Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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SEALING METHOD OF CONTAINER-SHAPED STRUCTURAL BODY
This invention concerns a sealing method for
a container-shaped structural body by means of a heat-
settable silicone rubber set between the fitting
surfaces of the parts of the container-shaped
structural body. In one embodiment of the method the
heat-settable silicone rubber is cast into one or more
longitudinal grooves in at least one of the fitting
surfaces.
Silicone rubber has excellent properties,
such as heat resistance, cold resistance,
weatherability, electrical insulating property, water
resistance, oil resistance, chemical resistance, etc.,
and has been widely used as a sealing material in
places where a high heat resistance and a high oil
resistance are demanded, such as between the oil pan
and crankcase of a diesel engine.
The application methods of the silicone
rubber can be roughly divided into two types. The
first type is the mold in-place gasket (MIPG) method in
which a gasket is molded by means of injection molding
using dies; the second is the cured in-place gasket
(CIPG) method in which the room-temperature curable
silicone rubber is coated in bead form on the fitting
surfaces of the oil pan, etc., that are to be sealed,
followed by setting in air to form the sealed portion.
In the former method, the MIPG method,
although the sealing effect is excellent, the gasket
has to be molded using an expensive injection molder.
This is unfavorable in regard to productivity and cost.
On the other hand, for the latter method, the CIPG
method, the operation can be performed at the site of
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assembly of the parts to be sealed without any
restrictions on the time and location; hence, the
productivity can be significantly improved. However,
for the silicone rubber a beaded coat, concavo-convex
profile, or wrinkles are formed so that the sealing
surface becomes uneven, and a sufficient sealing effect
cannot be realized.
The purpose of this invention is to solve the
aforementioned problems of the conventional methods by
providing a sealing method of a container-shaped
structural body, characterized by the fact that while
it is a CIPG method, it has an excellent productivity
and the container-shaped structural body formed has
excellent sealing property.
In a first embodiment of this invention, a
heat-settable silicone rubber is cast in bead form on
at least one of two fitting surfaces of a container-
shaped structural body. In a second embodiment of the
present invention, a heat settable silicone rubber is
cast in bead form into a longitudinal yroove located in
at least olle i:itting surface of the containel.-sl~a~ed
structural body. The surface of the silicone rubber is
then cured to a smooth state using a heated concave
die. Consequently, an excellent sealing effect can be
realized between the two fitting surfaces using this
cured-in-place method.
Figure 1 is a cross-sectional view
illustrating an example of a container-shaped
structural body (1) to be sealed by the method of this
invenlion.
Figure 2 is an oblique view illustratlng the
maln portion of a configuration of this invention at
the time that the uncured silicone rubber has been cast
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on one of the fitting surfaces, while heating of the
surface of the liquid-form silicone rubber by the die has
not yet started.
Figure 3 is an oblique view illustrating the
main portion of a configuration of this invention in
the state of heating/curing of the silicone rubber by
the die after the operation stage shown in Figure 2.
Figure 4 is an oblique view of the main
portion of a configuration of this invention in the
state ~t which the die is removed after the operational
stage shown in Figure 3.
Figure 5 is a cross-section view illustrating
an example of a container-shaped structural body to be
sealed by the method of this invention, where one of
the fitting surfaces contains a longitudinal groove
into which silicone rubber is cast.
Figure 6 i9 an oblique view illustrating the
main portion of a configuration of this invention at
the time that the uncured silicone rubber has been cast
into the groove formed on one of the fittin~ surfaces,
while heatillg of ths surface oE ~ l.iqt.~id ~iliCOrl~
rubber by the die has not yet started.
Figure 7 is an oblique view illustrat.illg the
main portion of a configuration of this invention in
the state of heating and curing of thesillcone rubber
by the die after the operational stage showll in Figure
6.
Figure 8 is an obligue view of the main
portion of a configuration of this invention in the
state A~ ~JhiCh ~he die is removed after thc operaiior,ai
stage shown in Figure 7.
