Elevator Wire Rope Coupling as a Mechanical Fuse for Cable Overload

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Solution Overview

Problem

Conventional elevator systems face challenges in safely managing tensile forces without causing permanent damage to components when the compensating cable encounters obstructions, as existing mechanical fuses like 'S' hooks may not effectively prevent damage to the system.

Innovation Solution

A wire rope coupling system with a cable having a tensile strength less than the elastic deformation limit of the compensating cable, incorporating a pair of thimbles and compression sleeves, and a switch assembly that activates an alarm upon cable breakage to prevent damage to other components.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a mechanical fuse like an 'S' hook is used to release before reaching tensile forces sufficient to inflict permanent damage, then the compensating cable is protected from permanent damage, but the system lacks reliability in ensuring the fuse releases at the correct moment and may not prevent damage to other components

Engineering Contradiction:

Improvereliability of mechanical fuseVSAvoiddamage to system components

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent changes the critical parameter from the mechanical strength of an 'S' hook to the tensile strength of a wire rope coupling cable. By carefully selecting the cable's tensile strength to be less than the elastic deformation limit of the compensating cable, the system achieves reliable failure at a predetermined load level, ensuring the compensating cable is protected while providing consistent, predictable performance.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The wire rope coupling cable is designed as a disposable sacrificial component with lower tensile strength than the compensating cable. When excessive tensile forces occur, this cable breaks first, acting as a mechanical fuse that protects more expensive and critical system components. The cable is replaced after each failure event, ensuring continuous safety.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

2Strength

If the cable tensile strength is set below the elastic deformation limit of the compensating cable, then the compensating cable is protected from permanent damage, but the wire rope coupling cable may break prematurely under normal operational loads

Engineering Contradiction:

Improveprotective strength of mechanical fuseVSAvoidreliability of wire rope coupling

Core Design Contradiction:

StrengthVSReliability

Solution Approach 1:

The patent incorporates a switch assembly that provides feedback when the wire rope coupling cable breaks. The switch is positioned to be activated by the breaking cable, which then triggers an alarm or shuts down the elevator system. This feedback mechanism ensures that normal operational loads never cause premature breaking, as the system would be shut down upon any failure event, allowing for inspection and replacement before further operation.

Inventive Principle:

Principle #23Feedback

3Reliability

If a wire rope coupling system with switch assembly is implemented, then system safety and maintenance scheduling are improved, but the device complexity increases

Engineering Contradiction:

Improvesafety of elevator systemVSAvoidcomplexity of wire rope coupling system

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The wire rope coupling system integrates multiple functions into a single assembly: the cable provides mechanical coupling and acts as a mechanical fuse, the thimbles provide structural support and cable routing, the compression sleeves provide secure attachment, and the switch assembly provides failure detection and system shutdown. This multi-functionality reduces the need for separate safety devices while improving overall system safety and maintenance scheduling.

Inventive Principle:

Principle #6Universality (Multi-functionality)

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 wire rope coupling system acts as a mechanical fuse, ensuring the cable fails before reaching the compensating cable's elastic deformation point, thereby preventing damage and providing high fatigue resistance and wear attributes for maintenance scheduling.

Implementation Method 1

The compensating cable has an elastic deformation limit. The cable has a tensile strength that is less than the elastic deformation limit of the compensating cable.

Methodology Applied

Scientific EffectElastic deformation: Elasticity

Data Source

PatentUS11220413B2Wire rope coupling for elevator

Publication Date: 2022.01.11 DRAKA ELEVATOR PRODS

AI summary

An elevator assembly includes an elevator cabin, a counterweight, a compensating cable and a means for suspending the compensating cable from the elevator cabin. The compensating cable includes a proximal end and a distal end. The proximal end is coupled with the elevator cabin and the distal end is coupled with the counterweight. The means for suspending the compensating cable is coupled with the elevator cabin and is further coupled with the compensating cable adjacent the proximal end of the compensating cable. The compensating cable has an elastic deformation limit. The means for suspending the compensating cable has a tensile strength that is less than the elastic deformation limit of the compensating cable.