Sonotrode Non-Central Thickening for Frequency Separation
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Solution Overview
Problem
Existing sonotrodes used in ultrasonic processing experience undesirable vibration modes, particularly the triangular frequency, which leads to non-homogeneous energy transfer and unwanted audible oscillations due to coupling with the main frequency, resulting in poorer welding results and increased hearing protection requirements.
Innovation Solution
A sonotrode design featuring non-central convex thickening on at least one main surface, positioned between 0.25x and 2x the sealing surface width from the wheel axis, to increase the difference between the triangular and main frequencies, thereby minimizing the influence on the main frequency and maximizing the separation of these modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the sonotrode is designed with a standard uniform structure, then the manufacturing is simple and cost-effective, but the triangular frequency is too close to the main frequency causing mode coupling and audible oscillations
Solution Approach 1:
The patent applies local quality by introducing a thickened portion only in specific regions of the sonotrode rather than changing the entire structure. This localized modification changes the mass distribution and stiffness characteristics in targeted areas, effectively shifting the triangular frequency away from the main frequency while maintaining uniform structure elsewhere, thus resolving the mode coupling issue without excessive complexity
Solution Approach 2:
The patent employs asymmetry by positioning the thickened portion at specific locations that create an asymmetric mass distribution. This asymmetric design intentionally disrupts the symmetry of vibration modes, causing the triangular frequency to shift to a different value than the main frequency, thereby preventing mode coupling and audible oscillations
2Object-generated harmful factors
If the triangular frequency is shifted further from the main frequency, then the mode coupling is reduced and audible oscillations are minimized, but the structural modification becomes more complex
Solution Approach 1:
The thickened portion is applied locally rather than throughout the entire sonotrode, creating the necessary frequency separation with minimal structural modification. This localized approach achieves the goal of reducing audible oscillations while keeping the overall device complexity low
Solution Approach 2:
The patent changes physical parameters (mass distribution, thickness) in specific regions to shift the triangular frequency. By adjusting the thickness and position of the thickened portion, the frequency parameters are optimized to maximize separation from the main frequency while minimizing structural 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
The design effectively reduces the excitation of undesirable triangular frequency, enhancing energy transfer homogeneity and reducing audible oscillations, resulting in improved ultrasonic processing outcomes.
Implementation Method 1
a standing cylindrical wave is excited in the sonotrode, i.e. the sonotrode has a resonant frequency at which a standing cylindrical wave forms in the sonotrode
Implementation Method 2
the sonotrode has a resonant frequency at which a standing cylindrical wave forms in the sonotrode
Implementation Method 3
the sealing surface vibrates at an ultrasonic frequency in the radial direction
Implementation Method 4
the coupling of the modes leads to an oscillation whose frequency is determined by the difference between the main frequency and the triangular frequency
Data Source
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AI summary
The invention relates to a sonotrode with a wheel-shaped portion with a wheel axis and a diameter d, having two substantially circular main surfaces and a substantially cylindrical sealing surface which connects the main surfaces and has the width b. The aim of the invention is to provide a corresponding sonotrode in which the triangular frequency significantly differs from the main frequency. According to the invention, this is achieved in that at least one main surface has a non-central thickened portion which has a convex region that is not arranged on the wheel axis when seen in a sectional view perpendicular to the main surface.