Hand-Guided Power Tool Braking Device State Control
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Solution Overview
Problem
Hand-guided power tools, such as motor chain saws and trimmers, face damage due to improper utilization of braking devices, leading to potential overload, wear, and high temperatures, particularly with band brakes and centrifugal clutches.
Innovation Solution
Incorporating a sensor to detect the state of the braking device, which sends a state signal to a control unit to control the power tool's devices, preventing impermissible operating states by limiting engine speed and preventing the drive motor from starting when the braking device is applied, and ensuring the braking device is released before operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the braking device is applied to stop the working tool, then the working tool is stopped and operator safety is improved, but the drive motor may be overloaded or the braking device may suffer damage
Solution Approach 1:
The control unit is programmed to check the braking device state before allowing the drive motor to start. If the braking device is applied, the motor startup is prevented in advance, avoiding overload conditions before they can occur.
Solution Approach 2:
A sensor detects the state of the braking device and sends a state signal to the control unit, which then adjusts the drive motor operation accordingly. This feedback loop ensures the motor does not start when the brake is applied, preventing overload.
2Reliability
If the braking device is applied to stop the working tool, then the working tool is stopped, but significant wear on the clutch pads results and high temperatures occur on the centrifugal clutch
Solution Approach 1:
The control system checks the braking device state before enabling the drive motor. By preventing motor startup when the brake is applied, the system avoids the harmful combination of brake engagement and clutch operation that causes wear and overheating.
Solution Approach 2:
The sensor continuously monitors the braking device state and provides feedback to the control unit, which adjusts the drive motor operation to prevent harmful operating conditions during brake application.
3Reliability
If a sensor and control unit are added to detect braking device state and control the drive motor, then damage prevention is improved, but the device complexity increases
Solution Approach 1:
The control unit serves multiple functions: it monitors the braking device state via the sensor, controls the drive motor startup based on brake state, and prevents harmful operating conditions. This multi-functionality reduces the need for separate dedicated components for each function.
Data Source
AI summary
A hand-guided power tool has a drive motor and a drive element connected to and driven by the drive motor. A working tool is connected to the drive element and driven by the drive element. A braking device is correlated with the drive element, wherein the braking device in a first state, in which the braking device is applied, blocks the drive element and in a second state, in which the braking device is released, releases the drive element so that the drive elements can rotate freely. The braking device has a brake lever and a sensor that detects the first and second states of the braking device. A control unit is provided, wherein an output signal of the sensor as a state signal of the first state or the second state is supplied to the control unit. The control unit, based on the state signal, controls devices of the power tool.