Note: Descriptions are shown in the official language in which they were submitted.
The present invention relates to a rail-like water-
removal element for the sieve or felt part of a wa-ter-remo~al ma-
chine, especially for paper-making machinery, such as a mesh
table, foil, couch roll, wet suction roll, suction roll, tube
suction roll, and suction felt, the layer of which that is in
sliding contact with the mesh or felt consisting of individual
segments of hard material, such as sistered aluminum oxide, and
silicon carbide, these segments having a shoulder on the side
remote from and opposite to the mesh, the individual segments
being secured to a rail by means of said shoulder, said rail
being adapted to be installed on the supporting structure of
the water-removal machine.
Rail-like water-removal elements for the mesh or felt
stage of a water-removal machine, built up from individual segments
made of hard material in combination with other materials are
known. The introduction of water-removal elements provided with
hard materials has the advantage of permitting high operating
speeds to be attained by present day water-removal machinery.
It is necessary to build up the water-removal elements from in-
dividual segments because bodies produced from hard materials cannot be produced in one piece having large-area configurations,
as can be done, for example, when using plastics. An important
disadvantage in building up segments is that the butt joints be-
tweet thy individual segments can damage the mesh and felt and
can cause defects, such as water stripes in the paper being pro-
duped, particularly if there are manufacturing tolerances between
the individual segments. This disadvantage can be eliminated when
the manufacturer grinds off a finished water-removal element.
Nevertheless, gaps can open up at the butt joints if the water-
removal elements are subjected to bending, torsion, and/or thermal expansion.
In order to avoid these disadvantages No. DEEPS 23 63 732
-- 1 --
I
discloses a water-removal device in which the wear-r~sis-tant sex-
mints of hard material, which have a shoulder or a trapezoidal
groove which extends in a longitudinal direction on their under-
sides, are secured by means of a molded mass in a U-shaped metal
rail. Taken together, the metal rail and the segments of hard
material form a structural element for the water-removal element,
said element extending across the whole width of the paper-making
machine. In order to compensate for thickness tolerances of the
different hard materials that are governed by manufacturing pro-
cusses, the contact surfaces of the segments on the U-shaped
metal rails must also be subjected to a costly grinding process.
Water-removal elements of such a bonded construction can rupture
at the butt joints between the segments of hard material if they
are bent or twisted about the longitudinal axis, because of the
elastic-plastic joint with the U-rails, and these ruptures can
lead to the aforesaid disadvantages. Also, stress loads can
occur in the bonded body as a result of differing thermal expand
soon in the metal rail and the segments of hard material.
DEEPS No. 21 10 564 discloses a water-removal device
in which the hard material segments that are let into a support
rail are pressed against each other by a clamping element. This
clamping clement consists of a rod and two movable jaws at the
ends of the rod. One disadvantage of such a structure is that if
the water-removal element is bent, compression forces can occur
at the butt joints between the individual hard material elements
and these can cause the hard material to rupture. In the same
way, if the water-rernoval element is twisted about the longitudinal
axis ruptures can occur at the butt joints between the individual
segments of hard material because of the slight twisting and
these can lead to the aforesaid mesh and felt damage. In addition,
in this structure the production of the individual hard material
segments demands the observance of extremely close tolerances
-- 2
and the greatest possible an~lclr precision when ye blowout joint surfaces
are machined, and this results in considerable costs for grinding
operations.
DEMOS No. 23 36 450 discloses a built-up ceramic come
potent as a water-removal element, this being under adequate pro-
run '3
ssure-pL~ go loading so that when the element is bent as
a result of bending forces or thermal changes, the resulting come
I press ion loads are absorbed on the inner side of the curve. One
disadvantage of this structure is that once again -there is a
requirement for costly and very precise machining of the individual
ceramic elements. Furthermore, it is impossible to achieve a con-
slant and adequate pressure-pretensioning loading by the tension
anchor because of the differing coefficients of thermal expansion
of ceramic and steel. The temperature span in the paper-making
machinery is between 20 and 85C. Thus, there is a danger -that
despite pretensioning the butt joints will rupture under bending
loads or that stress peaks that occur on the edges of the individual
ceramic elements can lead to rupturing in the pressure areas of the
butt joints. In addition, the structure contained in DEMOS No. 23
36 450 and DEEPS No. 21 10 564 require a hole in the ceramic sex-
mint and this leads to a weakening of this segment.
