Trigger-Controlled Power Tool Speed Limits for Bit Wear Reduction
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Solution Overview
Problem
Existing electric power tools cause excessive wear on bits due to high rotation speeds when drilling through materials like steel, leading to reduced bit service life.
Innovation Solution
An electric power tool with a motor, output shaft, drive force transmission, trigger, rotation speed changing circuitry, and rotation speed control circuitry that limits the rotation speed of the output shaft to a lower maximum speed when the trigger is fully pulled, using a three-stage planetary gear mechanism and an upper limit rotation speed selector to manage speed reduction and control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the rotation speed of the motor is increased to improve drilling productivity, then the drilling speed increases, but the wear of the bit increases excessively
Solution Approach 1:
The patent applies dynamics by making the rotation speed adjustable and adaptable to different operating conditions. The control unit dynamically adjusts the motor rotation speed based on the selected bit type and material being drilled, allowing the system to optimize between speed and bit wear in real-time. This resolves the contradiction by enabling high speeds when appropriate while limiting speeds to protect bits when necessary.
Solution Approach 2:
The patent changes the rotation speed parameter based on the operating conditions. By detecting the bit type and material being drilled, the system adjusts the rotation speed parameter to appropriate levels - higher speeds for materials that tolerate them, lower speeds for materials that cause excessive bit wear. This parameter adaptation resolves the contradiction between productivity and bit service life.
2Reliability
If the rotation speed is limited to prolong bit service life, then bit wear is reduced, but the drilling productivity decreases
Solution Approach 1:
The system dynamically adjusts rotation speed limits based on the detected operating conditions rather than applying a fixed limit. When drilling materials that benefit from lower speeds, the system automatically reduces the speed limit to protect the bit. When drilling materials that can tolerate higher speeds, the system increases the limit to maintain productivity. This dynamic adaptation resolves the contradiction.
Solution Approach 2:
The control unit changes the rotation speed parameter based on bit type and material detection. By adjusting this parameter according to specific operating conditions, the system achieves lower speeds when needed for bit protection while maintaining higher speeds when productivity is the priority, thus resolving the contradiction between bit service life and drilling speed.
3Adaptability or versatility
If multiple rotation speed modes are provided to adapt to different materials, then the adaptability increases, but the device complexity increases
Solution Approach 1:
The system performs self-service by automatically detecting the bit type and material being drilled, then autonomously selecting the appropriate rotation speed mode without requiring manual intervention from the user. This automation provides multiple adaptability modes while keeping the user interface simple, resolving the contradiction between adaptability and complexity.
Solution Approach 2:
The system uses feedback from bit type detection and material identification to automatically adjust rotation speed settings. The control unit receives information about the operating conditions and responds by selecting the appropriate speed mode, creating a closed-loop system that achieves high adaptability through automated feedback mechanisms rather than complex manual controls.
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 effectively prolongs the service life of bits by reducing wear through controlled rotation speeds, allowing the tool to operate at low-speed, high-torque or high-speed, low-torque modes, and enabling users to select upper limit rotation speeds to prevent excessive wear.
Implementation Method 1
a three-stage planetary gear mechanism may be used as the drive force transmission
Data Source
Figure 1
Figure 2~3
Figure 4~6
AI summary
An electric power tool (10) includes a motor (21), an output shaft (38), a drive force transmission (23) configured to reduce drive speed of the motor and transmit drive force of the motor to the output shaft; a trigger (40) that can be pulled by a user; a rotation speed changing circuitry (50) configured to change a rotation speed of the output shaft that corresponds to a maximum pulled amount of the trigger to a limited rotation speed that is lower than a maximum rotation speed of the output shaft in a non-limited rotation speed mode (L1, L2); and a rotation speed control circuitry (50) configured to control a rotation speed of the motor in correspondence with a pulled amount of the trigger to obtain the rotation speed of the output shaft that is changed by the rotation speed changing circuitry.