Note: Descriptions are shown in the official language in which they were submitted.
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Multi-layer gasket and its use
The present invention relates to a multi-layer gas-
ket, in particular to a multi-layer gasket with two
or more metallic layers. Such gaskets are especially
used as flat gaskets, for example in an internal com-
bustion engine, in the exhaust line of an internal
combustion engine or also in a fuel cell. Such gas-
kets can for instance be cylinder head gaskets or ex-
haust manifold gaskets.
According to the state of the art, such multi-layer
gaskets often comprise sealing beads, which seal the
openings to be sealed, such as combustion chamber
openings, water holes, oil holes or bolt holes. These
beads are usually accompanied by a deformation lim-
iter, also referred to as stopper, which possesses a
higher stiffness than the bead itself. As a conse-
quence, when compressed between the parts to be
sealed, the deformation limiter prevents the bead
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from complete compression. Therefore, the bead re-
mains in its elastic range and can therefore follow
the movements of the sealing gaps because of its re-
silient properties.
However, one should not underestimate the demand in
space required for such a combination of bead and de-
formation limiter. Especially in the sealing area of
the combustion openings, the space available is very
limited, which leads to the use of bead-stopper com-
binations with complicated constructions.
This is due to the fact that besides the sealing
properties of such sealing constructions, it is not
only the demand in space that is of high importance,
but also that the sealing construction provides a
long-term durability. Further, such sealing construc-
tions shall be flexibly applicable under the most
varied conditions.
Therefore, it is the object of the present invention,
to provide a gasket and its use, which gasket re-
quires only limited space, is flexibly applicable,
cost-efficient in its production, and reproducibly
provides for a long-term durability as well as for an
excellent sealing.
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In accordance with an embodiment of the present invention there is
provided a multi-layer gasket comprising: a first metallic layer, a
second metallic layer adjacent to the first layer, which layers both
extend essentially over the area of the complete gasket, and a
further metallic layer, and optionally further layers, wherein the
first layer, the second layer and the further metallic layer each
have at least a first passage opening, which first passage openings
are arranged on and immediately opposite to each other. A sealing
bead is arranged in each of the first layer and in the further
metallic layer around the at least one first passage opening at
least in sections or completely surrounding the passage opening.
The sealing bead in the further layer is configured symmetrically
relative to the sealing bead in the first metallic layer. A
profiling in the second layer is arranged on and immediately opposite
to the beads and surrounds the first passage opening at least in
sections. A plane of the second layer extends transversely to the
circumferential direction of the profiling and relative to the
thickness of the second layer in its areas adjoining laterally to
the profiling and pointing towards the outer edge of the gasket
layer, in the center of the second layer. The
profiling is
transverse to the circumferential direction showing a wave-shaped
or trapezoidal cross section consisting of crests and troughs and
having at least one period. Only part of the crests and troughs
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extend on one side out of the plane of the second layer. For
at least one, several or all of the wave crests and/or the wave
troughs, a first tangent to the profiling touching essentially
in the middle of a wave crest or wave trough and a second tangent
touching the profiling essentially centrally between the wave
crest and its neighbouring wave trough or between the wave trough
and its neighbouring wave crest define an angle a between 0 and
900. Along at least one cross section through the second layer,
the crests and troughs protrude beyond alternating sides of the
plane of the layer.
The gasket according to one embodiment the invention comprises
at least two metallic layers, which both extend essentially or
completely over the complete area of the gasket. If necessary,
further layers may be present
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and can be designed in various ways.
The at least two metallic layers each comprise at
least one first passage opening, which in the adja-
cent layers are adjacent to each other. Examples for
such passage openings comprise combustion chamber
openings in cylinder head gaskets, water or oil
holes, bolt holes in cylinder head gaskets or in
other gaskets or exhaust gas passage openings in gas-
kets of the exhaust line of a combustion engine.
This first passage opening in the first one of the at
least two metallic layers is encircled by a sealing
bead. Encircling does not necessarily mean that the
sealing bead individually encloses this particular
passage opening. Rather, it may enclose several pas-
sage openings simultaneously without passing along
the complete edge of each passage opening.
In the adjacent second layer, a profiling is arranged
adjoining to this sealing bead in the first layer.
This profiling increases the thickness in the area of
the sealing bead and therefore increases the compres-
sion of the sealing bead.
