Acoustics – Sound-modifying means – Housing or enclosure
Reexamination Certificate
2001-02-14
2004-11-16
Lockett, Kimberly (Department: 2837)
Acoustics
Sound-modifying means
Housing or enclosure
C181S294000, C296S039300, C296S211000
Reexamination Certificate
active
06817441
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a foam member having shape memory property. Especially, the present invention relates to a foam member used for fluid sealing, soundproofing, and thermal insulation and to a method of producing the same.
Further, the present invention relates to an engine noise-proof cover for the purpose of reducing noise made by a car engine.
2. Description of the Related Art
Various kinds of foam materials such as a urethane foam and silicon sealants such as liquid hardening sealant are widely used for fluid sealing, soundproofing, and thermal insulation in joints of buildings, industrial machinery, and automobiles. In order to obtain enough performances of fluid sealing, soundproofing, and thermal insulation, gaps between joints of structures need to be filled up with theses materials.
A conventional foam member are attached on a portion where a process such as fluid sealing, soundproofing, and thermal insulation is necessary (hereinafter, referred as a “processed portion”) in a compressed state, and the foam member fills gaps between joints by recovering the thickness with an elastic force of the foam member itself. However, since the conventional foam member recovers its original shape as soon as a pressure thereon is released, the foam member or an assembly using the foam member need to be attached on the processed portion with keeping the foam member compressed against its recovery force. Therefore, operatability of attachment is very low.
If the foam member is thin, the operatability of attachment is improved. However, the performances of fluid sealing, soundproofing, and thermal insulation becomes insufficient since gaps are generated between the structure and the foam member in the processed portion. Alternatively, the recovery force of the foam member at the compressed state can be decreased by using a soft foam member, but its effect is slight. On the contrary, since use of the soft foam member results in lowering strength of the foam member, a life of the foam member is shortened. Especially, the performance of fluid sealing becomes inferior. As discussed above, each performance of fluid sealing, soundproofing, and thermal insulation and the operatability of attachment were hardly accomplished at the same time. Therefore, a foam member satisfying each performance at the same time is demanded.
On the other hand, a sealant of liquid hardening type such as a silicon sealant is also used. In the case of such a sealant, a material in liquid form is poured into gaps of the processed portion, and the gaps are filled by hardening the material with a chemical reaction or volatility of a volatile material such as a solvent. However, the sealant of liquid hardening type necessitates a long time for a sealing operation, and it takes a long time for hardening the material itself.
According to Japanese published examined patent application Sho. 48-1903, an elastic synthetic resin impregnated with a viscous resin composite is compressed, and the resin is restored with using hysteresis of time-recovery in order to fill a gap. However, since this method necessitates a complicated process such as impregnation of a viscous resin composite, the cost becomes high.
According to Japanese published unexamined patent applications Hei. 10-110059 and 9-132668, a shape-recovery foam element consisting of a closed-cell resin foam element is disclosed. However, there is a problem that enough performances of fluid sealing, soundproofing, and thermal insulation cannot be obtained immediately since this foam element necessitates a long time, e.g. dozens of days, for recovering the original shape.
Japanese published examined patent application Hei. 7-39506 (JP-B-7-39506) discloses a shape-memory polymer foam element made of urethane, and Japanese published unexamined patent application Hei. 9-309986 (JP-A-9-309986) discloses a shape-memory vulcanized rubber molding in which rubber is blended with resin. Further, it is known that polynorborenene and styrene-butadiene copolymer can be made as a shape memory polymer; therefore, a foam element having a shape recovery characteristic can be obtained with these materials. However, in order to produce the foam element with a shape recovery characteristic, some specific materials, which is difficult to obtain, are necessary, and special producing plants are also necessary. Therefore, this kind of foam elements is not widely used.
Hereinafter, a conventional engine soundproof cover is discussed in detail.
In order to prevent noise generated from a car engine, the engine is usually covered with an engine soundproof cover. For example,
FIG. 1
is a perspective view showing an engine soundproof cover
10
for use in a V-type engine
20
. The engine soundproof cover
10
is formed so that a foam member
12
is provided as a soundproof member substantially all over the engine-side surface (inner surface) of a cover body
11
made of metal or resin. The engine soundproof cover
10
is fixed to fastening holes
15
provided in an intake manifold
13
, an intake collector
14
, and the like, by bolts (not shown).
In addition, the shape of the engine
20
is complicated. Accordingly, the engine soundproof cover
10
is attached to the engine
20
in the state where the foam member
12
is compressed in the direction of its thickness. Then, the thickness of the foam member
12
is recovered by an elastic force of the foam member
12
itself so as to fill up a gap between the cover body
11
and the engine
20
. Thus, the soundproof effect is enhanced. However, usually, the foam member
12
recovers its thickness immediately as soon as the pressure is released. It is therefore necessary to attach the engine-proof cover
10
to the engine
20
while keeping the compressed foam member
12
in the compressed state against the recovery force of the foam member
12
. Thus, the operatability of attachment is very low.
If the foam member
12
is made thin, the workability on attachment is improved. However, there appears a gap between the foam member
12
and the engine
20
so that the soundproof performance becomes insufficient. Although the recovery force from the compressed state can be lowered by use of a soft foam member
12
, the effect is slight. If anything, reduction in the strength of the foam member
12
caused thereby leads to a problem such as shortening of the life.
Although it is also considered to mold the foam member
12
in accordance with the shape of the engine
20
, it is necessary to prepare the foam member
12
for every kind of engine
20
and for every attachment place if such foam members
12
are attached to a plurality of places of the engine
20
. Thus, the product cost is increased. In addition, because the foam member
20
is not brought into pressure contact with the engine
20
, it is inevitable to generate a gap, though it is small, between the foam member
12
and the engine
20
. Thus, there is a problem also in the point of view of the soundproof performance.
SUMMARY OF THE INVENTION
In view of the above circumstances, a first object of the present invention is to provide a foam member which is excellent in performances of fluid sealing, soundproofing, and thermal insulation, is excellent in the operatability of attachment to the processed portion, and is obtained at low cost without requiring a special material and equipment for producing.
Further, as discussed above, since the operatability of attachment of the engine soundproof cover to the engine is incompatible with the soundproof performance thereof. It is therefore a second object of the present invention to provide an engine soundproof cover which is excellent both in operatability of attachment and soundproof performance.
The inventors of the present invention made diligent investigation to solve the foregoing problem. As a result, the present inventors reached the following discovery. If a shape recovery foam member of the present invention is treated with the specific process which does not require specia
Murakami Atsushi
Nishimoto Kazuo
Niwa Takahiro
Lockett Kimberly
Miller Patrick
Nichias Corporation
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