Dual-Cable Lumbar Support for Symmetric Seat Back Adjustment
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Solution Overview
Problem
Existing lumbar supports in seat backs, such as those in motor vehicle and office furniture, suffer from asymmetrical movement and require a large pulling force for minimal adjustment due to the use of a single Bowden cable, leading to inadequate relief in the lordosis area.
Innovation Solution
A lumbar support system utilizing two coupled traction cables that move the lumbar support basket symmetrically relative to the seat back frame, allowing for twice the adjustment path with the same pulling length, and are guided within a movable device to ensure symmetrical and efficient movement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single Bowden cable is used to move the lumbar support basket, then the structure is simple, but the movement becomes asymmetrical and requires large pull length for small adjustment
Solution Approach 1:
The single Bowden cable is segmented into two separate pull cables that attach to opposite sides of the frame. This segmentation allows each cable to independently control the movement on its respective side, ensuring symmetrical movement of the lumbar support basket while maintaining operational simplicity through a single actuator that controls both cables via a common cable housing.
2Device complexity
If a single Bowden cable is used to move the lumbar support basket, then the structure is simple, but the adjustment path is limited for a given pull length
Solution Approach 1:
The system transitions from a single-dimension pull (one cable pulling in one direction) to a two-dimensionally distributed pull system where two cables pull from opposite sides simultaneously. This dimensional redistribution allows the same pull length to generate twice the effective adjustment path, as both cables work in parallel to move the lumbar support basket along its adjustment trajectory.
3Device complexity
If a single Bowden cable is used, then the actuator placement is flexible, but the pull force distribution becomes asymmetrical causing lateral movement
Solution Approach 1:
The system intentionally introduces asymmetry in cable routing by having the two pull cables attach to opposite sides of the frame at different locations, while the actuator remains positioned asymmetrically on one side of the seat back. This controlled asymmetry in attachment points ensures that the pull forces are distributed symmetrically to the lumbar support basket, preventing lateral movement and maintaining positional stability during adjustment.
Data Source
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AI summary
The invention relates to a lordosis support which is disposed in a backrest frame of a seat. Said lordosis support comprises a lordosis supporting cage (12) which is arranged in a backrest frame (10) of the seat as well as a pulling device that modifies the position of the lordosis supporting cage (12) relative to the frame. The inventive lordosis support is characterized in that the pulling device is provided with two traction cables (16, 17) which are coupled to the lordosis supporting cage (12) and the frame in such a way that the lordosis supporting frame (12) is moved relative to the plane defined by the backrest frame (10) of the seat when the pulling device is pulled.