U.S. patent application number 09/797550 was filed with the patent office on 2001-07-05 for pretensioner.
Invention is credited to Bland, Stuart, Downie, Andrew, Patrickson, James, Thirlwell, Bryan.
Application Number | 20010006290 09/797550 |
Document ID | / |
Family ID | 10849109 |
Filed Date | 2001-07-05 |
United States Patent
Application |
20010006290 |
Kind Code |
A1 |
Patrickson, James ; et
al. |
July 5, 2001 |
Pretensioner
Abstract
A pretensioner for a vehicle occupant safety restraint has an
outer casing that contains a gas generant. An igniter has igniter
material disposed within an igniter housing. A pair of electrodes
are connected to the igniter material. A grounding path connector
link electrically connects the igniter housing to a grounding path.
The connector link may be formed by springs connecting the outer
case to the grounding electrode and an interference fit connecting
the igniter housing to the outer case. The link forms a low
resistance path to short circuit undesirable static charges in the
unit that would otherwise tend to cause unintentional activation of
the pretensioner.
Inventors: |
Patrickson, James; (England,
GB) ; Downie, Andrew; (England, GB) ; Bland,
Stuart; (England, GB) ; Thirlwell, Bryan;
(England, GB) |
Correspondence
Address: |
BREED AUTOMOTIVE TECHNOLOGY, INC
5300 ALLEN K BREED HIGHWAY
P O BOX 33050
LAKELAND
FL
33807-3050
US
|
Family ID: |
10849109 |
Appl. No.: |
09/797550 |
Filed: |
March 2, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09797550 |
Mar 2, 2001 |
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09347500 |
Jul 2, 1999 |
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6234524 |
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Current U.S.
Class: |
280/806 |
Current CPC
Class: |
B60R 22/4628 20130101;
F42B 3/18 20130101; B60R 2021/26029 20130101; B60R 21/264
20130101 |
Class at
Publication: |
280/806 ;
102/530 |
International
Class: |
C06D 005/00; B60R
022/36 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 5, 1999 |
GB |
99 05 188.0 |
Claims
1. A pretensioner for a vehicle occupant safety restraint
comprising: an outer casing; gas generant contained within said
outer case; an igniter comprising igniter material within an
igniter housing; a pair of electrodes connected to said igniter
material; a ground path connector link electrically connecting the
igniter housing to a grounding path.
2. The pretensioner for a vehicle occupant safety restraint
according to claim 1 arranged so that the connector link
electrically connects the igniter housing to one of the
electrodes.
3. The pretensioner for a vehicle occupant safety restraint
according to claim 1 wherein the link is a very low resistance
link.
4. The pretensioner for a vehicle occupant safety restraint
according to claim 1 wherein the igniter housing is electrically
connected to the outer case of the pretensioner.
5. The pretensioner for a vehicle occupant safety restraint
according to claim 4 wherein the igniter housing is an interference
fit in the case.
6. The pretensioner for a vehicle occupant safety restraint
according to claim 4 wherein one of the electrodes forms an
electrical connection to the outer case.
7. The pretensioner for a vehicle occupant safety restraint
according to claim 6, wherein said one of the electrodes comprises
a bent section protruding through the igniter housing and fitting,
interference wise, with the outer case.
8. The pretensioner for a vehicle occupant safety restraint
according to claim 1 wherein the connector link is provided by a
resilient member.
9. The pretensioner for a vehicle occupant safety restraint
according to claim 8 wherein the resilient member comprises a
spring pressed over one of the electrodes.
10. The pretensioner for a vehicle occupant safety restraint
according to claim 1 wherein the igniter housing comprises a
non-conductive material and the igniter housing has a cap which is
crimped with the outer case directly into a conductive sleeve.
11. The pretensioner for a vehicle occupant safety restraint
according to claim 10 wherein one of the electrodes is modified so
that a flat anti-rotation feature is extended outwards to contact
with the conductive sleeve.
