Helmet Cushion Shear Force Management via Liquid Bladder
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Solution Overview
Problem
Conventional helmets are ineffective in managing rotational and shear forces, leading to increased risk of injuries such as concussions and subdural hematomas, due to added weight and moment of inertia from solutions that permit independent rotation of the helmet shell.
Innovation Solution
A helmet design featuring an energy-absorbing layer with a liquid-filled bladder and a compressible pad that absorbs and expels liquid upon impact, creating a slip plane to decouple shear forces and allow rotational freedom, while maintaining comfort and stability during normal use.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If conventional solutions provide a slippery surface material or low friction layer to permit independent rotation of the helmet shell, then rotational forces are managed, but the helmet weight increases and moment of inertia increases, causing fatigue
Solution Approach 1:
The patent uses a liquid-filled bladder as the core mechanism. The bladder is filled with liquid that can move freely within it, creating internal fluid dynamics that allow the bladder to deform and rotate in response to external forces. This hydraulic approach replaces traditional mechanical friction-based solutions, achieving rotational force management through fluid movement rather than solid-on-solid friction, thereby reducing weight and moment of inertia.
Solution Approach 2:
The patent employs materials with shear-thickening properties that change their physical parameters based on applied stress. During normal use, the material remains soft and flexible, but upon impact, it transitions to a stiffer state. This dynamic parameter change allows the system to provide rotational freedom during normal wear while offering protection during impact, without requiring constant heavy structural reinforcement.
2Object-affected harmful factors
If conventional solutions use gel, liquid or soft material layers between shell and liner to allow rotation, then rotational forces are managed, but device complexity increases
Solution Approach 1:
The patent combines multiple functions into a single integrated component - the liquid-filled bladder. This single element simultaneously provides: (1) a slip plane for rotational freedom, (2) shear force management through liquid movement, (3) impact absorption through compression, and (4) a mechanism for dissipating rotational energy. By merging these functions into one component rather than using separate layers for each function, the patent reduces overall device complexity.
Solution Approach 2:
The liquid-filled bladder serves multiple purposes within the helmet system. It acts as both a cushioning element and a rotational freedom mechanism, and also functions as an impact absorber. The liquid inside provides both shear management during rotation and compression resistance during direct impact. This multi-functionality eliminates the need for separate specialized components for each protective function.
3Strength
If conventional helmets are designed to manage linear forces, then linear impact protection is improved, but effectiveness against shear or rotational forces decreases
Solution Approach 1:
The patent introduces dynamic elements into the helmet design - specifically the liquid-filled bladder that can move and deform in response to applied forces. During linear impact, the bladder compresses and the liquid moves to absorb energy. During rotational impact, the bladder can rotate and deform asymmetrically, allowing the liquid to move in patterns that dissipate rotational energy. This dynamic response capability enables the same structure to effectively manage both linear and rotational forces, unlike static conventional designs.
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 solution effectively attenuates rotational and shear forces, reducing the risk of head injuries by allowing the helmet to rotate relative to the head upon impact, while maintaining comfort and reducing weight compared to conventional designs.
Implementation Method 1
The pad has pores or other interstices that are open to the exterior of the pad (such as open cell foam) to permit the liquid to be secreted and absorbed by the pad when the pad is compressed and decompressed
Implementation Method 2
The presence of free-flowing liquid within the bladder when compressed permits opposing surfaces of the bladder to be displaced in a shearing motion relative to each other, effectively permitting the bladder to 'roll'
Implementation Method 3
The liner usually comprises a compressible material that absorbs impact energy by distorting and absorbing the impact using the resilient and/or compressible properties of the material or by crushing and absorbing energy by material fracture
Data Source
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AI summary
The present disclosure relates to a cushion for use in a helmet comprising an outer shell for impact with an incoming force, the cushion disposed between the outer shell and a head when the helmet is worn, the cushion comprising: a sealed bladder comprising a flexible membrane; a pad housed within the bladder, said pad comprising a compressible member having interstices open to the exterior of the pad; and a liquid within the interior of the bladder; wherein said pad absorbs at least some of said liquid when uncompressed and expels said liquid when compressed; and wherein the volume of liquid within the bladder is sufficient to allow opposing surfaces of the bladder to be displaced in a shearing motion relative to each other when the cushion is compressed and subjected to shear forces, to decouple shear forces between said helmet and the head.