Composite Belt Sheave Molding for Smooth, Low-Cost Conveyor Use

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Solution Overview

Problem

The manufacturing of belt sheaves, particularly idler sheaves, for passenger conveyor systems is costly and requires multiple processing steps, and existing materials like steel often need additional machining for smooth surfaces and reduced electrostatic charge generation.

Innovation Solution

Disc gate injection moulding of glass or carbon fibre reinforced polymers to produce a cylindrical sleeve with improved fibre orientation and a smooth outer surface, reducing the need for post-production machining and minimizing electrostatic charges.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If steel is used for belt sheaves with traditional manufacturing methods, then mechanical strength is sufficient, but manufacturing cost increases and multiple processing steps are required

Engineering Contradiction:

Improvemanufacturing process simplicityVSAvoidnumber of processing steps

Core Design Contradiction:

Ease of manufactureVSDevice complexity

Solution Approach 1:

The patent uses glass fibre reinforced polymer composite material to manufacture belt sheaves, replacing traditional steel. This composite material approach allows the sheave to be manufactured in a single injection molding process, eliminating multiple machining steps while maintaining sufficient mechanical strength for the application.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The patent replaces traditional mechanical machining processes with injection molding technology. Instead of cutting, drilling, and finishing steel components through multiple machining operations, the sheave is formed directly through injection molding of composite material, significantly simplifying the manufacturing process.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Manufacturing precision

If steel sheaves are manufactured with smooth surfaces, then belt damage is reduced, but additional machining and coating steps are required

Engineering Contradiction:

Improvesurface smoothnessVSAvoidnumber of post-production steps

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The patent incorporates surface smoothing directly into the injection molding process itself. The mold cavity is designed with the final desired surface finish, and the injection molding process produces the sheave with the required surface smoothness immediately, eliminating the need for post-production machining or coating steps.

Inventive Principle:

Principle #10Preliminary action

3Ease of manufacture

If traditional injection molding is used, then production is simpler, but weld lines appear and tensile strength decreases

Engineering Contradiction:

Improvemanufacturing simplicityVSAvoidtensile strength

Core Design Contradiction:

Ease of manufactureVSStrength

Solution Approach 1:

The patent optimizes injection molding parameters including injection pressure, injection speed, and mold temperature to control the flow pattern and eliminate weld line formation. By carefully adjusting these parameters, the process achieves both manufacturing simplicity and high tensile strength in the resulting sheave component.

Inventive Principle:

Principle #35Parameter changes

4Reliability

If steel sheaves are used, then structural integrity is maintained, but electrostatic charge generation increases causing belt degradation

Engineering Contradiction:

Improvestructural integrityVSAvoidelectrostatic charge generation

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

The patent uses a homogeneous polymer composite material structure that inherently produces minimal electrostatic charges. The glass fibre reinforced polymer provides uniform electrical properties throughout the sheave, eliminating the high electrostatic charge generation problem associated with steel, while maintaining structural integrity through the reinforced composite design.

Inventive Principle:

Principle #33Homogeneity

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

This method results in a sheave with enhanced tensile strength, reduced roughness, and lower production costs, while maintaining mechanical properties suitable for high-load applications in elevator systems.

Implementation Method 1

heating the material to a temperature above the melting point of the polymer

Methodology Applied

Scientific EffectMelting: Melting

Implementation Method 2

The cylindrical sleeve is cooled to a temperature below the melting point of the polymer such that the cylindrical sleeve contracts

Methodology Applied

Scientific EffectThermal contraction: Thermal Contraction

Data Source

PatentEP4112526B1Belt sheave for passenger conveyor systems

Publication Date: 2024.10.30 OTIS ELEVATOR CO

Figure 1A
Figure 1B~1C
Figure 2A~2B

AI summary

A sheave (100) for a passenger conveyor system is provided. The sheave (100) comprises a sheave axis (150) about which the sheave (100) rotates; a cylindrical sleeve (105); and a bearing (120a, 120b) centred on and arranged to rotate about the sheave axis (150). The cylindrical sleeve (105) comprises an outer surface (110) comprising a groove (155) arranged to receive a belt; and an inner surface (115) defining a cylindrical cavity (122) centred on the sheave axis (150). The bearing (120a, 120b) includes an outer race (125a), an inner race (130a) and one or more rolling elements (135a) therebetween, wherein the outer race (125a) comprises a protrusion (140) arranged to hold the bearing (120a, 120b) within the cylindrical cavity (122) due to engagement between the protrusion (140) and the inner surface of the cylindrical sleeve (115).