Multispeed Power Tool Gear Selector With Simplified 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 transmission assembly with a reduction gearset and a speed selector mechanism, featuring a movable member, actuator, and shifter assembly, which allows for easy switching between gear ratios through a selector switch and biasing springs, reducing the overall part count and simplifying the gear shifting process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a traditional multispeed power tool design is used, then gear ratio changes can be achieved, but the part count becomes high and shifting becomes difficult
Solution Approach 1:
The patent combines the speed selector mechanism components (movable member, actuator, shifter assembly) into an integrated unit that operates within the transmission assembly. The selector switch, switch fork, and biasing springs work together as a unified mechanism to control the movable member's position, reducing the overall part count while maintaining multispeed functionality.
Solution Approach 2:
The movable member serves multiple functions: it acts as a selector for different gear ratios, a actuator for the planetary stages, and a structural component of the transmission assembly. The single movable member controls engagement of different planetary stage combinations to achieve multiple speed ratios, eliminating the need for separate mechanisms for each function.
2Adaptability or versatility
If a traditional multispeed power tool design is used, then gear ratio changes can be achieved, but the shifting operation becomes difficult
Solution Approach 1:
The biasing springs automatically return the movable member to its neutral position after actuation, and the detent features automatically engage to lock the movable member in selected positions. This self-servicing mechanism eliminates the need for complex control systems or manual resetting, making the shifting operation simple and intuitive.
Solution Approach 2:
The switch fork acts as an intermediary between the selector switch and the movable member, translating the user's selection input into precise positioning of the movable member. This intermediary mechanism ensures accurate and smooth shifting operations by mediating the control signal transmission.
3Device complexity
If a simplified speed selector mechanism is used, then part count is reduced, but gear ratio shifting capability must be maintained
Solution Approach 1:
The movable member is designed to be selectively movable between fixed positions, transitioning from a static component to a dynamic selector. This dynamic capability allows the same component to achieve multiple gear ratios by changing its position, maintaining versatility while using fewer parts.
Solution Approach 2:
The transmission assembly is segmented into distinct functional zones: the reduction gearset with planetary stages, the speed selector mechanism with movable member, and the housing assembly. This segmentation allows each component to be optimized for its specific function while working together as an integrated system, reducing overall complexity.
Data Source
AI summary
A tool with a transmission 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 shift fork is slidably coupled to the selector switch and receives the yoke. The springs cooperate to bias the shift fork relative to the selector switch into a neutral position.