Marine Propeller Wedge Retention for Composite Blade Weight Reduction
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Solution Overview
Problem
Existing marine propulsion systems face challenges in reducing the stress on the drive system due to the weight of large propeller assemblies, particularly when using composite materials, as traditional joining methods are not applicable for composite propeller blades.
Innovation Solution
A blade retention system featuring a hub with wedge retaining members that create a dovetail slot to securely engage propeller blades with an interference fit, allowing for the use of lightweight composite blades and simplifying the assembly process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If traditional joining methods are used for propeller blades, then the structural integrity is maintained, but the weight reduction benefit of composite materials cannot be achieved
Solution Approach 1:
The retaining system is divided into multiple wedge-shaped retaining members distributed around the hub, each independently securing a portion of the propeller blade. This segmentation allows the blade to be retained through distributed frictional contact rather than requiring traditional mechanical fasteners that would compromise the composite structure.
Solution Approach 2:
The patent replaces traditional mechanical joining methods (such as bolts, rivets, or adhesives) with a friction-based retaining system. The wedge retaining members utilize radial friction forces generated by centrifugal loading to secure the composite propeller blade, eliminating the need for mechanical fasteners that would damage the composite material.
2Weight of moving object
If propeller blades are made from composite materials, then weight is reduced, but traditional joining methods become inapplicable
Solution Approach 1:
The wedge retaining members are pre-installed on the hub before propeller blade assembly. This preliminary action creates ready-made retention zones that guide and secure the composite blades during assembly, simplifying the manufacturing process compared to traditional methods that require complex fastening operations after blade installation.
Solution Approach 2:
The retaining system utilizes the operational conditions of the propeller (rotational speed and centrifugal forces) to generate the friction forces needed for blade retention. During normal operation, the centrifugal loading automatically increases the frictional engagement between the retaining members and the blade, making the system self-securing without requiring additional active retention mechanisms.
3Stress or pressure
If the propeller assembly weight is reduced, then stress on the drive system decreases, but the blade retention mechanism becomes more critical
Solution Approach 1:
The wedge retaining members are made from composite materials that provide both lightweight construction and high strength-to-weight ratio. This allows the retention mechanism itself to be lightweight while maintaining sufficient connection strength, preserving the overall weight reduction benefits while ensuring adequate blade-to-hub connection strength.
Solution Approach 2:
The wedge retaining members feature curved or tapered surfaces that conform to the rotational loading conditions. The curved geometry distributes the retention forces more evenly around the blade root, enhancing the effective connection strength while maintaining a lightweight structure that does not compromise the drive system stress reduction.
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
This solution reduces the weight of the propeller assembly, enables the use of composite materials, and simplifies the assembly of marine propeller systems by restricting radial movement of propeller blades, thereby alleviating stress on the drive system.
Implementation Method 1
The plurality of wedge retaining members are configured to restrict radial movement of the root portion within the dovetail slot
Implementation Method 2
The plurality of wedge retaining members are spaced circumferentially about the outer radial surface such that a dovetail slot is defined between adjacent wedge retaining members
Data Source
AI summary
A propeller assembly that includes a hub having an outer radial surface and a plurality of wedge retaining members removably coupled to the hub. The plurality of wedge retaining members are spaced circumferentially about the outer radial surface such that a dovetail slot is defined between adjacent wedge retaining members. The assembly also includes at least one propeller blade including a root portion having a dovetail profile. The root portion is coupled to the hub and positioned within the dovetail slot. The plurality of wedge retaining members are configured to restrict radial movement of the root portion within the dovetail slot.