Multi-Fiber Conductive Coupling for Stable Blade Contact Detection
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Solution Overview
Problem
Existing conductive couplings for power tools with active injury mitigation technology face challenges in maintaining a reliable, direct physical contact with spinning blades or arbors, leading to potential delays in detecting human contact due to microscopic bouncing, which can result in interruptions in the electrical signal and increased risk of injury.
Innovation Solution
The use of multi-fiber or multi-filament brushes that make direct contact with the spinning blade or arbor, ensuring continuous electrical connection through multiple points of contact, and positioning these brushes within a conductive material or chamber to minimize wear and maintain reliable signal transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single-point conductive coupling is used to contact the spinning blade or arbor, then the device structure is simple, but the electrical contact reliability deteriorates due to microscopic bouncing
Solution Approach 1:
The conductive coupling is segmented into multiple independent contact points (multiple fibers or filaments) instead of a single contact point. This segmentation ensures that if one contact point loses contact due to bouncing, other contact points maintain the electrical connection, thereby resolving the contradiction between structural simplicity and contact reliability.
Solution Approach 2:
Different parts of the conductive coupling (individual fibers or filaments) have the same basic function but operate independently. The local quality of each fiber is optimized for reliable contact, and the collective behavior of multiple fibers provides redundant contact paths, resolving the reliability issue while maintaining overall structural simplicity.
2Reliability
If multiple conductive elements are used to maintain continuous contact, then the electrical signal reliability improves, but the device complexity increases
Solution Approach 1:
Multiple conductive fibers or filaments are merged into a single integrated conductive coupling assembly. This merging allows the system to achieve reliable signal transmission through multiple parallel contact paths while presenting a unified, manageable structure that does not excessively increase device complexity.
Solution Approach 2:
The multi-fiber conductive coupling serves multiple functions simultaneously: it provides redundant electrical contact paths, accommodates the spinning motion of the blade or arbor, and maintains continuous electrical connection. This multi-functionality resolves the contradiction by achieving reliability enhancement without proportionally increasing complexity.
3Speed
If direct physical contact is maintained with the spinning blade, then the detection speed improves, but the contact stability deteriorates due to bouncing
Solution Approach 1:
The conductive fibers or filaments are pre-positioned to contact the spinning blade or arbor before any bouncing occurs. The multiple contact points are established in advance, creating redundant pathways that ensure continuous electrical connection even when bouncing disrupts individual contact points, thus maintaining both detection speed and contact stability.
Solution Approach 2:
The multi-fiber structure provides beforehand cushioning against contact instability. By having multiple fibers ready to make contact, the system cushions against the destabilizing effect of bouncing, ensuring that detection speed is not compromised while contact stability is maintained through redundant contact paths.
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 provides a reliable and durable conductive coupling that maintains continuous electrical contact with the blade or arbor, reducing the likelihood of signal interruptions and enabling swift detection of human contact, thereby enhancing the safety and effectiveness of active injury mitigation systems in power tools.
Implementation Method 1
The conductive brush makes direct physical contact with the spinning blade or arbor... minimizing the radius at which the brush contacts the arbor or blade to reduce wear
Implementation Method 2
positioning these brushes within a conductive material or chamber to minimize wear and maintain reliable signal transmission
Data Source
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AI summary
Power tools with conductive couplings used with active injury mitigation technology are disclosed. Conductive couplings are particularly relevant to table saws, hand-held circular saws, track saws, miter saws, and band saws with active injury mitigation technology. Conductive couplings provide a mechanism through which an electrical signal can be coupled or imparted to a blade, and then monitored for changes indicative of human contact with the blade. An exemplary conductive coupling includes a brush that establishes an electrical connection with a moving part of a power tool, and the brush maintains contact with the moving part of the power tool during at least 40 hours of cumulati ve time when the motor is spinning the arbor and blade without an interruption in the electrical connection sufficient to trigger the reaction system. A conductive coupling may be two-sided compliant. A conductive coupling may connect to a motor shaft to minimize electrical noise.