Wheelchair Lift Roll Stop Interlock with Pre-Motion Sensor
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Solution Overview
Problem
Conventional wheelchair lift outer roll stops often move before detecting an object, creating unsafe conditions for occupants, as they lack pre-motion detection of loads, which can lead to unexpected lift movements.
Innovation Solution
Incorporating a sensor assembly with sensitized strips and a control circuit that detects objects on the top plate before allowing the outer roll stop to move, ensuring the lift only operates when no load is present, utilizing a metal top plate and biasing arrangement to enhance sensitivity and reliability, and a flange for water and debris egress to prevent false readings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional roll stop interlock is used that remains deployed during lift operation until a predetermined height is reached, then the lift can operate without pre-motion detection, but the roll stop may move before detecting an object creating unsafe conditions
Solution Approach 1:
The sensor is positioned between the top plate and base to detect objects before the roll stop moves, enabling preliminary detection of loads. The control circuit receives sensor signals before motion commands are executed, allowing the system to prepare for potential load conditions in advance and prevent unsafe movements.
Solution Approach 2:
The sensor provides continuous feedback about object presence on the top plate to the control circuit. This feedback mechanism allows the system to monitor the roll stop area in real-time and adjust operation based on detected conditions, improving safety through active monitoring rather than passive detection.
2Device complexity
If the roll stop is positioned to allow easy access but without pre-motion detection, then the structure remains simple, but unexpected lift movements can occur when objects are on the roll stop
Solution Approach 1:
The mechanical detection system is replaced with a sensor-based detection system. Instead of relying solely on mechanical interlocks that detect load after movement begins, an electronic sensor detects objects before motion occurs, substituting mechanical detection with electronic sensing to improve reliability.
Solution Approach 2:
The sensor acts as an intermediary between the physical object on the roll stop and the control system. It translates physical presence into electrical signals that the control circuit can process, enabling the system to predict load presence before movement occurs without requiring complex mechanical prediction mechanisms.
3Reliability
If the sensor is positioned between the top plate and base for pre-motion detection, then safety is improved, but the device complexity increases due to additional sensor assembly
Solution Approach 1:
The sensor assembly is integrated into the existing roll stop structure by positioning it between the top plate and base. This merging approach incorporates the detection function into the existing components rather than adding completely separate systems, reducing overall complexity while maintaining detection accuracy.
Solution Approach 2:
The space between the top plate and base serves multiple functions: it provides structural support for the roll stop and simultaneously houses the sensor for object detection. This multi-functionality reduces the need for additional components and simplifies the overall device structure while achieving improved detection capabilities.
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
Ensures the safety of occupants by preventing lift movement until an object is detected, enhancing the reliability and robustness of the outer roll stop through pre-motion detection and reducing the risk of false triggers.
Implementation Method 1
The sensor may be a sensitized strip having first and second conductive elements, with the first and second conductive elements configured to engage each other when the sensitized strip is compressed.
Implementation Method 2
The top plate may be biased to the first position by a biasing arrangement. The biasing arrangement may include one or more compression springs.
Data Source
AI summary
An outer roll stop for a wheelchair lift includes a base having a leading end, a trailing end, a top surface, and a bottom surface positioned opposite from the top surface, a top plate secured to the base, with the top plate moveable relative to the base, and an interlock assembly comprising a sensor positioned between the top plate and the base, with the sensor having a first state and a second state. The sensor moving from the first state to the second state when an object is positioned on the top plate. The sensor is configured to detect when an object is positioned on the top plate prior to motion of the outer roll stop.