Rolling Crown Axial Thrust Compensation in Geared Pumps
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Solution Overview
Problem
External geared positive-displacement pumps face issues with noise and efficiency due to periodic axial load oscillations and hydrodynamic film instability at high pressures and low speeds, leading to increased sliding friction and wear.
Innovation Solution
Incorporating a plurality of rolling bodies forming a crown in annular seats at the interface between the gearwheels and containment bodies, which support axial thrusts and maintain a thin hydrodynamic film for sealing, reducing sliding friction and wear.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If floating bushes are used to compensate axial clearance, then axial thrust balancing is improved, but periodic axial load oscillations increase noise and reduce efficiency
Solution Approach 1:
The floating bush is segmented into multiple independent rolling elements (balls or rollers) arranged in a crown, each capable of independently supporting axial loads. This segmentation converts the continuous sliding surface into discrete rolling contacts, eliminating periodic oscillations while maintaining axial thrust balancing capability
Solution Approach 2:
The sliding friction mechanism of traditional floating bushes is replaced with a rolling friction mechanism using balls or rollers. This substitution transforms the mechanical interaction from sliding contact to rolling contact, significantly reducing friction and eliminating periodic load variations that cause noise
2Reliability
If floating bushes are used for axial thrust balancing, then sealing is improved, but sliding friction increases at low speeds
Solution Approach 1:
The sliding friction mechanism is replaced with rolling friction using balls or rollers in the floating bush. This substitution dramatically reduces friction forces, enabling effective operation at low speeds (100-500 rpm) where hydrodynamic lubrication would be insufficient
Solution Approach 2:
The friction regime is changed from sliding to rolling by introducing rolling elements. This parameter change in the friction mechanism allows the pump to operate efficiently at low speeds while maintaining proper sealing through the rolling elements
3Object-generated harmful factors
If spur cylindrical gearwheels are used, then axial load oscillations are limited, but helical gearwheels generate substantial oscillations
Solution Approach 1:
The sliding axial contact between helical gear teeth and floating bush is replaced with rolling contact through balls or rollers. This substitution eliminates the periodic oscillations generated by helical gear meshing while preserving the advantages of helical gear smooth engagement and high productivity
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 enables reliable operation at high pressures (100-300 bar) and low speeds (100-500 r.p.m.) with reduced sliding friction and wear, ensuring effective sealing and improved efficiency.
Implementation Method 1
for each of the two gearwheels, a plurality of rolling bodies which are freely housed in a respective annular seat and which rest on relative rolling tracks when a distance greater than zero exists between the first face of the containment body and the surface of the gearwheel that faces it
Implementation Method 2
between the inner faces of the bearings and the facing faces of the two gearwheels a hydrodynamic film or meatus forms consisting of the liquid that is pumped
Data Source
AI summary
A geared positive-displacement machine (10), comprising a housing (11) provided with a suction port and with a discharge port, a pair of gearwheels (14, 15) that are housed and supported by respective shafts (16, 18) for the rotation in a space inside the housing (11) and in fluid communication with the suction port and the discharge port, wherein the gearwheels (14, 15) mesh with each other and have parallel or coinciding axes and a first wheel (14) thereof is driving and a second wheel (15) is driven, a pair of containment bodies (19, 20) for axially containing the wheels (14, 15), said containment bodies (19, 20) being associated with the housing (11) and each comprise a first face (19a, 20a) that faces the pair of gearwheels (14, 15) and a second face (19b, 20b) that is axially opposite with respect to the first face (19a, 20a), and, for each of the two wheels (14, 15), a plurality of rolling bodies (21) that form a crown and that are freely housed in an annular seat (22) that is coaxial to the respective shaft (16, 18) and that is defined at the interface between the first face (19a, 20a) of at least one of the two containment bodies (19, 20) and the surface (14a, 15a; 14b, 15b) of the wheels (14, 15) that in turn faces it, respectively in the first face (19a, 20a) of at least one of the two containment bodies or in the surface (14a, 15a; 14b, 15b) of the gearwheels facing the first face (19a, 20a), wherein the rolling bodies (21) rest on rolling tracks (23, 24) respectively integral with the wheels (14, 15) and with the at least one containment body (19, 20). Between the first face (19a, 20a) of the at least one containment body (19, 20) and the surface (14a, 15a; 14b, 15b) of the wheels (14, 15) facing the first face a distance (D) greater than zero exists.