Nested Gear Transmission for Power Tool Speed Shifting
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Solution Overview
Problem
Existing power tools, such as multi-speed hammer drills, face challenges in optimizing internal component configuration to allow for robust shifting and operation due to limited space within the housing, which affects the efficient switching between different speed and torque settings.
Innovation Solution
A transmission system with a speed shift assembly that includes a guide member and a user-engageable member, allowing the second output gear to nest into the first output gear, enabling selective coupling for different speed settings, and a biasing member to facilitate engagement with the output member, optimizing gear alignment and shifting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple output gears are arranged in a conventional configuration, then speed and torque optimization is achieved, but axial space requirements increase
Solution Approach 1:
The second output gear is configured to nest within the first output gear when not in use. The second gear includes an annular body that can be positioned inside the first gear's annular depression, allowing compact storage of multiple gears in limited axial space while maintaining the ability to provide different speed and torque ratios when engaged
2Adaptability or versatility
If a speed shift assembly is added to enable gear switching, then operational versatility is improved, but device complexity increases
Solution Approach 1:
A guide member acts as an intermediary component to control the shifting between different output gears. The guide member includes a guide surface that directs the movement of the second gear during shifting operations, and a guide slot that receives and guides the actuator pin, simplifying the overall shifting mechanism while enabling reliable gear transitions
Solution Approach 2:
The biasing member automatically urges the second output gear away from the first output gear to maintain proper spacing and alignment during operation. This self-actuating feature ensures correct gear positioning without requiring additional actuation mechanisms, reducing overall system complexity while maintaining reliable operation
3Force
If the second output gear is made larger to provide higher torque, then torque output is improved, but space within the housing is reduced
Solution Approach 1:
The second output gear with larger dimensions for higher torque capability is designed to nest within the first output gear when not engaged. The annular body of the second gear fits within the annular depression of the first gear, allowing the larger torque-providing gear to occupy minimal axial space during storage while maintaining its full torque capability when activated
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration allows for efficient shifting between speed positions, reducing axial space requirements and enhancing operational efficiency by ensuring proper gear alignment and engagement, thereby optimizing the power tool's performance across different drilling modes.
Implementation Method 1
a biasing member disposed between the first and second output gears. The biasing member is configured to urge the first output gear away from the second output gear while complementary teeth on the first output gear and the output member align during engagement
Data Source
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AI summary
A power drill (10) comprises a housing (12) having a motor (50) that includes an output member (52). A rotary output spindle (70,70') can be journaled in the housing. A transmission (72) is disposed in the housing and includes a first output gear (76) and a second output gear (78). The transmission can selectively couple the output member (52) to the output spindle through one of the first output gear (76) or the second output gear (78) for rotating the output spindle at one of a first speed or a second speed, respectively. A speed shift assembly (120) includes a guide plate and a user engageable member (34). The guide plate can selectively influence movement of the first and second output gears. The user engageable member can be movable between a first speed position and a second speed position. Movement between the first and second positions can cause the second output gear to at least partially nest into the first output gear.