Gas generator

A gas generating device is constructed of a gas generator, a hammer pin trigger device and a gas guide slot. The gas generator has a detonator. The hammer pin trigger device has a hammer pin arranged movably toward the detonator so that the hammer pin is caused to strike and fire the detonator. The gas guide slot is formed at a joint portion between the gas generator and the hammer pin trigger device for guiding gas, which occurs upon firing the detonator, in a specific direction to an outside of the gas generating device.

BACKGROUND OF THE INVENTION 
a) Field of the Invention 
This invention relates to a gas generating device for actuating an 
apparatus such as an air bag system or a webbing pretensioner of a seat 
belt system, for example, in the event of a collision of an automotive 
vehicle. More specifically, this invention is concerned with a gas 
generating device equipped with a hammer pin trigger device which causes a 
hammer pin to strike a detonator of a gas generator. 
b) Description of the Related Art 
An air bag system and/or a webbing pretensioner has been used to protect an 
occupant in the event of a collision of an automotive vehicle. It is 
necessary to make these devices actuate instantaneously at the time of a 
collision, so that a gas generating device is employed to cause explosive 
combustion of a gas-generating chemical reagent such as explosive for the 
generation of high-temperature gas. 
These gas generating devices are available in types, one being electrically 
fired and the other mechanically fired. Mechanical devices are however 
finding increasing popularity in recent years for their simpler 
construction and lower price. 
Referring first to FIGS. 8 through 10, a description will hereinafter be 
made of a conventional mechanically-triggered gas generating device as 
applied to a pretensioner of a webbing retractor in an automotive seat 
belt system. 
FIG. 8 is a front view of the webbing retractor equipped with the 
pretensioner, FIG. 9 is a partly cross-sectional view of the 
mechanically-triggered gas generating device, and FIG. 10 is a side view 
of the webbing retractor and shows directions of gas blown out of the 
mechanically-triggered gas generating device. 
The webbing retractor will first be described. As is illustrated in FIGS. 8 
and 10, the webbing retractor 1 comprises a frame 2 made of a steel plate, 
having an inverted square-U-shaped configuration in cross-section and 
mutually-opposing side walls 2a,2b, a take-up reel 3 rotatably supported 
at opposite ends thereof on the side walls 2a,2b and adapted to wind in or 
take up a webbing 4, a winder unit 6 for normally biasing the take-up reel 
3 in a webbing-winding direction, and an emergency lock mechanism 5 for 
locking rotation of the take-up reel 3 to prevent any further release of 
the webbing 4 upon occurrence of an abrupt deceleration on an automotive 
vehicle on which the webbing retractor 1 is mounted. 
The webbing retractor 1 is mounted on a vehicle body by a tongue-shaped 
mounting member 7 disposed on a lower side of the frame 2 as viewed in the 
drawings. The webbing 4, which is made of polyester fibers, can be wound 
out or released in an upward direction as viewed in the figures while 
being guided by a webbing guide 8. Attached as an integral unitary member 
to an upper end portion of the side wall 2a of the frame 2 by way of a 
horizontal connecting portion is a plate-shaped mounting bracket 2c for 
the gas generating device. This mounting bracket 2c extends in parallel 
with the side wall 2a. On opposite sides of the mounting bracket 2c, a 
hammer pin trigger device 20 and a pretensioner 10 are mounted, 
respectively, so that the hammer pin trigger device 20 and the 
pretensioner 10 are arranged opposite each other. The hammer pin trigger 
device 20 and the pretensioner 10 are threadedly secured on the mounting 
bracket 2c by bolts 26, whereby the bracket 2c is located between the 
hammer pin trigger device 20 and the pretensioner 10. 
As is illustrated in FIGS. 9 and 10, the hammer pin trigger device 20 has a 
housing 21 mounted on one side wall 2e of the mounting bracket 2c. This 
housing 21 has a bottom-closed cylindrical configuration. On an 
open-end-side outer peripheral wall of the housing 21, mounting flanges 
21a,21b are disposed so that they extend perpendicularly to an axis of the 
housing 21. A hammer pin guide member 25, which will be described 
subsequently herein, is fitted in the open end of the housing 21, so that 
the housing 21 is closed. 
In the housing 21, a rod-shaped hammer pin 24 is arranged slidably in the 
direction of the axis. A tip portion of the hammer pin 24 is pointed and 
is inserted in an aperture 25d of the hammer pin guide member 25. The 
hammer pin 24 is therefore axially displaceable within the housing 21. 
