Safety-Coupled Screw Propeller Hub for Obstacle Damage Protection
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Solution Overview
Problem
The existing screw propeller with safety coupling designs lack detailed construction elements, leading to suboptimal reliability, durability, and manufacturability, particularly in reducing the risk of damage to propeller blades and their mechanisms upon encountering obstacles.
Innovation Solution
The design enhances the screw propeller with a safety coupling system featuring a driving and driven coupling with a torque damper, a safety dowel pin, and trapezoidal splines, allowing for improved torque transmission and alignment through a spacer bushing, which increases reliability and manufacturability by preventing wear and damage to the propeller shaft and splines.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the driven coupling is rigidly fixed to the propeller shaft, then torque transmission is direct and efficient, but wear and damage to the propeller shaft and splines occurs upon encountering obstacles
Solution Approach 1:
The coupling is divided into a driving coupling and a driven coupling that can rotate relative to each other. The driven coupling is disposed for rotation on a spacer bushing, creating a segmented structure that allows independent movement of each coupling component, thereby protecting the propeller shaft from direct wear while maintaining torque transmission capability.
Solution Approach 2:
A spacer bushing is introduced as an intermediary element between the driven coupling and the propeller shaft. This mediator allows the driven coupling to rotate freely on the shaft without direct contact, eliminating wear on the shaft and splines while still enabling torque transmission through the coupling mechanism.
2Duration of action of stationary object
If the driven coupling can rotate and move relative to the propeller shaft, then wear and damage is prevented, but torque transmission efficiency may be reduced
Solution Approach 1:
The driven coupling is designed to be dynamically movable on the spacer bushing, allowing it to rotate and move axially relative to the propeller shaft. This dynamic capability enables the coupling to absorb shocks and misalignments from obstacles while maintaining continuous torque transmission, thus extending service life without significantly compromising power transfer.
Solution Approach 2:
The friction characteristics between the driven coupling and spacer bushing are optimized to maintain adequate torque transmission. By controlling the friction coefficient and contact pressure parameters, the system allows free rotation for protection while preventing excessive slippage that would reduce power transmission efficiency.
3Reliability
If detailed construction elements are added to improve reliability, then protection against damage increases, but manufacturability decreases
Solution Approach 1:
The safety coupling is segmented into modular components (driving coupling, driven coupling, spacer bushing, dowel pin) that can be manufactured independently using standard machining processes. This segmentation allows each component to be produced with conventional manufacturing methods while assembling to form a reliable protective mechanism.
Solution Approach 2:
The spacer bushing serves as a simple intermediary component that can be manufactured as a standard bushing element. Its straightforward geometry and function as a rotational bearing make it easy to manufacture while providing the critical function of protecting the propeller shaft from wear through the enabled relative motion.
Data Source
AI summary
The present device relates to boatbuilding, and more particularly to screw propellers with safety couplings, intended for use in outboard motors and/or marine screw propellers. A screw propeller with a safety coupling comprises a screw propeller body-cum-hub, a drive coupling, a driven coupling, and a dowel pin. The driven coupling is disposed for rotation on a spacer bushing, said spacer bushing being a tail bushing of the driving coupling. The driven coupling is partially or completely disposed in an opening in the screw propeller body-cum-hub and transmits torque to the screw propeller body-cum-hub by means of a longitudinal dowel pin and/or longitudinal grooves and a spline coupling. A common opening for the dowel pin in the driving and/or the driven coupling is configured as a through opening, and/or the blind end of the opening for the dowel pin is connected by a transverse opening to the outside surface.