Active bolster with interlocking gas barrier

An active bolster for an automotive vehicle has a plastic-molded outer trim panel with a closed-loop welding section. A plastic-molded expandable bladder member has a central attachment section, a welding flange along a peripheral edge, and a pleated region between the central attachment section and the welding flange. The welding section and the welding flange are joined by a hot weld. An inflator couples an inflation gas into a space between the trim panel and bladder member to expand the bladder member in response to a crash event. The bladder member includes a first blocking rib projecting toward the trim panel between the welding flange and the pleated region. The trim panel includes a second blocking rib projecting toward the bladder member. The blocking ribs mechanically interlock to resist separation of the bladder member and trim panel during expansion and to shield the hot weld from the inflation gas.

CROSS REFERENCE TO RELATED APPLICATIONS

Not Applicable.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH

Not Applicable.

BACKGROUND OF THE INVENTION

The present invention relates in general to active bolsters for occupant crash protection in automotive vehicles, and, more specifically, to increasing robustness of the bonding between an expandable bladder member and a trim wall which are separately molded.

An active bolster is a vehicle occupant protection device with a gas-inflatable bladder to absorb impacts and reduce trauma to occupants during a crash. As opposed to deployable air bag cushions that emerge from behind various openings upon inflation, active bolsters use the interior trim surface itself to expand at the beginning of a crash event for absorbing the impact and dissipating energy through the action of an inflation gas. U.S. Pat. No. 8,205,909, issued Jun. 26, 2012, incorporated herein by reference, discloses an active knee bolster integrated into a glove box door that is light weight and visually attractive. U.S. Pat. No. 8,474,868, issued Jul. 2, 2013, also incorporated herein by reference, discloses a typical structure wherein an active bolster includes an outer wall or trim panel that faces a vehicle occupant attached to an inner wall or panel along a sealed periphery. One or both of the walls is deformable in order to provide an inflatable bladder. For example, the inner wall (i.e., bladder wall) may have a pleated (i.e., accordion-like) region that straightens out during inflation. The walls are initially spaced apart by a small amount when in their pre-deployment, non-inflated condition. This allows ingress of the inflation gas in a manner that can achieve an even inflation across the panel.

The inner and outer walls of a typical active bolster are comprised of molded thermoplastics such as polyethylene, polyolefin, or PVC. They are typically injection molded but could also be blow molded. When formed separately, the walls must be hermetically joined around their periphery in order to form the inflatable bladder. The joint must be strong to resist separation as a result of the high pressures during inflation.

A known method of sealing the bladder walls is by hot welding, which involves heating of the matching surfaces and then compressing them together. Examples include hot plate welding, IR welding, and laser welding. A generally planar welding flange has been provided around the outer perimeter of an inner (bladder) wall which is received by a generally planar surface of an outer (trim) wall. The outer wall and/or inner surfaces may also include upstanding welding ribs that increase the weld strength by penetrating and fusing with the welding flange or other opposing surface during the hot welding process in which the areas to be welded are heated and then compressed. Despite the penetration of these ribs, weld separation has continued to be a potential failure mode for active bolsters for various reasons including warping of the parts to be welded, temperature variations of the hot plates during welding, uncorrected variances in the pressure applied during welding, and characteristic differences between the trim wall and bladder wall which may be molded from different plastic formulations.

Various stresses during inflation also contribute to the possibility of weld failure. Due to the elasticity required for making the pleated bladder wall inflatable, a significant peel stress may be applied to the weld seam during expansion. Another source of stress is the shock wave caused by the explosive initiation of gas flow from the inflator. Twisting and uneven bulging of the overall bladder structure during inflation can create stress or concentrate existing stresses at certain weld locations (e.g. along long straight edges of the weld).

