Oscillating Power Tool Axial Elastic Coupling Noise Reduction
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Solution Overview
Problem
Conventional oscillating rotary electric power tools generate abnormal noise due to the hitting of projected and depressed portions during rotation, and the use of an elastic body to prevent this noise results in insufficient durability as it can be torn off by rotational forces.
Innovation Solution
An elastic body, such as an O-ring, is interposed between the coupling member and the crankshaft in the same axial direction to increase rotational resistance and prevent noise by ensuring the coupling member and crankshaft adhere to each other, with the O-ring being sandwiched between end faces to enhance durability and reduce the risk of being squashed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If an elastic body is inserted between the projected portion and depressed portion in the circumferential direction to prevent abnormal noise, then the noise is reduced, but the elastic body can be torn off by rotational forces resulting in insufficient durability
Solution Approach 1:
The patent changes the placement dimension of the elastic body from the circumferential direction to the axial direction. The elastic body is positioned between the projected portion of one component and the depressed portion of another component along the axial direction, preventing circumferential movement while avoiding rotational forces that would tear the elastic body.
Solution Approach 2:
The elastic body serves as an intermediary element between the coupling member and crankshaft. It fills the clearance gap axially, allowing the two components to adhere to each other while accommodating minor misalignments, thereby preventing abnormal noise without being subjected to damaging rotational forces.
2Adaptability or versatility
If the projected portion and depressed portion are fitted with an allowance in the rotational direction, then the coupling is flexible, but the portions hit each other generating abnormal noise
Solution Approach 1:
The patent addresses the noise issue by acting in a different dimension (axial direction) rather than trying to eliminate the circumferential allowance. The elastic body is positioned axially to prevent the projected and depressed portions from hitting each other, while the circumferential flexibility is maintained for adaptability.
Solution Approach 2:
The elastic body acts as a cushioning element positioned in advance between the coupling member and crankshaft. It prevents the projected portion from hitting the depressed portion by providing elastic compliance, thereby cushioning against the impact that would generate abnormal noise.
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 prevents abnormal noise by increasing rotational unity between the coupling member and crankshaft while improving the durability of the elastic body, as it elastically deforms to adhere without being subjected to squashing forces, and allows for a stronger coupling member compared to the crankshaft.
Implementation Method 1
an elastic body is interposed between the coupling member and the crankshaft in a direction of the identical axis to fit the coupling member and the crankshaft together in the depression and projection fitting structure
Data Source
AI summary
An oscillating rotary electric power tool, in which a spindle with a distal end tool attached thereto is projected downward from a front end portion of a housing accommodating a motor, and the housing also accommodates a coupling member rotatable integrally with an output shaft of the motor, a crankshaft fitted with the coupling member in a depression and projection fitting structure, and a link member to which the spindle is fixed and power is transmitted from the crankshaft to rotate clockwise and counterclockwise in an oscillating manner so that the link member will be driven by the motor to rotate the spindle clockwise and counterclockwise in the oscillating manner, wherein an elastic body is interposed between the coupling member and the crankshaft in the same axial direction as the output shaft.