Abstract:
This invention is in the field of safety devices to lessen injuries arising from impact in vehicles, particularly automobiles. A bolster which may be employed to reduce impact severity to passengers from either frontal or side impacts is activated by impact sensing devices. The housing of the bolster has a lateral length L. Upon activation, the bolster is inflated with an activating fluid and extends the lateral length L of bolster upon activation.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 12/422,389, filed Apr. 13, 2009, and published as U.S. Patent Application Pub. No. 2009/0250915 on Oct. 8, 2009, which claims the benefit of and priority to U.S. Provisional Patent Application No. 61/044,294, filed Apr. 11, 2008. This application also is a continuation-in-part of U.S. patent application Ser. No. 11/560,473, filed Nov. 16, 2006, and published as U.S. Patent Application Pub. No. 2007/0108747 on May 17, 2007, which claims the benefit of and priority to U.S. Provisional Patent Application No. 60/738,222, filed Nov. 17, 2005. U.S. patent application Ser. No. 12/422,389 is a continuation-in-part of U.S. patent application Ser. No. 11/560,473. The entire contents of each of the foregoing applications and publications are hereby incorporated by reference. 
    
    
     FIELD OF THE INVENTION 
     This invention relates to the field of safety devices as are often installed in motor vehicles, particularly automobiles. Amongst many safety devices that are installed in vehicles to lessen injuries arising from impact are bolsters. A bolster may be part of an instrument panel in which case the bolster extends transversely to the vehicle. Bolsters may also be used for side impact events in which case the length of a bolster may extend longitudinally of the vehicle. Such bolsters may be mounted in door panels, side panels or roof panels of the vehicle. Bolsters can also be utilized in other locations and directions as desired to lessen injuries arising from impact events. 
     BACKGROUND OF THE INVENTION 
     In the first instance, bolsters are designed with a design point of impact. The design point of impact is determined by assuming the position of a statistical male or female occupant. Ideally, the vehicle occupant is in a designated position and is using a seatbelt or other similar safety harness. However, because of the differentiation in size of the vehicle occupants and because not all vehicle occupants use seatbelts, and therefore the location of the occupant may not be as expected, the point of impact between the occupant and the bolster may occur at other than the most desirable design location. Vehicles also have many other envelope constraints as to the amount of space available for mounting a bolster. In many cases, the vehicle mounting envelope constraints confine a bolster to a certain lateral length. It would be desirable, however, that the bolster, when called upon to provide its safety function, have a greater lateral length. 
     As used in this description and claims, the term “lateral” is used to describe the transverse width of the bolster. If the bolster were mounted against an instrument panel, the lateral extent of the direction would be transverse of the vehicle. If the bolster were mounted to a door frame, the lateral extent of the bolster would extend longitudinally of the vehicle. If the bolster were mounted on an angular support pillar such as an A pillar, the lateral length of the bolster would extend longitudinally and angularly of the vehicle. In short, the term “lateral” is intended to encompass any mounting location of the bolster with regard to the vehicle. 
     In accordance with the information set out above, it would be desirable, if a bolster were able to increase its lateral extent upon activation. 
     Known in the art are the following patent and patent applications which disclose inflatable bolsters and the like: US 2007/0108747; U.S. Pat. No. 6,032,978; U.S. Pat. No. 6,203,057; U.S. Pat. No. 6,305,710; U.S. Pat. No. 6,517,103; U.S. Pat. No. 6,578,867; U.S. Pat. No. 6,619,689; U.S. Pat. No. 6,758,493; U.S. Pat. No. 6,848,715; U.S. Pat. No. 6,976,706; U.S. Pat. No. 7,350,852; and WO 2006/132990. 
     SUMMARY OF THE INVENTION 
     In accordance with this invention, an inflatable bolster includes a housing, the housing defines a substantially closed volume for receiving fluid under pressure. The bolster has a source of pressurizing fluid. The housing defines an occupant face and a mounting face. The housing has a lateral length L in the direction substantially parallel to the occupant face. The bolster comprises an extension structure for extending the lateral length L of the bolster upon pressurization of the bolster. 
