Protective Grille Rib Tuning for Blower Noise Reduction
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Solution Overview
Problem
Hand-held blower and suction devices experience high noise levels during operation due to resonance vibrations caused by air flowing through grid-like guards, which are annoying for operators.
Innovation Solution
A protective device with ribs and disruptive bodies that form oscillation systems with different natural frequencies, reducing resonance vibrations and noise emissions by shifting natural frequencies outside the excitation range, and featuring a connection point that is rotationally movable but not translationally oscillable, with disruptive bodies of varying masses and positions to influence vibration systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If protective grilles are provided on the work equipment, then operator safety is improved, but noise emissions increase due to resonance vibrations
Solution Approach 1:
The patent applies mechanical vibration principles by introducing disruptive elements that create controlled vibrations to counteract the resonant vibrations of the protective grille. These disruptive elements are designed to vibrate at frequencies that interfere with and reduce the resonant vibrations caused by airflow through the grille, thereby lowering noise emissions while maintaining the protective function.
Solution Approach 2:
The patent changes the physical parameters of the protective grille by adding disruptive elements with specific masses and dimensions. These elements alter the natural frequencies and vibration characteristics of the grille structure, shifting the resonant frequencies away from the excitation frequencies caused by airflow, thus reducing noise emissions.
2Object-generated harmful factors
If disruptive elements are added to rib sections, then noise emissions are reduced by shifting natural frequencies, but device complexity increases
Solution Approach 1:
The patent segments the protective device into modular rib sections, each potentially equipped with its own disruptive elements. This segmentation allows for independent optimization of each rib section and facilitates easier manufacturing, assembly, and maintenance, thereby managing device complexity while achieving noise reduction across the entire protective grille.
Solution Approach 2:
The patent applies local quality by placing disruptive elements selectively on specific rib sections rather than uniformly across the entire protective grille. This localized approach allows for targeted noise reduction at critical resonant areas while minimizing the overall addition of complexity to the protective device structure.
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
Significantly reduces noise emissions by altering the natural frequencies of the rib sections, preventing resonance and thus minimizing disturbing vibrations.
Implementation Method 1
When air flows through the grille, it is externally excited and begins to vibrate. If the excitation frequency caused by the airflow corresponds to a natural frequency of the excited grille structure, resonance occurs.
Implementation Method 2
The rib section has a natural frequency on its own. The rib section and the disruptive element form an oscillating system with a system natural frequency. The system natural frequency and the natural frequency of the rib section are different.
Implementation Method 3
The connection point forms an attachment point for the adjacent rib sections, which is fixed translationally. Thus, the connection point is not capable of translational movement.
Data Source
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AI summary
The invention relates to a protective device (10) for an intake or blowing channel of a work device. The protective device (10) comprises at least one rib (11) with a longitudinal direction (12). The at least one rib (11) has at least one rib section (13, 14), wherein the rib section (13, 14) extends along the longitudinal direction (12) of the rib (11) from a first end (18) to a second end (19) and has a natural frequency on its own. A disruptive element (20) that is translationally oscillatable with the rib section (13, 14) is arranged on the rib section (13, 14) between the first end (18) and the second end (19). The rib section (13, 14) and the disturbance body (20) form a vibration system (21) with a system natural frequency, wherein the system natural frequency and the natural frequency of the rib section (13, 14) are different.