Hand Tool Vibration Damping with Dual Resonant Absorbers
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Solution Overview
Problem
Handheld power tools, such as hammer drills, face challenges in effectively damping vibrations along their working axis due to resonant excitations, which can lead to amplification of vibrations rather than absorption, especially when the resonance frequencies of damping mechanisms are not adequately tuned.
Innovation Solution
The implementation of two dampers with distinct resonance frequencies, differing by 2% to 5%, and designed with pendulum arms and mass bodies attached to the tool housing, where the resonance frequencies are adjusted by varying the length of the pendulum arms and mass bodies, ensuring high resonance frequencies in directions perpendicular to the working axis to prevent excitation and enhance vibration absorption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single damper with a specific resonance frequency is used, then vibration absorption is effective at that frequency, but vibration amplification occurs when the excitation frequency matches the resonance frequency
Solution Approach 1:
The single damper is segmented into two separate dampers, each with its own resonance frequency. The first damper has a resonance frequency of 50 Hz and the second damper has a resonance frequency of 63 Hz. This segmentation allows the system to absorb vibrations across a broader frequency range and prevents resonant amplification that would occur with a single damper tuned to one specific frequency.
2Loss of energy
If the resonance frequency of the damper is tuned to match the excitation frequency, then maximum vibration absorption is achieved, but resonant excitation causes vibration amplification
Solution Approach 1:
The resonance frequencies of the dampers are deliberately set to different values (50 Hz and 63 Hz) rather than matching the excitation frequency exactly. This parameter change prevents resonant excitation and vibration amplification while still enabling effective vibration absorption through the distributed frequency response of the two dampers.
3Reliability
If pendulum arms are made rigid to prevent out-of-plane oscillation, then high resonance frequencies are achieved in perpendicular directions, but the complexity of ensuring rigidity increases
Solution Approach 1:
The pendulum arms are constructed as composite structures with high moment of inertia, combining geometric design (length and cross-section) to achieve the desired rigidity properties. This allows the arms to provide sufficient resistance to out-of-plane oscillations and achieve high resonance frequencies in perpendicular directions while maintaining manufacturability.
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 approach results in a wider response range for vibration absorption, preventing amplification and ensuring the tool remains stable during operation by coupling the dampers effectively, thus reducing user discomfort and tool wear.
Implementation Method 1
A resonant excitation of an oscillation of the first damper along the working axis takes place at a first resonance frequency, which differs from a second resonance frequency of the second damper for the oscillation along the working axis
Implementation Method 2
At least two absorbers are provided in the handheld power tool for damping vibrations along the working axis
Implementation Method 3
connected to the housing (15) by means of a leaf spring (23)
Data Source
Figure 1~2
Figure 3
AI summary
The hand-held power tool comprises a linear drive for moving a tool along a working axis, and two vibration absorbers, whose resonant frequencies are different for movement along the working axis. The resonant frequency of the former vibration absorber lies in a frequency band, in which the excited latter vibration absorber oscillates with a deflection.