Dual stage hybrid inflator
An inflator for an airbag has a cylindrical housing forming a pressure vessel for storing inert gas within a first end portion; a second end portion forming a separate combustion chamber, and an intermediate diffusion portion interposed between the first and second end portions for exhausting gases from the inflator into an airbag. The inflator has a first gas generator subassembly disposed within the first end portion and in communication with the stored inert gas. A second gas generator subassembly has a combustion chamber which is disposed within the second end portion and isolated from the inert gas by one or more rupturable sealing disks. The actuation of the inflator can be accomplished such that one or both of the gas generators can be ignited. The ignition can be simultaneously or sequential permitting either very rapid full filling of the airbag or slower prolonged filling.
1 . An inflator for an airbag comprising:
a cylindrical housing forming a pressure vessel for storing inert gas within a first end portion; a second end portion forming a separate combustion chamber, and an intermediate diffusion portion interposed between the first and second end portions for exhausting gases from the inflator into the airbag;
a first gas generator subassembly disposed within the first end portion and in communication with the stored inert gas; and
a second gas generator subassembly disposed within the second end portion and isolated from the inert gas by one or more rupturable sealing disks.
2 . The inflator according to claim 1 wherein the first gas generator subassembly comprises a first igniter, and a first enhancer, a first gas generant, and a first gas generant subassembly housing, the gas generant housing retains the first gas generant and includes a plurality of apertures whereby the first gas generant is in communication with the stored gas before the first gas generant is ignited wherein a sealing disk is positioned within the first gas generant subassembly housing between the first enhancer and the first igniter to prevent leakage of stored gas out of the inflator.
3 . The inflator according to claim 1 wherein the intermediate diffuser portion has a first bulkhead adjacent the first end portion forming an internal end of the pressure vessel, the first bulkhead having one or more openings sealed by a rupture disk, and a second bulkhead adjacent the second end portion forming an internal end of the separate combustion chamber, the second bulkhead having one or more opening sealed by a rupture disk, interposed between said first and said second bulkheads are a plurality of radially aligned exhaust openings.
4 . The inflator according to claim 1 wherein the second gas generator subassembly comprises a second igniter, a second enhancer, contained in an end cap and a second gas generant contained in said separate combustion chamber and separated from said second enhancer by an end plate with opening sealed by a rupture disk.
5 . The inflator of claim 1 wherein the second gas generator subassembly further comprises a porous generant retaining means for controlling the gas generant volume and noise abatement.
6 . The inflator of claim 1 wherein the diffuser portion includes a porous filtration means between said first and second bulkheads covering said exhaust opening.
7 . The inflator of claim 1 wherein the first gas generator subassembly further comprises a cushion for controlling the gas generant volume and noise abatement.
8 . The inflator of claim 3 wherein the gas exits the inflator in a thrust neutral condition from directionally opposed radial openings.
9 . The inflator of claim 2 wherein the first end portion of the housing has a first end air tightly affixed to said housing, said first housing end having a central means for holding said first igniter and said first generant subassembly housing with said formed pressure vessel.
10 . The inflator of claim 9 wherein said first end further comprises a fill port opening for filling the inert gas, the fill port opening being permanently sealed upon filling of said gasses by a sealing means.
11 . The inflator of claim 1 wherein the plurality of apertures are situated along the length of the gas generant, wherein the apertures have a size and shape that does not allow pellets of gas generant to pass thereto, wherein the apertures are positioned to direct hot gasses generated from the burning of the gas generant toward the outer housing of the pressure vessel.
12 . The inflator of claim 1 wherein the cylindrical housing is formed with three or more substantially cylindrical portions welded together at circumferential ends.
13 . The inflator of claim 12 wherein each end of the cylindrical housing has an end closure welded to a cylindrical portion, each end closure includes an igniter which can be electrically connected to an actuation means.
14 . The inflator of claim 1 wherein the actuation means can selectively actuate either the first igniter alone, the second igniter alone or both igniters in a sequential delayed timing or simultaneously.
15 . The inflator of claim 1 wherein the inflator housing has an outside diameter of 50 mm or less.
16 . The inflator of claim 15 wherein the inflator housing has an outside diameter of about 45 mm.