Eccentric Tool Holder for Pipe Threading

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Solution Overview

Problem

Conventional machining methods for large pipes face challenges with power requirements, vibration issues, and reduced machining accuracy, particularly in maintaining cutting capability as the tool's revolution radius changes during threading.

Innovation Solution

A machining unit with a rotatable eccentric rotational section and a cutting-edge-orientation correcting mechanism that adjusts the tool's orientation by spinning the tool holder, allowing the cutting edge to maintain proper alignment with the rotation center regardless of the revolution radius, enabling flexible machining of various pipe diameters.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If the revolution radius of the tool is changed to machine pipes of various diameters, then the adaptability is improved, but the cutting capability deteriorates because the cutting edge cannot maintain proper orientation with the rotation center

Engineering Contradiction:
Improveability to machine various pipe diametersVSAvoidcutting capability
Core Design Contradiction:
Adaptability or versatilityVSManufacturing precision

Solution Approach 1:

The tool holder is designed to be rotatable about its own axis in addition to the eccentric rotational section's rotation. This dynamic configuration allows the tool holder to adjust its orientation independently, enabling the cutting edge to maintain proper alignment with the rotation center regardless of the revolution radius, thus preserving cutting capability while machining various pipe diameters

Inventive Principle:
Principle #15Dynamics

Solution Approach 2:

The tool holder serves dual functions: it supports the tool for cutting operations and simultaneously acts as a rotating mechanism to correct the cutting edge orientation. This multi-functionality allows the same component to adapt to different machining requirements without sacrificing cutting performance

Inventive Principle:
Principle #6Universality (Multi-functionality)

2Manufacturing precision

If a large lathe is used to machine large diameter pipes, then the cutting capability is maintained, but the device complexity and cost increase

Engineering Contradiction:
Improvecutting capabilityVSAvoidmachine tool size
Core Design Contradiction:
Manufacturing precisionVSDevice complexity

Solution Approach 1:

Instead of rotating the workpiece (pipe) as in conventional lathe machining, the invention inverts the approach by keeping the workpiece stationary and rotating the tool about an eccentric axis. This inversion allows a smaller, more compact machine tool to achieve the same machining capability, reducing device complexity and cost while maintaining cutting performance

Inventive Principle:
Principle #13The other way round (Inversion)

Solution Approach 2:

The eccentric rotational section acts as an intermediary mechanism that translates the rotation of the main spindle into the desired tool motion. This intermediary allows the system to achieve complex tool paths and orientations without requiring a large, complex lathe structure, thereby reducing overall device complexity

Inventive Principle:
Principle #24Intermediary (Mediator)

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 solution ensures consistent cutting capability and improved machining accuracy by maintaining the cutting edge's orientation with the rotation center, even as the revolution radius changes, effectively addressing the limitations of existing methods.

Implementation Method 1

an eccentric rotational section that is disposed on the main spindle section and that is rotatable about an eccentric axis, the eccentric axis being located eccentrically at any distance in a radial direction of the main spindle section from a rotation center of the main spindle section

Methodology Applied
Scientific EffectEccentric rotation: Eccentric

Implementation Method 2

a cutting edge of the tool 143 revolves along an outer circumferential surface of the pipe 101 and, in conjunction therewith, the main spindle section 121 moves in the axis direction of the pipe 101, so that helical threads are formed

Methodology Applied
Scientific EffectMechanical cutting: Abrasion

Data Source

PatentEP2090389B1Machining unit and machine tool
Publication Date: 2010.08.18 SANKYO SEISAKUSHO
  • EP2090389B1 patent drawingFigure 1A~1B
  • EP2090389B1 patent drawingFigure 2A~2B
  • EP2090389B1 patent drawingFigure 3

AI summary

A machining unit that is supported on a machine tool and machines a workpiece by a revolving tool with a main spindle section being driven and rotated includes an eccentric rotational section, a tool holder, a tool revolution-radius changing mechanism, and a cutting-edge-orientation correcting mechanism. The eccentric rotational section is disposed on the main spindle section, and is rotatable about an eccentric axis that is located eccentrically at any distance in a radial direction of the main spindle section from a rotation center of the main spindle section. The tool holder is disposed on the eccentric rotational section, and supports the tool. The tool revolution-radius changing mechanism moves the tool in the radial direction, and changes the radius of the revolution of the tool by rotating the eccentric rotational section about the eccentric axis. The cutting-edge-orientation correcting mechanism corrects the orientation of a cutting edge of the tool by making the tool holder spin about an axis of the tool holder, the axis being parallel to the rotation center of the main spindle section.