Abstract:
An active bolster for an interior trim surface of an automotive vehicle has a plastic-molded outer trim panel with a closed-loop bonding 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 bonding flange along an peripheral edge, and a baffle section between the central attachment section and the bonding flange. The closed-loop bonding section and the bonding flange are configured to define a substantially closed toroidal region therebetween. An attachment body is molded in-situ to substantially fill the toroidal region. As a result of the in-situ molding of the attachment body in the toroidal region, the trim panel and bladder member become bonded via the attachment body resulting in a high bonding strength.

Description:
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 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 sealing 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 the sealing ribs, weld separation has continued to be a potential failure mode for active bolsters. 
     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 bonding 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 bonding flange along an peripheral edge, and a baffle section between the central attachment section and the bonding flange. At least one of the bonding section or the bonding flange includes a plurality of circumferential ribs. The bonding section and the bonding flange are intermixed in a hot weld region by melting them together. A spine member is insert molded into one of the bonding section or the bonding flange. The spine member projects between adjacent circumferential ribs, wherein the spine member is unmelted by the hot welding of the bonding section and the bonding flange so that the intermixing of the bonding section and the bonding flange encapsulates a projecting portion of the spine member in the hot weld region. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an outward-looking, exploded perspective view of a prior art active knee bolster glove box door system of a type to which the present invention can be applied. 
         FIG. 2  is a rear perspective view of an outer trim panel and bladder wall assembly of a prior art active bolster. 
         FIG. 3  is a perspective view of the prior art outer trim panel of  FIG. 2  with the bladder wall removed. 
         FIG. 4  is a cross-sectional view of a prior art welded joint between a trim panel and bladder wall. 
         FIG. 5  is a perspective view of one embodiment of a spine member having an I-beam cross section prior to insert molding into an outer trim panel. 
         FIG. 6  is a cross-sectional view of the spine member along lines  6 - 6  of  FIG. 5 . 
         FIG. 7  is a cross-sectional view of one embodiment of an outer trim panel, insert-molded spine member, and inner bladder wall prior to hot welding. 
         FIG. 8  is a cross-sectional view of the outer trim panel, spine member, and inner bladder wall of  FIG. 7  after hot welding. 
         FIG. 9  is a perspective view of another embodiment of a spine member having a T-shaped cross section. 
         FIG. 10  is a cross-sectional view of the spine member of  FIG. 9  along lines  10 - 10 . 
         FIG. 11  is a cross-sectional view of the spine member of  FIG. 9  insert molded in an outer trim wall. 
         FIGS. 12-14  are cross-sectional views of other embodiments of the spine member with other cross-sectional shapes. 
         FIG. 15  is a cross-sectional view of another embodiment of an active bolster wherein an outer trim wall and an inner bladder wall each has an insert molded spine member. 
         FIG. 16  is a cross-sectional view of the active bolster of  FIG. 15  with interlocking spine members after hot welding. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     Referring now to  FIG. 1 , a prior art active knee bolster system  10  has a base panel component  11  which forms the support structure or foundation for the bolster. Base  11  may be part of a glove box door which is attached to the vehicle by hinging from a storage cavity or glove box  12  as shown in  FIG. 1 . Alternatively, the active bolster can be mounted to another support structure such as an instrument panel support below a steering column, for example. Such locations interface to the knees of an individual riding in a corresponding seating position within a vehicle. The bolster may also be placed for protecting other body areas, such as a bolster mounted on a passenger door for torso protection. 
     Base  11  acts as a reaction surface for supporting an inflatable bladder formed by an inner wall (bladder member)  13  and an outer (trim panel) wall  14  that are joined around their periphery  15 . Walls  13  and  14  are preferably comprised of molded plastics (such as thermoplastic polyolefin (TPO)) and are joined by plastic welding, such as hot plate welding, to form a peripheral seal around a central region  17  for forming a bladder. An inflation gas source (i.e., inflator)  16  is electronically controlled for activating during a crash to release gas to inflate the bolster. Outer wall  14  may comprise the Class A interior trim surface such as the outside of the glove box door, or an additional skin or cover (not shown) can be applied to its outer surface. 
       FIG. 2  is a rear view of another prior art embodiment of an inflatable bladder  20 . A plastic-molded outer trim panel wall  21  overlies a plastic-molded, expandable inner bladder wall  22 . Walls  21  and  22  are joined around a closed perimeter region  23  to form an inflatable bladder having an open central volume between walls  21  and  22  to receive an inflation gas during a crash event from an inflator  24  mounted in a recess  25  of bladder wall  22 . Bladder wall  22  includes a plurality of pleats, such as  26  and  27 , to accommodate the expansion of bladder wall  22  during inflation. A plurality of bosses or towers  28  are used to mount bladder wall  22  to a vehicle support structure acting as a reaction surface. A welding flange  29  extends circumferentially around bladder wall  22 . Vent holes  30  comprised of an asterisk-shaped pattern cut through bladder wall  22  may 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. 3  shows outer wall  21  with the inner bladder wall removed revealing a bladder surface  31  that faces the inner wall when assembled. A plurality of upstanding ribs  32  follow closed perimeter region  23  and are joined with flange  29  of inner bladder wall  22  ( FIG. 2 ) by hot welding to create a hermetic seal for the inflatable bladder. Ribs  33  are provided for supporting the inflator. 
