Compound Planetary Transmission for Wide Torque-Speed Power Tools
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Solution Overview
Problem
Existing power tools lack a transmission arrangement that can produce a wide range of output speeds and torques, limiting their versatility for tasks such as drilling large diameter holes, installing drywall screws, and high-speed drilling operations, often requiring separate tools for standard and heavy-duty applications due to energy consumption issues with early cordless rotary power tools.
Innovation Solution
A power tool with a multi-speed compound planetary transmission system that includes a planetary stage with an input sun gear, output planet carrier, and compound planet gears, allowing for selective operation in different gear reduction modes to achieve various speed and torque outputs, optimized for use with modern high-capacity batteries.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a single or dual speed transmission is used in power tools, then the tool can perform standard operations, but it lacks sufficient speed reducing capacity for low-speed, high torque operations
Solution Approach 1:
The transmission system is divided into multiple planetary gear stages, with each stage providing specific gear reduction ratios. The first planetary gear stage and second planetary gear stage are segmented to deliver different speed reduction levels, enabling the tool to achieve a wide range of output speeds and torques through modular gear arrangement
Solution Approach 2:
Compound planetary gear sets are nested within each other, where planet gears are arranged in multiple rows around the sun gear, with each row providing additional gear reduction. This nesting allows multiple gear reduction functions to be integrated in a compact configuration, expanding the speed range without proportionally increasing overall size
2Force
If configuration is optimized for high torque operations, then low-speed performance improves, but high speed performance is impaired
Solution Approach 1:
The transmission system provides dynamically selectable gear reduction ratios through the engagement of different planetary gear stages. Users can switch between first, second, and third gear reduction modes depending on whether high torque or high speed is needed, allowing the system to adapt its characteristics rather than being fixed in one optimization state
Solution Approach 2:
The system changes the gear reduction ratio parameter by engaging different planetary gear combinations. By varying the effective gear ratio between approximately 6:1 and 18:1, the transmission can deliver either high torque at low speeds or lower torque at higher speeds, effectively changing the operational parameters to match task requirements
3Use of energy by moving object
If early cordless rotary power tools with rechargeable batteries are used, then portability is achieved, but energy consumption is excessive for low-speed, high torque operations
Solution Approach 1:
The patent replaces early rechargeable battery systems with modern high-capacity battery technology that can sustain the energy demands of low-speed, high torque operations. This substitution enables cordless tools to deliver heavy-duty performance without being constrained by the energy limitations of earlier battery systems
Data Source
AI summary
A tool having a housing assembly, which defines a handle, a motor assembly, a trigger assembly, a spindle and a transmission assembly. The motor assembly is received in the housing assembly and has an output shaft. The trigger assembly is coupled to the housing assembly and is configured for use in actuating the motor assembly. The transmission assembly transmits rotary power between the output shaft of the motor assembly and the spindle. The transmission assembly includes a planetary stage with an input sun gear, an output planet carrier and a compound planet gear having a first planet gear and a second planet gear coupled together for common rotation on the output planet carrier. The planetary stage is selectively operable in a first gear reduction and a second, relatively lower gear reduction in which the compound planet gear cooperates to produce at least one intermediate gear reduction within the planetary stage.