Impact Wrench Anvil Shank-Head Diameter Ratio
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Solution Overview
Problem
Anvil assemblies in impact wrenches experience high stress levels due to striking rotational force, leading to fatigue failure and potential fracture of the anvil head, reducing their operational life.
Innovation Solution
The design of the anvil features a shank and head with a diameter ratio between approximately 1:1 and 1.35:1, minimizing stress through a transition zone that reduces the stress between the shank and head, thereby increasing the anvil's useful life by distributing the force more effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the anvil head diameter is increased to withstand high stress, then the strength is improved, but the stress concentration at the shank-head junction increases leading to fatigue failure
Solution Approach 1:
The patent applies parameter changes by optimizing the diameter ratio between the shank and head to a specific range (1:1 to 1.35:1). This quantitative parameter adjustment reduces stress concentration at the junction while maintaining the head's strength to withstand high impact loads, thereby resolving the contradiction between strength and fatigue resistance
Solution Approach 2:
The patent implements local quality by creating a transition zone with specific geometric characteristics at the shank-head junction. This localized structural modification distributes stress more evenly in the critical junction area, preventing stress concentration that would lead to fatigue failure while preserving the overall strength of the anvil head
2Loss of substance
If the anvil shank diameter is decreased to reduce material usage, then the manufacturing cost is reduced, but the stress distribution becomes uneven leading to head fracture
Solution Approach 1:
The patent uses parameter changes by defining an optimal diameter ratio range (1:1 to 1.35:1) that balances material efficiency with structural integrity. This parameter optimization ensures adequate material distribution to prevent head fracture while minimizing overall material consumption
Solution Approach 2:
The patent applies local quality by designing a transition zone with specific geometric properties that ensures adequate material presence at the critical shank-head junction. This localized structural feature prevents stress concentration and head fracture while allowing the rest of the anvil to use material efficiently
Data Source
AI summary
An anvil for use with an impact wrench includes a first end, a second end opposite the first end, a shank adjacent the first end, and a head adjacent the second end. The shank includes a diameter and an outer cylindrical surface that defines a longitudinal axis that extends centrally through the anvil between the first end and the second end. The head includes a plurality of planar faces and an outer cylindrical surface. The outer cylindrical surface defines a diameter of the head. A ratio between the diameter of the shank and the diameter of the head is between approximately 1:1 and approximately 1.35:1.