Metal gasket

The present invention relates to a metal gasket for installation into a gap between a cylinder head and a cylinder block of a multi-cylinder engine by bolt fasteners. The gasket includes a base plate and a supplementary plate. The base plate has a plurality of combustion chamber openings, a plane plate portion surrounding each of the openings, and a convex cross-sectional shaped bead surrounding the plane plate portion and providing an inner and an outer sealing line on a concave side of the bead on the side of the opening and on the far side of the opening, respectively. The supplementary plate is overlapped with the concave side of the base plate and extended from a periphery of each opening to an area of the bead passing through the plane flange portion and the inner sealing line. The supplementary plate, however, is not extended to the outer sealing line. In this way, the supplementary plate forms a portion increased in thickness. Only the inner sealing line of two sealing lines overlaps with the portion which is increased in thickness having relatively wide width. The inner sealing line provides a good sealing function to seal the gap around the combustion chamber opening where the gap clearance is larger than that in the portion near the bolt fastening portion and, therefore, provides good durability during the engine operation.

FIELD OF THE INVENTION 
The present invention relates to a metal gasket for sealing a gap between a 
cylinder head and a cylinder block of an internal combustion engine, and 
more particularly, to a metal gasket for coping with a phenomenon of 
opening the gap between the cylinder head and cylinder block in accordance 
with a distance from a bolt fastening part to a part around a combustion 
chamber opening gradually and for sealing a whole gap between the cylinder 
head and the cylinder block with a uniform sealing pressure at the time of 
securing a cylinder head and a cylinder block in multi-cylinder engines. 
BACKGROUND OF THE INVENTION 
When a cylinder head and a cylinder block of an internal combustion engine 
are secured in the prior art, as shown in FIG. 34, after situating a metal 
gasket formed with a bead 53 for surrounding a combustion chamber opening 
42 between the gap of a cylinder head 45 and a cylinder block 46, it is 
bolted with a bolt 40 at a predetermined bolt fastening part 41. At this 
time, the bead 53 is elastically deformed by a fastening force of the bolt 
40, and the elastically restoring force and the elastic restoration at the 
time of the elastic deformation form an elastic sealing line between the 
gap between the cylinder head 45 and the cylinder block 46 and thereby 
sealing the gap. 
However, although the cylinder head 45 is bolted at each fastening part 41 
with the uniform fastening force as shown in FIG. 33, the whole gap of the 
cylinder head 45 and the cylinder block 46 can not be secured uniformly 
and such gap changes variously according to the relation with the position 
of the bolt fastening part 41. 
This is because the larger the distance from the fastening part 41 is, the 
lower the fastening force of the bolt 40 becomes. As a result of that, as 
the distance from the bolt fastening part, 41 becomes larger, the gap 
between the cylinder head 45 and the cylinder block 46 becomes larger, 
thereby deteriorating the sealing pressure of the bead. 
In particular, in the multi-cylinder engines arranging a plurality of the 
combustion chamber openings 42 as shown in FIG. 33, such gap clearance 
between the cylinder head 45 and the cylinder block 46 gradually increases 
in order of a gap portion extending from the bolt fastening part 41 to a 
part around the combustion chamber opening 42 (A-A'-A" cross-sectional 
part of FIG. 33), a gap portion between the bolt fastening parts 41 and 41 
(B-B' cross-sectional part of FIG. 33), and a gap portion between the 
combustion chamber openings 42 and 42 (C-C' cross-sectional part of FIG. 
33). This leads to considerable blowing-off of burned gas between the 
adjacent combustion chamber openings. 
Further, the surfaces of gasket between the cylinder head 45 and the 
cylinder block 46 are beaten due to the repetition of the increase and 
decrease of the gap clearance by the explosion gas pressure in the 
combustion chamber opening 42. As a result, the gasket is easily apt to 
cause failure deformation not only between the bolt fastening parts 41 and 
41 but also the bead near the bolt fastening part 41, thereby 
deteriorating the sealing pressure of the gap between the cylinder head 45 
and the cylinder block 46. This results in serious problems such as an 
enhanced blowing-off of the gas and loosening of the fastening bolts 40. 
