Extension Ladder Nested Rail Design for Compact Stacking
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Solution Overview
Problem
Conventional extension ladders face challenges in storage and shipping due to their width, as they cannot be easily stacked or nested, limiting their density and increasing shipping costs.
Innovation Solution
The extension ladder design features a fly section whose rails are nested within the rails of a base section, utilizing J-locks or swing locks to guide and position the fly section, allowing it to slide and lock into place, reducing the overall width and enabling more efficient stacking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the extension ladder uses a conventional side-by-side rail configuration, then the ladder provides adequate structural strength and stability, but the overall width prevents efficient stacking and increases storage and shipping costs
Solution Approach 1:
The patent applies nesting by placing the fly section rails inside the base section rails when retracted, similar to nested dolls. The C-shaped cross-section of base rails is designed to receive and contain the fly rails within its curvature, allowing compact stacking while maintaining structural integrity during extension
2Volume of moving object
If the fly section is placed alongside the base section, then the ladder maintains simplicity in structure, but the width prevents multiple ladders from being stacked together efficiently
Solution Approach 1:
The patent transitions from a two-dimensional side-by-side arrangement to a three-dimensional nested arrangement. The C-shaped rail profile creates a vertical containment structure that receives fly rails from above, utilizing the vertical dimension to achieve compact horizontal footprint when retracted
3Ease of operation
If the rails are designed with stems for nesting, then the fly section can be properly positioned and guided, but the manufacturing complexity increases
Solution Approach 1:
The rail structure is segmented into distinct functional zones: the C-shaped containment profile, the stems protruding inward, and the flange regions. This segmentation allows each element to be formed independently during manufacturing, with stems acting as separate positioning features that can be integrated through standard forming processes
Data Source
Figure 1
Figure 2~4B
Figure 3
AI summary
An extension ladder having a fly section rested in a base section. A method for positioning an extension ladder. A system for moving extension ladders.