Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F42—AMMUNITION; BLASTING
  • F42B—EXPLOSIVE CHARGES, e.g. FOR BLASTING, FIREWORKS, AMMUNITION
  • F42B3/00—Blasting cartridges, i.e. case and explosive
  • F42B3/10—Initiators therefor
  • F42B3/12—Bridge initiators
  • F42B3/121—Initiators with incorporated integrated circuit
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F42—AMMUNITION; BLASTING
  • F42B—EXPLOSIVE CHARGES, e.g. FOR BLASTING, FIREWORKS, AMMUNITION
  • F42B3/00—Blasting cartridges, i.e. case and explosive
  • F42B3/10—Initiators therefor
  • F42B3/195—Manufacture
  • F42B3/198—Manufacture of electric initiator heads e.g., testing, machines
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B60—VEHICLES IN GENERAL
  • B60R—VEHICLES, VEHICLE FITTINGS, OR VEHICLE PARTS, NOT OTHERWISE PROVIDED FOR
  • B60R21/00—Arrangements or fittings on vehicles for protecting or preventing injuries to occupants or pedestrians in case of accidents or other traffic risks
  • B60R21/02—Occupant safety arrangements or fittings, e.g. crash pads
  • B60R21/16—Inflatable occupant restraints or confinements designed to inflate upon impact or impending impact, e.g. air bags
  • B60R21/26—Inflatable occupant restraints or confinements designed to inflate upon impact or impending impact, e.g. air bags characterised by the inflation fluid source or means to control inflation fluid flow
  • B60R2021/26029—Ignitors

