Stepladder Shelf With Protrusion For Load Support
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Solution Overview
Problem
Existing tool-carrying shelves for stepladders have limited load resistance, requiring reduced plate sizes and expensive treated metallic materials for stability, and are prone to incorrect assembly and deformation during transport.
Innovation Solution
A shelf assembly with a protrusion that fits into the hollows of the stepladder's beams, providing additional support and increased load capacity without hindering user movement, using a thermoplastic material like polypropylene for cost-effectiveness and resistance to external attacks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If an articulated rod is used to increase load capacity, then the admissible load increases, but the device complexity increases and requires expensive treated metallic materials
Solution Approach 1:
The patent extracts the articulated rod from the system and replaces it with a simplified protrusion-integration solution. The shelf directly integrates protrusions that fit into hollows on the riser, eliminating the need for separate articulated rod components and their complex assembly procedures.
Solution Approach 2:
The patent merges the support function and attachment function into a single integrated structure. The protrusions are directly formed as part of the shelf structure, combining what were previously separate components (shelf and articulated rod) into one unified element.
2Reliability
If treated metallic materials are used for the articulated rod, then resistance to corrosion and shocks improves, but the manufacturing cost increases
Solution Approach 1:
The patent changes the material parameter from treated metal to thermoplastic polymer. This material substitution maintains adequate resistance to corrosion and shocks while dramatically reducing manufacturing cost and simplifying the production process through injection molding or similar thermoplastic forming methods.
Solution Approach 2:
The patent employs a cost-effective thermoplastic material that, while potentially having shorter service life than treated metal, provides sufficient durability for the application at a fraction of the cost, making the shelf economically viable for mass production and widespread use.
3Strength
If the articulated rod is used, then load support capability improves, but the risk of incorrect assembly and deformation during transport increases
Solution Approach 1:
The patent implements a nesting mechanism where the protrusions fit into hollows on the riser, creating a self-aligning and self-locking structure. This nested configuration naturally guides correct assembly and prevents mispositioning, eliminating the need for complex alignment procedures required by articulated rods.
Solution Approach 2:
The protrusions are pre-formed as integral parts of the shelf during manufacturing, with their geometry precisely configured to match the hollows on the riser. This preliminary preparation ensures that during assembly, the components naturally align and connect correctly without requiring additional adjustment or precision handling.
Data Source
Figure 1
Figure 2~3
Figure 4~5
AI summary
Assembly (5) comprising: a step-up platform (2) or stepladder platform (1) comprising two stringers (8) connected by a plurality of parallel rungs (7) including an extreme rung (6), each of the stringers comprising hollows (10) beyond the extreme rung, a shelf (4) intended to support a predetermined load, the shelf comprising a fixing part (17) provided with two members (29) capable of fitting into the hollows so as to allow the shelf to be mounted on the stringers, the shelf comprising a projection (34) configured to come into contact with the extreme rung when the shelf is mounted on the step-up platform, so as to form a support.