Accordingly, in order to solve the above mentioned problems, in the 
conventional metal gasket, a supplementary plate 52 is provided against a 
base plate 51 in which a bead 53 is formed, as shown in FIG. 34. 
The reference is made to the explanation about the conventional metal 
gasket based on FIGS. 35 (a) to (c). FIG. 35 (a) corresponds to a A-A'-A" 
cross-sectional part of FIG. 33 and is a cross-sectional view of a part 
around the combustion chamber opening of the metal gasket in the gap from 
the bolt fastening part 41 to the part around the combustion chamber 
opening 42. Hereinafter, similarly, FIG. 35 (b) corresponds to a B-B' 
cross-sectional part of FIG. 33 and is a cross-sectional view of a part 
around the combustion chamber opening of the metal gasket between the bolt 
fastening parts 41 and 41, and FIG. 35 (c) corresponds to a C-C' 
cross-sectional part of FIG. 33 and is a cross-sectional view of a part of 
the metal gasket between the combustion chamber openings 42 and 42. 
In the FIGS. 35 (a) to (c), the reference numeral 51 is a base plate for 
forming a bead 53 in which the bead having an arc and convex shape in the 
cross-section is formed, and 52 is a supplementary plate. This 
supplementary plate 52 is provided on whole surface of the base plate 51 
in the concave side of the bead 53 and is folded to the convex side of the 
bead 53 at an inner periphery end of a plane plate portion 51a to overlap 
to the surface of the plane plate portion 51a, thereby forming a portion 
52a increased in thickness. Further, in FIG. 35 (c), when the distance 
between the combustion chamber openings 42 and 42 is narrow and it is not 
possible to form an independent bead 53 relative to each combustion 
chamber opening 42, two beads are connected to each other and merged in 
one bead 53 at the center point between the combustion chamber openings 42 
and 42. Accordingly, the plane plate portions 51a and 51a are provided at 
both sides of the bead 53 and this results in the construction of 
overlapping the portions 52a and 52a increased in thickness under the 
plane plate portions 51a and 51a. 
In the above mentioned construction, by controlling bead heights H51, H52, 
and H53 and the bead widths W51, W52, and W53 in accordance with the gap 
clearance between the cylinder head 45 and the cylinder block 46, the gap 
between the cylinder head 45 and the cylinder block 46 can be compensated. 
Further, by providing a portion 52a increased in thickness around the 
combustion chamber opening 42, it is possible to compensate the gap 
between the cylinder head 45 and the cylinder block 46 around the 
combustion chamber opening 42 in which the gap clearance, at the time of 
fastening the bolt, is large. 
However, according to the above mentioned metal gasket, since the 
supplementary plate 52 is provided on whole surface of the base plate 51 
in the concave side of the bead 53 and is folded at the side the 
combustion chamber opening 42 to overlap with the plane plate portion 51a, 
two inner and outer sealing lines 51f and 51j formed in the concave side 
of the bead 53 are overlapped by the supplymentary plate 52 and each of 
the increased amounts in thickness at the sealing lines 51f and 51j by the 
supplymentary plate 52 becomes equal. On the other hand, as for the bead 
heights H51, H52, and H53 projecting to the convex side of the bead 53, 
the deflective height is reduced for the thickness S51 of each portion 52a 
increased in thickness, thereby causing the problem of deteriorating the 
sealing pressure of the bead. In other words, the portion 52a increased in 
thickness provided to compensate the gap whose clearance is larger around 
the combustion chamber opening 42 than the other gap portion and causes 
the deterioration of the sealing pressure of the bead 53 and the sealing 
function by the bead. 
Further, between the combustion chamber openings 42 having a largest gap 
clearance between the cylinder head 45 and the cylinder block 46, as shown 
in FIG. 35 (c), not only the deflective height of the bead 53 is reduced 
by the thickness S51 of both portions 52a and 52a increased in thickness 
but also both portions 52a and 52a increased in thickness tend to be in 
the state of floating between the gap, because these portions 52a and 52a 
locate in the convex side of the bead 53. That is, the more the bead 
height H53 of the bead 53 increases, the more both portions 52a and 52a 
are beaten by the repetition of the increase and decrease of the gap 
clearance due to the explosion gas pressure, thereby causing the breakage 
of both portions 52a and 52a and deteriorating the sealing function. 
