Sofa bed

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Solution Overview

Problem

Existing sofa beds face issues such as increased rear occupation when folding, mechanical complexity, need for additional storage for cushions, excessive depth or width in certain configurations, and discomfort due to articulation placement, especially when transitioning between sofa and bed modes.

Innovation Solution

A sofa bed design featuring a support structure with a foldable leg rest, parallel mechanisms for vertical movement, a cushioned flexible body with machined parts and elastic upper layers, automatic unfolding mechanisms, and adjustable height arms, allowing for a wide bed configuration without excessive depth or storage needs, and providing leg support.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Area of moving object

If the back is folded horizontally coplanar with the seat using a sliding non-return ratchet, then the bed width is increased, but the rear occupation increases requiring separation from the wall

Engineering Contradiction:
Improvebed widthVSAvoidrear occupation
Core Design Contradiction:
Area of moving objectVSArea of stationary object

Solution Approach 1:

The patent changes the folding direction from horizontal (increasing rear occupation) to vertical (increasing bed height). The backrest folds downward onto the mattress rather than horizontally across it, eliminating the need to move the sofa away from the wall while still providing adequate bed width.

Inventive Principle:
Principle #17Another dimension (Dimensionality change)

2Device complexity

If the articulation is placed in the longitudinal center of the bed, then the folding mechanism is simplified, but comfort is reduced in the most commonly used area

Engineering Contradiction:
Improvefolding mechanism complexityVSAvoidcomfort in commonly used area
Core Design Contradiction:
Device complexityVSEase of operation

Solution Approach 1:

The patent positions the folding articulation asymmetrically at the front of the seat rather than in the longitudinal center. This allows the backrest to fold downward without interfering with the central sleeping area, maintaining comfort while enabling the transformation mechanism.

Inventive Principle:
Principle #4Asymmetry

3Strength

If a complex mechanism with springs is used to articulate the bed base, then the sofa structure is supported, but mechanical complexity increases and cushions require additional storage

Engineering Contradiction:
Improvesofa structure supportVSAvoidmechanical complexity
Core Design Contradiction:
StrengthVSDevice complexity

Solution Approach 1:

The patent removes the complex spring mechanism and cushion storage requirement by designing the backrest to fold downward onto the mattress. The cushions remain in place on the seat, eliminating the need for additional storage space while maintaining structural support through a simpler articulation system.

Inventive Principle:
Principle #2Taking out (Extraction)

4Adaptability or versatility

If the bed base is folded or divided into sections, then the sofa configuration is achieved, but the mattress becomes thin and uncomfortable

Engineering Contradiction:
Improvesofa configuration capabilityVSAvoidmattress comfort
Core Design Contradiction:
Adaptability or versatilityVSStrength

Solution Approach 1:

The patent uses a dynamic folding mechanism where the backrest moves vertically onto the mattress rather than folding the mattress itself. This maintains the mattress thickness and comfort while achieving the sofa configuration through backrest positioning.

Inventive Principle:
Principle #15Dynamics

5Length of moving object

If the seat depth is increased to accommodate hospital guest bed configuration, then the bed base fits into the drawer, but excessive space is occupied in the sofa area

Engineering Contradiction:
Improveseat depthVSAvoidspace occupation in sofa area
Core Design Contradiction:
Length of moving objectVSArea of stationary object

Solution Approach 1:

Instead of increasing seat depth to accommodate the bed configuration, the patent inverts the approach by having the backrest fold downward onto the mattress. This maintains a compact seat depth suitable for sofa use while achieving adequate bed dimensions through vertical folding.

Inventive Principle:
Principle #13The other way round (Inversion)

Data Source

PatentEP3351145B1Sofa bed
Publication Date: 2019.09.25 FAMA SOFAS
  • EP3351145B1 patent drawingFigure 1~2
  • EP3351145B1 patent drawingFigure 3
  • EP3351145B1 patent drawingFigure 4

AI summary

The invention relates to a sofa bed (1) comprising: a support structure (2) on the floor, a main seat base (3) arranged on said support structure (2), a front foldable leg rest (4) which is fixed to the structure (2) by means of a first articulation (5), and a cushioned body (6) that covers the main base (3) and the leg rest (4).