In contrast to the ordinary state of the art, this
profiling is not arranged alongside the sealing bead
within the plane of the layer, but opposite to the
sealing bead in the adjacent layer. This means that
the profiling at least partially comes to lie on or
within the bead. Doing so, the profiling does not
need to be arranged symmetrically to the bead; in-
stead their radial extension may be different. It is
further possible that the profiling extends into the
neighbourhood or until the circumferential edge of
the first passage opening.
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This profiling also encircles the first passage open-
ing at least in sections and in a direction trans-
verse to this circumferential direction may show dif-
ferent cross-sections. These cross-sections may also
change along the circumferential direction.
The second layer defines a plane of a layer, which is
determined by those areas of the second layer, which
extend transversely to the circumferential direction,
i.e. parallel to a plane which is spaned by the usu-
ally plane circumference of the passage opening, and
each of which is situated immediately adjacent to the
profiling in the second layer on both sides of the
profiling or which continue the layer radially out-
side the profiling adjacent to the profiling. Thus,
the plane of the layer extends transversely to the
circumferential direction of the profiling and at
half the height of the second layer in the area men-
tioned. The profiling can extend from this plane in
one or both directions.
The profiling according to the invention in a direc-
tion transverse to the circumferential direction
around the first passage opening shows a cross-
section which at least in sections is wave-shaped or
trapezoidal with at least one period of a wave, pref-
erable more than a period of a wave. Here, a period
is defined analogously to a sine wave as 360 . A pe-
riod thus consists in a sequence of a wave crest and
a wave trough until the beginning of the next wave
crest. This way, the cross-section comprises at least
one wave crest and one wave trough. It is however
preferred that it shows at least two wave crests and
two wave troughs. In this context, trapezoidal cross-
sections are to be understood in such a way that each
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wave crest and each wave trough shows an essentially
trapezoidal cross-section.
The trapezoidal or wave-shaped profiling here is how-
5 ever no rectangular stopper. Considering on the one
hand a tangent to the wave crest - or to a wave
trough - which touches either a tangent in the plane
of the layer or the plane of the layer itself and on
the other hand a tangent to the layer touching in the
flank between a wave crest and a neighbouring wave
trough - or between a wave trough and its neighbour-
ing wave crest - either in the middle of the flank or
at the position with maximum slope of the flank,
these tangents do not define an orthogonal angle - as
would be the case for a rectangular stopper - but an
angle a with 0 < a < 900
.
This means that the profiling according to the inven-
tion extends in a flattened manner and is no rectan-
gular stopper. This provides for an improved elastic
behaviour of the stopper.
With a sine-shaped cross-section of the profiling,
the angle a is preferably 45 a 72
õ especially
preferably 48 a 68 . With a
trapezoidal cross-
section of the profiling, the angle a is preferably
60 5 a 80 õ
especially preferably 65 5 a 5 750
.
With a trapezoidal cross-section, the tangent to the
layer in the flank corresponds to a prolongation of
the flank itself. These preferred ranges of angles
provide for an essentially easy closing and opening
of the halves of the tool during embossment, which
reduces wear and guarantees for an outstanding dura-
bility of the tools. In addition, a high stiffness of
the profiling is achieved with a small demand in
space.
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According to the invention, the crests and troughs
are arranged in such a manner that only part of them
is situated on one side outside the plane of the
layer. The profiling is thus formed in such a way
that it is not completely situated on a single side
outside the plane of the second layer. It needs to be
stressed that the most extreme points of the respec-
tive crests and troughs need to be considered, not
the neutral fibre. The relevant point defining
whether a crest or trough fulfils this condition is
the maximum point on the surface pointing away from
the centre of the structure.
A full bead usually comprises only one crest or one
trough and therefore already in this is different
from the profiling which comprises at least one pe-
riod, thus one crest and one trough. Further the two
elements are different in that the length of a period
for the profiling is less than the four-fold of the
material thickness of the profiled layer, while the
bead from foot to foot is broader than the four-fold
of the material thickness of the beaded layer. This
also influences the resilient properties of the two
elements. Considering the two layers separately, the
displacement of a profiled layer of a new, not yet
installed gasket under a load with 500 N/mm is less
than 40 pm, whereas the bead in a separately consid-
ered layer under the same conditions makes a dis-
placement of at least 80 pm, with the values speci-
fied relating to the load section of the correspond-
ing load deflection curves.
