Collapsible Cart Linkage for Compact Under-Rack Storage

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Solution Overview

Problem

Existing shopping carts with collapsing mechanisms do not allow for compact storage due to the front legs being folded over the basket, making it difficult to store them efficiently on vehicle trunks.

Innovation Solution

A cart design that transitions from a use state to a storage state through coordinated folding of front and rear leg parts, where the legs are stored below the rack part, utilizing a simple link mechanism without actuators, allowing for compact storage by sliding onto a cargo rack.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If the front legs are folded over the basket in existing collapsing mechanisms, then the cart can be collapsed, but the cart in the collapsed state cannot be stored in a compact manner

Engineering Contradiction:
Improvecollapsing capabilityVSAvoidstorage volume
Core Design Contradiction:
Ease of operationVSVolume of moving object

Solution Approach 1:

Instead of folding the front legs over the basket as in conventional designs, this patent inverts the folding direction by storing the front legs below the upper surface of the rack part. The front leg parts are configured to fold downward and rearward, passing below the rack part to a stored position, which fundamentally changes the collapse geometry to achieve compactness.

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

Solution Approach 2:

The patent employs coordinated folding between front and rear leg parts in different spatial dimensions. The front leg parts fold in a first direction (downward and rearward below the rack), while the rear leg parts fold in a second direction (upward and forward above the rack), utilizing three-dimensional space efficiently to achieve compact storage.

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

2Ease of operation

If a complex actuator mechanism is used to coordinate the folding of front and rear legs, then the cart can collapse properly, but the device complexity increases

Engineering Contradiction:
Improvecoordinated foldingVSAvoidmechanism complexity
Core Design Contradiction:
Ease of operationVSDevice complexity

Solution Approach 1:

The cart employs a self-service collapsing mechanism where the user simply pulls the handle, and the coordinated folding of front and rear leg parts occurs automatically through the mechanical linkage built into the structure. The connection part between front and rear leg parts creates a mechanical relationship that causes one leg part to move in coordination with the other without requiring external actuators or complex control systems.

Inventive Principle:
Principle #25Self-service

Solution Approach 2:

The patent merges the collapsing functions of front and rear leg parts into a unified mechanical system. The connection part integrates the movement of front leg parts and rear leg parts into a single coordinated action, where pulling the handle simultaneously initiates the folding sequence of both leg parts through the mechanical coupling, eliminating the need for separate actuation mechanisms.

Inventive Principle:
Principle #5Merging (Combining)

Data Source

PatentEP4450368B1cart
Publication Date: 2026.05.06 TSUBAKIMOTO CHAIN CO
  • EP4450368B1 patent drawingFigure 1
  • EP4450368B1 patent drawingFigure 2
  • EP4450368B1 patent drawingFigure 3

AI summary

A compactly collapsible cart is provided. The cart includes: a rack part on which a load is placed, and a pair of front leg parts and a pair of rear leg parts provided to the rack part and having wheels on distal ends thereof. The cart is able to transition from a use state for use as a cart, through coordinated folding of the pair of front leg parts and the pair of rear leg parts, to a storage state in which the front and rear leg parts are stored below an upper surface of the rack part.