Random Orbital Tool Eccentric Bearing Design
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Solution Overview
Problem
Conventional random orbital power tools experience significant vibrations and mechanical stress due to the large distance between the eccentric element and its bearings, leading to inefficient absorption of lateral forces and tilting moments at high speeds.
Innovation Solution
The power tool incorporates at least one separate bearing for the eccentric element, with a rotationally symmetric external surface and a mechanical gear arrangement, including meshing gear wheels, to directly guide the eccentric element and absorb lateral forces, reducing vibrations and allowing for a more compact design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the eccentric element is positioned at a large distance from the drive shaft bearings, then the structural design is simplified, but lateral forces and tilting moments increase significantly at high speeds
Solution Approach 1:
The patent divides the bearing support function into two separate systems: (1) drive shaft bearings that support the motor shaft, and (2) separate bearings that directly support the eccentric element. This segmentation allows each bearing system to be optimized for its specific function, with the separate bearings positioned close to the eccentric element to minimize lateral forces and tilting moments while maintaining simplified structural design.
2Device complexity
If the eccentric element is positioned at a large distance from the bearings, then the mechanical structure is simpler, but vibrations increase due to inefficient absorption of lateral forces
Solution Approach 1:
The patent introduces separate bearings as intermediary elements that directly support the eccentric element. These bearings act as mediators between the eccentric element and the tool housing, providing a dedicated support path that efficiently absorbs lateral forces and reduces vibrations without complicating the overall mechanical structure.
3Device complexity
If the eccentric element forms an integral part of the drive shaft, then torque transmission is simplified, but adaptability for different configurations is limited
Solution Approach 1:
The patent segments the torque transmission path by introducing a gear arrangement as a separate component between the motor and the eccentric element. This allows the eccentric element to be independently designed and configured while maintaining efficient torque transmission through the gear mechanism, thereby enhancing adaptability for different configurations.
4Object-generated harmful factors
If separate bearings are added for the eccentric element, then vibrations are reduced, but device complexity increases
Solution Approach 1:
The separate bearings serve multiple functions simultaneously: they support the eccentric element, absorb lateral forces, reduce vibrations, and enable compact positioning. This multi-functionality justifies the addition of the bearings by delivering multiple benefits from a single component addition.
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
This configuration significantly reduces vibrations and mechanical stress, enabling more efficient operation at high speeds while allowing for a more compact and lightweight power tool design.
Implementation Method 1
The separate bearing can absorb the lateral forces directly from the rotating eccentric element (including the backing pad and a counter weight connected thereto). This has the advantage that vibrations of the power tool during its operation resulting from the eccentric element (including the backing pad and a counter weight connected thereto) at high speeds (up to 12,000 rpm) can be significantly reduced.
Implementation Method 2
The mechanical gear arrangement is provided functionally between a driving shaft driven by the motor and the eccentric element. The mechanical gear arrangement comprises at least two meshing gear wheels, wherein at least one of the gear wheels is attached to the eccentric element in a manner adapted for transmitting torque to the eccentric element.
Data Source
AI summary
A hand-held/hand-guided random orbital polishing/sanding power tool has a static body and a motor for driving an eccentric element with a rotational movement about a first rotational axis, and a plate-like backing pad rotatably connected to the eccentric element about a second rotational axis. The first/second axes extend parallel to and spaced apart from one another. Part of an external circumferential surface of the eccentric element has a rotational symmetry re the first axis to form a rotationally symmetric part. The tool has a first bearing between the rotationally symmetric part and the static body so the eccentric element is rotatably guided re the static body about the first axis, and also having a mechanical gear arrangement with two meshing gear wheels arranged between the motor's drive shaft and the eccentric element, and one meshing gear wheel attached to the eccentric element for transmitting torque thereto.