Folding Propeller Mass Offset and Composite Design
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Solution Overview
Problem
Conventional folding propellers for watercraft face challenges in propulsion and maneuverability, particularly during reversing and stopping, due to balancing centrifugal and thrust forces, which result in significant losses and increased weight, noise, and maintenance costs from heavy metal materials.
Innovation Solution
A folding propeller design with a hub-driven propeller blade that has a center of mass offset from the maximum opening plane, utilizing a buoyancy body like a winglet to generate an opening moment, and a modular construction with different material densities for optimized centrifugal and buoyancy forces, reducing weight and corrosion while improving propulsion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If the mass of the propeller blades is increased to increase centrifugal force, then the propeller blades can open further from medium opening position during reversing, but the entire folding propeller becomes very heavy, generating unwanted vibrations, noise, and strong shocks
Solution Approach 1:
The patent changes the parameter of mass distribution by concentrating mass at specific locations (propeller blade tip section or stub section) rather than uniformly distributing it. This creates a distally arranged center of mass that generates sufficient centrifugal force while minimizing overall weight and associated vibrations and noise.
Solution Approach 2:
The patent employs composite construction with different material densities in different sections of the propeller blade. High-density materials are used selectively in the tip section or stub section where mass concentration is needed, while lighter materials are used in other sections, optimizing the balance between centrifugal force generation and weight reduction.
2Strength
If high-density metal materials are used for propeller blades, then sufficient strength and centrifugal force are achieved, but the folding propeller becomes very heavy, increasing corrosion and maintenance costs
Solution Approach 1:
The patent uses composite materials with different densities and corrosion properties in different sections of the propeller blade. This allows the use of corrosion-resistant materials in areas subject to water exposure, reducing maintenance costs while maintaining sufficient strength through strategic material placement.
Solution Approach 2:
The patent applies different material properties to different locations in the propeller blade structure. High-density materials are used locally in the tip section or stub section where mass concentration is needed for centrifugal force, while corrosion-resistant materials are used in areas prone to water exposure, optimizing both performance and durability.
3Force
If the propeller blades are made heavy to increase centrifugal force, then opening force during reversing is improved, but the propulsion system experiences unwanted vibrations and noise
Solution Approach 1:
The patent optimizes the parameter of mass distribution by concentrating mass distally in the propeller blade tip section or stub section. This creates a distally arranged center of mass that generates sufficient opening force during reversing while minimizing the overall mass that would cause vibrations and noise.
Solution Approach 2:
The patent employs composite materials with optimized density distributions to achieve the necessary centrifugal force for opening during reversing while minimizing the mass that would generate unwanted vibrations and noise in the propulsion system.
4Strength
If conventional folding propellers use standard metal materials, then sufficient strength is achieved, but manufacturing becomes complex and overall boat weight increases
Solution Approach 1:
The patent uses composite materials that can be manufactured using standardized processes, simplifying production while achieving the required strength properties. The modular design with standardized connection elements between blade sections also simplifies manufacturing and assembly.
Solution Approach 2:
The patent divides the propeller blade into multiple sections (tip section, stub section, root section) that can be manufactured separately and then connected using standardized elements. This segmentation simplifies manufacturing by allowing parallel production and reduces overall complexity compared to monolithic construction.
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
Enhances propulsion efficiency and maneuverability by optimizing centrifugal and buoyancy forces, reducing weight and corrosion, and simplifying maintenance through modular design and material distribution.
Implementation Method 1
an opening force acts on the propeller blade, which results from rotation of the folding propeller and which is directed essentially radially outwards with respect to the rotational axis
Implementation Method 2
utilizing a buoyancy body like a winglet to generate an opening moment
Data Source
Figure 1
Figure 2a
Figure 2b
AI summary
The present invention relates to a folding propeller (10) for a watercraft, comprising a hub (12) which is drivable about a rotational axis (D) via a drive shaft, and a propeller blade (14) which is arranged on the hub (12) so as to be pivotable about a pivot axis (S) between a maximum closed position (P1) and a maximum open position (P2), wherein the pivot axis (S) together with a normal (ND) of the rotational axis (D) intersecting the pivot axis (S) defines a maximum opening plane (EMax), wherein in the driven state and a pivoted position of the propeller blade (14) in the region of the maximum open position (P2), at least one opening force acts on the propeller blade (14), which results from rotation of the folding propeller (10) and is directed substantially radially outwards with respect to the rotational axis (D),wherein an effective force application point (EAP) of the opening force is spaced from the maximum opening plane (EMax) and arranged substantially in the closing direction (SR) of the propeller blade (14). Furthermore, the invention relates to a folding propeller (10) comprising a propeller blade (14) having a reversing element (143) designed such that, during reverse propulsion, a reverse thrust force (FReversal) acts on the reversing element (143), which is directed substantially perpendicular to the propeller blade longitudinal axis (LP) in the opening direction (ÖR) of the propeller blade (14).