressband and forming meshs the width
thereof is chosen dependent especially on the viscosity of the
prepolymer mass such that the meshs are completely impregnated by
the prepolymer mass poured onto the meshs and that the threads of
the net, texture, knitted fabric or similar structure are
completely coated by the meshs forming on the side opposite to the
surface of the mandrel a closed, smooth surface of prepolymer
material, the thickness of which corresponds to the distance of the
substrate from the surface of the mandrel, which polymer material
can be separated from that mandrel surface.
Inventors: |
SCHON, WERNER; (HEIDENHEIM,
DE) |
Correspondence
Address: |
WARE FRESSOLA VAN DER SLUYS &
ADOLPHSON, LLP
BRADFORD GREEN BUILDING 5
755 MAIN STREET, P O BOX 224
MONROE
CT
06468
US
|
Family ID: |
7851266 |
Appl. No.: |
09/207947 |
Filed: |
December 9, 1998 |
Current U.S.
Class: |
442/50 ;
428/297.7; 428/36.1; 428/36.3; 428/36.4 |
Current CPC
Class: |
Y10T 428/1369 20150115;
B29C 70/32 20130101; Y10S 162/904 20130101; D21F 3/0236 20130101;
Y10S 162/902 20130101; Y10T 442/198 20150401; Y10T 442/184
20150401; Y10T 428/249941 20150401; Y10S 162/903 20130101; Y10S
162/901 20130101; Y10T 428/1362 20150115; B29C 53/8075 20130101;
Y10S 162/90 20130101; D21F 3/0227 20130101; Y10T 428/1372
20150115 |
Class at
Publication: |
442/50 ;
428/36.1; 428/36.3; 428/36.4; 428/297.7 |
International
Class: |
B32B 027/12; B32B
027/04; B32B 001/08 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 9, 1997 |
DE |
197 54 631.5 |
Claims
1. Method for the manufacture of dimensionally stable,
liquid-impermeable, flexible, elastic pressbands, particularly for
use with broad-nip shoepresses of paper making machines, comprising
pouring a flowable mixture of a prepolymer onto a substrate moved
by a distance maintaining device over a cylindrical mandrel and
maintained during this movement in an adjustable distance from the
surface of said mandrel and being coated during this movement by a
coating device with a flowable prepolymer, wherein during this
coating of the substrate threads or wires are laid down onto the
substrate in the direction of rotation of the mandrel and are
coated with the polymer substance, characterized by providing a
net, texture, knitted fabric or similar structure as substrate
tensioned over the surface of the mandrel and consisting of
non-woven threads located transverse with the longitudinal
direction of the pressband and forming meshs the width thereof is
chosen dependent particularly on the viscosity of the prepolymer
mass such that the meshs are completely impregnated by the
prepolymer mass poured onto the meshs and that the threads of the
net, texture, knitted fabric or a similar structure are completely
coated by the mass forming on the side opposite to the surface of
the mandrel a closed, smooth surface of prepolymer material, the
thickness of which corresponds to the distance of the substrate
from the surface of the mandrel, which polymer material can be
separated from said mandrel surface.
2. Method according to claim 1, characterized in that the substrate
will be drawn prior to its coating in form of an elastic tube over
the surface of the mandrel and will be maintained under tension in
a distance from said surface.
3. Method according to claim 1, characterized in that the mandrel
is used in connection with a tensioning device, wherein the
substrate is secured at both frontfaces of the mandrel and is
maintained under tension over the surface of the mandrel.
4. Method according to claim 1, characterized in that the distance
of the substrate from the surface of the mandrel is maintained by
means of a distance keeping device which is shiftable axially over
the surface of the mandrel.
5. Method according to claim 1, characterized in that the width of
the meshs of the substrate is between 2 and 8 mm and is chosen such
that the prepolymer mass which is to be poured onto the substrate
passes the meshs and is disposed on the surface of the mandrel.
6. Method according to claim 1, characterized in that the threads
are wound onto the substrate in a helically configured manner and
thus under an angle transverse to the longitudinal direction of the
pressband.
7. Method according to claim 1, characterized in that the threads
are multifile threads of plastic material.
8. Method according to claim 1, characterized in that the the
threads are monofile threads of plastic material.
9. Method according to claim 1, characterized in that the threads
are provided of a material of high tensile strength as for instance
polyamid, polyester and also Keflar.RTM. or Dyneema.RTM..
