Method of assembly of a combustion cup, filter, and diffuser cup for a vehicle occupant restraint inflator

An inflator for inflating a vehicle occupant restraint includes an annular slag screen or filter which is disposed between a combustion cup and a diffuser cup. A canister of gas generating material is disposed in the combustion cup. Upon igniting the gas generating material in the canister, gas flows through openings in the side wall of the combustion cup to the slag screen or filter. The gas then flows through a final filter assembly and out of the diffuser cup. The slag filter is preassembled on the combustion cup by radially contracting a surface of the filter to grip the side wall of the combustion cup. This enables the combustion cup and slag filter to be positioned as a unit relative to the diffuser cup and final filter.

BACKGROUND OF THE INVENTION 
The present invention relates to a new and improved apparatus and method 
for inflating a vehicle occupant restraint. Specifically, the invention 
relates to an air bag inflator having a filter through which gas passes 
before entering the air bag. 
A known inflator housing which holds materials for generating gas to 
inflate an air bag is disclosed in U.S. Pat. No. 4,902,036. Upon ignition 
of the gas generating material in the inflator housing, gas flows through 
a slag screen or filter. The gas then flows through a final filter 
assembly. After passing through the final filter assembly, the gas enters 
the air bag to inflate the air bag. 
Although this known inflator is generally satisfactory, the inflator could 
be improved by increasing the ease with which the inflator is assembled. 
SUMMARY OF THE INVENTION 
The present invention relates to an improved inflator which inflates a 
vehicle occupant restraint, such as an air bag. The inflator includes a 
housing having a combustion cup with a chamber in which gas generating 
material is located. Gas flows from the combustion cup through a slag 
screen or filter upon ignition of the gas generating material. The gas 
then flows through a final filter and is conducted through openings in a 
diffuser cup to the air bag. 
In accordance with a feature of the present invention, the slag screen or 
filter and the combustion cup are preassembled to facilitate positioning 
of the slag filter and combustion cup, as a unit, relative to the diffuser 
cup and final filter assembly. To preassemble the combustion cup and slag 
filter, a surface of the annular slag filter is radially contracted to 
grip the combustion cup. Thereafter, the combustion cup and slag filter 
are positioned as a unit in the diffuser cup with the slag filter between 
the combustion cup and diffuser cup.

DESCRIPTION OF ONE EMBODIMENT OF THE INVENTION 
General Description 
The present invention relates to an air bag inflator and particularly to an 
inflator for inflating an air bag to protect the driver of a vehicle. The 
present invention is applicable to various inflator constructions. As 
representative of the present invention, FIG. 1 illustrates an inflator 
10. An air bag 12 is folded around the inflator 10. A cover 14 encloses 
the air bag 12 and the inflator 10. The inflator 10, the air bag 12, and 
the cover 14 are components of a module which is mounted on a vehicle 
steering wheel 16. 
Upon the occurrence of sudden vehicle deceleration, such as occurs in a 
collision, the inflator 10 is energized and produces a large volume of 
gas. The gas from the inflator 10 expands the air bag 12. As the air bag 
12 starts to expand, it breaks weakened portions in the cover 14. One of 
the weakened portions is designated 18 in FIG. 1. As the air bag 12 
continues to expand, it moves into the space between the driver of the 
vehicle and the steering wheel 16 to restrain movement of the driver, as 
is known. 
The inflator 10 (FIG. 2) includes a housing 40. The housing 40 is made of 
three pieces, namely, a one-piece diffuser cup 42, a one-piece combustion 
cup 44, and a one-piece combustion chamber cover 46. The diffuser cup 42, 
the combustion cup 44, and the combustion chamber cover 46 are each made 
from one piece of sheet metal, such as UNS S30100 stainless steel. 
The diffuser cup 42 is generally cup-shaped, is a single piece of sheet 
metal, and has a cylindrical side wall 50 extending around the central 
axis 52 of the inflator 10. The side wall 50 extends between a flat upper 
annular end wall 54 and a flat lower annular flange 56. The annular flange 
56 extends radially outwardly from an end of the diffuser cup opposite 
from the end wall 54 and is coaxial with the side wall 50. A circular 
inner annular surface 55 on the upper end wall 54 of the diffuser cup 42 
defines a central circular opening 57 in the upper end wall 54 which 
minimizes the weight of the diffuser cup. The end wall 54 and the flange 
56 are parallel to each other and perpendicular to the axis 52. An annular 
array of gas outlet openings 58 extends circumferentially around an upper 
portion of the diffuser cup side wall 50. 
