Variable-Diameter Helical Spring for Pump Buckling Resistance
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Solution Overview
Problem
Conventional rotary pumps with helical springs are prone to buckling under axial compressive loads, leading to instability and potential failure, which can result in premature throttling or complete malfunction, especially due to non-parallel bearing surfaces and limited installation space.
Innovation Solution
A pump design featuring a helical spring with a variable cross-sectional area envelope that increases or decreases monotonically along its length, stabilizing itself by allowing windings to merge or separate, reducing the risk of buckling and extending spring travel without additional stabilization components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a conventional cylindrical helical spring with constant winding diameter is used, then the spring can be manufactured simply, but the spring is susceptible to buckling under axial compressive load
Solution Approach 1:
The patent applies local quality by varying the winding diameter along the length of the spring. The envelope of the spring is formed such that the cross-sectional area changes progressively in the longitudinal direction, creating different local properties - smaller diameter at ends and larger diameter in the middle section. This local variation provides buckling resistance where needed while maintaining manufacturability.
Solution Approach 2:
The patent changes the geometric parameter of the spring by varying the winding diameter along its length. The envelope is designed with a specific profile (e.g., barrel-shaped, bell-shaped, or hourglass-shaped) that changes the cross-sectional area progressively. This parameter change transforms the spring from a uniform cylinder to a variable-diameter structure that resists buckling.
2Adaptability or versatility
If the bearing surfaces are made non-parallel to accommodate the pivoting setting structure, then the pump can be regulated, but the helical spring is deflected at an angle promoting yielding and buckling
Solution Approach 1:
The variable cross-sectional area envelope provides local quality enhancement at critical locations. The enlarged middle section of the spring acts as a stabilization zone that resists the additional radial forces generated by non-parallel bearing surfaces, while the end sections maintain proper mounting geometry.
Solution Approach 2:
The patent addresses the two-dimensional problem of bearing surface alignment by introducing a third dimension - the longitudinal variation of the winding diameter. This dimensional change creates a three-dimensional envelope that can accommodate angular deflections while maintaining spring stability.
3Reliability
If the setting travel is increased to match the critical spring travel, then the spring can be optimized, but the installation space requirements increase
Solution Approach 1:
By changing the winding diameter parameter along the length of the spring, the patent achieves better travel characteristics without proportionally increasing the overall volume. The variable diameter allows the spring to extend further in the axial direction while the cross-sectional area varies to maintain stability, effectively decoupling travel length from volume.
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 design effectively minimizes the risk of helical spring damage and maintains pump functionality by stabilizing the spring and extending its travel, reducing the likelihood of buckling and fatigue, while allowing for optimal throttling characteristics without increasing costs.
Implementation Method 1
a helical spring (10) for applying a spring force, which acts in a setting direction, to the setting structure (7)
Data Source
AI summary
A pump having an adjustable delivery volume, including: a pump housing featuring a delivery chamber which includes a delivery chamber inlet for a fluid and a delivery chamber outlet for the fluid; a delivery member, which can be rotated within the delivery chamber, for delivering the fluid; an adjusting device featuring a setting structure, which is mounted such that it can move back and forth within the pump housing in order to adjust the delivery volume of the pump, and a helical spring for applying a spring force, which acts in a setting direction, to the setting structure, wherein the windings of the helical spring are enclosed by an envelope lying on the outside of the helical spring wherein the cross-sectional area of the envelope as measured transversely with respect to the longitudinal direction of the spring changes progressively in the longitudinal direction of the spring.