Three-Point Bearing System for Hand-Held Power Tools
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Solution Overview
Problem
The existing hand-held power tools with pneumatic percussion mechanisms driven by linear motors face challenges in achieving a friction-free yet secure rotor bearing, often requiring precise manufacturing tolerances or complex fitting processes, which can lead to increased friction and reduced service life due to overdetermined bearing systems.
Innovation Solution
A simplified bearing device with a three-point mounting system, comprising a runner bearing and an exciter piston bearing, allows the rotor to pivot transversely, providing a statically determined yet non-overdetermined support, reducing frictional forces and eliminating the need for complex fitting, thereby enhancing the tool's efficiency and service life.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the rotor is mounted directly in the stator with four flat partial air gaps, then the rotor bearing is overdetermined, but this leads to complex fitting processes and increased friction
Solution Approach 1:
The bearing system is segmented into three distinct bearing points instead of a continuous four-gap structure. The first and second bearings are positioned at opposite sides of the runner, with the third bearing providing longitudinal guidance, creating a statically determined three-point support system that eliminates over-constraint
Solution Approach 2:
Instead of mounting the rotor directly in the stator with multiple constraining air gaps, the invention inverts the approach by using a separate bearing device with three strategically positioned bearings. This inversion transforms the overdetermined four-gap system into a statically determined three-point bearing system, allowing for simpler fitting while maintaining reliability
2Manufacturing precision
If manufacturing tolerances are made very small to ensure precise rotor positioning, then bearing precision is improved, but production costs increase significantly
Solution Approach 1:
The three-point bearing system concentrates the bearing function at three specific locations rather than requiring uniform precision across the entire rotor-stator interface. This allows for reasonable manufacturing tolerances in the overall assembly while maintaining precise positioning at the critical bearing points, reducing production costs
3Measurement precision
If the runner is mounted with tight tolerances to prevent incorrect positioning, then bearing accuracy is improved, but frictional heat generation increases
Solution Approach 1:
The bearing system is designed to accommodate dynamic positioning of the runner during operation. The three-point bearing configuration with the third bearing providing longitudinal guidance allows the runner to maintain accurate positioning while permitting natural movement and expansion, reducing frictional heat generation compared to rigid tight-tolerance mounting
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 three-point bearing system reduces frictional heat generation and operational constraints, resulting in improved efficiency and extended service life of the hand-held power tool by minimizing unnecessary constraint forces and simplifying the manufacturing process.
Implementation Method 1
a linear motor with a runner (600), an exciter piston (400) which is mechanically rigidly coupled to the runner (600), and a bearing device (100)
Data Source
AI summary
The power tool (800) has a supporting unit (100) that is equipped with rotor bearings (10,20,120) for supporting the longitudinally movable bearings of a rotor (600), and with an exciter piston bearing (180) for supporting the longitudinally moving components of a hammer piston (400). The rotor bearings are pivoted at opposite sides of rotor together with hammer piston around movement axis (210) corresponding to transverse axes (211,212) of bearings. The exciter piston bearing is provided with respect to a longitudinal guide along movement axis of hammer piston.