Abstract:
An opening apparatus for a gas pressure container for inflating an airbag is provided. A housing is fixedly connected to the container and communicates therewith via a discharge opening. The housing includes a principal member that has oppositely disposed open ends. A sealing element for initially sealing the discharge opening is supported by a pressure piece on a counterbearing against opening forces acting on the sealing element via gas pressure in the container. A triggering device is provided that when activated removes support for the sealing element so that the discharge opening is opened by gas pressure in the container for inflating the airbag. The triggering device is in the form of a separate unit that is independently mountable on the housing and is held n one of the end plates. Support of the sealing element is stable independently of the triggering device.

Description:
BACKGROUND OF THE INVENTION 
     The invention relates to an opening apparatus for a gas pressure container for inflating an airbag comprising a housing that is securely connected to the container at the discharge opening thereof. A sealing element seals the discharge opening and is supported by a pressure piece on a counterbearing against the opening forces acting on the sealing element via the gas pressure in the container. A tripping device is provided that when tripped or activated removes the support for the sealing element so that the discharge opening is opened by the gas pressure in the container and the airbag is inflated. The support of the sealing element is stable independent of the tripping element. 
     Such an opening apparatus is known from DE 195 40 618 A1. The discharge opening of the pressure container is closed by means of a sealing element that is supported on a counterbearing fixed in the housing for supporting the gas forces via a pressure member. The pressure member has a pyrotechnic charge that destroys the counterbearing when ignited and thus removes the support for the sealing element. The sealing element is now destroyed by the gas pressure in the container and the airbag attached to the housing is inflated by the gas flowing out. 
     Known from DE 197 27 047 is filling the gas pressure container with an inert gas, e.g., at least one gas from the nitrogen, argon, and helium group. The gas pressure containers thus filled are closed by a bursting disk that is joined to the gas pressure container and that is opened by the explosion pressure of a pyrotechnic charge. 
     The filled gas pressure containers are manufactured by suppliers and shipped to end users. The gas pressure containers ready for shipping contain operational opening apparatuses, each comprising a pyrotechnic charge, which is why cautious handling is necessary during manufacture, shipping, and final installation in order to avoid inadvertent actuation of the apparatus. 
     In addition, it has been determined that gases stored in the gas pressure container must be present in a particular mix in order to ensure rapid and correct inflation of the airbag without mechanical damage. 
     The object of the invention is to further develop an apparatus of the aforementioned type such that it is assured that the airbag will open immediately regardless of the gases used and without the inflating process causing mechanical damage. 
     SUMMARY OF THE INVENTION 
     This object is achieved in accordance with the invention in that the housing, which is open on opposing ends, comprises a principal member that is connected to the pressure container, wherein the open ends can be closed off by end plates, and wherein the tripping or triggering device is in the form of a separate unit that is independently mountable on the housing and is held in one of the end plates. 
     The throttling means is provided in the direction of discharge of the gases in front of the discharge opening in the gas pressure container, and the reason for this is two-fold. First, the discharge opening can have a large diameter, which means that the gas pressure acts on a correspondingly large surface area and large opening forces are available that provide explosion-type opening of the pressure container when the pressure piece is absent. In contrast, the discharge speed of the gas is determined by the throttling means, which is selected according to the gas filling and installed securely when the container is manufactured. Preferably the pressure container is filled with an inert gas, especially helium or a helium mix, the discharge speed of the gas being constructively pre-determined by the throttling means. Helium is not highly temperature sensitive; its flow speed is high because of its low molecular weight and the flow speed can be adapted with the throttling means to the airbag to be filled. 
     In a further development of the invention the tripping device embodies a unit separate from the housing that is independently mountable. Since the support for the sealing element is stable independent of the tripping device, the opening apparatus can be preassembled with the gas pressure container without the tripping device. It is useful for the housing to remain open on opposing sides so that if the sealing element is inadvertently opened the gas under pressure flows out of equivalent opening areas on opposing sides and the reaction forces are thus thrust-neutral. Thus the gas pressure container moves only slightly or does not move at all so that a high degree of safety is achieved during pre-assembly, shipping, and final assembly without additional complexity. The tripping device is pre-assembled separate from the opening apparatus and the gas pressure container. The opening apparatus for the gas pressure container is not provided the tripping device until final assembly, when the overall arrangement is made operational. By this time, however, the gas pressure container is securely mounted so that thrust forces that occur due to discharging gases are captured. 
     Preferably the housing embodies a principal member that is joined to the pressure container and that comprises open ends that can be closed by end plates. The principal member can be closed for shipping by temporary end plates that each have discharge openings equal in size. This can assure that the opening apparatus in the housing is not damaged. The tripping device mounted in one end plate is not attached to the principal member until final assembly, wherein the end plate opposite the tripping device can have the necessary discharge openings for the fill gas for the airbag; it is useful for the airbag to be attached to this end plate. 
