Solid Propellant Compacts With Recesses For Rapid Ignition
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Solution Overview
Problem
Existing solid propellant pellets for inflators have a limited surface-to-volume ratio, leading to variable performance and inefficient ignition, as well as undefined surface structures in granulated forms which further complicate consistent operation.
Innovation Solution
The development of solid propellant compacts with defined recesses on their surfaces, increasing the surface-to-volume ratio, allowing for rapid ignition and burning, and featuring a consistent performance by optimizing the geometry of the recesses to enhance mechanical stability and ease of molding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If solid propellant pellets are used in traditional cylindrical shape, then the structure is simple and easy to manufacture, but the surface-to-volume ratio is limited which reduces ignition speed and gas generation efficiency
Solution Approach 1:
The propellant compact is segmented by creating recesses (dimples) on its surface, dividing the originally smooth cylindrical surface into multiple elevated and recessed regions. This segmentation increases the total surface area available for ignition without fundamentally changing the cylindrical form factor, thereby improving ignition speed while maintaining manufacturing simplicity
Solution Approach 2:
The invention adds a third dimension to the propellant surface by creating depth in the recesses. Instead of merely expanding the surface area in two dimensions (making the pellet larger), the recesses utilize the depth dimension to create additional surface area within the same volume constraints, effectively increasing the surface-to-volume ratio without proportionally increasing the compact's external dimensions
2Reliability
If granulated solid propellant is used, then the surface-to-volume ratio can be increased, but the surface structure becomes undefined leading to performance variation
Solution Approach 1:
Instead of using uniformly small granules (which would define surface structure uniformly), the invention applies local quality by creating specific recesses at particular locations on the propellant compact. Each recess has a defined geometry and position, creating localized high-surface-area regions that ensure consistent ignition characteristics while maintaining overall structural integrity
Solution Approach 2:
The invention changes the geometric parameters of the propellant compact by introducing recesses with specific dimensions (depth, diameter, spacing). These controlled parameter changes create a defined surface structure that increases surface area while ensuring repeatability and consistency in ignition performance, unlike the random structure of granulated propellant
3Quantity of substance
If the recess depth is increased to maximize surface area, then the surface-to-volume ratio increases, but the mechanical stability of the compact decreases
Solution Approach 1:
The invention applies partial action by creating recesses that extend only to a specific depth (between 20-80% of the radius) rather than completely through the propellant compact. This partial penetration into the propellant mass provides sufficient surface area increase for rapid ignition while leaving enough material depth to maintain structural integrity and mechanical stability
Solution Approach 2:
The propellant compact with recesses creates a composite-like structure with elevated regions and recessed regions. This structural composition allows the compact to exhibit both high surface area (from the recessed regions) and high mechanical strength (from the elevated regions that provide structural support), effectively combining properties that would otherwise be mutually exclusive
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solid propellant compacts with increased surface-to-volume ratios enable rapid and consistent gas generation, reducing performance variation in inflators and actuators, achieving a short onset and high initial gas production.
Implementation Method 1
solid propellant in the form of a compact made of powered and/or granulated solid propellant, especially for inflators and/or pyrotechnical drive units
Data Source
AI summary
A solid propellant compact (10) in the form of a compact made of a powdered and/or granulated solid propellant, especially for inflators and/or actuators of a vehicle occupant restraint system, includes at least one recess on at least one of its sides. Solid propellant compacts (10) of this type are provided in an inflator (14) comprising at least one combustion chamber. A module includes such inflator (14) with an airbag inflatable by the inflator (14). A pyrotechnical drive unit (30) comprising a housing (32), a piston (34) movable in the housing (32) includes solid propellant compacts (10) of this type.