Reinforced support sheet and method for making same

A reinforced support sheet or plate, especially for making flat gaskets or heat dampening plates is made of a sheet or plate-like support material which is covered with a vulcanizable soft material layer which contains a fiber-like and, if need be, powder-like binder material. The support material is smooth and the soft layer material is composed predominantly of a powder-like, asbestos-free mineral base material. A method for making such a sheet or plate is also disclosed.

The present invention relates to a reinforced support sheet or plate, 
especially suitable for making flat gaskets, as well as heat dampening 
plates. More particularly, it relates to such a sheet or plate having a 
sheet or plate-like support material which is covered with a vulcanizable, 
soft material which contains fiber-like and, if need be, powder-like base 
materials, as well as a binder material. 
A reinforced support sheet of the aforementioned type is disclosed in 
German Auslegeschrift (DE-AS) No. 21 46 309. The subject matter of the 
aforementioned reference is, in particular, a method for making such a 
reinforced support material. Therein, a dough-like, fiber-reinforced 
elastomer mixture (as the soft material) is applied by means of calender 
rollers, with the aid of additional water, onto a metallic support 
material. The additional water is required so as to avoid an adhering of 
the dough-like material onto the calender rollers. The dough-like soft 
material consists of a rubber-asbestos mixture in a ratio of about 1:1. 
As previously indicated, reinforced sheets of the aforementioned type may 
be used as a base material for making flat gaskets which are subjected to 
high mechanical and thermal stresses, for example, cylinder head gaskets 
in combustion engines. In such sealing systems, which are subjected to 
high dynamic stresses, the following characteristics of the gaskets 
employed are important: 
(a) adaptability; 
(b) pressure resistance; 
(c) spring back resilience 
(d) gas and liquid tightness; 
(e) temperature resistance; 
(f) longitudinal and transverse stability; 
(g) hardness of the cutting edges; and 
(h) corrosion resistance. 
In this respect, the reinforced support sheets or the flat gaskets made out 
of these sheets in accordance with the known method of DE-AS No. 21 46 309 
have substantial disadvantages. The required dough-like base condition of 
the soft material requires a high rubber content of the same. On account 
of this requirement, gasket plates made from this reinforced support sheet 
have a very low pressure resistance, an insufficient temperature 
resistancy, as well as a completely insufficient longitudinal and 
transverse stability. 
Furthermore, the dough-like mass of the soft materials adheres to the 
calender rollers during manufacturing. As mentioned above, it has been 
attempted to overcome this disadvantage by adding additional water. 
However, this results in a different significant disadvantage in that the 
adherence ability of the dough-like soft material onto the support 
material is severely diminished, especially when a sheet metal is used 
without a mechanical clamping, fastening or mounting associated therewith. 
It is quite obvious that such a soft material is not usable for making 
flat gaskets which have to have the aforementioned criteria. 
It is therefore an object of the present invention to afford a reinforced 
support sheet or plate of the aforementioned type wherein the mentioned 
disadvantages of the known reinforced sheets or plates or the products 
made therefrom, for example, gaskets, are eliminated and, in addition, to 
provide a simple and cost saving method for making such a reinforced sheet 
or plate. 
In accordance with the invention, certain of the foregoing and related 
objects are obtained by the provision of a support sheet or plate of the 
aforementioned type, wherein the support material is smooth and the soft 
material layer predominantly consists of a powder-like, asbestos-free, 
mineral base material. 
In the inventive reinforced support sheet or plate, a dough-like base 
condition of the soft material is eliminated. Thereby, it is 
advantageously possible to reduce the rubber content (binder content), 
thus obtaining a high pressure resistance of the sheet or the flat gaskets 
made therefrom. A further significant advantage of the invention is that 
an application of additional water onto the calender rollers is no longer 
required. This results in the advantage that an excellent adherence 
ability of the soft material rolled onto the support material is obtained, 
even if the support material is a smooth sheet metal, foil, fleece or 
fabric. On account of the invention, it is possible to eliminate a 
mechanical mounting. Consequently, a very great advantage can be seen in 
that the reinforced support sheet or plate and the products made 
therefrom, like flat gaskets, for example, cylinder head gaskets, can be 
made substantially thinner than known gasket sheets or flat gaskets. 
