Abstract:
The invention relates to an actuator subassembly for a vehicle safety system having a pin release actuator unit and a cradle bracket for holding the actuator unit and attaching to an airbag module. Further the invention relates to an airbag module with said actuator subassembly and a method of mounting a releasable tether on an airbag module by means of said actuator subassembly.

Description:
FIELD OF THE INVENTION 
     This application claims the benefit of U.S. Provisional Application 62/148,418, filed on Apr. 17, 2015. The disclosure of the above application is incorporated herein by reference. 
    
    
     The invention relates to an actuator subassembly with an actuator unit held in a cradle bracket. Moreover, the invention also relates to an airbag module of a vehicle safety system with the actuator subassembly as well as a method of mounting a releasable tether at an airbag module by means of the actuator subassembly. 
     BACKGROUND OF THE INVENTION 
     In the case of modern vehicle safety systems, especially in the case of airbag modules, it is endeavored to adapt the safety system more individually to different parameters of a crash situation. It is a known and advantageous possibility to make use of tensile means such as tethers, by release of which flow orifices are opened or closed. Moreover, by such tensile means also the airbag geometry can be influenced and an additional airbag volume can be released. 
     For the active release of a tether a so-called tether activation unit “TAU” is required. Such TAU are usually stressed for shearing by comparatively small shear force loads. For this reason, in WO 2007/065715 A1 for actuating a vehicle safety system pyrotechnic actuator units are made which have a plastic case and can be cheaply manufactured. 
     In WO 2007/065709 A1 an airbag module having an actuator unit in the form of a TAU is described in which a retaining means is provided to restrict the free mobility of a fragment separated after activation of the actuator unit. In this way, undesired contact with a vehicle occupant or damage of the airbag module by the separated fragment is largely excluded. 
     It is the object of the invention to provide a cheap and easily manufactured actuator subassembly that meets all safety requirements made to pyrotechnic actuators as regards movable components or fragments and at the same time can be easily mounted in a vehicle safety system. 
     SUMMARY OF THE INVENTION 
     An actuator subassembly for an airbag module has a pin release actuator unit and a cradle bracket for holding the actuator. The actuator unit has an actuator, a housing and a releasable pin for holding a looped end of a tether. The pin extends from one end of the housing. The actuator is housed inside the housing and configured to be connected at an opposite end to an electrical connection. 
     The cradle bracket has a “U” shaped housing part and a snap-on retaining clip, the “U” shaped housing part has an open first end, a closed second end with an aperture and a receiving chamber to accommodate the actuator unit disposed between said ends. Upon assembly of the actuator to the cradle, the actuator can move relative to the cradle bracket to receive a loop end of a tether, and when moved toward the closed end of the “U” shaped housing part, the releasable pin enters the aperture fixing said loop about the pin. The snap-on retaining clip has a pair of leg extensions fixing the actuator unit in the cradle. 
     The “U” shaped housing part has a plurality of feet projecting along the sides. The feet are configured to fit into apertures in a housing module to fix the actuator subassembly to the module on assembly. The actuator is, preferably, a pyrotechnic device and the releasable pin is released by actuation of the pyrotechnic device. This causes the pin to move through or withdraw from said aperture on actuation of the pyrotechnic device to release the loop of said tether. Prior to its activation, the actuator unit is undisplaceably attached to the cradle bracket. Inside the cradle bracket at least one stop is formed to restrict movement of the housing after activation of the actuator unit. The subassembly has a tether fixed to the pin of the actuator unit prior to activation of the pyrotechnic actuator unit. In the actuator, there is a pre-fabricated electric igniting unit including a pyrotechnic charge. The cradle bracket can be a plastic part. The actuator unit and cradle bracket are firmly connected to each other prior to activating the actuator unit. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will be described by way of example and with reference to the accompanying drawings in which: 
         FIG. 1A  is a top perspective view of the actuator subassembly of the present invention shown mounted on a portion of an airbag module plate. 
         FIG. 1B  is a bottom plan view of the actuator subassembly illustrating the actuator mounted into the cradle bracket of the present invention. 
         FIG. 1C  is an end perspective view of the cradle bracket and actuator showing the electrical connector end of the actuator of the present invention. The actuator subassembly being affixed to a portion of an airbag module plate. 
         FIG. 2A  is a perspective view of the actuator subassembly shown above an airbag module plate having a plurality of apertures for receiving the cradle bracket of the present invention. 
         FIG. 2B  is an illustration of the actuator subassembly positioned into the apertures on the airbag module plate. 
         FIG. 2C  is an illustration of the actuator subassembly wherein the retaining clip is pressed down into a locked positon onto the cradle bracket housing portion and the plate of the airbag module. 
         FIGS. 2D and 2E  show alternative looped ends of a tether. 
