Folding Stairs Four-Bar Linkage Flap Stability

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Solution Overview

Problem

Existing folding stairs with hinge mechanisms struggle to effectively support loads and user weight, particularly in light wooden designs intended for ceiling installations, as the flap serving as a supporting structure requires reinforcement to maintain stability during unfolding and use.

Innovation Solution

The design employs a four-bar linkage mechanism with connecting rods and a double-arm lever to maintain the rotation axis of the first stair segment relative to the door frame, combined with tension springs for stability and a supporting beam to distribute stresses, allowing the flap to open and close without additional locking mechanisms, facilitating easier use and storage.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If the flap is reinforced to support loads from stair segments and users, then the load-bearing capacity and stability are improved, but the weight and complexity of the flap increase

Engineering Contradiction:

Improveload-bearing capacity of flapVSAvoidweight of flap

Core Design Contradiction:

StrengthVSWeight of moving object

Solution Approach 1:

The flap is divided into multiple segments connected by hinges, allowing each segment to be lighter while collectively supporting the required loads. The segmentation enables the flap to flex and distribute forces more efficiently across multiple connection points.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Connecting rods are introduced as intermediary elements between the flap and the stair segments. These rods act as force distributors, transferring and dispersing the loads from the stair segments and users across multiple attachment points on the flap, reducing the stress concentration on any single point of the flap structure.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Stability of the object's composition

If the flap is reinforced with additional supporting structures, then the stability during unfolding is improved, but the device complexity increases

Engineering Contradiction:

Improvestability of flap during unfoldingVSAvoidcomplexity of flap structure

Core Design Contradiction:

Stability of the object's compositionVSDevice complexity

Solution Approach 1:

The connecting rods serve multiple functions: they connect the flap to the stair segments, provide structural support, distribute loads, and enable controlled movement during unfolding. This multi-functionality reduces the need for separate reinforcing structures, maintaining stability while limiting complexity growth.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The flap structure incorporates dynamic elements including hinges and connecting rods that allow controlled movement during unfolding. This dynamic design provides inherent stability through mechanical constraints and force distribution, eliminating the need for complex static reinforcing structures.

Inventive Principle:

Principle #15Dynamics

3Adaptability or versatility

If the rotation axis position changes during unfolding, then the unfolding motion is more flexible, but the structural integrity and load distribution deteriorate

Engineering Contradiction:

Improveunfolding motion flexibilityVSAvoidstructural integrity during unfolding

Core Design Contradiction:

Adaptability or versatilityVSStrength

Solution Approach 1:

The connecting rods act as intermediary elements that maintain the rotational relationship between the flap and stair segments. By providing fixed attachment points and controlled connection geometry, these rods ensure that the rotation axis remains stable while still allowing the necessary unfolding motion, thus preserving structural integrity during movement.

Inventive Principle:

Principle #24Intermediary (Mediator)

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

This configuration enhances the structural integrity and usability of light wooden folding stairs by distributing loads effectively, reducing the weight and cost of the flap, while enabling convenient deployment and storage due to minimized dimensions.

Implementation Method 1

Flap is suspended on the first segment of stairs by means of at least two couples of connecting rods, which together with first segment of stairs form four-bar linkage

Methodology Applied

Scientific EffectFour-bar linkage: Four-Bar Linkage

Implementation Method 2

Within the couple of connecting rods located closest to hinge holders at least one of connecting rods is a double-arm lever connected in its central part rotationally with first segment of stairs

Methodology Applied

Scientific EffectLever: Lever

Implementation Method 3

Stairs are also provided with tension springs, supporting rising of stairs during their closing and attenuating dropping of stairs during their opening

Methodology Applied

Scientific EffectSpring: Spring

Data Source

PatentEP2636814B1Folding stairs, especially light wooden stairs

Publication Date: 2018.01.31 FAKRO PP SPOLKA Z O O

Figure 1
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Figure 3~4

AI summary

Folding stairs have three segments (11, 12, 13) of ladder stairs connected by hinges. The first segment (11) of stairs is connected by an articulated joint with door frame (2) by means of hinge holders (3) fitted from inside to door frame wall, and during unfolding of these stairs rotation axle of the first segment of stairs does not change its position against door frame. Flap (4) is suspended to the first segment of stairs by means at least two couples of connecting rods (41, 42), which together with the first segment of stairs and the flap form four-bar linkage.