Capacitive Grip Sensing for Accidental Switch Lockout in Personal Care Tools
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Solution Overview
Problem
Handheld personal care devices, such as electric razors, often experience unintended operation when carried in a bag due to accidental activation of the operation switch, and existing solutions like lock mechanisms or time-dependent mode shifting can be complex or prone to unintentional unlocking.
Innovation Solution
A handheld personal care device equipped with a sensor electrode embedded in the grip unit that detects changes in capacitance when grasped, coupled with a control device to lock or unlock the operation switch based on grasp information, preventing erroneous operations without requiring manual locking or unlocking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a lock mechanism is equipped on the operation switch to prevent unintended operation, then reliability is improved, but device complexity increases and ease of operation deteriorates due to required lock/unlock operations
Solution Approach 1:
The device automatically detects when it is being held by a user through the sensor electrode and autonomously controls the lock state of the operation switch. When the sensor detects the user's hand, the switch is automatically unlocked; when not detected, it is automatically locked. This eliminates the need for manual lock/unlock operations while preventing unintended operation.
Solution Approach 2:
The patent replaces the mechanical lock mechanism with an electronic control system using a sensor electrode and control unit. Instead of mechanical springs and latches, the system uses electrical signals to detect hand presence and control the switch state, simplifying the overall mechanism while maintaining reliability.
2Reliability
If a lock mechanism is equipped on the operation switch, then reliability is improved, but ease of operation worsens because users may forget to perform lock operations
Solution Approach 1:
The device performs the locking function automatically based on sensor detection. The control unit continuously monitors the sensor electrode and autonomously adjusts the operation switch state without requiring user intervention, eliminating forgetfulness issues while maintaining security.
Solution Approach 2:
The sensor electrode provides continuous feedback about whether the device is being held. The control unit uses this feedback to automatically adjust the lock state, creating a closed-loop system that responds to user presence and ensures the switch is locked when not in use.
3Reliability
If modes are shifted depending on continuous pressing time to lock the operation switch, then reliability is improved, but ease of operation worsens due to risk of unintentional long pressing
Solution Approach 1:
The patent replaces the time-dependent pressing mechanism with a sensor-based detection system. Instead of requiring the user to press for a specific duration to lock, the sensor electrode detects hand presence and automatically controls locking, eliminating the risk of unintentional long pressing while achieving the same reliability goal.
Solution Approach 2:
The sensor electrode acts as an intermediary between the user and the operation switch. Rather than directly pressing the switch to lock it, the user's hand presence is detected by the sensor, which then triggers the automatic locking through the control unit, adding a safety layer that prevents accidental activation.
4Reliability
If the operation switch is locked automatically, then reliability is improved, but ease of operation worsens because the switch cannot be operated during grasping
Solution Approach 1:
The lock state of the operation switch is dynamically adjusted based on real-time sensor detection. The control unit continuously monitors the sensor electrode and changes the switch state from locked to unlocked when hand presence is detected, and from unlocked to locked when not detected, making the system adaptive to current usage conditions.
Solution Approach 2:
The device prepares the operation switch in advance by locking it before the user needs to operate it. When the sensor detects that the device is being held, the switch is automatically unlocked in advance, ensuring it is ready for immediate use without requiring additional user actions.
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 effectively prevents unintended operation of the device when carried in a bag, simplifies the operation by eliminating the need for manual locking, and ensures the switch remains locked even in wet conditions or during temporary non-use, enhancing user convenience and safety.
Implementation Method 1
a sensor electrode that is embedded in the grip unit, and causes a change in capacitance depending on whether or not the grip unit is grasped
Data Source
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AI summary
A handheld personal care device according to the present disclosure includes: an operation switch configured to change a treatment operation of an operation unit; a sensor electrode configured to cause a change in capacitance depending on whether or not the grip unit is grasped; and a control device electrically connected to the operation switch and the sensor electrode and configured to control the treatment operation of the operation unit. The control device includes: a grasp detector configured to detect that the grip unit is grasped based on a change in capacitance of the sensor electrode; and a change permission part configured to permit the operation switch to change the treatment operation of the operation unit when the change permission part receives, from the grasp detector, grasp information indicating that the grip unit is grasped.