Portable Electric Tool Counterweight Balancing via Axial Segmentation
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Solution Overview
Problem
Conventional portable electric tools, such as orbital sanders, face challenges in reducing vibration caused by eccentric circular motion, which requires significant counterweights to balance, leading to increased size and weight.
Innovation Solution
The configuration includes a first weight and a second weight positioned axially differently, with a large specific gravity difference, allowing for reduced mass and size while efficiently generating centrifugal forces to balance the tool, and utilizing a bearing as a spacer to further minimize size and cost.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single counterweight is mounted on the output shaft to reduce vibration, then the static unbalance is solved, but the couple unbalance cannot be effectively addressed and the counterweight mass becomes large
Solution Approach 1:
The single counterweight is divided into two separate counterweights (first counterweight and second counterweight) positioned at different axial locations on the output shaft. This segmentation allows each counterweight to address specific unbalance components, with the first counterweight primarily addressing static unbalance and the second counterweight addressing couple unbalance, thereby reducing the total mass required while effectively solving both types of unbalance.
2Reliability
If two counterweights are positioned at the same axial location to reduce couple unbalance, then the centrifugal forces cancel out, but larger masses are required to achieve balancing
Solution Approach 1:
The two counterweights are positioned at different axial locations along the output shaft, utilizing the axial dimension to create a three-dimensional balancing configuration. This axial separation allows the counterweights to generate centrifugal forces that effectively counteract couple unbalance without requiring large masses, as the forces act at different positions along the shaft axis rather than canceling each other out at the same location.
3Ease of manufacture
If the counterweight has the same specific gravity as the fan, then the structure is uniform, but a large mass is required to generate sufficient centrifugal force for balancing
Solution Approach 1:
The specific gravity of the counterweight material is changed to be higher than that of the fan material. This parameter change allows the counterweight to generate the required centrifugal force for balancing with a smaller mass, since centrifugal force is directly proportional to mass and the higher density material provides more mass per unit volume. This resolves the contradiction by prioritizing balancing effectiveness over structural uniformity.
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 effectively reduces the mass and size of the counterweights required to balance the tool, improving motor cooling performance and maintaining functionality with reduced vibration.
Implementation Method 1
the centrifugal forces respectively applied to the first weight and the second weight can be prevented from being canceled out by each other
Data Source
AI summary
A portable electric tool includes an output shaft extending in an axial direction and configured to be rotatable, a tool accessory configured to perform an eccentric circular motion according to the rotation of the output shaft, a dust collection fan fixed to the output shaft so as to circumferentially surround the output shaft, a motor disposed on an opposite side of the dust collection fan from the tool accessory in the axial direction and configured to provide a rotational driving force to the output shaft, a motor cooling fan disposed between the dust collection fan and the motor in the axial direction, a first weight attached to one of the dust collection fan and the motor cooling fan and having a specific gravity higher than the one of the fans, and a second weight disposed at a position different from the first weight in the axial direction.