Definitions

• the field of the present invention is that of pyrotechnic initiators / that is to say components making it possible to transmit a pyrotechnic effect in a pyrotechnic chain.
• Their external profile thus has a generally cylindrical shape which is intended to cooperate with a complementary cavity of the gas generator or of the pyromechanism. They also have a bead which acts as a stop during assembly, a bead which also makes it possible to ensure sealing by serving as a bearing surface for an O-ring.
• These initiator boxes are generally produced by injection or overmolding.
• the initiator according to the invention has a structure which makes it possible to manufacture it at a lower cost for a given external geometry.
• the mounting method according to the invention also allows lower cost to produce initiators having various external dimensions.
• the method according to the invention also makes it possible to easily integrate into the initiator electronic components providing additional functions (electromagnetic or electrostatic protection, logic circuits, firing device, etc.). Thanks to the invention, the internal part of the initiator is the same regardless of the external geometry of the complete component. It is therefore possible to mass produce the essential and a priori most expensive part of the initiator, ie the box which contains the pyrotechnic composition as well as its initiation means.
• the initiator is then personalized by placing this box in an envelope having external dimensions appropriate to the needs of a client.
• the subject of the invention is a pyrotechnic initiator comprising at least one pyrotechnic composition disposed inside a housing composed of a substantially cylindrical case extended by at least two pins, initiator characterized in that the housing is disposed at the 'interior of an envelope formed by the joining of at least two shells, envelope defining an internal volume receiving the housing.
• the envelope is advantageously formed by the attachment of an upper shell, delimiting the internal volume receiving the housing, and of a shell lower, carrying holes allowing the pins of the housing to pass.
• the envelope may be formed by the attachment of an upper shell, delimiting the internal volume receiving the housing, and of a lower shell, carrying holes allowing at least two electrodes to pass, pins and electrodes being connected to a circuit arranged in the internal volume.
• the circuit can be carried by a plate arranged perpendicular to the pins and the electrodes.
• the plate may be housed in a bore arranged in the lower shell.
• the circuit can alternatively be housed in the upper shell.
• the circuit will include at least one component providing protection against electromagnetic waves and / or electrostatic discharges.
• the circuit may include at least one component providing a function for decoding a firing signal.
• the envelope has an external profile allowing it to be fixed to a gas generator or a pyromechanism.
• the shells can be made integral with one another by ultrasonic welding.
• the invention also relates to a method of mounting a pyrotechnic initiator which allows its adaptation to a gas generator or a particular pyromechanism, this method is characterized in that it comprises the following steps: on the one hand an initiator housing comprising a substantially cylindrical case extended by at least two pins,
• At least one enclosure is produced which has an external profile allowing it to be adapted to a gas generator or a specific pyromechanism, enclosure comprising an upper shell and a lower shell, said shells defining an internal volume making it possible to receive the housing,
• the housing is placed in the envelope, - the two shells of the housing are secured.
• each envelope having a different external profile
• each envelope comprising an upper shell and a lower shell, said shells defining an internal volume making it possible to receive the housing.
• We will then choose the envelope having the external profile corresponding to the gas generator or to the pyromechanism on which we wish to adapt the initiator.
• We will then have the housing in the envelope thus chosen, finally we will secure the two shells of the housing.
• the initiator box can be fixed to an electronic circuit before being housed in the chosen envelope.
• FIG. 1 represents in section an initiator according to the invention
• FIGS. 2a and 2b represent the lower shell alone
• FIG. 2a being a section of FIG. 2b along the plane AA
• FIG. 3 is a sectional view of the upper shell alone
• FIG. 4 shows schematically the different steps of an assembly method according to the invention.
• FIGS. 5 and 6 represent an initiator according to a second embodiment, FIG. 5 being a partial longitudinal section along the plane CC of FIG. 6 and the latter being a cross section of FIG. 5 along the plane BB, Figure 7 shows in partial longitudinal section an initiator according to a third embodiment.
• a pyrotechnic initiator 1 according to the invention comprises an internal box 2 arranged inside an envelope 3.
• the housing 2 comprises a metallic case 4 (for example made of stainless steel) which is substantially cylindrical and contains an inflammatory pyrotechnic composition 5, for example a composition associating Boron and potassium nitrate in the proportions by mass of 70% Boron for 30% potassium nitrate.
• an inflammatory pyrotechnic composition 5 for example a composition associating Boron and potassium nitrate in the proportions by mass of 70% Boron for 30% potassium nitrate.
• the case 4 is closed by an equally metallic bottom which carries two electrodes 7a, 7b.
• the electrode 7a is welded to the bottom 6 and the electrode 7b crosses the bottom 6 and it is electrically insulated therefrom by an insulating sleeve 8
• a semiconductor wafer 9 is formed of an insulating substrate 10 based on undoped silicon which is bonded to the bottom 6.
