U.S. patent application number 11/065444 was filed with the patent office on 2005-10-06 for device for cutting a structure in a motor vehicle.
This patent application is currently assigned to PYROALLIANCE. Invention is credited to Borg, Evrard, D'emmanuelle, Laurent, Laspesa, Eric.
Application Number | 20050217466 11/065444 |
Document ID | / |
Family ID | 34878487 |
Filed Date | 2005-10-06 |
United States Patent
Application |
20050217466 |
Kind Code |
A1 |
Borg, Evrard ; et
al. |
October 6, 2005 |
Device for cutting a structure in a motor vehicle
Abstract
The technical field of the invention is that of motor vehicle
safety involving devices for cutting a structure such as, for
example, an instrument panel, so as to actuate a safety device. The
object of the present invention relates more specifically to a
device (1) for cutting a structure in a motor vehicle comprising a
linear pyrotechnic charge (5) placed inside a flattened deformable
tube (6), combustion of the said charge (5) bringing about
deformation of the tube (6) which increases its cross section, the
said deformation causing the structure (3) to break. The main
characteristic of this device is that the combustion rate of the
pyrotechnic charge (5) is less than 3000 m/s.
Inventors: |
Borg, Evrard; (Sanary,
FR) ; Laspesa, Eric; (Six Fours Les Plages, FR)
; D'emmanuelle, Laurent; (Toulon, FR) |
Correspondence
Address: |
OLIFF & BERRIDGE, PLC
P.O. BOX 19928
ALEXANDRIA
VA
22320
US
|
Assignee: |
PYROALLIANCE
Les Mureaux
FR
78130
|
Family ID: |
34878487 |
Appl. No.: |
11/065444 |
Filed: |
February 25, 2005 |
Current U.S.
Class: |
89/1.14 |
Current CPC
Class: |
F42B 3/006 20130101;
F42B 15/38 20130101; B26F 3/04 20130101; F42B 15/36 20130101 |
Class at
Publication: |
089/001.14 |
International
Class: |
F42B 012/58 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 2, 2004 |
FR |
0403469 |
Claims
1. Device for cutting a structure in a motor vehicle comprising a
linear pyrotechnic charge placed inside a flattened deformable
tube, combustion of the said charge brining about deformation of
the tube which increases its cross section, the said deformation
causing the structure to break, characterized in that the
combustion rate of the pyrotechnic charge is less than 3000
m/s.
2. Cutting device according to claim 1, characterized in that the
pyrotechnic charge comprises a plurality of strands.
3. Cutting device according to claim 1, characterized in that the
tube is metallic.
4. Device according to claim 1, characterized in that the tube is
closed at each of its ends by a stopper so as to contain the
pyrotechnic effects inside the said tube.
5. Device according to claim 3, characterized in that the tube is
made of aluminum.
6. Device according to claim 1, characterized in that a space
exists between the pyrotechnic charge and the tube, the said space
being packed with a foam made of an elastomer.
7. Device according to claim 1, characterized in that a device for
igniting the pyrotechnic charge comprising an igniter is placed at
one of the ends of the tube.
8. Device according to claim 1, characterized in that the flattened
tube is housed in a groove of the structure having a U-shaped cross
section, the bottom of the groove including a secondary groove and
the tube being held by means of a closure clip.
9. Device according to claim 1, characterized in that the linear
density of the pyrotechnic charge is less than 4 g/m.
10. Cutting device according to claim 2, characterized in that the
tube is metallic
Description
[0001] The technical field of the invention is that of motor
vehicle safety involving devices for cutting a structure such as,
for example, an instrument panel, so as to actuate a safety device.
Cutting devices according to the invention are particularly suited
to the application of airbags in a motor vehicle.
[0002] Devices for cutting a structure have already been the
subject of several patents.
[0003] Mention may be made of patent EP 0 273 061 which describes a
separation joint between two structures and involves a linear
explosive charge confined in a flattened tube. The two structures
fit into each other and ignition of the explosive charge brings
about expansion of the tube which then deforms one of the two
structures bringing about their separation. The explosive charge is
not specifically described but the description reveals some
indications that suggest that it consists of a detonating
charge.
[0004] Similarly, the separating device disclosed in U.S. Pat. No.
6,170,400 or in U.S. Pat. No. 5,372,071 employs a detonating fuse,
ignition of which will bring about deformation of the tube in which
it is housed so as to push back a piston in order to separate two
sub-assemblies.
[0005] Finally, mention may be made of U.S. Pat. No. 5,478,106
which describes an opening system for deploying an airbag. This
opening system comprises a deformed tube having a tapered part and
in which a linear pyrotechnic charge is housed. Ignition of the
said charge brings about expansion of the tube, the tapered part of
which comes into contact with the structure in order to cut it.
[0006] Cutting devices according to the invention employ
deflagrating fuses housed in flattened tubes and ignition of these
causes the cross section of the said tubes to expand so as to cut a
structure. Deflagrating fuses have slower reaction rates than those
of detonating fuses and the associated pyrotechnic effects are
consequently less violent and in particular the risks of projection
of splinters and the emission of shock waves in the air outside the
said devices become negligible. Cutting devices according to the
invention are particularly suited to motor vehicles in as much as
they are reliable and efficient while exhibiting an increased
safety level by limiting the intensity of the reaction and hence
the possibilities of physical injuries.