       FIG. 4  illustrates the welded joint between flange  29  and ribs  32  in greater detail. Due to the application of heat and pressure, ribs  32  preferably penetrate and bond with flange  23 . During inflation, outer wall  21  moves outward while pleat  27  unfolds. Bladder expansion results in forces applied to the weld that tend to peel apart the weld. 
     In order to avoid certain disadvantages of the known welded joints, the present invention employs a spine member which is insert molded into one of the walls to be hot welded, so that the spine member is incorporated into the hot weld region in a manner that strengthens the weld. 
     A first embodiment of a spine member  35  is shown in  FIGS. 5 and 6  formed as a circumferential ring with an I-beam cross-section. Spine member  35  is preferably formed of a metal such as stainless steel or aluminum or a nonmetal material which remains unmelted at the temperatures employed when hot welding the plastic bladder and trim walls. As shown in  FIG. 6 , the I-beam cross-section includes a lower or embedded plate  36 , an upper plate  37 , and a center webbing  38  between plates  36  and  37 . Spine member  35  has a ring shaped circumference in order to follow a weld track defined by circumferential ribs in one of the active bolster walls. 
     Preferably, the size of spine member  35  is adapted to fit inside a pair of adjacent circumferential ribs as shown in  FIG. 7 . Thus, outer trim wall  40  has a bonding section comprised of ribs  41  and  42  separated by an intervening gap  43 . Lower plate  36  of spine member  35  is insert molded during the manufacture of wall  40  so that spine member  35  projects between ribs  41  and  42  with upper plate  37  exposed (preferably remaining within the profile of gap  43 ). An inner bladder wall  45  has a bonding flange  46  to be hot welded with ribs  41  and  42  by the heating of adjacent areas  47  during a hot welding process. As known in the art, a hot weld plate or other heat source is placed between the bonding section (ribs  41  and  42 ) and bonding flange  46  to contact and melt the corresponding plastic material. Once melted or softened, the hot plate is removed and then walls  40  and  45  are compressed in order to intermix the melted plastic material. As shown in  FIG. 8 , the walls melt together by intermixing in a hot weld region  48 . Spine member  35  is unmelted so that intermixing of the plastic material from walls  40  and  45  encapsulates the portion of spine member  35  that initially projected between the circumferential ribs. Thus, upper plate  37  is encapsulated by intermixed material from walls  40  and  45  while lower plate  36  remains embedded in the portion of wall  40  that did not melt. The gap between adjacent ribs into which the spine member projects provides a space for the intermixing of the plastic material from both walls, thereby creating a weld with substantially increased strength as a result of reinforcement by the spine member. 
       FIGS. 9 and 10  shows another embodiment of a spine member  50  having a T-shaped cross-section. A center leg  52  is connected with an upper plate  51 . As shown in  FIG. 11 , center leg  52  is embedded by insert molding into an outer trim wall  53  between adjacent circumferential ribs  54  and  55  to project into a gap  56 , so that upper plate  51  is oriented toward a second wall (not shown) to be hot welded with ribs  54  and  55 . 
       FIG. 12  shows a variation in the cross-section of a spine member wherein a center webbing  60  couples a lower plate  61  and an upper plate  62 . Upper plate  62  has a pair of extensions  63  and  64  which are oriented to penetrate and grip into an intermixed region of hot welded plastic material that flows beneath upper plate  62 , for example. In a similar manner,  FIG. 13  shows an alternative embodiment wherein a center leg  65  connects with a curve upper plate  66  with angled extensions  67  and  68  to grip the intermixed plastic material of the hot weld to further increase the weld strength. 
       FIG. 14  shows another version of a spine member with a leg  70  integrated with a locking end  71 . End  71  has a deflection edge  73  and a ledge  72  which may be especially useful in an embodiment shown in  FIGS. 15 and 16  wherein spine members are utilized in both the outer trim wall and inner bladder wall to be hot welded in an interlocking manner. Thus,  FIG. 15  shows an outer trim wall  75  with circumferential ribs  76  and  77  and an intervening gap  78  to form a bonding section. A spine member  80  is insert molded with its locking end  84  extending into gap  78 . Inner bladder wall  82  has a bonding flange  82  into which a spine member  83  is insert molded so that an interlocking end  85  projects toward gap  78 . During hot welding, bonding flange  82  and ribs  76  and  77  are heated to their melting point and walls  75  and  81  are compressed with spine member ends  84  and  85  sliding along their angled faces until they snap together and become latched as shown in  FIG. 16 . Intermixing of the plastic material of the bonding flange and the circumferential rib bonding section of walls  81  and  85 , respectively, encapsulates the interlocked spine members. Thus, bonding strength of the hot weld region is even further increased. 
     Many other cross-sectional shapes of the spine member could be used, such as arrowhead or barbed shapes. The spine member preferably forms a circumferential ring in order to reinforce the entire weld track around the bladder for the active bolster. However, a spine member can also be used over only a smaller arc portion of the circumferential bonding area in order to reinforce just those areas where concentrated forces may increase the likelihood of weld separation.