Even though both portions 52a and 52a increased in thickness are formed to 
be thicker than other parts of the portion 52a in FIGS. 35 (a) or (b), 
corresponding to the large gap clearance between the combustion chamber 
openings 42 and 42, such gap clearance changes in accordance with the 
variations in dimensions by each engine and the order of fastening the 
bolts even in the same type of engine. Accordingly, it may produce the 
reverse effect on the sealing function by thickening the portion 52a 
increased in thickness and it is also very difficult to process the 
portion 52a having a variable thickness. 
Further, if failure deformation occurs in the bead 53 by beating due to the 
explosion gas pressure, the fastening bolt 40 may come loose. This causes 
considerable deterioration of the engine function. 
SUMMARY OF THE INVENTION 
The present invention is to solve the above mentioned problems according to 
the conventional art. One object of the present invention is to provide a 
metal gasket for securing a sealing function of all of the gap between the 
cylinder head and the cylinder block by making a sealing pressure at the 
gap portion between the combustion chamber openings very strong at the 
time of fastening a bolt, which is not sufficient in the conventional art. 
Another other object of the present invention is to provide a metal gasket 
for making good use of the sealing function of a bead without any 
reduction of the surface pressure of the bead by a portion increased in 
thickness so as to compensate the largest gap clearance between the 
cylinder head and the cylinder block around the combustion chamber 
opening. 
Another object of the present invention is to provide a metal gasket for 
compensating the gap between the cylinder head and the cylinder block, 
which opens gradually from the bolt fastening part to the part around the 
combustion chamber opening, with a uniform sealing pressure regardless of 
such gap clearance variation. 
Further, the other object of the present invention is to provide an 
improved metal gasket, wherein it is not easy to produce the failure 
deformation of the bead even on when the cylinder block is beaten by the 
cylinder head due to the explosion gas pressure. It is possible to secure 
a durability of the bead without any loosening of the fastening bolt.

DETAILED DESCRIPTION OF THE INVENTION 
Hereinafter, the reference is made to the explanation of the embodiments of 
the present invention based on the drawings. 
FIGS. 1(a) to (c) are illustrations for showing the cross-sectional state 
around the same combustion chamber opening 6 of, for example, FIG. 2. FIG. 
1(a) is a cross-sectional view around the combustion chamber opening along 
with the A-A'-A" line of FIG. 2, FIG. 1(b) is a cross-sectional view 
around the combustion chamber opening along with the B-B' line, and FIG. 
1(c) is a cross-sectional view between the combustion chamber openings 
along the C-C' line. 
The reference numeral 1 indicates a base plate for forming a bead, 
comprising an elastic metal plate, and a plane plate portion 1a is formed 
at the inner periphery end around the combustion chamber opening 6 in this 
base plate 1 for predetermined width. The plane plate portion 1a is 
surrounded by a bead 3 whose cross-sectional shape is an arc and convex. 
Further, 2 is a supplementary plate, made of a soft metal plate, and such 
supplementary plate 2 is provided on the whole surface of the base plate 1 
in the convex side of the bead 3 and is folded to the concave side of the 
bead 3 at the inner periphery end of the plane plate portion 1a, thereby 
forming the portion 2a increased in thickness. The outer periphery end 2b 
of the portion 2a increased in thickness extends to about the center 
position of the bead 3. 
In each bead 3 of FIGS. 1(a) to (c), the bead width corresponding to the 
A-A'-A" cross-sectional part of FIG. 2 is designated as W1 and the bead 
height is H1. The bead width corresponding to the B-B' cross-sectional 
part of FIG. 2 is designated as W2 and the bead height is H2. The and the 
bead width corresponding to the C-C' cross-sectional part of FIG. 2 is as 
W3 and the bead height is H3. As one gets farther from the bolt fastening 
part 11, the bead width of the bead 3 around the combustion chamber 
opening is reduced gradually, that is, W1&gt;W2&gt;W3 and the bead height is 
increased gradually, that is, H1&lt;H2&lt;H3. Such controlling of bead height 
and bead width makes the bead sealing pressure strong and more uniform 
regardless of the variation of the gap clearance between the cylinder head 
12 and the cylinder block 13 which becomes wider in order of the A-A'-A" 
cross-sectional part of FIG. 2, the B-B' cross-sectional part, and the 
C-C' cross-sectional part, thereby realizing the sealing by the bead 3. 