[0007] The object of the present invention relates to a device for
cutting a structure in a motor vehicle comprising a linear
pyrotechnic charge placed inside a flattened deformable tube,
combustion of the said charge bringing about deformation of the
tube which increases its cross section, the said deformation
causing the structure to break, characterized in that the
combustion rate of the pyrotechnic charge is less than 3000
m/s.
[0008] In this patent application, the expressions "deflagrating
charge" and "charge of which the combustion rate is less than 3000
m/s" are equivalent.
[0009] This equivalence is desirable since although deflagration is
defined by a longer and less violent reaction than a detonation, it
remains relatively poorly defined as regards the value of certain
parameters characterizing it.
[0010] The combustion rate of the pyrotechnic charge preferably
lies between 1000 m/s and 2000 m/s.
[0011] The deflagrating charges selected for cutting devices
according to the invention are sufficiently lively to bring about
cutting of a structure in a motor vehicle, without exhibiting
difficulties associated with the use of a detonating charge such as
for example the risks of the cutting device breaking with emission
of undesirable pyrotechnic effects such as a shock wave in the air
and the projection of splinters.
[0012] Advantageously, the pyrotechnic charge comprises a plurality
of strands such as, for example, those described in U.S. Pat. No.
4,220,087.
[0013] The tube is preferably metallic.
[0014] Advantageously, the said tube has a good ability to deform
plastically.
[0015] Preferably, the tube is closed at each of its ends by a
stopper so as to contain the pyrotechnic effects inside the said
tube.
[0016] Indeed, since the requirements for motor vehicle safety are
particularly high, it is recommended to minimize the risks of the
propagation of untimely effects outside the cutting device.
[0017] The tube is preferably made of aluminium.
[0018] Advantageously, a space exists between the pyrotechnic
charge and the tube, the said space being packed with a foam made
of an elastomer intended, on the one hand, to hold the said charge
in the centre of the said tube, and, on the other hand, to increase
the pressurization of the said tube. In this way, this makes it
possible, with a small pyrotechnic charge and therefore with a
small quantity of gas produced, to maximize stresses, even in
strong tubes, so that they recover their original cylindrical
shape.
[0019] Preferably, a device for igniting the pyrotechnic charge
comprising an igniter is placed at one of the ends of the tube.
[0020] Advantageously, the flattened tube is housed in a groove of
the structure having a U-shaped cross section, the bottom of the
groove including a secondary groove and the tube being held by
means of a closure clip.
[0021] Preferably, the linear density of the pyrotechnic charge is
less than 4 g/m.
[0022] Cutting devices according to the invention have the
advantage of not being dangerous for persons, whether they are
functioning normally or erratically, in as much as the effects
produced remain of low intensity. Moreover, they are reliable,
since ignition of such compositions is perfectly controlled.
Finally, on account of the great diversity of deflagrating
compositions that can be used, cutting devices according to the
invention can be adapted to a large number of configurations
associated in particular with the thickness of the structure to be
cut, with the material constituting the said structure and with the
surface to be cut.
[0023] A detailed description of a preferred embodiment of the
invention is given hereinafter with reference to FIGS. 1 and 2.
[0024] FIG. 1 is a view in lateral axial section of a cutting
device according to the invention, positioned in relation to the
structure to be cut and not having yet functioned.
[0025] FIG. 2 shows the cutting device of FIG. 1 after
operation.
[0026] With reference to FIG. 1, the cutting device 1 according to
the invention is inserted into a groove 2 of the structure 3 to be
cut, the said groove 2 having a U-shaped cross section, the bottom
of which includes a secondary v-shaped groove so that the thickness
of the structure 3 in the region of the said secondary groove 4 is
at a minimum. A linear pyrotechnic charge 5 consisting of three
strands is housed in the centre of a hollow deformable aluminium
tube 6, the said tube 6 being flattened so as to have an elongate
section possessing two flat sides that are parallel to each other
and connected to each other by two segments in the arc of a circle,
the said charge 5 being in contact with the two flat sides of the
tubes 6. The space existing between the pyrotechnic charge 5 and
the inner wall of the tube 6 is packed with an elastomeric foam 7
to assist in holding the said charge 5 in the centre of the said
tube 6. The tube 6 occupies the groove 2 without any lateral play,
in other words each of the two flat sides of the tube 6 is in
contact with the walls of the groove 2. The groove 2 is made in a
bead of the structure 3 and the tube 6 is held in the groove 2 by
means of a closure clip 8 covering the said groove 2. The tube 6 in
the groove 2 is in contact at the same time with the bottom of the
said groove 2 and the closure clip 8. An ignition device comprising
a single igniter is placed close to the tube 6. Two stoppers close
the ends of the said tube 6.
[0027] With reference to FIGS. 1 and 2, the method of operating the
cutting device according to the invention is as follows.
[0028] Ignition of the pyrotechnic charge 5 brings about the
production of gas in the tube 6 which is then subjected to a high
internal pressure. The tube 6 reacts by deforming so as to adopt a
circular cross section.
[0029] This expansion causes the structure 3 to break in the region
of its smallest thickness created by the secondary groove 4, as
well as the closure clip 8. The structure is, thus cut and all the
pyrotechnic effects remain contained in the tube 6.
* * * * *