Hollow-Shaft Pump Coupling for High-Speed Alignment
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Solution Overview
Problem
Existing pump assemblies face challenges in achieving high rotational speeds while maintaining a compact design due to intolerable dynamic imbalances and eccentricities caused by tight manufacturing tolerances in motor and pump shaft connections, and they lack flexibility in accommodating various pump drive shaft lengths and diameters.
Innovation Solution
A modular pump assembly with a hollow motor drive shaft and a releasable drive shaft coupling that allows for axial positioning and easy disassembly without dismounting the pump housing, utilizing a frictional connection and optional hydraulic pressure chambers for enhanced alignment and torque transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If tight manufacturing tolerances are used for shaft connections, then angular alignment between motor shaft and pump shaft is improved, but manufacturing cost and quality management rejections increase
Solution Approach 1:
A coupling device is introduced as an intermediary element between the motor drive shaft and pump drive shaft. This coupling includes alignment features such as tapered surfaces and positioning elements that automatically align the shafts angularly without requiring tight manufacturing tolerances on the shafts themselves, thereby reducing manufacturing cost and rejections while maintaining precise angular alignment.
Solution Approach 2:
The invention changes the approach from controlling angular alignment through shaft dimensional parameters to controlling it through coupling device geometry parameters. The coupling device incorporates specific geometric features (tapered surfaces, positioning ribs, etc.) that define the angular relationship, allowing standard-tolerance shafts to achieve precise alignment through the coupling's designed parameters.
2Ease of operation
If releasable connections between motor drive shaft and pump drive shaft are implemented, then ease of assembly and disassembly is improved, but dynamic imbalances and eccentricities at high rotational speeds increase
Solution Approach 1:
The coupling device serves as a precision intermediary that maintains reliable torque transfer at high speeds while enabling easy release. It incorporates friction surfaces and mechanical engagement features that provide secure connection during operation, minimizing dynamic imbalances, while allowing tool-based release for assembly and disassembly without dismounting the pump drive shaft from the pump housing.
Solution Approach 2:
The invention replaces traditional mechanical connection methods (keys, splines, or press-fits) with a friction-based mechanical press fit system in the coupling device. This system uses radially expandable elements that create uniform friction contact between shafts, providing reliable torque transfer at high rotational speeds while maintaining the ability to release with appropriate tools.
3Volume of moving object
If compact pump assembly design is pursued, then volume is reduced, but maximum operating speed is limited due to dynamic imbalances
Solution Approach 1:
The coupling device is designed to fit within the hollow motor drive shaft, creating a nested configuration. The radially expandable elements are contained within the motor drive shaft's inner diameter when retracted, and expand outward to contact the pump drive shaft. This nesting approach minimizes the radial and axial dimensions of the coupling, maintaining compact pump assembly design while enabling high-speed operation through precise alignment and balanced torque transfer.
4Adaptability or versatility
If drive shaft coupling is made freely positionable in axial direction, then adaptability to various pump drive shaft lengths is improved, but positioning precision may be compromised
Solution Approach 1:
The coupling device incorporates axial adjustability through its design, allowing it to be positioned at different axial locations along the pump drive shaft. The friction-based mechanical press fit and expandable elements enable the coupling to maintain secure engagement and precise positioning regardless of axial location, providing adaptability to various pump drive shaft lengths while preserving positioning precision through its self-centering and friction-locking features.
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 solution reduces dynamic imbalances, allows for high rotational speeds up to 6000 rpm, and supports a variety of shaft lengths, while maintaining a compact design and providing resilience against axial and radial forces.
Implementation Method 1
The drive shaft coupling is arranged at least partly within the hollow motor drive shaft for transferring torque from the motor drive shaft to the pump drive shaft by frictional connection with a radial inner surface of the hollow motor drive shaft and/or a radial outer surface of the pump drive shaft
Data Source
Figure 1
Figure 2
Figure 3a~3b
AI summary
The present disclosure refers to a pump assembly (1) comprising: - an electric drive motor (5) comprising at least a motor drive shaft (35) and a rotor (41), wherein the motor drive shaft (35) extends along a rotor axis (R) and the rotor (41) is mechanically coupled to the motor drive shaft (35); and - a pump housing (3) enclosing an impeller (13) that is mechanically coupled to a pump drive shaft (33), wherein the pump drive shaft (33) extends along the rotor axis (R), wherein the motor drive shaft (35) is releasably coupled to the pump drive shaft (33) by a drive shaft coupling (37) for transferring torque from the motor drive shaft (35) to the pump drive shaft (33), characterised by the motor drive shaft (35) being hollow from a first axial motor drive shaft end (81) to a second axial motor drive shaft end (83), wherein the pump drive shaft (33) protrudes into the hollow motor drive shaft (35) at the first axial motor drive shaft end (81), wherein the drive shaft coupling (37) is arranged at least partly within the hollow motor drive shaft (35) for transferring torque from the motor drive shaft (35) to the pump drive shaft (33) by frictional connection with a radial inner surface (89) of the hollow motor drive shaft (35) and/or a radial outer surface (93) of the pump drive shaft (33), wherein the drive shaft coupling (37) is accessible by an elongate tool through the second axial hollow motor drive shaft drive end (83) for selectively tightening and releasing the drive shaft coupling (37).