SUMMARY OF THE INVENTION

In one aspect of the invention, an active bolster is provided for an interior trim surface of an automotive vehicle. A plastic-molded outer trim panel has a closed-loop welding section on an inside surface. A plastic-molded expandable bladder member has a central attachment section configured to attach to a support structure of the vehicle, a welding flange along a peripheral edge, and a pleated region between the central attachment section and the welding flange. The welding section and the welding flange are joined by a hot weld. An inflator couples an inflation gas into a space between the trim panel and bladder member to expand the bladder member in response to a crash event of the vehicle. The bladder member includes a first integrally-molded blocking rib projecting toward the trim panel between the welding flange and the pleated region. The trim panel includes a second integrally-molded blocking rib projecting toward the bladder member inside the welding section. The first and second blocking ribs mechanically interlock to resist separation of the bladder member and the trim panel during expansion and to shield the hot weld from the inflation gas.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Referring toFIG. 1, a plastic-molded outer trim wall10overlies an expandable inner bladder wall11with a welding flange12disposed at its outer perimeter and a pleated region with pleats13and14bending inward from flange12. This active bolster may comprise an active glove box door with a pivotable inner door panel17acting as a reaction surface to which bladder wall11is mounter.

Outer wall10has sealing ribs15that have been joined to welding flange12by hot welding. Inner wall11further includes a blocking rib16that extends from wall11between flange12and pleat13into abutment with outer wall10. Blocking rib16may preferably extend for a full circumference around inner wall11at an inside edge of welding flange12. Due to its abutment with outer wall10, blocking rib16restricts the flow of inflation gas against welding flange12that could otherwise cause the weld to separate and fail. Blocking rib16may extend substantially transversely with respect to flange12in order to contact outer wall10and make a good sealing contact to prevent inflation gas from entering the weld. Blocking rib16may preferably be substantially co-planar with a side of outermost pleat13. Even more preferably, blocking rib16may be compressed against outer wall10so that substantially no inflation gas flows past blocking rib16. Consequently, the inflation gas pushes against the weld in a direction transverse to sealing ribs15, which may correspond to the direction of greatest strength of the weld. In the event that displacement of pleat13during expansion causes blocking rib16to lose contact with outer wall10, blocking of the inflation gas is lost.

FIG. 2is a rear view of an active bolster20. A plastic-molded outer trim panel wall21overlies a plastic-molded, expandable inner bladder wall22. Walls21and22are joined around a closed perimeter region23to form an inflatable bladder having an open central volume between walls21and22to receive an inflation gas during a crash event from an inflator24mounted in a recess25of bladder wall22. Bladder wall22includes a plurality of pleats, such as26and27, to accommodate the expansion of bladder wall22during inflation. A plurality of bosses or towers28are used to mount bladder wall22to a vehicle support structure acting as a reaction surface. A welding flange29extends circumferentially around bladder wall22. Vent holes30comprised of an asterisk-shaped pattern cut through bladder wall22may be included for venting the central volume prior to and during deployment. Other kinds of vents, such as an active vent, can also be employed.

FIG. 3shows outer trim panel21with the inner bladder wall removed revealing an inner surface31that faces the bladder wall when assembled. A plurality of upstanding ribs32follow closed perimeter region23and are joined with flange29of inner bladder wall22(FIG. 2) by hot welding to create a hermetic seal for the inflatable bladder. Ribs33are provided for supporting the inflator.

FIG. 4illustrates an alternative embodiment for a blocking rib, wherein a bladder member40has a welding flange41and a first (radially outermost) pleat42. A trim panel43has a plurality of welding ribs44that penetrate and fuse with the heated plastic material of welding flange41. A circumferential blocking rib45is disposed radially inward from welding ribs44and likewise extends inwardly toward bladder member40. A hump48is preferably provided in bladder member40between welding flange41and pleat42to create a pocket46for accommodating blocking rib45, whereby blocking rib45bears against bladder member40at a position radially outward of the pleats in order to block an inflation gas shock wave47from reaching the hot weld between flange41and welding ribs44. During a welding operation when an active bolster is assembled, welding flange41is heated, welding ribs44may or may not be heated, and blocking rib45is not heated. Blocking rib45does not fuse with bladder member40(although the material of hump48may flow over blocking rib45filling or partially filling pocket46).

