Multispeed Power Tool Gear Selector With Neutral-Biased Shifting
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Solution Overview
Problem
Existing multispeed power tools face difficulties in shifting between different overall gear reduction ratios and often have a high part count, which complicates their design and functionality.
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, an actuator, and a shifter assembly with biasing springs, allowing for seamless switching between first and second overall gear ratios through a novel engagement mechanism.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a conventional multispeed power tool design is used, then gear ratio switching capability is provided, but the part count becomes high and shifting difficulties arise
Solution Approach 1:
The patent combines multiple functions into the movable member, which simultaneously serves as a speed selector, a gear shifter, and a locking mechanism. By integrating these functions into a single component rather than using separate parts for each function, the design reduces the overall part count while maintaining the capability to switch between different gear ratios.
Solution Approach 2:
The movable member is designed as a multi-functional component that can perform multiple operations: selecting speed, engaging different gear ratios, and providing locking engagement with the ring gear. This universal component approach eliminates the need for multiple specialized parts, directly addressing the high part count issue in conventional designs.
2Adaptability or versatility
If a conventional multispeed power tool design is used, then gear ratio switching capability is provided, but shifting difficulties occur
Solution Approach 1:
The follower acts as an intermediary component that translates the rotational movement of the movable member into axial movement. This mechanical intermediary ensures smooth and reliable engagement between different gear ratios by mediating the motion transfer, thereby eliminating shifting difficulties present in conventional direct-engagement designs.
Solution Approach 2:
The patent replaces complex multi-component mechanical shifting mechanisms with a simplified system based on magnetic coupling and direct mechanical engagement. The movable member magnetically couples to the planet carrier for common rotation, and locking teeth provide direct engagement with the ring gear, eliminating the need for complex intermediate shifting mechanisms and improving ease of operation.
3Device complexity
If a simplified gear mechanism is used, then part count is reduced, but gear ratio switching reliability may be compromised
Solution Approach 1:
The design incorporates dynamic engagement mechanisms where the movable member can rotate with the planet carrier during operation and then lock into fixed positions for gear ratio changes. The locking teeth engage with the ring gear teeth to provide secure mechanical locking, ensuring reliable gear ratio switching while maintaining a simplified part structure.
Solution Approach 2:
The patent uses magnetic coupling between the movable member and planet carrier to replace complex mechanical connection mechanisms. This magnetic field-based coupling provides reliable force transmission while maintaining simplicity, and the direct tooth-to-tooth engagement of locking teeth with the ring gear ensures reliable gear ratio switching without requiring multiple intermediate components.
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.