This invention provides a sealing method of a
container-shaped structural body, characterized by the
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following facts: this sealing method is used for
sealing the fitting surfaces of a container-shaped
structural body that can be separated into at least two
parts that have the aforementioned fitting surfaces
facing each other. In one embodiment of this sealing
method, the aforementioned surfaces are formed in a
planar shape facing each other, and the uncured heat-
settable silicone rubber is cast in bead form on at
least one surface in the longitudinal direction. In a
second embodiment of this sealing method, one or more
of the aforementioned fitting surfaces has one or more
longitudinal grooves into which heat-settable silicone
rubber is cast. The surface of the aforementioned
heat-settable silicone rubber is molded and cured to a
smooth state by means of a heated concave molding die.
The surface of the aforementioned cured heat-settable
silicone rubber is then set in close contact with the
fitting surface of the other part.
In this method, when the cured-in-PlaCe gasket
~CIPG) method is implemented, ~fter the l~eat.-sett~ble
silicone rubber i~ cast in bead form o]l olle o~ tile
surfaces, its surface i6 cured to a æmooth st~te by a
heated concave molding die. Hence, the time can be
shortened, the productivity can be improved, and the
sealing effect can al50 be improved.
According to this invention, the contailler-
sh~ped structural body reîers to the part that has a
container shape and can be separated into at least two
portions, each of which has a fitting surface, with the
fitting surfaces o- the portions facing each other.
One or more of the fitting surfaces may have one or
more longitudinal grooves. Examples of the container-
shaped structural body include the oil pan of the
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diesel engine of an automobile, etc., ocker cover,
timing-belt cover, separation flask, and other types of
chemical-experiment ec~ipment, as well as other
assemblies consisting of at least two separable parts.
In the following, the sealing method of this
invention will be explained in more detail with
reference to figures. Figure 1 shows an example of a
first embodiment of a container-shaped structural body
sealed using the method of this invention. Container-
shaped structural body (1) is an assembly of main body
(2) and lid (2'). Their fitting surfaces (4),(4') are
formed in a planar shape with respect to each other. A
sealing material (3) made of the heat-settable silicone
rubber is formed in bead form on one fitting surface
(4) and is used to seal the area between fitting
surfaces (4),(4'). As shown in Figure 2, in this
sealing method with the aforementioned configuration,
unc~lred liquid-form silicone rubber (S) is cast in bead
form on fitting surface (4) of main body (2) in the
longitlld~tlal direction.
l'he suLfac~ of sa.id s.ilicone ~ bl~ ) ls
coveLed with heated dis (5) having a collcave pOLtiOII,
as ShOWtl in Figure 3, for molding to form a smootll
surface, while being cured under heating. The curillg
operation may be performed only for tlle s~lrface without
going into the interior. After die (5) is removed,
li~uid-form silicone rubber (S) has its surface molded to
form a smooth, convex sealing material (3); hence, when
lid (2') llas its fitting surface (4') set on top of it,
a perle~ aling state call be realizecl.
In a second embodiment of the present method,
one or more longitudinal grooves are formed in at least
one of the fitting surfaces. After the heat-settable
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silicone rubber is cast in bead form in the groove, itssurface is cured to form a smooth surface by means of a
heated concave die. Consequently, the surface of the
silicone rubber formed is smooth and located correctly
with respect to the fitting surface. When this sealing
method is used repeatedly there is no shift in position
of the CIPG of silicone, and thus a high durability seal
is made.
Figure 5 showæ an example of the container-
shaped structural body sealed using the embodiment of
the present method wherein positioning of the CIPG of
silicone is maintained at least partially by a
longitudinal groove in one of the fitting surfaces. In
Figure 5, container-shaped structural body (1) is an
assembly of main body (2) and lid (2'). On fitting
surface (4) of main body (2), a groove ~6) is formed in
its longitudinal direction. A sealing material (3)
made of heat-settable silicone rubber is formed in bead
form in said groove (6) and is used to seal main body
(2) and lid (2') between their fitting s~rfaces (4) and
(4').