The combustion cup 44 (FIGS. 2 and 3) is generally cup-shaped, is a single 
piece of sheet metal, and is disposed inside the diffuser cup 42. The 
combustion cup 44 has a cylindrical side wall 60 extending around the axis 
52. The cylindrical side wall 60 extends between a flat imperforate 
circular upper end wall 64 and a flat lower annular flange 66. The flange 
66 is disposed in a coaxial relationship with the cylindrical side wall 60 
and extends radially outwardly from an end of the side wall 60 opposite 
from the end wall 64. The upper end wall 64 and the lower flange 66 are 
parallel to each other and perpendicular to the axis 52. An annular array 
of openings 68 extends circumferentially around a lower portion of the 
combustion cup side wall 60. 
The upper end wall 64 of the combustion cup 44 is welded, with a circular 
continuous weld, to the annular surface 55 on the upper end wall 54 of the 
diffuser cup 42 at a weld location 70, preferably by laser welding. The 
combustion cup flange 66 is welded with a circular continuous weld to the 
diffuser cup flange 56 at a weld location 72, also preferably by laser 
welding. 
The cover 46 is also formed from a single piece of sheet metal. The 
combustion chamber cover 46 is a generally flat circular metal piece 
having a circular center portion 80 and a parallel but slightly offset 
annular outer flange 82. A circular opening 84 is located in the center 
portion 80 of the chamber cover 46. The opening 84 is coaxial with the 
diffuser and combustion cup side walls 50 and 60. The outer flange 82 of 
the chamber cover 46 overlaps the combustion cup flange 66 and is welded 
with a circular continuous weld to the combustion cup flange 66 at a 
circumferential weld location 86, again preferably by laser welding. The 
circular weld locations 70, 72 and 86 are coaxial with the central axis 52 
of the inflator. The welds may be formed by a Rofin-Sinar 850 CO.sub.2 
Laser. 
A hermetically sealed canister 90 (FIG. 2) is disposed in the combustion 
cup 44. The canister 90 is made of two pieces, namely, a lower canister 
section 92 and a cover 94. The radially outer edge of the canister cover 
94 is crimped to an adjacent edge of the canister lower section 92 to seal 
the canister 90 hermetically. The canister 90 is preferably made of 
relatively thin aluminum. 
The canister lower section 92 (FIG. 2) has a cylindrical outer side wall 96 
adjacent to and inside the combustion cup side wall 60. The side wall 96 
has a reduced thickness in the area adjacent the openings 68 in the 
combustion cup side wall 60. The canister lower section 92 also has a 
cylindrical inner side wall 98 spaced radially inwardly from the outer 
side wall 96. The side wall 98 has a reduced thickness in the area 
adjacent an igniter 142. 
A flat ring-shaped lower wall 100 of the canister lower section 92 
interconnects the outer side wall 96 and the inner side wall 98. A 
circular inner top wall 102 of the canister lower section 92 extends 
radially inwardly from and caps the inner side wall 98. The inner top wall 
102 and the cylindrical inner side wall 98 define a downwardly opening 
central recess 104 in the canister 90. 
The canister cover 94 is generally circular in shape. A recess 106 is 
located in the center of the canister cover 94. A packet 108 of auto 
ignition material is located in the recess 106 and held in the recess 106 
by a piece of aluminum foil tape 109. 
A plurality of annular disks 110 of gas generating material are stacked 
atop each other within the canister 90. An annular cushion 112 is disposed 
between the uppermost gas generating disk 114 and the inside of the 
canister cover 94. The disks 110 are made of a known material which, when 
ignited, generates nitrogen gas. Although many types of gas generating 
material could be used, suitable gas generating materials are disclosed in 
U.S. Pat. No. 3,895,098. 
An annular prefilter 120 is disposed in the canister 90. The prefilter 120 
is located radially outward of the gas generating disks 110 and radially 
inward of the outer side wall 96 of the canister 90. A small annular space 
exists between the prefilter 120 and the outer side wall 96. 
An annular slag screen or filter indicated schematically at 122 is located 
in the diffuser cup 42, outside of the combustion cup 44. The slag filter 
122 is disposed radially outward of the openings 68 and lies against the 
combustion cup side wall 60. However, the slag filter 122 could be spaced 
away from the openings 68 in the combustion cup side wall 60. 
