Progressive Compression Spring for Vibration Damping in Hand-Held Power Tools
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Solution Overview
Problem
Existing hand-held power tools experience significant vibration at medium to high contact pressures, which is not adequately reduced by existing anti-vibration systems without increasing spring travel.
Innovation Solution
A cylindrically progressive compression spring with two or three stiffness ranges of different rigidity levels is used in the anti-vibration unit, allowing for a non-linear spring characteristic and adjustable stiffness without a thread dome, reducing vibration effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a conventional linear spring is used in the anti-vibration unit, then the structure is simple, but vibration reduction at medium to high contact pressures is insufficient
Solution Approach 1:
The spring is divided into multiple sections along its length, with each section having a different wire diameter to create varying stiffness characteristics. This local variation in geometry allows the spring to provide optimized vibration reduction at different compression stages without requiring multiple separate components
Solution Approach 2:
The wire diameter parameter is varied along the length of the spring to create a progressive stiffness characteristic. By changing this geometric parameter, the spring transitions from a linear to a non-linear force-deflection behavior, improving vibration reduction effectiveness at medium to high contact pressures
2Object-affected harmful factors
If the spring travel is increased to reduce vibration, then vibration reduction improves, but the device size increases
Solution Approach 1:
By modifying the wire diameter parameter along the spring length, the spring achieves a non-linear force-deflection curve that provides enhanced vibration reduction within a limited travel range. The progressive stiffness allows effective vibration damping without requiring excessive spring compression distance
Solution Approach 2:
Different sections of the spring with varying wire diameters provide localized stiffness optimization, allowing the spring to deliver maximum vibration reduction effectiveness within a compact travel envelope rather than requiring uniform high stiffness throughout the entire spring length
3Adaptability or versatility
If a threaded boss is used to attach the spring, then the spring can be securely mounted, but the adjustment of stiffness profile becomes complex
Solution Approach 1:
The threaded boss attachment feature is removed from the spring design. Instead, the spring is secured through alternative means that allow for simpler stiffness adjustment, possibly through direct placement or simplified retention mechanisms that do not require threading operations
Solution Approach 2:
Stiffness adjustment is achieved by replacing springs with different wire diameter profiles rather than modifying the attachment structure. This parameter-based approach to stiffness control simplifies the attachment mechanism while maintaining versatility
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 reduces vibration in hand-held power tools at medium to high contact pressures without increasing spring travel, providing a cost-effective and structurally simple means to manage stiffness, thereby enhancing user comfort and tool performance.
Implementation Method 1
the anti-vibration unit comprises a spring wire coil with several turns oriented along the vibration axis
Implementation Method 2
a non-linear spring characteristic of the coiled spring wire can be achieved... effectively reduces vibration in hand-held power tools
Data Source
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AI summary
The invention relates to an electric hand-held power tool (100), in particular a drill or chisel hammer, comprising a percussion assembly (10) which vibrates along a vibration axis (A) and a handle assembly (20) which is vibration-decoupled via an anti-vibration unit (30). The anti-vibration unit (30) has a coil spring (35) which is oriented along the vibration axis (A) and which comprises multiple windings, wherein the coil spring (35) is designed as a cylindrically progressive compression spring (36) with two rigidity regions (S1, S2) with different degrees of rigidity.