Patent Publication Number: US-2021170970-A1

Title: Actuator devices and assemblies for automotive safety devices

Description:
TECHNICAL FIELD 
     The present disclosure relates generally to the field of automotive protective systems. More specifically, the present disclosure relates to automotive safety systems that are configured to deploy in response to collision events. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present embodiments will become more fully apparent from the following description and appended claims, taken in conjunction with the accompanying drawings. Understanding that the accompanying drawings depict only typical embodiments, and are, therefore, not to be considered limiting of the scope of the disclosure, the embodiments will be described and explained with specificity and detail in reference to the accompanying drawings. 
         FIG. 1  is a perspective view of an interior of a vehicle with a passenger, wherein an airbag assembly has been deployed to a first configuration. 
         FIG. 2  is a perspective view of an interior of a vehicle with a passenger, wherein the airbag assembly of  FIG. 1  has been deployed to a second configuration. 
         FIG. 3A  is an isometric view of an actuator assembly according to one embodiment. 
         FIG. 3B  is an isometric view of an actuator assembly with an electrical insulation layer according to one embodiment. 
         FIG. 4A  is a cross-sectional view of the actuator assembly of  FIG. 3A  in a pre-actuation configuration. 
         FIG. 4B  is a cross-sectional view of the actuator assembly of  FIG. 4A  in a post-actuation configuration. 
         FIG. 5  is an isometric view of an actuator assembly encompassed in an over-mold according to an embodiment. 
         FIG. 6  is a cross-sectional view of the actuator assembly and over-mold of  FIG. 5 . 
         FIG. 7  is an isometric view of a tether release assembly that comprises an actuator assembly encompassed in an over-mold. 
         FIG. 8A  is a view of a tether release assembly in a pre-actuation configuration of an actuator assembly according to one embodiment. 
         FIG. 8B  is a view of the tether release assembly of  FIG. 8A  in a post-actuation configuration of the actuator assembly. 
         FIG. 8C  is a view of the tether release assembly wherein the tether is released. 
         FIG. 9  is a cross-sectional view of a tether release assembly according to one embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     It will be readily understood that the components of the embodiments as generally described and illustrated in the figures herein could be arranged and designed in a wide variety of different configurations. Thus, the following more detailed description of various embodiments, as represented in the figures, is not intended to limit the scope of the disclosure, as claimed, but is merely representative of various embodiments. While the various aspects of the embodiments are presented in drawings, the drawings are not necessarily drawn to scale unless specifically indicated. 
     During a vehicle collision event, one or more sensors provide data to an engine control unit (ECU) and/or airbag control unit (ACU), which determines if threshold conditions have been met for deployment of an automotive safety device such as an airbag (or a plurality of airbags). The ECU/ACU may cause an electrical pulse to be sent to an initiator of an automotive safety device. 
     Conventional initiators may comprise a pyrotechnic relay load that is ignited and heats or burns. The activation of an initiator may produce an effect or otherwise set in motion events to initiate operation of an automotive safety device. In the case of an airbag assembly, the initiator may ignite a chemical compound within an inflator of the airbag assembly. The chemical compound burns rapidly and produces a volume of inert gas that is directed to fill the airbag itself. In other airbag assembly embodiments, the initiator may produce a volume of gas that increases pressure within a compressed air chamber, thereby bursting the chamber and releasing a larger volume of inflation gas to fill the air bag. In still other embodiments, an initiator may initiate or otherwise produce another effect, such as cutting or releasing a tether, displacing a component, pre-tensioning a seat belt, and the like. 
     Attempts have been made to use conventional initiators to actuate mechanisms of automotive safety devices, or to otherwise deploy or actuate automotive safety devices. However, an initiator typically produces a gas and/or a flame which can prove detrimental in certain actuation scenarios. The present disclosure describes embodiments of actuator assemblies that include similar principles of operations as initiators, but are flameless, and a housing of the actuator maintains its integrity. In other words, the actuator maintains its integrity by not bursting open during actuation. The disclosed actuator assemblies are described in the operation with an airbag assembly. As can be appreciated, the disclosed actuator assemblies may be used with various types of airbag assemblies, including, for example, front air bags, inflatable curtains, passenger air bags, side airbags, etc. The disclosed embodiments of actuator assemblies may also be utilized in conjunction with any of a variety of automotive safety devices in addition to inflatable airbag modules, including, but not limited to, a knee bolster, a seat belt pretensioner, a tether cutter, or any other automotive safety device. 
     The phrases “connected to,” “coupled to,” and “in communication with” refer to any form of interaction between two or more entities, including mechanical, electrical, magnetic, electromagnetic, fluid, and thermal interaction. Two components may be coupled to each other even though they are not in direct contact with each other. The term “abutting” refers to items that are in direct physical contact with each other, although the items may not necessarily be attached together. 
       FIGS. 1-2  depict perspective views of an interior of a vehicle  10 , in which an occupant  20  is seated on a seat  18 . An inflatable airbag assembly  100  is depicted in a deployed configuration. The airbag assembly  100  may comprise an inflatable airbag  110 , one or more tethers  120 , a housing  130 , and a tether release assembly  150 . The airbag assembly  100  is depicted as being mounted in an instrument panel  12 , via a mounting bracket  137 . 
     The airbag assembly  100  may be used to minimize occupant injury in a collision scenario. The airbag assembly  100  may be installed at various locations within a vehicle, including, but not limited to, the steering wheel, the instrument panel, within the side doors or side seats, adjacent to the roof rail of the vehicle, in an overhead position, or at the knee or leg position. In the following disclosure, “airbag” may refer to an inflatable curtain airbag, overhead airbag, front airbag, or any other airbag type. 
