Thermal Barrier Roller for Elevator Door Fire Safety

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Solution Overview

Problem

Elevator door assemblies face challenges in maintaining fire safety during building fires due to heat transfer through convective, conductive, and radiated heat, which can soften and melt the polymer tire material on rollers, potentially leading to thermal shortcuts and failure in fire tests.

Innovation Solution

The implementation of a thermal barrier between the tire material and the rim or hub of the rollers, as well as between the rail and the header, using low thermal conductivity materials like ceramics or composites to inhibit heat transfer, thereby reducing the risk of polymer melting and maintaining the structural integrity of the door assembly during fires.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If roller components (rim and hub) are made from materials with high thermal conductivity to ensure structural strength, then the roller can maintain its mechanical integrity, but heat transfer to the tire material increases causing melting and fire test failure

Engineering Contradiction:

Improvestructural integrity of rollerVSAvoidheat transfer to tire material

Core Design Contradiction:

StrengthVSObject-affected harmful factors

Solution Approach 1:

A thermal barrier layer is introduced as an intermediary between the roller components (rim and hub) and the tire material. This barrier prevents direct heat conduction from the metal roller parts to the polymer tire, eliminating the thermal pathway that causes melting while maintaining the mechanical strength of the roller structure.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The roller assembly is constructed as a composite structure combining metal components (rim and hub for strength) with a thermal barrier material layer (for heat protection) and polymer tire material (for friction and grip). This multi-material composite approach allows each material to perform its optimal function without the drawbacks of using a single material for all purposes.

Inventive Principle:

Principle #40Composite materials

2Ease of manufacture

If the door assembly uses standard roller components without thermal barriers to simplify construction, then manufacturing and installation are easier, but the tire material softens and melts under fire conditions leading to visible flames

Engineering Contradiction:

Improveconstruction simplicityVSAvoidfire safety performance

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The thermal barrier layer serves as a protective intermediary that can be applied to standard roller components, maintaining ease of manufacture while dramatically improving fire safety. The barrier can be applied as a coating or bonded layer during the manufacturing process without requiring complete redesign of the roller assembly.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The thermal barrier modifies the thermal parameters (heat conduction properties) of the roller assembly without changing its mechanical parameters (strength, weight, dimensions). This allows the same roller structure to perform both mechanically and thermally protected functions by changing only the thermal conductivity parameter through the barrier layer.

Inventive Principle:

Principle #35Parameter changes

3Reliability

If thermal barriers are added to roller components to prevent heat transfer, then fire safety is improved, but the device complexity increases

Engineering Contradiction:

Improvefire safetyVSAvoidroller assembly structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The thermal barrier is applied locally only where heat transfer occurs - specifically between the rim/tire interface and hub/tire interface areas of the roller. This localized application provides fire protection exactly where needed without adding unnecessary complexity to the entire roller assembly structure.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

Inventive Principle:

Principle #40Composite materials

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 use of thermal barriers effectively reduces heat transfer, preventing the melting of tire materials and ensuring the door assembly's robustness, thus enhancing its ability to pass fire safety tests by maintaining the absence of visible flames and ensuring safe operation during elevated temperatures.

Implementation Method 1

The roller is at least partially covered with a thermal barrier between the tire material and at least one of the rim and the hub to prevent heat transfer to the tire material

Methodology Applied

Scientific EffectThermal insulation: Thermal Insulation

Data Source

PatentUS8443574B2Intumescent thermal barrier from hub to tire

Publication Date: 2013.05.21 OTIS ELEVATOR CO

AI summary

A door assembly has a door header mounted on a frame defining a doorway, a door movably supported on the frame, and a track including at least one supporting surface along at least one side of the track. The track is secured to the door header. The assembly has at least one roller that is adapted to roll along the track. The roller has a rim portion adjacent a hub portion, and a tire material surrounding the rim portion that contacts the track. The roller is at least partially covered with a thermal barrier between the tire material and at least one of the rim portion and the hub portion to prevent heat transfer to the tire material.