In accordance with the invention, certain of the foregoing and related 
objects are also attained in a method for making such a reinforced support 
sheet or plate, where the soft material is applied successively onto both 
sides of the support material by means of calender rollers and, 
afterwards, is dried and vulcanized in an oven. In accordance with this 
novel method, a separate pair of calender rollers is provided for each of 
the sides of the support material to be coated and this soft material is 
applied as a flowable bulk material onto the given side of the support 
material immediately before it enters the opening between the given pair 
of calender rollers. The two rollers of the given pair of calender rollers 
are driven at unequal circumferential speeds. 
Due to the unequal circumferential speed of the two rollers of the given 
pair of calender rollers, a friction is exerted on the flowable soft 
material which is applied onto the support material which results in an 
excellent adherence of the soft material onto the surface of the support 
material. Due to the different circumferential speeds of the calender 
rollers, a further advantage is obtained in that an application of 
additional water on the calender rollers is no longer required. The 
elimination of the additional water again enhances the aforementioned 
adherence ability of the soft material which is rolled onto the support 
material. A further advantage of the inventive method is that an 
additional pulling device for the support material, which is required with 
known methods, can be eliminated. 
A great advantage of the invention is that the adhesive which, in most 
cases, is applied onto the support material before the coating operation, 
can be eliminated in almost all applicable cases. On the other hand, the 
invention does not exclude the use of an adhesive. For example, it is 
advisable to provide the support material with adhesive when the inventive 
sheet is used as a base material for making cylinder head gaskets which 
stand freely in water. 
At any rate, i.e., whether an adhesive is applied onto the support material 
or not, a dryer for the adhesive is eliminated in the inventive method 
(but is required in the known method disclosed in DE-AS No. 21 46 309). 
This means a considerable saving in energy relative to the method in 
accordance with DE-AS No. 21 46 309. 
In the case where an adhesive is used, it is preferred in accordance with 
the invention not to dry the adhesive because it assures a particularly 
good adherence of the soft material on the support materal in its tacky 
state. 
As already indicated above, the inventive method enables a concentrated 
adhesion of the soft material onto the support material without causing an 
adherenece on the calender rollers which would render the coating 
unusable. A further considerable advantage of the invention can be seen in 
that a single oven is used for the drying and vulcanization of the applied 
soft material and that these operative steps can be performed in one 
single operation. With respect to the known methods, in which three or 
four ovens are required, considerable savings are realized by the subject 
invention with respect to purchases, required space and energy 
consumption, which are required for the plant for making the products. 
Further savings along the aforementioned lines can be obtained with the 
inventive method in that the required thickness and density, as well as 
the accuracy of measurement of the applied soft material layers, are 
obtained without the usual successive series of calibrating rollers in the 
known devices. 
Finally, it should be noted that the inventive method still has the 
advantage over the known state of the art in accordance with DE-AS No. 21 
46 309 in that no kneading process, no strand pressing and no preparation 
in tablet form is required for the soft material. 
Therefore, the inventive method enables one to eliminate the considerable 
cost and safety preparations as required in the aforementioned method in 
accordance with DE-AS No. 21 46 309 (see, in particular, column 5, 
paragraph 3 of the aforementioned patent). In contrast thereto, the 
inventive method requires only one single operating step. 
Other objects and features of the present invention will become apparent 
from the following detailed description considered in connection with the 
accompanying drawing, which discloses one embodiment of the invention. It 
is to be understood that the drawing is to be used for the purposes of 
illustration only, and not as a definition of the limits of the invention.

Referring now in detail to the drawing, the support material 10 can be a 
strip of sheet metal, foil, fleece or fabric which is drawn off a supply 
drum or roller (not shown). As a material for the support material one can 
use metal, plastic or paper. The shape and the material of the support 
material depends upon the intended use of the sheet or plate to be made. 
The feeding direction is shown by an arrow 11. The main stations of the 
illustrated installation are two pairs of calender rollers 12, 13 and 14, 
15, as well as a drying and vulcanization oven 16. A container 17 is 
associated with the pairs of calender rollers 12, 13 and 14, 15 which 
serves to receive the flowable bulk material or goods of the soft material 
and apply the same into the opening between the rollers 12, 13 and 14, 15 
of the given pair of calender rollers. The soft material which is 
contained in containers 17 is a substance in the form of a flowable bulk 
material. 
