Molten Metal Pump Coupling Assembly Segmentation
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Solution Overview
Problem
Existing coupling assemblies for molten metal pumps are prone to premature wear and fracture due to shear stress, are difficult to clean, and require excessive handling or machining, lacking superior strength and ease of connection/disconnection.
Innovation Solution
A coupling assembly with a female coupling member featuring co-axial shaft receiving openings, a pin member for precise axial positioning, and a removable driver member with an elongated configuration to enhance strength and ease of cleaning, allowing for secure and efficient connection between the drive shaft and impeller shaft.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a modified square coupling arrangement is used to transmit torsional forces, then the coupling can provide structural connection, but the internal corner portions are placed in shear causing fracture and premature wear
Solution Approach 1:
The coupling body is segmented into multiple web portions (first web, second web, third web, fourth web) that radiate from a central region to the internal corners. This segmentation distributes the torsional loads across multiple load paths, preventing concentration of shear stresses at any single corner portion and eliminating the fracture mechanism present in traditional modified square couplings.
Solution Approach 2:
The coupling design transitions from a two-dimensional modified square profile to a three-dimensional structure with multiple webs extending in different directions. This dimensional change creates redundant load paths and distributes stresses throughout the coupling body, eliminating the shear stress concentration that causes failure in planar modified square designs.
2Strength
If a traditional coupling design is used, then the connection is secure, but the coupling is difficult and time consuming to clean
Solution Approach 1:
The coupling body features substantially rounded internal corners and curved surfaces throughout its structure, replacing the sharp internal corners of traditional modified square designs. This curvature eliminates crevices where molten metal can accumulate, making the coupling easy to clean while maintaining structural integrity through the distributed web design.
Solution Approach 2:
The coupling body is designed with a smooth, rounded surface profile that reflects light uniformly, making it visually identifiable as a cleanable surface. The absence of shadowed internal corners creates a uniform appearance that indicates ease of cleaning, while the rounded geometry actually enables the cleaning function.
3Strength
If the impeller shaft is screwed into an internally threaded portion of the female coupling member, then the connection is secure, but the process is difficult and time consuming
Solution Approach 1:
The internal threading is extracted from the coupling body and replaced with an external threaded portion on the impeller shaft that engages with a corresponding external thread on the coupling. This extraction of the threading feature from one component and its placement on another simplifies the assembly process and reduces cleaning requirements while maintaining connection strength.
Solution Approach 2:
The coupling design uses a standardized external threaded interface that can be replicated and manufactured with high precision. This copied threading design allows for consistent, rapid assembly while maintaining secure connections, replacing the more complex internal threading approach.
4Device complexity
If conventional shaft connections or modified square design are used, then the structure is simple, but the strength is insufficient
Solution Approach 1:
Multiple functional features are merged into a single coupling body design: the web structure provides both structural strength and load distribution, the rounded corners provide both aesthetic simplicity and cleanability, and the threaded portion provides both connection functionality and manufacturing simplicity. This merging creates a multi-functional component that achieves superior strength without proportionally increasing complexity.
Solution Approach 2:
The coupling body serves multiple functions simultaneously: it transmits torsional forces through its web structure, provides a cleanable surface through its rounded geometry, enables secure shaft connection through its threaded interface, and maintains structural integrity under load. This multi-functionality achieves superior performance without requiring multiple separate components.
Data Source
AI summary
A coupling assembly for connection between a drive shaft and an impeller in a molten metal pump. The coupling assembly includes an upper portion to receive an end of the motor drive shaft and a lower portion to receive an end of the impeller shaft. The impeller shaft is pinned to the lower portion with a pin member which extends through first and second apertures in the lower portion of the coupling body. The pin member includes a handle portion, a driver member, and a stop. The driver member has an elongated configuration sized and shaped to pass through the first aperture of the coupling member. In application, once the impeller shaft is positioned in the coupling body, the pin member is passed through the apertures such that the driver member passes through the second aperture until the stop is in abutting relationship with the coupling member outer surface. Once the pin member and therefore driver member is inserted, the driver member is a contact point between the interior of the coupling member and impeller shaft.