AU3315099A - Priming composition and igniter containing the same - Google Patents

Description

S F Ref: 466880

AUSTRALIA

PATENTS ACT 1990 COMPLETE SPECIFICATION FOR A STANDARD PATENT

ORIGINAL

Name and Address of Applicant: Actual Inventor(s): Address for Service: Invention Title: Chung Shan Institute of Science Technology No.2, Chung Shan Road Chia An Village Lungtan Taoyuan

TAIWAN

Long-Ming Tsai Spruson Ferguson, Patent Attorneys Level 33 St Martins Tower, 31 Market Street Sydney, New South Wales, 2000, Australia Priming Composition and Igniter Containing the Same The following statement is a full description of this invention, including the best method of performing it known to me/us:- 5845 PRIMING COMPOSITION AND IGNITER CONTAINING THE SAME BACKGROUND OF THE INVENTION The present invention relates to a priming composition, and more specifically to a priming composition which is used in the electricallyinitiated igniter for the inflator of the airbag system and the pretensioner of a motor vehicle.

Igniters with high quality for military or civilian use are in great need nowadays. Taking the airbag system or the pretensioner of vehicles 10 for example, when the vehicle crashes, the impact sensor outputs a signal to the electronic control unit, causing the electronic control unit to provide ignition current to the igniter. Upon receipt of ignition current, the igniter immediately ignites the gas generating agent, causing the air bag to be inflated within 20-50 milli-seconds. When the air bag is inflated, the cover is broken out suddenly, and therefore the car driver is protected.

On the other hand, the ignition currents will activate the igniter of the pretensioner to retract the seat belt for 8 to 15 centimeters automatically, .within 12 milli-seconds. Therefore in a crash, the displacements of the driver and/or passengers toward the front are reduced by the system. The life of the driver and/or passengers are protected adequately by the system.

The igniter of the air bag system is required to produce a pressure of about 40-80 Bar within 2 milli-seconds, so that the gas generating agent can be ignited to deploy the air bag instantaneously. The basic requirement of the responsetime to trigger the pretensioner is less than 2milli-seconds, the whole action to retract the seat belt is also required to complete within around 12 milli-seconds. Thus, the time delay for the ignition is very important. The shorter the ignition time delay is, the earlier the action to retract the seat belt starts, and, of course, the better protection for passengers results. Generally speaking, for known igniters, ignition time delay decreases as temperature rises. Drawbacks like longer ignition time delay for lower temperatures can also be found for known igniters.

If the igniter fails, the air bag system is unable to function, and the driver may be injured seriously or killed when a collision occurs. If the igniter is excessively sensitive, the air bag may be caused to deploy by an erroneous signal. Therefore, the reliability of the igniter is critical.

10 Various igniters for vehicle air bag systems have been disclosed.

Exemplars are seen in US Pat. Nos. 4,208,967; 5,230,287.

SUMMARY OF THE INVENTION The present invention has been accomplished under the circumstances in view. It is one object of the present invention to provide a priming composition to be used in an igniter for vehicle air bag inflators which is highly anti-electrostatic, makes the ignition delay shorter and weather proof. It is another object of the present invention to provide a highly-reliable priming composition which can be used in an igniter.

The present invention provides a priming composition which can be used in an igniter for a vehicle air bag inflator and pretensioner.

One aspect of the present invention relates to a priming composition which comprises Zirconium (Zr) 40% to 55% by weight; lead styphnate (NLS) 10% to 25% by weight; and potassium perchlorate (KC104) 25% to 40% by weight.

A particularly preferred embodiment of the composition which comprises Zirconium (Zr) 45% to 50% by weight; lead styphnate (NLS) 15% to 20% by weight; and potassium perchlorate (KC 104) to 35% by weight. The composition of the present invention can be further comprised of a component Kelf-800 resin 1% to 8% by weight.

The Kelf-800 resin can be bought from the market.

