Planetary Speed Selector for Multispeed Power Tool Gear Shifting
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Solution Overview
Problem
Existing multispeed power tools face difficulties in shifting between different overall gear reduction ratios and have a high part count, which complicates their operation and design.
Innovation Solution
The design incorporates a housing assembly with a transmission assembly that includes a reduction gearset and a speed selector mechanism, featuring a movable member, actuator, and shifter assembly, allowing for seamless switching between first and second overall gear ratios through a combination of planetary stages and axial movement, with biasing springs to maintain a neutral position.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a traditional multispeed power tool design is used, then gear ratio switching capability is achieved, but the part count increases and operational complexity increases
Solution Approach 1:
The patent combines multiple functions into integrated components. The speed selector mechanism integrates the movable member, actuator, and shifter assembly into a unified structure that selectively couples planet carriers to the housing, enabling gear ratio changes without requiring separate mechanisms for each function. This merging reduces the overall part count while maintaining multispeed capability.
Solution Approach 2:
The movable member serves multiple functions: it acts as a coupling element between the planet carrier and housing, functions as a selector for different gear ratios, and provides a mounting structure for the actuator. This multi-functionality reduces the need for additional specialized components, thereby reducing part count while achieving gear ratio switching.
2Adaptability or versatility
If a traditional multispeed power tool design is used, then gear ratio switching capability is achieved, but operational complexity increases
Solution Approach 1:
The patent employs a dynamic speed selector mechanism where the movable member can be selectively positioned to couple different planet carriers to the housing. This dynamic coupling/decoupling approach allows smooth transitions between gear ratios during operation, reducing operational complexity compared to fixed or rigid switching mechanisms.
Solution Approach 2:
The actuator serves as an intermediary element that mediates between the user's selection input and the mechanical coupling of planet carriers. By introducing this intermediate component, the system simplifies the user interaction required for gear ratio switching, making operation easier while maintaining the ability to switch between multiple ratios.
3Volume of moving object
If a compact transmission assembly is used, then tool size is reduced, but gear ratio switching difficulty increases
Solution Approach 1:
The patent implements a nested arrangement where the speed selector mechanism is integrated within the compact transmission assembly. The movable member, actuator, and shifter components are positioned within the existing transmission housing space, allowing gear ratio switching functionality to be added without significantly increasing the overall transmission assembly volume.
Solution Approach 2:
The patent utilizes axial movement of the movable member along the longitudinal axis of the transmission assembly to achieve gear ratio switching. This axial dimension provides the necessary movement space for coupling/decoupling planet carriers without requiring increased radial or lateral dimensions, thereby maintaining a compact transmission assembly while enabling gear ratio changes.
Data Source
AI summary
A tool with a transmission assembly having a reduction gearset and a speed selector. The speed selector has a member, an actuator and a shifter assembly. The member is movable between a first position, in which the member is non-rotatable, and a second position in which the member is coupled to a planet carrier of the reduction gearset for common rotation. The actuator includes a pivoting yoke and a follower that is coupled to the yoke. The follower engages the member so as to be axially movable with the follower. The shifter assembly has a selector switch, a switch fork, and a pair of springs. The selector switch is slidable between a first switch position and a second switch position. The switch fork is slidably coupled to the selector switch and receives the yoke. The springs cooperate to bias the switch fork relative to the selector switch into a neutral position.