Vehicle Seat Headrest Cam Locking for Low-Force Unlocking
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Solution Overview
Problem
Existing motor vehicle seat headrests are complex due to multiple components and require additional effort to unlock, with insufficient robustness in securing the secondary body during impacts.
Innovation Solution
A simplified headrest design with a force return cam between the crosspiece and latch, eliminating the need for a spring to return the latch, and enhancing the locking edge's robustness by using a spring-loaded metal wire for unlocking, which reduces the effort required to unlock and improves the secondary body's locking stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a spring is used to return the latch to the locking position, then the latch can automatically return to locking position, but the device complexity increases and additional force is required to unlock
Solution Approach 1:
The patent removes the spring component from the system entirely. Instead of using a spring to return the latch to the locking position, the design uses the cam mechanism where the crosspiece's translational movement directly drives the latch through its cam surface, eliminating the need for elastic energy storage and recovery components.
Solution Approach 2:
The cam acts as an intermediary element between the crosspiece and the latch. The cam surface translates the horizontal movement of the crosspiece into vertical movement of the latch, providing a mechanical advantage that moves the latch without requiring a spring return mechanism.
2Reliability
If multiple components are used in the locking device, then the locking function is achieved, but the unlocking effort required increases
Solution Approach 1:
The cam surface is a curved geometric profile that converts small horizontal displacement of the crosspiece into larger vertical displacement of the latch. This curvature provides mechanical advantage, reducing the force required at the button while maintaining reliable locking engagement.
Solution Approach 2:
The mechanism transforms the unlocking action from a vertical lifting motion to a horizontal pushing motion. By moving the effort application to a different dimension (horizontal vs vertical), the design leverages the cam's geometric transformation to reduce the required force.
3Device complexity
If a simple locking mechanism is used, then the device complexity is reduced, but the robustness during impact decreases
Solution Approach 1:
The locking edge of the latch is designed to engage the rack teeth in advance, creating a pre-loaded mechanical interlock. This preliminary engagement ensures that when impact forces occur, the locking interface is already established and can resist the sudden loads without requiring additional active components.
Solution Approach 2:
The locking interface combines multiple functional elements (latch body, locking edge, rack teeth, cam surface) into an integrated assembly that distributes impact forces across multiple contact points, enhancing overall strength without adding separate reinforcement components.
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 simplifies the unlocking process, reduces the effort needed, and provides enhanced robustness to prevent unwanted removal of the latch, ensuring secure positioning during impacts.
Implementation Method 1
a force return cam arranged between said crosspiece and said latch, said cam having in longitudinal view: a point of rotational connection to said crosspiece along a longitudinal axis of rotation, and... an actuating edge forming a cam surface bearing on said latch, said slot being arranged so as to induce, during the movement of said crosspiece in unlocking and the transverse movement of said point which results therefrom: a movement of said locking edge releasing the actuation of said latch in unlocking, and a rotation of said cam around said axis, said rotation producing a vertical movement of said actuating edge pushing said latch towards its unlocking position
Data Source
Figure 1~2a
Figure 2b~3
Figure 4a~4b
AI summary
The invention relates to a headrest (1) for a motor vehicle seat, said headrest comprising a first locking device for a main body (3), a second device comprising a latch (5) for locking a secondary body sliding longitudinally on said main body, a crossbar (7) for simultaneously unlocking said devices, a cam (9) disposed between said crossbar and said latch, said cam having a rotational connection point (10) to said crossbar, a first finger (12) mounted to slide in a slot (13) of said main body, a locking edge for said latch in the locked position and an actuating edge for said latch, said slot being arranged so as to induce a displacement of said locking edge releasing the actuation of said latch in unlocking, and a rotation of said cam effecting a vertical displacement of said actuating edge pushing said latch towards its unlocking position.