FIG. 5shows a first embodiment of an active bolster50of the present invention. A plastic-molded outer trim panel51has a closed-loop welding section53on an inside surface that receives a plastic-molded expandable bladder member52. Welding section53of trim panel51includes welding ribs54for penetrating and forming a hot weld57with a welding flange55of bladder member52. A pleated region56of bladder member52is disposed between welding flange55and a central attachment section (not shown). Hot weld57is formed in a known manner, including hot-plate welding and/or laser welding.

A blocking rib structure of the invention includes a first integrally-molded blocking rib60projecting from bladder member52toward trim panel51between flange55and pleated region56. A second integrally-molded blocking rib61projects from trim panel51toward bladder member52inside welding section53. Blocking ribs60and61are configured to mechanically interlock when trim panel51and bladder member52are brought together during hot welding. When interlocked, blocking ribs60and61will simultaneously A) resist separation of bladder member52from trim panel51during expansion, and B) shield hot weld57from the inflation gas that might otherwise tend to peel apart the weld.

FIG. 6shows trim panel51and bladder number52in the process of being hot welded together. Heat68is applied to welding ribs54and welding flange55(e.g. by contact with heated plates or illumination by laser radiation) prior to being pressed together by a fixture69. Blocking ribs60and61are not significantly heated, but are instead mechanically interlocked when panel51and bladder number52are pressed together as follows. Blocking rib60has an elongated wall62with a sloped end surface63projecting laterally from wall62to form an intermediate latching surface64. Blocking rib61is comprised of an elongated wall65having a complementary sloped end surface66and an intermediate latching surface67. Sloped end surfaces63and66slidingly engage when trim panel51and bladder number52are pressed together during formation of the hot weld. Walls62and65are sufficiently flexible to be deflected laterally until sloped surfaces63and66most past each other. Then, walls62and65move partially back to their original positions and intermediate latch surfaces64and67snap together and prevent ribs60and61from separating. The mechanical interlocking in which blocking ribs60and61continue to press against each other results in an airtight seal that blocks inflation gas from reaching hot weld57during bladder inflation in a crash event.

A blocking rib or ribs may or may not extend around the full perimeter of the hot weld. It may be desirable in some cases to extend the mechanically-interlocking blocking ribs along only a portion of the periphery of the hot weld (e.g., in just the areas that would otherwise be subject to a highest stress during expansion). For example, a typical weld seam may follows a generally-rectangular profile with a pair of long horizontal edges and a pair of short vertical edges. In an active glove box door, for example, the longer horizontal dimension of the generally-rectangular profile corresponds to the side-to-side distance necessary to accommodate both knees of a seated vehicle occupant. When the pleated material of a bladder elongates during inflation, a highest peel stress tends to occur at central portions of the long edges. Due to the higher stress, prior art bolsters have had an increased potential for weld failure along the central portions.

FIG. 7shows an inside surface of a trim panel70having welding ribs in a closed-loop welding section71. A blocking rib72preferably follows a complete closed-loop path disposed inside of welding section71, but may be configured for mechanical locking only at portions of the hot weld otherwise subject to a highest stress during expansion (i.e., along the long horizontal edges). Thus, blocking rib72has vertical side portions73and74that lack mechanical interlocking and horizontal top and bottom portions75and76configured for mechanical interlocking with complementary mating ribs on a bladder member (not shown).

FIG. 8shows blocking rib portions74and75in greater detail. Interlocking portion75includes a sloped end77and a latching surface78. Non-interlocking portion74may have a height which is the same as portion75or may be taller (as shown by dashed lines74′) or shorter depending upon how it contacts the bladder member (e.g., whether it contacts a non-interlocking rib or whether it contacts a flat area on the bladder member).