Vehicle Headrest Parallelogram Linkage for Adjustable Load Support
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Solution Overview
Problem
Existing motor-vehicle headrests lack the ability to adjust the head contact part to different positions effectively, fail to withstand high forces applied by the seat occupant, and are not easily manufactured or compact in design.
Innovation Solution
A motor-vehicle headrest featuring a base fixed to a post with a cushion support forming a parallelogrammatic linkage, including upper and lower links and a rigid brace, which allows for adjustable positioning and force compensation to prevent deformation and overload, along with a latch mechanism for secure positioning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a traditional headrest design with pivoted levers and catch mechanism is used, then the head contact part can be adjusted to different positions, but the structure becomes complex and difficult to manufacture
Solution Approach 1:
The headrest is divided into functionally independent segments: the base (14) fixed to the post, the parallelogrammatic linkage (16a, 16b, 17, 23a, 23b) for positioning, and the latch mechanism (29) for securing. This segmentation allows each component to perform its specific function with simple geometry, reducing overall structural complexity while maintaining adjustability.
Solution Approach 2:
The parallelogrammatic linkage serves multiple functions simultaneously: it enables the head contact part to be adjusted to different positions, maintains parallel motion for comfort, and provides structural stability. This multi-functionality eliminates the need for separate adjustment mechanisms, reducing device complexity.
2Ease of manufacture
If a compact and lightweight design is pursued, then manufacturing cost is reduced, but the headrest may lack the strength to withstand high forces from the seat occupant
Solution Approach 1:
The headrest utilizes a composite structure combining metal components (base, links, latch) with a foam cushion. The metal parts provide high strength-to-weight ratio and force withstanding capability, while the foam cushion provides comfort and reduces overall weight. This composite approach allows compact, cost-effective manufacturing without sacrificing strength.
Solution Approach 2:
The heavy cushion body is separated from the structural framework. The base and linkage are designed as lightweight metal structures that only provide structural support and positioning, while the cushion is a separate replaceable component. This extraction allows the structural parts to be minimized for cost and weight reduction while maintaining sufficient strength through optimal structural design.
3Strength
If the head contact part is made rigid to withstand high forces, then strength is improved, but the ability to adjust to different positions is reduced
Solution Approach 1:
The headrest employs a dynamic parallelogrammatic linkage that allows the head contact part to move between different positions while maintaining rigidity during use. The linkage transitions from a movable adjustment state to a locked stable state when the latch engages, providing both adjustability and force withstanding capability.
Solution Approach 2:
The latch mechanism acts as an intermediary between the adjustable linkage and the rigid head contact surface. It locks the linkage in position, transferring the rigidity requirement from the entire mechanism to just the locked connection point, allowing the rest of the structure to remain lightweight and adjustable.
4Reliability
If a latch mechanism is added to secure positioning, then reliability is improved, but device complexity increases
Solution Approach 1:
The latch mechanism is merged with the parallelogrammatic linkage structure. The latch (29) integrates with the links (16a, 16b, 17) and braces (23a, 23b) rather than being a separate added component. This merging provides secure positioning while minimizing the increase in device complexity.
Solution Approach 2:
The latch mechanism is designed to automatically engage and disengage based on the position of the head contact part. It provides self-locking functionality that secures the adjusted position without requiring additional control mechanisms, maintaining simplicity while improving reliability.
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
Enables adjustable and secure positioning of the head contact surface, withstands high forces by distributing loads through the parallelogrammatic linkage, and allows for a compact, lightweight, and cost-effective manufacturing process.
Implementation Method 1
The lower link forms with the base, cushion, and upper link a parallelogrammatic linkage. The brace transmits the force exerted in the case of a load applied by the seat occupant to the cushion support from the lower link to the upper link in such a way that a counter torque to the force applied by the cushion body to the upper link is created.
Implementation Method 2
An upper link has a front end pivoted at an upper support axis on the support and a rear end pivoted at an upper base axis on the base, and a lower link having a front end pivoted at a lower support axis on the support offset downward from the upper support axis and a rear end pivoted at a lower base axis on the base offset downward from the upper base axis.
Data Source
AI summary
A motor-vehicle headrest has a base fixable to a motor vehicle seat and a cushion support having a forwardly directed front face adapted to engage a head of a person in the seat. An upper link has a front end pivoted at an upper support axis on the support and a rear end pivoted at an upper base axis on the base, and a lower link having a front end pivoted at a lower support axis on the support offset downward from the upper support axis and a rear end pivoted at a lower base axis on the base offset downward from the upper base axis. The cushion is shiftable relative to the base between a rear position and a front position on pivoting of the links about the respective axes. A rigid brace is pivoted on the upper link between the upper axes and on the lower link between the lower axes.