Fiber-Reinforced Screw Rotor Assembly for Lightweight Torque Transfer

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Solution Overview

Problem

Conventional screw rotors made from cast iron or steel are labor-intensive and costly to manufacture, require significant material wastage, and are heavy due to their material density, which complicates achieving the necessary fine tolerances for proper function in fluid-injected compressors, expanders, and vacuum pumps.

Innovation Solution

A screw rotor made from fiber-reinforced polymer with a shaft and rotor body, where the shaft features elements that prevent axial and rotational movement, allowing for simpler manufacturing through injection molding, reducing the need for extensive finishing processes and minimizing material loss, and providing a lighter, more corrosion-resistant alternative.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If cast iron or steel is used for the screw rotor, then the rotor has sufficient strength and rigidity, but the weight increases significantly

Engineering Contradiction:

Improverotor strengthVSAvoidrotor weight

Core Design Contradiction:

StrengthVSWeight of moving object

Solution Approach 1:

The patent uses fiber-reinforced polymer composite materials for the screw rotor, combining polymer matrix with reinforcing fibers (such as carbon fibers, glass fibers, or aramid fibers) to achieve both lightweight properties and sufficient mechanical strength. This composite approach allows the rotor to maintain required strength while significantly reducing weight compared to traditional metal materials.

Inventive Principle:

Principle #40Composite materials

2Strength

If cast iron or steel is used for the screw rotor, then the rotor has high strength, but corrosion resistance deteriorates

Engineering Contradiction:

Improverotor strengthVSAvoidcorrosion resistance

Core Design Contradiction:

StrengthVSObject-affected harmful factors

Solution Approach 1:

The polymer matrix in the composite material provides inherent corrosion resistance while the fiber reinforcement maintains structural strength. This combination creates a rotor that is both strong and resistant to corrosion, eliminating the corrosion issues associated with traditional metal rotors.

Inventive Principle:

Principle #40Composite materials

3Manufacturing precision

If conventional casting and finishing processes are used, then the rotor achieves required tolerances, but manufacturing time increases significantly

Engineering Contradiction:

Improvescrew rotor tolerancesVSAvoidmanufacturing speed

Core Design Contradiction:

Manufacturing precisionVSProductivity

Solution Approach 1:

The injection molding process forms the screw rotor with pre-defined precise geometry directly during manufacturing, eliminating the need for subsequent finishing operations. The mold cavities are designed to produce the final screw profile and dimensional tolerances in one step, achieving both precision and high productivity.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent replaces traditional mechanical finishing processes (grinding, filing, milling) with a molding process that creates the final geometry through material injection into precision-machined mold cavities. This substitution of manufacturing methodology achieves equivalent or better tolerances with significantly reduced processing time.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

4Manufacturing precision

If conventional casting and finishing processes are used, then the rotor achieves required tolerances, but manufacturing cost increases

Engineering Contradiction:

Improvescrew rotor tolerancesVSAvoidmanufacturing cost

Core Design Contradiction:

Manufacturing precisionVSEase of manufacture

Solution Approach 1:

The injection molding process achieves the required dimensional tolerances and surface finish directly during the primary manufacturing operation, eliminating multiple secondary finishing operations. This consolidation of manufacturing steps reduces labor costs, machine tool usage, and overall manufacturing complexity.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent combines multiple manufacturing operations (forming, finishing, and tolerance achievement) into a single injection molding process. The mold design integrates all geometric features and tolerance requirements, allowing the rotor to be produced in one operation rather than through sequential processing steps.

Inventive Principle:

Principle #5Merging (Combining)

5Ease of manufacture

If conventional casting processes are used, then the rotor can be manufactured, but material waste increases due to extensive finishing operations

Engineering Contradiction:

Improvemanufacturing feasibilityVSAvoidmaterial waste

Core Design Contradiction:

Ease of manufactureVSLoss of substance

Solution Approach 1:

The injection molding process creates the screw rotor with the final precise geometry and dimensions directly, eliminating the need for material removal through finishing operations. The polymer material is deposited only where needed in the mold cavity, achieving near-net-shape manufacturing with minimal waste.

Inventive Principle:

Principle #10Preliminary action

Data Source

PatentUS12129850B2Screw rotor and method for manufacturing such screw rotor

Publication Date: 2024.10.29 ATLAS COPCO AIRPOWER NV

AI summary

A screw rotor is made out of polymer. The screw rotor includes a shaft with a rotor body on it. The polymer of the shaft is reinforced with fibers. The shaft features elements that engage the rotor body or corresponding elements on the rotor body, such that the elements prevent an axial and/or rotational movement of the shaft with respect to the rotor body.