The pretensioner 10 has a cylindrical housing 11 mounted on an opposite 
side wall 2f of the bracket 2c and a cylinder 12 threadedly fitted in a 
free end portion of the housing 11. The pretensioner 10 therefore has an 
L-shaped configuration as viewed in front elevation. 
Accommodated in the housing 11 is a gas generator 30 which is disposed in 
contact with the side wall 2f of the mounting bracket 2c. 
This gas generator 30 comprises, as depicted in FIG. 9, a gas-generating 
chemical reagent 32 enclosed within a bottom-closed cylindrical casing, a 
detonator holder 34 sealing the gas-generating chemical reagent 32 and 
holding a detonator 33 on an axis, and a cap 35 defining a hammer pin 
guide aperture 35a for guiding the tip portion of the hammer pin 24. The 
detonator 33 is in the form of a detonator which is fired when struck by 
the pointed tip portion of the hammer pin 24, and is disposed opposite the 
hammer pin guide aperture 35a. The detonator holder 35 also defines a 
through-hole 34a so that when the detonator 33 is fired by the hammer pin 
24, resulting flame is allowed to blow out into the gas-generating 
chemical reagent 32 to ignite the gas-generating chemical reagent 32. 
Operations of the above-described hammer pin trigger device 20 and the gas 
generator 30 will next be described. 
When an abrupt inertia of at least a predetermined value acts on an 
unillustrated inertia body arranged in the hammer pin trigger device 20 as 
a result of a collision or the like of the automotive vehicle, the inertia 
body is caused to move axially against magnetic repulsion between the 
inertia body and a cylindrical magnet (not shown). As a result, the hammer 
pin 24 is caused to move toward the gas generator 30 so that the pointed 
end portion of the hammer pin 24 strikes and fires the detonator 33. The 
gas-generating chemical reagent 32 ignited as a result of the firing of 
the detonator 33 generates a great deal of high-temperature gas G. This 
high-temperature gas G breaks up the bottom of the casing 31 and blows out 
into a gas compartment 13 of the pretensioner 10. As a consequence, a 
piston 15 disposed within the cylinder 12 of the pretensioner 10 is driven 
by gas pressure P so that the piston 15 is caused to move within the 
cylinder 12. A wire cable 16 connected to the piston 15 is therefore 
pulled by pulling force F. Accordingly, the take-up reel 3 on which the 
wire cable 16 is wound is biased in a direction to wind up the webbing 4, 
whereby webbing slack is taken up. The occupant's body is therefore firmed 
restrained on the seat by the slack-free webbing 4, thereby reducing the 
distance of a sway toward the front of the vehicle body due to an impact 
of a collision and hence protecting the occupant from injuries which would 
otherwise occur as a result of impacting a steering wheel or the like. 
The above-described gas generator 30 is accommodated within the housing 11 
so that the gas generator 30 is located opposite the side wall 2f of the 
mounting bracket 2c. Further, the cap 35 defines the hammer pin guide 
aperture 35a through which the hammer pin 24 extends. As a consequence, a 
part of high-temperature and high-pressure gas G generated by the chemical 
reagent 32 flows backward and blows out through gaps between the gas 
generator 30 and housing 11 and the side wall 2f of the mounting bracket 
2c. The mounting bracket 2c is also provided with the through-bore 2d 
through which the hammer pin 24 extends. The high-temperature and 
high-pressure gas G which has passed through the through-bore 2d blows out 
through a gap between the impact pin trigger device 20 and the side wall 
2e of the mounting bracket 2c. Since the gas so blown out has a 
considerably high temperature, it may give unfavorable thermal influence 
to components arranged around the pretensioner 10 and the hammer pin 
trigger device 20. 
This potential problem is not limited to the above-described webbing 
retractor but also exists in the case of an air bag arranged inside the 
steering wheel or at another location as long as its gas generating device 
or the like is mounted in a similar manner. 
SUMMARY OF THE INVENTION 
With the foregoing in view, the present invention has as a primary object 
thereof the protection of peripheral components from such thermal 
influence by controlling the blow-out direction of high-temperature gas 
leaked out through a joint portion between a gas generator and a hammer 
pin trigger device. 
In one aspect of the present invention, there is thus provided a gas 
generating device comprising: 
a gas generator having a detonator; 
a hammer pin trigger device having a hammer pin arranged movably toward 
said detonator so that said hammer pin is caused to strike and fire said 
detonator; and 
gas guide means arranged at a joint portion between said gas generator and 
said hammer pin trigger device for guiding gas, which occurs upon firing 
said detonator, in a specific direction to an outside of said gas 
generating device. 
