Length Measuring Device Thermal Decoupling
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Solution Overview
Problem
Existing length measuring devices face inaccuracies due to tension and temperature-related shifts caused by differential linear expansions between the carrier and scale, leading to measurement inaccuracies, especially in machine tools and semiconductor industries.
Innovation Solution
A length measuring device with a scale attached to a carrier using a fastening system that minimizes frictional forces during temperature changes, featuring a viscous intermediate layer for adhesion and a flexible fastening mechanism that decouples the scale from the carrier, allowing for thermal expansion without constraining forces, and a holder for forming a thermal zero point that bypasses the carrier, ensuring precise and stable measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the scale is rigidly connected to the carrier at a fixed point by means of a form fit, then the scale is stabilized and easier to handle, but tension and temperature changes can lead to shifts in the fixed point, resulting in measurement inaccuracies
Solution Approach 1:
A holder is introduced as an intermediary component that connects the scale to the body to be measured at the fixed point, bypassing the carrier. This mediator allows the scale to be thermally decoupled from the carrier at the fixed point, preventing transmission of thermal expansion forces while maintaining mechanical support and positioning.
Solution Approach 2:
The connection system is segmented into two independent paths: (1) the holder provides a stationary connection from the scale to the body at the fixed point, and (2) the carrier provides support and stabilization elsewhere along the scale. This segmentation allows different parts to fulfill different functions without interfering with each other's thermal behavior.
2Ease of manufacture
If the carrier is made of a material with different linear expansion coefficient than the scale, then the carrier can be made of less expensive material, but differential thermal expansion causes friction and constraining forces that affect measurement accuracy
Solution Approach 1:
The holder acts as a mediator that interrupts the direct thermal interaction between the carrier and scale at the fixed point. This allows the carrier to be made of cost-effective materials with different thermal expansion coefficients while preventing these differences from generating constraining forces on the scale.
Solution Approach 2:
The thermal expansion interaction is extracted from the carrier-scale connection at the fixed point by routing the connection through the holder instead. This removes the source of thermal stress while preserving the functional relationship between carrier and scale in other regions.
3Stability of the object's composition
If the scale is guided in a longitudinally movable manner on a profile part, then thermal expansion is accommodated, but the device complexity increases
Solution Approach 1:
The holder serves as a simple intermediary component that provides a stationary connection path bypassing the carrier, avoiding the need for complex movable guidance mechanisms while still accommodating thermal expansion differences between the carrier and scale.
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 solution provides a high-precision, temperature-stable position measurement by stabilizing the scale with a carrier made of less expensive material, adapted to the thermal expansion coefficient of the body being measured, resulting in improved handling and measurement accuracy while avoiding measurement inaccuracies.
Implementation Method 1
The fastening means, which mounts the scale on the carrier so that it can be displaced in the measurement direction, is an intermediate layer which adhesively holds the scale on the carrier
Implementation Method 2
This intermediate layer is designed, for example, as a liquid film over which the scale is drawn against a surface of the carrier by means of capillary action
Implementation Method 3
when the temperature changes, the carrier can expand in length relative to the scale in the measuring direction with as little friction as possible
Data Source
Figure 1
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Figure 4
AI summary
The length measuring device comprises a component (1) that includes a support (12) and a scale (11) attached to it with low friction. The support (12) can be fixed in place on a body (13) to be measured for position measurement. Furthermore, a bracket (3) is provided with which the scale (11) can be attached to the body (13) to a fixed point (P), bypassing the support (12).