     In  FIG. 1 , the airbag assembly  100  provides a front airbag  110 . Front airbags are typically installed in the steering wheel and/or an instrument panel of a vehicle. During installation, the airbag  110  may be rolled, folded, or both, and retained in the rolled/folded state behind a cover. During a collision event, vehicle sensors trigger the activation of an inflator, which rapidly fills the airbag with inflation gas. Thus, the airbag rapidly changes configurations from the rolled/folded configuration to an expanded configuration. A deployed configuration of the airbag  110  may be partially determined by one or more internal or external tethers, such as tether  120 . The tether  120  may limit or restrict the width, depth, and/or height of the airbag  110 . Further the tether  120  may be configured to be releasable such that the airbag  110  may adopt more than one deployed configuration. As will be described, an actuator according to the present disclosure may be utilized to initiate a release of the tether  120 . In other embodiments, an actuator according to the present disclosure may be utilized to initiate a severing (e.g., cutting) of the tether  120 . 
     In  FIG. 1 , the airbag assembly  100  is in an inflated state and extends from the housing  130  to a predetermined depth in a car-rearward direction. The tether  120  may be located within an inflatable void  118  of the inflatable airbag  110  such that a front face  113  of the inflatable airbag  110  may be deployed to a predetermined depth. The tether  120  comprises a connecting portion  125 , which connects the tether  120  to the tether release assembly  150 . 
     The tether release assembly  150  may either retain the connecting portion  125  or release the connecting portion  125  such that the inflatable airbag  110  may adopt either a constrained configuration or an unconstrained, fully deployed configuration, as depicted in  FIG. 2 . Before or during deployment of the inflatable airbag  110 , one or more vehicle sensors may electronically signal the tether release assembly  150  to release the tether  120  and thereby allow the inflatable airbag  110  to deploy without constraint imposed by the tether  120 . In the depicted embodiment, the connecting portion  125  of the tether  120  comprises a loop  124  that may be retained or released by the tether release assembly  150 . 
     As will be appreciated by those skilled in the art, one or more vehicle sensors of a variety of types and configurations can be utilized to configure a set of predetermined conditions that will dictate whether the tether release assembly  150  releases the tether  120 . For example, in one embodiment, a seat rail sensor is utilized to detect how close or far away from an airbag deployment surface an occupant&#39;s seat is positioned. In another embodiment, a seat scale may be used to determine whether an occupant is occupying the seat and, if so, ascertain an approximate weight of the occupant. In yet another embodiment an optical or infrared sensor may be used to determine an occupant&#39;s approximate surface area and/or distance from an airbag deployment surface. In another embodiment, an accelerometer is employed to measure the magnitude of negative acceleration experienced by a vehicle, which may indicate whether an accident has occurred and the severity of the accident. Additionally, a combination of these and other suitable sensor types may be used. 
     The present disclosure is directed to the tether release assembly  150  (and specifically an actuator of the tether release assembly  150 ) and methods of detaching the tether  120  from the tether release assembly  150 . When the tether release assembly  150  is actuated, the tether  120  is released or detached from the tether release assembly  150 . The tether release assembly  150  may comprise a plurality of components, such as an assembly housing (e.g., assembly housing  300  in  FIG. 7 ), an actuator assembly (e.g., actuator assembly  200  in  FIG. 3A ), and a tether  120 . Compared to other safety device actuators, the disclosed actuator assembly  200  may be smaller due to the fact that the portion of the actuator doing the work is actually the actuator cup itself and a separate piston or pushing component is not needed in the actuator assembly  200 , thereby reducing the overall envelope. In other words, the overall size of the device may be smaller than other similar devices because device contains fewer parts. 
       FIGS. 3A and 3B  illustrate an isometric view of the actuator assembly  200  according to one embodiment. The actuator assembly  200  comprises a hollow tubular housing  202  (e.g., an actuator cup). The tubular housing  202  includes opposing first and second longitudinal ends  204 ,  206 . The first longitudinal end  204  may also be referred to as a proximal end of the actuator assembly  200  and the second longitudinal end  206  may be referred to as a distal end of the actuator assembly  200 . In some embodiments, an electrical insulation layer  208  encompasses a portion (e.g., a majority) of the tubular housing  202  and the second longitudinal end  206 , as illustrated in  FIG. 3B . The electrical insulation layer  208  may be a high dielectric plastic layer to help prevent inadvertent deployment of the actuator assembly  200 , such as by an inadvertent electrical charge as may occur through building of static electricity. In some embodiments, the tubular housing  202  does not include the electrical insulation layer  208 , as illustrated in  FIG. 3A . 
     As illustrated in  FIG. 3A , the second longitudinal end  206  of the tubular housing  202  may comprise a surface  210  with a predetermined shape. For example, in one embodiment, the second end  206  of the tubular housing  202  in a pre-actuation configuration comprises a concave surface  212  and the second end  206  of the tubular housing  202  in a post-actuation configuration comprises a convex surface (e.g. see convex surface  214  in  FIG. 4B ). As discussed in more detail below, during actuation of the actuator assembly  200 , the second end  206  of the tubular housing  202  may transition from the concave surface  212  to the convex surface  214 . 
       FIGS. 4A and 4B  illustrate a cross-sectional view of the actuator assembly  200 , according to one embodiment.  FIG. 4A  illustrates the actuator assembly  200  in a pre-actuation configuration and  FIG. 4B  illustrates the actuator assembly  200  in a post-actuation configuration. During (e.g., throughout the course of) actuation, the actuator assembly  200  maintains its integrity. In other words, the actuator assembly  200  maintains its integrity by not bursting open during actuation. Thus, the actuator assembly  200  is flameless (e.g., does not produce a flame during actuation). The actuator assembly  200  defines a storage chamber  220  for housing a pyrotechnic material  230 . For example, in one embodiment, the pyrotechnic material  230  may be Zirconium Potassium Percholate (ZPP), Zirconium Tungsten Potassium Perchlorate (ZWPP), or any other suitable composition. 
