Tilting Vehicle Seat Backrest With Sacrificial Shock Absorption
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Solution Overview
Problem
Existing aircraft seat backrests that absorb shock during accidents are bulky and restrictive, making their incorporation into seats problematic.
Innovation Solution
A seat design with a backrest that tilts forward during impact, utilizing a sacrificial mechanical link and pivot links with brakes and stops to absorb shock, allowing adjustable absorption levels without significant weight or size increase.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a spring is incorporated into the seat to ensure progressive slow down of the backrest during impact, then shock absorption is improved, but the weight and overall dimension of the seat increase significantly
Solution Approach 1:
The shock absorption function is segmented between multiple components: the sacrificial mechanical link (absorbing initial impact energy through controlled failure), the pivot links with brakes (providing progressive damping during backrest tilting), and the stop systems (limiting rotation amplitude). This segmentation allows each component to be optimized for its specific function while collectively achieving effective shock absorption with reduced overall weight compared to a single large spring system.
Solution Approach 2:
The sacrificial mechanical link is designed as a disposable component that absorbs a portion of the impact energy through controlled failure during the accident. This allows the system to use a lighter, non-reusable component for the high-energy initial absorption phase, rather than requiring a heavy, durable spring system to handle the entire shock absorption burden.
2Reliability
If the backrest is designed to tilt forward during impact to absorb shock, then shock absorption is improved, but the device complexity increases due to additional fastening mechanisms
Solution Approach 1:
The fastening mechanism merges multiple functions into integrated components: the link rod simultaneously provides structural support, enables controlled tilting motion through pivot links, and incorporates braking systems for shock absorption. The sacrificial mechanical link is positioned opposite the link rod to create a balanced, symmetric structure that simplifies the overall fastening assembly while achieving complex shock absorption behavior.
Solution Approach 2:
The link rod serves multiple functions: it connects the lower and upper frames, enables the backrest tilting motion, incorporates pivot links with brakes for progressive damping, and works with the sacrificial mechanical link to provide both initial impact absorption and controlled deceleration. This multi-functionality reduces the number of separate components needed, thereby reducing overall device complexity.
3Ease of operation
If the backrest is made stable and easy to reposition after impact, then ease of operation is improved, but the shock absorption mechanism becomes more complex
Solution Approach 1:
The fastening mechanism transitions from a static rigid connection to a dynamic system that adapts its behavior based on applied forces. During normal use, the pivot links with brakes provide stable support. During impact, the sacrificial link fails and the brakes engage to provide progressive damping. After impact, the stop systems allow easy manual repositioning by overcoming the brake friction with reasonable force, while preventing spontaneous tilting under moderate forces. This dynamic behavior achieves both ease of operation and effective shock absorption without requiring overly complex mechanisms.
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
Effectively reduces shock intensity by absorbing impact energy through a tilting backrest, with adjustable absorption levels and minimal space requirements, facilitating easy repositioning post-impact for passenger evacuation.
Implementation Method 1
each pivot link having a rotation brake and/or a system of stops limiting its rotation amplitude
Implementation Method 2
a sacrificial mechanical link that connects the lower frame to the upper frame while being located opposite the link rod
Data Source
AI summary
A seat intended to be fixed to the floor of a vehicle includes a seat part incorporating a lower frame, and a backrest incorporating an upper frame secured to the lower frame by at least one fastener that allows the backrest to tilt in the event of an impact, by rotation about a transverse axis. The fastener includes a link rod having a first end connected to the lower frame by a first pivot link of axis parallel to the transverse axis, and having a second end connected to the upper frame by way of a second pivot link of axis parallel to the transverse axis. Each pivot link has a rotation brake and/or a system of stops limiting its rotation amplitude. A sacrificial mechanical link connects the lower frame to the upper frame while being situated next to the link rod.