Rotary Power Tool Vibration Damping for High-Speed Operation
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Solution Overview
Problem
Pneumatic motors in high-speed portable grinding tools do not produce significant vibration, while electric motors with longer rotor shafts experience resonant vibration, leading to tool shaking.
Innovation Solution
A power tool with an electric motor, a first printed circuit board assembly, a battery receptacle, and a vibration damping assembly to attenuate vibrations, along with a light assembly to indicate battery charge, using LEDs and light pipes for external visibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If electric motors with longer rotor shafts are used, then the tool can operate at high speeds, but resonant vibration occurs causing tool shaking
Solution Approach 1:
The patent applies vibration damping elements (such as elastomeric materials, foam, or rubber) positioned between the motor housing and tool housing to preemptively absorb and attenuate resonant vibrations before they propagate through the tool structure. This cushioning approach allows the electric motor to operate at high speeds while preventing the harmful vibration effects that would otherwise occur.
2Object-affected harmful factors
If a vibration damping assembly is added to reduce tool shaking, then vibration is attenuated, but device complexity increases
Solution Approach 1:
The vibration damping assembly is integrated into the existing motor housing and tool housing structures, merging the vibration attenuation function with the structural components rather than adding entirely separate elements. The damping materials are positioned within the housing assembly to reduce vibration while maintaining a compact and relatively simple overall 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
The solution effectively reduces tool vibrations and provides real-time battery charge indication, enhancing user control and safety.
Implementation Method 1
The second printed circuit board assembly has a fuse and a thermistor configured to detect a temperature of the fuse
Implementation Method 2
The light pipes are positioned adjacent the respective LEDs to transmit light emitted from the LEDs to the exterior of the tool housing
Implementation Method 3
a vibration damping assembly to attenuate vibrations
Data Source
AI summary
A power tool includes a housing, an electric motor disposed within the housing, a first printed circuit board assembly configured to selectively supply electric current to the electric motor, causing the electric motor to activate and drive a tool element, and a battery receptacle configured to support a removable battery pack. The battery receptacle has a battery terminal block electrically connected to the battery pack to supply electrical current to the first printed circuit board assembly. The power tool further includes a second printed circuit board assembly electrically connected between the first printed circuit board assembly and the battery terminal block. The second printed circuit board assembly has a fuse and a thermistor configured to detect a temperature of the fuse.