People Conveyor Handrail Safety Switch Assembly
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Solution Overview
Problem
Existing people conveyor systems, such as escalators and moving walkways, face risks of human body parts, particularly fingers, getting jammed between the moving handrail and stationary handrail exit/entry portions, leading to potential injuries and unnecessary shut-offs.
Innovation Solution
A safety switch assembly with touch sensors at handrail exit/entry portions that detect approaching human body parts, triggering an alarm and reducing handrail speed or completely stopping it to prevent jamming, while minimizing conveyor shut-offs by allowing early detection and intervention.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a mechanical safety switch is provided at the handrail exit/entry portion to stop the handrail when activated, then the risk of body parts being trapped is reduced, but the conveyor experiences unnecessary shut-off times
Solution Approach 1:
The capacitive touch sensor detects the approach of a body part (such as a finger) to the handrail exit/entry portion before the mechanical safety switch is activated. This preliminary detection allows the system to prepare for potential activation and reduces false triggering by distinguishing between intentional contact and accidental approach, thereby reducing unnecessary shut-off times while maintaining safety
Solution Approach 2:
The touch sensor provides feedback about the state of the handrail exit/entry portion to the control system. This feedback mechanism allows the control system to make informed decisions about whether to activate the safety switch, reducing unnecessary shutdowns while ensuring safety when actually needed
2Reliability
If the handrail speed is reduced when a body part is detected by the touch sensor, then the risk of jamming is minimized, but the conveying efficiency is reduced
Solution Approach 1:
The handrail speed is dynamically adjusted based on the detection state. When a body part is detected by the touch sensor, the handrail speed is temporarily reduced to prevent jamming. Once the body part is removed and the sensor no longer detects contact, the speed is restored to normal. This dynamic adjustment minimizes safety risks while maintaining conveying efficiency during normal operation
Solution Approach 2:
The touch sensor continuously monitors the handrail exit/entry portion at periodic intervals. This continuous monitoring allows the system to detect body parts and adjust speed only when necessary, rather than maintaining reduced speed continuously, thus preserving conveying efficiency while ensuring safety
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 operational security by preventing human body parts from being trapped and reduces unnecessary conveyor shut-offs by allowing early detection and resolution of dangerous situations without complete stoppage.
Implementation Method 1
The sensor, without contact, registers variations in an electrical and/or magnetic field
Data Source
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AI summary
A people conveyor (2) comprises two landing areas (4, 6) located at two opposing ends of the people conveyor (2); a movable conveying element (8) extending between the two landing areas (4, 6) and configured for conveying passengers between the two landing areas (4, 6); a handrail (12) extending parallel to the conveying element between the two landing areas and configured for moving with the conveying element (8); a handrail exit/entry portion (19) located at one of the landing areas (4, 6) and configured for receiving a return portion of the handrail (12); and a safety switch assembly (31) provided at the handrail exit/entry portion (19) and configured for stopping the handrail (12) when activated. The safety switch assembly (31) comprises at least one sensor surface (27, 29) providing a touch sensor for detecting any part of a human body, in particular a finger, approaching and/or touching at least one of the at least one sensor surfaces (27, 29).