• This wafer comprises a semiconductor bridge 11, for example made of doped silicon which is partially covered by two conductive pads 12a , 12b for example aluminum.
• the spacing between the pads is between 60 and 100 micrometers and preferably of the order of 80 micrometers.
• the stud 12b is connected to the electrode 7b by a connecting wire 13 fixed by welding.
• the stud 12a is connected to the electrode 7a via the metal bottom 6 through a semiconductor well 14 (doped silicon) which passes through the insulating substrate 10.
• a pyrotechnic ignition composition 15 covers the wafer 9 as well as the wire 13 and the welds. This composition is constituted for example by the association of
• Zirconiu and potassium perchlorate in conventional proportions of 60% by mass of zirconium for 40% by mass of perchlorate. It is initiated by the semiconductor bridge and it is intended to ignite the inflammatory composition 5.
• the average particle size of the composition 15 will be chosen to be of the same order of magnitude as the dimensions of the semiconductor bridge. Such an arrangement ensures thermal transfer by convection and / or projection during the rise in temperature of the semiconductor bridge. This ensures reliable initiation of the pyrotechnic composition by the resistive bridge.
• the bridge generally has dimensions of the order of 50 micrometers x 150 micrometers. We therefore adopt for the composition a particle size less than or equal to 50 micrometers.
• the bottom 6 is made integral with the case 4, for example by laser welding.
• the loading of the casing 2 is carried out in the following manner: The casing 4 is first loaded with the inflammatory composition 5 then with its ignition composition 15, a slight compression of the compositions is carried out.
• the bottom 6 is then positioned carrying the semiconductor wafer 9.
• the bottom 6 is welded to the case 4.
• This box 2 is placed inside an envelope 3 which is formed by the joining of two shells: a lower shell 16 and an upper shell 17.
• the two shells are produced by injection of a plastic material, for example of the polyamide or polycarbonate type. They are made integral with one another, for example by ultrasonic welding.
• the lower shell 16 is shown alone in FIGS. 2a and 2b. It has a support face 18 on which is made a circular groove 19 and it is crossed by two holes 20, 21 connected by a notch 22.
• the holes 20 and 21 are intended to allow the pins 7a and 7b of the housing 2 to pass.
• the notch 22 makes it possible to receive the curvatures of the pins 7a and 7b.
• the external profile of the lower shell 16 comprises two cylindrical surfaces 23, 24 connected to one another by a conical surface 25.
• the upper shell 17 is shown alone in FIG. 3. It has a bearing face 26 which carries a circular toothing 27 intended to cooperate with the groove 19 of the lower shell 16.
• the upper shell 17 defines an internal cylindrical volume 28 which is intended to receive the housing 2. This volume therefore has the same diameter as the external diameter of the housing 2 and it has a height equal to that of the housing.
• the external profile of the upper shell 17 comprises two cylindrical surfaces 29, 30 connected to each other by a conical surface 31.
• the thickness e of the upper shell is of the order of 0.5 mm. This shell is thin enough to be able to be broken by the initiation of composition 5.
• the mounting of the initiator according to the invention is carried out as follows.
• this housing is positioned on the lower shell 16 by making the pins 7a and 7b penetrate into the holes 20 and 21.
• the bottom 6 of the housing 2 is therefore supported on the face d 'support 18.
• the housing 2 is then capped with the upper shell 17.
• the two shells are then joined together by ultrasonic welding.
• Ultrasonic welding is carried out in a known manner by applying a sonotrode of a welding device to the conical profile 31 of the upper shell.
• the vibrations of the sonotrode cause the welding of the contacting surfaces.
• the circular toothing 27 enters the mounting in the groove 19 which allows to concentrate the stresses caused by ultrasonic vibrations during welding. We thus locate a heating at the level of the groove / toothing contact which allows the welding.
• the sealing of the initiator with respect to the outside is ensured by the laser welding of the housing 2. No particular precaution from the point of view of sealing is to be expected during the mounting of the casing 3. It is simplified thus manufacturing.
• the notch 22 can be replaced by a larger housing which can receive an electronic filtering component, for example a capacitor welded in parallel on the terminals 7a and 7b.
• an electronic filtering component for example a capacitor welded in parallel on the terminals 7a and 7b.
• Such an arrangement ensures protection against static electricity discharges (see in particular patent US5099762).
• initiators comprising more than two pins.
• One of the advantages of the initiator according to the invention is that its structure is simple and makes it possible to manufacture it at a lower cost for a given external geometry.
• the boxes 2 which contain the pyrotechnics can be produced on the one hand and the plastic envelopes produced elsewhere. It is therefore no longer necessary to carry out a plastic overmolding operation on a pyrotechnically active unit.
• Another advantage of the initiator according to the invention is that it is possible to produce initiators having various external dimensions at low cost.
• FIG. 4 shows the different stages of the method for mounting a pyrotechnic initiator according to the invention.
• pyrotechnic initiators having different external shapes and / or dimensions depending on the mounting interfaces of the safety systems to which they must be adapted (gas generators for protective cushion, belt tensioners, safety device weakening, for example, of automobile pedal boards, various pyromechanisms, etc.).
