Four-Bar Stroller Frame Locking Against Accidental Folding

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Solution Overview

Problem

Conventional stroller frames are complicated to fold, prone to accidental folding, and occupy a large area when folded, posing safety and storage challenges.

Innovation Solution

A stroller frame with a four-bar linkage structure and a lock mechanism that allows for flexible folding and locking, featuring a lock mechanism with an engaging member and elastic members to prevent accidental folding, along with a brake mechanism to secure the frame in an expanded state.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If the stroller frame uses a conventional folding structure, then the folding operation becomes complicated, but the frame can be folded

Engineering Contradiction:

Improvefolding operationVSAvoidfolding structure

Core Design Contradiction:

Ease of operationVSDevice complexity

Solution Approach 1:

The stroller frame is divided into multiple support members (first support member, second support member, third support member, fourth support member) that can independently pivot relative to each other. This segmentation allows the frame to be folded in a controlled manner through sequential pivoting actions, simplifying the folding operation while maintaining structural integrity.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent introduces a dynamic locking mechanism that can transition between locked and unlocked states. The locking member engages with the engaging member to lock the support members in expanded positions, and can be released to allow folding. This dynamic capability enables simple one-action folding while preventing accidental collapse during use.

Inventive Principle:

Principle #15Dynamics

2Area of stationary object

If the stroller frame is made foldable for convenient storage, then the storage space is reduced, but the frame becomes prone to accidental folding

Engineering Contradiction:

Improvestorage areaVSAvoidanti-accidental folding

Core Design Contradiction:

Area of stationary objectVSReliability

Solution Approach 1:

The locking mechanism is designed to proactively prevent accidental folding by maintaining engagement between the locking member and engaging member during normal use. The elastic member continuously applies force to keep the locking member engaged, creating a preliminary protective action against unintended folding before it can occur.

Inventive Principle:

Principle #9Preliminary anti-action

Solution Approach 2:

The elastic member provides continuous mechanical feedback to the locking mechanism, ensuring the locked state is maintained. When the support members are in the expanded position, the elastic member keeps the locking member engaged with the engaging member, providing real-time feedback that confirms the locked state and prevents accidental folding.

Inventive Principle:

Principle #23Feedback

3Device complexity

If the lock mechanism uses only elastic force for engagement, then the structure is simple, but the locking reliability may be insufficient

Engineering Contradiction:

Improvelock mechanism structureVSAvoidlocking reliability

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The locking mechanism merges multiple functions into a single integrated system: the elastic member provides engagement force, the locking member provides the locking action, and the engaging member provides the engagement interface. This combination of components working together achieves reliable locking without excessive structural complexity.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The locking mechanism uses composite functional design where the elastic member (providing continuous force) and the rigid locking member (providing structural integrity) work together. This functional composition achieves both simplicity and reliability by combining different mechanical properties in a unified locking system.

Inventive Principle:

Principle #40Composite materials

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 safe and compact folding of the stroller frame, preventing accidental collapse and facilitating easy storage, while maintaining stability and safety during use.

Implementation Method 1

a lock mechanism (60) able to lock the upper support member (40) and the lower support member (50) at an expanded angle

Methodology Applied

Scientific EffectElastic force: Elasticity

Data Source

PatentUS12473005B2Stroller frame and stroller

Publication Date: 2025.11.18 WONDERLAND SWITZERLAND AG

AI summary

A stroller frame (100) includes a front leg (10), a bottom tube (30), a rear leg (20), an upper support member (40) and a lower support member (50). The front leg (10), the bottom tube (30), the lower support member (50) and the upper support member (40) are pivotally connected to each other to form a four-bar linkage structure. The rear leg (20) is connected to an end of the bottom tube (30). A lock mechanism (60) is disposed at a pivot joint between the upper support member (40) and the lower support member (50). The lock mechanism (60) is able to lock the upper support member (40) and the lower support member (50) at an expanded angle, such that the front leg (10) is able to be expanded with respect to the bottom tube (30). The lock mechanism (60) is unlocked to release the upper support member (40) and the lower support member (50), such that the front leg (10) is able to be folded with respect to the bottom tube (30).