According to the invention, the sealing bead and the
opposite, pressure-increasing profiling are situated
in two different metallic layers of the gasket, which
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essentially extend over the area of the complete gas-
ket. The area of the complete gasket is of course to
be understood as the extension in the plane while
leaving out openings and passages. The sealing bead
and the profiling thus are formed in ordinary gasket
layers. It is thus not necessary to provide for a
particular, length-reduced beaded layer or profiled
layer, which facilitates the production of the gas-
ket. It shall be stressed that at least all fastening
holes pass through both the beaded layer and the pro-
filed layer. This makes it possible to produce the
sealing construction proposed in a simple and cost-
efficient manner.
The sealing construction according to the invention
can also be realized in such gaskets which comprise
elastomeric or rubber-based sealing elements, which
are often applied as lip-shaped profiles, e.g. by on-
top or edge moulding. It is preferred that these lip-
shaped profiles are applied in a symmetric manner,
which means that an application at the central gasket
layer is preferred. This central gasket layer may of
course also be a beaded or profiled layer.
With the lip-shaped profiles, it is preferred to pro-
vide for a recess in one or both layers adjoining to
the layer with the applied sealing profile. The re-
cess is provided in the area adjoining to the profile
and preferably also in the areas immediately border-
ing to these areas, for instance over an area corre-
sponding to the five-fold width of the applied pro-
filing. As an alternative, in case the applied pro-
filing extends along the outer edge of the gasket,
the adjoining layer(s) terminate immediately before
the beginning of the applied profile, at the most at
a distance which corresponds to the double width of
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the profile. Thus, the adjoining layers have a re-
duced extension.
As the sealing bead and the profiling are arranged
immediately one lying on the other, it is extremely
efficient with respect to its demand of space. The
sealing construction according to the invention in a
cylinder head gasket for example only requires a
width of 1.5 to 2.5 mm when a sealing bead thickened
according to the invention with the profiling is ar-
ranged between different combustion chambers. Never-
theless, with an abundance in space, broader con-
structions are possible as well.
This makes it possible that the sealing construction
according to the invention is only slightly sensitive
against a shift of the central line of the profiling
relative to the central line of the bead. In general,
it is admissible with the sealing construction ac-
cording to the invention, that the central line of
the profiling is shifted relative to the central line
of the bead by more than 0.3 mm. In some cases even
more than 0.5 mm are acceptable. In the same way, it
is not necessary that the central lines run in paral-
,
lel or in case of a shift as outlined above, concen-
tric to each other. The shift may also change along
the course of the bead or the profiling, respec-
tively. It is most recommended that at least three
linear contacts extend between the two feet of the
bead.
While with the bead-stopper sealing constructions of
the state of the art both the bead and the stopper
are distanced to the passage opening, the sealing
construction according to the invention makes it pos-
sible that the profiling extends until the edge of
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the passage opening. It is thus prolonged. This is
especially advantageous, as the profiling provides
the respective metal sheet with a higher stiffness
compared to a smooth metal sheet and the section af-
fected therefore has much less tendency to flutter.
This embodiment is often combined with a concentric,
but shifted arrangement of the central lines of the
bead and the profiling.
A shift of the central lines of bead and profiling
can also result from a prolongation of the profiling
relative to the outer edge of the bead. The increased
number of transversely extending structures improves
the sealing behaviour towards coolants and/or lubri-
cants.
The sealing construction according to the invention
shows an extraordinary durability and allows to be
flexibly adapted to the most varied of sealing geome-
tries and types of gaskets.
As a coating is possible but not mandatory, the pro-
duction process is dominated by the embossment of the
sealing beads and the profiling, which allows for a
cost-efficient production. Nevertheless, an excellent
sealing function and a high reproducibility of the
production are guaranteed.
According to the invention, the crests and troughs do
not all extend on one side of the plane of the second
layer. In contrast, it is advantageous if the two
wave troughs following on a wave crest protruding on
one side of the plane (and vice versa) return at
least into the plane of the layer or exceed beyond
that towards the side of the plane of the layer oppo-
site to the wave crest. In this context, it is advan-
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tageous if all wave crests protrude towards one side
of the layer of the plane in the same degree. In the
same way it is advantageous if all wave troughs on
one side of the layer protrude to the same degree
5 relative to the plane of the layer or relative to the
wave crests. The degree of protrusion of the wave
crests on the one hand and of the wave troughs on the
other hand relative to the plane of the layer does
however not need to be identical.
