Power Tool Pivot Member Reversing Restriction Mechanism
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Solution Overview
Problem
Existing power tools with gear mechanisms face issues where the pivot plate is not reliably stopped at a target position due to retroaction after the drive unit stops, leading to unexpected gear ratio switching, especially when there is no brake circuit, resulting in early wear of components and increased tool size.
Innovation Solution
Incorporating a reversing restriction portion in the pivot member, which includes inclined holding holes and surfaces to restrict pivoting in the reverse direction, ensuring the movable member is stopped at a given position even after the drive unit stops, without the need for a brake circuit, by applying sliding resistance and locking mechanisms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a brake circuit is used to stop the gearshift actuator at the target position, then the positioning accuracy is improved, but the device complexity increases
Solution Approach 1:
The invention extracts the braking function from a separate brake circuit and integrates it into the cam hole structure itself. The inclined holding hole portion acts as an inherent braking mechanism that converts kinetic energy into frictional heat, eliminating the need for external braking components and circuits.
Solution Approach 2:
The cam hole structure serves itself by incorporating the holding hole that automatically provides braking action during the pivoting motion. The friction between the support and the inclined holding hole portion self-regulates the pivoting speed and stops the motion at the target position without requiring external control systems.
2Ease of operation
If the pivot plate is allowed to pivot by inertia after the gearshift actuator stops, then the ease of operation is improved, but the reliability deteriorates due to unexpected gear ratio switching
Solution Approach 1:
The inclined holding hole portion is designed to counteract the inertial pivoting motion before it can cause harmful effects. As the pivot plate approaches the target position, the support enters the inclined holding hole portion which creates increasing frictional resistance, thereby suppressing further inertial pivoting and preventing the pivot plate from reaching positions that would cause unexpected gear ratio switching.
3Duration of action of moving object
If the motor is enlarged to prevent early wear of the gearshift actuator components, then the duration of action is improved, but the weight of the power tool increases
Solution Approach 1:
The inclined holding hole portion acts as a cushioning mechanism that absorbs and dissipates the kinetic energy of the pivoting motion through friction. This beforehand cushioning reduces the impact forces and wear on the gearshift actuator components, thereby extending their service life without requiring a larger motor.
4Manufacturing precision
If a brake circuit is used to stop the gearshift actuator, then the positioning accuracy is improved, but the volume of the power tool increases
Solution Approach 1:
The invention merges the braking function with the existing cam hole structure by incorporating the inclined holding hole portion. This integration combines multiple functions (guiding the support, providing braking action, and maintaining positioning) into a single structural element, thereby achieving accurate positioning without increasing the overall volume of the power tool.
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 unexpected gear ratio switching and reduces component wear, allowing for precise control and maintaining tool size without the need for additional braking systems, enhancing the reliability and efficiency of power tools.
Implementation Method 1
The holding hole is inclined with respect to the circumferential direction of the pivot member... applies sliding resistance that restricts pivoting of the pivot member in the reverse direction
Data Source
Figure 1
Figure 2~3
Figure 4A~4C
AI summary
A power tool includes a reversing restriction portion (46b (46c)) arranged in a pivot member (42). When a drive unit (33) pivots the pivot member (42) to switch the gear ratio of a gear mechanism (41), the reversing restriction portion (46b (46c)) engages with a support (47) to restrict pivoting of the pivot member (42) in a reverse direction that is caused by a reaction force which acts on the pivot member (42) at a limit position from where further pivoting of the pivot member (42) is prohibited.