Hand-Held Tool Grip Sensor for Defined Capacitive Activation
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Solution Overview
Problem
Existing hand-held machine tools with capacitive sensors cannot reliably ensure that a user is holding the tool with a firm grip, as undesired contact, such as with the back of a hand, can lead to detection, and there is no defined method for user-side detection.
Innovation Solution
A hand-held machine tool design featuring a capacitive sensor system with a first element connected to a control device and a second displaceable element, where user actuation of the second element changes the distance between the elements, allowing for force-dependent detection, ensuring only a defined grip activates the sensor, thus preventing undesired actuation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a capacitive sensor is used to detect user presence, then the machine tool can be activated when a hand is detected, but undesired contact such as with the back of a hand also leads to detection, making it impossible to ensure firm grip
Solution Approach 1:
The capacitive sensor is divided into two separate elements: a first element connected to the control device and a second element that is displaceable relative to the first element. This segmentation allows the system to detect not just presence but also the displacement caused by proper gripping, thereby distinguishing intentional activation from accidental contact.
Solution Approach 2:
The control device monitors the distance or displacement between the first and second sensor elements and uses this feedback to determine whether activation should occur. Only when the displacement exceeds a threshold (indicating proper grip) does the system enable activation, providing reliable feedback-based control.
2Device complexity
If a single line connects the sensor element to the control device, then the structure remains simple and inexpensive, but the sensor cannot detect force-dependent grip
Solution Approach 1:
The second sensor element is designed to be displaceable relative to the first element, creating a dynamic structure that responds to applied force. This dynamic element allows the simple single-line configuration to detect grip force through displacement, maintaining structural simplicity while achieving force-dependent detection precision.
Solution Approach 2:
The displaceable second element acts as an intermediary between the user's grip force and the capacitive sensing mechanism. It translates mechanical force into positional change relative to the first element, enabling the control device to detect grip strength through the single connection line.
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 solution ensures reliable detection of a user's hand in the intended grip region, preventing accidental activation and allowing the machine tool to be actuated only when held correctly, thereby implementing a 'dead man function' in a structurally simple and cost-effective manner.
Implementation Method 1
at least one capacitive sensor element operatively connected to the control device
Implementation Method 2
The first element and the second element are interconnected via a spring device
Data Source
AI summary
A hand-held machine tool including a drive device by which a tool that can be brought into operative connection with the machine tool can be actuated, with a control device for actuating the drive device and at least one capacitive sensor element (40) operatively connected to the control device being provided. The at least one sensor element (40) has a first element (42) connected to the control device via a line (44) and a second element (43) which is arranged at a distance from and so as to be displaceable relative to the first element (42) and can be actuated by a user.