Active Pen Tip Pressure Sensor Using Non-Linear Leaf Spring
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Solution Overview
Problem
Existing active pens with pressure sensors face challenges in accurately detecting a wide range of forces due to the complexity, size, and robustness issues associated with traditional spiral springs and elastic elements, which result in high assembly time and detection errors.
Innovation Solution
The use of a non-linear leaf spring as an elastic element that is both conductive and integrated with the position signal circuit, allowing it to act as both a contact mechanism and a force detection mechanism, reducing complexity and increasing accuracy by varying stiffness based on tip displacement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If traditional spiral springs or elastic elements with constant stiffness are used, then a wide force detection range is achieved, but the manufacturing precision and detection accuracy for small forces deteriorate
Solution Approach 1:
The patent applies parameter changes by using a non-linear elastic element whose stiffness varies with displacement rather than remaining constant. This allows the system to achieve both wide force detection range and high precision for small forces, as the stiffness automatically adapts to the applied force magnitude.
Solution Approach 2:
The patent implements local quality by creating different stiffness characteristics at different displacement ranges. The non-linear elastic element provides higher stiffness for large forces and lower stiffness for small forces, optimizing detection accuracy across the entire force range rather than using a uniform stiffness property.
2Measurement precision
If multiple springs with different stiffness are used to extend force detection range, then the force detection accuracy is improved, but the device complexity increases
Solution Approach 1:
The patent merges the functions of multiple springs with different stiffness into a single non-linear elastic element. This integration maintains the ability to detect a wide range of forces with high accuracy while eliminating the complexity of assembling and coordinating multiple separate spring components.
Solution Approach 2:
The non-linear elastic element serves multiple functions simultaneously: it acts as both the elastic restoring element and the force detection mechanism. This multi-functionality eliminates the need for separate components and simplifies the overall device structure while maintaining detection accuracy across the full force range.
3Quantity of substance
If spiral springs are used for force detection, then the force detection range is extended, but the ease of manufacture and assembly deteriorate
Solution Approach 1:
The patent extracts the complex spiral spring mechanism and replaces it with a simpler non-linear elastic element that can be directly integrated into the pen structure. This extraction eliminates the need for complex assembly procedures while maintaining the force detection range.
4Difficulty of detecting and measuring
If movable parts and springs are used in pressure sensors, then the force detection capability is improved, but the reliability and robustness deteriorate
Solution Approach 1:
The patent combines the elastic element and the force detection mechanism into a single integrated non-linear elastic element. This merging eliminates movable parts and potential failure points associated with separate components, thereby improving reliability and robustness while maintaining force detection capability.
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 enables high accuracy in detecting small forces while maintaining a wide force detection range, reducing assembly time and complexity, and avoiding the limitations of traditional elastic elements.
Implementation Method 1
an elastic element (9, 15) is integrated into the force detection mechanism (9) and is configured to store energy and/or act against the force applied on the tip (3)
Data Source
Figure 1~2
Figure 3~6
Figure 7~10
AI summary
Active position indicator comprising a movable tip element (10) configured to be displaced from an initial position in a displacement direction by a tip displacement depending on the force acting on a tip (3) arranged on a distal end of the tip element (10); a force sensor for detecting a force acting on the tip (3) comprising an elastic element acting on the tip element (10) against the tip displacement; wherein the elastic element is a leaf spring (15).