Abstract:
An inflatable restraint system with selectable ventilation, including a base plate defining a vent aperture, an inflatable cushion secured to the base plate, and a single conventional inflator for inflating the inflatable cushion with inflation gas. In some vehicle impacts, the vent aperture remains sealed with a vent plug, which inhibits ventilation of the inflation gas from the inflatable cushion through the vent aperture. In other vehicle impacts, depending on the placement and force of the impact, the speed and direction of the vehicle, and the size and placement of the passengers, the energy absorption characteristics of the inflatable cushion may be controlled. This is accomplished by an initiator, which may be selectively activated to rupture the vent plug and thereby allow selective ventilation of the inflation gas through the vent aperture.

Description:
TECHNICAL FIELD OF THE INVENTION 
     This invention generally relates to inflatable restraint systems for motor vehicles. More specifically, this invention relates to inflatable restraint systems that use selectable ventilation to control the energy absorbing characteristics of the inflatable restraint. 
     BACKGROUND 
     In a conventional inflatable restraint system, a sensor is used to detect the occurrence of a vehicle impact and, upon such occurrence, to deploy an inflatable cushion. Once deployed with inflation gas, the inflatable cushion provides a layer between the passenger of a vehicle and the hard surfaces of an automotive interior during vehicle impact. These systems are highly effective and have saved lives in thousands of vehicles. For some passenger and impact situations, however, the conventional inflatable restraint systems are not optimized. These situations may occur, for example, with passengers who are much smaller than the average adult, with passengers who are unbelted or “out-of-position,” or in low severity impacts. In such cases, conventional inflatable restraint system may deploy an inflatable cushion with less-than-optimal energy absorption characteristics, such as excessive force. 
     Various techniques have been explored to control the energy absorption characteristics of the inflatable cushion. One such technique uses a dual level inflator. In these systems, a first inflator charge is used to deploy the inflatable cushion with inflation gas upon the detection of a vehicle impact, and the second inflator charge is used to further inflate the inflatable cushion only in response to specific situations. These techniques, however, suffer from the expense and complication of using such a dual level inflator. 
     Another such technique, as described in U.S. Pat. No. 5,074,583 (Fujita et al.), uses a discharge valve to allow ventilation of the inflatable cushion when the pressure in the inflatable cushion reaches a certain level. The ventilation of the inflatable cushion through the discharge valve limits and reduces the pressure in the inflatable cushion and may prevent the deployment of an inflatable cushion with excessive force. This technique, however, only allows control of the pressure of the inflatable cushion and does not allow any control of the energy absorption characteristic of the inflatable cushion in response to different passenger and impact situations. 
     Other, more recent, techniques use movable shutters, instead of discharge valves, that may be selectively activated. The ventilation of the inflatable cushion through the movable shutters also alters the energy absorption characteristics of the inflatable cushion by reducing the pressure in the inflatable cushion. Unlike the discharge valve technique, the movable shutters allows control of the energy characteristics of the inflatable cushion in response to different passenger situations. But, because of the slow response of the mechanical shutters, these techniques do not allow control of the energy absorption characteristics of the inflatable cushion in response to low severity impacts. Vehicle impacts occur too fast for a determination of a low severity impact and for an appropriate mechanical response. 
     Thus, the current techniques in the art fail to provide a simple, cost-effective technique to control the energy absorption characteristics of the inflatable cushion in response to passengers who are much smaller than the average adult, passengers who are unbelted or “out-of-position,” and low severity impacts. 
     SUMMARY OF THE INVENTION 
     This invention provides for an inflatable restraint system that overcomes the problems and disadvantages of the conventional techniques in the art. Additionally, the present invention provides for an inflatable restraint system that controls the energy absorption characteristics of the inflatable cushion in response to passengers who are much smaller than the average adult, passengers who are unbelted or “out-of-position,” and low severity impacts. Further, the present invention provides for an inflatable restraint system that can be easily modified during testing procedures and for optimal performance in different vehicles. 
