Motorized Collapsible Step Linkage Force Isolation
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Solution Overview
Problem
Existing automatic step systems for recreational vehicles often develop a 'spongy' or unstable feel over time due to mechanical failure, leading to excessive force transfer to the drive system and potential premature failure.
Innovation Solution
A collapsible step assembly with a two-part linkage system and a pivot member, where the pivot member is rotatably mounted to a frame and connected to a motor through a worm gear drive, isolating the motor from excessive forces and preventing 'popping' impacts by aligning the crank with the link in the extended position.
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 assembly, then the step extension and retraction are automated, but the system fails over time and gives a spongy or unstable feel
Solution Approach 1:
The linkage system is divided into two separate parts: a crank that rotates with the pivot rod and a separate link that is fixed to the frame. This segmentation allows the crank to rotate freely without transferring excessive forces to the motor, while still achieving the desired step extension and retraction motion. The separation of functions between the rotating crank and the fixed link prevents the spongy feel and premature failure experienced in unified linkage systems.
Solution Approach 2:
The harmful force transfer path is extracted from the motor assembly by introducing a frame-fixed link that does not rotate with the pivot rod. This link serves as a force isolation element, preventing excessive forces from being transferred back to the motor and gear assembly, thereby eliminating the source of premature failure and instability.
2Reliability
If the crank is fully aligned with the link in the extended position, then excessive forces are prevented from being transferred to the drive system, but the linkage complexity increases
Solution Approach 1:
The linkage is segmented into a crank portion and a link portion that are pivotally connected but not rigidly fixed together. The crank rotates with the pivot rod while the link remains fixed to the frame, creating a pivotal connection point that allows force isolation. This segmentation achieves force protection without requiring complex additional mechanisms.
Solution Approach 2:
The pivotal connection between the crank and link serves as an intermediary element that mediates between the rotating pivot rod and the fixed frame. This intermediary allows the crank to rotate freely while preventing excessive forces from being transferred to the motor, achieving force protection with minimal added complexity.
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
This configuration enhances the durability and longevity of the motor and reduces servicing needs by minimizing force transfer to the drive system, eliminating the 'spongy' feel and preventing unwanted impacts during step extension and retraction.
Implementation Method 1
The motor, mounted to the frame, has an output shaft, and is engaged to a drive gear through the motor's output gear, which is preferably a worm gear drive train.
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 assembly having 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 steps 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. A two-part linkage is rotatably engaged between the pivot rod and the step linkage and transfers downward forces on the step when retracted and when extended to the drive unit so that the step stays in its position.