Pyrotechnic gas generator for inflatable air-bag of a motor vehicle

Claim 1

Pyrotechnic gas generator (1) for an air bag intended to protect the occupants of a motor vehicle, comprising in particular: i) a hollow cylindrical body consisting of a circular base (2) extended by a cylindrical lateral wall (3) having, in proximity to the base (2), orifices (4) which connect inside and outside of the said hollow body, said wall (3) being terminated by a thinned end (5) and having an external shoulder (29) located under the orifices (4); ii) a circular closure ring (6) crimped into said thinned end (5) of the lateral wall (3), said ring having a central orifice (11) in which a cylindrical ignition device (14, 16, 17) which penetrates inside said hollow body is fixed in a gas-tight manner; iii) a pyrotechnic charge (18) in the form of an annular block, arranged inside said hollow body around the ignition device (14, 16, 17) and consisting essentially of a silicone binder and of a mixture of ammonium perchlorate and sodium nitrate, a height (h) of said annular charge (18) being less than a distance (d1) existing inside said hollow body between inner surfaces of the closure ring (6) and of the base (2), and a maximum thickness (em) of said annular charge (18) being less than a radial distance (d2) separating, inside said hollow body, the lateral wall (3) and the ignition device (14, 16, 17), so that the pyrotechnic charge (18) presents free surfaces which can all be covered by the gases originating from said ignition device (14, 16, 17); iv) wedging means (23, 24) which allow the gases to circulate and which are arranged between the closure ring (6) and the charge (18) and between the base (2) and the charge (18); v) a thin metal casing (25) interposed, inside said hollow body, between said charge (18) and both said lateral wall (3) and said base (2) so as to close off said orifices (4) in a gas-tight manner; vi) a deflector (35) and a condenser (38, 39, 40) which are wedged between an outer ring (30) supported by said external shoulder (29) and an external diffuser (33) crimped onto circumference of the base (2).