Low-Mass Coupling Element for Precision Length Measurement
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Solution Overview
Problem
Existing length measuring devices face challenges in achieving a simple, compact structure while maintaining precise position measurement, often compromised by the need for complex couplings that affect measurement accuracy due to mass-spring systems.
Innovation Solution
A length measuring device with a coupling element made of low-density, high-modulus materials like ceramic or carbon fiber reinforced plastic (CFRP), using a solid-state joint and peg-shaped elements for flexible coupling, eliminating the need for stop pins and allowing for improved frequency behavior and reduced mass.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a traditional coupling with mass-spring system is used, then the coupling provides flexibility, but the natural frequencies cause deterioration of measurement accuracy
Solution Approach 1:
The patent changes the material parameters of the coupling element by using ceramic or CFRP materials with lower density and higher modulus of elasticity compared to traditional steel. This parameter change shifts the natural frequency band towards higher frequencies, eliminating interference with measurement accuracy while maintaining structural simplicity.
Solution Approach 2:
The patent employs composite materials, specifically carbon fiber reinforced plastic (CFRP) or ceramic, for the coupling element. These materials provide a favorable combination of low density and high modulus of elasticity, achieving both flexibility and high natural frequency without requiring complex mass-spring systems.
2Measurement precision
If high-density materials like steel are used for the coupling element, then the coupling provides sufficient mass for stability, but the mass leads to lower natural frequency and reduced measurement precision
Solution Approach 1:
The patent fundamentally changes the density parameter of the coupling element by selecting ceramic or CFRP materials with 10-80% of steel's density. This parameter change reduces the coupling element's mass, shifting the natural frequency higher and eliminating measurement precision deterioration while maintaining adequate stability.
3Ease of operation
If a complex coupling structure with stop pins and ball supports is used, then the coupling provides robust mechanical connection, but the complexity increases device size and reduces compactness
Solution Approach 1:
The patent extracts and eliminates unnecessary components from the traditional coupling structure, specifically removing stop pins and ball support mechanisms. The simplified coupling element with through-openings provides adequate mechanical connection without the bulk and complexity of traditional designs, achieving compactness while maintaining operational reliability.
4Stability of the object's composition
If low-modulus materials are used for the coupling element, then the coupling provides flexibility, but the flexibility reduces inherent stiffness and lowers natural frequency
Solution Approach 1:
The patent optimizes the modulus of elasticity parameter by selecting materials with 100-500 GPa, significantly higher than traditional flexible materials. This parameter change provides sufficient inherent stiffness to maintain high natural frequency while retaining adequate flexibility for the coupling function, resolving the contradiction between flexibility and stiffness.
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 design achieves high rigidity with low mass, shifting the natural frequency band towards higher frequencies, enhancing measurement accuracy and eliminating the need for additional mass-spring systems, resulting in a simple, compact, and precise position measurement system.
Implementation Method 1
The solid-state joint is a leaf spring. The solid-state joint is designed to support the coupling element so as to be freely rotatable about a first axis of rotation that is perpendicular to a plane of the measuring division relative to the driver.
Implementation Method 2
The coupling element has a lower density and/or a higher modulus of elasticity compared to steel. This allows the frequency band of the system's natural frequency to be shifted significantly towards higher frequencies.
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
A length measuring device comprises a scale (12), a scanning carriage (16) for scanning a measuring division (14) of the scale (12), and a coupling (20) comprising a coupling element (22). The coupling element (22) is attached to a driver (26) via a solid joint (30). The solid joint (30) is designed to support the coupling element (22) so that it can rotate freely about a first axis of rotation (R1) perpendicular to a plane (S) of the measuring division (14) relative to the driver (26). The coupling element (22) has a lower density and/or a higher modulus of elasticity compared to steel.