Thus, the present invention provides a rail-shaped water-
removal element for the mesh or felt part of a water-removal macho
ire, said water-removal element displaying no breaks, chipping or
gaps at the butt joints between the individual ceramic segments
under bending loads, longitudinal torsion, or thermal expansion,
which water-removal element can be adjusted to any length and fine-
ground, is simple to install, and safe and easy to manipulate.
In accordance with the present invention, there is pro-
voided a rail-shaped water-removal element for the mesh or felt
stage of a water-removal machine, in particular a paper-making
machine, such as a mesh table, foil, couch roll, wet suction roll,
suction roll, suction tube and suction felt, the layer of which
that is in slidln~ contact with the mesh or felt layer Wormed from
individual segments of hard Motorola such as sistered aluminum
oxide, and silicon carbide said individual segments having a
shoulder on the side furthest from the mesh or felt and being sea-
used to a rail that extends transversely to the direction of
movement of the mesh or felt and by said rail being adapted to
be installed on the supporting structure of the water-removal
machinery, said individual segments being cemented to each other
and having stepped jointing surfaces on their longitudinal side
ends which extend across the whole width of the segments.
The advantage of the present invention lies in the fact
that by joining the individual stepped jointing surfaces and sea
using them by cementing a structure which can be considered as
a self-supporting water-removal element from strength consider-
lions results and which, as such, can be handled safely. Since
the upper portion and the shoulder are of material that has the
same coefficient of expansion, with a bonded construction of this
kind no forces that could cause a change of shape or deformation,
especially at the stepped jointing surfaces, and subsequent fail-
use of the component, will result from thermal expansion in the event of temperature changes.
I've stepped jointing surfaces permit a positive and form-
locking cemented joint, this resulting in a considerable increase
in the area of the surfaces that are in contact as compared to
a simple butt joint, and this in its turn results in a reduction
in the specific surface loads that occur.
Since the critical shear strength of the cemented joint
is greater than the critical static strength of the selected
hard materials, i.e., ceramic substances, there will be no pies-
tic or elastic deformations and concomitant changes in shape of the rail-shaped water-removal element. Generally conventional
materials such as glues, solders, cements or low-melting point
mixtures of inorganic glass-forming non-water soluble compounds
can be used to produce the cemented joint, provided only that they
possess the required degree of strength.
In a preferred embodiment of the invention the stepped
jointing surfaces are perpendicular to the longitudinal axis of
the segment and in each instance form a right-angle with each
other.
In a particularly preferred embodiment of the present
invention, the segment of hard materials is not formed in one
piece and then ground, but is made up of a separately produced
upper portion and a shoulder, these being of equal length, the
upper portion being displaced one-half length in relation to the
shoulder, and then bonded to the shoulder by means of cement.
The upper portion and the shoulder may be made of the
same material having the same characteristics however, since no
demands with regard to grain size distribution, surface hardness,
pore volume, pore distribution, and grinding and polishing chafe-
cteristics are imposed on the shoulder, starting materials that
meet only the requirements for strength and coefficient of then-
met expansion can be used, whereas the upper portion, which is
in contact with the mesh or felt stages, should have as few pores
as possible, in order that no particles of filler can accumulate
in them, causing damage to the mesh or felt. Pores are, however,
desirable in the shoulder since they improve adhesion of the gem-
en. The shoulder can be produced, for example, from the waste
material that results from processing the uncured blanks for the
upper portion.
The jointing surfaces that are parallel to the longitu-
dial axis of the segment are to be identical to the neutral axis
of the overall cross-section, or they may be above the neutral
axis. If the jointing surface lies on the neutral axis, there
will be no compression, tensile or other stresses. If the jointing
surface is above the neutral axis, the cement layer will only be
subjected to compression forces. A high level of reliability is
Sly
thus guaranteed or the joint. Were the adhesion to be stressed
on forming, the reliability of the joint would only be a fraction
of that under shear stresses.
