1. The Field of the Invention
The present invention relates to systems and methods for protecting vehicle occupants from impact. More specifically, the invention relates to a system and method for more tightly compacting an inflatable curtain module for installation in a comparatively narrow space.
2. Technical Background
The inclusion of inflatable safety restraint devices, or airbags, is now a legal requirement for many new vehicles. Airbags are typically installed in the steering wheel and in the dashboard on the passenger side of a car. In the event of an accident, an accelerometer within the vehicle measures the abnormal acceleration or deceleration and triggers the ignition of an explosive charge. Expanding gases from the charge fill the airbags, which immediately inflate in front of the driver and passenger to protect them from impact against the windshield. Side impact airbags have also been developed in response to the need for similar protection from impacts in a lateral direction, or against the side of the vehicle.
Typically, side impact airbags have a cushion that is mounted on or near the roof rail, or the portion of the frame that extends along the length of the vehicle between the side windows and the roof. The cushion is typically compacted, i.e., folded, rolled, or processed through a combination of folding and rolling, to stow the cushion behind a headliner covering the interior of the roof of the vehicle. The cushion may be designed to unfold or unroll downward to inflate beside a passenger to keep the passenger from hitting the door or window during lateral impact.
However, despite their enormous lifesaving potential, airbags, and particularly side impact airbags, have typically been limited to certain vehicles and configurations. In part, these limitations result from the fact that even after a mechanized compaction process, the cushion is often still quite bulky. Some more compact vehicles simply do not have the space to accommodate the bulk of currently available side impact airbags. Seatbelts are somewhat effective in restraining forward motion of an occupant, as in a head-on collision, but they leave a person more or less unprotected from sideways motion. As a result, people in compact vehicles are now unable to obtain any significant protection from lateral impact and rollovers.
Unfortunately, even in vehicles large enough to hold side impact airbags, it is difficult to properly mount and hide the airbags in the vehicle. Airbags mounted in a visible, accessible location are to be avoided because they are unsightly and may be tampered with by children and others. However, the space between the roof and the headliner is necessarily limited to minimize the profile of the vehicle.
The problem of finding adequate space to mount the compacted airbag is further exacerbated by the fact that traditional side impact cushions do not fold evenly. Typically, known cushions have a protection zone divided into chambers to control the size and shape of the cushion in inflated form. Often, the chambers are made vertical so that the cushion shortens horizontally during inflation, thereby tightening the cushion to provide more resilient side impact protection, particularly when the inflated cushion is not supported by a window.
Vertical seams normally separate the chambers from each other. The seams can be formed in a wide variety of ways, including weaving, adhesive or chemical bonding, thermal processing, and the like. Unfortunately, some seam formation methods tend to create a seam that is somewhat thicker than the surrounding material. Thus, when the cushion is folded or rolled for mounting on the roof rail, each seam stacks against itself to create a bulge in the compacted cushion. Such bulges increase the profile of the compacted cushion, thereby making it difficult or impossible to mount the cushion in the comparatively small space surrounding the roof rail.
Consequently, it would be an advancement in the art to provide a system and method for minimizing the profile of seams in compacted inflatable curtain modules. Preferably, such a system and method should be usable with current folding methods and machinery, and with current cushion manufacturing systems. Thus, the system and method should preferably consist of only a minimal change in the design of the cushion.
The apparatus of the present invention has been developed in response to the present state of the art, and in particular, in response to the problems and needs in the art that have not yet been fully solved by currently available inflatable curtain modules. Thus, the present invention provides a cushion for an inflatable curtain module in which the seams are angled and displaced from each other so that seam overlap is minimized. The bulk of the seams can thus be spread relatively evenly along the length of the compacted curtain.
In one embodiment of a cushion for an inflatable curtain module, the cushion has a top edge configured to be attached to a roof rail, a bottom edge, and a protection zone between the top and bottom edges in which inflatable chambers are separated by interior seams. The bottom edge can be compacted, i.e., folded or rolled, toward the top edge in a compaction direction to convert the cushion into a comparatively long, thin structure.