An annular final filter assembly indicated schematically at 124 is located 
inside the diffuser cup 42 above the slag screen or filter 122. The final 
filter assembly 124 is radially inward of the gas outlet openings 58 in 
the side wall 50 of the diffuser cup 42. The final filter assembly 124 is 
a plurality of layers of various materials. The layers extend around the 
diffuser cup side wall 50 and are located inside the side wall. The 
detailed structure of the final filter assembly 124 does not form a part 
of the present invention and therefore will not be described in detail. 
An annular filter shield 126 projects radially inwardly from the diffuser 
cup side wall 50 and separates the final filter assembly 124 and the slag 
screen 122. An annular graphite seal 128 seals the gap between the upper 
edge of the final filter assembly 124 and the inside of the diffuser cup 
upper end wall 54. Another annular graphite seal 130 seals the gap between 
the lower edge of the final filter assembly 124 and the upper side of the 
filter shield 126. 
The inflator 10 includes an initiator assembly 140. The initiator assembly 
140 projects through the opening 84 in the chamber cover 46 into the 
central recess 104 of the canister 90. The initiator assembly 140 is 
welded with a continuous weld, preferably a laser weld, to the center 
portion 80 of the chamber cover 46 at a circumferential weld location 144. 
The initiator assembly 140 includes the igniter 142. The igniter 142 
includes a pair of wire leads 146 which extend outwardly from the 
initiator assembly 140. The wire leads 146 are connectable to a collision 
sensor (not shown). Within the igniter 142, the wire leads 146 are 
connected to a resistance wire embedded in an ignition material. The 
igniter 142 may be of any suitable well known construction. A thin plastic 
film (not shown) is located on the outside of the upper portion of the 
igniter 142, to prevent metal-to-metal contact which could ground the 
igniter 142 and disable the inflator 10. 
Upon the occurrence of a collision or other sudden vehicle deceleration, 
the collision sensor closes an electrical circuit. An electrical current 
then flows through the wire leads 146 to the igniter 142. The resistance 
wire sets off the ignition material which ignites a charge in the igniter 
142. Ignition of the charge forms hot gas products which flow outwardly 
from the igniter 142 and rupture the inner top wall 102 and the inner side 
wall 98 of the canister 90. The hot gas from the igniter 142 ignites the 
disks 110 of gas generating material. The disks 110 of gas generating 
material rapidly produce a large volume of another hot gas. 
The pressure of the gas acts on the cylindrical side wall 96 of the 
canister 90, forcing the side wall 96 radially outwardly against the 
combustion cup side wall 60. This results in the thin side wall 96 of the 
canister 90 being ruptured or blown out at the openings 68 in the 
combustion cup side wall 60. The reduced thickness of the side wall 96 
adjacent the openings 68 allows this portion of the side wall 96 to 
rupture in preference to other portions at a desired pressure. The gas 
generated by burning of the disks 110 then flows radially outwardly 
through the prefilter 120. The prefilter 120 removes from the flowing gas 
some combustion products of the initiator assembly 140 and of the gas 
generating disks 110. The prefilter 120 also cools the gas, and molten 
combustion products plate on the prefilter. The gas flows through the 
openings 68 and into the slag screen or filter 122. 
The slag screen or filter 122 removes and traps particles from the flowing 
gas. The slag filter 122 also cools the flowing gas. When the gas cools, 
molten combustion products such as metal are plated onto the slag filter 
122. The filter shield 126 between the slag filter 122 and the final 
filter assembly 124 causes turbulent flow of gas to occur in and around 
the slag filter. The turbulent gas flow promotes the retention of 
relatively heavy particles in the slag filter 122 and in the lower portion 
of the diffuser cup 42. 
The gas flows axially upwardly from the slag filter 122 to the final filter 
assembly 124. The gas then flows radially outwardly through the final 
filter assembly 124 which removes small particles from the gas. The final 
filter assembly 124 also further cools the gas so that molten products in 
the gas may deposit on parts of the final filter assembly 124. The annular 
array of gas outlet openings 58 directs the flow of gas into the air bag 
12 to inflate the air bag 12. 
In accordance with one of the features of the present invention, the slag 
filter 122 is preassembled on the combustion cup 44. The preassembled 
combustion cup 44 and slag filter 122 are then positioned as a unit in the 
diffuser cup 42. By preassembling the combustion cup 44 and slag filter 
122, assembly of the inflator 10 is facilitated. 