The present invention will be further illustrated by
way of the accompanying drawings in which:-
Figure 1 is a perspective view of a segment of hard material in accordance with one embodiment of the present invent
lion;
Figure 2 is a side elevation of a water-removal element
made up of segments of hard material of Figure 1, extending trays-
verse to the direction of movement of the machine,
Figure 3 is a side view of a second embodiment of a
water removal element, extending transverse to the direction of
movement of the machine;
Figure 4 is a cross-section on the plane of the line
V-V of Figure 3;
Figure 5 is a perspective view of a third embodiment
of a water-removal element; and
; Figure 6 is a cross-section of a water-removal element
with a profile rail and a supporting structure of the water-
removal machine.
Referring to the accompanying drawings, the one-piece
segment 1 of hard material shown in perspective in Figure 1 has
a shoulder 3 that is secured in a profile rail 9 shown in Figure
6. The shoulder 3 is offset longitudinally in relation to the
upper portion 2 of the segment 1, and is of a suitable trapezoidal
shape (Figure 1) or T-shape (Figure 4). A very secure union with
the supporting structure 10 shown in Figure 6 is provided by means
of the profile rail 9. The upper portion 2 of the segment 1 is in
direct con-tact with the sieve mesh or felt, the direction of the
sieve mesh or felt being indicated by the arrow 6. The cross-
section ox the upper portion 2 is shown as being rectangular. It
can, however, be of any shape. The stepped joint surfaces that are
formed in each instance from the surface that extend parallel
to the longitudinal axis of the secJment, and the surfaces 5 that
are, in each instance, perpendicular to the longitudinal axis of
the segment serve to ensure a shape- and force locking union with
the cement between adjacent segments 1.
Figure 2 shows a water-removal element composed of in-
dividual segments 1, transverse to the direction of movement of
the sieve mesh or felt. The stepped joint surfaces, formed from
the individual surfaces 4 and 5, are set very close together and
are bonded together by the cement layer 8.
Figure 3 shows a further embodiment of a water-removal
element, the two-part segment 1 consisting of an upper portion 2
and the shoulder 3, it being simple to produce and machine them.
The upper portion 2 and the shoulder 3 are of the same length
and are, in each instance, displaced by a half-length on their
joint surfaces that extend horizontally, parallel to the long-
tudinal axis and cemented firmly in position by the cement layer
8. Once again, the stepped joint surfaces between the individual
segments 1 are formed by the surfaces 4 and 5.
Figure 4 is a side view of a water removal element in
the plane of -the line IV-IV in Figure 3. The upper portion 2 is
shaped as a foil. The joint with the shoulder 3 is effected by
means of the cement layer 8. The shoulder 3 has a T-shaped cross-
section. The water-removal element is connected to the supporting
structure by means of the profile rail 9 shown in Figure 6.
Figure 5 is a perspective view of a third embodiment of
the water-removal element which, once again, is built up from two-
part individual segment 1. The direction of movement of the sieve
mesh is indicated by the arrow 6. The upper portion 2 is in the
form of a foil, this being wider than the shoulder 3. The shoulder
3 has a swallow-tail cross-section to provide a connection with
the profile rail (not shown). The strength of the shoulder 3 in
its vertical extension is greater than the strength of the upper
portion I The upper portion 2 is owe the same installed length as
the shoulder 3 and is displaced on the shoulder 3 by one-half its
length and secured by means of the cement layer 8.
Figure 6 is a vertical section through the water-removal
element installed on the supporting structure of a water-removal
machine. The contact surface 11 of the upper portion 2 touches the
sieve mesh or the felt, the direction of movement of which is in-
dilated by the arrow 6. The shoulder 3, which is secured by the
upper portion 2, is of trapezoidal cross-section, and engages in
the profile rail 9 that is made of plastic, glass-fibre reinforced
plastic or metal. In its turn, the profile rail 9 surrounds a T-
shaped metal rail 12 of the supporting structure 10 of the water-
removal machine. Only the shoulder 3 of the water-removal element
can move freely in the recess of the profile rail 9 transversely
to the direction of movement of the sieve mesh. In the same manner,
the profile rail 9 on the T-shaped metal rail 12 with the support
tying structure 10 can move freely only transversely to the direct
lion of movement 6 of -the sieve mesh. This arrangement means that
thermal expansion within the assembled structure is equalized by
sliding backlash with the result that no bending loads occur on
the water-removal element.
-- 8
