Variable Pump Helical Spring Geometry to Prevent Buckling
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Solution Overview
Problem
Conventional rotary pumps with adjustable delivery volumes face issues due to coil spring buckling under axial pressure, leading to instability and potential fatigue fractures, which can result in pump malfunction or damage, especially when storage conditions exacerbate non-parallel contact surfaces and pivoting actuating structures.
Innovation Solution
A pump design featuring a helical spring with a progressively changing cross-sectional area, forming a concave envelope curve that stabilizes the spring by allowing turns to immerse or overlap, reducing the risk of buckling and extending spring travel without compromising installation space.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a conventional cylindrical compression spring with constant coil diameter is used, then the spring can be installed in limited pump space, but the spring is prone to buckling under axial compressive loads due to high L0/D ratio
Solution Approach 1:
The spring wire diameter varies along the length of the spring, with larger diameter at the ends and smaller diameter in the middle section. This local variation in geometry provides enhanced buckling resistance at the ends where it is most needed, while maintaining compact overall dimensions for pump installation.
Solution Approach 2:
The spring features a curved envelope with concave profile instead of a straight cylindrical shape. The curved geometry with varying coil diameter along the length improves structural stability and buckling resistance while maintaining compact installation space within the pump housing.
2Reliability
If the spring wire diameter is increased to prevent buckling, then buckling resistance improves, but the spring becomes more expensive and may prevent optimal throttle response adjustment
Solution Approach 1:
Instead of uniformly increasing the wire diameter throughout the spring, the invention applies larger diameter only at the end sections where buckling resistance is critical, while maintaining smaller diameter in the middle section. This localized approach provides the necessary stability while minimizing material usage and manufacturing cost.
3Reliability
If mandrels or sleeves are used to stabilize the spring, then buckling is prevented, but additional costs are incurred and the solution may not be compatible with all pump designs
Solution Approach 1:
The spring's own geometry is modified to provide buckling resistance through varying wire diameter along its length, eliminating the need for external mandrels or sleeves. This self-stabilizing design integrates the stabilization function directly into the spring structure, reducing component count and complexity.
4Reliability
If the actuating travel is limited to be smaller than the critical spring travel, then buckling is avoided, but the pump's throttle response adjustment is compromised
Solution Approach 1:
The non-uniform wire diameter distribution with larger ends and smaller middle section increases the critical buckling travel distance, allowing the actuating structure to achieve full required travel range without risking buckling, thus maintaining optimal throttle response adjustment capability.
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 coil spring buckling, ensuring stable pump operation and extended spring travel, thereby reducing the likelihood of material fatigue and pump damage, while maintaining cost-effectiveness.
Implementation Method 1
a helical spring (10) for applying a spring force (Fs) to the adjusting structure (7) in an adjusting direction
Data Source
Figure 1~2
Figure 3~10
AI summary
Pump with variable displacement, comprising: - a pump housing (1) with a pumping chamber having a pumping chamber inlet (2) for a fluid and a pumping chamber outlet (3) for the fluid, - a pumping element (4) rotatable in the pumping chamber for pumping the fluid, - an adjustment device (5) with an actuating structure (7) mounted to move back and forth in the pump housing (1) for adjusting the pump's displacement, and a helical spring (10; 20; 30; 40; 50; 60) for applying a spring force to the actuating structure (7) in an actuating direction, wherein the coils of the helical spring (10; 20; 30; 40; 50; 60) are enclosed by an envelope on the outside of the helical spring (10; 20; 30; 40; 50; 60), wherein the cross-sectional area of the envelope measured transversely to the longitudinal direction of the spring is changes progressively in the longitudinal direction of the spring.