Abstract:
A gas generator comprises an elongated, preferably tubular outer housing ( 10 ), at least one combustion chamber ( 26, 28 ) provided therein and filled with a solid propellant ( 30; 30 ′), and at least one igniter unit ( 16, 18 ) generating ignition gas for igniting the solid propellant ( 30; 30 ′). The igniter unit ( 16, 18 ) is arranged laterally and externally on the outer housing ( 10 ) in such a way and, in relation to the outer housing ( 10 ), a preferably radial ignition transfer opening ( 50, 58 ) is provided in the outer housing so that ignition gas generated in the igniter unit ( 16, 18 ) flows into the interior of the outer housing ( 10 ) via the ignition transfer  1  openings ( 50, 58 ).

Description:
TECHNICAL FIELD 
     The invention relates to a gas generator with an elongated, preferably tubular outer housing, at least one combustion chamber provided therein and filled with a solid propellant, and at least one igniter unit generating ignition gas for igniting the solid propellant. 
     BACKGROUND OF THE INVENTION 
     Elongated gas generators, also known as tubular gas generators, usually have an axial length which distinctly exceeds the diameter of the outer housing. The length generally amounts to more than twice the diameter. The gas generators are to make possible a rapid ignition of the propellant across a large area. A possible problem in the through-flow of the solid propellant through already generated gas is the erosion on the surface of the propellant, which can lead to an output development which is more difficult to calculate. The aim is therefore to achieve a “gentle” ignition of the propellant and to avoid an intense erosion of the propellant, whereby high pressure peaks in the combustion chamber can be avoided and at the same time the minimum pressure in the combustion chamber, necessary for combustion, can be maintained at a certain level for the entire duration of combustion. Furthermore, it is to be achieved that the solid propellant can be filled into the combustion chamber without any problems. 
     BRIEF SUMMARY OF THE INVENTION 
     According to the invention, a gas generator comprises an elongated, preferably tubular outer housing, at least one combustion chamber provided therein and filled with a solid propellant, and at least one igniter unit for igniting the solid propellant. The igniter unit is arranged laterally and externally on the outer housing in such a way and, in relation to the outer housing, a preferably radial ignition transfer opening is provided in the outer housing so that ignition gas generated in the igniter unit flows into the interior of the outer housing via the ignition transfer openings. In the gas generator proposed, the igniter unit thus does not project axially into the combustion chamber, but rather the igniter unit is arranged outside the outer housing, so that the so-called ignition gas can emerge from the igniter unit via the radial ignition transfer opening into the interior of the outer housing and, hence, into the combustion chamber. Through this so-called lateral ignition, on the one hand a greater ignition surface can be made available, and on the other hand the igniter unit no longer projects deep into the combustion chamber, which facilitates the filling process of the combustion chamber with solid propellant and leads to a better fixing in position with the use of propellant tablets. In addition, radial outflow openings are provided in the outer housing, so that the propellant bed comprised of solid propellant is not flowed through in axial direction, as in the prior art, and hence in its greatest extent, but rather is flowed through radially on a shorter path, which reduces the erosion of the propellant. 
     The igniter unit, in accordance with an embodiment, does not project into the r combustion chamber, so that the igniter unit in no way impedes the filling of the combustion chamber. The preferably cylindrical combustion chamber has an axially arranged filling opening. 
     The combustion chamber is to be constructed as far as possible without undercut, as already mentioned, e.g. is to be cylindrical, in order to make possible a complete and simple filling. With a cylindrical construction of the combustion, chamber, the longitudinal axis of the combustion chamber is to run parallel to the central axis of the outer housing, in order to achieve a compact construction. 
     The so-called ignition gases, i.e. the mixture of particles and gas which is produced by the igniter unit, can arrive into the combustion chamber even better distributed when a distribution space for the produced ignition gas is provided between the inner face of the outer housing and the combustion chamber wall. The ignition transfer opening also opens out into the distribution space. The distribution space preferably extends across the entire axial length of the combustion chamber, so that the gas spreads out from the igniter unit along the preferably elongated distribution space on the entire axial length and from there arrives across a very large area into the combustion chamber, which leads to a so called “gentle” ignition of the solid propellant. 
     According to the preferred embodiment, an expansion space for gas is arranged between the combustion chamber and outflow openings on the outer housing, which can likewise extend across the entire axial length of the combustion chamber. 