FIG. 1(c) shows a state of forming the bead 3 in the case the distance 
between the adjacent combustion chamber openings 6 and 6 is relatively 
narrow as shown in FIG. 4. The beads 3 and 3 are formed around each 
adjacent combustion chamber opening 6 and the beads 3 and 3 are connected 
and merged in one bead at the point where each combustion chamber opening 
6 is close to each other. Namely, as shown in FIG. 1(c), the plane plate 
portions 1a and 1a are formed at both sides of the bead 3, and the 
supplementary plate 2 covers the convex side of the bead 3 and is folded 
to the concave side of the bead 3 at the periphery ends of both plane 
plate portions 1a and 1a so as to overlap these plane plate portions 1a 
and 1a, thereby forming the portions 2a and 2a increased in thickness. 
Two bottom portions in the concave side of the bead 3 form an inner sealing 
line if and an outer sealing line ij, for surrounding the combustion 
chamber opening 6 and these draw tracks of the sealing lines of FIG. 5 in 
the case of the multi-cylinder engines in which the distance between the 
combustion chamber openings 6 is relatively narrow. Namely, FIG. 5(a) 
shows tracks of the inner sealing lines 1f, wherein each of them is 
independent around each combustion chamber opening 6. FIG. 5(b) shows the 
track of the outer sealing line ij, wherein it surrounds the periphery of 
each combustion chamber opening 6 and draws the connected track when the 
bead 3 is merged at each point between the combustion chamber openings 6. 
Accordingly, as shown in FIG. 1(c), the inner sealing lines if and If are 
formed at the both bottom portions of the bead 3 between the combustion 
chamber openings 6. 
As for the above mentioned construction, in FIGS. 1(a) and (b), since the 
portion 2a increased in thickness, in the concave side of the bead 3, is 
overlapped under the plane plate portion 1a near the combustion chamber 
opening 6, only the inner sealing line if passes through in the state of 
coming in contact with the upper surface of the portion 2a increased in 
thickness. 
According to the above mentioned metal gasket, in the A-A'-A" 
cross-sectional portion or the B-B' cross-sectional portion of FIG. 2, as 
shown in FIGS. 1(a) and (b), only the inner sealing line If is overlapped 
by the portion 2a increased in thickness and the outer sealing line 1j is 
not overlapped by the same. Therefore, near the bolt fastening part 11, 
when the bead 3 is flattened on fastening by the bolt, the total thickness 
of the metal gasket is thicker in the side of inner sealing line 1f (the 
engine combustion chamber opening side)than in the side of the outer 
sealing line 1j and these thickness differences at both side of the bead 3 
causes good sealing functions near the engine combustion chamber opening 6 
(wedge effect). When the bead 3 located in the A-A'-A" and B-B' 
cross-sectional portions is flattened on fastening the cylinder head 12 
and the cylinder block 13 by bolts, the gap clearance in the C-C' 
cross-sectional portion is larger than other portions. But good sealing 
pressure at this portion can be attained by the bead 3 having higher 
height H3 and narrower width W3 at this portion as shown in FIG. 1(c). So 
the uniform sealing pressure can be obtained all around the combustion 
chamber opening 6. 
And at this bead flattened state, in the A-A'-A" or the B-B' 
cross-sectional portion, in the bead side 3b, the total thickness of the 
metal gasket is less for the thickness S. Therefore, even in the case the 
plastic deformation occurs at the inflection point of the base plate 1 at 
the inner sealing line 1f at the bead, flattened state as the gap 
clearance between the cylinder head and the cylinder block at the outer 
sealing line 1j is approximately equal to the total thickness of the 
gasket at the sealing line 1f and is wider than the thickness of the base 
plate 1, the spring force by the bead side 3a in the side of the outer 
sealing line 1j remains and it functions to give sealing pressure when the 
gap clearance increases due to the gas pressure. 
