Eccentric Piston Pump Shaft Flexing for Leak-Free Sealing
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Solution Overview
Problem
Positive displacement pumps with eccentric pistons experience leaks under load due to pressure-induced flexing of the drive shaft, leading to efficiency issues.
Innovation Solution
The use of elastic pressers with a thinned, flexible portion of the drive shaft and optionally radial springs with an angular offset ensures the piston remains pressed against the cylinder, maintaining fluid containment by aligning the return force with the piston-cylinder contact points, even under load.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the drive shaft is made rigid to maintain structural stability, then the pump structure is simple and strong, but the piston detaches from the cylinder under load causing leaks
Solution Approach 1:
The drive shaft transitions from a rigid structure to a flexible structure by reducing the cross-sectional area of a specific portion (first portion) while maintaining adequate strength in other portions. This parameter change allows the shaft to deform elastically under load, maintaining piston contact with the cylinder and preventing leaks.
Solution Approach 2:
The drive shaft is designed with non-uniform cross-sectional areas along its length. The first portion has a reduced cross-sectional area to provide flexibility, while other portions maintain larger cross-sectional areas for strength. This local quality differentiation resolves the contradiction between overall structural strength and local flexibility needs.
2Reliability
If the drive shaft is made flexible to maintain piston contact under load, then sealing is improved, but the shaft requires complex structural design with varying cross-sections
Solution Approach 1:
Instead of making the entire drive shaft complex and flexible, only a specific first portion is designed with reduced cross-sectional area to provide the necessary flexibility. The rest of the shaft maintains a simpler, more robust structure, thereby limiting the increase in device complexity to only where needed.
3Reliability
If the spring force is increased to maintain piston contact, then sealing improves, but the spring may interfere with piston movement or cause excessive wear
Solution Approach 1:
The drive shaft is designed to dynamically adapt its flexibility under load through elastic deformation of the first portion. This dynamic response replaces the need for high static spring forces, allowing the system to maintain sealing reliability while avoiding the harmful effects of excessive spring pressure such as interference with piston movement and increased wear.
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 configuration reduces leaks and maintains pump efficiency by ensuring the piston remains securely pressed against the cylinder, enhancing the pump's operational reliability and performance under load conditions.
Implementation Method 1
the elastic pressers includes at least one radial spring mounted at the end of the piston
Implementation Method 2
the cross-sectional area of the first portion is less than the cross-sectional areas of the adjacent portions so as to be able to deform elastically during the rotation of the drive shaft
Data Source
AI summary
Some embodiments are directed to a positive displacement pump having an eccentric piston, comprising a tube having a first end and a second end that is terminated by a cylinder secured to a delivery zone, the tube including an intake opening and a delivery opening, a drive shaft extending between the transmission zone and the tube, a piston arranged in the delivery zone and mounted in a sliding manner at the end of the shaft, being pressed against the cylinder by an elastic presser so as to prevent fluid displacement between the tube and the delivery zone when the pump is dry, and the elastic presser is provided to press the piston against the cylinder when the pump is running under load.