     In accordance with another aspect of the present invention, an inflatable bolster for use in an occupant compartment of a vehicle is provided, the inflatable bolster comprising an inflatable housing having a mounting wall which is devised to mount to a reaction structure of the vehicle, an occupant wall which is opposite the mounting wall and devised to face the occupant compartment, a substantially closed volume formed between the mounting wall and the occupant wall, and a restriction means formed between the mounting wall and the occupant wall for restricting fluid flow between different areas of the housing. The inflatable bolster also comprises a source of pressurized fluid mounted to the housing and being in fluid communication with the substantially closed volume for inflating the housing. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will be better understood, upon review of the attached drawings which illustrate various embodiments in accordance with the invention. 
         FIG. 1  illustrates an isometric view of a bolster in accordance with the invention which incorporates alternate first and second embodiments of the invention; 
         FIG. 2  illustrates an isometric view of the un-deployed configuration of the left end of the bolster of  FIG. 1 ; 
         FIG. 3  illustrates an isometric view of the deployed configuration of the structure illustrated in  FIG. 2 ; 
         FIG. 4  illustrates a cross-section of the bolster of  FIG. 1  taken along line  4 - 4 ; 
         FIG. 5  is a similar cross-section to  FIG. 4  showing the bolster of  FIG. 4  in deployed configuration; 
         FIG. 6  is a plan view of the deployed bolster of  FIG. 5 ; 
         FIG. 7  is a perspective view of the structure of the right-hand end of the bolster of  FIG. 1  in the un-deployed configuration; 
         FIG. 8  illustrates in perspective view the structure of  FIG. 7  in the deployed configuration; 
         FIG. 9  illustrates a perspective view of a bolster in accordance with the invention which incorporates a third embodiment of the invention; 
         FIG. 10  is a front view of the bolster shown in  FIG. 9 ; 
         FIG. 11  is a sectional view taken along line AA as shown in  FIGS. 9 and 10 ; 
         FIG. 12  is a sectional view taken along lines BB shown in  FIGS. 9 and 10 ; 
         FIG. 13  is a sectional view along line CC illustrated in  FIGS. 9 and 10 ; 
         FIG. 14  illustrates an isometric view of a bolster in accordance with the invention which incorporates a fourth embodiment of the invention; 
         FIG. 15  is a front view of the bolster of  FIG. 14 ; 
         FIG. 16  is a sectional view along line DD of  FIGS. 14 and 15 ; 
         FIG. 17  illustrates a perspective view of a bolster in accordance with the invention which incorporates a fifth embodiment of the invention; 
         FIG. 18  is a sectional view taken along lines EE and FF shown in  FIG. 17 ; 
         FIG. 19  illustrates a perspective view of a bolster in accordance with the invention which incorporates a fifth embodiment of the invention; 
         FIG. 20  is a sectional view taken along lines GG and HH shown in  FIG. 19 ; 
         FIG. 21  illustrates a perspective view of a bolster in accordance with the invention which incorporates a sixth embodiment of the invention; 
         FIG. 22  is a sectional view taken along line II shown in  FIG. 21 ; 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Bolsters may be used to provide energy absorption to lessen injury in the event of a vehicle/occupant impact. A bolster achieves the energy absorption by filling the bolster with a pressurized fluid, usually a gas, upon the occurrence of an impact event. Once the bolster is filled with fluid, then energy is absorbed by releasing the fluid through an orifice of controlled size. 
     Some bolsters are described as active bolsters. An active bolster differs from an inactive bolster in that the bolster moves relative to its support surface towards the occupant. By decreasing the distance between the occupant face of the bolster and the occupant, then a greater length of time may be used to slow the speed of the occupant relevant to the speed of the vehicle and thus provide an opportunity for reduction of force in decelerating the occupant relative to the vehicle. The invention of the present application may be utilized with either active or inactive bolsters. 
     Typically bolsters are pressurized by a source of gas which may be contained in a cartridge. The gas may be released by initiators which may be linked to various vehicle sensors. The vehicle sensors may sense a vehicle impact which may be in the nature of an excessive deceleration, as may be typical in frontal impacts of moving vehicles, a rapid vehicle acceleration as may be involved in a rear impact, vehicle lateral acceleration as may be involved in impacts from either side of the vehicle or impending vehicle rollover. In all cases, when such a vehicle event occurs, there develops a relative velocity between the vehicle and the occupants riding in the vehicle. The occupants may then strike vehicle structure and the purpose of the bolster is to reduce the forces involved so as to lessen injury. 
