Method of manufacturing a steel plate with a seal coating for a steel laminate gasket

A method of manufacturing a steel plate for a steel laminate gasket comprises applying a first seal coating consecutively on at least one side of a base plate in the shape substantially the same as that of an actual steel plate for constituting the gasket. After the first seal coating on the base plate is dried, the base plate is pressed or cut to form a plurality of steel plates. Each steel plate has a configuration as in the actual steel plate, an outer surface formed by the first seal coating on the entire one side thereof and a plurality of holes therein. When a steel laminate gasket is formed, the steel plate with the seal coating thereon is stacked with other steel plates so that the seal coating is located between the two steel plates.

BACKGROUND OF THE INVENTION AND RELATED ART STATEMENT 
The present invention relates to a method of manufacturing a steel plate 
with a seal coating for a steel laminate gasket. Further, the present 
invention disclosed a method of manufacturing a steel laminate gasket with 
a seal coating between steel plates. 
A steel laminate gasket is formed of a plurality of steel plates stacked 
one after another. In one of a steel laminate type cylinder head gasket, 
for example, sealing means is provided around cylinder bores and holes for 
oil and water of the gasket to seal around the bores and holes, while in 
some of a steel laminate type cylinder head gasket, a plurality of steel 
plates is simply stacked together without using any sealing means around 
the cylinder bores and holes for oil and water. 
The steel laminate gasket is situated between two engine parts and is 
tightened strongly in use. However, if sealing means is not provided 
around the cylinder bores and holes for oil and water, fluid may leak 
therefrom by passing between the steel plates. Especially, since 
tightening pressure around the holes for oil and water is not strong, 
water and oil are liable to leak around the holes for oil and water. 
Namely, the gasket can not provide sufficient sealing, and leakage causes 
corrosion of a gasket. 
In order to prevent leakage around water and oil holes, it was proposed 
that a seal coating is formed between two steel plates. The seal coating 
may be provided on one of two steel plates facing with each other or both 
sides of the steel plates. The seal coating must be even in thickness to 
properly seal between the two steel plates. 
One method of forming a steel plate with a seal coating is that a seal 
coating is formed on one or both entire sides of a base plate, and then 
the base plate is pressed or cut to thereby form a complete steel plate. 
In this method, the seal coating material is applied on the entire surface 
of the base plate. Namely, the seal coating is applied onto an area of the 
base plate which is not used for a steel plate of a gasket. In some 
situations, about 50% of the base plate is used for the steel plates of a 
gasket, and the rest of the base plate is discarded. Since the coating 
material is expensive,the method of coating the coating material on the 
entire surface of the base plate is costly. 
Another method of forming a steel plate with a seal coating is that a base 
plate is, at first, cut into the actual configuration of the steel plate, 
and the coating is applied thereon. In case the steel plate is formed by 
cutting the base plate, the steel plate is slightly deformed. Therefore, 
it is very difficult to coat the coating material with even thickness. 
Further, the coating material is liable to accumulate around edge portions 
of the steel plate. As a result, it is very difficult to apply onto the 
steel plate a seal coating with even thickness. 
Accordingly, one object of the present invention is to provide a method of 
manufacturing a steel plate with a seal coating, wherein a seal coating 
can be formed on a steel plate with a minimum amount of a coating 
material. 
Another object of the invention is to provide a method of manufacturing a 
steel plate as stated above, wherein a seal coating can be evenly applied 
onto a steel plate. 
A further object of the invention is to provide a method of manufacturing a 
steel laminate gasket with a seal coating between steel plates, which can 
be easily and economically made. 
A still further object of the invention is to provide a method of 
manufacturing a steel laminate gasket as stated above, wherein the sealing 
ability of the gasket is excellent. 
Further objects and advantages of the invention will be apparent from the 
following description of the invention. 
SUMMARY OF THE INVENTION 
In accordance with the present invention, a method of manufacturing a steel 
plate for a steel laminate gasket is disclosed. In this method, at first, 
a first seal coating is applied onto at least one side of a base plate in 
the shape substantially the same as that of an actual steel plate. After 
the first seal coating is dried, the base plate is pressed or cut to form 
a plurality of steel plates. Each steel plate is provided with a 
configuration as in an actual steel plate, an outer surface formed by the 
first seal coating on the entire one side thereof and a plurality of holes 
therein. 
After the first seal coating is dried, a second seal coating may be applied 
onto the first seal coating at a selected area. Thereafter, the second 
seal coating is dried. Preferably, the second seal coating is formed 
around holes for water and oil. Also, the second seal coating is formed 
adjacent to an outer periphery of the gasket. In case the second seal 
coating is formed around the holes for water and oil, the area around the 
holes for water and oil can be securely sealed. Alternatively, the second 
seal coating is applied onto the base plate prior to the first seal 
coating. After the second seal coating is dried, the first seal coating is 
applied onto the base plate over the second seal coating. 
When a steel laminate gasket is formed, the steel plate with the seal 
coating thereon is assembled with other steel plates so that the seal 
coating is located between the two steel plates. The steel plates may be 
connected together by spot welding. Since the seal coating is situated 
between the adjacent two steel plates, leakage of liquid between the two 
steel plates is substantially prevented.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
Referring to FIG. 1, a method of manufacturing a steel plate with a seal 
coating and a method of manufacturing a steel laminate gasket using the 
steel plate with a seal coating are shown in a block diagram. 