     In order to assure that the tripping device is installed in the correct position, the open edge of the end of the principal member engages in a groove in the end plate. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Additional features of the invention result from the additional claims, description, and drawing, in which the exemplary embodiments of the invention are described in detail in the following: 
     FIG. 1 is a perspective drawing of a gas pressure container comprising an opening apparatus arranged at one end; 
     FIG. 2 is a perspective drawing in accordance with FIG. 1 with the opened housing of the opening apparatus; 
     FIG. 3 is a cross-sectional schematic diagram of a first exemplary embodiment of the opening apparatus comprising a pyrotechnic tripping device; 
     FIG. 4 is a schematic diagram of a second embodiment of the opening apparatus comprising a thermoelectric tripping device; 
     FIG. 5 is a schematic diagram of another principal member of a gas pressure container comprising a dual opening apparatus with an electric tripping device; 
     FIG. 6 illustrates a gas pressure container in accordance with FIG. 5 comprising a pyrotechnic tripping device; 
     FIG. 7 is a section through a gas pressure container comprising throttling means; 
     FIG. 8 is a partial section through a gas pressure container comprising an end cap opposing the discharge opening; 
     FIG. 9 is a radial section through the tripping device-in accordance with FIG.  8 . 
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
     The gas pressure container I illustrated in FIG. 1 inflates an airbag  2  as employed, e.g., in motor vehicles. 
     As can be seen in FIGS. 2 and 3, fastened to the central discharge opening  3  of the pressure container  1  is a housing  4  that is securely connected to the container  1 . The discharge opening  3  is preferably disposed coaxially with the central longitudinal axis  48  of the container  1 . 
     FIGS. 1,  2 , and  7  provide the structure of the housing  4  with greater precision, while FIGS. 3 through 6 merely contain sketches of the housing  4  and FIGS. 8 and 9 provide an alternative housing. 
     As illustrated particularly in FIG. 2, the housing  4  comprises a hollow principal member  5  comprising mutually opposing open ends  6  and  7  that are closed by means of the end plates  8 ,  9 . As is evident from FIG. 1, the end plates  8  and  9  are larger than the ends  6  and  7  so that the end plates  8  and  9  overhang the principal member  5 . Provided in the overhanging segments  10  are through-holes  11  for arranging, connecting or tie-rods  12 . The end plates  8  and  9  are usefully embodied identically in terms of size such that the through-holes  11  of the mutually opposing end plates  8  and  9  are congruent and permit the arrangement of each tie 15  rod  12 . In order to assure positionally correct assembly of the end plates to the principal member  5 , a groove  13  is provided on the side of the end plates  8  and  9  facing the principal member  5  for the edge  14  of the open ends  6  and  7 . When the end plates  8  and  9  are assembled such that the ends  6  and  7  are closed, the edge  14  of the principal member  5  engages the groove  13  of each end plate and thereby assures positionally correct assembly with the principal member  5 . This arrangement also assures precisely-aligned, mutually correct positioning of the through-holes  11  for installing the tie-rods  12 . Three tie-rods  12  are provided around the circumference of the end plates  8 ,  9 . One tie-rod  12  approximately intersects the center longitudinal axis  48  of the pressure container  1  in an extension of the pressure piece over the opening apparatus. The other two tie-rods  12  are disposed adjacent to the neck of the pressure container  1  to the left and right next to the housing  4 . All three tie-rods  12  are disposed parallel to the longitudinal central axis  45  of the housing  4 , which is perpendicular to the end plates  8  and  9 . 
     The discharge opening  3  of the gas pressure container  1  opens approximately centrally into the housing  4 , i.e., its principal member  5 , which is rectangular in cross-section in the exemplary embodiment illustrated. Other cross-sectional shapes of the principal member  5  can be advantageous (FIG.  8 ). In order to obtain thrust-neutrality when the end plates  8  and  9  are uninstalled, the housing  4 , i.e., principal member  5 , is open on opposing sides  6 ,  7 . The open sides  6 ,  7  preferably have the same area; the central axis perpendicular to each end  6 ,  7  is coaxial with the longitudinal central axis  45  of the principal member  5  or housing  4 . The central longitudinal axis  48  of the pressure container  1  intersects the longitudinal central axis  45  of the housing  4  at a right angle. 
     The discharge opening  3  is closed by a sealing element  15  that is thin film in the exemplary embodiment illustrated and that is mounted on the side of the discharge opening  3  in the pressure container  1  that faces away from the housing  4 . The sealing element  15  is preferably attached pressure-proof to the container housing  17  in the region of the film edge  16 . Depending on the material the film is made of, its edge  16  can be joined or bonded to the container housing  17 . 
     The sealing element  15  on the side facing the housing  4  is adjacent to a support disk  18  that is placed in the discharge opening  3 . 