     The actuator assembly  200  may further comprise electrical conductors  207  (e.g., pins) that are configured to actuate the actuator assembly  200  and ignite the pyrotechnic material  230  when an electrical signal is received, resulting in a collision event. In other words, the electrical conductors  207  create an electrical connection that initiates communication with the pyrotechnic material  230 . In other words, the electrical conductors  207  are in reaction initiating communication with the pyrotechnic material  230 . The electrical signal may pass through a bridgewire across a distal end of the electrical conductors  207  so as to ignite the pyrotechnic material  230 . The ignition of the pyrotechnic material  230  produces gas and a sufficient pressure wave to transition the second end  206  of the tubular housing  202  from the concave surface  212  to the convex surface  214 . The deformation of the second end  206  of the tubular housing  202  occurs in the longitudinal or axial direction. In other words, pre-actuation ( FIG. 4A ) the second end  206  of the tubular housing  202  comprises the concave surface  212  and post-actuation ( FIG. 4B ) the second end  206  of the tubular housing  202  comprises the convex surface  214 . The actuation of the actuator assembly  200  is contained within the actuator assembly  200 , and no external ballistic event occurs before, during, or after actuation of the actuator assembly  200 . Further, there are no loose or unattached parts that can fly around within the vehicle after the actuation of the actuator assembly  200  as all loose parts are contained within the actuator assembly  200 . 
     In the pre-actuation configuration, the surface  210  of the second end  206  of the tubular housing  202  comprises the concave surface  212 . The concave surface  212  comprises an inflection point  213  that is disposed a predetermined distance D 1  from the second end  206  of the tubular housing  202 . In some embodiments, the distance D 1  is at least 0.3 mm. In some embodiments, the distance D 1  is at least 0.5 mm. In some embodiments, the distance D 1  is not greater than 3 mm. 
     In the post-actuation configuration, the surface  210  of the second end  206  of the tubular housing  202  comprises the convex surface  214 . The convex surface  214  comprises an inflection point  215  that is disposed a predetermined distance D 2  from the second end  206  of the tubular housing  202 . In some embodiments, the distance D 2  is at least 0.3 mm. In some embodiments, the distance D 2  is at least 0.5 mm. In some embodiments, the distance D 2  is not greater than 3 mm. 
     In some embodiments, the inflection point  213  of the pre-actuation concave surface  212  transitions longitudinally (i.e., axially) between 1 mm and 6 mm to the inflection point  215  of the post-actuation convex surface  214 . In some embodiments, the inflection point  213  of the pre-actuation concave surface  212  transitions longitudinally (i.e., axially) between 1 mm and 3 mm to the inflection point  215  of the post-actuation convex surface  214 . 
     Actuation of the actuator assembly  200  may occur quickly. For example, the transition from the concave surface  212  to the convex surface  214  may occur at speeds faster than 0.4 msec. In some embodiments, the speed of transition from the concave surface  212  to the convex surface  214  may be less than 0.3 msec. In some embodiments, the speed of transition from the concave surface  212  to the convex surface  214  may be less than 0.2 msec. In some embodiments, the speed of transition from the concave surface  212  to the convex surface  214  may be less than 0.1 msec. Because actuation of the actuator assembly  200  is contained (e.g., gas, ballistic events) within the actuator assembly  200 , the actuation time is significantly reduced compared to existing systems that work with the physical effects of the actuator&#39;s ballistic gases outside the actuator, which requires more time, such as 1.6 msec. 
     In some embodiments, in the pre-actuation configuration, the concave surface  212  may have a circular shape. A diameter d 1  of the concave surface  212  may be the same as a diameter d 2  of the tubular housing  202 . In some embodiments, the diameter d 1  of the concave surface  212  may be less than the diameter d 2  of the tubular housing  202 . 
     In some embodiments, in the post-actuation configuration, the convex surface  214  may have a circular shape. A diameter of the convex surface  214  may be the same as the diameter of the tubular housing  202 . In some embodiments, the diameter of the convex surface  214  may be less than the diameter of the tubular housing  202 . 
     The actuator assembly  200  may further comprise a coolant  240  disposed within the chamber  220 . The coolant  240  may mitigate the deflagration temperature of the pyrotechnic material  230  and may prevent the burn-through ballistic rupture of the second end  206  of the tubular housing  202 . The prevention of the burn-through ballistic rupture of the second end  206  makes the actuator assembly  200  flameless. One benefit of the coolant  240  in the actuator assembly  200  is there is no hazard of cup rupture during normal function or even in a bonfire. 
     The coolant  240  may be disposed within the chamber  220  of the tubular housing  202  between the pyrotechnic material  230  and the second end  206  of the tubular housing  202 . The coolant  240  may be spaced apart from the pyrotechnic material  230 . In some embodiments, the coolant  240  may be disposed along the entire inner surface of the second end  206  of the tubular housing  202 . In some embodiments, the coolant  240  may be disposed at the inflection point  213  of the second end  206 . The coolant  240  may be a slurry so that the coolant stays in the desired location after being placed in the tubular housing  202 . 
     In certain aspects, the coolant  240  has a decomposition temperature in the range of greater than or equal to about 180° C. to less than or equal to about 450° C., meaning that the compound decomposes endothermically within this temperature range for example by releasing water or carbon dioxide. The coolant  240  nay be selected per its cooling efficiency. In certain preferred variations, the coolant  240  comprises aluminum hydroxide (Al(OH) 3 ). However, in alternative variations the following compounds could be employed as a coolant component: Aluminum Hydroxide, Hydromagnesite, Dawsonite, Zinc borate hydrate, Magnesium Hydroxide, Magnesium Carbonate Subhydrate, Bohemite, Calcium Hydroxide, Dolomite, Huntite, Montmorillonite, and combinations thereof. Each of these compounds decomposes endothermically within the desired temperature range of greater than or equal to 180° C. to less than or equal to 450° C., as set forth in Table 1 below. 
     
