Electric Power Tool Speed Limiting for Steel Plate Drilling
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Solution Overview
Problem
Electric power tools with drilling functions often cause excessive wear of bits due to high rotation speeds when used with steel plates, leading to reduced 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 speed when the trigger is fully pulled, using a three-stage planetary gear mechanism and an upper limit rotation speed selector to maintain a controlled speed, thereby reducing wear on bits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the trigger is pulled to increase rotation speed for drilling operations, then drilling efficiency is improved, but bit wear increases excessively
Solution Approach 1:
The patent implements dynamic rotation speed control by switching between multiple rotation speed modes (first, second, and third modes with progressively lower speeds) based on operational requirements. The rotation speed changing circuitry dynamically adjusts the motor rotation speed to match the specific drilling task, preventing excessive speed that would cause bit wear while maintaining high speed when productivity is needed.
Solution Approach 2:
The patent changes the rotation speed parameter of the motor through the rotation speed changing circuitry, which selectively connects different rotation speed modes. By modifying this key operational parameter, the system optimizes the balance between drilling efficiency and bit service life, resolving the contradiction between high productivity and reduced material loss.
2Speed
If high rotation speed is used for drilling steel plates, then drilling speed is improved, but bit service life is reduced
Solution Approach 1:
The system provides dynamic adjustment of rotation speed through multiple selectable modes. The rotation speed changing circuitry enables the motor to operate at different speeds (first mode for high speed drilling, second and third modes for lower speed applications), allowing users to select appropriate speeds for different materials and tasks, thereby extending bit service life while maintaining drilling speed when needed.
Solution Approach 2:
The patent makes the electric power tool universal by incorporating multiple rotation speed modes that can handle various drilling applications. The rotation speed changing circuitry provides multi-functionality, enabling the same tool to drill steel plates at high speed when necessary while also performing lower-speed drilling for applications requiring extended bit life, thus resolving the contradiction between drilling speed and service life.
3Productivity
If maximum rotation speed is maintained for all operations, then productivity is improved, but bit wear increases and service life decreases
Solution Approach 1:
The patent implements dynamic rotation speed management with multiple operational modes. The rotation speed changing circuitry allows the system to switch between first mode (maximum speed for high productivity tasks) and second/third modes (reduced speeds for tasks requiring bit reliability). This dynamic adjustment maintains high productivity when needed while preserving bit reliability through appropriate speed selection.
Solution Approach 2:
The system changes the rotation speed parameter based on operational requirements. By modifying this parameter through the rotation speed changing circuitry, the system optimizes both productivity and bit reliability, preventing the excessive wear that would result from continuous maximum speed operation while maintaining high productivity when the application demands it.
Data Source
AI summary
An electric power tool includes a motor, an output shaft, a drive force transmission configured to reduce drive speed of the motor and transmit drive force of the motor to the output shaft; a trigger that can be pulled by a user; a rotation speed changing circuitry 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; and a rotation speed control circuitry 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.