       FIG. 1  illustrates a bolster generally at  10 . The bolster has a mounting face  12  and an occupant face  14 , visible in  FIG. 4 . The bolster  10  includes an extension structure  16  located at the left hand end of bolster  10  and extension structure  18  located at the right hand end of bolster  10 . While bolster  10  has been illustrated as embodying the two extension structures  16  and  18  respectively, it will be recognized that in accordance with this invention, a bolster may use any combination of one or more of extension structures  16  and  18 . Thus, a bolster may utilize one such extension structure  16  or two or more extension structures  16 . Similarly, a bolster may involve one extension structure  18  or two or more extension structures  18 . A bolster may have any combination of one or more of the two extension structures. 
     In accordance with this embodiment of this invention as illustrated in  FIG. 1 , the bolster is a unitary structure. Being a unitary structure, the bolster is preferably made by a blow molding procedure. The bolster includes a housing  20 . The housing defines the occupant face  14  and the mounting face  12 . The housing defines a substantially closed volume  22 . The volume  22  is described as substantially closed in that the volume is intended to confine the pressurizing gas when the bolster is activated. The housing will thus either define an inlet for pressurized gas or pressurized gas will be stored in a preactivation cylinder within the housing. The housing will also define one or more exhaust apertures to permit release of gas during the energy absorption phase. 
     As shown in the un-deployed stage, the housing defines a lateral length L extending in the direction which is substantially parallel to the occupant face. 
     It will be understood that upon activation, fluid will fill the closed volume of the bolster. In the embodiment illustrated in  FIG. 1 , the bolster also includes expansion facilitating structure  30 . This allows the bolster to be an active bolster so that the occupant face will move toward the occupant to assist in reduction of forces experienced by the occupant on contacting the bolster. In the particular example illustrated in  FIG. 1 , the expansion facilitating structure  30  comprises two vertically extending pleats  32  and  34  and a laterally extending pleat  36 . The effect of these pleats during deployment will be discussed below. 
     Focusing now on the left hand end of the structure, in  FIG. 1 , the housing  20  includes a main portion  21  and an auxiliary portion  40 . The extension structure  16  comprises in part the auxiliary portion  40 . The auxiliary portion  40  is an integral part of the housing  20  and is also a hollow structure. The auxiliary portion  40 , extends away from the occupant face  14  in a direction which is substantially perpendicular to the dimension L. The auxiliary portion  40  has a length L 1  as illustrated in  FIG. 4 . Upon deployment of the bolster, the auxiliary portion  40  moves hingedly relative to the main portion  21  to extend the lateral length L of the bolster  10  by an amount substantially equal to L 1  thereby providing a laterally enlarged bolster for use during the deployment phase. The extension structure  16  also includes an expandable area  42 . The expandable area  42 , preferably includes at least one pleat  44 . The expandable area  42  is formed at the intersection of the mounting face  12  and an inner face  46  of the auxiliary portion  40 . Expansion of the expandable area  42  and the pressurization of the auxiliary portion  40  in conjunction with pressurization of the main portion causes the auxiliary portion  40  to move hingedly to the deployed position as shown in  FIG. 6 . As the auxiliary portion  40  moves hingedly relative to the main portion  21 , the corner  50  where the auxiliary portion  40  meets with the occupant face of the main portion  21 , distortion will occur, although the apex may remain as is shown diagrammatically at  52  in  FIG. 6 . In addition, the uppermost surface  54  of the auxiliary portion  40  may also deform upwardly under the effect of the pressurizing fluid. 
     Focusing now on the right hand end of the bolster  10  as illustrated in  FIG. 1 , reference is made to  FIGS. 7 and 8 . The extension structure  18  in this embodiment, is illustrated in an end face  60  of the housing  20 . The end face  60  includes an end face wall  62  which comprises the occupant face  14  of the bolster  10 . Additionally, the end face  60  includes a mounting wall face  64 , which coincides with the mounting face  12 . In the embodiment illustrated, the extension structure  18  includes an expandable area  70 . The expandable area advantageously includes at least one first pleat  72 . 
