Rotary Impact Tool Hammer Dynamics for Screw Tightening
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Solution Overview
Problem
Conventional impact tools often face insufficient striking force in the rotational direction, which can be improved without increasing the torque required to detach the engaging portions, thereby complicating screw tightening operations.
Innovation Solution
The impact tool incorporates a rotating member concentric with the tool support member, allowing the hammer to move axially and rotationally, and a control unit that adjusts rotation speed and stroke frequency to enhance striking force without increasing detachment torque.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If the spring constant of the elastic member is increased to increase the striking force, then the striking force in the rotational direction is improved, but the torque required to detach the first engaging portion from the second engaging portion is increased, making screw tightening work difficult
Solution Approach 1:
The hammer is designed to move dynamically in the axial direction relative to the rotating member, allowing it to approach and strike the tool support member during rotation. This dynamic movement enables the system to generate high striking force through the elastic member's rebound action without requiring the engaging portions to withstand high static torque, thus resolving the contradiction between striking force and ease of operation
Solution Approach 2:
The hammer performs periodic striking actions as the rotating member rotates, with the first engaging portion climbing over the second engaging portion during each rotation cycle. This periodic action allows the elastic member to repeatedly store and release energy, generating high striking force without requiring continuously high torque, thereby maintaining ease of operation
2Force
If the rotational force required to tighten the screw member increases, then the striking force is improved, but the hammer moves in the axial direction and the first engaging portion climbs over the second engaging portion, reducing tightening speed
Solution Approach 1:
The hammer's axial movement is dynamically coupled with the rotation of the rotating member. As the rotating member rotates, the hammer moves axially to approach the tool support member, and the first engaging portion climbs over the second engaging portion in a controlled manner. This dynamic coordination allows the system to generate high striking force while maintaining rotation speed, thus resolving the contradiction between striking force and tightening speed
Solution Approach 2:
The system introduces axial movement as an additional dimension to the rotational motion. The hammer moves not only rotationally with the rotating member but also in the axial direction toward the tool support member. This multi-dimensional motion allows the engaging portions to climb over each other smoothly while maintaining both striking force and rotation speed, thereby resolving the contradiction between force and productivity
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 increases the striking force in the rotational direction, speeding up the screw tightening process while maintaining manageable torque requirements.
Implementation Method 1
a spring as an elastic member which presses the hammer toward the tool support member
Implementation Method 2
a first cam groove provided in an outer circumferential surface of the spindle; a second cam groove provided in an inner circumferential surface of the hammer; a cam ball held by the first cam groove and the second cam groove
Implementation Method 3
the first engaging portion strikes the second engaging portion. In this manner, a striking force in the rotational direction is applied from the hammer to the tool support member
Data Source
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AI summary
In order to provide an impact tool which is capable of increasing a striking force in a rotational direction of being applied from a hammer to an anvil, the impact tool includes: an electric motor; an anvil (27) which supports a work tool and is driven by the electric motor; and a hammer (43) which applies the striking force in the rotational direction to the anvil (27). The impact tool is provided with: a spindle (40) which is arranged to be concentric with the anvil (27), supports the hammer (43) to be movable in an axial direction and the rotational direction with respect to the anvil (27), and transmits motive power of the electric motor to the anvil (27); and a control unit which controls rotation speed of the electric motor. The number of strokes of the anvil (27) due to one rotation of the hammer (43) differs in response to rotation speed of the electric motor.