10. Method according to claim 1, characterized in that after curing
the prepolymer material on the surface of the mandrel the obtained
pressband is mechanically treated with a lathe-tool for obtaining
the required thickness, surface condition and surface
structure.
11. Method according to claim 10, characterized in that the surface
structure of the pressband is particularly configurated by the
provision of blind bores, ridges or grooves for dewatering
purposes.
12. Method according to claim 10, characterized in that after the
pressband has been treated mechanically it will be withdrawn from
the mandrel by a drawing device.
13. Device for the manufacture of dimensionally stable,
liquid-impermeable, flexible pressbands according to claim 1,
characterized by a cylindrical mandrel provided with a surface
plated with chromium or extremely polished, at each frontface of
which a tension annulus is positioned on the shaft of the mandrel
keeping the tube-like substrate under tension and rotating together
with the mandrel or its shaft, respectively, wherein the one
tension annulus is axially fixed on the shaft and the other tension
annulus is axially shiftible keeping the substrate over the surface
of the mandrel during its coating with the prepolymer material
under tension in a distance from said surface defined by tension
annulus which is also axially shiftable.
14. Dimensionally stable, liquid-impermeable, flexible pressband
particularly for the use in connection with shoepresses of paper
making machines, characterized in that the pressband is
manufactured of a tube-like substrate consisting of a net, texture,
knitted fabric or a similar structure the threads thereof are not
interwoven and form in longitudinal direction and cross direction
of the pressband extendable meshs which are completely covered by a
prepolymer mass spread onto the substrate in such a way that the
coated substrate is provided with a prepolymer layer also on that
surface opposite to the press shoe, the structure being such that
the other surface of the substrate which is not opposite to the
press shoe is provided with at least one monofile or multifile
thread embedded into the coating material and helically wound.
15. Pressband according to claim 14, characterized in that the
substrate consists of several superimposed layers of a net,
texture, knitted fabric or similar structure the threads of which
are forming meshs provided of not interwoven threads.
Description
BACKGROUND OF THE INVENTION
[0001] The invention relates to a method of and device for the
manufacture of dimensionally stable, liquid-impermeable, flexible,
elastic pressbands, particularly for use with broad-nip shoepresses
of paper making machines, said method comprising pouring a flowable
mixture of a prepolymer onto a substrate moved by a distance
maintaining device over a cylindrical mandrel and maintained during
this movement in an adjustable distance from the surface of said
mandrel and being coated during this movement by a coating device
with a flowable prepolymer, wherein during this coating of the
substrate threads or wires are laid down onto the substrate in the
direction of rotation of the mandrel and are coated with the
polymer substance.
[0002] Such method is known from the German published patent
application DE 40 22 800. The pressbands and presscoats for wet
presses manufactured by this known method, are disadvantageous,
however, because of the fact that the longitudinal threads and
cross threads embedded in the coating material are slowly released
from the coating material under the pressure forces and tensional
forces created within the press band during operation of such a wet
press, if the tensile modules of threads, adhesion promoters and
coating material had not been precisely checked up to one another
previously. Such a check up, however, is rather difficult.
Moreover, the tensile modules are changing because of ageing. As a
consequence thereof the so-called excavating or tunneling effect
arises according to which the threads are providing around them
hollow spaces because of the alternating tensions affecting them.
This effect, however, essentially decreases the strength of the
band substantially and thus also its lifetime or durability and
destroys in this connection especially the original tensile
strength of the band.
[0003] Moreover, pressbands manufactured according to the known
method are often destroyed during operation in case the paper web
is drawn into the nip together with waste material causing a local
breaking of the pressband below the shoe, whereas the elastic felt
web proceeds on the non-breaked areas of the pressband. That is the
reason why the pressband is generally so strongly deformed in the
range of failure that it breaks in cross-direction as soon as the
deformation forces cannot be taken over by the pressband.
SUMMARY OF THE PRESENT INVENTION
[0004] It is therefore an object underlying the invention to
provide a method of the initially specified kind in such a way that
the manufactured pressbands have the required high strength and
tensile stability and that they are able to maintain both over very
long times of operation.
[0005] It is a further object of the invention to improve the
method of manufacturing insofar as the pressbands remain rather
unaffected in case of local deformations of such pressbands caused
by waste material in the nip of the shoepress.