     As shown in  FIG. 7 , the expandable area  70  is in the form of at least one pleat  72  which extends internally into the closed volume  22  of the bolster  10 . Upon activation of the bolster, the pressurized fluid, pushes the pleat  72  out, relative to the end face  60 , where the pleat is able to expand to the position shown in  FIG. 8 . The pleat  72 , having extended externally of the housing  20  now provides an additional length L 2  to the bolster for use in energy absorption on contact with a vehicle occupant (see  FIG. 8 ). 
     Preferably, the bolster  10  is made in a blow molding operation. In blow molding, a parison is extruded, the parison is enclosed in a blow mold structure, and a blowing gas is injected into the interior of the parison. Upon expansion of the parison, the parison then expands so as to obtain the shape of the mold cavity. Generally speaking, the wall thickness of the parison is relatively uniform throughout the expanded parison subject to the necessity of plastic flow to obtain the shape as defined by the mold. In the blow molding process, slides can be established in the mold. The term “slide” is used to describe a structure that is used to move from a withdrawn position (usually not in the mold cavity) to an extended position, before the parison has cooled. By extending the slide, which effectively moves the slide against the wall of the parison, the wall of the parison is stretched to move inwardly of the mold surface. Thus, use of a slide may be used to create the at least one pleat  72  in connection with the extension structure  18  and to locate that structure so that it extends internally of the housing  20 . The use of the slide does not, however, rupture the wall of the parison. Thus the finished product can still remain as a housing defining a substantially closed volume. Use of the slide, will create a diminution of the thickness of the wall of the parison, this helps to create a relatively thinner wall, which is then capable of undergoing the movement between the un-deployed and deployed configurations illustrated in  FIGS. 7 and 8  without rupture of the wall of the housing. To facilitate movement of this type, the plastic used for the parison may be selected from the group of suitable materials including by way of example thermoplastic olefins or a plastic available from Salflex Polymers under the trade mark SALFLEX 245™. 
     Similarly, the extension structure  16  illustrated in  FIGS. 1 through 4  may be formed by the use of slides in a blow mold. The auxiliary portion  40  can be readily formed in the blow mold. The expandable area  42  and the at least one pleat  44  can be created in the blow mold by use of a slide which moves some of the parison wall internally of the mold cavity to create the structure upon cooling, as shown at the left hand end of  FIG. 1 . This process also is capable thus of creating an expandable area while ensuring that the housing still remains with a substantially closed volume. 
     As shown in  FIG. 1 , the bolster  10  is what is referred to as an active bolster. Thus, rather than simply pressurizing the bolster and using the pressurized thickness of the bolster for energy absorption, it is desirable that the occupant face extend outwardly toward the occupant. The pressurization of the bolster may itself distort the bolster so that the bolster achieves a more rounded configuration than the un-deployed, substantially rectangular configuration illustrated in the embodiment shown in  FIG. 1 . However, in order to facilitate further movement of the occupant face relevant to the mounting face, the bolster  10  may also include the expansion structure  30 . The expansion structure  30  can include second pleats to facilitate such expansion. The pleats may be made by use of slides or by initial configuration of the mold depending upon the location of the mold parting lines and the configuration of the mold cavity. Most preferably as shown in  FIG. 1 , the expansion structure, includes the generally vertically extending pleats  32  and  34  as well as the longitudinally extending pleat  36 . By providing at least one pleat and preferably a series of pleats, the bolster may deform outwardly relative to the mounting face  12 . 
     As shown in  FIG. 4 , the mounting face  12  will be mounted against a suitable support or reaction structure illustrated generally by the dotted line  80 . As shown in  FIG. 5 , it is assumed there is no relative movement of the reaction surface  80 . Thus, deformation of the expandable structure  30 , as well as general deflection of the wall of the housing, means that the housing  20  will form a substantially sausage shape. As well, the general deflection of the wall of the housing, means that the housing  20  will form a substantially sausage shape as shown in  FIG. 5 . As shown, the occupant face  14  is no longer necessarily planar but is moved effectively closer to the occupant. This provides a greater distance for energy absorption before the occupant comes into contact with the mounting surface  80 . As shown in  FIG. 6 , the auxiliary portion  40  has hingedly moved relative to the main portion by expansion of the expandable area  42  through expansion of the at least one pleat  44 . 
