Offset-Axis Power Tool Transmission for Seamless Gear Shifting
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Solution Overview
Problem
Existing power tools face issues such as transmission jamming during gear changes, inadequate lubrication due to orientation, and bulkiness that makes them difficult to use in restricted spaces.
Innovation Solution
A power tool transmission design with offset rotation axes and a gear selection mechanism that allows gear changes without interrupting operation, separate grease chambers for optimal lubrication, and a compact arrangement that reduces the tool's width.
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 gear changes causing operational interruption
Solution Approach 1:
A dogging member acts as an intermediary element between the draw key and the gear selection mechanism. This dogging member can be selectively engaged or disengaged from the draw key, allowing the gear selection mechanism to operate independently without requiring the transmission to be inactive. The dogging member mediates the connection between the selection mechanism and the transmission gears, enabling smooth gear changes during operation.
2Reliability
If lubricant is provided to the transmission, then lubrication is improved, but lubricant flows away when the power tool is used overhead or in vertical orientation
Solution Approach 1:
The lubricant storage and delivery system transitions from a gravity-dependent single-point lubrication approach to a multi-dimensional distribution system. Lubricant is stored in a reservoir and delivered through multiple lubrication points positioned at different locations within the transmission housing, ensuring adequate lubrication regardless of the tool's orientation in three-dimensional space.
3Ease of operation
If a shift lever mechanism is placed adjacent to the side of the drive gears, then gear selection is achieved, but the power tool's radial dimension increases making it harder to use in restricted spaces
Solution Approach 1:
The gear selection mechanism, including the draw key and dogging member, is nested within the existing transmission housing structure rather than being positioned externally adjacent to the drive gears. The selection mechanism utilizes the internal space of the transmission case, allowing gear selection functionality without increasing the external radial dimensions of the power tool.
Data Source
AI summary
A power tool includes a motor having a drive shaft. A transmission has an intermediate shaft with a first rotation axis operatively coupled to an output shaft with a second rotation axis connected to a tool holder. The intermediate shaft is operatively coupled to the motor drive shaft via an input shaft having a third rotation axis. The output shaft includes at least a first gear and a second gear. The intermediate shaft includes at least a first idling gear and a second idling gear configured to respectively engage the first gear and the second gear such that the transmission is configured to transmit torque from the motor to the tool holder via a first gearing or a second gearing. Each of the first rotation axis, the second rotation axis and the third rotation axis are offset from each other in a first direction and a second direction.