         FIG. 3  is an illustration of a retention foot on the cradle housing portion that is adapted to fit into an aperture on each side of the plate to help reduce any movement of the actuator subassembly when mounted to the plate. 
         FIG. 4A  is a perspective view of the cradle bracket without the actuator wherein the cradle bracket is shown mounted onto an airbag module housing. 
         FIG. 4B  is an end perspective view showing the cradle bracket mounted on the airbag module housing and affixed to the airbag module plate. 
         FIG. 4C  is a side perspective view of the cradle bracket mounted on the airbag module housing and affixed to the airbag module plate. 
         FIG. 5A  is a cut away view of an airbag with the vent in the closed position, pin puller not activated and tether engaged. 
         FIG. 5B  is a cut away view of an airbag with the vent in the open position, pin puller activated and tether disengaged. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     An airbag actuator subassembly  10  for an airbag module is illustrated in  FIGS. 1A-1C . As shown, the airbag actuator subassembly  10  has a pin release actuator unit  12  and a cradle bracket  40  for holding the actuator  12 . The actuator unit  12  has a housing  11  and a release pin  14  as illustrated. The cradle bracket  40  has a “U” shaped housing part  20  and a snap-on retaining clip  30  as illustrated. The “U” shaped housing part  20  is designed to hold the actuator  12  between sides of the actuator housing  20 . 
     The retaining clip  30 , as illustrated in  FIG. 2B , is shown in a pre-assembly position where it is retained by leg extensions  31  which act as locking arms on each side of the clip  30  that are designed to be held on protrusion  21  having upper and lower recesses  25 . The leg extensions  31  have a projecting tip  33  that engages the notches or recesses  25  in such a way it holds the retaining clip  30  in an unclipped and non-final assembly condition. In this position, the retaining clip  30  is extended slightly above the housing part  20  as illustrated in  FIGS. 2A and 2B . The housing  20  includes a ramp or rib  24  as illustrated. As the leg extension  31  is pushed down it moves out of the top notch  25  and starts to ride down the side of the adjacent wall of the housing  20 . However, as the leg extension  31  moves down the wall of the housing  20  that engages the ramp  24  until the leg extension  31  gets to the bottom of the ramp  24  where it moves in a manner to snap into the lower notch  25 . Once in the lower notch  25 , the leg extension  31  is prevented from moving out of the lower notch  25  because of an adjacent perpendicular surface of the ramp  24 . 
     In  FIG. 2C , when a downward pressure is applied, the retaining clip  30  moves inwardly such that the pair of legs  32  on the retaining clip  30  enter apertures  52  on the airbag module plate  50  in such a way that locks the retaining clip  30  into the module plate portion  50  as illustrated. When this occurs, the projecting tip  33  on the leg extension  31  enters the notch or recess  25  closest to the plate portion  50 . When this occurs, the subassembly  10  is in its final assembly configuration. A tether  200  shown in  FIG. 2C  can be mounted on the release pin  14 . The release pin  14  extends from the actuator  12  forward through a closed end wall  27  into an aperture  26 . When in this position, the cantilevered release pin  14  is supported not only by the actuator  12  held at the location  28  but also by the closed end wall  27 . This gives a full and complete support of the tether  200  to be restrained.  FIGS. 2D and 2E  show examples of looped ends  202  of a tether  200 . The tether  200  can be a thin rope that provides a quick reaction time when the pin  14  is pulled. A window  23  is provided on each side of the housing part  20 . This window  23  allows one to observe that the tether loop as illustrated is properly looped around the pin  14  on final assembly of an airbag. 
     The tether  200 , when restrained in this position, prevents the airbag from fully deploying or can be used to keep a vent either open or closed. However, when the actuator  12  is activated, the release pin  14  can either be pulled or pushed to create a free space such that it allows the tether loop to be free of the release pin  14 . Once this occurs, the tether  200  no longer restrains the airbag deployment or vents. 
     As shown in  FIG. 1C , the electrical connection end  16  is illustrated. At the top of the actuator  12  there is a slot  13 . This slot  13  provides an orientation direction such that when the actuator  12  is positioned into the cradle bracket  40  the slot  13  will be in a proper vertical positon as illustrated. This ensures that the electrical connection will always be made properly as it also has slide in features that allow this to occur. 
     With reference to  FIG. 2A , the actuator subassembly  10  is illustrated with a snap-on clip  30  in the upright extended position. In this position, the actuator  12  is free to move longitudinally forward or back as illustrated. Once the assembly is aligned with the apertures  52  on each side and  51  and  53  on the end, the projecting feet  29 A and  29 B on the housing part  20  are adapted to fit into the apertures  51 ,  52 ,  53  on the plate  50  as shown in  FIG. 2A . 