     The support disk  18  is disposed with radial play to the edge  19  of the discharge opening  3 , thus forming an annular gap  20  that is closed on the container side by the sealing element  15 . This annular gap  20  constitutes a pressure relief valve; the design of the annular gap is contrived in association with the material of the sealing element  15  such that at a prespecifiable pressure limit the sealing element  15  ruptures in the region of the annular gap so that the overpressure is discharged in a controlled manner through the annular gap  20  without the discharge opening  3  itself opening. FIGS. 8 and 9 illustrate a gas pressure container with no annular gap. 
     The support disk  18  is supported by a pressure piece  21  on a counterbearing or support  22  fixed in the housing so that the opening forces that act upon the sealing element  15  through the gas pressure in the container  1  are captured with certainty. The round end  23  of the pressure piece  21  is situated in a corresponding concave bearing or support  24  in the support disk  18 , while the other end  25  of the pressure piece  21  has a slightly concave depressed rest  26  with which the pressure piece engages lightly on a bolt  27  constituting the counterbearing  22 . The bolt  27  is held in opposing holes  47  in the principal member  5 . The longitudinal axis  28  of the pressure piece  21  runs perpendicular to the support disk  18  and sealing element  15 , preferably runs through the axis of the bolt  27 , and coincides with the central longitudinal axis  48  of the container  1 . 
     Arranged transverse to the longitudinal axis  28  of the oblong, preferably cylindrical pressure piece  21  is a tripping or triggering device  30  that is mounted in an end plate  9  of the housing, as shown in FIG.  2 . The tripping device  30  together with the end plate  9  constitutes a unit  29  that is separate from the housing  4  and that can be installed independently. 
     The tripping device  30  essentially comprises an actuating piston  31  that is displaceably guided in a corresponding cylinder  32  transverse to the longitudinal axis  28 , wherein arranged in the cylinder  32  is a pyrotechnic charge  33  that can be ignited electrically in a known manner. The actuating piston  31 , adjacent to the counterbearing bolt  27  in the region of the end  25  rests on the pressure piece  21 , wherein the longitudinal axis  34  of the cylinder  32  is preferably disposed at a right angle to the longitudinal axis  28  of the pressure piece  21 . 
     As can be appreciated from FIG. 3, the support of the sealing element  15  by means of the support disk  18 , the pressure piece  21 , and the counterbearing  22  is stable and independent of the tripping device  30 , the depressed rest  26  also contributing to this. The gas pressure container  1  can therefore be operationally pre-installed and filled without the arrangement of the tripping device  30  and without the pyrotechnic ignition charge  33  being arranged. This is advantageous during pre-assembly, shipping, and in final assembly. The end plate  9  with the tripping device  30  that contains the pyrotechnic charge  33  is not affixed to the principal member  5  in the manner described in the foregoing until final assembly, wherein the end plate  8  arranged at the other end  6  has discharge openings  35  through which the airbag  2  attached preferably to the end plate  8  is inflated. 
     Instead of the pyrotechnic charge  33 , a purely electric or thermoelectric tripping device  30  is provided in the exemplary embodiment in accordance with FIG.  4 . Deviating from the support described in FIG. 3, the end  25  of the pressure piece  21  facing the bolt  27  inclines so that as a consequence of the forces acting in the direction of the arrows  36  on the pressure piece  21 , as a result of the inclined plane  37  on the end  25  of the pressure piece  21 , a resulting force  38  occurs which dislodges the pressure piece  21  from the counterbearing  22 . The resulting force  38  is intercepted by an electrically conducting, mechanically loadable wire  39 , wherein the wire  39  is fixed at one end in the pressure piece  21  by means of an insulating member  40  and is fixed at the other end in the housing  4  by means of an additional insulating member  40 . Soldered to the wire  39  are connecting cables  41  to the tripping device by means of which the wire  39  heats up in fractions of a second and is thus thermally weakened so that the wire  39  ruptures under the resulting force  38 , the end  25  of the pressure piece  21  is removed from the counterbearing  22 , and the sealing element  15  is no longer supported so that the gas pressure in the container  1  suddenly opens the sealing element  15  and the airbag  2  is inflated through the discharge openings  35 . It can be useful to embody the electrical tripping unit  30  like the pyrotechnic tripping unit  30  in FIG. 3 such that the unit is separate from the housing and can be installed independently. 
     The exemplary embodiment in accordance with FIG. 5 corresponds in principle to the tripping unit  30  described for the electric tripping unit in FIG. 4; identical reference numbers are therefore used for identical parts. The pressure gas container  1  in the exemplary embodiment in accordance with FIG. 5 comprises two round, separate individual containers; the housing  4  is provided in the center thereof. The torus-shaped ring has two discharge openings  3  and  3 a, wherein discharge opening  3   a  is smaller than discharge opening  3 . Arranged sealing elements  15  and  15   a  are supported in the same manner by support disks  18  and  18   a  and pressure pieces  21  and  21   a  against a common counterbearing  22 . Provided for each support is a separate holding wire  39  so that the discharge openings  3 ,  3   a  can be opened at different times. 