     The distribution or expansion spaces can be formed in that the combustion chamber wall, constructed as an insert, has at least one radially inwardly directed indentation, which as stated preferably runs across the entire length of the combustion chamber. 
     Except for the distribution and expansion spaces, the insert can lie with its entire surface against the inner face of the outer housing and can therefore be positioned so as to be securely in place. 
     The insert can be constructed as a single-layered filter or as a perforated sheet, which makes it possible to dispense with a thick filter insert in the entire gas generator. 
     A preferred embodiment makes provision that the outflow openings are arranged in a region lying diametrically opposite the ignition transfer opening, i.e. on one side there takes place the introduction of the ignition gases, which are firstly distributed axially, in order to then penetrate the propellant bed, and it is only on the opposite side that the generated gas can flow out from the gas generator. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a longitudinal sectional view through a first embodiment of the gas generator according to the invention, 
         FIG. 2  shows a cross-sectional view along the line II—II in  FIG. 1 , 
         FIG. 3  shows a longitudinal sectional view through a gas generator of the invention in accordance with a second embodiment along line III—III in  FIG. 4 , 
         FIG. 4  shows a cross-sectional view through the gas generator along line IV—IV in  FIG. 3 , 
         FIG. 5  shows a longitudinal sectional view through the gas generator of the 10 invention in accordance with a third embodiment, 
         FIG. 6  shows a cross-sectional view through the gas generator along line VI—VI in  FIG. 5  and 
         FIG. 7  shows a cross-sectional view through the gas generator of the t. invention in accordance with a further embodiment. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     In  FIG. 1  an elongated tubular gas generator is illustrated, which has a cylindrical outer housing  10 . The tubular gas generator consists of two stages  12 ,  14 , which can be activated independently of each other and have associated igniter units  16 ,  18 . The outer housing  10  of the gas generator is composed of two cylindrical tubes  20 ,  22  closed on one side, which are connected with each other by an intermediate wall  24 . Inside the outer housing  10 , each stage is provided with its own cylindrical and elongated combustion chamber  26 ,  28 , which is filled with solid propellant  30  in tablet form to form a propellant bed. The combustion chambers  26 ,  28  are formed by a combustion chamber wall  32  in the form of a cylindrical filter body insert, open on both sides and closed peripherally. This filter body lies on the inner face of the outer housing  12  across its entire surface, but has two radially inwardly directed indentations extending across its entire axial length, which lie in regions diametrically opposite the central axis A of the outer housing  10 . These indentations, together with the inner face of the outer housing  10 , delimit spaces extending across the entire axial length of each combustion chamber  26 ,  28 , namely a distribution space  40  and an expansion space  42  which is arranged in the region of outflow openings  44  in the outer housing  10 . Diametrically opposite the outflow opening  44 , there is provided for each igniter unit  16 ,  18  in the outer housing  10  an ignition transfer opening  50 . This is aligned radially to the central axis A. 
     Each igniter unit  16 ,  18  consists of a cup-shaped housing  52 , which is placed laterally from the exterior onto the outer housing  10 . In the housing  52 , an igniter  54  and a booster charge  56  are arranged. An ignition transfer opening  58  on the end face, running radially to the central axis A, allows the outflow of so-called ignition gases, i.e. the combustion products (gas and particles) on activation of the igniter  54  and combustion of the amplifier charge  56 . 
     In the region of the ignition transfer opening  58 , adjacent to the combustion chamber wall  32 , an axially short, curved baffle plate  60  is arranged, which does not have any openings. 
     With regard to the igniter units  16 ,  18 , it is to be emphasized that these can only lie against the outer face of the outer housing  10  or, as illustrated in  FIG. 1 , also partially project into the ignition transfer opening  50 . 
     In each case, however, the igniter units  16 ,  18  do not project into the combustion chambers  26 ,  28 . 
     For filling the combustion chamber, the two tubes  20 ,  22  are not yet connected with each other, so that they have one axial filling opening (open end) each. As the combustion chambers  26 ,  28  are constructed without undercuts, they can be filled completely and very simply axially with solid propellant  30 . Then in each case an elastic filling disc  70  is introduced, before both tubes  20 ,  22  are fastened to the intermediate wall  24 . 
