Lightweight Foldable Patient Litter Truss Structure
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Solution Overview
Problem
Current patient litter technologies are heavy due to frame structures that distribute loads through bending, leading to stress concentrations and increased weight, and fail under high accelerations during transport.
Innovation Solution
A lightweight truss structure that supports loads through compression and tension, using flexible materials and co-locating litter-to-vehicle and litter-to-patient restraints for direct load transfer, reducing material mass and weight.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If frame structures are used to support patient weight, then the litter can be manufactured with simple bending components, but the overall litter weight increases due to stress concentrations requiring additional structural material
Solution Approach 1:
The patent changes the fundamental loading parameter from bending to axial compression/tension. By redesigning the litter as a truss structure where members carry only axial loads, the components can be made lighter while maintaining strength, directly resolving the contradiction between manufacturing simplicity and weight reduction.
Solution Approach 2:
The patent employs composite construction combining rigid compression members (aluminum or composite tubes) with flexible tension members (webbing or straps). This composite approach allows each material to operate in its optimal stress regime, achieving weight reduction while maintaining manufacturability through modular assembly.
2Strength
If frame structures with bending loads are used, then the litter can support patient weight, but the structure fails under high accelerations during vehicle transport
Solution Approach 1:
The patent fundamentally changes the stress state parameter from bending to axial compression and tension. Truss members subjected to axial loads can efficiently withstand high acceleration forces without the stress concentrations that cause frame structures to fail, simultaneously improving both strength and reliability under dynamic conditions.
Solution Approach 2:
The patent segments the litter structure into discrete truss members that can independently carry axial loads. This segmentation allows each member to be optimized for its specific loading condition, with compression members providing rigid support and tension members providing flexible restraint, enhancing overall reliability during high-acceleration events.
3Device complexity
If traditional litter-to-vehicle and litter-to-patient restraint interfaces are located separately, then the litter can be designed with simple restraint attachment, but substantial loads are transferred through the litter structure increasing system mass
Solution Approach 1:
The patent merges the litter-to-vehicle and litter-to-patient restraint interfaces by co-locating their attachment points on the litter structure. This merging allows direct load transfer from patient to vehicle restraints without routing forces through the litter's structural members, eliminating the need for additional mass to handle these loads and simplifying the overall restraint system.
Data Source
AI summary
A lightweight flexible patient litter includes, in one example, spaced compression longerons each foldable at spaced legs, a bed between the compression longerons, and a longitudinal truss structure on each side of the litter each including a longeron, its spaced legs, and one or more flexible tension members connected thereto. One or more lateral truss structures may each include opposing legs on each side of the litter and one or more flexible tension members connected thereto. A bed truss structure may include one or more tension members.