     The invention includes an inflatable restraint system with a base plate defining a vent aperture, an inflatable cushion secured to the base plate, and a single conventional inflator for inflating the inflatable cushion with inflation gas. In some vehicle impacts, the vent aperture remains sealed with a vent plug, which inhibits ventilation of the inflation gas from the inflatable cushion through the vent aperture. In other vehicle impacts, depending on the placement and force of the impact, the speed and direction of the vehicle, and the size and placement of the passengers, the energy absorption characteristics of the inflatable cushion may be controlled. This is accomplished by an initiator, which may be selectively activated to rupture the vent plug and thereby allow selective ventilation of the inflation gas through the vent aperture. Further, by using base plates with a smaller or larger vent aperture size, the ventilation characteristics, such as the flow rate, of the inflatable restraint system can be easily modified during testing procedures and for optimal performance for different vehicle applications. 
     Further features and advantages of the invention will become apparent from the following discussion and accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective, exploded representation of the invention; 
     FIG. 2 is a back view of the invention; 
     FIG. 3 is a cross-sectional view of the invention taken along the line  3 — 3  in FIG. 2; and 
     FIG. 4 is a cross-sectional view of the invention taken along the line  4 — 4  in FIG.  2 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The following description of the preferred embodiment is merely exemplary in nature, and is in no way intended to limit the invention or its application or uses. 
     The inflatable restraint system  10  of the present invention is shown in FIGS. 1 through 4. As shown in these figures, the inflatable restraint system  10  generally includes a base plate  20 , an inflator  30 , a cushion ring  40 , an inflatable cushion  50 , a trim cover  60 , a vent plug  70 , and an initiator  80 . 
     The base plate  20  acts as the main anchor point for the entire inflatable restraint system  10 . The base plate  20  includes vent apertures  22 , mounting holes  24 , a device aperture  26 , and trim cover tabs  28  arranged around the perimeter of the base plate  20 . In alternative embodiments, as discussed below, the vent apertures  22  may include one or more apertures, each of any shape. The particular amount, size, and shape of the apertures determine the cross-sectional area of the vent apertures  22  and, hence, affect the flow rate of inflation gas through the vent apertures  22 . The base plate is made of a high-strength material, such as steel. 
     The inflator  30 , which is mounted to the back side of the base plate  20 , generates inflation gas on the front side of the base plate  20  into the inflatable cushion  50 . The inflator  30  includes a base with mounting holes  32 , aligning with the mounting holes  24  of the base plate  20 . The inflator  30  is a conventional device that generates inflation gas for inflatable restraint systems. In the preferred embodiment, the inflator  30  is mounted to the back side of the base plate  20 . In alternative embodiments, however, the inflator  30  may be mounted in a different area of the vehicle and may simply supply the inflation gas to the front side of the base plate  20  through a tube or any other medium. The inflator  30  is well known and used in the art of inflatable restraint systems and its implementation in the system of the present invention would be readily understood by one of ordinary skill in the art. 
     The cushion ring  40 , which is mounted to the front side of the base plate  20 , includes mounting bolts  42  and a device aperture  44 . The mounting bolts  42  extend from the back side of the cushion ring  40  through the mounting holes  24  of the base plate  20 , and through the mounting holes  32  of the inflator  30 . The cushion ring  40  and the mounting bolts  42  are made of a high-strength material, such as steel. The device aperture  44 , like the device aperture  26  of the base plate, is designed to allow the inflator  30  to project towards the inflatable cushion  50 . The device aperture  44  of the cushion ring  40 , however, is enlarged and does not block the vent apertures  22 . 
     As shown in FIG. 3, the inflatable cushion  50  is attached to the front side of the cushion ring  40 . The trim cover  60  is attached to the base plate  20  over the trim cover tabs  28  and surrounds the entire inflatable cushion  50 . The inflatable cushion  50  and the trim cover  60  are both well known and used in the art of inflatable restraint systems and their implementation in the system of the present invention would be readily understood by one of ordinary skill in the art. 
     The vent plug  70  substantially seals the vent apertures  22  and inhibits ventilation of the inflation gas from the inflatable cushion through the vent apertures  22 . The vent plug  70  includes mounting holes (not shown) to receive the mounting bolts  42  of the cushion ring  40 . As shown in FIG. 2, mounting nuts  72  are tightened onto the mounting bolts  42  to secure the vent plug  70  and the inflator  30  to the back side of the base plate  20 . The vent plug  70  also includes preformed tear seams  74  located near the mounting holes. The vent plug  70  is made of a low-strength material, such as nylon, that will withstand the internal pressures of a filling and filled inflatable cushion, but that will rupture upon a pyrotechnic explosion. 
