Tool Assembly Shank Tapering for Alignment and Torque Transfer

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Solution Overview

Problem

Existing clamping mechanisms for tool assemblies in metal working operations face challenges in maintaining alignment and torque transfer due to manufacturing tolerances and potential obstructions, requiring significant force and tight tolerances to achieve 'full coupling' between the shank and socket.

Innovation Solution

A tool assembly design featuring a shank that tapers axially with a frustoconical coupling member, a collet with bulge portions, and a tool holder with a cavity that includes a forward tapering and cylindrical portion, allowing for secure alignment and torque transfer without relying on elastic deformation or tight manufacturing tolerances.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If tight manufacturing tolerances are used for conical shank and socket geometries, then alignment between rotational axes is improved, but manufacturing complexity and cost increase

Engineering Contradiction:

Improvealignment between rotational axesVSAvoidmanufacturing complexity

Core Design Contradiction:

Manufacturing precisionVSEase of manufacture

Solution Approach 1:

The coupling interface is divided into two distinct geometric zones: a conical region for torque transfer and a cylindrical region for alignment. This segmentation allows each zone to perform its specific function with relaxed tolerance requirements, eliminating the need for tight tolerances across the entire interface.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different geometric properties are assigned to different regions of the coupling interface. The conical region provides friction-based torque transfer, while the cylindrical region provides alignment through geometric constraint. Each region is optimized for its specific function rather than requiring uniform high precision throughout.

Inventive Principle:

Principle #3Local quality

2Reliability

If significant drawing force is applied via collet onto coupling member, then full coupling contact is improved, but device complexity and force requirements increase

Engineering Contradiction:

Improvefull coupling contactVSAvoidclamping mechanism complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

A conical geometry is used instead of a cylindrical one, creating a wedge effect where radial clamping force from the collet is converted into axial drawing force on the coupling member. This geometric transformation achieves full coupling contact with reduced collet force requirements.

Inventive Principle:

Principle #14Spheroidality (Curvature)

Solution Approach 2:

The coupling mechanism transitions from a static friction-based interface to a dynamic wedge-based interface. The conical geometry allows the system to self-adjust and self-center during engagement, maintaining full coupling contact through geometric constraint rather than relying solely on high clamping forces.

Inventive Principle:

Principle #15Dynamics

3Reliability

If elastic deformation of socket periphery walls is used to enable full coupling, then coupling contact is improved, but manufacturing precision requirements increase

Engineering Contradiction:

Improvecoupling contactVSAvoidsocket geometry precision

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The conical geometry is designed to automatically generate the necessary drawing force during the engagement process itself. As the tool is inserted and the collet applies radial clamping force, the conical surfaces convert this into axial force that pulls the coupling member into full contact, eliminating the need for pre-applied significant drawing force.

Inventive Principle:

Principle #10Preliminary action

4Manufacturing precision

If tight tolerances are maintained during manufacturing of shank and socket, then alignment is improved, but resistance to obstructions such as dirt or metal chips deteriorates

Engineering Contradiction:

ImprovealignmentVSAvoidsensitivity to obstructions

Core Design Contradiction:

Manufacturing precisionVSObject-affected harmful factors

Solution Approach 1:

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The design accepts that some variation and potential obstructions may occur, but the redundant cylindrical alignment region provides a tolerance buffer that prevents these variations from affecting functional performance. The system is designed to be robust against rather than sensitive to such variations.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

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 design reduces the force required for 'full coupling' and maintains alignment between the tool and tool holder, enabling efficient torque transfer with reduced manufacturing tolerance requirements and improved resistance to obstructions.

Implementation Method 1

The coupling mechanism has the main objectives of transferring torque by, inter alia, frictional force from a spindle via the tool holder to the tool

Methodology Applied

Scientific EffectFriction: Friction

Implementation Method 2

a significant drawing force has to be applied via the collet onto the coupling member

Methodology Applied

Scientific EffectMechanical Force: Mechanical Force

Data Source

PatentUS7478983B2Tool assembly

Publication Date: 2009.01.20 ISCAR LTD

AI summary

A tool assembly in which a tool is releasably mounted on a tool holder. The tool is supported by the tool holder at two spaced apart regions which are formed independently therefore alignment between the axes of the tool and tool holder does not rely on tight manufacturing tolerances.