Tactile Probe Stylus Module Kinematic Stops
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Solution Overview
Problem
Tactile probing systems in coordinate-measuring machines face issues with excessive displacement, leading to deformation or breakage of movable bodies due to the lack of adequate constraint, especially when thin-walled portions exceed their elasticity limits, and existing solutions like stoppers and kinematic connections do not fully address bending, torsion, tension, and compression problems.
Innovation Solution
The design incorporates a tactile probing system with a stylus module that includes a movable portion sandwiched between fixed portions, utilizing kinematic joints and mechanical stops to absorb and manage excessive displacement, allowing the stylus to separate from the sensor when limits are exceeded, and featuring piezo resistive strain gauges connected in a Wheatstone bridge configuration for precise displacement measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If movable bodies are not constrained other than by thin-walled portions, then the structure remains simple and flexible, but the movable bodies suffer from deformation or breakage when subject to excessive displacement
Solution Approach 1:
The patent introduces stoppers that constrain the movable bodies at specific displacement limits, changing the physical state of the system from completely flexible to constrained at critical points. This prevents the thin-walled portions from exceeding their elasticity limits while maintaining structural simplicity.
Solution Approach 2:
The stoppers are positioned in advance to prevent excessive displacement before it can cause damage. By providing mechanical stops at predetermined locations, the system cushions against potential deformation or breakage of the movable bodies and thin-walled portions.
2Reliability
If stoppers are provided to constrain displacement of movable bodies, then the thin-walled portions do not exceed elasticity limit, but the device complexity increases and bending, torsion, tension, and compression problems persist
Solution Approach 1:
The patent applies constraints (stoppers) only at specific critical locations where excessive displacement would cause damage, rather than constraining the entire movable body structure. This localized approach protects the thin-walled portions while minimizing overall structural complexity.
3Reliability
If a kinematic connection is provided to allow stylus separation under excessive displacement, then the stylus is protected, but bending, torsion, tension, and compression problems still occur in the contact probe
Solution Approach 1:
The patent segments the contact probe into distinct functional components: the stylus, the movable bodies, the thin-walled portions, and the stoppers. This segmentation allows each component to be optimized independently - the stylus can separate under excessive displacement while the stoppers protect the thin-walled portions from bending, torsion, tension, and compression.
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 solution significantly increases the tolerance for excessive displacement, preventing breakage and maintaining measurement precision, allowing for millimeter-order overshoot and enabling precise 3D measurements with enhanced durability and sensitivity.
Implementation Method 1
Each having a piezo resistive strain gauge vapor-deposited thereon and connected in a Wheatstone bridge configuration
Implementation Method 2
The thin-walled portions of the sensor have elasticity limits and may not be able to receive the excessive displacement transmitted via the movable bodies
Data Source
Figure 1A
Figure 1B
Figure 1C
AI summary
A contact probe includes a stylus, a sensor, and two parallel substantially planar plates. The stylus has a contact. The sensor has a substantially planar shape and includes a fixed portion, at least three thin-walled portions each formed of a planar plate and having a strain sensor vapor-deposited thereon, and a movable portion to which the stylus is mounted and linked to the fixed portion via the thin-walled portions in at least three locations. The two parallel substantially planar plates are connected to the fixed portion on opposing sides and sandwich the movable portion so as to maintain a predetermined distance between the movable portion and the two parallel substantially planar plates and limit movement of the movable portion to a movable range. The sensor outputs a contact signal due to the strain sensors deforming in response to a measurement force from the stylus.