       
         
           
               
               
               
             
               
                 TABLE 1 
               
               
                   
               
               
                   
                   
                 Decomposition 
               
               
                 Compound 
                 Chemical Formula 
                 Temp. ° C. 
               
               
                   
               
             
            
               
                 Aluminum Hydroxide 
                 Al(OH) 3   
                 180-200 
               
               
                 Hydromagnesite 
                 Mg 5 (CO 3 ) 4 (OH) 2 •4H 2 O 
                 220-240 
               
               
                 Dawsonite 
                 NaAl(OH) 2 CO 3   
                 240-260 
               
               
                 Zinc borate hydrate 
                 2ZnO•3B 2 O 3 •3.5H 2 O 
                 290 
               
               
                 Magnesium Hydroxide 
                 Mg(OH) 2   
                 300-320 
               
               
                 Magnesium Carbonate 
                 MgO•CO 2 •H 2 O (0.3)   
                 340-350 
               
               
                 Subhydrate 
                   
                   
               
               
                 Bohemite 
                 AlO(OH) 
                 340-350 
               
               
                 Calcium Hydroxide 
                 Ca(OH) 2   
                 430-450 
               
               
                 Dolomite 
                 CaMg(CO 3 ) 2   
                 ~650  
               
               
                 Huntite 
                 Mg 3 Ca(CO 3 ) 4   
                 ~180  
               
               
                 Montmorillonite 
                 (Na,Ca) 0.33 (Al,Mg) 2 (Si 4 O 10 )(OH) 2 • n H 2 O 
                 300 
               
               
                   
               
            
           
         
       
     