When a steel plate with a seal coating thereon is manufactured, a seal 
coating in the shape slightly larger than or substantially the same as 
that of the actual steel plate is applied onto a base plate at a coating 
section 10. Then, the coating on the base plate is dried at a dry section 
12. Finally, the base plate is pressed or cut at a press section 14 to 
form a steel plate with accurate configuration and size. 
When a second or partial coating is further applied onto the seal coating, 
a partial coating is made at a coating section 16. The partial coating is 
dried at a dry section 18. Finally, the base plate with two coatings 
thereon is cut at the press section 14 to form a steel plate. 
Alternatively, the partial coating is, at first, formed on the base plate 
at a coating section 17, and then dried at a drying section 19. 
Thereafter, a coating is applied on the base plate over the partial 
coating at the coating section 10. After drying the coating, the base 
plate is cut at the press section 14. 
In case a steel laminate gasket is formed, the steel plate with the seal 
coating theron is assembled with other steel plates at an assembly section 
20. At the assembly section 20, the steel plates are stacked together so 
that the seal coating is situated between the two plates. As a result, 
when the gasket is used, fluid does not penetrate into a space between the 
two plates. 
FIG. 2 shows a line for continuously manufacturing steel plates with seal 
coatings thereon. As shown in FIG. 2, a base plate 22 is in the elongated 
rectangular form, wherein the property of the base plate is selected based 
on requirement of the gasket. 
At the coating section 10, a seal coating 24 is continuously applied onto 
the base plate 22. The seal coating 24 applied at the coating section 10 
is in the shape slightly larger than the shape of the actual steel plate 
for constituting a steel laminate gasket. The seal coating 24 is not 
formed on portions for constituting bore and hole portions, i.e. cylinder 
bores and holes for water and oil, of the actual steel plate. 
The seal coating 24 must have heat-resistance and oil-resistance properties 
and fluidity when the seal coating 24 is applied onto the base plate. 
Further, the seal coating must be congenial to a metal plate. The seal 
coating 24 may be fluorocarbon polymer, fluorine-containing rubber, 
silicone polymer, silicone gum, chloroprene rubber, nitrile rubber or 
chlorosulfonated polyethylene. 
The seal coating 24 must be applied onto the base plate 22 evenly and 
consecutively at the coating section 10. Preferably, the seal coating 24 
is formed by a screen printing. Other methods, or a combination thereof, 
such as an electronic printing or a transfer printing, may be utilized. 
The thickness of the seal coating 24 is selected based on the sealing 
condition, generally 5-200 micra. 
After the seal coating 24 is imprinted onto the base plate 22, the base 
plate 22 is heated to dry the seal coating 24 at the dry section 12. The 
seal coating 24 is adhered onto the base plate 22. 
The base plate 22 with the seal coating 24 is cut by a press at the press 
section 14. Since the seal coating formed on the base plate 22 is slightly 
larger than the actual configuration of the steel plate for constituting 
the gasket, when the base plate is cut into the actual size, the seal 
coating is evenly coated throughout the entire one side of the steel 
plate. 
Cylinder bores Hc, water holes Hw, oil holes Ho and so on, may be formed at 
the same time of cutting the outer configuration of the steel plate at the 
press section 14. However, after the outer configuration of the actual 
steel plate is cut at the press section 14, the bores Hc and holes Hw and 
Ho may be formed on the steel plate. The seal coating 24 must be evenly 
coated throughout the entire one side of the actual steel plate as shown 
in FIG. 3. 
In case the seal coating 24 is formed on both sides of the base plate 22, 
after the seal coating 24 is formed and dried on one side of the base 
plate 22, the seal coating 24 is applied on the reverse side of the base 
plate 22 and dried. The seal coatings 24 on both sides of the base plate 
22 must exactly conform to each other. 
When the second or partial coating 26 (FIG. 4) is formed on the seal 
coating 24, after the seal coating 24 is formed and dried, the partial 
coating 26 is applied onto the seal coating 24 and dried. The partial 
coating 26 is formed around the water holes Hw and oil holes Ho and along 
the outer periphery of the steel plate. Namely, the partial coating 26 is 
formed at portions requiring additional sealing pressure. As a result, it 
is possible to properly seal around the water holes and oil holes. 
Alternatively, after the partial coating 26 is formed, the seal coating 24 
may be formed. 
FIG. 5 shows a partial section view of a steel laminate gasket 28 using the 
steel plates with the seal coatings 24 thereon. The gasket 28 comprises 
outer plates 30, 36, an inner plate 32 and an inner plate 34 with a bead 
34a around the water hole Hw. The outer plates 30, 36 are provided with 
seal coatings 30', 36' on both sides of the respective plates, while the 
plates 32, 34 are provided with seal coatings 32', 34' on one side of the 
respective plates. The plates 30, 32, 34, 36 are stacked together so that 
the seal coatings are situated between the adjacent two plates 
respectively. The plates may be connected together by spot welding. 
Since the gasket 28 is provided with seal coatings between the respective 
two plates as well as the bead 34a, it is possible to securely seal around 
the water hole Hw without using special sealing means. 
In accordance with the present invention, the seal coating having a 
configuration similar to the configuration of the actual steel plate for 
constituting a gasket is printed on a base plate. After the seal coating 
is dried, the base plate is cut into the actual size of the steel plate 
for a gasket. Therefore, a necessary amount of coating material is only 
used in the present invention. Since the coating material is expensive, 
the present method is very economical. Further, in the present invention, 
it is possible to provide the seal coating with even thickness. 
While the present invention has been explained with reference to the 
specific embodiments of the invention, the explanation is illustrative and 
the invention is limited only by the appended claims.