Multispeed Power Tool Selector for Low-Part-Count Gear 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 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 easy switching between gear ratios through a selector switch and biasing springs, which reduces the complexity and part count while enabling smooth gear ratio changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a traditional multispeed power tool design is used, then the tool can operate in different gear reduction ratios, but the part count is high and shifting between ratios is difficult
Solution Approach 1:
The patent combines multiple functions into the movable member, which simultaneously serves as a speed selector, a clutch element, and a gear ratio changer. By integrating these functions into a single component, the design reduces the part count while maintaining the ability to switch between different gear reduction ratios.
Solution Approach 2:
The movable member is designed to perform multiple functions: selecting speed, engaging/disengaging clutch elements, and changing gear ratios. This multi-functional design eliminates the need for separate components for each function, thereby reducing overall device complexity.
2Adaptability or versatility
If a traditional multispeed power tool design is used, then the tool can operate in different gear reduction ratios, but shifting between ratios is difficult
Solution Approach 1:
The biasing springs automatically engage and disengage the clutch elements as the movable member shifts positions, eliminating the need for manual clutch operation. The system self-regulates the engagement process through the mechanical action of the springs, making gear ratio changes simpler and more intuitive for the user.
Solution Approach 2:
The biasing springs are pre-positioned to automatically engage clutch elements before the movable member fully reaches its target position, and to begin disengagement in advance. This preliminary action ensures smooth transitions between gear ratios without requiring precise manual timing from the operator.
3Device complexity
If a simplified speed selector mechanism is used, then the part count is reduced, but reliable gear ratio switching may be compromised
Solution Approach 1:
The patent replaces complex multi-component mechanical shifting mechanisms with a simplified system using biasing springs and a single movable member. The spring-based engagement mechanism provides reliable clutch element activation through mechanical force, ensuring consistent and dependable gear ratio switching despite the reduced part count.
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.