     The amount of the coolant  240  disposed within the chamber  220  may vary depending on a variety of factors, such as the volume of the chamber  220 , the amount of the pyrotechnic material  230 , etc. Accordingly, in some embodiments, the amount of the coolant  240  disposed within the chamber  220  may range between 50 mg and 150 mg. In some embodiments, the amount of the coolant  240  is 100 mg. 
       FIGS. 5 and 6  illustrate the actuator assembly  200  disposed within an over-mold  250 .  FIG. 5  illustrates an isometric view of the over-mold  250  and actuator assembly  200 , and  FIG. 6  illustrates a cross-sectional view of the over-mold  250  and actuator assembly  200 . The over-mold  250  may be molded over the actuator assembly  200 . 
     The over-mold  250  may comprise a first end  252  and a second end  254 . The second end  254  of the over-mold  250  of  FIGS. 5 and 6  comprises an open end. The open end of the over-mold  250  may allow the second end  206  of the actuator assembly  200  to align with the second end  254  of the over-mold  250 . In some embodiments, the second end  206  of the actuator assembly  200  extends out of the open end of the second end  254  of the over-mold  250 . 
     The first end  252  of the over-mold  250  may also comprise an open end. The electrical conductors  207  of the actuator assembly  200  may be accessible through the open end on the first end  252  of the over-mold  250 . 
     An outer surface of the over-mold  250  may comprise a plurality of sections or portions, a first end portion  255 , a hexagon shaped portion  256 , and a second end portion  257 . The shape of the hexagon shaped portion  256  may facilitate assembly, and specifically insertion of the over-mold  250  into a housing assembly. The present disclosure is not limited to a hexagon shape for the hexagon shaped portion  256 . In some embodiments, the hexagon shaped portion  256  may be non-circular and a variety of different cross-sectional shapes may be used, such as triangular, square, rectangular, polygonal, octagonal, and the like. The first end portion  255  extends from the first end  252  to the hexagon shaped portion  256  in a longitudinal direction of the over-mold  250 . A first end portion  255  may comprise a plurality of different sections, each section with a different diameter, to enable the first end portion  255  to interact with the assembly housing  300 , as illustrated in  FIG. 7 . 
     The hexagon shaped portion  256  longitudinally extends between the first end  252  and the second end  254  of the over-mold  250 . The hexagon shaped portion  256  comprises six equal sides that encompass and define the circumference of the over-mold  250 . The hexagon shaped portion  256  may comprise a textured surface. The textured surface of the hexagon shaped portion  256  may comprise a plurality of ribs  258  that are longitudinally spaced along the over-mold  250 , wherein each rib  258  encompasses the circumference of the over-mold  250 . In the illustrated embodiment, the hexagon shaped portion  256  comprises three ribs  258 ; however, the over-mold  250  may have more or fewer than three ribs  258 . Valleys  259  may be disposed between adjacent ribs  258  and are longitudinally spaced along the hexagon shaped portion  256 . The valleys  259  may be annular grooves that encircle the hexagon shaped portion  256 . The valleys  259  may be define by adjacent ribs  258 . The ribs  258  may extend radially outward from the outer surface of the over-mold  250 . The valleys  259  may extend radially inward from the outer surface of the over-mold  250 . 
     The second end portion  257  extends from the hexagon shaped portion  256  to the second end  254 . The second end portion  257  may comprise a constant diameter that enables the second end portion  257  to be secured in a portion of the assembly housing  300 , as illustrated in  FIG. 7  and as discussed in more detail below. 
     The over-mold  250  may be fabricated from a number of different materials, such as high-density polyethylene (HDPE), acrylonitrile butadiene styrene (ABS), acrylic polymethyl methacrylate (acrylic PMMA), acetal copolymer, acetal polyoxymethylene copolymer, poly ether ketone (PEEK), polyetherimide (PEI), polybutylene terephthalate (PBTR), polyamide (PA) including (HTN), polyphthalamide (PPA), and the like. 
       FIG. 7  illustrates an assembly housing  300  of the tether release assembly  150 . The assembly housing  300  is configured to house the actuator assembly  200  disposed within the over-mold  250 . The assembly housing  300  may at least partially encompasses the actuator assembly  200  disposed within the over-mold  250 . The over-mold  250  is configured to be able to slide along an inner surface or a sliding path within the assembly housing  300 . For example, the assembly housing  300  may comprise a sliding surface  310 , an engaging surface  320 , a retaining arm  330 , a reactive surface  340 , a retaining end  350 , and a tether slot  360 . The inner surface may include the sliding surface  310  and the engaging surface  320 . 
     The sliding surface  310  is disposed on a first end of the assembly housing  300  and enables the over-mold  250  to slide along the sliding surface  310  during actuation of the actuator assembly  200 . 
