Air bag inflator

• US 5,816,612 A
• Filed: 02/26/1993
• Issued: 10/06/1998
• Est. Priority Date: 06/21/1991
• Status: Expired due to Fees

• Current Assignee: TRW Vehicle Safety Systems Incorporated (Zeppelin - Stiftung der Stadt Friedrichshafen)
• Original Assignee: TRW Vehicle Safety Systems Incorporated (Zeppelin - Stiftung der Stadt Friedrichshafen)
• Inventors: Thompson, Richard J., Faigle, Ernst M., Semchena, John H.
• Primary Examiner(s): Culbreth, Eric D.
• Application Number:
  US08/024,851
• Time in Patent Office: 2,048 Days
• Field of Search: 280/736, 280/738, 280/740, 280/741, 280/742, 222/3, 55/323, 55/330, 55/307, 55/308, 55/DIG. 45, 55/529, 55/498, 55/486, 210/483, 210/484, 210/489, 422/164
• US Class Current: 280/740
• CPC Class Codes: B60R 21/2644 using only solid reacting substances, e.g. pellets, powder
• CPC Class Codes: B60R 21/30 with means to draw ambient air into the flow line and mix such air with the inflation fluid

Abstract

An inflator for generating gas to inflate an air bag in a vehicle occupant safety apparatus comprises gas generating material, a plurality of filter layers, and a strand extending around the filter layers. The gas generating material generates gas when ignited. The filter layers filter the gas as it flows through the filter layers, and encircle the gas generating material. The filter layers include an outer layer with a cylindrical outer surface. The strand extends around the cylindrical outer surface of the outer filter layer at least partially in a helix, and has a plurality of circumferentially extending turns. The turns in the strand are spaced apart axially to define a helical gap which permits the gas to move from the cylindrical outer surface past the strand toward the air bag.

Claims

1. An inflator for generating gas to inflate an air bag in a vehicle occupant safety apparatus, said inflator comprising:

gas generating material which generates gas when ignited;

filter means for filtering the gas, said filter means including a filter structure having a generally cylindrical outer surface with first and second axial ends, said filter structure comprising a plurality of overlying porous flexible filter layers surrounding said gas generating material, one of said filter layers being the outermost porous flexible filter layer in said inflator;

wrapping means for pressing said filter layers together in overlying relationship, said wrapping means comprising a strand wrapped around said cylindrical outer surface of said filter structure and extending from said first axial end to said second axial ends said strand being wrapped in tension so as to apply a radially directed compressive force to said filter layers; and

a first end cap adjacent to said first axial end of said cylindrical outer surface and a second end cap adjacent to said second axial end of said cylindrical outer surface, said strand having first and second axial end portions, each of said axial end portions being wrapped circumferentially entirely around a respective one of said end caps.

2. Apparatus as defined in claim 1 wherein said strand is a metal wire having a circular cross-section.

3. A cylindrical inflator for inflating a vehicle occupant restraint, said inflator comprising:

an ignitable gas generating material which, when ignited, generates gas for inflating the vehicle occupant restraint;

means for defining a pair of circular side walls, each of said side walls having a radially outer periphery;

a cylindrical tube extending axially between said side walls and being entirely spaced radially inward from said peripheries of said side walls, said tube having a cylindrical inner surface extending axially between said side walls and circumferentially around said gas generating material, said tube further having means for defining a plurality of gas flow openings for directing said gas to flow from said gas generating material in a direction radially outward through said tube and to flow between said side walls in a direction radially outward from said tube toward said peripheries of said side walls, said tube being the radially inner-most part of said inflator having gas flow openings for directing said gas to flow radially outward from said gas generating material;

a tubular filter having an outer surface with a generally cylindrical shape, said filter extending over said tube between said side walls and being circumferentially and axially continuous over said tube between said side walls, said filter including means for filtering said gas as said gas flows between said side walls in said direction radially outward from said tube toward said peripheries of said side walls; and

holding means for holding said outer surface of said filter in said generally cylindrical shape between said side walls, said holding means including a strand having helical turns extending circumferentially entirely around said filter, a plurality of said helical turns being spaced from each other to define a gas flow space in a helical shape between said plurality of helical turns;

said helically shaped gas flow space having a width extending axially between adjacent ones of said plurality of helical turns and having a length extending circumferentially entirely around said filter a plurality of times, said helically shaped gas flow space being continuously open and free of obstructions between said plurality of helical turns throughout said width and length of said helically shaped gas flow space;

said strand being wrapped in tension around said filter so as to apply a radially directed compressive force through said filter from said outer surface of said filter to said tube, said force pressing said filter radially against said tube and holding said outer surface of said filter in said generally cylindrical shape between said side walls.

4. A cylindrical inflator for inflating a vehicle occupant restraint, said inflator comprising:

an ignitable gas generating material which, when ignited, generates gas for inflating the vehicle occupant restraint;

tubular means for containing said gas generating material, said tubular means defining a plurality of gas flow openings for directing said gas to flow radially outward from said as generating material into said tubular means, said gas flow openings being the radially inner-most gas flow openings in said inflator that are located radially outward of said gas generating material;

said tubular means comprising filter means for filtering said gas as said gas flows radially outward from said gas generating material, said filter means having an outer surface with a generally cylindrical shape, said filter means being circumferentially and axially continuous over said gas generating material and being radially continuous from said gas flow openings to said outer surface; and

holding means for holding said outer surface of said filter means in said generally cylindrical shape, said holding means including a strand having helical turns extending circumferentially entirely around said filter means, a plurality of said helical turns being spaced from each other to define a gas flow space in a helical shape between said plurality of helical turns;

said helically shaped gas flow space having a width extending axially between adjacent ones of said plurality of helical turns and having a length extending circumferentially entirely around said filter a plurality of times, said helically shaped gas flow space being continuously open and free of obstructions between said plurality of helical turns throughout said width and length of said helically shaped gas flow space;

said strand being wrapped in tension around said filter means so as to apply a compressive force radially inward through said entire filter means, said compressive force holding said outer surface of said filter means in said generally cylindrical shape.