Handheld Micrometer Epicyclic Gear Drive

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Solution Overview

Problem

Handheld micrometers lack the desirable features of traditional fine-pitch thread-driven micrometers, such as engagement stiffness and resistance, which are essential for precise measurement and user feedback, especially when dealing with workpieces of varying cross-sections.

Innovation Solution

A handheld micrometer drive configuration utilizing an epicyclic gear drive system that includes a spindle drive gear, planetary drive gear, and ring gear, allowing for rapid spindle movement with limited user motion, and incorporating a self-locking spindle drive thread configuration to provide the necessary engagement stiffness and resistance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Speed

If a coarse pitch thread is used to directly drive the micrometer, then rapid spindle movement is achieved, but engagement stiffness and resistance are lost

Engineering Contradiction:

Improvespindle movement speedVSAvoidengagement stiffness

Core Design Contradiction:

SpeedVSStrength

Solution Approach 1:

The patent introduces an epicyclic gear drive system as an intermediary mechanism between the thimble and the spindle drive thread. This gear system includes a spindle drive gear, planetary drive gear, and ring gear that work together to transmit and amplify the rotational motion while maintaining the fine pitch thread configuration, thereby achieving both rapid movement and engagement stiffness

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent changes the mechanical parameters by implementing a gear ratio system where the spindle drive gear has fewer teeth than the ring gear. This parameter change allows the spindle to rotate multiple times for each thimble rotation, achieving rapid movement while the fine pitch thread maintains engagement stiffness through the mechanical advantage of the gear system

Inventive Principle:

Principle #35Parameter changes

2Strength

If a fine pitch thread is used to drive the micrometer, then engagement stiffness is maintained, but rapid spindle movement is not achieved

Engineering Contradiction:

Improveengagement stiffnessVSAvoidspindle movement speed

Core Design Contradiction:

StrengthVSSpeed

Solution Approach 1:

The patent adds a rotational dimension through the epicyclic gear system. Instead of relying solely on the linear thread pitch for speed, the system introduces angular multiplication where the planetary drive gear rotates around the sun gear, creating multiple rotational cycles that amplify the spindle movement speed while the fine pitch thread maintains stiffness

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

3Stability of the object's composition

If electronic sample and hold circuits are used for reading stability, then reading stability is achieved, but device complexity increases

Engineering Contradiction:

Improvereading stabilityVSAvoidelectronic circuit complexity

Core Design Contradiction:

Stability of the object's compositionVSDevice complexity

Solution Approach 1:

The patent implements a self-service mechanical stabilization system where the self-locking feature of the fine pitch thread, combined with the friction characteristics of the epicyclic gear drive, naturally maintains the spindle position and reading stability without requiring external electronic intervention. The mechanical system serves itself to maintain stability through its inherent physical properties

Inventive Principle:

Principle #25Self-service

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 epicyclic gear drive system enables precise and ergonomic operation by rotating the spindle at a higher rate than the thimble, allowing for finer spindle drive thread pitches while maintaining rapid spindle advance, thus providing improved engagement stiffness and user feedback without the need for electronic stabilization.

Implementation Method 1

Methodology Applied

Scientific EffectEpicyclic gearing: Epicyclic Gearing

Implementation Method 2

incorporating a self-locking spindle drive thread configuration to provide the necessary engagement stiffness and resistance

Methodology Applied

Scientific EffectFriction: Friction

Implementation Method 3

The spindle drive gear, the planetary drive gear, and the ring gear may be referred to as an epicyclic gear drive, or an epicyclic drive, for short

Methodology Applied

Scientific EffectMechanical advantage: Mechanical Advantage

Data Source

PatentUS8997369B2Fast rotary drive for a handheld micrometer

Publication Date: 2015.04.07 MITUTOYO CORP

AI summary

A micrometer drive configuration for a handheld micrometer comprises: a frame; a spindle; a linear displacement sensor that senses a displacement of the spindle; a threaded spindle drive having a relatively coarse thread pitch, wherein the threaded spindle drive is attached to a spindle drive gear; a planetary drive gear that mates to the spindle drive gear; a ring gear surrounding and mating to the planetary drive gear; and a thimble generally surrounding the spindle drive gear, the planetary drive gear, and the ring gear. The thimble is coupled to drive the spindle drive gear through the planetary drive gear, and the planetary drive gear is sized and mounted such that the spindle drive gear turns faster than the thimble.