     The engaging surface  320  comprises a surface that corresponds to the hexagon shaped portion  256  of the over-mold  250 . The engaging surface may comprise a textured surface that corresponds with the textured surface of the hexagon shaped portion  256  of the over-mold  250 . The textured surface of the engaging surface  320  may comprise a plurality of ribs  322  and valleys  324  that are longitudinally spaced apart from each other. The ribs  322  may extend radially inward from the inner surface of the assembly housing  300 . The valleys may extend radially outward from the inner surface of the assembly housing  300 . The ribs  322  of the engaging surface  320  are configured to fit or nest within the valleys  259  of the over-mold  250 , and the ribs  258  of the over-mold  250  are configured to fit or otherwise nest within the valleys  324  of the engaging surface  320 . Accordingly, when the over-mold  250  is engaged with the engaging surface  320 , a predetermined amount of force is needed to dislodge the over-mold  250  from the engaging surface  320  and enable the over-mold  250  to slide relative to the assembly housing  300 . 
     The retaining arm  330  is configured to retain the over-mold  250  within the assembly housing  300  before actuation. The retaining  330  arm may partially encircle the over-mold  250  to retain the over-mold  250  within the assembly housing  300 . An inner surface of the retaining arm  330  may comprise at least one rib  322  that fits or nests in a valley  259  of the over-mold or simply between two adjacent ribs  258  of the over-mold  250 . 
     The reactive surface  340  of the assembly housing  300  is configured to interact with the surface  210  of the tubular housing  202 . The second end  206  of the tubular housing  202  abuts the reactive surface  340  pre-actuation. During actuation, the pre-actuation concave surface  212  transitions to the post-actuation convex surface  214  and the inflection point  215  impacts the reactive surface  340  at a predetermined amount of force. The amount of force generated exceeds the amount of predetermined force needed to dislodge the ribs  258  of the over-mold  250  from the valleys of the engaging surface  320  and the actuator assembly is displaced relative to the assembly housing  300 . In some embodiments, the transition between the concave surface  212  to the convex surface  214  may create at least 1000 Newtons (N) of force when the surface  210  impacts the reactive surface  340 . In some embodiments, the retaining arm  230  is flexible and the force produced by the actuation of the pyrotechnic material  230  causes the ribs  258  of the over-mold  250  to push the retaining arm  330  radially outward thereby facilitating the over-mold  250  sliding relative to the assembly housing  300 . 
     The retaining end  350  is configured to secure and retain the second end  254  of the over-mold  250  when the over-mold  250  is in the pre-actuated configuration. 
     The tether slot  360  is disposed between the retaining arm  330  and the retaining end  350 . The tether slot  360  enables the tether  120  to loop around the over-mold  250 , thus securing the tether  120  to the tether release assembly  150 . The tether  120  remains in a taught configuration until the tether  120  is released from the tether release assembly  150  through actuation of the actuator assembly  200  and actuation of the tether release assembly  150 . 
       FIGS. 8A-8C  illustrate the actuation of the tether release assembly  150  from the pre-actuation configuration to the post-actuation configuration and to the release of the tether  120 .  FIG. 8A  illustrates the tether release assembly  150  in a pre-actuation configuration. The over-mold  250  and the actuator assembly  200  are housed within the assembly housing  300 . In response to a predetermined event, such as a collision event, an electrical signal may be sent to the actuator assembly  200  through the electrical conductors  207  to ignite the pyrotechnic material  230 . The ignition of the pyrotechnic material  230  produces gas and a sufficient pressure wave to transition the surface  210  of the second end  206  of the tubular housing  202  from the concave surface  212  to the convex surface  214 . The inflection point  215  of the convex surface  214  impacts the reactive surface  340  and produces a sufficient amount of force to dislodge the ribs  258  from the valleys of the engaging surface  320  and the over-mold  250  starts to slide along the sliding surface  310 . The tether  120  is wrapped or looped around the over-mold  250 . The load on the tether  120  may vary from no load or no tension to a snap load or significantly high tension (i.e., 1100 N). 
       FIG. 8B  illustrates the tether release assembly  150  in a post-actuation configuration. The over-mold  250  is sliding along the sliding surface  310 , but the tether  120  is still wrapped around the over-mold  250 . The tether slot  360  keeps the tether  120  in a predetermined position, thus the over-mold  250  is configured to slide relative to the tether  120 . 
       FIG. 8C  illustrates the tether release assembly  150  releasing the tether  120 . After the over-mold  250  travels a predetermined distance and clears the tether slot  360 , the tether  120  is detached or released. 
