Closure for an air bag deployment opening

Abstract: A closure arrangement for an air bag deployment opening (40) formed in an auto interior, including a closure panel (10) positioned in the opening (40) and hinged along one side (24), with a frangible lock on the other side opposite the hinge, fractured by pressure exerted by the deploying inflatable cushion. In a first embodiment, the frangible lock is defined by a tab portion (48) of a foam plastic core body (14) of the closure panel (10) protruding into a recess (50) formed in an adjacent structure (12), or an additional lock attached to the cannister, the tab (48) fractured by being sheared off after the inflatable cushion contacts an inside protuberance (64) projecting from the inside of the closure panel (10) or additional lock attached to the cannister; and, the hinge is provided by bending of an convoluted-shaped section (26) of a formed aluminum layer (18) defining the inner side of the closure panel (10). In a second embodiment, a molded plastic panel member has an inward frangible flange (116) with tabs secured to an air bag cannister (124) or instrument panel structure (104) to provide the lock, and the tabs are fractured by tensile loading created by deployment of the inflatable cushion. An inwardly directed integral hinging flange (118) is also adapted to be connected to the air cushion cannister (124) or instrument panel structure (104).

Description: This invention concerns a closure arrangement adapted to be operated by the deployment of an "air bag" through an opening in the interior structure of an auto, as in the instrument panel. A closure arrangement of this kind having the features given in the generic part of the main claim is described in DE-A1-38 00 652. Inflatable safety cushions, commonly known as "air bags", have been used as safety devices to protect the occupants of an automobile from injury as a result of a crash. The "air" bag is inflated with a gas very rapidly, as a collision is occurring to provide impact protection for an occupant. In the passenger side designs, the air bag deploys into the passenger compartment through an opening formed in the instrument panel while on the driver's side, a steering wheel housed compartment is used. The air bag safely absorbs the momentum of the driver or front seat passenger moving forward within the passenger compartment during a crash. The cushion is stored uninflated in a compartment, and a closure is required to cover the deployment opening until activation. Such closure must be securely and permanently locked closed to protect against tampering with the air bag components such as to cause a malfunction. Particularly, the closure should not invite the placing of objects into the air bag compartment since these could become lethal projectiles when the air bag is deployed. It is also desirable that the post deployment state of the closure provide a certain indication of the fact of deployment of the air bag. At the same time, the closure must operate very reliably to open when needed, almost instantaneously and in such a way as to not interfere with proper deployment of the air bag. Thus only smooth contours should be contacted by the bag during deployment, avoiding the presence of sharp projections. Since deployment of the air bag must be complete within only a few milleseconds, a typical requirement is that the closure must be open within 3 milliseconds, when operated by the pressure exerted by the air bag as it inflates, and thus a light weight structure is imperative. The system must operate very reliably over a wide range of temperatures and other environmental conditions. For example, a -40°C low and 105°C high temperature standards have been proposed corresponding to commonly used design criteria applied to other automotive components, which temperature standards have not heretofore been met for air bag deployment opening closures. For reliability and cost considerations, a simple design must be employed, utilizing a minimum number of parts. It is important that hazardous fragments from the closure itself should not be directed into the passenger compartment upon deployment. The closure arrangement of DE-A1-38 00 652 mentioned above has a closure panel member with an inwardly directed frangible flange extending along its side as a locking means having areas of reduced thickness which lie at the outer surface of a corner formed by the panel and the flange. This causes bending of the area of reduced thickness when the air bag deploys. The problem to be solved by the invention is to further enhance the reliability of a closure arrangement so that optimal effectiveness and reliable and consistent opening can be realized. The invention solves this problem by the features of the main claim. Advantageous further developments are described in the subclaims. The frangible flange depends from the inside of the panel member, and one or more areas of reduced thickness lie inward of the inside of the panel member. By this arrangement the areas of reduced thickness are in pure tension when the air bag deploys. This enhances the reliability of opening since any shearing effect is avoided. The closure panel is formed with an integral hinging section along one side which operates to not interfere with adjacent structures, and one or more frangible portions are provided along the other side which secure the closure panel in the closed and locked condition, but which fracture under the pressure exerted by an inflated air bag to allow the closure to be hinged open. One or more inwardly directed protuberances extend from the inside of the panel member, contacted by the deploying air bag so as to exert maximum opening pressure and reliably cause fracture of the frangible portion and hinging opening of the closure. The panel member is formed of a generally planar member having a series of inwardly projecting stiffening ribs in a direction extending from the opening to the hinged side of the panel. The member is also formed with downwardly projecting hinge and frangible flanges extending along the hinging and opening sides, but spaced inwardly, each secured to an air bag containing cannister. The frangible flange comprises a series of strips joined to the main portion of the ribbed member by a reduced thickness section junction, fracturing under the tensile stress exerted by the air bag pressing on protruding portions of the ribs located adjacent the opening side of the closure. The hinging flange is formed with grooves which allow it to buckle and enable the hinge side of the closure to move in and beneath the thickness of the adjacent structure, after which the closure is free to swing open without interference. An outer decorative layer matches the finish of the adjacent structure, and, a layer of soft foam padding over lying the panel member is used to match the less stiff feel of a surrounding padding as typically used in an instrument panel. FIGURE 1 is a sectional view of an installed closure according to the present invention, with the closure shown partially open in phantom. FIGURE 2 is an enlargement of the sectioned area 5-5 in FIGURE 1. FIGURE 3 is a plan view of the frangible flange portion of the closure of FIGURE 1, shown separated from the remaining portions thereof. FIGURE 4 is a plan view of the hinging flange portion of the closure of FIGURE 1 shown separated from the remaining portions. The invention will be shown used in a front passenger side air bag installation in the top of an instrument panel, but this is only by way of illustration, as the closure arrangement of the invention may be used with many different installations. The closure 100 is configured to be fit within a deployment opening 102 formed in the instrument panel 104 to cover the opening when in its normal closed position. The closure 100 also includes an inner contact surface 106 for the air bag, here provided by a molded plastic member having a generally planar layer portion 108, a series of stiffening transverse inner ribs 110 and outer webs 112 bridging a contour matching step 114 in the planer layer portion 108. The layer portion 108 also includes an integral frangible flange 116 and a hinging flange 118 extending inwardly from the inside of the closure 100, and parallel to the opening and hinging sides of the closure 100, but spaced inwardly thereof. The frangible flange 116 includes one or more tabs 120 integral with the layer portion 108, joined by reduced cross-section areas 122. The frangible flange 116 is fastened to an air bag containing cannister 124 by a strip portion 126 joining the tabs 120 at their ends opposite the ares 122. The strip 126 has a series of holes 128, each adapted to receive a fastener 130 securing the same to the side of the air bag cannister 124 beneath a clamping plate 137. The air bag cannister 124 is mounted beneath the instrument panel 104, aligned with the opening 102, by conventional structure not shown in FIGURE 1. The hinging flange 118 comprises a depending strip also formed with a series of holes 132 receiving fasteners 134 securing the same to the opposite side of the air bag cannister 124 beneath a clamping plate 135, with a strengthening rib 133 preventing tear out of the fasteners 134. A series of grooves 136 extend across the hinging flange to create a line of weakening to cause the hinging flange 118 to buckle, enabling the end 138 to snap under the adjacent structure of the instrument panel 104 as the opening end 140 lifts up, and thereafter enable free swing up of the closure 100 without interference. In this embodiment, a soft foam pad layer 142 overlies the rigid panel member 108, matching the less stiff feel of the conventional instrument panel pad. The outer layer is wrapped with a decorative vinyl layer 144, matching the vinyl layer 146 wrapped around the instrument panel 104. The ribs 106 extend out to create a protuberance adjacent the frangible flange 116, so that contact of the deploying air bag therewith is insured, establishing effective tensile breaking pressure on the areas 122. This produces reliable fracturing of the flange 116 and opening of the closure 100. Thus a tamper proof frangible lock has been provided for a hinged closure fit to a deployment opening, which is simple and yet has been found to be reliable over a wide range of temperature and other conditions. No projections are contacted by a deploying air bag, nor hazardous debris generated upon opening. A smooth outer appearance, and an opening free, tamper resistant exterior is also provided.