     As shown in  FIG. 2B , once the subassembly  10  is positioned on top of these apertures  51 ,  52 ,  53  the subassembly  10  is then moved directionally forward illustrated by the dashed arrow. When this occurs, the feet  29 A,  29 B are moved to a forward position within the plate  50  and are interlocked into the plate  50 . At this point, the subassembly  10  is still free to move backward from this forward position if desired and the actuator  12  can be moved backward to accept the tether loop about the release pin  14  as it will be pulled back allowing a tether loop to drop into the opening  20 A such that the actuator  12  when slid forward will pass the pin  14  through the loop thus securing the tether  200 . Once the pin  14  is pushed into the forward aperture  26  of the closed wall  27 . The tether  200  is no longer free to be disengaged until the actuator  12  is activated by a pyrotechnic device internal of the actuator housing  11 . When the device is in the fully forward position, the retaining clip  30  can be pushed downwardly, as previously mentioned, the legs  32  will then engage the aperture  52  on each side of the device and the leg extension  31  with the projecting tip  33  will engage the notch  25  closest to the plate  50  on each side of the bracket  40  as illustrated in  FIG. 2C . 
     In order to keep the subassembly  10  from vibrating or moving, a retaining leg  41  is provided. The retaining leg  41  fits in a narrow slot or aperture  53  on each side of the housing plate  50 . This retaining leg  41  has a projecting foot  41 A that engages the aperture  53  on the plate  50  and provides a tension on the device such that it cannot move forward or backward when locked in this position. As further illustrated, when referring back to  FIG. 2B , a tension leg  22  is provided that pushes on the actuator  12 . This tension leg  22  provides a spring loaded feature and creates a small downward force on the actuator  12  that helps preload the actuator  12  in such a fashion that it will not rattle inside the housing structure  20  or cause any vibrational noises. As can easily be appreciated, this cradle bracket  40  having a snap-on retaining feature  30  and an housing structure  20  as illustrated creates a simple way of holding a cylindrical type actuator device  12 . 
       FIGS. 4A, 4B and 4C  show the housing portion  20  and the retaining clip portion  30  mounted on an airbag module assembly  100 . The airbag module assembly  100  has the plate  50  shown in a more full view. The airbag module housing  100  has an opening  56  for receiving an airbag inflator and an airbag. A tether for the airbag would then be mounted on the actuator release pin  14  when the subassembly  10  is assembled onto the module  100 . The actuator  12  itself is not illustrated in these figures to show the simplicity of the cradle bracket  40  design and its unique way of attachment of the cradle bracket  40  to the plate  50 . 
     With reference back to  FIG. 1B , an underside view of the actuator subassembly  10  is illustrated. In this illustration, the retaining clip  30  shows the legs  32  on each side of the lower housing part  20 . The legs  32  project slightly inward and will be received in the plate  50  as previously discussed. Internal of the housing part  20  are illustrated projecting ribs  34 . These projecting ribs  34  project inwardly slightly from the housing and are designed to enter into notches  11 A that were formed into the actuator housing  11 . When these legs  34  engage the recessed notches  11 A on each side of the actuator  12  as the retaining clip  30  is pressed into full engagement this prevents the actuator  12  from moving longitudinally down its length. When this occurs, the release pin  14  is fixed into the aperture  26  as shown. In this condition, the actuator  12  and cradle bracket  40  are locked into a fixed position. Prior to being locked in this fixed position, a tether loop preferably is mounted onto the release pin  14 . When the actuator  12  receives an electrical signal through the connector  16  at the opposite end a pyrotechnic squib internal of the actuator housing  11  will be fired creating a chamber pressure that will either push the release pin  14  outward or pull the release pin  14  inwardly into the actuator assembly  10 . In doing so, as the release pin  14  moves longitudinally outward or inward, the opening  20 A where the tether loop is positioned will be free of the pin  14  in such a fashion that the tether  200  is released and the airbag can reach full deployment or a vent opened or closed if so desired. 
     With reference to  FIGS. 5A and 5B , in  FIG. 5A , the airbag cushion  102  has an internal tether  200  with a looped end  202  secured on the pin  14  of the pin puller assembly  10 . The tether  200 , when held by the pin  14 , holds a vent opening  103  closed at the opposite end. Under this condition, the inflation gases can fully inflate the airbag cushion  102 . In  FIG. 5B , the airbag cushion  102  is shown when the pin puller  10  has been activated retracted the pin  14  to release the tether  200  allowing the vent to open and inflation gases to escape. 
     Variations in the present invention are possible in light of the description of it provided herein. While certain representative embodiments and details have been shown for the purpose of illustrating the subject invention, it will be apparent to those skilled in this art that various changes and modifications can be made therein without departing from the scope of the subject invention. It is, therefore, to be understood that changes can be made in the particular embodiments described which will be within the full intended scope of the invention as defined by the following appended claims.