Torque-Limited Impact Tool Asymmetric Anvil Hammer Geometry
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Solution Overview
Problem
Conventional impact tools lack effective torque limiting mechanisms, leading to potential over-tightening of fasteners during installation and inefficient loosening of fasteners, which can result in damage or difficulty in operation.
Innovation Solution
The impact tool incorporates a shaft with a first helical groove and a hammer with a second helical groove, where a ball couples the hammer to the shaft, allowing axial travel, and an anvil with lugs forming acute and obtuse impact surfaces. The obtuse impact surface of the hammer lug and the acute impact surface of the anvil lug are angled to limit torque in one direction while allowing high torque in the opposite direction, achieved through specific angle configurations between 105° and 165° for the obtuse angle and 15° and 75° for the acute angle.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional impact tools are used for fastener installation, then fastening operation can be performed, but torque cannot be limited leading to potential over-tightening of fasteners
Solution Approach 1:
The patent changes the geometric parameters of the impact surfaces by providing an obtuse angle (greater than 90 degrees) on the hammer impact surface and an acute angle (less than 90 degrees) on the anvil impact surface. This angular parameter configuration creates inherent torque limitation during the impact process, preventing over-tightening while maintaining reliable fastener installation.
Solution Approach 2:
The patent applies asymmetry by making the hammer and anvil impact surfaces geometrically asymmetric with respect to the axis of rotation. The obtuse angle on the hammer side and acute angle on the anvil side create asymmetric force distribution during impact, which inherently limits torque in the tightening direction while allowing efficient loosening in the opposite direction.
2Ease of operation
If conventional impact tools are used for fastener loosening, then loosening operation can be performed, but torque efficiency is reduced leading to difficulty in operation
Solution Approach 1:
The patent inverts the approach by configuring impact surfaces that limit torque in one rotational direction (tightening) while maximizing torque in the opposite direction (loosening). The asymmetric angular configuration reverses the force distribution depending on rotation direction, providing high torque efficiency for loosening operations.
Solution Approach 2:
The patent changes the operational parameters by providing different torque characteristics for different rotation directions through the fixed geometric configuration of the impact surfaces. The obtuse and acute angle arrangement automatically adjusts torque delivery based on rotation direction, optimizing both tightening and loosening operations.
3Reliability
If asymmetric impact surfaces with obtuse and acute angles are provided, then torque limiting during tightening is achieved, but device complexity increases
Solution Approach 1:
The patent applies local quality by providing different geometric properties (obtuse vs. acute angles) at specific locations on the hammer and anvil impact surfaces. This localized geometric differentiation creates torque limiting functionality without requiring complex overall mechanism design, maintaining simplicity while achieving precise torque control.
Solution Approach 2:
The patent achieves torque limiting through parameter changes in the geometric configuration of impact surfaces rather than through complex mechanism design. By simply adjusting the angular parameters (obtuse >90° and acute <90°) of existing surface features, torque control is achieved without adding mechanical complexity.
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
This configuration provides torque limiting during tightening, preventing over-tightening of fasteners and enabling efficient loosening by controlling energy transfer, ensuring precise fastener management.
Implementation Method 1
a shaft adapted to rotate about an axis, the shaft having a first helical groove; a hammer having a second helical groove and a hammer jaw with an obtuse impact surface; a ball received in the first and second helical grooves wherein the ball rotationally couples the hammer to the shaft and permits axial travel of the hammer relative to the shaft
Implementation Method 2
the obtuse impact surface of the hammer jaw is adapted to impact the acute impact surface of the anvil jaw when the shaft rotates in a first direction
Implementation Method 3
the obtuse impact surface forms an edge of the hammer lug and the obtuse impact surface is disposed at an obtuse angle with respect to the forward impact face... the acute impact surface being disposed at an acute angle with respect to the rearward impact face
Data Source
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AI summary
An impact tool may include a shaft (22) adapted to rotate about an axis, a hammer (28) having a hammer jaw (74) with an obtuse impact surface (78), and an anvil (30) having an anvil jaw (94) with an acute impact surface (98). The shaft may include a first helical groove (50), and the hammer may include a second helical groove (52). The impact tool may further include a ball (60) received in the first and second helical grooves, wherein the ball rotationally couples the hammer to the shaft and permits axial travel of the hammer relative to the shaft. The obtuse impact surface of the hammer jaw may be adapted to impact the acute impact surface of the anvil jaw when the shaft rotates in a first direction.