Elevator Safety Chain Resistance Detection
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Solution Overview
Problem
Elevator safety switch arrangements can become worn over time, leading to potential short circuits or open connections that may not be detected by existing safety controllers, compromising the safety of elevator operations.
Innovation Solution
Incorporating a series connection of safety switches with first resistors and a comparator to measure resistance values, allowing for accurate detection of short circuits and open connections, and optionally using parallel second resistors and a bridging resistor to differentiate between proper function, short circuits, and open switches, with a safety controller that outputs status signals based on threshold comparisons.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If safety switch arrangements are connected in series without additional components, then the safety chain structure is simple, but the ability to detect short circuits and open connections deteriorates
Solution Approach 1:
The patent changes the electrical parameters of the safety switch arrangement by adding resistors in series with each safety switch. This modification enables the system to detect not only open connections but also short circuits by monitoring resistance changes, thereby improving detection accuracy without significantly complicating the overall safety chain structure.
Solution Approach 2:
The patent introduces resistors as intermediary elements between the safety switches and the control system. These resistors serve as mediators that enable the detection of safety switch status by creating measurable resistance changes when switches open or short circuit, thus improving measurement precision while maintaining relative structural simplicity.
2Duration of action of stationary object
If safety switch arrangements are worn over time, then the connection function may fail, but existing safety controllers cannot detect the failure
Solution Approach 1:
The patent implements preliminary detection capability by continuously monitoring the resistance of each safety switch arrangement through the added resistors. This allows the system to detect wear-related failures (open connections or short circuits) before they compromise safety, maintaining reliability throughout the extended service life of the elevator system.
Solution Approach 2:
The patent establishes a feedback mechanism where the control system continuously monitors the resistance values of safety switch arrangements and compares them against expected values. When wear causes resistance changes indicating open or shorted switches, the feedback loop triggers appropriate safety responses, ensuring reliable detection throughout the component's service life.
3Reliability
If resistors are added in series with safety switches, then short circuit detection capability is improved, but the device complexity increases
Solution Approach 1:
The patent improves short circuit detection by changing the electrical parameter (resistance) of each safety switch arrangement through the addition of series resistors. This allows the control system to distinguish between normal closed switches and shorted switches by monitoring resistance values, significantly improving detection reliability.
Solution Approach 2:
The patent applies segmentation by adding individual resistors to each safety switch arrangement rather than using a single complex detection system. This modular approach improves short circuit detection capability while keeping the increase in device complexity manageable, as each addition is a simple, independent component.
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 the accuracy of safety chain status detection, enabling the safety controller to reliably stop the elevator motor and engage brakes in case of short circuits or open switches, providing a more sophisticated safety monitoring system.
Implementation Method 1
The safety controller comprises a comparator for the determination of the status of the safety chain. The comparator is connected with or has a memory for storing at least one resistor reference value. The comparator is configured to output a safety chain status signal in dependence of the result of a comparison of a measured resistance value with the resistor reference value.
Data Source
AI summary
An elevator has a safety controller to which several safety switch arrangements are connected. The safety controller is configured to cause the stop of the elevator motor and the activation of the motor brakes. A comparator is provided in the safety controller for the determination of the status of the safety chain. The comparator is connected with a memory for storing at least one resistor reference value, which comparator is configured to output a safety chain status signal in dependence of comparison of a measured resistance value with the resistor reference value. Each of said safety switch arrangements includes at least one first resistor and a safety switch which are connected in series. The value of the first resistor is different in at least some safety switch arrangements, preferably in all safety switch arrangements. Each safety switch arrangement includes at least a second resistor connected in parallel with the safety switch, which second resistor has a higher value than the first resistor. The detection of a short circuit as well as of the opening of a safety switch arrangement are allowed.