Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B60—VEHICLES IN GENERAL
  • B60R—VEHICLES, VEHICLE FITTINGS, OR VEHICLE PARTS, NOT OTHERWISE PROVIDED FOR
  • B60R21/00—Arrangements or fittings on vehicles for protecting or preventing injuries to occupants or pedestrians in case of accidents or other traffic risks
  • B60R21/02—Occupant safety arrangements or fittings, e.g. crash pads
  • B60R21/16—Inflatable occupant restraints or confinements designed to inflate upon impact or impending impact, e.g. air bags
  • B60R21/23—Inflatable members
  • B60R21/239—Inflatable members characterised by their venting means
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B60—VEHICLES IN GENERAL
  • B60R—VEHICLES, VEHICLE FITTINGS, OR VEHICLE PARTS, NOT OTHERWISE PROVIDED FOR
  • B60R21/00—Arrangements or fittings on vehicles for protecting or preventing injuries to occupants or pedestrians in case of accidents or other traffic risks
  • B60R21/02—Occupant safety arrangements or fittings, e.g. crash pads
  • B60R21/16—Inflatable occupant restraints or confinements designed to inflate upon impact or impending impact, e.g. air bags

Definitions

• the invention relates to vent holes in flexible pressure vessel structures. Specifically, the invention relates to non-circular vent holes in airbags. Description of the Related Art
• Airbag vents are generally a circular hole (or perhaps two holes in some designs) usually located somewhere on the back panel of an airbag. These vents deflate the airbag by providing a path for the inflator gas to exit the airbag. The deflating airbag decelerates the occupant at an acceptable rate during an impact (i.e., pressure in the airbag increases as the
• the vent acts to relieve or better control the internal pressure.
• the airbag would generally be very stiff, leading to higher deceleration forces exerted on the occupant and would likely rebound the occupant into the seat, potentially causing whiplash injuries.
• the vent also quickly deflates the airbag in case of accidental deployment.
• the geometry of a vent has two primary design considerations. First, it must be a reasonably efficient shape to permit the inflator gas to flow through it.
• the circular vent was probably developed under this criterion, as it presents the optimum area to perimeter ratio for two-dimensional geometries.
• a second design criterion is an efficient structural shape, which is certainly dependent on the geometry and construction of the particular airbag.
• the non-circular shapes described below attempt to present a geometry which is both
• the vent is a geometric discontinuity in the fabric membrane and presents a stress concentration as the airbag is pressurized (i.e., the vent is a
• Shear stress (which is detrimental to the fabric structure) is necessarily induced in the fabric surrounding the vent as the fabric distributes the loading to account for the missing fabric.
• vent hole increases the flexibility of the airbag structure, which causes the fabric around the hole to stretch. At some point during this stretching, the fabric will begin to resist. The fabric, however, has only a limited amount that it can stretch before failure. The inventors have found that the fabric surrounding the vent hole stretches quite easily as the hole is initially deformed from a circle to an ellipse. Only after it has been initially deformed, does
• the constructed vent geometry is similar to the strained vent geometry during the actual deployment, then the induced stress can be significantly less.
• Fig. 1 illustrates an elliptical vent hole according to one embodiment of the invention.
• Fig. 2 illustrates a diamond shaped vent hole according to a second embodiment of the invention.
• Fig. 3 illustrates an inverted triangular shaped vent hole.
• Fig. 4 illustrates a triangular shaped vent hole.
• Fig. 5 is a rear view of an airbag having an elliptical vent hole.
• Fig. 6 is a rear view of an airbag having an inverted triangular shaped vent hole.
• Fig. 7 illustrates a vent hole having dimensions selected in accordance with the orthotropic properties of an airbag material.
• the fabric is positioned to carry load more efficiently, removing the flexibility required to transition from the circular hole to the ellipse.
• the fabric already being in the "deformed" condition
• vent hole shape need not be
• a slit, rectangular or any generally elongated shape will also provide immediate, continuous resistance to stretching and tearing.
• the direction of elongation will preferably be in the direction parallel to the axis of lowest modulus of elongation (normally between the warp and fill, or weaving directions).
• Figure 5 shows a generally square airbag.
• the greatest elongation is generally parallel to the axial direction of inflation (i.e., in the direction of the driver as the airbag inflates). It is possible, however, and within the scope of this disclosure, that the greatest elongation may be encountered in some other direction. This would typically depend on the
• the ellipse is advantageous from the standpoint that the smooth, continuous periphery does not present stress concentration regions like the corners of a rectangle or the ends of a slit.
• the rectangular corners or slit's edges may, however, be rounded to decrease the stress concentration factors at these regions.
• the long axis of the ellipse is oriented toward the bias
• the diamond shaped vent geometry shown in Figure 2 takes advantage of a different strengthening mechanism and parallels the warp and fill directions of the fabric weave.
• the inventors apply a principle of orthogonality for load bearing on the vent region similar to that applied to the main diagonal seams of the airbag.
• the diamond is oriented such that the wa ⁇ and fill construction directions are normal to the "flats" of the diamond. This design forces the fabric to carry load in its optimum configuration — in the direction of the
• the corners of the diamond shape may also be rounded to minimize the tendency of fabric structures under stress to tear at a sharp corner.
• triangle and inverted triangle shapes (with rounded corners) shown in Figures 3 and 4 also have edges which parallel the fabric wa ⁇ and fill lines and provide an acceptable
• the inverted triangle provides a shape similar to the constructed geometry of the airbag shown in Figure 6.
• the initial shape of the vent may not be as symmetric as the previously shown examples. That is, assuming the fabric experiences greater elongation along the wa ⁇ direction, the diamond shape (for example) may be initially more rectangular than square, so that the final deformed shape is symmetric.
• the initial shapes of the vent can be determined by scaling the vent dimensions according to the
• the elliptical geometry was constructed with a major axis of 28.5 mm and a minor axis of 20.1 mm (i.e., approximately a 45°ellipse).
• the diamond geometry was constructed as a 22 mm square, however, the corners were rounded with a 5 mm radius. Both vent geometries were reinforced
• vent holes of the instant invention may take on many sizes and shapes, so long as they take advantage of one or both of the strengthening mechanisms described herein.
• circular vent holes may also be used in heavy or intermediate-weight fabric airbags.

Landscapes

• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Air Bags (AREA)
• Mattresses And Other Support Structures For Chairs And Beds (AREA)

Priority Applications (4)

Applications Claiming Priority (4)

Publications (2)

Family

ID=26693962

Family Applications (1)

Country Status (8)

Cited By (3)

Families Citing this family (4)

Citations (6)

• 1997
  • 1997-06-25 CA CA002259373A patent/CA2259373A1/en not_active Abandoned
  • 1997-06-25 CN CN97197495A patent/CN1228740A/zh active Pending
  • 1997-06-25 JP JP10504178A patent/JP2000514014A/ja active Pending
  • 1997-06-25 WO PCT/US1997/010492 patent/WO1998000313A1/en not_active Application Discontinuation
  • 1997-06-25 EP EP97933145A patent/EP0907528A1/en not_active Withdrawn
  • 1997-06-25 KR KR1019980710990A patent/KR20000022542A/ko not_active Application Discontinuation
  • 1997-06-25 BR BR9710084A patent/BR9710084A/pt not_active Application Discontinuation
  • 1997-06-25 AU AU36408/97A patent/AU3640897A/en not_active Abandoned

Patent Citations (6)

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