Impact Tool Output Shaft Segmentation for Stress Distribution
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Solution Overview
Problem
Impact tools, such as impact wrenches, suffer from a significant stress concentration point at the square shaft of the output shaft, leading to premature breakage and reduced tool life due to the small force-bearing area at the joint between the output shaft and the tool accessory.
Innovation Solution
The impact tool design includes a first output shaft with a partially nested region greater than or equal to 3 mm, where the second output shaft is connected to the first output shaft, forming a stable connection with a polygonal opening and a larger force-bearing surface, and optionally featuring varying hardnesses across different regions to enhance durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the output shaft is integrated with a square shaft at the front end, then the structure is simplified and manufacturing is easier, but the square shaft is prone to break off due to stress concentration and small force-bearing area
Solution Approach 1:
The output shaft is divided into two separate components: a first output shaft and a second output shaft. The first output shaft includes a force-bearing region with a larger area to distribute impact forces, while the second output shaft has a square cross-section for tool accessory mounting. This segmentation eliminates the stress concentration point at the integrated square shaft while maintaining manufacturing simplicity through modular assembly.
Solution Approach 2:
A connector is introduced as an intermediary component between the first output shaft and the second output shaft. The connector includes a buffer that absorbs impact forces, preventing direct transmission of stress to the square shaft region. This intermediary structure protects the vulnerable square shaft area while maintaining the functional integrity of the output shaft system.
2Volume of moving object
If the force-bearing area at the joint between output shaft and tool accessory is reduced, then the structure is more compact, but the impact reaction force causes premature breakage and reduced tool life
Solution Approach 1:
The force-bearing region of the first output shaft is designed with a larger cross-sectional area in the radial dimension to distribute impact forces. By increasing the area in this dimension, the impact reaction force is spread over a larger region, reducing stress concentration and preventing premature breakage, thereby extending tool life without significantly increasing the overall volume of the output shaft system.
Data Source
AI summary
An impact tool includes: an electric motor including a drive shaft rotating about a first axis; an impact member configured to be driven by the electric motor; an output mechanism configured to be provided with an impact force by the impact member; a transmission mechanism disposed between the electric motor and the impact member and transmitting torque outputted by the drive shaft to the impact member; and a power supply configured to supply electrical energy to the impact tool. The output mechanism includes: a first output shaft driven by an impact member to rotate, a second output shaft connected to the first output shaft and retained at the front-most end of the impact tool to be mounted with a tool accessory. The front end surface of the first output shaft is configured as a force-bearing region bearing an impact reaction force from the tool accessory.