       FIG. 9  depicts an embodiment of a tether release assembly  150 ′ that resembles the tether release assembly  150  described above in certain respects. Accordingly, like features are designated with like reference numerals, with an apostrophe. For example, the embodiment depicted in  FIG. 9  includes an assembly housing  300 ′ that may, in some respects, resemble the assembly housing  300  of  FIG. 7 . Relevant disclosure set forth above regarding similarly identified features thus may not be repeated hereafter. Moreover, specific features of assembly housing  300  and related components shown in  FIG. 7  may not be shown or identified by a reference numeral in the drawings or specifically discussed in the written description that follows. However, such features may clearly be the same, or substantially the same, as features depicted in other embodiments and/or described with respect to such embodiments. Accordingly, the relevant descriptions of such features apply equally to the features of the tether assembly  150 ′ and related components depicted in  FIG. 9 . Any suitable combination of the features, and variations of the same, described with respect to the tether assembly  150  and related components illustrated in  FIG. 7  can be employed with the tether assembly  150 ′ and related components of  FIG. 9 , and vice versa. This pattern of disclosure applies equally to further embodiments depicted in subsequent figures and described hereafter, wherein the leading digits may be further incremented. 
     The tether assembly  150 ′ includes an actuator assembly  200 ′ disposed within an over-mold  250 ′. The over-mold  250 ′ is housed within the assembly housing  300 ′. The assembly housing  300 ′ includes a reactive surface  340 ′ that is configured to interact with a surface  210 ′ of a tubular housing  202 ′ of the actuator assembly  200 ′. The second end  206 ′ of the tubular housing  202 ′ abuts the reactive surface  340 ′ pre-actuation. The reactive surface  340 ′ may include a bump or convex feature. The bump or convex feature may comprise an inflection point and the inflection point of the bump or convex feature may align with the inflection point  213  of the concave surface  212  of the second end  206  of the tubular housing  202 . 
     The bump or convex feature may correspond with a concave surface  212 ′ of the surface  210 ′. In some embodiments, the bump or convex feature may have a radius of curvature equal to the radius of curvature of the concave surface  212 ′. In some embodiments, the bump or convex feature may have a radius of curvature greater than the radius of curvature of the concave surface  212 ′. In some embodiments, the bump or convex feature may have a radius of curvature less than the radius of curvature of the concave surface  212 ′. 
     During actuation, the pre-actuation concave surface  212 ′ transitions to the post-actuation convex surface and impacts the bump or convex feature of the reactive surface  340 ′ at a predetermined amount of force. The amount of force generated exceeds the amount of predetermined force needed to dislodge the ribs  258 ′ of the over-mold  250 ′ from ribs  322 ′ and valleys  324 ′ of the engaging surface  320 ′ and the actuator assembly is displaced relative to the assembly housing  300 ′. In some embodiments, the transition between the concave surface  212 ′ to the convex surface creates at least  1000  N of force when the surface  210 ′ impacts the reactive surface  340 ′. 
     In some embodiments, the assembly housing  300 ′ may further comprise a stop wall  370 ′ that is configured to stop the relative movement of the over-mold  250 ′ relative to the assembly housing  300 ′ after actuation of the pyrotechnic material. The stope wall  370 ′ is configured to engage with and slow down the over-mold after actuation. 
     Example 1. An actuator device comprising: an actuator cup comprising a first end and a second end, the actuator cup defining a storage chamber containing a pyrotechnic material to produce gas; and at least one electrical connection coupled to the first end, the electrical connection in reaction initiating communication with the pyrotechnic material, wherein the second end of the actuator cup comprises a concave surface before actuation of the pyrotechnic material and during the actuation of the pyrotechnic material the second end transitions from the concave surface to a convex surface. 
     Example 2. The actuator device of example 1, further comprising a coolant disposed within the storage chamber of the actuator cup. 
     Example 3. The actuator device of example 2, wherein the coolant is aluminum hydroxide. 
     Example 4. The actuator device of example 2, wherein the coolant is disposed at an inflection point of the concave surface. 
     Example 5. The actuator device of example 1, wherein the gas is contained within the storage chamber after actuation of the pyrotechnic material. 
     Example 6. The actuator device of example 1, wherein the transition between the concave surface to the convex surface occurs in less than 0.4 msec. 
     Example 7. The actuator device of example 1, wherein the transition between the concave surface to the convex surface creates at least 1000 Newtons of force. 