A symmetric arrangement with the wave crests and wave
troughs protruding to different sides of the plane of
the layer is especially advantageous; with this em-
bodiment it is also possible that the respective pro-
trusions have the same dimensions towards both sides.
Further, it is advantageous if in a profiling which
comprises several periods of a wave, a plurality,
thus at least two, consecutive periods protrude with
the same dimension or at least with essentially the
same dimension from the plane of the layer.
In, other embodiments, it can be advantageous if the
wave crests and troughs following one on the other
along the cross section of the wave, have different
constitution, e.g. if the amplitude along the cross
section first increases and then decreases.
The cross section of the profiling according to the
invention may comprise trapezoidal and/or wave-shaped
areas. This means that it may both comprises purely
or essentially trapezoidal or purely or essentially
sinus-shaped sections. Further, it may comprise sec-
tions with a shape being an intermediate form between
trapezoidal and sinusoidal. These respective cross-
sectional geometries may extend continuously and
along the whole course of the profiling. In case of a
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profiling encircling a passage opening, the wave
crests and troughs preferably extend continuously in
a concentric manner with essentially uniform dis-
tances. The wave-shaped or trapezoidal cross sections
may however also only be given in sections. It is
even possible that along the course of the profiling,
the cross sections of various sections are offset
relative to each other. In the last case, a cup- or
dimple-shaped structure may arise as the profiling
according to the invention.
Such a dimple-shaped profiling is for instance known
from EP 1298365 A2. Thus, dimple-shaped profilings in
the sense of the present invention shall also com-
prise the dimple-shaped structures in the sense of EP
1298365 A2, the disclosure of which is taken over
into this description by reference to EP 1298365 A2.
A wave-shaped or trapezoidal profiling is for in-
stance known from WO 01/96768 Al and WO 2008/012363
Al. Thus, wave-shaped or trapezoidal profilings in
the sense of the present invention shall also com-
prise the wave-shaped or trapezoidal structures in
the sense of WO 01/96768 Al and WO 2008/012363 Al,
the disclosure of which is taken over into this de-
scription by reference to WO 01/96768 Al and
WO 2008/012363 Al.
In a further essentially advantageous embodiment of
the invention, the transition sections between wave
crests and wave troughs are tapered with respect to
the thickness of the adjoining wave crests and wave
troughs. The thickness of the transition regions,
also referred to as flanks, is advantageously reduced
by 5 to 50 %, more advantageously by 10 to 40 %, and
most advantageously by 10 to 30 % relative to the
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thickness of the profiling in the area of the wave
crests and wave troughs.
In other advantageous embodiments, the profiling pos-
sesses such a width that it extends within the area
of the bead, thus between the foot points of the
sealing bead. The cross section of the profiling is
thus less broad or at least equally broad than the
width of the sealing bead, which is defined by the
distance between the two foot points of the sealing
bead. In advantageous embodiments, the width of the
profiling, measured between the foot points of the
profiling in the cross section is 30
%, more advan-
tageously 50 %, but advantageously also 100
% of
the width of the sealing bead, thus broader than the
width of the sealing bead measured in the cross sec-
tion between the foot points of the sealing bead. In
other embodiments, the width of the profiling may be
restricted to 200 % of the width of the sealing
bead. The foot points of the profiling and the seal-
ing bead for the measurement of the width of the re-
spective elements can be measured in the uninstalled
state, thus before the gasket is installed for the
first time, or in the de-installed state after in-
stallation and compression.
Stainless steels as well as non-hardened and hardened
carbon steels have shown to be advantageous materials
for the first and/or second layer. Hardening here can
take place before or after forming of the profiling.
For a large amount of applications, spring steel pro-
vides particular advantages. The layers further can
be coated one-sided or double-sided, in areas or over
a whole surface, in order to improve the sealing
properties of the sealing construction. In this con-
text it is especially advantageous if at least the
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area of the beads and/or of the profilings are
coated. The coating does usually extend over the feet
of the respective structure, at least by half a width
of the bead or profiling, respectively. Coating mate-
rials which are particularly advantageous comprise a
thermoset binder or several thermoset binders, as
they improve the micro sealing.
In the following some examples of gaskets according
to the invention are further described. The same or
similar reference numbers are used for identical or
similar elements, which means that their description
is not always repeated.
All characteristics shown in the following examples
are advantageous for the present invention and can be
combined with each other, even if they have to be
taken out of the context of the respective examples.
