Angle Scale Centering via Dual Scanning Head Feedback

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Solution Overview

Problem

Existing methods for assembling bodies with angle scales in angle measuring systems are inefficient and costly, often failing to accurately center the scales due to eccentricities caused by mounting deviations, which affects the accuracy of rotational movement measurements in machine tools.

Innovation Solution

A method involving two scanning heads positioned to scan the angle scale, with their signal outputs connected to an electronic counting device, allowing for detection of position signals and calculation of a difference to adjust the body's position and reduce eccentricity, enabling precise centering without the need for additional centering tools.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If traditional mounting methods are used to attach the angle scale body to the machine part, then the assembly process is simple, but mounting deviations cause excessive eccentricity that degrades measurement accuracy

Engineering Contradiction:
Improvecentering precision of angle scaleVSAvoidassembly process complexity
Core Design Contradiction:
Manufacturing precisionVSDevice complexity

Solution Approach 1:

The patent implements feedback by using two scanning heads to detect position signals from the angle scale and feeding this information back to a counting device. The counting device calculates the difference between signals from both scanning heads, providing real-time feedback on eccentricity magnitude. This feedback loop enables iterative adjustment of the angle scale position until eccentricity is minimized, achieving high centering precision through measurement-guided adjustment rather than relying solely on initial mounting accuracy.

Inventive Principle:
Principle #23Feedback

Solution Approach 2:

The patent replaces complex mechanical centering tools and procedures with an electronic measurement and calculation system. Instead of using mechanical dial gauges or complex alignment fixtures, the invention uses scanning heads to optically detect the angle scale position and electronically computes the eccentricity through signal differencing. This substitution of mechanical centering methods with electronic detection and calculation simplifies the physical assembly process while improving centering precision.

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

2Manufacturing precision

If dial gauges or complex centering tools are used to center the angle scale, then centering precision can be improved, but the cost and complexity of equipment increase

Engineering Contradiction:
Improvecentering precision of angle scaleVSAvoidassembly cost and equipment requirements
Core Design Contradiction:
Manufacturing precisionVSEase of manufacture

Solution Approach 1:

The patent implements self-service by making the angle scale itself the reference geometry for centering. The angle scale's graduated markings serve dual purposes: as the measurement scale for angle detection and as the reference feature for determining eccentricity. The scanning heads read the scale's own markings to generate position signals, and the system uses these signals to calculate and eliminate eccentricity. This eliminates the need for separate, expensive centering reference circles or precision stop edges, as the angle scale performs the centering function for itself.

Inventive Principle:
Principle #25Self-service

Solution Approach 2:

The patent applies multi-functionality by designing the angle scale to serve multiple functions simultaneously: it acts as the measurement scale for angle detection, as the reference geometry for centering, and as the source of position signals for eccentricity calculation. The same graduated markings that provide angular measurement also enable the determination of scale position and eccentricity. This multi-functional design eliminates the need for separate centering tools and reference features, reducing equipment requirements and assembly cost.

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

3Measurement precision

If high-resolution angle scales with small graduation periods are used, then measurement accuracy is improved, but the requirement for precise centering becomes more stringent and difficult to achieve

Engineering Contradiction:
Improveangle measurement accuracyVSAvoidcentering precision requirement
Core Design Contradiction:
Measurement precisionVSManufacturing precision

Solution Approach 1:

The patent uses feedback to iteratively reduce eccentricity to levels appropriate for high-resolution measurement. The counting device continuously monitors the difference between scanning head signals and provides feedback on the magnitude of eccentricity. Based on this feedback, the angle scale position can be adjusted in iterative steps until the eccentricity is reduced to a level that does not compromise the high measurement accuracy provided by the fine graduation period. This feedback-driven approach makes achieving the required centering precision manageable even for high-resolution systems.

Inventive Principle:
Principle #23Feedback

Solution Approach 2:

The patent replaces mechanical centering methods with electronic detection and calculation to achieve the precise centering required for high-resolution angle scales. The scanning heads optically detect the fine graduation markings without mechanical contact, and the electronic counting device calculates eccentricity with high precision through signal processing. This electronic approach achieves the sub-millimeter centering precision required for small graduation periods (less than 50 μm, particularly less than 25 μm or 10 μm) without the limitations of mechanical alignment tools.

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

Data Source

PatentEP2056072B1Method for mounting a body with angle scaling and device therefor
Publication Date: 2014.12.17 DR JOHANNES HEIDENHAIN GMBH
  • EP2056072B1 patent drawingFigure 1~2
  • EP2056072B1 patent drawingFigure 3
  • EP2056072B1 patent drawing

AI summary

The method involves detecting position signals (S1, S2) of scanning heads (2.1, 2.2) by an electronic counter (4). Count values are determined by the counter based on the position signals. Difference between the count values is determined. The difference or a variable e.g. angle error, based on the difference is outputted. A body is displaced with respect to a machine part i.e. shaft (3), such that the difference or the variable based on the difference is changed and eccentricity of angle scaling is reduced. An independent claim is also included for a device for mounting a body of an angle measuring system in a machine part.