12. The pretensioner for a vehicle occupant safety restraint
according to claim 1 wherein the igniter housing is moulded or cast
from conductive material and one of the pins is coated with an
insulating material.
13. The pretensioner for a vehicle occupant safety restraint
according to claim 12 wherein the igniter housing cap and the outer
case are crimped directly onto a conductive sleeve thus creating a
low resistance link between the conductive igniter housing and the
electrode.
14. The pretensioner for a vehicle occupant safety restraint
according to claim 13 wherein the second electrode is insulated
from the igniter housing.
15. The pretensioner for a vehicle occupant safety restraint
according to claim 1 wherein the igniter housing cap is designed as
an interference fit with the outer case, so as to electrically
connect the two components, and an electrical connection is formed
between the outer case and one of the electrodes, said connection
comprising an extended leg jutting from the outer case to contact
the electrode.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a pretensioner for a
vehicle occupant safety restraint, particularly for a seat
belt.
BACKGROUND OF THE INVENTION
[0002] Pretensioners are used to rapidly pull in slack in a safety
restraint seat belt at the onset of a crash to more securely
restrain the vehicle occupant against forward movement and
potential injury by collision with structural features of the
vehicle. In addition, the pretensioning operation pulls the
occupant into, or at least towards, the correct seating position to
maximize the effect of a second restraint such as an airbag.
[0003] A modern seat belt is known as a 3-point restraint because
it is secured to the vehicle at three points arranged about the
vehicle occupant to provide a diagonal torso section and a
horizontal lap portion to hold the vehicle occupant in the seat.
The belt is attached to the vehicle by a spring-loaded retractor
tending to tighten in the belt, and by a buckle for quick release
of the belt.
[0004] Pretensioners are typically sited at the retractor or at the
buckle end of the restraining seat belt. They are designed to store
energy which when released effects the pretensioning operation.
This energy may be mechanical energy in the form of a stressed
spring, but more modern pretensioners are pyrotechnically operated.
Pyrotechnically operated pretensioners comprise a sealed tube
containing a gas generant composition which reacts rapidly to
generate gas which expands rapidly to provide the energy to effect
the pretensioning operation. The gas generant composition is
ignited electrically via pin terminals protruding from the
pretensioning tube and connected to an intermediate igniter
material.
[0005] Discussion of the Prior Art
[0006] The general construction of a pretensioner and the manner in
which it is fitted into a vehicle to control a safety restraint
seat belt is well known to persons skilled in the art. One such
example is shown and described in EP 827 883 A.
SUMMARY OF THE INVENTION
[0007] One problem with pyrotechnically operated pretensioners is
that spurious electric charges can produce inadvertent activation
of the pretensioner. For example static charge may build up within
the sub-assembly of the pretensioner. When the unit passes over or
through any static field a low voltage will flow across the
sensitive igniter material. This low voltage will in time break
down the protective coating on the igniter material and once
exposed it will react with oxygen and ignite thus causing the
pretensioner to be activated.
[0008] In addition, inadvertent firing will occur with single
discharges of static electricity, especially across the igniter
material, which provides a short path between the firing pins and
the igniter casing.
[0009] The present invention aims to provide an improved
pretensioner, which can be used at either end of the seat belt.
[0010] According to one aspect of the present invention there is
provided a pretensioner for a vehicle occupant safety restraint
comprising: an outer casing; gas generant contained within said
outer case; an igniter comprising igniter material within an
igniter housing; a pair of electrodes connected to said igniter
material; and a ground path connector link electrically connecting
the igniter housing to a grounding path.
[0011] Preferably the connector link electrically connects the
igniter housing to one of the electrodes. Advantageously the link
is a very low, or even almost zero, resistance link and is
connected to one of the pins only with a shorting connection
between the two electrodes being provided.
[0012] Thus a low resistance link is provided for the charge to
take through the unit so as to prevent the build up of charge and
thus inhibit spurious activation of the pretensioner.