     Example 8. An actuator assembly comprising: an actuator comprising: a tubular housing with a first end and a second end, the tubular housing defining a storage chamber containing a pyrotechnic material to produce gas; and at least one electrical connection coupled to the first end, the electrical connection in reaction initiating communication with the pyrotechnic material; wherein the second end of the tubular housing is formed as a concave surface before actuation of the pyrotechnic material and during the actuation of the pyrotechnic material the second end is transitioned from the concave surface to a convex surface; and an assembly housing configured to house the actuator, wherein the assembly housing comprises a reactive surface, wherein the second end of the tubular housing impacts the reactive surface during actuation of the pyrotechnic material. 
     Example 9. The actuator assembly of example 8, wherein during the transition between the concave surface to the convex surface, the second end impacts the reactive surface of the assembly housing to displace the actuator within the assembly housing away from the reactive surface. 
     Example 10. The actuator assembly of example 8, further comprising an actuator housing that partially encompasses the actuator. 
     Example 11. The actuator assembly of example 10, wherein the actuator housing comprises an outer hexagon shape that corresponds with an inner surface of the assembly housing. 
     Example 12. The actuator assembly of example 8, further comprising a coolant disposed within the storage chamber of the tubular housing. 
     Example 13. The actuator assembly of example 12, wherein the coolant is aluminum hydroxide. 
     Example 14. The actuator assembly of example 8, wherein the gas is contained within the storage chamber after actuation of the pyrotechnic material. 
     Example 15. The actuator assembly of example 8, wherein the transition between the concave surface to the convex surface occurs in less than 0.4 msec. 
     Example 16. The actuator assembly of example 8, further comprising a tether that is looped around the tubular housing and is released from the tubular housing after actuation of the pyrotechnic material. 
     Example 17. The actuator assembly of example 16, wherein the tether is released from the tubular housing when the actuator is displaced away from the reactive surface. 
     Example 18. The actuator assembly of example 16, wherein the assembly housing comprises an aperture that enables the tether to enter into the assembly housing through the aperture, loop around the tubular housing, and exit the assembly housing through the aperture. 
     Example 19. The actuator assembly of example 16, wherein the tether is under tension before actuation of the pyrotechnic material. 
     Example 20. An actuator device comprising: an actuator cup comprising a first end and a second end, the actuator cup defining a storage chamber containing a pyrotechnic material to produce gas; and at least one electrical connection coupled to the first end, the electrical connection in reaction initiating communication with the pyrotechnic material, wherein the second end of the actuator cup comprises an inflection point, wherein actuation of the pyrotechnic material displaces the inflection point of the second end an axial distance away from the first end of the actuator cup. 
     The terms “a” and “an” can be described as one but not limited to one. For example, although the disclosure may recite a tab having “a line of stitches,” the disclosure also contemplates that the tab can have two or more lines of stitches. 
     Unless otherwise stated, all ranges include both endpoints and all numbers between the endpoints. 
     Reference throughout this specification to “an embodiment” or “the embodiment” means that a particular feature, structure, or characteristic described in connection with that embodiment is included in at least one embodiment. Thus, the quoted phrases, or variations thereof, as recited throughout this specification are not necessarily all referring to the same embodiment. 
     Similarly, it should be appreciated that in the above description of embodiments, various features are sometimes grouped together in a single embodiment, figure, or description thereof for the purpose of streamlining the disclosure. This method of disclosure, however, is not to be interpreted as reflecting an intention that any claim require more features than those expressly recited in that claim. Rather, as the following claims reflect, inventive aspects lie in a combination of fewer than all features of any single foregoing disclosed embodiment. Thus, the claims following this Detailed Description are hereby expressly incorporated into this Detailed Description, with each claim standing on its own as a separate embodiment. This disclosure includes all permutations of the independent claims with their dependent claims. 
     Recitation in the claims of the term “first” with respect to a feature or element does not necessarily imply the existence of a second or additional such feature or element. It will be apparent to those having reasonable skill in the art that changes may be made to the details of the above-described embodiments without departing from the underlying principles of the invention. Embodiments of the invention in which an exclusive property or privilege is claimed are as follows.