Retractable Wheel Stepladder with Lever-Actuated Front Tilt
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Solution Overview
Problem
Conventional rolling steps for working at height, such as those defined by French standards NF P 93-352 and NF P 93-353, require significant user effort to maneuver due to the need to lift and tilt them for wheel deployment, leading to fatigue, safety risks on uneven surfaces, and potential slipping, especially when not enough weight is applied to retract the front wheels.
Innovation Solution
A design featuring retractable rear wheels biased by springs and a tilting front wheel mechanism actuated by a lever, allowing easy deployment and retraction for rolling, ensuring the step remains stable when not in use and reducing the risk of slipping by maintaining contact with the ground when not in motion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the step is provided with fixed rear wheels that are raised when the step rests on the ground, then the step can be moved by rolling when wheels touch the ground, but sufficient force is required to lift the step which causes unnecessary fatigue for the user when repeated
Solution Approach 1:
The patent applies dynamics by making the wheel mounting system movable rather than fixed. The rear wheels are mounted on springs that allow them to move between a raised position (when step is in use) and a lowered position (when step needs to be moved). The front running gear tilts between retracted and deployed positions based on whether the step is stationary or being moved. This dynamic adjustment eliminates the need for manual lifting while enabling easy rolling transport.
Solution Approach 2:
The patent uses spring mechanisms to provide counterweight force against the weight of the step. The springs are pre-loaded to automatically raise the rear wheels when the step is placed on the ground, counteracting the gravitational force that would otherwise require the user to lift the step manually. This eliminates the need for repeated lifting operations.
2Reliability
If the front wheels are retracted by placing weight on the step, then the wheels are retracted when the user is perched on the step, but the step is mobile as long as the step is free of any weight which risks slipping away on sloping ground
Solution Approach 1:
The patent applies self-service by designing a manual actuation mechanism where the user controls wheel retraction through a lever operation rather than relying on body weight. The user can easily actuate the lever to retract or deploy the front running gear as needed, without needing to climb on the step or apply their weight. This provides reliable control in all situations, including when the step is empty or on sloping ground.
3Reliability
If the front wheels are retracted by imposing sufficient weight on the step, then the wheels tip to retracted position, but the user is exposed to the risk of falling if he does not impose sufficient weight on the step from the first step
Solution Approach 1:
The patent replaces the weight-dependent retraction mechanism with a manual lever actuation system. The user can reliably control the front running gear position through the lever without needing to climb on the step or apply their body weight. This eliminates the safety risk of falling while providing easy, deliberate control over wheel retraction regardless of the user's position or the step's load.
4Ease of operation
If manual actuation of the lever causes the deployment of the front wheel, then the step can be temporarily placed in a rolling configuration allowing it to be moved easily, but the front wheel returns by gravity to its retracted position which allows the running board to rest on the ground at least by its front uprights
Solution Approach 1:
The patent uses a dynamic tilting mechanism for the front running gear that pivots between retracted and deployed positions. The lever actuation tilts the crosspiece, which mechanically transfers motion to deploy or retract the front wheel. The mechanism uses gravity and mechanical leverage to maintain positions without requiring complex motors or actuators, achieving easy movement while controlling complexity through clever mechanical design.
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
Enhances user ergonomics and safety by reducing manual effort required for movement, preventing unintended rolling, and ensuring stability on various ground surfaces by maintaining contact through retractable wheels and gravity-assisted retraction of the front wheel.
Implementation Method 1
each rear wheel being biased towards its position deployed by a spring
Implementation Method 2
the front wheel returns by gravity to its retracted position
Data Source
Figure 1~3
Figure 4~5
Figure 6
AI summary
Footboard (1) comprising: - a front plane (2) including a pair of front uprights (3), - a rear plane (9) articulated on the front plane (2) and including a pair of rear uprights (10), - a pair of retractable rear wheels (33) mounted movable relative to the rear plane (9) between a retracted position and a deployed position, each rear wheel (33) being forced towards its deployed position by a spring (34), - a front rolling assembly (39) equipped with a retractable front wheel (40), the front rolling assembly (39) being mounted movable relative to the front plane (2) between a retracted position and a deployed position, - a mechanism (46) for actuation of the front wheel (40), which includes an operating lever (47) articulated on a front upright (3), and a rod (48) running along the front upright (3) and coupling the lever (47) to the front rolling assembly (39).