Power Tool Transmission With Dynamic Gear Shift and Offset Axes
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Solution Overview
Problem
Existing power tools with transmissions that require inactivity for gear adjustments are prone to jamming, and lubrication issues arise when used in vertical orientations, making them inconvenient and less effective in restricted spaces.
Innovation Solution
A power tool design featuring a transmission with offset rotation axes and a gear selection mechanism that allows for torque transmission through multiple gears without jamming, combined with compartmentalized grease chambers to maintain lubrication in various orientations, enabling efficient operation in tight spaces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a transmission with an internal draw key is used to select different gears, then gear selection is enabled, but the transmission must be inactive during adjustment which causes inconvenience and potential jamming
Solution Approach 1:
The gear selection mechanism is designed to operate dynamically during transmission function. The draw key can be actuated to engage or disengage gears while the transmission is running, eliminating the need to stop the tool for gear changes. This dynamic adjustment capability resolves the contradiction by allowing gear selection without requiring transmission inactivity.
2Reliability
If lubricant is provided to the transmission, then lubrication is improved, but the lubricant flows away when the power tool is used in vertical orientations
Solution Approach 1:
The transmission housing is divided into multiple separate grease chambers (first grease chamber, second grease chamber) that are isolated from each other. Each chamber contains lubricant for specific transmission components. This segmentation prevents lubricant from flowing between chambers and ensures each chamber maintains adequate lubrication regardless of the tool's orientation, resolving the contradiction between reliable lubrication and vertical orientation performance.
Solution Approach 2:
Different regions of the transmission are provided with localized lubrication through separate grease chambers. Each chamber is positioned and sized to provide adequate lubrication to its specific components in any orientation. This localized approach ensures that lubrication effectiveness is maintained locally in each chamber regardless of the overall tool orientation.
3Adaptability or versatility
If a shift lever mechanism is placed adjacent to the side of the drive gears, then gear selection is achieved, but the radial dimension increases making the power tool harder to use in restricted spaces
Solution Approach 1:
The gear selection mechanism utilizes axial movement of the draw key along the rotation axis of the output shaft rather than radial placement. This dimensional change allows the shift lever mechanism to be positioned within the existing radial envelope of the transmission, eliminating the need for increased radial dimension while maintaining full gear selection functionality.
Data Source
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AI summary
A power tool (100) comprises a motor (104) having a drive shaft. A transmission (200) has an intermediate shaft (216) with a first rotation axis (C) operatively coupled to an output shaft (202) with a second rotation axis (B) connected to a tool holder (204). The intermediate shaft (216) is operatively coupled to the motor drive shaft via an input shaft (218) having a third rotation axis (D). The output shaft (202) comprises at least a first gear (206) and a second gear (208). The intermediate shaft (216) comprises at least a first idling gear (220) and a second idling gear (222) configured to respectively engage the first gear (206) and the second gear (208) such that the transmission (200) is configured to transmit torque from the motor (104) to the tool holder (204) via a first gearing or a second gearing. A gear selection mechanism (234) is moveable within the output shaft (202) and configured to selectively engage the first gear (206) or the second gear (208). Each of the first rotation axis (C), the second rotation axis (B) and the third rotation axis (D) are offset from each other in a first direction (X) and a second direction (Y).