Owing to the provision of the gas guide means arranged at the joint portion 
between the gas generator and the hammer pin trigger device, the gas guide 
means can guide therealong high-temperature gas which occurs upon firing 
the detonator and would otherwise leak out along a joint between the gas 
generator and the hammer pin trigger device, so that the high-temperature 
gas is allowed to blow out in the specific direction to avoid thermal 
influence to peripheral components. 
In another aspect of the present invention, there is also provided a gas 
generating device comprising: 
a gas generator having a detonator; 
a hammer pin trigger device having a hammer pin arranged movably toward 
said detonator so that said hammer pin is caused to strike and fire said 
detonator; and 
a shielding member arranged outside a joint portion between said gas 
generator and said hammer pin trigger device for preventing gas, which 
leaks out along said joint portion upon firing said detonator, from 
blowing out in a specific direction. 
The provision of the shielding member outside the joint portion between the 
gas generator and the hammer pin trigger device makes it possible to block 
the gas leaked out along a joint between the gas generator and the hammer 
pin trigger device, so that the gas is prevented from directly hitting 
peripheral components.

DETAILED DESCRIPTION OF THE INVENTION AND PREFERRED EMBODIMENTS 
The preferred embodiments of the present invention will hereinafter be 
described in detail with reference to FIGS. 1 through 7 of the 
accompanying drawings, in which elements of structure similar to the 
corresponding elements in the conventional construction shown in FIGS. 8 
to 10 are identified by like reference numerals and their description will 
be adequately simplified to avoid superfluous description. 
A gas generating device according to the first embodiment of the present 
invention will be described with reference to FIGS. 1 through 4. 
This gas generating device 100 is basically similar to that illustrated in 
FIGS. 8 through 10. As is shown in FIG. 1, the gas generator 30 and the 
hammer pin trigger device 20 are assembled together with the mounting 
bracket 2c being located therebetween. A joint portion is therefore formed 
between the gas generator 30 and the hammer pin trigger device 20. 
A characteristic construction of this embodiment resides in the provision 
of gas guide slots 50,51 at the mounting bracket 2c of the frame 2, 
whereby the through-bore 2d is communicated to an outside of the gas 
generating device along the mounting bracket 2c. 
As is shown in FIG. 2, cut-off portions 21c,25b are provided in a sectorial 
form in a mounting face of the housing 21 of the hammer pin trigger device 
20 and a mounting face of the hammer pin guide member 25 closing the open 
end of the housing 21, respectively. At these mounting faces, the housing 
21 and the hammer pin guide member 25 are mounted on the mounting bracket 
2c. The cut-off portions 21c,25b extend from an outer peripheral portion 
of the hammer pin trigger device 20 to the through-bore 2d formed in the 
mounting bracket 2c. This particular shape of the cut-off portions 21c,25b 
is to allow high-temperature gas to spread out in the sectorial form so 
that the reachable distance of the high-temperature gas is limited. Owing 
to the provision of these cut-off portions 21c,25b, the gas guide slot 50 
adapted to guide the high-temperature gas G is formed when the hammer pin 
trigger device 20 is mounted on the side wall 2e of the mounting bracket 
2c. 
Exactly the same cut-off portions are also formed in mounting faces of the 
gas generator 30 and the housing 11 of the pretensioner 10 which 
accommodates the gas generator 30. At these mounting faces, the gas 
generator 30 and the housing 10 are mounted on the mounting bracket 2c. As 
a consequence, a gas guide slot 51 is formed to guide the high-temperature 
gas G. 
As is appreciated from the foregoing description, the gas guide slots 50,51 
allow the high-temperature (and also high-pressure) gas G, which has 
flowed to a side of the hammer pin 24 upon firing the detonator 33 by the 
hammer pin 24, to blow out of the gas generating device through the gas 
guide slots 50,51. When the gas generator 30 and the hammer pin trigger 
device 20 are fixed on the mounting bracket 2c, they cannot be mounted on 
the side walls 2f,2e without any gap so that gaps communicated with the 
through-bore 2d are unavoidably formed at locations other than the gas 
guide slots 50,51. The high-temperature gas G is however allowed to blow 
out through the gas guide slots 50,51 because it is easier for the 
high-temperature gas G to flow through the gas guide slots 50,51 than such 
gaps. 
It is accordingly possible to protect peripheral components from adverse 
thermal effects of the high-temperature gas G by adequately setting the 
positions of the gas guide slots 50,51, for example, in such a way that 
the high-temperature gas G blows out in directions where there is a 
relatively wide open space without components made of a synthetic resin. 
In the first embodiment described above, the bracket 2c is arranged at the 
joint portion between the gas generator 30 and the hammer pin trigger 
device 20. It is however not necessary to provide the joint portion with 
such a bracket. 