       FIG. 9  illustrates, in perspective, an alternative embodiment of the invention. In  FIG. 9 , the bolster shown generally at  100  includes a mounting face  112  and an occupant face  114 . The bolster  100  is an active bolster and includes an extension structure  116  located at the left hand end of bolster  100  as illustrated in  FIG. 9 . The bolster  100  includes a housing  120 . The housing  120  defines a substantially closed chamber  122 . In many respects the bolster  100  is similar to the bolster  10  illustrated in  FIG. 1 . 
     The bolster  100  includes a main portion  121  and an auxiliary portion  140 . The extension structure  116  comprises in part the auxiliary portion  140 . The auxiliary portion  140  is an integral part of the housing  120  and is also a hollow structure. The auxiliary portion  140  includes an auxiliary chamber  123 . 
     The extension structure  116  also includes an expandable area  142 . The expandable area  142  preferably includes at least one pleat  144 . In this respect, the embodiment illustrated in  FIG. 9  operates similar to the embodiment illustrated in  FIG. 1 . 
     The principal difference between these two embodiments however is the ability to change the rate at which the activating fluid flows into the auxiliary chamber  123 . The source of inflating fluid to cause activation of the bolster is first directed to the chamber  122  in main portion  120 . To control the rate of flow of activating fluid from the main portion to the auxiliary portion, a restriction means including a limited flow path is provided. In this example, the expansion structure  116  includes a hollow rib  117 . The rib  117  is defined by slides which may be activated during the blow molding manufacturing process by setting out depressed areas  119  on either side of the rib. As shown in  FIGS. 11 ,  12  and  13 , the hollow rib  117  is formed by slides which move the mounting face  112  against the interior of the occupant face  114 . This provides a channel  121  for flow of fluid from the chamber  122  within the main portion  120  to the auxiliary chamber  123  within the auxiliary portion  140 . Also, as shown in this embodiment the rib  117  is itself in the form of a bellows so as to not restrict the desired movement of auxiliary portion  140  relative to main portion  121 . By selection of the number of ribs  117  and the sizing of those ribs, the inflation characteristics of the auxiliary portion  140 , can be controlled by the designer. 
     It is preferred that in operation, particularly with respect to an active bolster, that the main portion of the bolster first begin to modify its position relative to the vehicle occupant before movement of the auxiliary portion  140  to the deployed position. By providing a relatively restrictive flow path using at least one such rib  117 , the deployment timing of the auxiliary portion  140  can be selected as desired. Any number of ribs  117  having any particular size of flow channel or configuration may be utilized. By using at least one such rib, it is possible to obtain what is, in effect, a slightly delayed deployment of the auxiliary portion  140  relative to the time that the main portion  121  begins its deployment upon activation. 
       FIG. 14  illustrates a further embodiment and illustrates a bolster  200 . The bolster  200  is similar to the bolster  100  except that the extension structure  216  is provided to activate the movement of the auxiliary portion  240  relevant to the main portion  220 . In this case, the extension structure  216  includes an expandable area  242  which includes at least one pleat  244 . In this case the pleat  244  has a central depressed portion  245 , together with two grooves  247  which define the pleat  244 . 
     As shown in  FIG. 16 , the depressed areas  247  and  245  constitute therebetween, a pair of ribs  249  which extend vertically upwardly, as shown in  FIG. 14 . This in turn defines a pair of conduits  249 , each conduit having internally thereof a flow path  251 . Because the depressed areas  247  do not extend all the way to the lower edge of the pleat  244  as shown in  FIGS. 14 and 15 , there is a flow path for activating fluid, firstly from the main portion  220  to the first rib  249 , vertically upwardly through the first flow path  251  and then horizontally across the upper edge, as illustrated in  FIGS. 14 , and  15  and then downwardly through the second flow path  251  where it may then enter into the auxiliary portion  240 . Thus, the pleat  244  provides a serpentine path flow. This serpentine path flow by its length and cross-sectional size constitutes a restriction means which can also be used to provide a somewhat restricted flow and thus a slightly delayed deployment of the auxiliary portion  240  upon application of activating fluid to the main portion  220 . 
