Electric Cutting Tool Impedance Stop for Blade Contact Detection
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Solution Overview
Problem
Existing safety devices for electric cutting tools, such as pruning shears and chainsaws, face issues with discomfort from conductive clothing, risk of severed connections, and unreliable detection due to varying impedance values, especially when the operator's skin condition or environmental factors affect conductivity.
Innovation Solution
The safety cutting tool employs a system with electrically conductive cutting elements, insulated handle and trigger controls, and a dual manual contact electrode system to measure impedance, using a comparator to trigger an emergency stop when a predetermined threshold is crossed, ensuring reliable detection of contact with the cutting element without conductive clothing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conductive clothing (gloves, shoes) is used to detect contact with cutting element, then contact detection capability is improved, but operator comfort deteriorates and risk of connection failure increases
Solution Approach 1:
The operator's body serves as the conductive element itself, eliminating the need for external conductive clothing. The body's natural conductivity is utilized to complete the measurement circuit when contact with the cutting element occurs, making the system self-sufficient and comfortable for the operator.
Solution Approach 2:
The conductive clothing accessory is extracted and removed from the system. Instead of requiring external conductive elements, the invention directly uses the operator's body as the conductive path, simplifying the system and eliminating discomfort associated with specialized clothing.
2Reliability
If impedance measurement is used to detect contact, then contact detection is achieved, but measurement precision deteriorates due to varying skin conditions
Solution Approach 1:
The tool housing serves as an intermediary conductive element that provides a stable reference point for impedance measurement. By measuring impedance between the cutting element and the housing (which the operator touches), the system obtains a more consistent measurement than direct body impedance alone.
Solution Approach 2:
The measurement approach changes from measuring raw body impedance to measuring impedance through a controlled circuit that includes the tool housing as a reference. This parameter transformation stabilizes the measurement against variations in skin conditions.
3Reliability
If conductive clothing is required for safety, then injury prevention capability is improved, but ease of operation deteriorates due to forgotten or improper wearing
Solution Approach 1:
The operator's body naturally serves as the conductive element, eliminating the need to remember to wear or properly don conductive clothing. The safety function is automatically available whenever the operator touches the tool housing, making safety as easy as using the tool itself.
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 comfortable safety mechanism that effectively prevents injuries by accurately detecting contact with the cutting element, reducing the risk of severe cuts and eliminating the need for conductive clothing, thus enhancing operator safety.
Implementation Method 1
a measuring device of an impedance characteristic of a first electric circuit and an impedance characteristic of a second electric circuit
Implementation Method 2
a comparator of an impedance characteristic of the first electric circuit and a threshold value, which is dependent on the impedance characteristic of the second electric circuit
Data Source
AI summary
A safety cutting tool includes an electrically conductive cutting member, an electric motor for actuating the cutting member, a gripping handle electrically insulated from the cutting tool, a cutting trigger control that can be actuated by the hand of the user gripping the gripping handle, the cutting trigger control being electrically insulated from the cutting tool, an emergency stop device sensitive to a user coming into contact with the cutting member. The emergency stop device is controlled by a comparator comparing an impedance of a first electric circuit comprising the cutting tool and a second electric circuit used as a reference, the first and second circuits having manual contact electrodes provided on at least one of the gripping handle of the tool and the cutting trigger control. A method for controlling such a tool is also disclosed. The tool and method are is-applicable to electric secateurs and shears.