[0006] It is still a further object of the invention to provide a
device which is designed in such a way as to permit a highly
economic and therefore inexpensive performing of said method and in
this connection also an improved pressband should be
manufactured.
[0007] These and other objects are accomplished according to one
aspect of the invention by providing a net, texture, knitted fabric
or a similar structure as substrate tensioned over the surface of
the mandrel and consisting of non-woven threads located transverse
to the longitudinal direction of the pressband and forming meshs
the width thereof is chosen dependent especially on the viscosity
of the prepolymer mass such that the meshs are completely
impregnated by the prepolymer mass poured onto the meshs and that
the threads of the net, texture, knitted fabric or a similar
structure are completely coated by the mass forming on the side
opposite to the surface of the mandrel a closed, smooth surface of
prepolymer material, the thickness of which corresponds to the
distance of the substrate from the surface of the mandrel, which
polymer material can be separated from said mandrel surface.
[0008] By that positioning of the net, texture, knitted fabric or a
similar structure within the pressband in relation to the running
direction of the pressband, as well as by the fact that the threads
those nets, textures, knitted fabrics or similar structures are
consisting of are connected to one another but not interwoven with
one another, the flexibility or elasticity of the pressband on
operation is improved essentially so that a tension profile is
formed which avoids the creation of tension peaks and which is in
contrast to the tension profile of the common pressbands more
uniform and more homogenous and in addition to that it is on a
lower level. As a consequence the crossthreads and longitudinal
threads of the substrate which are with respect to the direction of
running of the pressband no more positioned in parallel or
rectangularly but in general diagonally are not released even after
a long running time from the coating mass, for instance
polyurethane, surrounding them but remain in a fixed position
within the coating mass so that formation of breakes within the
pressbands are completely avoided even if there will be troubles
because of waste material.
[0009] There are many advantageous embodiments of the subject
invention which are dealt with in the subclaims. According to one
advantageous embodiment the substrate is configured as a tube and
is fixed in a tensioning device at both front sides of the mandrel
and is axially tensioned by a stretching device, the construction
being such that the substrate is held during the coating operation
in the required distance from the surface of the mandrel by a
distance annulus.
[0010] In accordance with an advantageous further improvement of
the invention multifile threads are used for helically winding the
threads onto the substrate during coating of the same by casting
the prepolymer onto the surface of the substrate resulting in
obtaining the required strength of the pressband in circumferential
direction thereof.
[0011] According to a further advantageous feature of the subject
invention the threads of which the substrate is provided, i.e. the
net, texture, knitted fabric or similar structure, can be multifile
threads of plastic material in order to obtain the required
tensional stability of the pressband.
[0012] After the casting of the prepolymer material and its couring
on the surface of the mandrel the obtained pressband can be
advantageously mechanically treated to obtain the required
thickness and/or quality of the surface before the pressband will
be withdrawn from the surface of the mandrel. In this connection it
has been found further advantageous to provide the surface of the
pressband also with holes and/or depressions for the removal of
liquid.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] The invention will be described below with reference to the
embodiments thereof as illustrated in the drawings. In the
drawings:
[0014] FIG. 1 is a schematic, perspective view onto a mandrel over
which a substrate in form of a tube-like net consisting of threads
is tensioned, which substrate is coated with a prepolymer on
feeding threads thereto,
[0015] FIG. 2 is a schematic longitudinal sectional view of a
mandrel device provided with front side tension annulus for the
substrate which is to be coated and to be wound,
[0016] FIGS. 3 and 4 are schematical views onto net-like structures
which can be used as substrate and which consist of monofile and/or
multifile threads, and
[0017] FIG. 5 is a schematic view onto the mesh of a net-like
structure of the kind as shown in FIGS. 3 and 4 in different
conditions of longitudinal and cross-tension appearing in the
tube-like web, texture or knitted fabric elastically stretched over
the surface of the mandrel.