     Either of the bolsters  100  or  200  illustrated in  FIGS. 9 through 13  and  14  through  16  respectively, may be fitted with similar structures on the right hand end as depicted, or structures similar to structure  18  as discussed in association with the bolster of  FIG. 1 . It will also be possible to vary the number and location of the various flow channels to achieve the desired activation time delay as may be considered desirable. 
       FIG. 17  illustrates, in perspective, an alternative embodiment of the invention. In  FIG. 17 , the bolster shown generally at  300  comprises a housing  302  which includes a mounting wall  304  and an occupant wall  306  which is opposite thereto. The mounting wall  304  comprises an exterior mounting face  308  which, when installed, faces the reaction structure of the vehicle. The occupant wall  306  comprises an exterior occupant face  310  which, when installed, faces the vehicle interior and any occupants therein. 
     As shown in  FIG. 18 , a substantially closed volume  310  is formed between the mounting wall  304  and the occupant wall  306 . The bolster  300  further comprises a source of pressurized fluid  312  which is mounted to the housing  302  and, as discussed above, serves to inflate the bolster  300  by injecting pressurized fluid into the volume  310 , In the illustrated embodiment, this source  312  is a cartridge. 
     The housing  302  comprises a first and a second restriction means  314   a  and  314   b  formed between the mounting wall  304  and the occupant wall  306  for restricting the flow of the fluid injected by the source  312 . The restriction means  314   a  and  314   b  restricts the fluid flow between different areas  316 ,  320   a  and  320   b  of the housing  302 . 
     Similar to the hollow rib  117  of  FIGS. 9 to 13  and the pleat  244  of  FIGS. 14 to 16 , the restriction means  314   a  and  314   b  separate the housing  302  into a main chamber  316  into which the source  312  injects pressurized fluid and respective auxiliary portions  320   a  and  320   b.    
     In the embodiments illustrated, the restriction means  314   a  and  314   b  both comprise depressed areas  314   a  and  314   b , similar to the depressed area  119  of  FIGS. 9 to 13  and the depressed areas  245  and  247  of  FIGS. 14 to 16 . These areas  314   a  and  314   b  are preferably formed during molding of the housing  302  and formed by compressing the mounting wall  304  until it meets the occupant wall  306  such that once molded the two walls  304  and  306  are in contact. It will be appreciated however that the occupant wall  306  could similarly be compressed into the mounting wall  304 . The depressed areas  314   a  and  314   b  are sealingly bonded together in order to prevent air from seeping through. 
     In the embodiment illustrated, the depressed area  314   a  does not extend the entire width of the housing. The depressed area  314   a  comprises a channel  322  at the end  324  which connects the main chamber  316  with the interior of the auxiliary portion  320   a , which here forms a hollow auxiliary chamber  318   a . During deployment of the bolster  300 , fluid flows from the source  312 , into the main chamber  316 , through the channel  322  and into the auxiliary chamber  318   a.    
     As before, by forcing the pressurized fluid through the channel  322 , the rate at which the fluid enters the auxiliary chamber  318   a , and hence the rate of inflation of the auxiliary chamber  318   a , will differ from that of the main chamber  316 . In particular, choking the fluid flow at the channel  322  can enable a slightly delayed deployment of the auxiliary portion  320   a . By varying the diameter and shape of the channel  322 , the relative rates of inflation of the main and auxiliary chambers  316  and  318   a  can be adjusted. 
     It will be appreciated that, in contrast with the auxiliary portions of the previous figures, the auxiliary portions  320   a  and  320   b  are not provided with an extension structure. 
     In the embodiment illustrated, auxiliary portion  320   b  consists of the depressed area  314   b . In other words, the portions of the mounting wall  304  and the occupant wall  306  which form the auxiliary portion  320   b  have been compressed and no fluid can travel in or out thereof. As such, the auxiliary portion  320   b  will not inflate. It will be appreciated that such a non-inflating portion of the bolster  300 , whose occupant face  310  may be subject to various additional esthetic and/or packaging constraints, advantageously enables a variety of design options which might not be available given a conventional bolster whose entire housing was inflated. 