Additionally, as the outer periphery end 2b of the portion 2a increased in 
thickness extends to about the center portion of the bead 3, the portion 
2a is wide in the width to give wider contact area to the cylinder block 
compared with the conventional art shown in FIGS. 35(a) and (b) and it 
prevents the defective deformation of the contact surface of the cylinder 
block by the excessive sealing pressure and also overcomes small nicks, 
flaws or other unevenness on the contact surface of the cylinder block. 
Furthermore, the inflection point of the base plate 1 at the inner sealing 
line if between the bead 3 and the plane plate portion 1a is completely 
ridden on the portion 2a, and therefore, there is no increase in stress 
concentration at this point by providing this portion 2a, when the bead 3 
is flattened. 
Further, in the C-C' cross-sectional portion of FIG. 2 (c), both of the 
inner sealing lines if and if are overlapped by the portions 2a and 2a 
increased in thickness. Accordingly, wider contact area of the portion 2a 
and 2a to the cylinder block surface of relatively narrow width can be 
provided compared with the conventional art shown in FIG. 35(c), and it 
gives preferable sealing function and good durability against the 
phenomenon of the repetition of the increase and decrease of the gap 
clearance due to the gas pressure during the engine operation. 
As mentioned above, as for the bead 3 of the metal gasket cited as one 
embodiment of the present invention, both bead sides 3a and 3b have the 
common symmetric arc shape to give the bead 3 of symmetric convex shape. 
As examples of the present invention using such symmetric convex shaped 
bead, there are variations as shown in FIGS. 6 to 10. In these FIGS. 6 to 
10, each (a) corresponds to the A-A'-A" cross-sectional portion, each (b) 
to the B-B' cross-sectional portion, and each (c) to the C-C' 
cross-sectional portion of FIG. 2, respectively. 
The metal gasket as shown in FIGS. 6(a) to (c) has a similar construction 
to that of FIG. 1. 
As for the metal gasket as shown in FIGS. 7(a) to (c), the supplementary 
plate 2 is provided under the base plate 1 in the concave side of the bead 
3 and the supplementary plate 2 is folded at the plane plate portion 1a 
near the combustion chamber opening, thereby forming the portion 2a 
increased in thickness. 
As for the metal gasket as shown in FIGS. 8(a) to (c), a ring shape 
supplementary plate 2 is provided under the plane plate portion 1a near 
the combustion chamber opening in the concave side of the bead 3, thereby 
forming the portion 2a increased in thickness. 
As for the metal gasket as shown in FIGS. 9(a) to (c), a step 4a is formed 
by bending the portion near the combustion chamber opening of an 
intermediate plate 4 and the supplementary plate 2 is provided along with 
the intermediate plate 4, the inner periphery end 2b of the supplementary 
plate 2 is folded to the concave side of the step 4a of the intermediate 
plate 4, and the lower side of the intermediate plate 4 is made planar, 
thereby forming the portion 2a increased in thickness in the convex side 
of the step 4a of the intermediate plate 4. Further, two base plates 1 and 
1 in which the bead 3 is formed are provided on both surfaces of the 
intermediate plate 4. 
As for the metal gasket as shown in FIG. 10(a) to (c), the portion near the 
combustion chamber opening of the supplementary plate 2 is folded on the 
intermediate plate 4 having no step 4a in FIGS. 9(a) to (c), thereby 
forming the portion 2a increased in thickness. 
All metal gaskets as shown in FIGS. 6 to 10 have the construction of 
overlapping the portion 2a increased in thickness to the plane plate 
portion 1a in the side of the combustion chamber opening 6 and in the 
concave side of the bead 3 formed in the base plate 1 and all metal 
gaskets have the same effect as that shown in FIG. 1. And particularly, 
examples, shown in FIGS. 9 and 10 having two base plates can receive wider 
height change and are preferable for use in engines wherein the gap 
clearance changes widely by the combustion gas pressure. 