The priming composition of the present invention can be used in an igniter. The igniter comprises a stainless steel casing, an O-ring, an ignition unit, a pyrotechnic powder holder and a stainless steel shell. The ignition unit is mounted in the receiving chamber within said stainless steel casing. The ignition unit comprises a pair of electrodes (gold plated steel 10 electrodes), a nickel chrome wire connected between said electrodes at one and an electrically insulative packing block fastened to said electrodes to fix said electrodes in place and to insulate said electrodes from each other. The ignition mixture holder is covered on said ignition unit and holds a high burning rate pyrotechnic powder. The stainless steel shell is mounted around the periphery of said pyrotechnic powder holder.

The priming composition of the present invention is fixedly fastened to the nickel chrome wire of the ignition unit.

e The igniter is operated when an ignition current is applied to a nickel chrome wire, which is connected between two electrodes at one end, causing a high temperature to be produced to initiate the priming composition being fastened to the nickel chrome wire, and therefore a high burning rate ignition mixture which surrounds the priming composition is ignited. The design of the igniter achieves high safety and high reliability.

Pressure built-up time and ignition time delay as well as environmental effects such as high and low temperature have been taken into account during the design of the igniter.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a sectional view of the igniter of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to Figures 1, an igniter for vehicle air bag inflator in accordance with the present invention is generally comprised of a stainless steel casing 10, an ignition unit 20, a pyrotechnic powder holder 30, and a stainless steel shell 40. The O-ring 11 mounted on said stainless steel casing 10, and used for sealing as bound to the air bag inflator module (not 10 shown in figure 1).

The ignition unit 20 comprises a pair of electrodes 21, a nickel :..chrome wire 22 having resistance about 2.0 ohms, and an insulating packing block 23. The pyrotechnic powder holder 30 is covered on the top of ignition unit 20, and filled with a high burning rate ignition mixture 50. Scoring lines 31 are provided on the pyrotechnic powder holder 30 at which the pyrotechnic powder holder 30 can easily be broken. The stainless steel shell 40 is mounted around the pyrotechnic powder holder The priming composition 60 is fixedly fastened to the nickel chrome wire 22 in the ignition mixture 50. When ignition current is guided to the nickel chrome wire 22, the priming composition 60 is immediately initiated, thereby causing the ignition mixture 50 to burn.

The priming composition of this invention can be used in the igniter to make the ignition time delay shorter than 1 millisecond and not be affected within -40°C Both the air bag inflator and the pretensioner of vehicles have standard short-circuit rings and electric power connectors. The igniters of the present invention could match with them well.

The priming composition of the present invention comprises (a) Zirconium (Zr) 40% to 55% by weight; lead styphnate (NLS) 10% to by weight; and potassium perchlorate (KCIO 4 25% to 40% by weight.

More detailed examples are used to illustrate the present invention, and these examples are used to explain the present invention. The examples below, which are given simply by way of illustration, must not be taken to limit the scope of the invention.

10 In these examples, parts is counted as weight, temperature is Celsius "C.

0 0 Example 1 (priming composition) 50 part of zirconium 16 parts of styphnate (NLS) and 34 15 parts of potassium perchlorate (KC10 4 were mixed together to form a priming composition, homogeneous dry powders.

Example 2 (priming composition) part of Zirconium 20 parts of styphnate (NLS) and parts of potassium perchlorate (KCIO 4 were mixed together to form a priming composition, homogeneous dry powders.

Example 3 (priming composition) part of Zirconium 20 parts of styphnate (NLS) and parts of potassium perchlorate (KC104) were mixed together to form a priming composition, homogeneous dry powders.

Example 4 (priming composition) 48 part of Zirconium 19 parts of styphnate (NLS) and 33 parts of potassium perchlorate (KCO10 4 were mixed together to form a priming composition, homogeneous dry powders.

