Multi-Position Backrest Latch with L-Shaped Catch Slot
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Solution Overview
Problem
Existing backrest latches in motor vehicles only allow for switching between an upright and folded-down position, failing to provide the option to vary the upright position, which limits comfort for rear passengers and does not meet the requirement for locking in multiple positions.
Innovation Solution
A closing device with a catch featuring an L-shaped insertion slot allowing for two closed positions, a comfort pawl with ratchet hooks, and a blocking pawl that secures the comfort pawl, enabling the backrest to be locked in two different upright positions while maintaining the seatback angle despite misalignment, and allowing for easy transition between these positions using a handle or electric drive.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a conventional single-position locking mechanism is used, then the structure is simple, but the backrest cannot be locked in multiple upright positions, limiting comfort and functionality
Solution Approach 1:
The locking mechanism is segmented into multiple independent pawls (first comfort pawl, second comfort pawl, first blocking pawl, second blocking pawl) that can engage with corresponding ratchet teeth at different positions. Each pawl-ratchet pair independently provides locking capability at a specific position, enabling multi-position locking without requiring a completely complex new mechanism design
Solution Approach 2:
The catch includes an L-shaped insertion slot with two distinct limbs (first limb and second limb) oriented at different angles. The closing pin can engage with either limb to establish different closed positions, effectively using spatial dimensionality to create multiple stable states within a single locking mechanism structure
2Manufacturing precision
If the insertion slot is designed to accommodate closing pin misalignment, then the seatback angle stability improves, but the slot geometry becomes more complex
Solution Approach 1:
The insertion slot is designed as an asymmetric L-shape with two limbs of different orientations and lengths. The first limb is optimized for engagement when the closing pin approaches from one angle, while the second limb is optimized for a different approach angle. This asymmetric geometry naturally compensates for manufacturing tolerances and misalignment while maintaining consistent seatback angles
Solution Approach 2:
The slot geometry parameters (limb lengths, angles, and orientations) are specifically optimized to compensate for allowable closing pin misalignment. By carefully selecting these geometric parameters, the mechanism maintains the targeted seatback angle across the full range of expected pin position variations
3Ease of operation
If a multi-pawl locking mechanism is used, then operating forces are reduced and noise characteristics improve, but the mechanism complexity increases
Solution Approach 1:
Multiple pawls (comfort pawls and blocking pawls) are combined within a single integrated catch structure. The blocking pawls work together with the comfort pawls to provide both secure locking and easy release functionality. This merging of multiple functional elements into one unified component achieves the benefits of multi-pawl mechanisms while containing the complexity within a single manufacturable part
Data Source
AI summary
A closing device for use in motor vehicles, in particular a backrest latch for locking and unlocking backrests in motor vehicles. The closing device is also provided with a multi-pawl locking mechanism substantially consisting of a catch, a comfort pawl that interacts with the catch and a blocking pawl that secures the comfort pawl. The catch includes an L-shaped insertion slot for a closing pin for forming at least a first closed position and a second closed position.