Capacitive Safety System for Portable Power Tools
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Solution Overview
Problem
Existing safety systems for portable power tools are unreliable due to the risk of short-circuits and require significant modifications to existing tools, making them difficult to install and use.
Innovation Solution
A safety system that includes a pad made of electrically conductive material surrounding the tool, connected to a first and second transformer, allowing for galvanic isolation and capacitive coupling, which detects user contact to generate an alarm or modify the tool's speed without referencing the tool's potential, thus avoiding short-circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If existing safety systems use conductive pathways to detect contact between user and machining member, then contact detection capability is improved, but the risk of short circuits increases and reliability deteriorates
Solution Approach 1:
The patent introduces an intermediary capacitive coupling mechanism between the user and the machining member, replacing direct conductive pathways. The system detects contact through changes in capacitance rather than direct electrical conduction, thus avoiding short circuit risks while maintaining detection capability. The control unit measures capacitance variations to determine contact occurrence.
Solution Approach 2:
The patent replaces the traditional electrical conduction-based detection system with a capacitive sensing system. Instead of relying on electrical current flow through conductive materials, the system uses electrical field interactions and capacitance measurements to detect contact, fundamentally changing the detection mechanism to eliminate conductive pathway requirements.
2Reliability
If existing safety systems require significant modifications to power tools, then safety detection capability is improved, but device complexity and ease of manufacture worsen
Solution Approach 1:
The patent designs the safety system with universal applicability to existing power tools. The control unit and capacitive sensing mechanism can be integrated into various tool types without requiring fundamental redesigns. The system uses general-purpose components that can be adapted to different machining members and tool configurations, reducing overall device complexity.
Solution Approach 2:
The patent changes the detection parameter from electrical conductivity to capacitance. This parameter change allows the use of simpler, non-conductive materials for the machining member while maintaining detection functionality. The control unit is programmed to detect capacitance variations within specific ranges, enabling flexible integration across different tool types without complex hardware modifications.
3Measurement precision
If existing safety systems require additional user accessories or special clothing, then contact detection accuracy is improved, but ease of operation deteriorates
Solution Approach 1:
The patent enables the power tool itself to serve the safety detection function without requiring separate user accessories. The machining member's own capacitive properties are utilized for detection, and the control unit automatically monitors capacitance changes. This self-service approach eliminates the need for users to wear special conductive clothing or carry additional detection devices.
Solution Approach 2:
The patent uses the air gap and electrical field between the user's body and the machining member as an intermediary detection medium. This capacitive coupling occurs naturally when the user approaches or contacts the tool, requiring no additional accessories. The control unit detects this natural capacitive interaction to determine contact status.
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 system is more reliable, easier to install on existing tools, and does not require additional user accessories, providing enhanced safety without the risk of short-circuits.
Implementation Method 1
two transformers providing galvanic isolation
Implementation Method 2
based on impedance measurements
Data Source
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AI summary
Safety system (1000) for a power tool (10), comprising: - the power tool (10), comprising: - a machining element (4) and a support element (2), - a pad (12) of electrically conductive material, arranged to at least partially surround the body (9) of the tool (10) and to be grasped by a first limb of the user, - a first and a second transformer (T1, T2). An electrical circuit (1) comprising: - a secondary winding (L2) of the first transformer (T1), - a primary winding (L3) of the second transformer (T2), - a first terminal (D1; D2) connected to the pad (12), - a second terminal (D2; D1) connected to the machining element (4) and/or to the support element (2) is arranged to be closed when an impedance element connects the first terminal with the second, so that an induced current (Id) flows in the circuit.A control module is arranged to generate an alarm and/or to change the speed of an actuator, based on a measurement signal induced in the secondary winding (L4) of the second transformer (T2).