Collapsible Step Linkage Using Gravity to Stabilize Extended Position
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Solution Overview
Problem
Automatic step systems for recreational vehicles often provide a 'spongy' or unstable feel and are prone to retracting under load, necessitating an improved mechanism for extending and retracting collapsible steps.
Innovation Solution
A collapsible step assembly featuring a mounting frame, linkage assembly with non-parallel links, and a pivot member, where a gravitational load on the step urges one of the links to rotate and press against a stop, stabilizing the step in the extended position and resisting retraction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Extent of automation
If a motor assembly with gear assembly is used to automatically extend and retract the step, then the step extension is automated, but the step gives a spongy or unstable feel and loads tend to move the step toward retraction
Solution Approach 1:
The patent inverts the conventional approach by using the gravitational load on the step to actively press the linkage against the stop, rather than relying on motor force alone to counteract gravity. This inversion transforms the harmful effect of gravity into a stabilizing mechanism that ensures firm contact and eliminates the spongy feel.
Solution Approach 2:
The patent converts the harmful effect of gravitational load (which tends to retract the step) into a beneficial force that presses the linkage assembly against the stop. The load that previously caused instability now ensures firm engagement and stable positioning of the step in the extended state.
2Ease of operation
If a motor rotates a pivot rod through a gear assembly to extend and retract the step, then the step can be automatically positioned, but the system complexity increases and the step feels unstable under load
Solution Approach 1:
The patent implements self-service by designing the linkage assembly to automatically self-adjust and self-stabilize under load. The gravitational force on the step automatically presses the linkage against the stop, eliminating the need for complex feedback control systems or preloading mechanisms, thereby simplifying the overall device while maintaining ease of operation.
3Device complexity
If the step is designed without preloading, then the device complexity is reduced, but the step may have play or instability under load
Solution Approach 1:
The patent eliminates the need for preloading by converting the gravitational load into a beneficial force that creates the necessary contact pressure. The weight of the step itself becomes the preload, pressing the linkage against the stop and eliminating play without requiring additional springs or preloading mechanisms.
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
The solution provides a stable and load-resistant step extension mechanism that maintains the step in the extended position without preloading, reducing play and ensuring the step remains secure under applied loads.
Implementation Method 1
A gravitational load on the step urges at least one of the links of the linkage assembly in the direction of rotation of the link toward extension of the step
Data Source
AI summary
The present invention provides an improved collapsible step assembly for recreational vehicles. The movable step apparatus comprises a mounting frame, at least one step mounted to the frame through a linkage assembly, and a pivot rod with a longitudinal axis of rotation. In use, the pivot rod is rotatably mounted to the frame and rotates the linkage assembly and the at least one step between an extended position and a retracted position. Rotating the pivot rod in a first direction moves the step to the extended position, and rotating the pivot rod in the opposite direction moves the step to the retracted position. The linkage assembly includes a link which is movable in the direction of the link toward extension of the step to contact a stop of the frame that reacts against a gravitational load acting on the step.