Wet Rotor Pump Assembly Coaxial Alignment via Stator Housing
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Solution Overview
Problem
Existing wet rotor pumps in house heating systems face challenges in achieving a compact design with precise coaxial alignment of the rotor axis, leading to inefficiencies due to manufacturing tolerances and increased fluid leakage.
Innovation Solution
The pump assembly employs a stator housing to angularly align the rotor can with respect to the pump housing, utilizing radial and annular reference surfaces for exact centric alignment, and a bearing retainer for radial centring, minimizing the gap between the impeller and neck ring, and incorporating a bayonet ring for secure and compact mounting of the stator housing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a large rotor can flange with circumferentially distributed trunnions is used for rotation prevention and axial alignment, then the alignment precision is improved, but the lateral space requirement increases
Solution Approach 1:
The alignment function is extracted from the rotor can flange and transferred to dedicated alignment elements (alignment ring and alignment protrusions) that are independently positioned. This separation allows the rotor can flange to be minimized for compactness while the alignment elements provide precise positioning without increasing lateral space requirements
Solution Approach 2:
An alignment ring is introduced as an intermediary element between the rotor can flange and the pump housing. This alignment ring with its protrusions provides the necessary rotation prevention and axial alignment, enabling the rotor can flange to be smaller while maintaining alignment precision
2Loss of energy
If manufacturing tolerances between independently manufactured rotor can and bearing retainer are reduced, then the gap between impeller and neck ring is minimized, but the alignment precision is improved
Solution Approach 1:
Alignment protrusions and corresponding recesses are pre-formed on the rotor can and alignment ring during manufacturing. These preliminary alignment features ensure that when components are assembled, the rotor axis is automatically centred with respect to the neck ring, minimizing the gap and reducing fluid leakage without requiring tight manufacturing tolerances on the assembled components
Solution Approach 2:
The reliance on tight mechanical tolerances between independently manufactured parts is replaced by a mechanical alignment system using protrusions and recesses. This substitution allows standard manufacturing tolerances to be used while still achieving precise centring of the rotor axis, thereby minimizing the gap between impeller and neck ring to reduce fluid leakage
3Volume of moving object
If the stator housing is used to angularly align the rotor can with respect to the pump housing, then the compactness is improved, but the device complexity increases
Solution Approach 1:
The stator housing is given multiple functions: it accommodates the stator, provides structural support, and serves as the alignment reference for the rotor can through its annular reference surface. By making the stator housing multi-functional, the patent achieves compactness without significantly increasing device complexity, as the same component performs multiple roles
Data Source
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AI summary
The present disclosure is directed to a pump assembly (1) comprising - a rotor axle (45) extending along a rotor axis (R), - an impeller (12) fixed to the rotor axle (45), - a pump housing (11) accommodating the impeller (12), wherein the pump housing (11) defines a first radial inner reference surface (71) and a first annular reference surface (109), - a drive motor comprising a stator (17) and a rotor (51), wherein the rotor (51) is fixed to the rotor axle (45) for driving the impeller (12), - a rotor can (57) accommodating the rotor (51), wherein the rotor can (57) comprises a rotor can flange (63), and - a stator housing (13) accommodating the stator (17), characterised in that the stator housing (13) defines a second annular reference surface (111) facing towards the impeller (12), wherein the second annular reference surface (111) is biased against the first annular reference surface (109) of the pump housing (11), and the stator (17) defines a second radial inner reference surface (115) essentially perpendicular to the second annular reference surface (111), and the rotor can (57) comprises a radial outer alignment surface (117) being aligned essentially perpendicular to the first annular reference surface (109) of the pump housing (11) by radially abutting against the second radial inner reference surface (115) of the stator (17).