It is shown in
Figures
1 and 3 a gasket according to the invention;
Figures 2,
4 and 5 a further gasket according to the inven-
tion;
Figures
6 to 13 further gaskets according to the inven-
tion in cross section which allows to
demonstrate the sealing construction ac-
cording to the invention.
Figure 1 shows a gasket 1 from its bottom side, the
gasket 1 comprises two combustion chamber passage
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openings 5a and 5b. The gasket further comprises bolt
holes 30.
Sealing constructions are arranged around the respec-
tive combustion chamber openings 5a and 5b, which in
figure 3 are represented in cross section. The com-
bustion chamber openings 5a and 5b here are sur-
rounded by profilings 7a, 7b and sealing beads 6
resting on them, with the sealing beads not being
visible in figure 1. They provide for a reliable
sealing of the combustion chambers 5a and 5b.
Figure 2 shows a cylinder head gasket 1; here the
lower layer 3 is visible. This second layer 3 here
shows combustion gas or combustion chamber openings
5a, 5b and 5c, which are encircled by sealing beads -
not shown in Figure 2 - and profilings 7a, 7b and 7c,
respectively. The design of the sealing structures in
the narrow bridge areas immediately between the com-
bustion chamber openings is often crucial. Here, for
demonstration purposes, the bridge are between com-
bustion chamber openings 5a and 5b (left side) is de-
signed differently than the bridge area between open-
ings 5b and 5c (right side). The same is true for the
transition areas of the sealing structures linking
the bridge areas with the sealing areas of the indi-
vidual combustion chamber openings. These different
designs are marked with circles in Figure 2. In the
example shown on the left side, the profiling 7a
shows a smoothed angle of about 20 to 30 and with
this angle passes into the profiling 7b, whereas a
straight section of the profiling passes through the
bridge section. In contrast, in the example depicted
on the right side, only half of the profiling 7b - to
be more precise half its width - continues into half
of the profiling 7c with a steep angle. These halves
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do not pass through the bridge region. The respective
other halves, thus the halves closer to the combus-
tion chamber passage openings 5b and 5c, respec-
tively, when entering the bridge section approach
5 each other steadily until they have passed half the
bridge length and then again move away from each
other.
Figure 3 shows a cross section of the two-layered
10 gasket of figure 1 along cross section A-A with a
first layer 2 and a second layer 3. The combustion
chamber opening is situated on the left side of the
section shown and is marked with reference number 5a.
15 Figure 3 further shows a tangent 20a to the wave
crest 11 at about a central position of the wave
crest as well as a tangent 20 parallel to the latter,
which is a tangent to the layer plane 9 or represents
the layer plane 9 itself. It further shows a tangent
21 to the flank between the wave crest 11 and the
wave trough 10. These tangents 20 and 21 define an
angle a. All figures 1 and 13 are only schematic
drawings, which do not represent the angles at scale.
The angle a in all embodiments of the profilings de-
picted is between 45 and 72 , in both cases includ-
ing the limits.
The first layer 2 comprises a plane of the layer 8
and a sealing bead 6, which encircles the combustion
chamber opening 5a. The sealing bead 6 comprises a
foot point 13a and a foot point 13b. The second layer
3 of the gasket comprises a wave-shaped profiling 7
with wave crests 10 and wave troughs 11. This profil-
ing at its foot points 14a and 14b continues into the
flat areas of the second layer 3. The plane of the
layer 9 of the second layer is defined by the foot
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points 14a and 14b and the adjacent areas of the
layer 3, which point away from the profiling 7. In
those cases, where the profiling 7 extends until the
edge of the passage opening 5a, the plane 9 of the
layer 3 is defined by the area adjoining to the outer
foot point 14b of the profiling circumferentially on
the outer side.
In figure 3, wave crests 10 and wave troughs 11 pro-
trude from the plane 9 of layer 3 into different di-
rections and with essentially identical height. The
width of the profiling 7 is larger than the width of
the bead 6 which is defined by the distance of the
foot points 13a and 13b. The profiling 7 extends im-
mediately adjacent to the bead 6 and in radial direc-
tion slightly protrudes to both sides of the foot
points 13a and 13b of the bead 6.
Figure 4 shows a cross section of the gasket in fig-
ure 2 along line B-B, with the first layer 1 being
arranged as the lower layer and the second layer 3
with the trapezoidal profilings 7a and 7b as the up-
per layer.
