Marine Propeller Bushing Breakable Portion
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Solution Overview
Problem
Existing propeller units in marine propulsion apparatuses face irregularities in shock absorbing performance, leading to excessive load on power transmission systems, which can compromise their protection and reliability.
Innovation Solution
A propeller unit design featuring a bushing with a hollow shaft member and an elastic damper, spline-coupled to the propeller shaft, includes a breakable portion acting as a safety fuse to protect the power transmission system by breaking under excessive load, thereby preventing damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a cushioning member is fitted between the sleeve member and inner hub to absorb shocks, then shock absorbing capability is improved, but irregularity in shock absorbing performance remains and excessive load may still be applied to the power transmission apparatus
Solution Approach 1:
The patent applies beforehand cushioning by incorporating a damper made of elastic material between the hollow shaft member and inner hub. This damper is pre-positioned to absorb shocks before they reach the power transmission apparatus. Additionally, a breakable portion is designed in advance as a safety mechanism that will fail under excessive load, preventing damage to critical components. This combination of pre-positioned cushioning and predetermined failure points directly addresses the contradiction by ensuring reliable shock absorption while guaranteeing protection capability.
2Stability of the object's composition
If the cushioning member is engaged with channels and protrusions to reduce irregularity, then shock absorption is improved, but the effect is not stabilized and protection remains insufficient
Solution Approach 1:
The patent applies segmentation by dividing the shock absorption function into multiple independent elements: the damper made of elastic material and the breakable portion. Rather than relying on a single cushioning member engaged with channels and protrusions, the invention segments the protection mechanism into a primary shock absorption element (damper) and a secondary safety element (breakable portion). This segmentation stabilizes the shock absorption effect and ensures reliable protection, as each segment independently contributes to the overall safety function.
3Device complexity
If no breakable portion is provided, then the structure is simpler, but excessive load cannot be safely managed and power transmission apparatus may be damaged
Solution Approach 1:
The patent applies the principle of disposable components by incorporating a breakable portion in the hollow shaft member. This breakable portion acts as a sacrificial element designed to fail under excessive load, protecting the more valuable and complex power transmission apparatus. The breakable portion is intentionally designed to be a weak point that can be replaced, while the main power transmission components are preserved. This approach manages excessive load safely with minimal added complexity, as the breakable portion is a simple structural feature rather than a complex mechanism.
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 design effectively absorbs and manages excessive loads, ensuring the reliability and protection of the power transmission system while maintaining low-speed sailing capabilities.
Implementation Method 1
a damper formed of an elastic member and arranged to cover an outer circumferential surface of the hollow shaft member
Data Source
AI summary
A propeller unit of a marine propulsion apparatus includes: an inner hub; an outer hub arranged coaxially with the inner hub, connected to the inner hub, and provided with a plurality of blades on its outer circumferential surface; and a bushing having a hollow shaft member provided with ribs on an outer circumferential surface and connected to the propeller shaft, and a damper formed of an elastic member and arranged to cover an outer circumferential surface of the hollow shaft member between the outer circumferential surface of the hollow shaft member and the inner circumferential surface of the inner hub, wherein the bushing is spline-coupled to the propeller shaft through spline teeth formed on an inner circumferential surface of a front half or rear half of a longitudinal direction of the hollow shaft member, and has a breakable portion provided in a part corresponding to the non-spline-toothed portion.