Tapered Thread Impeller Attachment for Self-Alignment
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Solution Overview
Problem
Current pump designs face challenges with aligning impeller threads and shaft threads during maintenance, as standard thread forms tend to cross-thread if slightly misaligned and require numerous turns to seat, complicating field maintenance with heavy equipment alignment issues.
Innovation Solution
A tapered thread configuration between the impeller and shaft allows for direct torque transmission and self-alignment, reducing the need for precise alignment and minimizing the number of turns required for attachment and detachment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If standard thread forms are used to attach impeller to shaft, then the connection is simple and inexpensive, but alignment is difficult to maintain in field conditions and cross-threading occurs if slightly misaligned
Solution Approach 1:
The patent changes the geometric parameters of the thread form from standard cylindrical threads to tapered threads with specific angle (typically 15-30 degrees). This parameter change allows the threads to self-align during assembly, eliminating the need for precise alignment while maintaining simplicity and low cost.
Solution Approach 2:
The tapered thread form introduces asymmetry in the thread geometry, with the diameter varying along the length of the thread. This asymmetric design creates a natural guiding effect that directs the impeller onto the shaft correctly, preventing cross-threading while keeping the attachment method simple.
2Device complexity
If standard thread forms are used, then the attachment method is simple, but a large number of turns are required to seat the shaft threads in the impeller
Solution Approach 1:
The tapered thread geometry changes the engagement characteristics, allowing the threads to seat more quickly. The converging shape of the tapered threads creates increasing contact area and friction as engagement progresses, enabling secure attachment in fewer turns compared to standard threads.
Solution Approach 2:
The tapered thread form introduces a curved, converging geometry that guides the engagement process. This curvature allows the threads to naturally align and engage more efficiently, reducing the number of turns needed to achieve full seating while maintaining mechanical simplicity.
3Ease of operation
If tapered threads are used for attachment, then alignment is improved and cross-threading is reduced, but the thread configuration becomes more complex
Solution Approach 1:
While the thread geometry becomes more complex with the taper, the parameters are optimized to balance alignment performance with manufacturality. The taper angle is kept within practical ranges (15-30 degrees) that can be easily machined, and the thread profile remains relatively simple, avoiding excessive complexity while achieving self-alignment.
Solution Approach 2:
The tapered thread design serves multiple functions simultaneously: it provides self-alignment, prevents cross-threading, and maintains adequate torque transmission. This multi-functionality justifies the moderate increase in geometric complexity by eliminating the need for separate alignment mechanisms or procedures.
4Loss of time
If tapered threads are used, then maintenance time is reduced and quick release is enabled, but manufacturing precision requirements increase
Solution Approach 1:
The taper angle and thread pitch are optimized to provide a balance between quick release capability and manufacturing tolerances. The gradual convergence of the tapered threads allows for controlled engagement and disengagement, reducing maintenance time while accommodating reasonable manufacturing variations.
Solution Approach 2:
The tapered thread design concentrates the alignment and engagement functions in the local geometry of the threads themselves, rather than requiring precise alignment of entire components. This local quality approach allows for faster maintenance while tolerating greater variations in overall component dimensions.
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 maintenance time and equipment needs, enhances efficiency by allowing quick release of the tapered threads, and decreases vibration, leading to longer equipment life and reduced eccentricity.
Implementation Method 1
The tapered threads are configured to couple directly to the impeller threads of the tapered bore of the impeller, to transmit torque directly through the tapered threads
Data Source
AI summary
A pump is provided having an impeller in combination with a power transmission shaft. The impeller has a tapered bore with impeller threads. The power transmission shaft has a shaft end with tapered threads configured to couple directly to the impeller threads of the tapered bore of the impeller, to transmit torque directly through the tapered threads, and to provide self axial or radial alignment even if the coupling of the tapered threads and the impeller threads of the tapered bore start out of alignment. The tapered thread configuration substantially reduces investment in lifting equipment and time by maintenance personnel because it eliminates the need for maintenance personnel to precisely align the impeller threads and the tapered threads before attaching or removing the impeller and the tapered threads release much more quickly from the impeller than a standard thread configuration, reducing the number of turns the power transmission shaft must be rotated by hand to free it from the impeller.