Length Reference Bar Thermal Expansion Compensation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing length reference bars for calibrating high-precision instruments like laser trackers and scanners are impractical for use outside their specified temperature range due to thermal expansion, leading to inaccuracies and complexities in design and calibration verification.
Innovation Solution
A length reference bar system with end caps that move oppositely to counteract thermal expansion, maintaining a constant distance between target positions, allowing for calibration verification using an inferometer alone and simplifying manufacturing and usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a length reference bar is designed for use within a specified temperature range, then measurement precision is maintained, but adaptability to different temperature conditions deteriorates
Solution Approach 1:
The patent applies thermal expansion principles by designing the end caps to expand thermally at a different rate than the bar portion. The end caps are made of a material with a higher coefficient of thermal expansion than the bar portion, causing them to expand more when temperature increases. This differential expansion compensates for the thermal expansion of the bar, maintaining constant target positioning accuracy across varying temperatures.
Solution Approach 2:
The patent changes the physical parameters of the end caps by selecting materials with specific thermal expansion coefficients and designing them with particular dimensions and attachment methods. The end caps are designed to be detachably attached to the bar portion, allowing their thermal expansion characteristics to be optimized independently. This parameter optimization enables the system to maintain measurement precision across a wider temperature range.
2Reliability
If probes are located axially with the length reference bar to compensate for thermal expansion, then thermal expansion compensation is achieved, but device complexity increases and alignment requirements worsen
Solution Approach 1:
The patent extracts the thermal compensation function from the probe alignment system and integrates it into the end cap design. Instead of requiring probes to be axially aligned with the bar for compensation, the end caps themselves provide the compensation through their differential thermal expansion. This separates the compensation function from the measurement function, reducing alignment complexity.
Solution Approach 2:
The end caps perform thermal compensation automatically through their material properties and geometric design, without requiring active control or complex alignment procedures. The differential expansion of the end caps self-corrects for thermal effects on the bar, providing passive compensation that simplifies the overall system operation.
3Ease of manufacture
If end caps are detachably attached to the bar portion, then ease of manufacture and assembly improves, but connection strength may deteriorate
Solution Approach 1:
The patent employs a dynamic attachment system where the end caps can be detachably connected to the bar portion. This allows the connection strength to be optimized for both secure attachment during use and easy removal for calibration or replacement. The detachable connection enables flexible assembly while maintaining sufficient strength through proper fastening mechanisms.
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 system effectively compensates for thermal expansion, ensuring accurate calibration and ease of use by maintaining a constant target distance, enabling precise verification of instrument functionality across varying temperatures without aligning the probe axially.
Implementation Method 1
This is due to the natural phenomenon of thermal expansion, which causes all materials to expand and contract when the materials are subjected to increases and decreases in temperature.
Data Source
AI summary
A length reference bar system and method that compensates for thermal expansion and allows for testing whether an instrument is working properly using only an inferometer. The system has a bar portion with end caps for target positions on either end of the bar portion that extend inward toward each other such that, if a length of the bar portion changes due to a temperature change, a length of the end caps also changes in an opposite direction to counteract the bar portion length change. Any target positions mounted on the end caps remain at a constant distance from each other regardless of the temperature thereby canceling out the effect of thermal expansion. The end caps also provide multiple target positioning capability so that any targets mounted thereon may be positioned in various configurations to provide a user with increased versatility for applications such as checking calibration.