To ensure the helmet lining retains its position and protection during an impact, the design of the connection structure begins with a mechanical interlocking mechanism, creating a secure physical lock between the helmet lining and the outer shell. The side of the helmet lining closest to the outer shell features a pre-designed protrusion or mortise-and-tenon structure, while the inner shell features a matching groove or slot. During assembly, the protrusions of the helmet lining precisely fit into the slots, fitting tightly together like a puzzle. This interlocking mechanism isn't uniformly distributed, but rather focuses on core impact-prone areas like the forehead and back of the head. This increases the density of interlocking points between the helmet lining and the outer shell, preventing lateral or vertical slippage in these critical areas even after an impact. The interlocking density is appropriately reduced in less critical areas, such as the sides of the head. This ensures stability while allowing for minimal deformation, ensuring a balanced fit and ensuring both comfort and protection.
The coordinated design of the energy-absorbing layer and the connection structure is crucial for enhancing the helmet lining's resistance to displacement. Helmet linings typically consist of multiple layers of cushioning materials (such as EPS and EPP foam) of varying densities. The connection method must be tailored to the energy-absorbing properties of these materials. Elastic connectors (such as flexible plastic clips or highly elastic fiber straps) are installed between the cushioning layer and the outer shell. These connectors securely fasten the helmet lining to the inner shell while simultaneously expanding and contracting with the compression deformation of the cushioning layer, preventing breakage or detachment due to the deformation of the cushioning layer. Furthermore, the distribution of the connectors aligns with the energy-absorbing zones of the helmet lining. This ensures that when the cushioning layer absorbs impact energy, each energy-absorbing point is supported by a connector, preventing localized shifting of the helmet lining due to uneven force distribution and maintaining its relative position to the outer shell.
A zoned locking mechanism allows the helmet lining's connection to be more tailored to the protection needs of different areas, preventing a single design from being unable to cope with complex impact scenarios. The helmet lining in the forehead area must not only resist displacement but also be adjustable with the headband. Therefore, a "rigid buckle + elastic strap" combination is employed. The rigid buckle ensures no significant displacement during impact, while the elastic strap allows for fine adjustment to accommodate different head shapes. The helmet lining in the lateral area of the head must conform to the contours of the ears. A combination of deformable Velcro and positioning posts is used for connection. The Velcro provides a flexible fit, while the positioning posts restrict lateral movement. At the back of the head, a critical area for impact protection, the edge of the helmet lining fully engages the circular grooves in the outer shell, creating a 360-degree wraparound fixation. Regardless of the direction of impact, the helmet lining at the back of the head remains firmly in place.
Material compatibility prevents environmental factors from damaging the connection between the helmet lining and the outer shell. Helmet linings are often made of lightweight foam or fabric composite materials, while the outer shell is often made of ABS or PC. The physical properties of these two materials differ significantly. Using rigid connections (such as metal screws) can easily lead to loosening after long-term use due to the different thermal expansion coefficients. Therefore, hot-melt adhesive, highly compatible with both materials, is used to facilitate mechanical connection. This adhesive fills the tiny gaps between the helmet lining and the outer shell, enhancing the fit. Its elasticity also allows it to withstand material deformation caused by temperature fluctuations. For helmets prone to sweating or humidity, a waterproof coating is added to the connection points to prevent moisture from penetrating and potentially causing adhesive failure or metal corrosion, ensuring a long-term, reliable connection between the helmet lining and the outer shell.
A dynamic anti-detachment mechanism can withstand the intense impact of a collision and prevent the helmet lining from becoming disengaged. Some connecting clips feature a barbed design that snaps into place during assembly. If a collision creates a tendency to separate, the barbs firmly engage the edge of the slot, preventing easy disengagement. A "secondary locking" mechanism is also added at key connection points between the helmet lining and the outer shell (such as the forehead and back of the head). When the stress on the primary connection reaches a threshold, the secondary locking pin automatically ejects and retracts into the positioning hole, creating a double fixation. Even if the primary connection becomes slightly loose, the secondary locking mechanism limits the helmet lining's movement, preventing it from leaving the protective area of the outer shell.
Assembly precision control is essential for ensuring a secure helmet lining connection, preventing partial connection failure due to installation deviation. During production, the helmet lining is pre-installed with precise positioning holes, and the outer shell is equipped with corresponding positioning posts. During assembly, the alignment of the positioning holes and posts ensures minimal deviation in the relative positioning of the helmet lining and the outer shell. In areas where Velcro fasteners are used, clear markings are placed on the helmet lining and outer shell to prevent manual assembly misalignment. After all connections are completed, the helmet lining is tested for displacement through simulated impact testing. If any area exhibits excessive displacement, the connection structure is adjusted or additional connection points are added until the protection standard is met.
The optimized detachable connection design facilitates maintenance of the helmet lining without sacrificing stability during impact. Many helmet liners need to be disassembled and cleaned regularly, so the connection method adopts a "quick release + precise positioning" combination - when disassembling, the helmet lining can be removed by pressing the buckle or tearing the Velcro. When installing, it can be quickly aligned through color markings and raised positioning points to ensure that the original fixed position is restored each time it is reinstalled, and there will be no connection deviation due to disassembly; for easily worn connectors (such as Velcro, elastic bands), they will be designed with a modular structure, and damaged parts can be replaced individually without replacing the helmet lining or shell as a whole. This not only reduces maintenance costs, but also maintains a stable connection between the helmet lining and the shell for a long time, avoiding the risk of displacement due to wear of the connectors.
