Length-Measuring Device Dual-Spring Scanning Carriage
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Solution Overview
Problem
Existing length-measuring devices face challenges in achieving precise and vibration-resistant position measurement, particularly in machine tools and semiconductor industries, due to flexural stiffness limitations and assembly tolerances, which affect measurement accuracy and require heavier, less weight-saving designs.
Innovation Solution
A length-measuring device with a carrier and scanning carriage coupled to a drive dog via a connecting element that is rotatably mounted at pivot joints, using a combination of springs to press the scanning carriage against guide surfaces, minimizing bending stresses and allowing for a more rigid and weight-saving design, while compensating for assembly tolerances and alignment deviations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a flexurally stiff connecting element is used to couple the scanning carriage to the drive dog, then the connection strength is improved, but the device weight increases and the design becomes less weight-saving
Solution Approach 1:
The connecting element is divided into two segments that are rotatably mounted to the scanning carriage at a first pivot joint and to the drive dog at a second pivot joint. This segmentation allows the connecting element to be more fragile and weight-efficient while still providing sufficient connection strength through the rotational joints, resolving the contradiction between strength and weight.
Solution Approach 2:
The connecting element changes its structural parameters by being rotatably mounted rather than rigidly fixed. This allows the element to adapt to assembly tolerances and alignment deviations while reducing its weight, achieving both connection strength and weight reduction.
2Device complexity
If the scanning carriage is pressed against the guide surface at a single position, then the balancing is simplified, but the measurement precision deteriorates due to vibration resistance issues
Solution Approach 1:
The pressure force application is segmented into two separate positions: a first position where the first spring presses the scanning carriage against the guide surface, and a second position where the second spring presses the scanning carriage against the guide surface. This segmentation improves vibration resistance and measurement precision while maintaining manageable balancing complexity.
3Ease of manufacture
If a rigid connecting element is used, then the assembly tolerance compensation is reduced, but the manufacturing precision requirements increase
Solution Approach 1:
The connecting element is designed with rotational degrees of freedom at the pivot joints, making it dynamic rather than rigid. This allows the connecting element to adapt to assembly tolerances and alignment deviations, improving ease of assembly while reducing the stringency of manufacturing precision requirements.
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 enables precise and vibration-resistant position measurement with a compact, space-saving design, reducing measurement errors and increasing resistance to vibration, allowing for a more fragile and weight-efficient connecting element that effectively compensates for assembly tolerances and alignment changes.
Implementation Method 1
A first spring is disposed between the connecting element and the drive dog and exerts a pressure force on the scanning carriage at a first position so as to press the scanning carriage against the at least one guide surface
Implementation Method 2
A second spring is disposed between the connecting element and the scanning carriage. The second spring is spaced apart from the first spring in the measurement direction and exerts a pressure force on the scanning carriage at a second position spaced apart from the first position in the measurement direction so as to press the scanning carriage against the at least one guide surface
Implementation Method 3
A connecting element which extends in the measurement direction and is rotatably mounted to the scanning carriage at a first pivot joint and to the drive dog at a second pivot joint spaced apart from the first pivot joint in the measurement direction
Data Source
AI summary
A length-measuring device includes a scanning carriage for scanning a measuring graduation that is to be guided longitudinally in the measurement direction on a guide surface. A coupling couples the scanning carriage to a drive dog rigidly in the measurement direction and resiliently transversely to the measurement direction. A first spring is disposed between a connecting element of the coupling and the drive dog and exerts a pressure force on the scanning carriage at a first position so as to press the scanning carriage against the guide surface. A second spring is disposed between the connecting element and the scanning carriage. The second spring is spaced apart from the first spring in the measurement direction and exerts a pressure force on the scanning carriage at a second position spaced apart from the first position in the measurement direction so as to press the scanning carriage against the guide surface.