The advantages of Variable Expanded Metal filters:
- Reduced inflator open flame
- VEM technology prevents burning pyrotechnic particles from escaping the filter.
- Reduced inflator tank wash by up to 50%
- ACS is able to reduce the tank wash over a normal wire mesh filter by up to 50% using VEM technologies. This results in cleaner and safer airbag inflator.
- Reduced Airbag Cushion Damage
- Excess cushion and pin hole burns are typically the result of burning particles that escape a filter: a problem typical in traditional laminar flow filter technology but solved with ACS’s VEM technology.
- Adjustable for Specific Combustion & Performance Gates
- ACS engineers can quickly adjust the filter’s internal combustion pressure and the tank ballistic performance gates with minor filter changes to meet a customer’s acceptance gates, most often without major generate nor propellant load changes.
Pyrotechnic airbag inflator filters have historically been constructed from welded, knitted, or woven wire mesh. ACS was a frontrunner in the industry’s transition to woven wire mesh filters in the early 2000’s which resulted in cheaper filters inside safer airbags. A little over a decade later, ACS revolutionized the airbag inflator filter market again with the release of V.E.M. filters.
ACS’s patented variable expanded metal filters consist of a single sheet of expanded metal containing differing pore sizes, the production of which is digitally monitored for conformity. The disparity in pore sizes across the resulting sheet of expanded metal allows the piece to simply be rolled up to create a circular filter with greater tortuosity and effectiveness than that of wire mesh, but at over 35% less weight, a greatly reduced level of part complexity, and significantly reduced cost.
Inflators that fill the bag with pyrotechnics produce a burning jet fire. The jet fire is filled with copper and other molten metals that must be cooled and plated without exiting the inflator. If the filter has the same hole profile in all layers, then negative laminar gas flow is obtained, especially when the layers nest, creating direct flow paths for the burning jet fire particles to exit the inflator. Escaping flames can damage the airbag, and even injure the passenger. ACS’s VEM filters use flow profiles that reduce the open flame by capturing all the burning particles before they can exit the filter. The result is cooler exit gas temperatures, and a cleaner, safer gas filling the airbag cushion.
Adjustable for Specific Inflator Combustion & Tank Performance Gates
ACS believes that filters for airbags are not heat sinks nor are they coolants, which function using convection heat transfer. A fast Mach gas velocity deployment time of less than 40ms invalidates the heat sink concept, making normal convection heat transfer formulas non-relevant. ACS believes the filter’s cooling is thus not based upon convection cooling; inflator performance is solely based upon the principles of thermodynamic cooling.
Rather than a coolant or a heat sink, ACS thinks of airbag inflator filters as thermodynamic diffusers. With this classification in mind, an engineer can quickly adjust both the filter’s internal combustion pressures and the tank’s ballistic performance gates with minor modifications. In this way we can meet a customer’s acceptance gates, most often without major generate nor propellant load changes. When designing a filter as a thermodynamic diffuser instead of a heat sink, the filter can become a much better generate slag trap, which helps to reduce overall inflator cost.
Reduced Inflator Tank Wash
USCAR requires total tank wash particulate below one gram regardless of airbag type: driver, passenger, side impact, roll over curtain, far side, etc. A varied pore profile on each layer of a VEM filter effectively reduces tank wash and allows for a lighter, smaller inflator. ACS is able to reduce the tank wash over a normal wire mesh filter or a standard expanded metal filter by up to 50% using VEM technologies. This results in a cleaner and safer airbag inflator.
Prototyping
ACS has a world class prototype filter department and software modeling technology to quickly help you design and alter the filter to meet your customers’ requirements and save development costs and reduce inflator cost as new inflator development takes time and costs are high. Please ask us about anything airbag filter related and we can help.
