Elevator Counterweight Derailment Detection via Optical Distance

Solution Overview

Problem

Existing derailment detection devices for elevator counterweights pose a risk of electric shock to maintenance workers due to the use of conductive wires and are ineffective when rust forms on these wires, preventing reliable detection.

Innovation Solution

A derailment detection device using a wire suspended parallel to the guide rail with a cylindrical member and photoelectric sensor to measure the distance to a detection target, eliminating the need for conductive wires and enabling detection even with rust, and incorporating a cut-off circuit to stop the elevator in case of derailment or wire breakage.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conductive wires or trolley lines are used for derailment detection, then derailment detection function is achieved, but maintenance workers are exposed to electric shock risk

Engineering Contradiction:

Improvederailment detection reliabilityVSAvoidelectric shock risk to maintenance workers

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent replaces the electrical contact-based detection system with an optical detection system. A photoelectric sensor mounted on the guide rail detects the position of a reflective target attached to the counterweight, eliminating the need for conductive wires or trolley lines that pose electric shock risks to maintenance workers.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent introduces a reflective target as an intermediary between the photoelectric sensor and the counterweight. This intermediary enables non-contact optical detection of the counterweight's position and derailment status without requiring direct electrical connections in the hoistway.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If conductive wires are used for derailment detection, then detection function is achieved, but rust formation on wires prevents reliable detection

Engineering Contradiction:

Improvederailment detection reliabilityVSAvoiddetection accuracy affected by rust

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The patent replaces the electrical contact-based detection system with an optical detection system. A photoelectric sensor mounted on the guide rail detects the position of a reflective target attached to the counterweight, eliminating the need for conductive wires or trolley lines that pose electric shock risks to maintenance workers.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent introduces a reflective target as an intermediary between the photoelectric sensor and the counterweight. This intermediary enables non-contact optical detection of the counterweight's position and derailment status without requiring direct electrical connections in the hoistway.

Inventive Principle:

Principle #24Intermediary (Mediator)

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

The solution safely detects counterweight derailment without exposing maintenance workers to live wires and maintains system safety by stopping the elevator in case of derailment or wire failure, while being effective even with rust on the wire.

Implementation Method 1

a photoelectric sensor which is provided on a fixed surface so as to be opposed to a lower surface of the detection target and measures a distance to the detection target

Methodology Applied

Scientific EffectPhotoelectric effect: Photoelectric Effect

Data Source

PatentUS11511966B2Derailment detection device for a counterweight of an elevator

Publication Date: 2022.11.29 MITSUBISHI ELECTRIC CORP

AI summary

Provided is a derailment detection device for a counterweight of an elevator comprising: a wire suspended in parallel with a guide rail for the counterweight; a cylindrical member which has an arm portion connected to the counterweight and allows the wire to pass therethrough in a vertical direction; a detection target connected to a lower end of the wire; a photoelectric sensor which is provided on a fixed surface so as to be opposed to a lower surface of the detection target and measures a distance to the detection target; and a detection circuit electrically connected to the photoelectric sensor. The detection circuit detects that the counterweight runs off the guide rail based on the distance from the photoelectric sensor to the detection target.