Telescopic Ladder Dovetail Stringer Profile
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Solution Overview
Problem
Existing telescopic ladders are obtrusive in their collapsed configuration due to wide stringer structures, and their manufacturing is limited to light metal, which restricts material options and requires thick profiles for strength, excluding materials like steel.
Innovation Solution
The ladder features stringers with planar flanges bent at an acute angle acting as dovetail guides, allowing for a narrow, flat collapsed configuration and enabling the use of metal sheets for construction, along with a countersunk bolt and wing nut system for mounting steps, and an articulated parallelogram mechanism for deployment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the stringers are made with a wide cross-sectional profile to ensure sufficient strength, then the structural strength is improved, but the collapsed configuration becomes obtrusive and wide
Solution Approach 1:
The stringers are designed to be nested within each other in the collapsed configuration, with each stringer fitting inside the previous one. This nesting arrangement dramatically reduces the overall width of the collapsed ladder while maintaining the necessary stringer dimensions for structural strength when deployed.
Solution Approach 2:
The stringers transition from a wide lateral arrangement in the deployed state to a compact nested arrangement in the collapsed state, effectively utilizing the vertical dimension for storage rather than occupying horizontal space. This dimensional transformation allows the ladder to be unobtrusive when stored against walls.
2Strength
If light metal is used with high material thickness to achieve sufficient strength, then the structural strength is improved, but the stringer structure becomes thick and manufacturing is limited
Solution Approach 1:
The patent changes the material parameter from light metal to steel, allowing for thinner wall thickness while maintaining or improving strength. This parameter change enables the use of conventional bending manufacturing processes and expands material options beyond extruded light metal.
Solution Approach 2:
The stringers are constructed as composite structures with a planar web and bent flanges forming a dovetail guide structure. This composite geometry provides both structural strength and telescopic guidance functions, eliminating the need for thick solid profiles.
3Device complexity
If the stringers are disposed adjacent to each other in the collapsed position, then the telescopic mechanism is simple, but the bunch of stringers becomes wide and obtrusive
Solution Approach 1:
Instead of disposing stringers adjacent to each other, the patent implements a nested configuration where each stringer is inserted within the previous one. This nesting principle maintains the simplicity of the telescopic mechanism while dramatically reducing the collapsed width from a lateral arrangement to a compact nested bundle.
4Device complexity
If a square or rectangular stringer profile is used for telescopic fitting, then the telescopic mechanism is simple, but the stringer structure becomes thick and obtrusive
Solution Approach 1:
The patent replaces the simple square or rectangular profile with a composite structure consisting of a planar web and bent flanges. This composite profile provides the necessary telescopic guidance surfaces while creating a flat, narrow collapsed configuration that is not obtrusive.
Solution Approach 2:
The flanges are bent at acute angles to form dovetail guides, introducing curved geometric elements that enable telescopic guidance without requiring thick solid profiles. This curved geometry allows for precise nesting and guidance while maintaining a slender overall shape.
Data Source
Figure 1~2
Figure 3
Figure 4~5
AI summary
A telescopic hang-on ladder including a set of ladder elements ( 1 1, 1 2 , 1 3 , 1 4 ...) coupled to each other so that the sequential ladder elements are telescopically movable relative to each other in order to extend and collapse the ladder. Each ladder element includes two parallel stringers (2 1 , 2 2 ) spaced apart from each other. The cross-sectional profile of a stringer comprises a planar web (3), and both long edges of the web comprise guide members, wherein the guide members of the stringer of each upper ladder element constitute a slide guide for the stringer of the adjacent lower ladder element. A step (4) extends between the stringers substantially perpendicularly to the lengthwise direction of the stringers (2 1 , 2 2 ) and is mounted at each end to the web (3) of the stringer. The stringers (2 1 , 2 2 ) of each ladder element are substantially fitted, for the most of their part, within the corresponding stringers of the adjacent upper ladder element. Both long edges of the web (3) comprise a planar flange (5, 6) bent at an acute angle relative to the plane of the web, wherein the flanges together with the web constitute said guide members, so that each stringer of the upper ladder element constitutes a dovetail guide for the stringer of the lower ladder element fitted within said stringer.