The soft material should comprise (by weight) at least 80% of a 
powder-like, asbestos-free mineral base material, for example, a ground 
rock and only up to 6% binder material. The remaining component, usually 
about 3% or a maximum of 14% is composed of an asbestos-free fiber 
material, for example, a polyamide-, cellulose- or other natural- or 
synthetic fibers. A fine ground shale is preferably used for the base 
material. However, it is feasable to use other asbestos-free, powder-like 
mineral materials. The binder material component of the soft material, 
preferably (in the base condition) a synthetic rubber-toluene-mixture, is 
limited to about 6%. 
The aforementioned materials are admixed in a mixer and thereby result in 
the desired flowable soft material. The manufacturing method by means of 
the illustrated installation is performed as follows: 
The uncoated support material, for example, a strip of sheet metal, is fed 
between two rollers 18, 19. Thereat, it can be coated on the surface with 
an adhesive, if so desired. The adhesive is present in a container 20 
above roller 18. If a coating of the support material 10 with adhesive is 
desirous, the adhesive is "ordered" from container 20 by means of a 
suitable conventional supply device (not shown) and is applied onto roller 
18. From roller 18, it is then applied to the surface of the support 
material 10. Subsequently, the support material 10 is deflected from an 
initial horizontal direction into a vertical direction by means of 
deflection roller 21 and is fed into the opening between the first pair of 
calender rollers 12, 13. Here, the flowable soft material is applied from 
container 17 onto the surface of support material 10 which may be applied 
with adhesive or not. Subsequently, the one-side-coated support material 
is fed over a further deflection roller 22 and into the already mentioned 
oven 16 within which a first drying of the applied soft material occurs. 
When moving through the oven 16, the one-side-coated support material 10 
is supported by support rollers 23. 
After leaving oven 16 and, after a two-time deflection by about 90.degree., 
the one-side-coated support material 10 is fed to a second adhesive 
coating device, whose components are provided with the same reference 
numerals as the previously-described adhesive supply device 18-20 for the 
sake of simplicity and clarity. Here, the still uncoated side of the 
support material 10 is provided with adhesive, if so desired. Thereafter, 
the support material 10 is again deflected by means of a deflection roller 
25 from the horizontal direction into a vertical direction and a coating 
is applied on the other side of support material 10 (if need be with the 
already applied adhesive coating) by the aforementioned second pair of 
calender rollers 14, 15 and the flowable soft material which is present in 
the associated container 17. 
In this context, it is important to mention that the circumferential speeds 
of the individual rollers 12, 13 or 14, 15 of each pair of the calender 
rollers as indicated by arrows 26, 27 or 28, 29 are unequal in their 
dimension in such a manner that a friction is exerted on the soft material 
34, 35. 
The support material which is now coated on both sides is then fed into the 
interior of oven 16 by means of further deflection rollers 30. In this 
oven, the drying of the previously-applied soft material layer and, 
simultaneously, the vulcanization of both of the material layers is 
performed. In order to provide a sufficient time for this process, three 
rollers 31 are provided with a relatively large diameter which assures 
that the path travelled by the coated material in the oven is 
correspondingly long (during its second throughput). 
After leaving the oven 16, the finally finished reinforced support sheet is 
fed over a further deflection roller 32 onto a wind-up roller 33. 
The aforedescribed coating method illustrated in the drawing for producing 
a support material 10 coated on both sides with a soft material layer 34 
or 35 enables the application of different material compounds and/or in 
different thicknesses, depending on the intended load conditions of the 
flat gaskets which are subsequently made from these sheets. Thereby, the 
soft material layer 34 can be made of a friction-resistant material 
composition on the one side of the support material 10. However, these are 
merely examples for a possible individual design of the soft material 
layers 34, 35 and the invention is by no means limited to such examples. 
Such a design of the reinforced support sheet or plate affords an excellent 
pressure resistance, good spring back resiliency, temperature resistance 
and a high longitudinal and transverse stability. Therefore, high 
requirements can be exerted onto the products which are made by such a 
sheet or plate, for example, flat gaskets, with respect to mechanical and 
thermal stress. The inventive sheet or plate, as well as the end products 
made therefrom are characterized by an extreme low thickness. Because of 
the solid adherence of the soft material on the support material, no 
mechanical mountings are required, so that the support material can be 
smooth-faced. 
Accordingly, while only one embodiment of the present invention has been 
shown and described, it is obvious that many changes and modifications may 
be made thereunto without departing from the spirit and scope of the 
invention.