Namely, the gas generator 30 and the hammer pin trigger device 20 may be 
bolted together either directly or by way of the mounting flanges 21a,21b. 
It is to be noted that similar flanges are arranged on the side of the gas 
generator 30. In this modification, the mounting on the bracket 2c is 
effected at positions other than the joint portion between the gas 
generator 30 and the hammer pin trigger device 20. In the above 
modification, gas guide means can be provided, for example, by axially 
cutting off a part of threads or forming slots in the flange portions. 
According to the second embodiment of the present invention, the gas guide 
slots 50,51 are formed in a different manner. The second embodiment will 
next be described with reference to FIGS. 5 and 6. 
In the second embodiment depicted in FIGS. 5 and 6, the hammer pin trigger 
device 20 is mounted on the bracket 2c via a spacer 40 which is preferably 
made of a metal although a heat-resistant resin or a thermosetting resin 
can be employed. In the spacer 40, a cutoff portion 40c is formed 
extending from an outer periphery thereof to a hammer pin insertion hole 
40b. Further, an exactly the same cut-off portion 41c is also formed in a 
spacer 41 interposed between a gas generator (not shown) on a side of the 
housing 11 of the pretensioner 10, said housing 11 accommodating the gas 
generator, and the mounting bracket 2c. The spacers 40,41 are mounted so 
that their cut-off portions 40c,41c are located opposite each other. 
The gas guide slots 50,51 are therefore easily formed by mounting these 
spacers 40,41 on the bracket 2c. These spacers 40,41 also have function as 
sealing means between the bracket 2c and the hammer pin trigger device 20 
and gas generator 30, thereby achieving effective sealing at locations 
other than the gas guide slots 50,51. 
The gas generating device according to the third embodiment of the present 
invention will next be described with reference to FIG. 7. 
As is illustrated in FIG. 7, the gas generating device according to the 
third embodiment is different from the conventional gas generating device 
of FIGS. 8 through 10 in that a gas shielding plate 60 is additionally 
arranged along the gas generating device. 
The gas shielding plate 60 has been formed by pressing a metal plate 
resistant to high temperatures and high pressures, for example, a steel 
plate into an L-shaped configuration as viewed in cross-section, and 
comprises a vertical wall 61 extending substantially at a right angle 
relative to the mounting bracket 2c and substantially in parallel with the 
webbing 4 and a horizontal wall 62 also extending at substantially right 
angle relative to the mounting bracket 2c and interposed between the gas 
generating device and the take-up reel 3. Mounting flanges 63 which are 
pendant from a distal edge portion of the horizontal wall 62 are 
threadedly secured on the side walls 2a,2b of the frame 2 by mounting 
bolts 64, respectively. 
High-temperature gas, which has leaked out between a mounting face of the 
gas generating device and the bracket 2c, is blocked by the shielding 
plate 60 so that the high-temperature gas does not blow out directly 
toward the webbing 4 wound out from the take-up reel 3 or the webbing 4 
wound on the take-up reel 3. The webbing 4 can therefore be protected from 
adverse thermal effects. Owing to the provision of the shielding plate 60 
outside the joint portion between the gas generator 30 and the hammer pin 
trigger device 20 so that gas leaked out along the joint portion is 
blocked from blowing out in a specific direction, the gas leaked out along 
the joint is blocked by the shielding plate and is prevented from directly 
hitting peripheral components. 
Needless to say, the shape of the shielding plate 60 is not necessarily 
limited to such an L-shape in cross-section (namely, the vertical wall 61 
and the horizontal wall 62 extend at right angle relative to each other) 
as shown in FIG. 7 and can be modified as needed. To effectively block gas 
leaked out along the joint, it is however preferred to arrange the 
shielding plate in such a way that the shielding plate extends in a 
direction perpendicular to the direction in which the mounting bracket 2c 
extends. 
In each of the above embodiments, the gas generating device according to 
the present invention was explained in the form as applied to the webbing 
retractor for the automotive vehicle. As described at the beginning, the 
present invention is also applicable to a gas generating device of an air 
bag system or the like. 
As has been described above, the gas generating device according to each 
embodiment of the present invention is provided with the gas guide slots 
for guiding gas, which leaks out along a mounting face at which the gas 
generating device is mounted on the mounting bracket, in a particular 
direction to allow the gas to blow out in that particular direction or is 
provided with the shielding plate for blocking the gas so leaked. It is 
therefore possible to prevent high-temperature gas, which has been 
generated by the detonator, from directing contacting peripheral 
components, thereby protecting the peripheral components from deleterious 
effects such as thermal deformation.