Dual-Layer Foam Cranial Protection Cell for Rotational Injury

The impact absorbing means is divided into multiple foam layers with different densities and mechanical properties. The first foam layer has higher density and rigidity to resist initial impact forces, while the second foam layer has lower density and higher compliance to absorb residual energy and reduce angular acceleration. This segmentation allows each layer to perform its specific function in the impact sequence.

The invention uses composite foam structures combining different materials with complementary properties. The first foam layer uses higher density material (e.g., expanded polystyrene or polyurethane foam with density 30-80 kg/m³) for initial impact resistance, while the second foam layer uses lower density material (e.g., expanded polystyrene or polyurethane foam with density 10-30 kg/m³) for energy absorption and torque reduction. This composite approach creates a gradient that effectively manages impact forces.

Different regions of the helmet have different foam layer configurations optimized for local impact characteristics. The frontal and lateral regions use thicker first foam layers for high-impact areas, while the rear and occipital regions use thinner configurations. The second foam layer is strategically positioned to provide torque absorption where needed most, creating a non-uniform distribution that optimizes protection-to-weight ratio.

The use of composite foam layers with different densities allows efficient energy absorption without requiring uniform thick coverage. The higher density first layer provides structural integrity and initial energy absorption, while the lower density second layer provides compliant energy dissipation. This composite structure achieves superior energy absorption per unit volume and weight compared to single-layer alternatives.

The multi-layer foam structure serves as an intermediary between the rigid shell and the skull. The first foam layer acts as a primary mediator to resist direct impact forces transmitted to the skull, while the second foam layer acts as a secondary mediator to absorb rotational forces and reduce torque on the brain. This intermediary structure decouples the protective function of the rigid shell from the harmful transmission of rotational forces.

The composite foam structure combines materials with different mechanical properties to create a gradient that transitions from rigid (first layer) to compliant (second layer). This composite construction allows the shell's rigidity to provide skull protection while the foam layers progressively absorb and dissipate rotational forces before they reach the brain, preventing diffuse axonal injury.

The impact absorption function is segmented across two foam layers with different density characteristics. The first foam layer uses higher density material (30-80 kg/m³) to provide structural support and initial impact resistance, contributing more to weight but also more to energy absorption. The second foam layer uses lower density material (10-30 kg/m³) to provide compliant energy dissipation with less weight contribution. This segmentation allows optimized weight-to-protection ratio.

The composite foam construction combines higher density and lower density materials in a coordinated arrangement where each material contributes its strengths. The higher density first layer provides rigidity and initial energy absorption, while the lower density second layer provides weight efficiency and compliant energy dissipation. Together they achieve superior impact absorption per unit weight compared to using single-density foam throughout.