Convertible Sofa Stretching Linkage for Length and Backrest Alignment
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Solution Overview
Problem
Current mechanical stretching devices for convertible sofas suffer from inconsistent length adjustment, misalignment of backrests, and sagging when loaded, affecting the appearance and quality of the sofa.
Innovation Solution
A mechanical stretching device with a complex linkage system involving foot levers, connecting rods, a seahorse member, rotating shaft transmission, and springs, which includes limiting surfaces and rivets for precise control and alignment, ensuring consistent unfolding and folding lengths, and maintaining the sofa's appearance and stability under load.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a conventional mechanical stretching device is used, then the sofa can be converted between sitting and lying positions, but the length increased by unfolding is not consistent with the length reduced by folding, causing appearance defects
Solution Approach 1:
The patent employs dynamic linkage mechanisms with multiple connecting rods (first through sixth connecting rods) and foot levers that automatically adjust the sofa's length during transformation. The linkage system dynamically compensates for dimensional changes, ensuring the sofa returns to its original length after conversion, thus resolving the length consistency issue while maintaining conversion functionality.
Solution Approach 2:
The invention uses adjustable parameters in the linkage mechanism, including the positions of limiting surfaces on foot levers and connecting rods, and the configuration of support members. By optimizing these parameters, the system achieves precise control over the sofa's dimensional changes during transformation, ensuring length consistency between folded and unfolded states.
2Device complexity
If a conventional mechanical stretching device is used, then the sofa structure is simple, but the back is loose by about 40 mm and backs are not aligned, affecting the grade or style of the sofa
Solution Approach 1:
The patent implements dynamic control of backrest positioning through the linkage mechanism. As the sofa transforms between positions, the connecting rods and foot levers automatically adjust the backrest angle and position, ensuring consistent alignment (within 3 mm tolerance) without requiring complex additional alignment mechanisms.
Solution Approach 2:
The limiting surfaces on the foot levers and connecting rods act as mechanical feedback elements. These surfaces engage at specific positions during transformation, providing automatic feedback control that ensures the backrest returns to the correct aligned position, maintaining aesthetic appearance while keeping the overall structure relatively simple.
3Device complexity
If a conventional mechanical stretching device is used, then the structure is simple, but after a load is placed, the product subsides by about 40 mm, affecting appearance
Solution Approach 1:
The patent incorporates support members (first and second support members) that act as counterweight elements. These members are positioned to provide upward support force that counteracts the subsidence caused by loaded weight, reducing subsidence from 40 mm to approximately 2 mm while maintaining overall structural simplicity.
Solution Approach 2:
The linkage mechanism dynamically responds to applied loads by adjusting the positions of connecting rods and foot levers. This dynamic adjustment allows the sofa to maintain stability under load, with the mechanical system automatically compensating for weight-induced deformation while preserving the simplicity of the overall structure.
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 solution ensures consistent length adjustment, minimizes backrest misalignment, and reduces sagging by about 2 mm, maintaining the aesthetic and quality standards of a fixed sofa.
Implementation Method 1
a spring, and a bottom connecting rod
Data Source
AI summary
A mechanical stretching device includes first, second, third and fourth foot levers, a side plate, first, second, third, fourth, fifth and sixth connecting rods, a first support member, a second support member, a linkage member, a connecting member, a rotating shaft transmission member, a spring, and a bottom connecting rod. A first limiting surface and a second limiting surface are disposed on the second foot lever, a third limiting surface is disposed on the fourth foot lever, a fourth limiting surface and a fifth limiting surface are disposed on the side plate, a sixth limiting surface and a seventh limiting surface are disposed on the second connecting rod, an eighth limiting surface is disposed on the sixth connecting rod, a ninth limiting surface is disposed on the first support member, and a tenth limiting surface is disposed on the linkage member.