Figure 6 further illustratefi t}le ~ea].j.ng
method with the aforementioned groove. In Figure 6,
groove (6) is formed in the longitudinal direction on
fitti.ng s~lrface (4) of main body (2), and ~mcured
li~uid-form silicone rubber (S) is cast in bead form in
groove (6). The surface of said silicone r~lbber (S) is
then covered with a heated die (5) having a concave
portion as shown in Figure 7 for molding onto a smooth
surfacc, ~:hile being cured wlder hea~ing. Thc curing
operation may be performed only for the surface portion
Wit]lOUt going to the interior, if desired. After die
(5) is removed, li~uid silicone rubber (S) has its
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surface molded into a smooth convex sealing material
(3) hence when lid (2') is set on top of it, a perfect
sealing state can be realized. Since groove (6) is
used to guide casting of the silicone rubber, the
silicone rubber can be set at the correct position to
realize precise sealing during the application process.
Therefore, even when lid (2') is set and removed
repeatedly, there is still no deviation in the position
of the CIPG of silicone and the durability of the seal
is thus good.
According to this invention, as shown in
Figure 6, the amount of the uncured silicone rubber
cast in the groove on the fitting surface should be
appropriate to ensure that the silicone rubber bulges
over fitting surface (4), yet stops below fitting
surface (4'). In this case, a convex portion should be
formed on fitting surface (4') of lid (2') so that it
can fit into groove (6) to compress the sealing
material (3). As far as the cross-sectional shape of
seali.ng material (3) is concerlled, in ~cldition to the
circular arc shape shown in the figure, a .sq~laLe
shaped cross-section or a polygon-shaped ClOSS-
section are also allowed.
According to this invention, there is no
special limitation on the type of silicone r~lbber to be
used, as long as it has the heat-setting property.
Examples of the silicone rubber that may be used
include vinyl-radical-containing diorganopolysiloxane;
the addition-reaction curing type silicone rubber
compositions .lith :~hc 5iiicon a~ln bondilly a hydroyerl-
atom-containing organopolysiloxane and a platinum
cataly~st used as the main ingredients; the
condensation-reaction curing type of silicone rubber
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com$ositions with the main ingredients including silanol-
radical-containing organopolysiloxane, methoxy-radical-
containing organopolysiloxane, organotin compound or
organotitanium compound and other condensing catalysts;
and the org~noperoxide curing type of silicone
c~sitions with the vinyl-radical-containing
diorganopolysiloxane and organoperoxide as its main
ingredients.
Among these, the addition-reaction curing
type of silicone rubber composition that has a fast
curing rate and that can be cured at a relatively low
temperature is preferred. The uncured silicone rubber
~ sitions with a viscosity at 25C of 100-200,000
poise, (10-20,000 Pa.s) preferably 2,000-20,000 poise,
(200-2,000 Pa.s) are used.
According to this invention, there is no
special limitation on the means for casting the uncured
silicone rubber c~sition in bead form. For example,
it may be extruded from a container having a noæ7,1s at
its tip, by means of compressed air or some other
pressing InealJs.
According to this invention, it is prefelled
that the die used for molding ths surface of the
uncured silicone rubber is made of a material having as
high a heat capacity as possible. The materials that
may be used include aluminum, SUS and other types of
carbon steel, cast iron, copper, etc. The heating
means may be incorporated, or set in the exterior using
electricity, gas, IR, rf, etc. As far as the degree of
curing OI the silicone rubber is concerned, at least
the surface has to be cured to a smooth state, while
the interior may be incomplete in curing as the flt.ting
surface of the other part is fit, or, it is also
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possible to perform fitting after the silicone
rubber is thoroughly cured. The curing temperature of
the silicone rubber is the temperature at which the
curing operation is started, and it is not specifically
limited. The curing temperature is usually within a
range of about 50-200C.
The following examples are provided to
illustrate the present invention.