Claims: A closure arrangement (100) for an opening (102) defined within an auto interior structure, said opening (102) adapted to accommodate deployment of an inflatable safety cushion through said opening (102), said closure arrangement (100) comprising: a closure panel member (108) configured to be interfit into said opening (102); hinging means (118) operatively associated with one side of said closure panel member (108) to enable outward pivoting of said closure panel member (108) away from said opening (102); frangible locking means (116) extending along the other side of the said closure panel member (108) opposite said hinging means (118) and comprising areas (122) of reduced thickness, said frangible locking means (116) normally locking said closure panel member (108) to prevent hinging open of said closure (100), but fracturing free upon exertion of a predetermined outward pressure applied by said inflatable cushion as it begins to be deployed towards said opening (102); said closure panel member (108) comprises a molded plastic member having an integral, inwardly directed frangible flange (116) extending along said other side of said plastic panel member (108), characterized in that said frangible flange (116) depends from the inside of said plastic panel member (108) and is adapted to be secured to an air bag cannister (124), one or more areas (122) of reduced thickness lying inward of the inside of said molded plastic panel member (108) and being tensioned by deployment of said air bag so as to be fractured and release said other side of said closure (100). The closure arrangement according to claim 1 further including an integral hinging flange (118) extending inwardly and along said one side of said closure (100) adapted to be fastened to said air bag cannister (124). The closure arrangement according to claim 1 or 2 wherein said frangible flange comprises a series of spaced tabs joined to the molded plastic panel member at a junction therewith comprising said areas (122) of reduced thickness. The closure arrangement according to claim 1, 2 or 3 wherein said hinging flange (118) is formed with one or more grooves (136) extending across the width thereof to produce a line of reduced stiffness, enabling buckling of said hinging flange (118) and dropping of said one side beneath said adjacent interior structure. The closure arrangement according to anyone of claims 1 to 4 further including a soft foam pad (142) mounted atop said molded plastic member (108) The closure arrangement according to anyone of claims 1 to 5 wherein said molded plastic member (108) is formed with a series of elongated stiffening ribs (110) extending transversely from side to side. The closure arrangement according to claim 6 wherein said ribs (110) protrude downward to a greater extent on the end adjacent said frangible flange (116), whereby said air bag first contacts said end of said ribs (110) adjacent said frangible flange (116) upon deployment thereof.

Inventors: BAUER DAVID J, SISALVO ANTHONY J, BAUER, DAVID J., SISALVO, ANTHONY J., DISALVO, ANTHONY J.
Applicants: TIP ENG GROUP INC, TIP ENGINEERING GROUP, INC.
Application year: 1989
Main classification: B60R21
IPC codes: B60R21