Land vehicles – Wheeled – Attachment
Reexamination Certificate
2002-03-26
2004-04-20
English, Peter C. (Department: 3616)
Land vehicles
Wheeled
Attachment
C280S743100
Reexamination Certificate
active
06722695
ABSTRACT:
The present application claims priority to Japanese patent application of Kobayashi et al, filed Mar. 29, 2001, No. 2001-097327, and Japanese patent application of Kobayashi et al, filed Oct. 24, 2001, No 2001-326365, the entirety of each is hereby incorporated into the present application by this reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an airbag for an airbag device and a method for manufacturing the airbag. The airbag device is mounted in the steering wheel of a vehicle or in the instrument panel in front of a passenger's seat.
2. Description of the Related Art
In the prior art, the airbag of the airbag device is provided with a vent hole for discharging an inflating gas from the airbag. This airbag is inflated to a predetermined shape by the inflating gas fed from an inflator. At this point, the inflating gas is then discharged through the vent hole from the airbag so that its internal pressure does not exceed a predetermined value.
The time for the airbag to expand to the predetermined shape is longer if the vent hole is opened from the beginning of expansion of the airbag. Therefore, the vent hole is preferably formed when the internal pressure of the airbag reaches a constant value or higher. This vent hole is formed, for example, by forming a group of slits in the peripheral wall of the airbag. This slit group is formed by arranging a plurality of slits intermittently along one line. In this slit group, portions which are designed to rupture between slits are ruptured to form the vent hole for discharging the inflating gas (as referred to Unexamined Published Japanese Utility Model Application No. 9-134).
In the airbag of the prior art, however, the peripheral wall itself is made of a woven fabric of a synthetic resin. Specifically, the woven fabric was formed by weaving warp and weft threads of a synthetic resin of polyester or polyamide. Moreover, the airbag has to be compactly arranged when it is mounted as the airbag device on a vehicle. Therefore, the airbag is folded and housed in the airbag holding apparatus.
If the airbag is folded in the condition with the slits being formed in the peripheral wall of the airbag, moreover, the warps and wefts around the slits may become frayed or shifted out of position. Among airbags, therefore, during the formation of the vent holes there may occur differences in the effective area of the vent holes or in the timing by which the vent holes open.
SUMMARY OF THE INVENTION
An object of the present invention is to solve the aforementioned problems. Specifically, the object of the invention is to provide an airbag for forming a vent hole by a rupturing portion designed to rupture and, more particularly, an airbag which can stabilize the effective area and the opening timing of the vent hole, and a method for manufacturing the airbag.
The above-specified object is achieved by an airbag of the present invention. An airbag of the invention comprises a peripheral wall, a slit group, a portion designed to rupture and a vent hole. The peripheral wall is flexible and has portions which can be melted and can be solidified. The slit group is arranged in the peripheral wall and includes a plurality of slits arranged intermittently along one line. The portion designed to rupture is arranged between the slits of the slit group. The vent hole is formed along the line of the slit group by the rupture of the portion designed to rupture. The vent hole when opened discharges inflating gas. Moreover, the airbag of the invention further comprises portions formed in the peripheral wall at the peripheral edges of the slits, these portions solidifying after being melted.
Even when the airbag of the invention is folded, the melt-solidified portions prevent the fray and dislocation of the warps and wefts of the woven fabric at the peripheral edges of the slits. Therefore, the length and the rupture strength of the portion designed to rupture between the slits can be kept constant for every airbag. As a result, the opening timing at the time of forming the vent hole can be stabilized for every airbag. Moreover, the arranging position of the end portions of the slit group can be clearly specified for every airbag. Therefore, the effective area of the vent hole can also be stabilized for every airbag.
In the airbag of the invention, therefore, the effective area and the opening timing of the vent hole to be formed by the rupture of the portion designed to rupture can be stabilized for every airbag.
If the melt-solidified portions are formed all over the slit peripheral edges, moreover, the shape holdability of the slits can be retained. Therefore, the inflating gas to leak from the narrow clearances within the slits in the course of expansion of the airbag can be controlled to be constant. As a result, the time period from the start to the end of expansion of the airbag can also be stabilized for every airbag.
In the airbag of the invention, for example, the peripheral wall includes a main body cloth and an applied cloth having the slit group arranged therein. The main body cloth has an arranging hole opened for exposing the slit group to a portion for forming the vent hole and in a smaller shape than the outer shape of the applied cloth. The applied cloth is integrated with the main body cloth, the slit group being visible from the arranging hole, by sewing its peripheral edge to the peripheral edge of the arranging hole.
In this airbag, tensile forces are countered by the sewn portions of the peripheral edges of the applied cloth, even if they act on the peripheral wall at the peripheral edges of the applied cloth at the expansion time. Before the internal pressure of the airbag reaches a predetermined value (that is, before the vent hole is properly opened), therefore, it is possible to prevent a premature rupture at the portion designed to rupture on the applied cloth. As a result, the timing for forming the vent hole can be more stabilized for every airbag.
In the airbag of the invention, moreover, the peripheral wall includes a main body cloth and an applied cloth. The applied cloth is arranged over the main body cloth at a portion for forming the vent hole, by sewing its peripheral edge. The slits are individually cut through the applied cloth and the main body cloth. Moreover, the melt-solidified portion is formed by melting and fusing the applied cloth and the main body cloth to each other and then solidifying.
In this airbag, too, around the portion for forming the vent hole, there is formed the sewn portion in which the peripheral edge of the applied cloth is sewn to the main body cloth. Like the aforementioned airbag, therefore, even if pulling tensile forces act on the peripheral wall at the peripheral edges of the applied cloth when the airbag expands, the tensile forces are countered by the sewn portions of the peripheral edges of the applied cloth. Before the internal pressure of the airbag reaches a predetermined value, therefore, it is possible to prevent a premature rupture at the portion designed to rupture. It is also possible to stabilize the opening timing of forming the vent hole. Moreover, at the melt-solidified portions around the slits the overlaid applied cloth and main body cloth have been melted, fused thickly, and solidified together. In other words, the melt-solidified portions are formed to retain the highest shape holdability. Therefore, even if strong tensile forces act on the sewn portions at the peripheral edges of the applied cloth, i.e. the vent hole forming portion, in the course of expansion of the airbag, the portion designed to rupture does not rupture easily. As a result, premature rupture before the internal pressure of the airbag reaches the predetermined value is prevented as much as possible. It is also possible to further stabilize the opening timing at the vent hole forming time for every airbag.
Moreover, the line of the slit group may be bent and arranged in the peripheral wall so that the vent hole may be opened with a flap portion. The hinge
Kobayashi Hiroyuki
Mori Kenji
Sato Yuji
English Peter C.
Posz & Bethards, PLC
Toyoda Gosei Co,., Ltd.
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