Vehicle Seat Headrest Dual-Latch Locking for HDPE Impact Robustness
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing motor vehicle seat headrests using high mechanical performance plastics are costly, and there is a need for a robust locking mechanism that can ensure passenger safety even with lower mechanical performance materials like high density polyethylene (HDPE).
Innovation Solution
A motor vehicle seat headrest design featuring a crosspiece with an actuating rack, upper and lower latches actuated by a spring, and a pinion with eccentrics that bring the latches closer to unlock, providing robust locking and unlocking functionality, ensuring the secondary body remains locked during rearward impacts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high-performance mechanical plastic materials are used to produce the main and secondary bodies, then robust locking is ensured in the event of impact, but the cost increases significantly
Solution Approach 1:
The patent replaces expensive high-performance plastic materials with cheaper high-density polyethylene (HDPE) material. The cost reduction is achieved by using a more economical material that can still provide adequate locking robustness when combined with the improved mechanical locking mechanism featuring two latches and spring means.
Solution Approach 2:
The patent employs a composite approach by combining HDPE material with enhanced mechanical locking components (two latches, spring means, pinion). This composite solution achieves the required robustness through the combination of material and mechanical design rather than relying solely on expensive high-performance plastic.
2Reliability
If a single latch is used for locking the secondary body, then the device complexity is reduced, but the locking robustness during rearward impact is insufficient
Solution Approach 1:
The patent divides the locking function into two separate latches (first latch and second latch) that operate independently but cooperatively. Each latch engages with its own locking rack on the secondary body, providing redundant locking that enhances robustness during rearward impact while maintaining manageable complexity through modular design.
Solution Approach 2:
The patent incorporates spring means that pre-load the latches into the locked position, creating a cushioning effect that ensures the latches remain firmly engaged during rearward impact. The spring means absorb and counteract impact forces, maintaining locking reliability without requiring an overly complex active control system.
3Reliability
If the latches are actuated apart from each other by spring means, then the locking robustness is improved, but the mechanism complexity increases
Solution Approach 1:
The pinion serves multiple functions: it acts as the primary actuating mechanism for both latches simultaneously, provides the unlocking action when rotated, and transmits force through the rack-pinion engagement. This multi-functional design reduces overall mechanism complexity while achieving coordinated latch actuation.
Solution Approach 2:
The patent employs cam surfaces with curved geometries that work in conjunction with the eccentrics on the pinion. The curved cam surfaces transform the rotational motion of the pinion into the linear motion required to actuate both latches, providing a compact and elegant solution that reduces mechanical complexity compared to direct linear actuation mechanisms.
4Ease of manufacture
If HDPE material is used instead of high-performance plastic, then the cost is reduced, but the mechanical performance is poorer
Solution Approach 1:
The patent changes the material parameter from high-performance plastic to HDPE, accepting the reduction in inherent material strength. This parameter change is compensated by enhancing the mechanical locking mechanism design, specifically through the two-latch system with spring pre-loading, which provides the additional strength needed to achieve equivalent overall performance.
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 design ensures a robust locking of the secondary body in its adjustment position during rearward impacts, optimizing ergonomics and reducing costs by using HDPE, while maintaining safety and ease of adjustment.
Implementation Method 1
said latches being actuated apart from each other by a second spring means interposed between them to place them in a locking position
Implementation Method 2
said pinion being provided with a first and a second eccentric, the unlocking actuation of said crosspiece causes said eccentrics to press against two respective cam surfaces provided on each of said latches so as to bring said latches closer to each other
Data Source
Figure 1a~1b
Figure 2a~2b
Figure 3a~3b
AI summary
The invention relates to a motor vehicle seat headrest (1) comprising a first locking device for a main body, a second locking device for a secondary body (4) and a common unlocking crossbar (7) for said devices provided with an actuating rack (30), said second locking device comprising a first upper latch (5a) and a second lower latch (5b) cooperating respectively with a first (6a) and a second (6b) locking rack, a pinion (31) meshing with said actuating rack, said pinion being provided with a first (32a) and a second eccentric, the unlocking actuation of said crossbar brings said eccentrics into contact with two respective cam surfaces provided on each of said latches so as to bring said latches closer together to put them in the unlocking position.