Elevator Safety Circuit with Semiconductor Bridging

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Solution Overview

Problem

Conventional elevator installations face reliability issues due to the high number of switchings in electromechanical switches used for bridging over door contacts, which are classified as high-demand safety functions, leading to potential safety risks and increased maintenance costs.

Innovation Solution

The integration of electronic semiconductor switches, such as MOSFETs, for high-demand safety functions like door contact bridging, combined with a processor-controlled monitoring circuit and an electromechanical safety relay for redundancy and failsafe operation, ensuring the safety circuit remains active even in case of semiconductor switch failures.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If electromechanical switches are used for bridging over door contacts, then the safety function can be implemented, but the high number of switchings (more than 520,000 per year) reduces reliability and increases maintenance needs

Engineering Contradiction:

Improvereliability of door contact bridgingVSAvoidnumber of switchings per year

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The patent replaces electromechanical switches with electronic semiconductor switches (such as MOSFETs) for the door contact bridging function. This substitution eliminates mechanical wear and contact fatigue, allowing the system to handle millions of switching cycles without degradation. The electronic switches maintain the safety function while dramatically improving reliability and reducing maintenance requirements.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent changes the operating parameters of the switching mechanism by transitioning from mechanical contact-based switching to electronic field-effect switching. This parameter change enables the system to operate at much higher switching frequencies without the reliability penalties associated with mechanical wear, directly addressing the contradiction between high switching volume and reliability.

Inventive Principle:

Principle #35Parameter changes

2Productivity

If semiconductor switches are used to replace electromechanical switches, then the number of switchings can be increased without reliability loss, but the risk of short-circuit failures increases

Engineering Contradiction:

Improvenumber of switchings per yearVSAvoidrisk of short-circuit

Core Design Contradiction:

ProductivityVSObject-affected harmful factors

Solution Approach 1:

The patent implements beforehand cushioning by incorporating monitoring circuits that continuously detect the operational state of semiconductor switches. These monitoring circuits identify potential failures or abnormal conditions before they lead to dangerous short-circuit failures. The system prepares compensatory measures in advance, such as triggering backup safety mechanisms or alerting operators, thereby cushioning against the inherent risks of semiconductor switch failures.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

Solution Approach 2:

The patent employs feedback mechanisms through monitoring circuits that continuously assess the state of semiconductor switches. This feedback loop detects anomalies such as leakage currents or abnormal voltage drops that indicate impending failures. By receiving real-time feedback about the health of the semiconductor components, the system can take corrective action before actual failure occurs, mitigating the harmful effects of semiconductor switch risks.

Inventive Principle:

Principle #23Feedback

3Reliability

If semiconductor switches are used for high-demand safety functions, then switching reliability improves, but the complexity of the safety circuit increases due to monitoring requirements

Engineering Contradiction:

Improvereliability of high-demand safety functionVSAvoidcomplexity of safety circuit

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent applies universality by designing monitoring circuits that serve multiple functions: they monitor the operational status of semiconductor switches, detect potential failures, and trigger appropriate safety responses. These monitoring circuits are integrated into the existing safety architecture rather than being separate add-on systems, allowing them to perform multiple safety-related tasks within a unified structure. This multi-functionality approach increases reliability while controlling the overall complexity increase.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Data Source

PatentUS9061863B2Safety circuit in an elevator system

Publication Date: 2015.06.23 INVENTIO AG

AI summary

A safety circuit in an elevator system includes at least one series connection of safety-relevant contacts that are closed during trouble-free operation of the elevator system, wherein in the case of certain operating conditions in which at least one contact is opened, the at least one contact can be bridged by semiconductor switches, and wherein the semiconductor switches are controlled by at least one processor and monitored by at least one monitoring circuit for short circuits. At least one electromechanical relay circuit, having relay contacts connected in series with the contacts of the bridged series connection can be controlled by the at least one processor and the bridgable series connection can be interrupted by the relay contacts in the case of short-circuiting of the semiconductor switches.