The interior seams are positioned at an angle with respect to the compaction direction; the angle is selected such that the seam will not overlap itself along at least half its length. xe2x80x9cOverlapxe2x80x9d is the disposition of the interior seam such that the bulge created by the seam on one layer interferes with the bulge created by the interior seam, or by a different interior seam, in an adjacent layer.
Such an angle can be determined with reference to the length and width of each interior seam and the number of compaction cycles that will be applied to the cushion. A compaction cycle is, in the case of rolling, one roll (360xc2x0), or in the case of folding, two overlapping, 180xc2x0 folds.
In selected embodiments, the cushion is rolled, such that the angled interior seam forms a helical shape with a variable diameter when the cushion is compacted. Each helical shape has a plurality of turns. With a rolled cushion, if the angle is one-half the inverse sine of the quantity consisting of the number of compaction cycles multiplied by two and by a thickness of the interior seam and divided by the length of the interior seam, there will be overlap along approximately half the length of the interior seam. The angle is thus preferably somewhat larger, so that overlap occurs along less than half the length of the interior seam.
In certain embodiments, the angle is large enough that no overlap occurs along the entire length of the seam. Yet further, in certain embodiments, the angle is large enough that no portion of the seam faces any other portion directly through the entire thickness of the compacted cushion. In such an embodiment, there is no interference between interior seam portions in adjacent layers, and there is furthermore no interference between interior seam portions in nonadjacent layers.
If the cushion is folded, a somewhat similar method may be used to optimize the interior seam angles to reduce or avoid overlap. However, instead of the helical configuration, the angle of the interior seam may produce a somewhat zigzagged configuration, with zigzags that are either the same width or different widths, depending on the folding method used.
According to an alternative embodiment, multiple interior seams are provided, in which the angle of each interior seam is large enough that the helical shapes formed by the interior seams during rolling are nested, or interleaved. In such a configuration, the interior seams are preferably displaced from each other such that no overlap between one seam and the next occurs. A similar nested pattern may be obtained in a folded cushion.
According to another alternative embodiment, the interior seams may be arrayed perpendicular to the compaction direction. Thus, each interior seam is parallel to the length of the compacted cushion, and no overlap of any interior seam with itself will occur. However, the interior seams should then be carefully positioned with respect to each other to ensure that adjacent seams do not overlap.
If rolling is the selected compaction method, adjacent seams should thus be disposed at different angular positions with respect to the center of the compacted cushion. Indeed, if desired, the interior seams may be relatively positioned such that the angular thicknesses of the interior seams have no overlap with each other.
If folding is the selected compaction method, the interior seams may be similarly separated by a distance calculated to avoid overlap. In such a case, linear thickness, rather than angular thickness, may apply. The interior seams may simply be disposed such that the linear thickness of each seam does not overlap with that of its neighbor, or with that of any other interior seam, if desired.
In yet another embodiment, the seams need not be straight, but may be curved to more fully prevent overlap. If rolling is the selected compaction method, overlap is more likely among the tighter turns of the helix of the interior seam, i.e., toward the bottom edge of the cushion. Thus, the interior seam or seams may have a comparatively small slope proximate the bottom edge, and a comparatively large slope (a smaller angle with respect to the compaction direction) proximate the top edge. Thus, all of the turns of the helical configuration may be separated by an equal displacement.
These configurations serve to spread the bulk of the interior seams out relatively evenly along the length of the compacted cushion. Thus, the inflated shape and tension of the cushion can still be determined through the formation of chambers of the protection zone, without creating bulges in the compacted cushion from the interior seams. The design, manufacture, and compaction of the cushions is otherwise similar to methods utilized in the past; thus, the system and method of the present invention may be employed with little or no additional engineering and tooling costs for the cushion manufacturer.
These and other features and advantages of the present invention will become more fully apparent from the following description and appended claims, or may be learned by the practice of the invention as set forth hereinafter.