Polygon Rotor Attachment Device for Bi-directional Torque

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Existing attachment devices for turbomachinery rotors, such as threaded couplings, are unidirectional and costly to manufacture, and require special tooling for polygon tapers, making them impractical for bi-directional torque transmission in soft or brittle materials.

Innovation Solution

A non-tapered polygon drive collar is used, fixedly and coaxially mounted between the rotor and drive shaft, allowing for bi-directional torque transmission without the need for hub inserts or oversized shafts, and can be manufactured using standard machine tools.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If threaded couplings are used to transmit high torque loads, then torque transmission capability is improved, but the coupling becomes unidirectional and manufacturing costs increase

Engineering Contradiction:

Improvetorque transmission capabilityVSAvoidmanufacturing cost

Core Design Contradiction:

StrengthVSEase of manufacture

Solution Approach 1:

The coupling system is segmented into a drive shaft with external polygonal features, a separate polygonal collar, and a rotor with internal polygonal features. This segmentation allows each component to be manufactured using standard machine tools through conventional processes like milling and turning, eliminating the need for expensive specialized tooling while maintaining high torque transmission capability through the distributed contact surfaces of the polygonal interface

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The invention changes the geometric parameters of the coupling interface from traditional circular or tapered forms to a polygonal configuration with multiple flat surfaces. This parameter change enables bi-directional torque transmission while allowing manufacturing using standard machine tools, as the polygonal surfaces can be created through conventional milling and turning operations rather than requiring specialized tapered grinding equipment

Inventive Principle:

Principle #35Parameter changes

2Reliability

If polygon tapers are used for bi-directional torque transmission, then torque carrying capability is improved, but special tooling is required making repair difficult

Engineering Contradiction:

Improvebi-directional torque carrying capabilityVSAvoidmanufacturability

Core Design Contradiction:

ReliabilityVSEase of repair

Solution Approach 1:

Instead of using tapered polygon surfaces that require specialized grinding equipment, the invention inverts the approach by using straight-sided polygonal surfaces that can be manufactured with standard milling and turning tools. This inversion maintains the bi-directional torque carrying capability through the multiple flat contact surfaces while making the components manufacturable and repairable in ordinary machine shops

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The polygonal collar is designed as a separate, relatively simple component that can be manufactured economically using standard machine tools. If wear or damage occurs, the collar can be replaced rather than requiring expensive reconditioning of the shaft or rotor, making the system more maintainable and cost-effective for repair operations

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

3Strength

If hub inserts or oversized shafts are used to transmit torque through soft or brittle materials, then torque transmission is improved, but weight and cost increase

Engineering Contradiction:

Improvetorque transmission through soft/brittle materialsVSAvoidweight

Core Design Contradiction:

StrengthVSWeight of moving object

Solution Approach 1:

The polygonal interface concentrates the torque transmission function at the localized mating surfaces of the drive shaft, collar, and rotor. The collar acts as a localized torque transmission element with optimized polygonal contact surfaces, allowing the rotor hub and shaft to maintain their original materials and dimensions without requiring heavy inserts or oversized construction throughout the entire assembly

Inventive Principle:

Principle #3Local quality

Data Source

PatentUS8052397B2Polygon rotor attachment device

Publication Date: 2011.11.08 FLOWSERVE PTE LTD

AI summary

A rotor and shaft assembly for turbomachinery has a polygon shaped drive collar interposed between corresponding polygonal mating surfaces of a drive shaft and a rotor hub. The mating surfaces of the polygon collar, the drive shaft and the rotor hub may be sized both axially and radially for required torque transmission without the need for hub inserts or oversized shafts. The polygon drive collar is manufacturable using standard machine tools such as lathes and end mills that remove metal in a tool path following not more than two axes of simultaneous movement. A shaft end assembly secures the rotor and drive collar to the shaft.