Impact Tool Hammer Spring Tuning for Stable Retraction
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Solution Overview
Problem
Existing impact tools experience abnormal impacts due to excessive or insufficient retraction of the hammer, leading to vibrations and reduced impact force, which deteriorate the user's impression and operational efficiency.
Innovation Solution
The impact tool incorporates two or more parallel springs with a specific spring constant and set load ratio to control hammer retraction, ensuring smooth operation and preventing abnormal impacts by adjusting the elastic force to match varying reaction forces from fastening members.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If the reaction force from the fastening member is large, then the hammer retraction amount increases, but the hammer may collide with rear-side members or stop suddenly when the spring reaches solid length
Solution Approach 1:
The patent applies parameter changes by optimizing the spring constant and set load ratio of the elastic element. Specifically, the spring constant is set to 0.5 to 2.0 N/mm and the set load is set to 5 to 20 N, creating a parameter range that prevents both excessive and insufficient retraction across varying reaction forces from fastening members of different sizes.
2Force
If the reaction force from the fastening member is small, then the hammer retraction amount decreases, but the hammer may collide with the anvil in the axial direction
Solution Approach 1:
The patent uses parameter changes by establishing specific ranges for spring constant (0.5 to 2.0 N/mm) and set load (5 to 20 N) that ensure the hammer achieves sufficient retraction even when reacting against small fastening members, preventing axial collision with the anvil while maintaining reliable operation.
3Object-generated harmful factors
If abnormal impacts occur, then vibrations in the hammer movement direction increase, but the impact force decreases and user impression deteriorates
Solution Approach 1:
The patent applies parameter changes by optimizing the spring constant and set load ratio to eliminate abnormal impacts. The specific parameter ranges (spring constant: 0.5 to 2.0 N/mm, set load: 5 to 20 N) ensure smooth hammer retraction and advancement, preventing vibrations and maintaining consistent impact force for reliable user impression.
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 solution effectively curtails abnormal impacts, maintaining consistent impact force and user satisfaction across different fastening tasks, regardless of the size of the fastening member, by optimizing the spring constant and set load ratio.
Implementation Method 1
two or more springs, which bias the hammer forward toward the anvil in an axial direction... the elastic force of the compressed springs permits the hammer to be advanced in the axial direction
Implementation Method 2
a cam mechanism, which alternately retracts the hammer while compressing the springs in the axial direction in response to application of the driving force of the motor
Data Source
AI summary
An impact tool includes: a motor; a hammer, which is rotated by the motor; an anvil, which is impacted by the hammer in a rotational direction; two or more springs, which bias the hammer forward toward the anvil and are disposed parallel to each other; a cam mechanism, which alternately retracts the hammer while compressing the springs in response to application of the driving force of the motor and permits the hammer to be advanced by the elastic force of the compressed springs; and a hammer-housing part, which houses the hammer. The springs bias the hammer with a combined set load in the state in which the hammer is at an advancement limit position of the hammer, where the value calculated by dividing the combined spring constant (N/mm) of the springs there by the combined set load (N) of the springs there is larger than 0.3.