Compound Planetary Gear Stage for Multi-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 multi-speed compound planetary transmission system with a gearset portion that includes an input sun gear, compound planet gears, and ring gears, allowing for selective operation in different gear reduction modes to provide a wide range of 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-speed or dual-speed transmission is used in power tools, then the device complexity is reduced and manufacturing is easier, but the adaptability and versatility are limited, requiring multiple tools for different applications
Solution Approach 1:
The transmission system is divided into multiple independent planetary gear stages, each capable of providing different gear reduction ratios. The first planetary gear stage and second planetary gear stage can operate independently or in combination, allowing the system to achieve multiple speed and torque outputs from a single transmission unit, thereby eliminating the need for multiple separate tools.
Solution Approach 2:
The transmission assembly is designed to perform multiple functions within a single device by incorporating compound planetary gear mechanisms that can deliver both high-speed low-torque and low-speed high-torque operations. This multi-functional capability allows one tool to replace what previously required multiple specialized tools for different applications.
2Force
If a low-speed, high torque transmission is configured for heavy-duty operations, then the torque output is improved, but the high-speed performance deteriorates
Solution Approach 1:
The transmission system dynamically switches between different operational modes by engaging or disengaging specific planetary gear stages. When high torque is needed, the system engages the compound planetary gear reduction; when high speed is needed, it operates in direct drive or reduced reduction mode. This dynamic adaptability resolves the trade-off between torque and speed performance.
Solution Approach 2:
The transmission system changes its effective gear ratio parameter based on operational requirements. By varying the engagement state of different planetary gear stages, the system can adjust its speed reduction ratio to optimize performance for either high-speed applications or high-torque applications, eliminating the need to compromise one parameter for the other.
3Force
If early cordless rotary power tools were used for low-speed, high torque operations, then the torque output was achieved, but energy consumption increased significantly
Solution Approach 1:
The patent replaces the traditional mechanical approach of using oversized motors and direct-drive transmissions with a optimized planetary gear transmission system. This mechanical substitution allows smaller, more energy-efficient motors to achieve the same torque output through gear multiplication, significantly reducing energy consumption during low-speed, high-torque operations while maintaining the required force output.
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
Enables power tools to perform diverse operations with improved efficiency and reduced energy consumption, eliminating the need for multiple tools by providing a broad range of speed and torque capabilities suitable for both standard and demanding tasks.
Implementation Method 1
a compound planet gear having a first planet gear and a second planet gear coupled together for common rotation on the output planet carrier
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.