Elevator Tension Member Monitoring Circuit
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Solution Overview
Problem
The need for efficient electricity-based monitoring techniques for coated steel belts in elevator systems arises due to the difficulty in visually inspecting the degradation of steel cord tension members, which are concealed by polyurethane jackets, necessitating innovative circuit arrangements to assess the strength and condition of these members without causing corrosion.
Innovation Solution
A circuit arrangement that applies electric signals with a low duty ratio and strategically couples non-adjacent tension members to form loops, minimizing corrosion risks by maintaining maximum distance between energized members and controlling signal polarity to prevent ion migration, allowing for effective monitoring of the tension members' condition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If electric signals are applied continuously to tension members for monitoring, then monitoring accuracy is improved, but corrosion of tension members increases
Solution Approach 1:
The patent applies periodic pulsed electric signals instead of continuous signals. The duty cycle is controlled to be less than 10% (preferably less than 1%), meaning the signal is active only during brief intervals and dormant for extended periods. This periodic application allows monitoring measurements to be taken while minimizing the time tension members are exposed to electric current, thereby reducing electrochemical corrosion while maintaining measurement capability.
2Productivity
If electric signals are applied to adjacent tension members simultaneously, then monitoring efficiency is improved, but electric field induced corrosion increases
Solution Approach 1:
The patent segments the monitoring process by applying electric signals to non-adjacent tension members alternately rather than to all members simultaneously. This segmentation strategy divides the set of tension members into groups that are monitored at different time intervals, preventing the formation of electric fields between adjacent members while still achieving comprehensive monitoring coverage through systematic sequencing.
3Measurement precision
If high amplitude electric signals are used for monitoring, then signal detection capability is improved, but corrosion and degradation of tension members increases
Solution Approach 1:
The patent optimizes multiple parameters of the electric signal simultaneously: using low amplitude voltages (e.g., less than 5V, preferably less than 1V), controlling duty cycle to be less than 10% (preferably less than 1%), and selecting frequencies in the range of 1Hz to 1kHz. These parameter changes collectively enable sufficient signal detection for monitoring while minimizing electrochemical reactions and degradation of the tension members.
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 approach enables efficient and corrosion-minimized monitoring of elevator load bearing members, ensuring accurate assessment of tension member strength and condition while reducing the risk of degradation, thereby extending the service life of coated steel belts.
Implementation Method 1
strategically applying electric signals only to tension members that are not adjacent to each other to avoid establishing an electric field between the spaced apart tension members
Implementation Method 2
monitoring the resistance of the tension members provides an indication of the condition of the tension members
Data Source
AI summary
An elevator load bearing member (30) monitoring device includes a controller (42) that applies a selected electrical signal to tension members (32) of the load bearing member (30). In one example, connectors (40) are associated with ends of the load bearing member (30) to establish an electrical interface between the controller (42) and the tension members (32). The connectors (40) facilitate establishing electrical circuit loops along the tension members (32) such that only non-adjacent tension members are energized at a selected time. A variety of circuit configurations are disclosed. The applied electrical signal in one example has a potential that is negative compared to a ground potential of a hoistway in which the elevator belt is used. In another example, the electrical signal comprises a plurality of pulses and has a duty cycle that is on the order of about one percent.