The profilings 7a and 7b again are arranged immedi-
ately opposite to the beads 6a and 6b in the first
layer. In this case, the width of the profilings 7a
and 7b is essentially the same as the width of the
beads 6a and 6b. The concave sides of the wave
troughs 11 are situated in the plane 9 of the layer,
whereas the convex sides of the wave crests 10 in an
asymmetrical matter protrude further beyond the plane
9 of the layer. In total, a one-sided profiling re-
sults, in which the peaks of the wave crests - on the
convex sides - are situated at the height of the sur-
face of layer 3.
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Figure 5 shows a further sealing construction. In
contrast to the foregoing example, where combustion
passage openings have been shown, the section given
here is adjacent to a coolant passage 50 in the back-
land of the gasket, close to the outer edge of the
gasket. In general, the backland especially comprises
the area, which when observed from the combustion gas
passage openings, is situated behind the bolt holes.
The section shown in figure 5 essentially corresponds
to section C-C in figure 2. While the bead 15 at the
coolant passage 50 has no thickening, the bead 6,
which runs in parallel to the outer edge of the gas-
ket is arranged opposite to a profiling 7 in the sec-
ond layer 3. The profiling 7 is configured in the
same way as the profilings 7a and 7b in figure 4.
Here, the profiling especially aims on support and
thickening.
Figure 6 represents a sealing construction, which
corresponds to the one from figure 3. However, here,
the first layer 2 as well as the second layer 3 is
coated on both surfaces with coatings 16a, 16b, 16c
and 16d.
Figure 7 again shows a sealing construction similar
to figure 3, which apart from the first layer - here
referred to as 2b and the second layer already known
shows a third layer, referred to as 2a. In the seal-
ing construction, this third layer 2a is arranged
symmetrically to layer 2b. Layers 2a and 2b on their
surface facing towards the second layer 3, have no
coating, but only on their surface which faces away
from layer 3, which means that in all cases, one
coating layer is given on the outer surfaces as well
as at all interfaces between layers. These coatings
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are referred to with reference numbers 16a, 16b, 16d
and 16d.
Figure 8 shows a further sealing construction compa-
rable to the one in figure 3, which again shows the
layers 2a and 3 already known from figure 7. Here,
layer 3 is coated with a coating 16b on only one of
its surfaces. The second layer 3 borders to a further
layer 17a with coatings 16c, 16d which layer 17a ad-
joins to a further layer 17b with a coating 16e. This
fourth layer 17b comprises a bead 15, which shows a
symmetric configuration relative to the bead in the
first layer 2a. To summarize, the embodiments of fig-
ures 7 and 8 are different from each other in that
they have a different distribution of the coatings on
the surfaces of the layers as well as by the addi-
tional unstructured metal sheet layer 17. This means
that the embodiment depicted in figure 8 is suited
for larger sealing gaps than the one in figure 7.
Figure 9 in a large section again shows a sealing
construction similar to figure 3, here however with a
bead 6 being broader than the profiling 7.
Figure 10 depicts a sealing construction comparable
to figure 3. However, here the profiling 7 is consid-
erably broader than the bead 6.
In figure 11 a sealing construction is shown with a
bead 6 in the first layer 2. The elements to be
sealed against each other are arranged on the top
surface of layer 3 and below the bottom surface of
layer 2 (not shown). The layer 2 on one of its sur-
faces is provided with a coating 16c. On the other
side of the layer 2, the second layer 3 is arranged,
which shows a profiling 7. This profiling is designed
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19
as described beforehand and shows the same width as
the bead 6. The wave crests and wave troughs on both
surfaces of the profiling 7 are completely filled
with coatings 16a and 16b. In this extremely sche-
matic representation, an improved sealing between the
elements to be sealed against each other is achieved
both with the coating 16b as well as with the coat-
ings 16a and 16c on the outer surfaces.
In figure 11, the tangents 20 and 21 as well as the
angle a are shown on the example of a profiling with
a trapezoidal cross section. In this case, the angle
a according to the invention ranges between 600 and
80 , including the limits of this range.
