Propeller Apparatus Elastic Damper Stress Distribution
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Solution Overview
Problem
Existing propeller apparatuses suffer from early deterioration and damage of impact-absorbing dampers due to stress concentration and accumulation of debris, leading to increased maintenance costs and reduced functionality.
Innovation Solution
A propeller apparatus with a tubular member and elastic bodies of spherical or columnar shape, allowing for directional change and easy cleaning, which are held between concave portions to distribute stress and prevent accumulation of debris.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a damper is disposed in a space surrounded by the hub, bushing, and ribs to absorb impact, then the impact between propeller shaft and propeller is reduced, but the damper suffers from stress concentration and early deterioration
Solution Approach 1:
The patent divides the single damper into multiple dampers (typically three dampers arranged at 120-degree intervals). Each damper handles a portion of the impact loads, distributing the stress concentration across multiple components. This segmentation prevents any single damper from bearing excessive localized stress, thereby extending the overall service life while maintaining impact absorption functionality.
Solution Approach 2:
The patent introduces circumferential grooves on the outer surface of the bushing and corresponding protrusions on the inner surface of the hub. These local structural modifications create defined contact zones that guide and distribute the impact forces more evenly across the damper surfaces. The grooves and protrusions locally modify the stress distribution pattern, preventing concentrated stress at specific points and reducing premature damper failure.
2Reliability
If ribs protrude inward and outward to press and deform the damper for impact absorption, then the impact is reduced, but debris accumulates in the spaces between ribs and dampers
Solution Approach 1:
The patent removes the rib structures that created debris-trapping spaces and replaces them with circumferential grooves on the bushing outer surface. This extraction of the harmful rib geometry eliminates the crevices where debris could accumulate, while the grooves maintain the necessary structural function for damper deformation and impact absorption. The harmful factor (debris accumulation zones) is extracted from the design.
Solution Approach 2:
Instead of having protruding ribs creating enclosed spaces that trap debris, the patent inverts the approach by using recessed grooves on the bushing that work with protrusions on the hub. This inversion opens up the structure, preventing debris entrapment while maintaining the mechanical deformation function for impact absorption.
3Power
If the bushing is non-rotatably fixed to both hub and propeller shaft, then rotation transmission is efficient, but the structure lacks flexibility to handle impact loads
Solution Approach 1:
The patent creates a dynamic system where the bushing can rotate relative to both the hub and the propeller shaft through the intermediary dampers. The circumferential grooves on the bushing and protrusions on the hub allow controlled relative motion. This dynamic configuration enables the system to adapt to impact loads by allowing temporary slip and dampers deformation, while still transmitting rotational power efficiently during normal operation.
Solution Approach 2:
The dampers serve as intermediary elements between the bushing and the hub protrusions. They mediate the interaction between the rotating bushing and the stationary hub, allowing controlled relative motion while transmitting power. The dampers absorb impact energy through deformation and friction, providing flexibility to the otherwise rigid power transmission path.
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
Prevents early deterioration and damage of elastic bodies by distributing stress and reducing debris accumulation, thereby maintaining impact absorption functionality and reducing maintenance costs.
Implementation Method 1
a plurality of elastic bodies provided between the tubular member and the hub, and configured to absorb an impact between the propeller shaft and the propeller
Implementation Method 2
the elastic bodies are rotatably held between the first concave portions and the second concave portions facing each other
Data Source
AI summary
A propeller apparatus of a ship propulsion machine includes a tubular member inserted into an insertion hole so as to be movable in a circumferential direction with respect to a hub. First concave portions arranged in a circumferential direction are formed in an outer peripheral surface of the tubular member. Second concave portions arranged in the circumferential direction so as to respectively face the first concave portions are formed in an inner peripheral surface of the insertion hole. Each of the elastic bodies has a spherical or columnar shape, a first portion of each of the elastic bodies is disposed in each of the first concave portions, a second portion of each of the elastic bodies is disposed in each of the second concave portions, and the elastic bodies are rotatably held between the first concave portions and the second concave portions facing each other.