Example. 5 (squibs) The priming composition of the example 1 was added to a diluted Kelf-800 resin liquid in a vessel and stirred fully to form a completely homogeneous paste. The paste was then coated on the wire and the oo*.

electrode surface of the ignition unit by a brush. Then the paste with wire and electrodes were put into an oven to heat for 4 hours at a temperature range between 40'C and 50'C. After cooling down, the paste was coated again with same procedures to form a droplet shape and then dried out at a temperature range between 60°C and 63°C for more than 24 hours. The 0 15 paste was cooled down and coated with lacquer on its surface.

Example 6 to 8 (squibs) Same procedures of example 5 were repeated to make squibs, but the priming composition of example 1 was replaced by the priming composition of example 2 to 4, respectively. Several squibs with different priming compositions were obtained.

Test method: 100 milli-gram of ignition mixture 50 comprising 52% of zirconium 42% of potassium perchlorate (KC 104) and 6% of binder were combined with squibs of example 5 to 8, respectively, to form electric igniters. After the electric igniters were made, the performance test below of electric igniters was completed.

Electric sensitivity test: Bruceton methods were used to check the electric sensitivity. All-fire current and no- fire current were calculated through statistical methods according to original test data.

Internal ballistic performance test: electric igniter was activated by 1.4A/3ms of electric current pulses at room temperature, high temperature and low temperature (-40 0 C) ,respectively. The pressure inside the 10 c.c. test chamber was also recorded. The S. graph of pressure vs. time was plotted. The peak pressure and time 10 delay could be read out.

Electrostatic safety test: Follow the guideline of the test in United States Military rules of MIL-STD-1512, Method 205.

Insulating resistance test: Follow the guideline of the test in United States Military rules of MIL-STD- 1512, Method 117.

**Test results: The igniters of example 5 to 8 can satisfy the conditions below. The results mean that the priming compositions of the present invention could greatly improve the properties of electric igniters 1. All-fire current: 0.8A/3ms.

2. No-fire current: 0.2A/10sec or 0.28A/3ms.

3. Post-fire resistance: >100KQ.

4. Ignition time delay: <lms (in 10c.c. test chamber).

Peak pressure: 55 10 bar (in 10c.c. test chamber).

6. Working temperature range:-40°C to +85 0

C.

7. Temperature effect: None (in the range of temperature between to 85 0

C).

8. Electrostatic safety: Pass the 25 KV electrostatic discharge.

9. Insulating resistance: >100KQ/500VDC.

While only one embodiment of the present invention has been shown and described, it will be understood that various modifications and changes could be made thereunto without departing from the spirit and scope of the invention disclosed.

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Claims (8)

1. A priming composition comprising: Zirconium (Zr) 40% to 55% by weight; lead styphnate (NLS) 10% to 25% by weight; and potassium perchlorate (KC 104) 25% to 40% by weight.

2. The composition of claim 1 comprising component (a) Zirconium (Zr) 45% to 50% by weight, component lead styphnate (NLS) 15% to 20% by weight and component potassium perchlorate 10 (KC10 4 30% to 35% by weight. Kelf-800 1% to 8% by weight.

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4. The composition of claim 1 which is used in an igniter.

The composition of claim 4 wherein said igniter comprising: a stainless steel casing defining a receiving chamber; nickel chrome wire connected between said electrodes at one end, and an electrically insulative packing block fastened to said electrodes to fix said electrodes in place and to insulate said electrodes from each other; a pyrotechnic powder holder covered on said ignition unit and holding a high burning rate ignition mixture; and a stainless steel shell mounted around the periphery of said pyrotechnic powder holder.

6. The composition of claim 5 wherein said pyrotechnic powder holder has at least one scoring line.

7. The composition of claim 5 wherein said priming composition is fixedly fastened to the nickel chrome wire of ignition unit.

8. A priming composition, substantially as hereinbefore described with reference to any one of the examples. Dated 3 June, 1999 Chung Shan Institute of Science Technology Patent Attorneys for the Applicant/Nominated Person SPRUSON FERGUSON S*30 S 0 0 555 eo SSSS [N:/libc]00383:bav