Encoder Scale Mounting Between Guide Rail and Surface
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Solution Overview
Problem
Existing coordinate positioning apparatuses face challenges in accurately measuring displacement between moving parts due to inaccuracies in mounting and alignment of encoder scales, particularly on guide rails, leading to variations in scale distance and measurement errors.
Innovation Solution
An encoder scale member is designed to be retained between a mounting surface and a motion guide, with scale markings accessible to a sensor, featuring mounting features for secure attachment, allowing for precise positioning and reduced deformation, enabling accurate measurement of relative displacement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the encoder scale is mounted on the lateral surface of the guide rail, then the scale can be positioned close to the sensor, but the scale distance varies due to mounting inaccuracies leading to measurement errors
Solution Approach 1:
The patent introduces a dedicated scale mounting structure that acts as an intermediary between the guide rail and the encoder scale. This structure includes a mounting block with a mounting surface that contacts the guide rail and a scale mounting surface that holds the encoder scale, ensuring precise and consistent positioning without direct mounting of the scale to the guide rail surface
Solution Approach 2:
The mounting system is divided into separate functional components: the guide rail, the mounting block (which provides positioning features), and the encoder scale. This segmentation allows each component to be optimized independently for its specific function while maintaining precise relative positioning through dedicated interface features
2Ease of operation
If the encoder scale is mounted on the guide rail, then the scale can be positioned for sensing, but mounting inaccuracies cause variations in scale distance leading to measurement errors
Solution Approach 1:
The mounting block is pre-configured with precise positioning features (mounting surface and scale mounting surface) that establish the correct geometry before the encoder scale is installed. This preliminary preparation ensures that when the scale is mounted, it is automatically positioned at the correct distance and orientation, eliminating the need for complex alignment operations
Solution Approach 2:
The mounting structure incorporates self-aligning features where the mounting block's geometry automatically ensures proper scale positioning. The scale mounting surface is designed to work with the scale's mounting features to automatically establish the correct position, reducing the need for operator skill and external alignment tools
3Measurement precision
If the encoder scale member is retained between the mounting surface and motion guide, then consistent scale distance is achieved, but the structure becomes more complex
Solution Approach 1:
The mounting block combines multiple functions into a single component: it provides structural support, establishes positioning through its mounting surface contact with the guide rail, and holds the encoder scale through its scale mounting surface. This merging of functions into one integrated part reduces the number of separate components needed while maintaining precision
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 accurate and reliable measurement of displacement with increased precision and robustness, even in hostile environments, by ensuring consistent scale distance and alignment, thus enhancing the accuracy of position determination in coordinate positioning systems.
Implementation Method 1
a first member comprising a sensor for sensing scale markings
Implementation Method 2
as disclosed in EP1752851 it is known to mount an active magnetic scale on a lateral surface of a guide rail
Data Source
AI summary
A coordinate positioning apparatus is described. The coordinate positioning apparatus comprises a mounting surface, a motion guide mountable on the mounting surface, a first member comprising a sensor for sensing scale markings, the first member being mountable on the motion guide, and an encoder scale member comprising a first set of scale markings which are, in use, sensable by the sensor. At least part of the encoder scale member is retained between the mounting surface and the motion guide such that the encoder scale member is supported by the mounting surface at least in the vicinity of the first set of scale markings. The motion guide may be a guide rail or a bearing, for example. En encoder scale member for use with such a coordinate positioning apparatus is also described.