To preassemble the slag filter 122 on the combustion cup 44, the combustion 
cup is positioned in a cylindrical die cavity 172 defined in part by a 
circular die ring 170 (FIG. 3). The cylindrical side wall 60 of the 
combustion cup 44 is positioned in the cylindrical die cavity 172 with a 
central axis of the combustion cup coincident with a central axis of the 
die cavity and the die ring 170. The annular combustion cup flange 66 is 
disposed in abutting engagement with an annular radially extending lower 
surface 174 of the die ring 170. The combustion cup 44 is supported and 
held in place by a backing plate or member 176, which underlies both the 
combustion cup and the die ring 170. 
The annular slag filter 122 is positioned in the die cavity 172 around the 
cylindrical outer side wall 60 of the combustion cup 44. A cylindrical 
radially outer side surface 180 of the slag filter 122 loosely engages a 
cylindrical radially inner side surface 184 of the die ring 170. A 
cylindrical radially inner side surface 188 of the slag filter 122 is 
coaxial with and spaced radially from side wall 60 of the combustion cup 
44. Since the inside diameter of the annular slag filter 122 is greater 
than the outside diameter of the combustion cup side wall 60, the slag 
filter can be readily positioned around the side wall with the radially 
extending lower end of the filter supported by the combustion cup flange 
66 (FIG. 3). 
Once the slag filter 122 has been positioned in the die cavity 172, a 
hollow cylindrical upper die 192 is lowered. As the die 192 is lowered 
from a raised position above the combustion cup 44 to the position shown 
in FIG. 3, the upper end portion of the combustion cup 44 enters a 
cylindrical cavity 194 in the upper die 192. Continued downward movement 
of the upper die 192 moves the upper die into the cylindrical cavity 172 
in the die ring 170. The upper die 192 is then in a relatively close 
fitting relationship with both the radially outer surface of the 
combustion cup side wall 60 and the radially inner surface 184 of the die 
ring 170. Continuing its downward movement, the upper die 192 moves its 
annular radially extending lower surface 196 into abutting engagement with 
an annular radially extending upper surface 198 of the slag filter 122. 
Further downward movement of the upper die 192 compresses the slag filter 
122 vertically between the combustion cup flange 66 and the upper die. As 
the slag filter 122 is compressed vertically, the material of the filter 
is forced radially inwardly to fill the space between the filter and the 
combustion cup side wall 60. In effect, the radially inner side surface 
188 of the slag filter contracts radially inwardly (FIG. 4) and firmly 
grips the side wall 60 of the combustion cup 44. Although the pressure 
applied by the upper die 192 against the slag filter 122 is sufficient to 
cause the inner side surface 188 of the slag filter to contract radially 
inwardly to grip the combustion cup side wall 60 securely, the pressure is 
not so great as to compact the material of the slag filter excessively and 
to increase its resistance to fluid flow undesirably. 
The slag filter 122 is preferably a knitted stainless steel structure 
having long cylindrical wires with smooth longitudinal surfaces and no 
sharp end points. The material of this specific slag filter 122 is UNS 
S30400 stainless steel per the ASTM-A-580 standard and can be obtained 
from Metex Corporation of New Jersey. The Density Range of the material is 
from 10 to 30 percent by volume. This specific stainless steel filter has 
a 15 percent density by volume. The slag filter 122 could, however, be 
formed of other materials and/or have a different density, if desired. 
Once the inner side surface 188 of the slag filter 122 has been radially 
contracted to grip the combustion cup side wall 60, the die 192 is raised 
and the support plate 176 is lowered to enable the preassembled combustion 
cup 44 and slag filter 122 to be removed as a unit from the die cavity 
172. At this time, the frictional grip of the slag filter 122 on the 
combustion cup 44 is sufficient to hold the slag filter in abutting 
engagement with the combustion cup flange 66. When preassembled with the 
combustion cup, the slag filter 122 overlies the combustion cup side wall 
openings 68. 
Once the combustion cup 44 and slag filter 122 have been preassembled, the 
combustion cup and filter are ready to be assembled as a unit with other 
components of the inflator 10. However, before the combustion cup 44 and 
slag filter 122 are assembled with the other components of the inflator 
10, the annular final filter assembly 124 (FIG. 5) is positioned in a 
cylindrical chamber 204 in the diffuser cup 42. The diffuser cup 42 is 
oriented upside down, as shown in FIG. 5, and the graphite seal 128 is 
placed against the diffuser cup end wall 54. The final filter assembly 124 
is then positioned in abutting engagement with the graphite seal 128. 