     The mode of operation of the illustrated gas generator is explained below. When one of the igniters  54  is activated, a combustion of the booster charge  56  is brought about, and via the ignition transfer opening  58  hot ignition gas escapes from the housing  52  and flows radially out into the outer housing  10 . The ignition transfer opening  50  permits the inlet of the outflow gases into the interior of the outer housing  10 . The gas strikes directly onto the baffle plate  60  and is deflected axially through 90°, therefore is distributed on the entire length in the distribution space  40  and finally arrives into the corresponding combustion chamber  26 ,  28 . The solid propellant  30  is ignited across a large area and the resulting gases can leave the combustion chamber across a large area in the direction of the expansion space  42  and finally leave the outer housing  10  via the outflow openings  44 . 
     High peak pressures in the combustion chambers  26 ,  28  are avoided; a gentle ignition of the propellant takes place, the necessary minimum pressure being able to be kept at a certain level over the entire duration of combustion. 
     The embodiment according to  FIGS. 3 and 4  corresponds in part to that according to  FIGS. 1 and 2 , so that the reference numbers already introduced are used for parts having identical function and only the differences which exist need to be described in detail. 
     The solid propellant  30 ′ is constructed in disc form with a central opening. The discs, which are asymmetrical to the central axis, are stacked one on another and may have small extensions or protuberances on the end face for mutual spacing. Each combustion chamber  26 ,  28  has two stacks of solid propellant discs  30 ′, which in the region of the opening  58  for the central entry of gas are spaced apart from each other, for example by means of two sheet metal discs  72 . The sheet metal discs  72  have openings in the region of the holes  71 . It could therefore be stated that in the embodiment according to  FIG. 3 , each combustion chamber  26 ,  28  is divided into two smaller combustion chambers  126 ′,  126 ″ and  128 ′ and  128 ″. 
     For each stack of solid propellant discs  30 ′, in addition its own cylindrical filter body is provided, which forms the combustion chamber wall  32 . 
     As can be seen from  FIG. 4 , there are two peripherally spaced rows of outflow openings  44  in the outer housing  10 . The combustion chamber wall  32  has two indentations which each are associated with a row of outflow openings  44 , so that two expansion spaces  42 , seen in cross-section, are produced. The expansion spaces  42  extend across the entire length of each pack of solid propellant tablets  30 ′ and therefore across an associated, divided, separate combustion chamber  126 ′,  126 ″,  128 ′,  128 ″. 
     In this embodiment, the gas generated in the igniter unit  16 ,  18  flows via the ignition transfer opening  58  out from the corresponding igniter unit  16 ,  18  and radially into the outer housing  10 . The ignition transfer opening  50  permits the entry of the ignition gas into the interior of the outer housing  10 . The gas arrives into an intermediate space  80  and into a central channel  82  which is formed by the holes  71  into the solid propellant discs  30 ′, so that the solid propellant  30 ′ is ignited radially from the inside. The generated hot gas arrives into the expansion chambers  42 , from where it leaves the outer housing  10  via the outflow openings  44 . 
     The embodiment according to  FIGS. 5 and 6  corresponds substantially to that shown in  FIGS. 1 and 2 . Here, however, the baffle plate  60  is omitted. Instead of this, a nozzle-shaped extension  90  additionally projects out from the housing  52  into the distribution space  40 . The nozzle-shaped extension  90  has a radial ignition transfer opening  58 , which is constructed as a blind bore. This blind bore meets a through-bore  92  running perpendicularly hereto, which is aligned parallel  25  to the axis A. 
     The gas generated in the ignition unit  16 ,  18  is deflected through 90° in the nozzle-shaped extension  90  and leaves the latter in two streams which run parallel to the axis A in the direction of the distribution space  40 , from where it ignites the solid propellant  30  across a large area. The generated gas finally arrives into the expansion space and leaves the outer housing  10  via the outflow openings  44 . 
     In the embodiments shown, the ignition transfer openings  58  in the housing  52  direct the ignition gas into the outer housing  10 . If, however, the housing  52  does not partially project through the ignition transfer opening  50 , the ignition transfer opening  50  also directs ignition gas into the interior of the outer housing  10 . 
     The embodiment according to  FIG. 7  corresponds substantially to that shown in  FIG. 4 , the filter defining the combustion chamber wall  32  being omitted. To provide a distribution space  40  and an expansion space  42 , the solid propellant discs  30 ″ have flattened areas or indentations  100 .