[0018] The mandrel 1 as shown in FIG. 1 in form of a cylindrical
roll is used in connection with further elements of the device as
shown in FIG. 2 for the manufacture of dimensionally stable,
liquid-impermeable, flexible, elastic pressbands, particularly for
use with broad-nip shoepresses of paper making machines. Such kind
of pressbands which are at least provided on their outer side
opposite to the fibrous web or the felt or felts, respectively,
with cavities and/or depressions for liquid drainage, are
manufactured as follows. A flowable mixture of a prepolymer is
poured or cast onto a substrate 10 by means of a not shown jet as
well as coating device. The substrate is maintained by means of a
distance device in form of a distance annulus 11 as shown in FIG. 2
in a distance from the cylindrical surface 2 of the mandrel, which
distance can be adjusted by that distance annulus. The substrate 10
is configured as a net 13 (as shown in FIGS. 3 and 4) or a not
shown shown texture, web or knitted fabric or a similar
configuration consisting of monofile or multifile threads 7 of
plastic material. Prior to that coating operation the substrate 10
is provided with monofile or multifile threads 15 which are layed
down onto the substrate 10 in direction of rotation A of the
mandrel 1 in a helically configurated manner. Thereafter, these
threads 15 are coated with polymer 14. The substrate is spanned
like a diaphragm over the surface of the mandrel 1 and its threads
7 extend transverse or diagonal to the longitudinal direction of
the pressband.
[0019] Thus, net 13 consists of a multiplicity of meshs 16 provided
by the threads 7 which meshs, however, are no woven meshs, i.e.
they are not provided with warp threads and weft threads. The width
of the mesh is exspecially chosen dependent on the viscosity of the
prepolymer mass such that the meshs are completely impregnated by
the prepolymer mass and the threads are completely coated by that
mass. In this way on the surface 2 of the side of the mandrel
opposite or adjacent to the substrate 10 a completely closed,
smooth surface layer of prepolymer material is provided the
thickness of that layer corresponds to the distance given by the
distance annulus 11. The width of the mesh amounts advantageously
to 4 to 6 mm. As material for the threads 7 of the substrate
polyamid and polyester as well as Keflar.RTM. and Dyneema.RTM. have
found to be essentially advantageous, the last one because of its
high tensile strength. The required elastic stretching of the
substrate is obtained by the kind of joining the threads 7 which is
shown for instance in FIGS. 3 and 4 as well as in FIG. 5 at a
mesh.
[0020] After the prepolymer material is cured on the surface of the
mandrel the such manufactured pressband is brought to the required
thickness by a mechanical treatment, for instance by means of a
lathe-tool so that the required quality of the surface will be
created. Thereafter, the pressband which can also be provided on
its surface with blind bores, ridges or grooves in order to fulfill
its future function of dewatering of fiber webs or felts,
respectively of paper making machines, will be withdrawn from the
mandrel by a drawing device.
[0021] As shown in FIG. 2, at both front faces 8, 9 of the mandrel
a tension annulus 5, 6 is located on the mandrel 1 supporting shaft
3. These two tension annulus 5, 6 keep the tube-like substrate 10
under extended condition in a required distance from the surface 2
adjusted by the distance annulus 11. For that purpose the annulus 5
on the shaft 3 supported by the bearings 4 is axially movable as
shown by the double arrow C, whereas the other tension annulus 6 is
axially fixed on the shaft 3. The distance annulus 11 is drawn by a
drawing device 17 in the direction of the arrow D so that this
annulus moves forwardly in the same extent as the coating mass is
axially proceeding which is laid down on the substrate by a not
shown jet.
[0022] The threads 15 which are to be wound onto the substrate
extent under an angle transverse to the longitudinal direction of
the pressband and are thus also wound on the substrate in a
spiral-like manner. These threads 15 can be of plastic material
like the threads 7 forming the meshs 16 of the net 13, texture or
knitted fabric multifile threads.
[0023] By this method of the manufacture of pressbands by means of
a net, texture, knitted fabric or a comparable structure forming a
substrate the threads of which extent transverse or diagonal,
respectively to the running direction of the pressband and thus
transfers to the longitudinal axes 18 of the mandrel, the tensile
strength and stretching stability of the pressbands are essentially
improved with respect to the common method according to which
instead of such a substrate threads are embedded into the coating
mass running parallel and in longitudinal direction of the
pressband. Because of the spiral-like winding of the threads during
the coating according to the subject invention the required
stability of the pressband in circumferential direction is
obtained. Therefore, the durability or lifetime of such kind of
pressbands is extended essentially, because the generation of
tension peaks during operation of the pressband is avoided. Thus,
the tension profile in the cross-section of the pressband is more
uniform and on a lower level. This is the reason why the threads of
plastic material within the coating mass remain much longer in
their original position as in known pressbands. Moreover, the
pressband according to the subject invention is much less sensitive
with respect to waste particles which can be drawn into the nip so
that the pressband does not break in contrast to the known
pressband.
* * * * *