Stock material or miscellaneous articles – Coated or structually defined flake – particle – cell – strand,...
Reexamination Certificate
1999-01-14
2001-04-03
Robinson, Ellis (Department: 1772)
Stock material or miscellaneous articles
Coated or structually defined flake, particle, cell, strand,...
C428S035200, C428S141000, C428S156000, C280S731000, C280S728300
Reexamination Certificate
active
06210797
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to improvements of a casing for storing an airbag of an airbag restraint system which casing is adapted to b e deployed under the influence of high pressure gas from an inflator which is operated in response to impact at a vehicle collision or the like.
2. Description of the Prior Art
Conventionally, a variety of casings for storing an airbag have been known, in which polyurethane foam is used as its material in order to provide a soft feeling to the skin layer part of the casing which part constitutes an interior part of a vehicle. In these casings, a hard resin material or a net-like fibrous reinforcing material is used as a core layer in the casing in order that the casing tears only along a predetermined tearing line (a thin wall part) when the airbag operates as disclosed, for example, in Japanese Patent Laid-Open No. 63-232052.
However, drawbacks have been encountered in these casings, in which the casings are of a multi-layer structure and therefore is complicated in its fabrication process thereby lowering a yield or productivity and having a tendency that an unevenness is formed at the surface owing to an insert and a core layer used. Additionally, the casing in which the fibrous reinforcing material is inserted therein has a problem that the fibrous reinforcing material tends to shift in location during fabrication because of a low rigidity of the fibrous reinforcing material.
From viewpoints of solving this problem and lowering a production cost, it has been proposed to produce the airbag storing casing of a thermoplastic elastomer by an injection molding without using the above-mentioned insert, as disclosed, for example, in Japanese Patent Laid-Open No. 2-171364.
However, the thus produced casing has a thin wall section at its tearing portion of a lid member. Besides, the casing is in a structure in which the wall thickness continuously increases form the thin wall section of the tearing portion, so that the area of a thin wall is large.
As a result, this thin wall section tends to be affected by light and heat inside the vehicle, and therefore the physical properties and appearance of the casing is deteriorated with time.
In view of these problems, it will be supposed to form a decorative protecting layer or coating film at the surface of the casing. However, in case of using a polyolefin material as the material of the casing for storing an airbag, a so-called two-coat and two-bake manner or a so-called two-coat and one-bake manner are necessary to rigidly bond the coating film to the surface of the casing, thus increasing a production cost. In the two-coat and two-bake manner, a primer is first coated and dried, and thereafter a paint is coated and dried. In the two-coat and one-bake manner, a primer is coated, and then a paint is coated and dried.
In order to solve the above-discussed difficulties encountered in painting processes, the present inventors have proposed new materials for the airbag storing casing and for the coating film, suitable for a so-called one-coat and one-bake manner in which a paint is coated and dried, as disclosed in Japanese Patent Laid-Open No. 6-156178 and Japanese Patent Laid-Open No. 8-324371. In this type of airbag storing casings, as shown in
FIG. 1
, the airbag storing casing
1
has a coating
3
which is applied onto the main body
5
and the coating can inhibit the thin wall portion
7
at which the casing
1
is torn from being deteriorated with time. According to these proposals, an airbag storing casing which has good appearance and which can be torn surely even in a condition of low temperatures.
However, the process for preparing the paint and forming a surface layer for decoration and protection becomes troublesome, thereby increasing a production cost. Accordingly, an effort to lower the production cost becomes necessary.
SUMMARY OF THE INVENTION
With these problems in mind, it is therefore an object of the present invention to provide an improved airbag storing casing which can overcome drawbacks encountered in conventional airbag storing casings and suitably function so as to securely store an airbag therein and to effectively tear along predetermined lines and smoothly deploy when the airbag is inflated to protect vehicle occupant, having a single-layer structure without use of reinforcing insert.
It is another object of the present invention to provide an improved airbag storing casing which is possible, without a surface layer or a coat, to reduce deterioration of physical properties and appearance due to aging or exposure to ultraviolet light, so as to retain suitable conditions and ensure a smooth deployment of the airbag storing casing.
In order to achieve the above-mentioned object, a casing for storing an airbag for an airbag restraint system, according to the present invention, comprises: a main body formed of a material comprising a thermoplastic elastomer composition which is prepared by: mixing 100 parts by weight of a copolymer composition with 0.05 to 0.5 parts by weight of a higher fatty acid amide as a lubricant to obtain a mixture; and dynamically heat-treating the mixture in the presence of an organic peroxide and an auxiliary crosslinking agent, wherein the copolymer composition comprises: (A) 20 to 50 parts by weight of an olefin copolymer resin of propylene and one or two kinds of 1-olefin other than propylene; (B) 10 to 50 parts by weight of ethylene-propylene copolymer rubber having a Mooney viscosity (ML
1+4
, 100° C.) ranging from 30 to 60; (C) 10 to 70 parts by weight of ethylene-propylene-nonconjugated diene copolymer rubber having a Mooney viscosity (ML
1+4
, 100° C.) ranging from 50 to 100; and (D) 10 to 50 parts by weight of an oil-extended ethylene-propylene-nonconjugated diene copolymer rubber containing ethylene-propylene-nonconjugated diene copolymer having a Mooney viscosity (ML
1+4
, 100° C.) ranging from 150 to 350 and a mineral oil softener contained at an amount of 50 to 150 parts by weight relative to 100 parts by weight of the ethylene-propylene-nonconjugated diene copolymer.
According to the present invention provided also is a casing for storing an airbag of an airbag restraint system, comprising: a main body formed of a material comprising a partially crosslinked product from a mixture of 100 parts by weight of a copolymer composition and 0.05 to 0.5 parts by weight of a lubricant comprising higher fatty acid amide, with an organic peroxide for crosslinking the copolymer composition and an auxiliary crosslinking agent, wherein the copolymer composition comprises: (A) 20 to 50 parts by weight of an olefin copolymer resin containing a propylene moiety and a 1-olefin moiety other than propylene; (B) 10 to 50 parts by weight of ethylene-propylene copolymer rubber having a Mooney viscosity (ML
1+4
, 100° C.) ranging from 30 to 60; (C) 10 to 70 parts by weight of ethylene-propylene-nonconjugated diene copolymer rubber having a Mooney viscosity (ML
1+4
, 100° C.) ranging from 50 to 100; and (D) 10 to 50 parts by weight of an oil-extended ethylene-propylene-nonconjugated diene copolymer rubber comprising 100 parts by weight of ethylene-propylene-nonconjugated diene copolymer having a Mooney viscosity (ML
1+4
, 100° C.) ranging from 150 to 350, and 50 to 150 parts by weight of a mineral oil softener.
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Hamanaka Tatsuo
Ooyama Hiroshi
Sato Izumi
Sugiyama Tomokazu
Chevalier Alicia
Kilpatrick & Stockton
Nihon Plast Co. Ltd.
Robinson Ellis
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