Although it is preferred to assemble the components of the inflator 10 in 
the upside down orientation illustrated in FIG. 5, they could be assembled 
in a different orientation if desired. 
Once the final filter assembly 124 has been positioned in the diffuser cup 
42, the graphite seal 130 (FIG. 2) is placed on top of the filter 
assembly. The annular filter shield 126 is then positioned in the diffuser 
cup. An interference fit is provided between the outer side surface of the 
filter shield 126 and the cylindrical radially inner side surface of the 
diffuser cup side wall 50. This interference fit holds the filter shield 
126 in place against the graphite seal 130 and adjacent an end of the 
final filter assembly 124 which is opposite the diffuser cup side wall 54. 
Once the filter shield 126 has been inserted into the diffuser cup 42, the 
combustion cup 44 and slag filter 122 are positioned in the diffuser cup 
42 as a unit. Specifically, the leading or lower (as viewed in FIG. 5) end 
portion of the combustion cup 44 is telescopically inserted into the 
diffuser cup 42. The annular final filter assembly 124 and filter shield 
126 will thus encircle the combustion cup 44. The combustion cup end wall 
64 (FIG. 2) also moves into flat abutting engagement with an annular 
radially extending inner surface of the diffuser cup end wall 54. 
As the end wall 64 of the combustion cup 44 engages the diffuser cup end 
wall 54, the annular radially extending flange 66 on the combustion cup 44 
moves into flat abutting engagement with the annular radially extending 
diffuser cup flange 56. In addition, the slag filter 122 moves into 
abutting engagement with the filter shield 126. Although it is preferred 
to position the combustion cup 44 and slag filter 122 relative to the 
diffuser cup 42 and final filter assembly 124 by moving the cup could be 
moved relative to the combustion cup, if desired. 
When the slag filter 122 has been positioned in abutting engagement with 
the filter shield 126 (FIG. 2), there is an annular space between a 
radially inner side surface of the final filter assembly 124 and a 
radially outer side surface of the cylindrical combustion cup side wall 
60. This space forms a passage through which gas flows from the slag 
filter 122 upwardly (as viewed in FIG. 2) along the combustion cup side 
wall 60 to the final filter assembly 124. The gas then flows radially 
outwardly through the annular final filter assembly 124 and openings 58 to 
the air bag which is to be inflated by the gas. 
Once the combustion cup 44 and slag filter 122 have been positioned as a 
unit in the diffuser cup 42, the diffuser cup and combustion cup end walls 
54 and 64 (FIG. 2) are interconnected by the continuous circular weld at 
weld location 70. Also, the combustion cup flange 66 is welded to the 
diffuser cup flange 56. Thus, a continuous circular weld 72 connects the 
periphery of the combustion cup flange 66 with a downwardly facing (as 
viewed in FIG. 2) surface of the diffuser cup flange 56. 
The canister 90 is then inserted into the cylindrical chamber 208 (FIG. 2) 
defined by the combustion cup 44. As the canister 90 is inserted into the 
combustion cup chamber 208, the end wall 94 of the canister engages the 
combustion cup end wall 64. The initiator assembly 140 is connected with 
the cover 46 by the continuous circular weld 144 while the cover is spaced 
from the combustion cup 44 and diffuser cup 42. Once the initiator 
assembly 140 has been connected with the cover 46, the initiator assembly 
140 is telescopically inserted into the cylindrical recess 104 at the 
center of the canister 90. The canister 90 is pressed by the cover 46 
against the combustion cup end wall 64. The canister end wall 94 is 
deflected axially inwardly and compresses the cushion 112 against the 
upper disk 114 of gas generating material. At the same time, the cover 
flange 82 moves into flat abutting engagement with the combustion cup 
flange 66. 
The cover flange 82 is then welded to the combustion cup flange 66 with the 
continuous circular weld 86. It should be noted that the continuous 
circular weld 86 is the only weld which is made to the inflator housing 40 
after the canister 90 of gas generating material has been positioned in 
the combustion cup 44. 
From the above description of the invention, those skilled in the art will 
perceive improvements, changes and modifications in the invention. Such 
improvements, changes and modifications within the skill of the art are 
intended to be covered by the appended claims.