Example 1. 100 parts by weight of
dimethylvinylsiloxy-radical-blocked
dimethylpolysiloxane with a viscosity at 25C (same in
the following) of 100 poise, (10 Pa.s) 3S parts by
weight of fumed silica with a specific area of 200
m2/g, and 5 parts by weight of hexamethyldisilazane
were uniformly blended, followed by heat treatment in
vacuum to form a liquid-silicone rubber-based material.
Subsequently, 100 parts by weight of the aforementioned
liquid-silicone rubber-based material were uniformly
blended with 6 parts by weight of trimethylsiloxy-
radical-blocked methylhydrogen polysiloxane (with the
content of the silicon-atom-bonded hydro~en atom of i . 5
wt %), 0.5 part by weight of a complex of
chloroplatinic acid and divinyltetramethyldi.siloxane
(with a platinum concentration of 0.4 wt ~), aIId 0.2
part by weight of 3,5-dimethyl-1-hexyne-3-ol used as
the curing inhibitor, forming a liquid-silicone rubber
composition with a viscosity of 15,000 poise (1,500
Pa.s).
The aforementioned liquid-silicone rubber
composition was used to seal seaiilly COCI~aiCler (ij
consisting of main body (2) and lid (2') as shown in
Figure 1. The silicone rubber composition was cast in
bead form on fitting surface (4) of main body (2) from
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a nozzle with a diameter of 2 mm set on the tip portion
of a cartridge under a pneumatic pressure of 6 kgf/cm2.
On the other hand, as shown in Figure 3, die (5) having
a semi-spherical cross section with a maxim~lm depth of
3.0 mm and a diameter of 3.5 mm was heated beforehand
for 30 minut~s in an oven at 150C. It was then set on
the surface of said liquid-silicone rubber composition,
and was then removed after heating to cure for 10 minutes
forming a sealing material with smooth surface (3).
Fitting surface (4') of lid (2') was set on said
sealing material (3). After sealing using bolts, the
pressure inside container (1) was increased, and the
pneumatic pressure at which the air started leaking
through the sealing portion was measured. The results
indicated that the air leakage took place when the
pneumatic pressure reached 7.0 kgf/cm2.
Example 2. For the purpose of comparison, a
container was sealed in the same way as in the
aforementioned application example, except that the
li~uid-silicone rubber c~sition cast on fitting
surface (4) of main body (2) was cured directl.i ~y
settlng for 10 min in an oven at 100nC. Whel~ the
interior of the container was pressurized, the
pneumatic pressure at which air leakage started from
the sealing portion was measured, and it wa~ found to
be 2.5 kgf/cm2.
Example 3. A liquid-silicone rubber
composition as described in Example 1 was ~lsed to seal
a container having a longitudinal groove in a fitting
~urf~ce d~ ~h~wn in ~iguSe 5. Referrin~ to Figur~ 6,
the silicone rubber composition was cast in bead form
into groove (6) with a width of 3.0 mm and a depth of
3.0 mm formed on fitting surface (4) of main body (2)
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from a nozzle with a diameter of 2 mm set on the tip
portion of a cartridge under a pneumatic pressure of 6
kgf/cm , with the bead bulging over fitting surface (4)
by a height of about 3.5 mm.
As shown in Figure 7, die (5) having a
semispherical cross-section with a maximum depth of 3.0
mm and a diameter of 3.5 mm was heated beforehand for
30 minutes in an oven at 150C. The die was then set on
the surface of said liquid-silicone rubber composition
(S), and was then removed after heating for curing for
~0 minutes, forming a sealing material with a smooth
surface (3).
Fitting surface (4') of lid (2') was set on
said sealing material (3). After sealing by means of
bolts, the pressure inside container (1) was increased,
and the pneumatic pressure present when the air started
leaking through the sealing portion was measured. The
results indicated that the air leakage took place when
the pneumatic pressure reached 7.0 kgf/cm2.
The sealing state of said container (1) was
then released by loosening the bolts. The container
was sealed again and pressurized in the same way as
above, and the pneumatic pressure present when air
started leaking was again measured. It was found that
this pressure was 7.0 kgf/cm2. It is thus determined
that there is virtually no difference in the sealing
effect as compared with the previous pressure test.
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