Power Tool Transmission With Separated Gear Key Positions
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Solution Overview
Problem
Heavy-duty power tools with multiple gearings face issues such as transmission jamming when adjusting gears during operation and inadequate lubrication due to lubricant flow when used in vertical orientations, making them inconvenient to use, especially in restricted spaces.
Innovation Solution
A power tool transmission system with a gear selection key that moves between distinct positions, allowing torque to be transmitted through different gears without jamming, and a compartmentalized lubrication system with separate grease chambers to maintain lubrication in various orientations, enhancing usability and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the transmission is designed with multiple gearings for different workpiece requirements, then the adaptability of the power tool is improved, but the device complexity increases
Solution Approach 1:
The transmission system is segmented into multiple independent gearings (first gearing, second gearing, third gearing) that can be selectively engaged. Each gearing operates independently with its own gear selection key position, allowing the system to provide multiple functions while maintaining a relatively simple overall structure. The gear selection key moves between distinct positions to engage different gearings without requiring complex shifting mechanisms.
2Reliability
If the gear selection key moves between distinct positions separated by distance greater than key width, then the reliability of gear engagement is improved, but the ease of operation deteriorates
Solution Approach 1:
The gear selection key engagement is achieved by moving the key between distinct positions along the rotation axis direction rather than requiring lateral movement. This dimensional approach allows the key to engage different gearings (first, second, third gearings) by simply moving forward or backward along the axis, ensuring reliable engagement while maintaining ease of operation. The distance between positions is greater than the key width to prevent simultaneous engagement of multiple gears.
3Device complexity
If the lubricant is provided in a single chamber, then the device complexity is reduced, but the reliability of lubrication in vertical orientations deteriorates
Solution Approach 1:
The lubrication system is segmented into separate grease chambers (first grease chamber, second grease chamber) that are spatially distributed within the transmission housing. Each grease chamber is positioned to ensure adequate lubrication of specific transmission components regardless of the power tool's orientation. This segmentation ensures that lubricant remains in contact with gear surfaces even when the tool is used in vertical or overhead positions, maintaining reliable lubrication without requiring a complex active lubrication system.
4Volume of moving object
If the gear selection key width is reduced to allow compact design, then the volume of the power tool is reduced, but the reliability of gear engagement deteriorates
Solution Approach 1:
Instead of increasing the gear selection key width in the radial direction (which would increase tool volume), the design utilizes the axial dimension along the rotation axis. The gear selection key moves between distinct positions separated by a distance greater than the key width, ensuring reliable engagement. This approach maintains a compact radial profile while achieving reliable gear selection through axial movement, effectively resolving the contradiction between compact size and engagement reliability.
Data Source
AI summary
A power tool includes a motor having a drive shaft and a transmission having an input shaft operatively coupled to the drive shaft of the motor and an output shaft operatively coupled to a tool holder. The transmission includes at least a first gear and a second gear. A gear selection key is moveable between a first position and a second position and configured to engage the first gear to the output shaft in the first position such that the torque is transmitted from the motor to the tool holder via the first gear and configured to engage the second gear to the output shaft in the second position such that the torque is transmitted from the motor to the tool holder via the second gear. The first position and the second position are separated by a distance greater than a width of the gear selection key.