• an initiator box 2 is manufactured comprising a substantially cylindrical case extended by the two pins (step A).
• the shells are also made to define the desired envelope for the final initiator.
• step B we presented three different sets of shells (16a / 17a, 16b / 17b, 16c / 17c).
• the shells all have in common the delimitation of an identical internal volume 28a, 28b, 28c making it possible to receive the same housing 2.
• the housing can be adapted to any of the envelopes 3a, 3b or 3c.
• the housing is placed in the chosen envelope and the two shells of the housing are joined together to produce the desired initiator la, lb or le.
• the initiator will be personalized by adapting it to an envelope 3 having the external geometry desired by a customer.
• the most expensive element of the initiator (the pyrotechnic system) can therefore be manufactured in large quantities since it is only subsequently that it will be integrated into a particular envelope adapted to the customer's needs. This greatly reduces the production cost of pyrotechnic initiators.
• FIGS 5 and 6 show another embodiment of an initiator according to the invention.
• This initiator 1 also comprises a box 2 containing the pyrotechnic composition or compositions, a box which is arranged inside an envelope 3 formed by the joining of two shells 16 and 17.
• the housing 2 is not shown in section for clarity of the figure.
• This initiator differs from that according to FIG. 1 in that the pins 7a and 7b of the housing do not come out of the envelope 2.
• These pins are soldered on an electronic circuit which is here a printed circuit 32 which has a circular shape and is housed in a complementary bore 33 which is a counterbore arranged on the lower shell 16.
• the lower shell 16 carries holes which allow two connection electrodes 34a, 34b to pass through.
• the electrodes are also soldered to the printed circuit 32.
• the printed circuit 32 makes it possible to electrically connect the pins 7a and 7b to the connection electrodes 34a, 34b. It can advantageously carry electronic components which will perform various functions: protection against electromagnetic waves and / or electrostatic discharges, introduction of a logic function in particular of a coding of the initiator and of means allowing the comparison of this code with a coded signal for triggering firing (decoding), electric energy storage capacitor.
• FIG. 5 and 6 show a circuit 32 which carries a capacitor 35 which is mounted in parallel between pins 7a and 7b and which provides protection against electrostatic discharges (a value of the capacitor capacity will be chosen between 0.1 and 10 microfarads).
• the circuit shown also includes an integrated circuit 36 which receives the signals from the two electrodes 34a, 34b and which supplies the pin 7b only if a code corresponding to that of the initiator is transmitted by the connection electrodes.
• Such a logic circuit is well known to those skilled in the art and will not be described in more detail.
• the active or passive circuits used will preferably be surface mount components (CMS), this in order to limit the size of the circuit and reduce the cost of assembly.
• CMS surface mount components
• the casing 2 is produced on the one hand and the casing 3 formed by the two shells 16 and 17 on the other hand.
• the shells will be defined in such a way that they have an internal volume which can receive the housing 2 as well as the printed circuit. 32.
• the external profile of the shells will be adapted according to the specific needs of the client.
• the printed circuit 32 carrying the two electrodes 34a, 34b is also produced.
• the two shells 16 and 17 are joined together, for example by ultrasonic welding.
• sealing means such as O-rings disposed between the circuit 32 and the lower shell.
• FIG. 7 shows another embodiment of an initiator according to the invention.
• This mode also includes a box 2 (not shown in detail), which contains the pyrotechnic composition or compositions and which is disposed inside an envelope 3 formed by the joining of two shells 16 and 17.
• the pins 7a and 7b of the housing do not come out of the envelope 2, they are fixed to an electronic circuit 37 which is shown here with a cylindrical shape and which is housed in the internal volume 28 of the upper shell 17.
• This circuit is not shown in details and could be defined so as to ensure the functions described above (electrical protection, decoding of a firing signal, supply of electrical energy, etc.).
• the lower shell 16 carries holes which allow the two electrodes 34a, 34b to pass, which are also connected to the electronic circuit 37.
• the housing 2 is identical to that shown with reference to FIG. 5. It therefore suffices to manufacture an upper shell 17 having a suitable shape to receive both the housing 2 and the circuit 37.

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• Engineering & Computer Science (AREA)
• General Engineering & Computer Science (AREA)
• Computer Hardware Design (AREA)
• Microelectronics & Electronic Packaging (AREA)
• Manufacturing & Machinery (AREA)
• Air Bags (AREA)
• Feeding, Discharge, Calcimining, Fusing, And Gas-Generation Devices (AREA)

Applications Claiming Priority (3)

Publications (1)

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ID=9548294

Family Applications (1)

Country Status (4)

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Family Cites Families (13)

• 1999
  • 1999-07-19 FR FR9909382A patent/FR2796715B1/fr not_active Expired - Fee Related
• 2000
  • 2000-07-07 EP EP00949669A patent/EP1112470A1/de not_active Withdrawn
  • 2000-07-07 WO PCT/FR2000/001962 patent/WO2001006202A1/fr not_active Application Discontinuation
  • 2000-07-07 US US09/719,862 patent/US6526890B1/en not_active Expired - Fee Related

Non-Patent Citations (1)

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