Further, the other embodiment is shown in FIG. 11. As for the metal gasket 
as shown in FIG. 11, a bead side 3'b in the side of the outer sealing line 
1j has an arc shape and a bead side 3a in the side of the inner sealing 
line 1f is an arc shape of larger radius than the bead side 3'b or 
approximately linear (hereinafter, both shapes are expressed as 
"approximately linear"), and both sides 3'a and 3'b form a bead 3' of 
non-symmetric convex shape, in the A-A'-A" or the B-B' cross-sectional 
portion of FIG. 2, wherein the metal gaskets as shown in FIGS. 1 and 6 to 
10 have the bead of the symmetric convex shape. However, in the C-C' 
cross-sectional portion of FIG. 2, when the distance between the 
combustion chamber openings 6 and 6 is narrow and one bead 3' passes 
through therebetween, the bead 3' becomes symmetric shape similar to the 
bead 3 as shown in FIG. 1(c). The height and the width of the bead 3' 
corresponding to the A-A'-A", the B-B' and the C-C' cross-sectional 
portion is gradually increase and decrease, respectively, as getting 
farther from the bolt fastening part, similar to the metal gasket in FIG. 
1. 
According to the above construction, in the A-A'-A" and the B-B' 
cross-sectional portions of FIG. 2, a spring constant of the bead side 3a 
in the side of the portion 2a increased in thickness is smaller than that 
of the bead side 3'b, without the decrease of the bead height, and the 
spring load in the bead side 3a at the time of bolt fastening is reduced. 
Therefore bolts are easily fastened with relatively smaller fastening 
torque than those in the case of the metal gasket having a bead of 
symmetric convex shape cross-section. Therefore the predetermined bolt 
fastening load can be applied to the whole surface of the metal gasket to 
give good sealing contact between the gasket and the cylinder block. Other 
functions and effects than those by forming the bead 3' to have 
non-symmetric convex shape mentioned above are same as the metal gasket 
having the symmetric convex shaped bead 3 and have been already explained 
with regard to FIG. 1. The example of such metal gasket is shown in FIG. 
12. This FIG. 12 corresponds to FIG. 4 and shows the cross-sectional state 
around the combustion chamber openings 6 and 6. 
FIGS. 13(a) and (b) correspond to FIGS. 5(a) and (b), and FIG. 13(a) shows 
the independent tracks of the inner sealing lines if around each 
combustion chamber opening and FIG. 13(b) shows the track of the outer 
sealing line 1j which surrounds each combustion chamber opening and draws 
the connected track when the bead 3' is merged at each point between 
combustion chamber openings. These FIGS. 12 and 13 show the case where the 
distance between the adjacent combustion chamber openings 6 is narrow. On 
the other hand, as shown in FIG. 14, in the case where the distance 
between the combustion chamber openings is wide, for compensating the wide 
distance between the combustion chamber openings 6, a compensating plate 5 
having approximately the same thickness as the portion 2a increased in 
thickness can be inserted between the outer periphery ends 2b of the 
portion 2a increased in thickness between the combustion chamber openings 
6. 
FIG. 16 is an another partial perspective view around the C-C' 
cross-sectional portion as shown in FIG. 14. The metal gasket as shown in 
FIG. 16 is a modified example of the metal gasket of FIG. 11, wherein the 
portions 2a and 2a increased in thickness are provided by the ring shaped 
supplementary plate under the plane plate portions 1a and 1a in the 
concave side of the bead 3. Also in this case, the compensating plate 5 
can be inserted between the outer periphery ends 2b and 2b of the portion 
2a and 2a increased in thickness. 
Further, various examples of the metal gasket having the above mentioned 
non-symmetric convex shaped bead 3' are shown in FIGS. 17 to 32. Each of 
these drawings shows the cross-sectional state around the combustion 
chamber opening. 
As for the metal gasket as shown in FIG. 17, the portion 2a increased in 
thickness by the ring shaped supplementary plate is placed on the base 
plate 1 in the concave of side the bead 3'. 
The metal gasket of FIG. 18 is similar to that of FIG. 17, wherein the 
portion 2a increased in thickness is provided along with the inner side of 
the concave shape of the bead 3'. 
In the metal gasket of FIG. 19, the supplementary plate 2 is provided on 
the base plate in the concave side of the bead 3' and is folded in the 
side of the combustion chamber opening to overlap, thereby forming the 
portion 2a increased in thickness. 
The metal gasket of FIG. 20 is similar to that of FIG. 11. 
As for the metal gasket of FIG. 21, a second supplementary plate 2' is 
provided on the concave side of the bead 3' and the portion 2a increased 
in thickness is overlapped between the second supplementary plate 2 and 
the base plate 1 in the side of the plane plate portion 1a. 