       FIGS. 19 and 20  illustrate another embodiment of the invention which is similar to that of  FIGS. 17 and 18 . As before, a bolster  400  similarly comprises a housing  402  formed by a mounting wall  404  and an occupant wall  406 , which surround a substantially closed volume  410  therebetween. The housing  402  is divided by restriction means  414   a  and  414   b , which here comprise depressed areas  414   a  and  414   b , into a main chamber  416  and two auxiliary portions  420   a  and  420   b.    
     In the embodiments illustrated, and in contrast with the equivalent elements in  FIGS. 17 and 18 , the depressed area  414   a  extends the entire width of the housing  402 , such that both ends  424  of the depressed area  414   a  engage the lateral side  426  of the housing  402 . Therefore, there is no channel formed by the depressed area  414   a  between the main area  416  and the auxiliary chamber  418   a  formed by the auxiliary portion  420   a . The auxiliary chamber  418   a  is isolated as there is little to no fluid communication between it and the main chamber  416 . As such, auxiliary portion  420   a  will not inflate. 
     The auxiliary portion  420   b  is equivalent to the auxiliary portion  320   b.    
       FIGS. 21 and 22  illustrate another embodiment of the invention. As before, a bolster  500  similarly comprises a housing  502  formed by a mounting wall  504  and an occupant wall  506 , which enclose a substantially closed volume  510  therebetween. The housing  510  is divided by a restriction means  514 , which here comprises a semi-circular depressed area  514 , into a main chamber  516  and an auxiliary portion and chamber  520  and  518 . 
     In this embodiment, the distance between the mounting wall  504  and the occupant wall  506  is locally decreased by the depressed area  514 , that is to say the portions of the mounting wall  504  and the occupant wall  506  at the depressed area  514  are closer to each other than in the main chamber  516  and the auxiliary chamber  518 . The walls  504  and  506  have not been completely compressed and are therefore not in contact. As such, it will be appreciated that the depressed area  514  only partially blocks fluid flow thereacross. However, such a decrease will nevertheless have an effect on the relative inflation rates of the main and auxiliary chambers  516  and  518 . 
     A pair of channels  522  is formed between either end  524  of the semi-circular depressed area  514  and the lateral side  526  of the housing  502 . The magnitude of the local decrease in the distance between the mounting wall  504  and the occupant wall  506  caused by the depressed area  514 , in addition to the diameter and shape of the channels  522 , will determine the relative inflation rates of the main and auxiliary chambers  516  and  518 . 
     It will further be appreciated that an alternate channel could be provided which increases the local distance between the mounting wall  504  and the occupant wall  506  and may thereby increase flow to a given area. 
     In accordance with some of the embodiments illustrated and described herein, it will be recognized, that a bolster has been provided having an un-deployed length L measured in a direction referred to as the transverse direction. Upon deployment, utilizing either of the embodiments as described herein, the bolster may gain an additional length in that transverse direction by expansion of an extension structure to provide increased lateral length. The orientation of the bolster may be selected as desired by the vehicle designer and thus the directions, vertical and horizontal are given only by way of illustrative example and not by limitation. In fact, the bolster may be active or inactive and may be located in the vehicle as desired and in any orientation desired. 
     In accordance with some of the embodiments illustrated and described herein, it will further be recognized that a bolster has been provided having an auxiliary chamber with different deployment timing and or characteristics from that of a main chamber. In particular, as described herein, a restriction means and flow channel may be provided which restricts fluid flow to the auxiliary chamber, thereby delaying deployment. Alternatively, as described herein, a restriction means may be provided which blocks fluid flow to the auxiliary chamber entirely, thereby providing a portion which will not inflate when the bolster is deployed. 
     In accordance with the embodiments illustrated and described herein, it will be recognized, that a bolster has been provided having an un-deployed length L measured in a direction referred to as the transverse direction. Upon deployment, utilizing either of the embodiments as described herein, the bolster may gain an additional length in that transverse direction by expansion of an extension structure to provide increased lateral length. The orientation of the bolster may be selected as desired by the vehicle designer and thus the directions, vertical and horizontal are given only by way of illustrative example and not by limitation. In fact, the bolster may be active or inactive and may be located in the vehicle as desired and in any orientation desired. 
     All descriptions and illustrations contained herein are to be taken by way of example only and reference shall be made to the claims for the full scope and extent of the invention.