     As shown in FIG. 4, the initiator  80  is insert molded into the vent plug  70 . In alternative embodiments, the initiator  80  is secured against the vent plug  70 , or may be simply placed between the vent plug  70  and the base plate  20 . The initiator includes a small filament (not shown) that generates heat upon the receipt of an electrical impulse and ignites a pyrotechnic material (not shown), which supplies the explosion and ruptures the vent plug  70 . During the explosion of the pyrotechnic material, the force of the explosion pushes against the base plate  20  and the vent plug  70 . Since the base plate  20  is made of a high-strength material, and the vent plug of a low-strength material, the vent plug  70  ruptures. Ideally, the rupture of the vent plug  70  occurs along the preformed tear seams  74 , as shown in FIG.  2 . The rupture of the vent plug  70  exposes the vent apertures  22 , which form an escape route for the inflation gas and, hence, controls the energy absorbing characteristics of the inflatable restraint. Initiators with filaments and pyrotechnic material are well known and used in the art of inflatable restraint systems and their implementation in the system of the present invention would be readily understood by one of ordinary skill in the art. 
     The front side of the inflatable restraint system  10  is assembled by placing the cushion ring  40 , already attached to the inflatable cushion  50 , near the front side of the base plate  20  and inserting the mounting bolts  42  through the mounting holes  24 . Then, the trim cover  60  is placed over the inflatable cushion  50  and secured to the trim cover tabs  28  of the base plate  20 . The back side of the inflatable restraint system  10  is assembled by placing the inflator  30  near the back side of the base plate  20  and positioning the mounting holes  32  over the mounting bolts  42 . Then, the vent plug  70  with an initiator  80  is placed near the back side of the base plate  20  and the mounting holes (not shown) are positioned over the mounting bolts  42 . Finally, the mounting nuts  72  are tightened onto the mounting bolts  42  to secure the entire inflation restraint system  10 . 
     During the operation of the present invention in a vehicle impact, a sensor (not shown) sends a signal, with two portions, to the inflation restraint system  10 . The first portion of the signal activates the inflator  30  to generate inflation gas, which pushes the inflatable cushion  50  through the trim cover  60  and fills the inflatable cushion  50 . The second portion of the signal selectively activates the initiator  80 . Upon such selective activation, the second portion of the signal directs an electrical impulse to the initiator  80 , causing the filament to heat, the pyrotechnic material to burn and explode, and the vent plug  70  to rupture along the preformed tear seams  74 . The rupture of the vent plug  70  causes a “short-circuit” and the inflation gas follows this short circuit and escapes through the vent apertures  22  of the base plate  20 , altering the energy absorbing characteristics of the inflatable cushion  50 . The determination to ventilate the system through selective activation of the initiator  80 , and the determination of the precise time to ventilate the system, is based on several factors, including the placement and force of the impact, the speed and direction of the vehicle, and the size and placement of the passengers. 
     In the preferred embodiment of the present invention, the vent plug  70  substantially seals the vent apertures  22  and prevents ventilation of the inflation gas from the inflatable cushion  50  through the vent apertures  22 . Alternatively, the vent plug  70  may merely inhibit ventilation of the inflation gas in order to aid or replace the vents located in some conventional inflatable cushions. In either case, the vent plug  70  is designed to perform in a similar manner at zero inflation as well as at full inflation of the inflatable cushion  50 . In other words, if the initiator  80  is not selectively activated during a vehicle impact, the vent plug  70  will either prevent or inhibit, depending on the specific design of the inflatable restraint system, ventilation of the inflation gas even during full inflation of the inflatable cushion  50 . 
     During testing of the inflation restraint system  10  for different ventilation flow rates, the same design for the vent plug  70  and the initiator  80  can be used throughout. Only the size of the vent apertures  22 , which can be drilled larger or smaller, needs to be altered. Further, during the installation of the inflation restraint system  10  in different vehicles, the same design for the vent plug  70  and the initiator  80  can be used and, again, only the size of the vent apertures  22  needs to be altered. Thus, the present invention provides for an inflatable restraint system that can be easily modified during testing procedures and for optimal performance in different interiors. 
     The foregoing discussion discloses and describes a preferred embodiment of the present invention. One skilled in the art will readily recognize from such discussion, and from the accompanying drawings and claims, that changes and modifications can be made to the invention without departing from the true spirit and fair scope of the invention as defined in the following claims.