Tortuous path filter for airbag inflator

A unitary filter module for insertion into an inflator for an airbag assembly, the inflator having a housing with a central longitudinal axis, at least one diffuser hole, and a gas source contained within a chamber defined within the housing, wherein, in response to receipt by the inflator of a first activation signal, the gas source provides a gas, the unitary filter module having a flat mode and an inserted spiral rolled mode and comprising:

• a unitary body having a length, a width, an inner layer portion, an intermediate layer portion, and an outer layer portion, in the flat mode:
• the inner layer portion comprises a first array of holes arranged in a first grid such that each hole in the first array of holes aligns longitudinally with at least one other of the holes of the first array of holes and also aligns laterally with at least one differing hole of the first array of holes;
• the intermediate layer portion comprises a second array of holes arranged in a second grid such that each hole in the second array of holes aligns longitudinally with at least one other of the holes of the second array of holes and also aligns laterally with at least one differing hole of the second array of holes, the holes aligned longitudinally in the first array of holes do not align longitudinally with the holes aligned longitudinally in the second array of holes;
• and
• the outer layer portion comprises a third array of holes arranged in a third grid such that each hole in the third array of holes aligns longitudinally with at least one other of the holes of the third array of holes and also aligns laterally with at least one differing hole of the third array of holes, the holes aligned longitudinally in the third array of holes do not align longitudinally with the holes aligned longitudinally in the second array of holes;
• the unitary body in the inserted spiral rolled mode is rolled around the central longitudinal axis into a spiral and disposed within the housing such that the inner layer portion defines an inner layer, the intermediate layer portion defines an intermediate layer, and the outer layer portion defines an outer layer, wherein:
• the first array of holes of the inner layer surround the central longitudinal axis such that the longitudinally aligned holes of the first array of holes define a first set of planes each substantially perpendicular to the central longitudinal axis and the laterally aligned holes of the first array of holes define a first set of axes substantially parallel to the central longitudinal axis, and wherein the inner layer is positioned such that the gas passes through the first array of holes to reach the intermediate layer;
• the second array of holes of the intermediate layer surround inner layer and the central longitudinal axis such that the longitudinally aligned holes of the second array of holes define a second set of planes each substantially perpendicular to the central longitudinal axis and each offset from the first set of planes, and the laterally aligned holes of the second array of holes define a second set of axes substantially parallel to the central longitudinal axis, and wherein the intermediate layer is positioned such that the gas passes through the second array of holes to reach the outer layer;
• and
• the third array of holes of the outer layer surround inner layer, the intermediate layer, and the central longitudinal axis such that the longitudinally aligned holes of the third array of holes define a third set of planes each substantially perpendicular to the central longitudinal axis and each offset from the second set of planes, and the laterally aligned holes of the third array of holes define a third set of axes substantially parallel to the central longitudinal axis, and wherein the outer layer is positioned such that the gas passes through the third array of holes to reach the and at least one diffuser hole;
• the intermediate layer comprises a second array of holes, each hole of the second array of holes is not aligned with the hole of the first array of holes nearest such hole of the second array of holes, wherein the intermediate layer is positioned such that the gas passes through the second array of holes to reach the outer layer;
• the outer layer comprises a third array of holes, each hole of the third array of holes is not aligned with the hole of the second array of holes nearest such hole of the third array of holes, wherein the outer layer is positioned such that the gas passes through the third array of holes to reach the at least one diffuser hole of the housing;
• and
• a plurality of protrusions disposed such that at least one protrusion is disposed on the inner layer portion, at least one protrusion is disposed on the intermediate layer portion, and at least one protrusion is disposed on the outer layer portion, each protrusion disposed on the inner layer portion is adjacent at least one of the holes of the first array of holes of the inner layer, each protrusion disposed on the intermediate layer portion is adjacent at least one of the holes of the second array of holes of the intermediate layer, each protrusion disposed on the outer layer portion is adjacent at least one of the holes of the third array of holes of the outer layer, such protrusions maintain a gap between the inner layer and the intermediate layer, between the intermediate layer and the outer layer, and between the outer layer and the exterior wall to define a spiraling plenum through which the gas passes on a tortuous path from the gas source through the filter module to exit the inflator through the at least one diffuser hole;
• and
• wherein the unitary body of the filter module is wider at the outer layer portion than at the inner layer portion and intermediate layer portion, and the inflator has a frangible burst disk between the gas source and the filter module thereby enabling the burst disk to open over the full diameter of the outer layer.

A unitary filter module for insertion into an inflator for an airbag assembly, the inflator having a housing with a central longitudinal axis, at least one diffuser hole, and a gas source contained within a chamber defined within the housing, wherein, in response to receipt by the inflator of a first activation signal, the gas source provides a gas, the unitary filter module having a flat mode and an inserted spiral rolled mode and comprising:

• a unitary body having a length, a width, an inner layer portion, an intermediate layer portion, and an outer layer portion, in the flat mode:
• the inner layer portion comprises a first array of holes;
• the intermediate layer portion comprises a second array of holes;
• the outer layer portion comprises a third array of holes;
• a plurality of protrusions, at least one protrusion of the plurality of protrusions being disposed adjacent at least one of the holes of the first array of holes of the inner layer portion, at least one protrusion of the plurality of protrusions being disposed adjacent at least one of the holes of the second array of holes of the intermediate layer portion, at least one protrusion of the plurality of protrusions being disposed adjacent at least one of the holes of the third array of holes of the outer layer portion;
• and
• wherein at least one of the first array of holes, the second array of holes, and the third array of holes has a staggered array pattern wherein the staggered array pattern comprises multiple lines of longitudinally aligned holes and each hole of any of the multiple lines of longitudinally aligned holes aligns laterally with at least one hole of another of the multiple lines of longitudinally aligned holes but does not align laterally with any of the holes of at least one other of the multiple lines of longitudinally aligned holes;
• the unitary body in the inserted spiral rolled mode is rolled around the central longitudinal axis into a spiral and disposed within the housing such that the inner layer portion defines an inner layer, the intermediate layer portion defines an intermediate layer, and the outer layer portion defines an outer layer, wherein:
• the inner layer is positioned such that the gas passes through the first array of holes to reach the intermediate layer;
• the intermediate layer is positioned such that the gas passes through the second array of holes to reach the outer layer;
• the outer layer is positioned such that the gas passes through the third array of holes to reach the and at least one diffuser hole;
• and
• each protrusion of the inner layer protrudes toward the intermediate layer, each protrusion of the intermediate layer protrudes toward the outer layer, each protrusion of the outer layer protrudes toward the exterior wall, such protrusions maintain a gap between the inner layer and the intermediate layer, between the intermediate layer and the outer layer, and between the outer layer and the exterior wall to define a spiraling plenum through which the gas passes on a tortuous path from the gas source through the filter module to exit the inflator through the at least one diffuser hole;
• and
• wherein the unitary body of the filter module is wider at the outer layer portion than at the inner layer portion and intermediate layer portion, and the inflator has a frangible burst disk between the gas source and the filter module thereby enabling the burst disk to open over the full diameter of the outer layer.