     In order to obtain favorable inflation characteristics in the airbag  2 , the discharge opening  3   a  of the one container is advantageously opened first in order then, after an interval of time, to open the larger discharge opening  3  of the other container for finally inflating the airbag. 
     The exemplary embodiment in accordance with FIG. 6 corresponds in principle to that in FIG. 5; identical reference numbers are therefore used for identical parts. 
     The two pressure pieces  21  and  21   a  are arranged at a common counterbearing  22 , wherein support of each sealing element  15  and  15   a  corresponds to an articulated lever and is stable without the arrangement of the pyrotechnic tripping device  30 . The ends  25  and  25   a  of the pressure pieces  21 ,  21   a  have depressed rests  26 ,  26   a  as described for the exemplary embodiment in accordance with FIG.  3 . The counterbearing  22   a  is held movable in a longitudinal slot  42  of the housing  4 , the actuating piston  31  of the pyrotechnic tripping device  30  engaging at the counterbearing  22   a . When tripped, the piston pushes the counterbearing  22   a  through the dead center of the articulated lever arrangement out of the illustrated stable position, wherein the support for each of the sealing elements  15  and  15   a  is removed and the discharge openings  3  and  3   a  are opened. 
     The exemplary embodiment in accordance with FIG. 7 corresponds in structure to that in FIG. 2; identical reference numbers are therefore used for identical parts. The principal member  5  constituting the housing  4  is joined to the neck of the pressure container  1  and has opposing open ends  6  and  7 . The end plate  9  has centering pins  42 . The support disk  18  is disposed with just a little play in the discharge opening  3  so that a film that is not very pressure resistant can be employed as sealing element  15 . Due to the small amount of play the support disk  18  has in the opening, the film is supported over substantially the entire opening cross-section of the discharge opening. 
     The opening cross-section, e.g., the diameter of the discharge opening  3 , is selected in terms of size such that the gas pressure acts on the support disk  18  with great opening force so that when tripped and the pressure piece  21  is pushed away, immediate explosive opening of the discharge opening  3  is assured. 
     Advantageously the pressure container is filled with a helium mixture, particularly however primarily helium or another suitable inert gas that is not highly temperature sensitive and that at the same storage pressure has a high inflation speed, which can be utilized advantageously for very brief airbag inflation times. 
     Throttling means  49  are provided in front of the discharge opening  3  in the pressure container  1  in the direction of discharge in order to preclude mechanical damage to the airbag with certainty. In the exemplary embodiment illustrated, the throttling means  49  is an apertured plate, wherein the throttle plate  49  is joined gas-tight to the container wall at its [the plate&#39;s ]exterior edge, preferably completely. The throttle orifice  50  is usefully disposed symmetrically to the center longitudinal axis  48  of the container housing  17  and particularly in line with the discharge opening  3 . The cross-section of the discharge opening  3  is larger, particularly larger by several times, than the cross-section of the throttle orifice  50 . In the exemplary embodiment a ratio of 3:1 has been selected; a ratio of about 8:1 is preferable. 
     The throttle plate  49  is situated approximately in the region of the tapering to the bottleneck at a distance d approximately parallel to the sealing element  15  and support plate  18 , so that formed in the bottleneck between the sealing element  15  and the throttle plate  49  is a pressure chamber  46  in which the same static pressure prevails as in the rest of the container housing  17 . After the discharge opening is opened, the pressure drops and is then determined by the gases flowing through the throttle orifice  50 . The distance d equals approximately half the diameter D of the throttle orifice  50 . 
     It is useful when the end plate  8  having the discharge openings  35  is provided a cup-shaped depression that projects into the airbag as a dome and that ensures its secure attachment 
     In the exemplary embodiment in FIGS. 8 and 9 the bottleneck comprising the throttle plate  49  and the discharge opening  3  and the sealing element  15  together with the principal housing  5  embody a pipe segment that is joined to a pressure container  1  at the one open end and that is closed at the other open end by means of a cap  8   a  that can be screwed on and off, that has discharge openings  35 , and that projects like a dome into the airbag. The tripping device  30  is screwed as a component into the cylindrical wall of the pipe segment perpendicular to the central longitudinal axis  48  (FIG.  9 ), whereby the opening apparatus is complete. 
     The specification incorporates by reference the disclosure of priority document DE 197 39 375.6 of Sep. 9, 1997. 
     The present invention is, of course, in no way restricted to the specific disclosure of the specification and drawings, but also encompasses any modifications within the scope of the appended claims.