Compound Planetary Transmission for Compact High-Torque Impact Tools
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Solution Overview
Problem
Existing impact tools face challenges in achieving high torque and power output while maintaining a compact size, as they often require multiple stages of planetary gear reductions, which increase tool size and complexity.
Innovation Solution
A compact impact tool design utilizing a planetary transmission with a single stage of compound planet gears, providing a high speed reduction ratio of at least 14:1 within a small volume, allowing for efficient torque and power delivery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If multiple stages of planetary gear reductions are used to achieve high torque and power output, then the torque and power output are improved, but the tool size and structural complexity increase
Solution Approach 1:
The patent combines two planetary gear stages into a single integrated stage with compound planet gears. The first and second planet gears are mounted on the same planet carrier and mesh with different gears (sun gear and ring gear respectively), allowing two speed reduction ratios to be achieved simultaneously in one compact structure rather than requiring two separate stages
Solution Approach 2:
The compound planet gear structure nests multiple gear functions within a single planetary stage. The first planet gear and second planet gear are positioned concentrically and share the same planet carrier, creating a nested arrangement where one gear system is effectively contained within the spatial envelope of another, maximizing space utilization and reducing overall tool size
2Speed
If multiple stages of planetary gear reductions are used to achieve high speed reduction ratio, then the speed reduction ratio is improved, but the device complexity increases
Solution Approach 1:
The patent merges two separate planetary gear stages into one unified stage by introducing compound planet gears. The first planet gear meshes with the sun gear while the second planet gear meshes with the ring gear, both rotating on the same planet carrier. This integration reduces the number of independent components and simplifies the overall structure while achieving the same cumulative speed reduction ratio
Solution Approach 2:
The planet carrier serves multiple functions simultaneously: it supports both the first planet gear and the second planet gear, transmits rotational motion from the sun gear to the ring gear, and provides the output shaft connection. This multi-functionality reduces the need for additional components and simplifies the transmission system
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
The compact design achieves higher torque and power output efficiently, enabling fastening into tough materials like concrete and reducing battery power consumption, while maintaining a small form factor.
Implementation Method 1
The planetary transmission includes a sun gear rotatably driven by the motor output shaft, a planet carrier rotatably driving the cam shaft, a ring gear rotationally fixed relative to the tool housing, a first planet gear mounted to the planet carrier and meshed with the sun gear but not meshed with the ring gear and a second planet gear mounted to the carrier and meshed with the ring gear but not meshed with the sun gear
Implementation Method 2
a spring that biases the hammer toward the spindle
Implementation Method 3
The impact power tool includes a motor disposed in the rearward portion of the housing and having a motor output shaft
Data Source
AI summary
An impact power tool includes one or more of the following features including a housing, a motor, an output spindle, a rotary impact assembly, and a planetary transmission having a fixed ring gear and rotatable planet gear carrier. In an aspect, the planetary transmission is configured to transmit rotational motion from a motor output shaft to a cam shaft at a single overall speed reduction ratio. The planetary transmission includes a sun gear rotatably driven by the motor output shaft, a planet carrier rotatably driving the cam shaft, a ring gear rotationally fixed relative to the tool housing, a first planet gear mounted to the planet carrier and meshed with the sun gear but not meshed with the ring gear and a second planet gear mounted to the carrier and meshed with the ring gear but not meshed with the sun gear.