The metal gasket of FIG. 22 has two base plates 1 and 1 and has the shape 
in which one base plate is positioned on the gasket shown in FIG. 17 so as 
to sandwich the portion 2a increased in thickness between both base plates 
1 and 1. 
As for the metal gasket of FIG. 23, the second plane supplementary plate 2' 
is further overlapped under the base plate 1 in the metal gasket of FIG. 
19. 
As for the metal gasket of FIG. 24, the second plane supplementary plate 2' 
is further overlapped under the base plate 1 of the metal gasket of FIG. 
20. 
In the metal gasket of FIG. 25, one of two base plates 1 and 1 having the 
same shape of bead 3' is overlapped on the supplementary plate 2 of the 
metal gasket of FIG. 19 so as to sandwich the supplementary plate 2 
between two base plates 1 and 1. 
In the metal gasket of FIG. 26, a step 8a is formed by bending the side of 
the combustion chamber opening of the intermediate plate 8 to the upper 
side, the supplementary plate 2 is inserted into the concave side of the 
step 8a, and after the portion 2a increased in thickness is formed in the 
convex side of the step 8a, the base plates 1 and 1 having the bead 3' are 
positioned symmetrically to each surface side of the intermediate plate 8. 
In the metal gasket of FIG. 27, the portion 2a increased in thickness is 
provided under the intermediate plate 8 in the side of the combustion 
chamber opening, one base plate 1 having the bead 3' is provided under the 
intermediate plate 8 and the portion 2a increased in thickness, and 
another base plate 1 having the bead 3' is provided on the reverse side of 
the intermediate plate 8 so that the convex side of the bead 3' of another 
base plate 1 comes in contact with the side surface of the intermediate 
plate 8. 
The metal gasket of FIG. 28 is similar to that of FIG. 26 but the 
intermediate plate 8 has no step 8a in FIG. 26 and the supplementary plate 
2 is folded along with the edge in the side of the combustion chamber 
opening of the intermediate plate 8. 
The metal gasket of FIG. 29 is similar to that of FIG. 27 but the 
supplementary plate is folded along with the edge in the side of the 
combustion chamber opening of the intermediate plate 8. 
As for the metal gasket of FIG. 30, the thin intermediate plate 8 is bent 
to the upper side in the side of the combustion chamber opening and the 
supplementary plate 2 is provided on the upper side of the intermediate 
plate 8. Further, the supplementary plate 2 is folded to overlap under the 
intermediate plate 8 to form the portion 2a increased in thickness and an 
auxiliary plate 7 of a thickness thinner than the portion 2a is provided 
under the intermediate plate 8. 
The metal gasket of FIG. 31 is similar to that of FIG. 29 but the 
intermediate plate 8 is thinner and an auxiliary plate 7 is positioned 
under the intermediate plate 8. 
In the metal gasket of FIG. 32, the supplementary plate 2 is folded and 
overlapped to the upper and the lower surface of the plane and thin 
intermediate plate 8 to form the portions 2a and 2a increased in thickness 
and the auxiliary plates 7 and 7 having a smaller thickness than the 
portions 2a are provided in the upper and lower sides of the intermediate 
plate 8. 
Every metal gasket as shown in FIGS. 17 to 32 has the construction of 
overlapping the portion 2a increased in thickness to the plane plate 
portion 1a in the side of the combustion chamber opening 6 and in the 
concave side of the non-symmetric bead 3' formed in the base plate 1 and 
every metal gaskets have the same effect as that shown in FIG. 11. And 
particularly, examples shown in FIGS. 22, 25 to 32 having two base plates 
can receive wider height change and are preferable to use engines wherein 
the gap clearance changes widely by the combustion gas pressure. 
As for the method of connecting the components of the above mentioned metal 
gaskets, spot welding, seam welding, laser welding, adhesion, etc. can be 
applied besides a folding and calking method. Further, when a 
heat-resistant rubber such as nitrile rubber and fluorine-contained rubber 
is coated to both surfaces of the gasket facing the cylinder head and the 
cylinder block, and preferably also to other surfaces of the gasket 
components, it is possible to adsorb process marks and flaws on the 
intersurfaces of the cylinder head and the block and to improve the 
sealing function therebetween.