Land vehicles – Wheeled – Attachment
Reexamination Certificate
1999-05-12
2001-09-04
Johnson, Brian L. (Department: 3618)
Land vehicles
Wheeled
Attachment
C280S736000
Reexamination Certificate
active
06283505
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a gas generator for air bags (hereinafter it is simply referred to as “gas generator”) for use in an air bag system for safely protecting a driver and riders in a vehicle from shock from collisions. Particularly, the present invention relates to a gas generator of cost efficiency having capabilities of maintaining the performance capability of preventing slag in a gas flowing outside.
BACKGROUND ART
The gas generators of this type include the one having a housing construction of the so-called single cylinder type and the one having a housing construction of the so-called double cylinder type. These housing constructions include a welded one and a friction welded one. Either of these two types of gas generators have the following fundamental construction. That is to say, these gas generators have a housing formed by a side cylinder having a plurality of gas exhaust openings; an upper cap closing an upper end of the side cylinder; and a lower cap closing a lower end of the side cylinder. The housing contains therein an igniter, gas generating agents, and a cooling/filtering member, which are arranged in this order from the center of the housing in a radially outward direction. The cooling/filtering member is formed to enclose the gas generating agents, extending from the upper cap side to the lower cap side.
In the gas generator having this fundamental construction, pressure of the gas generated in the housing rises instantaneously to inflate an air bag at the time of activation of the gas generator, according to the types of gas generating agents or burning conditions. As a result of this, looseness may occur in both end portions of the cooling/filtering member in abutment with the upper cap and the lower cap, then degradating the hermeticity of the cooling/filtering member at the ends abutting with the upper and lower caps, and as such may cause the slag in the gas to flow outside. The inventors of this application previously applied for a patent directed to a gas generator having the construction of preventing the slag in gas from flowing outside even when the gas pressure rises instantaneously (Japanese patent application No. Hei 8(1996)-207929).
Specifically, the previously proposed gas generator has, as shown in
FIG. 3
, a housing
33
composed of an upper container
31
having a side cylinder
31
b
having a plurality of gas exhaust openings
38
; an upper cap
31
a
closing an upper end of the side cylinder
31
b
; and a lower cap
32
a
closing a lower end of the side cylinder
31
b
. The housing
33
includes therein an igniter
70
having an ignitor element and an inflammation agent
72
sealed by barrier
35
, gas generating agents
36
, and a cooling/filtering member
37
, which are arranged in this order from the center of the housing to a radially outside thereof. The cooling/filtering member
37
is formed to extend from the side of the upper cap
31
a
to the side of the lower cap
32
a.
Further, the housing
33
has therein metallic foil
39
, bypass preventing members
45
,
46
and sealing members
40
a
,
40
b
. The metallic foil
39
adheres on an inner wall of the side cylinder
31
b
to cap the gas exhaust openings
38
from the inside. The bypass preventing members
45
,
46
are provided at the opposite ends of the cooling/filtering member
37
. The bypass preventing members
45
,
46
have a L-shaped section, contacting with an inner surface of the cooling/filtering member
37
at the opposite end portions thereof and with inner surfaces of the upper and lower caps
31
a
,
32
a
. To ensure the effect of preventing the slag from flowing outside, the sealing members
40
a
,
40
b
are provided at end surfaces of the cooling/filtering member
37
.
With the gas generator thus constructed, even when the gas pressure in the housing rises instantaneously to inflate the housing, since the bypass preventing members
45
,
46
are located at the opposite ends of the cooling/filtering member
37
, the slag in the gas can be prevented flowing outside. However, disadvantageously, the gas generator thus constructed has more parts and thus increased costs, due to the provision of the bypass preventing members
45
,
46
. Particularly in the circumstance in which specs on air bag systems are being standardized, cost reduction is being increasingly requested for gas generators, so cost increase resulting from the increase in component count is a significant drawback.
Accordingly, it is the object of the present invention to provide an improved gas generator at a low cost by improving the construction of inner surfaces of the upper and lower caps
31
a
,
32
a
to produce the function that is equal to or better than the function of the bypass preventing members
45
,
46
of preventing the slag in the gas from flowing outside through the cooling/filtering member
37
, thereby eliminating the need of the bypass preventing members
45
,
46
to provide reduction of component count and a resultant improved efficiency in assembling work.
DISCLOSURE OF THE INVENTION
A gas generator for air bags of the present invention comprises a housing formed by a side cylinder with a plurality of gas exhaust openings being closed at its ends by an upper cap and a lower cap; an ignitor, provided in the housing at a center portion thereof, to generate flame; gas generating agents, provided in the housing at a location radially outside of the ignitor means, to be burnt by the flame to generate gas; a cooling/filtering member provided in the housing at a location radially outside of the gas generating agents to enclose the gas generating agents and extending from the side of the upper cap to the side of the lower cap; and an annular projection member for preventing the gas generated by the burning of the gas generating agents from flowing toward an end portion of the cooling/filtering member, the annular projection being integrally formed on at least one of the upper cap and the lower cap so as to abut with an inner peripheral surface of the cooling/filtering member.
This produces the gas generator having, as compared with the gas generator as illustrated in
FIG. 3
, the feature that the bypass preventing members are replaced by the annular projection integrally formed with the upper cap or the lower cap, thus providing reduced component count as compared to the gas generator of FIG.
3
.
The annular projection has the same function of preventing the gas flowing toward the end portion of the cooling/filtering member as the bypass preventing members, and as such can allow a full amount of gas to pass through the entire cooling/filtering member except the end portion thereof. Further, when an instantaneous pressure rise occurs at the time of burning, the annular projection is pressed toward the cooling/filtering member, and as such can produce the operation and effect of a further increased degree of contact between the end surface of the annular projection at the outer diameter side thereof and the end surface of the cooling/filtering member at the inner diameter side thereof. This enables the slag in the gas to be prevented from flowing outside more reliably. This can achieve a gas generator having improved cost efficiency resulting from the reduced component count and the resultant improved assembling workability, while fully maintaining its performance capability of reliably preventing the slag in the gas flowing outside within a permissible range, without using any bypass preventing members shown in FIG.
3
and irrespective of the types of gas generating agents and the burning conditions.
The gas generator for air bags of the present invention may take the embodied form that the side cylinder and the upper cap are integrally formed and the side cylinder and the lower cap are joined to each other by friction welding, to thereby form the housing.
This embodied form provides the following result. When the housing is formed by friction welding, it is difficult to bring the side cylinder and the lower cap into full contact with each other
Kuroiwa Akihiko
Miyamoto Norihisa
Saso Takashi
Tanaka Koji
Fischmann Bryan
Johnson Brian L.
Nippon Kayaku Kabushiki-Kaisha
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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