[0013] According to a first embodiment of the present invention the
pretensioner is constructed so that the igniter housing is
electrically connected to the outer case of the pretensioner, for
example by making it an interference fit in the case, and one of
the electrode pins (preferably the grounded one) forms an
electrical connection to the outer case, for example it may
comprise a bent section protruding through the igniter housing and
fitting, interference wise, with the outer case. Thus a short
circuit is provided between the igniter housing and the grounded
electrode pin via the outer case to discharge spurious static
currents.
[0014] This embodiment has the advantage of requiring few parts and
no substantial modification of the igniter housing. Also there are
only two points which need maintain electrical connection.
[0015] According to a second embodiment the link is provided by a
resilient member, preferably a spring pressed over one of the pins.
The igniter housing is again formed as an interference fit with the
outer case and the spring providing the low resistance link from
the case to the pin.
[0016] The resilience of the spring maintains the electrical
connections and reduces the risk of the contact being broken. This
embodiment also requires very little or no changes to the igniter
housing design.
[0017] According to a third embodiment the igniter housing is made
from non-conductive material and the igniter housing has a cap
which is crimped with the outer case directly into a conductive
sleeve, and one of the pins is modified so that a flat
anti-rotation feature is extended outwards to contact with the
conductive sleeve. This embodiment has the advantage that a
relatively low number of electrical contacts are required and
little modification to manufacturing tools is needed.
[0018] According to a fourth embodiment the igniter housing is
molded or cast from conductive material and one of the pins is
coated in an insulating material such as plastic. The igniter
housing cap and the outer case are crimped directly onto a
conductive sleeve thus creating a low resistance link between the
conductive igniter housing and the pin. The second pin is insulated
from the igniter housing. This has the advantage of reducing the
number of electrical contacts, and requiring no additional
components.
[0019] According to a fifth embodiment the igniter housing cap is
designed as an interference fit with the outer case, so as to
electrically connect the two components, and an electrical
connection is formed between the outer case and one of the pins,
for example by an extended leg jutting from the outer case to
contact the pin. This embodiment requires no additional parts and
no modification to existing manufacturing tools.
[0020] Of course, modifications and combinations of the features of
each of the embodiments are envisaged and are intended to be within
the scope of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] For a better understanding of the present invention and to
show how the same may be carried into effect, reference will now be
made to the accompanying drawings, in which:
[0022] FIG. 1 is a cross-sectional view of part of a known prior
art pretensioner;
[0023] FIG. 2 is a cross-sectional view of part of a pretensioner
according to one embodiment of the present invention;
[0024] FIG. 3 is a cross-sectional view of part of a pretensioner
according to a second embodiment of the present invention;
[0025] FIG. 4 is a cross-sectional view of part of a pretensioner
according to a third embodiment of the present invention;
[0026] FIG. 5 is a cross-sectional view of part of a pretensioner
according to a fourth embodiment of the present invention;
[0027] FIG. 6 is a cross-sectional view of part of a pretensioner
according to a fifth embodiment of the present invention;
[0028] FIG. 7 is a cross-sectional view of part of a pretensioner
according to a sixth embodiment of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0029] In the Figures like parts are denoted by like reference
numbers.
[0030] Referring first to FIG. 1 there is shown is a
cross-sectional view of part of a known prior art pretensioner. The
pretensioner comprises an outer case 1 in the form of a cylindrical
tube of metallic material. This is filled with a gas generant 5,
numerous examples of which are known to those skilled in the art.
Within the outer case 1 is situated a small quantity of sensitive
igniter material 2 sandwiched behind an igniter header cap 4. The
igniter material 2 has a thickness indicated by 7.
[0031] Two electrode pins 3, 3a pass through a seal 6 forming the
igniter housing 8 at the end of the outer case 1. They are
connected by means of a thin wire (not shown) welded to each pin
and lying adjacent to or embedded in the igniter material 2. One of
the pins 3 is connected to ground and thus provides a grounding
path.