Figure 12 shows an especially preferred embodiment of
the profiling 7 in layer 3. This profiling shows a
wave-shaped cross section. This cross section com-
prises four wave crests 10a, 10b, 10c and 10d as well
as three wave troughs lla, llb and 11c situated be-
tween the wave crests. The profiling depicted in fig-
ure 12 thus shows more than three periods, to be more
precise almost four periods. The transition regions
between the wave crests and the wave troughs, here
referred to with reference numbers 12a, 12b, 12c,
12d, 12e, 12f and 12g are considerably tapered rela-
tive to the wave crests and wave troughs, namely by
about 30 %. This means that the local thickness of
the material measured orthogonally to the surfaces of
layer 3 in the area of the flanks is considerably
less than the corresponding thickness of the material
at the wave crests and wave troughs. This tapering of
the flanks causes an increase of the stiffness of the
profiling and in addition makes it possible to form a
larger number of waves - a larger number of periods -
with a given length between the foot points 14a and
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14b. The interaction of the above mentioned factors
causes an increased stiffening of the profiling,
which means that it can be designed with a considera-
bly larger stiffness than the adjoining bead to be
5 thickened. This means that the sealing construction
according to the invention in situations with little
space can provide for excellent sealing solutions at
low cost. The sealing construction can generally be
used in flat gaskets, for instance flat gaskets for
10 engine aggregates, exhaust lines, but especially for
cylinder head gaskets - in particular with little
abundance of space, in the case of cylinder head gas-
kets little space between the combustion chamber
openings.
Figure 12 further shows tangents 20a and 20b with 20a
being a tangent to a wave trough 11c and tangent 20b
being a tangent to a wave crest 10d, which both run
=
in parallel to the plane 9 of the layer. Together
with the tangents 21a and 21b to the flank 12f at
about the centre of the flank 12f, the tangents 20a
and 20b define an angle a, which according to the in-
vention is between 45 and 72 .
Figure 13 shows a further sealing construction compa-
rable to the one in figure 3. In this case, the wave-
shaped profiling 7 extends until the edge of the com-
bustion chamber passage opening 5. Figure 13 further
shows central lines 22 and 23 of the sealing bead 6
and the profiling 7, respectively. It is obvious that
these centre lines are set off relative to each
other. Nevertheless, the profiling 7 is arranged im-
mediately opposite to the bead 6. In this figure,
too, some of the tangents to the maxima of the wave
crests and to the minima of the wave troughs as well
as some of the tangents to the flanks between wave
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21
troughs and wave crests are given in order to indi-
cate angle a.
In general, almost all metallic gaskets can be de-
signed according to the invention. It is especially
recommended to design cylinder head gaskets with a
high demand of regular introduction of load according
to the invention. According to the invention, all
numbers of layers starting from at least two are pos-
sible. In the sealing construction according to the
invention, the beads are always in the main force
load. The use of the sealing construction according
to the invention both at the combustion gas passage
opening and in the backland of the gasket allows for
a variable adaptation of the thicknesses, which means
that a topographic distribution of the thicknesses
adapted to the respective engine is possible over the
range of the complete gasket.
All coating materials known as coatings for metallic
gaskets in the state of the art can be applied as the
coating for the structured layers, which comprise the
sealing bead ort he profiling.
The improvement of the micro sealing and/or of the
slide-friction coefficient can be achieved by these
coatings. In most cases the actual coating is applied
to an adhesive primer layer which in turn is situated
immediately on the surface of the metal sheet. Only
by way of example, coatings based on fluoropolymers,
such as for instance FPM (vinylidenefluoride-hexa-
fluoropropylene copolymere), silicone rubber or NBR
rubber (acryle-butadiene rubber), PUR (polyurethane),
NR (natural rubber), FFKM (perfluororubber), SBR
(styrole-butadiene rubber), BR (butyl rubber), FVSQ
(fluorosilicone), CSM (chlorosulfonated polyethylene)
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22
as well as silicone and epoxy rubbers shall be men-
tioned. For the application of these coating materi-
als, screen printing, curtain coating and spraying
are suited methods.
Apart from this, coatings based on polyester resins,
PEEK (polyetherketone), PFA and MFA (both being
fluoro polymers) as well as silica and epoxi resins
can be used. With these coating materials, powder
coating methods can be applied.
The invention with the profiling being arranged on
top or below the bead enables an excellent adhesion
of the coating and prevents from accidental flowing
of the coating out of the area of the bead. To
achieve this, the coatings are applied one-sided,
double-sided, on the complete area or only partially.
If necessary, it is possible to apply rubber-based
sealing elements in the gaskets according to the in-
vention.