[0032] When an electric current is applied across the electrode
pins 3, 3a, the thin wire heats up and ignites the igniter material
2. This activates the main gas generant material 5.
[0033] Spurious electric charges, such as those which result from
electrostatic build up, can cause an undesirable discharge of
current from the outer case 1 to the header cap 4 and thus through
the sensitive igniter material 2 to the grounding pin 3. When such
a current passes through the igniter material it often causes
ignition leading to spurious activation of the pretensioner.
[0034] FIGS. 2 to 6 show several embodiments of the invention in
which spurious discharges are reduced.
[0035] A first embodiment of the invention is shown in FIG. 2. The
electrode 3a has a U-bend 9 formed to connect with the inside wall
of the outer case 1 and form an electrical connection therewith. In
addition the header cap 4 is modified to provide an electrical
connection with the inside wall of the outer case 1 by an outwardly
bent portion in the form of projecting tangs 10. Thus an electrical
connection is provided between the header cap 4 and the grounding
pin 3, via the outer case 1, of relatively low resistance so that
spurious charges are discharged to ground before they build up
sufficiently to activate the sensitive igniter material 2.
[0036] The second embodiment shown in FIG. 3 utilises a pressed
metal clip 11 to provide a link from the generator case 1 to the
grounding pin 3. As in the embodiment of FIG. 1 the header cap 4 is
formed as an interference fit with the outer case by means of tangs
10 contacting the inside surface of the outer case. Again this
provide a short circuit to ground for spurious charges. The tangs
may be formed on assembly of the pretensioner by the case being
inserted over the header cap.
[0037] FIG. 4 is similar to FIG. 3 but shows the use of a stainless
steel tension spring 12 wound around the grounding pin 3 with its
free end connected to the generator outer case 1 to provide the
required short circuit link between the case 1 and ground. This is
in place of the pressed spring 11 shown in FIG. 3. The link between
the header cap 4 and the case 1 is again provided by bent tags 10.
An annular groove 13 of between 0.3 and 0.5 mm depth is formed in
the case to clamp the case to the fuse seal 6 and retain the two to
a pull off load of up to 250 N. A plurality of stakes 18, typically
eight, equally spaced around the circumference of the groove serve
to make the connection stronger.
[0038] In FIG. 5 the igniter housing 8 comprises two parts: a
conductive outer sleeve 13, formed for example from aluminium, and
a non-conductive insert 14 which may be moulded of standard
plastics material such as that known as PBT. The outer sleeve
provides a direct electrical connection to the outer case 1. The
outer sleeve is connected to the grounding pin 3 by a stainless
steel pin 15. This stainless steel pin is formed by a relatively
small change to the anti-rotation feature.
[0039] FIG. 6 illustrates an embodiment in which the grounding pin
3 is directly connected to both the outer case 1 and to the header
cap 4 by using a conductive plastic material for the igniter
housing 8. This will provide the low resistance short circuit path
required from the header cap 4 to ground. However, in this
embodiment it is necessary to insulate the other electrode pin 3a
and this is done by dipping it into insulating plastics material 16
prior to moulding the housing 8 around the pins 3, 3a.
[0040] Another embodiment is shown in FIG. 7 where the outer case 1
is formed with an extending leg 17 which contacts the grounding pin
3 directly. The header cap 4 is formed as an interference fit with
tangs 10 to provide the connection from the header cap to the case,
as in the embodiments of FIGS. 2, 3 and 4. A circumferential groove
13 with spaced stakes is also provided to ensure a strong
connection between the case 1 and the igniter housing 8 as in the
embodiment of FIG. 4.
[0041] Many changes and modifications in the above described
embodiments of the invention can, of course, be carried out without
departing from the scope thereof. Accordingly, that scope is
intended to be limited only by the scope of the appended
claims.
* * * * *