Eccentric Screw Pump Hollow-Shaft Mounting for Easier Stator Removal
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Solution Overview
Problem
Eccentric screw pumps face challenges during maintenance due to the difficulty in dismantling the stator housing with a blocked rotor, which requires relative movement between the stator and rotor, and the complexity of accessing and loosening screw connections, often resulting in prolonged downtime and risk of leaks.
Innovation Solution
The design includes a hollow shaft coupled to the drive motor via a gear, allowing for axial mobility of the stator housing and rotor by releasing the second shaft-hub connection through a cavity, and a truncated cone connection for easy detachment of the rotor from the drive shaft, along with a sleeve to encapsulate cardan joints and prevent fluid exposure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the rotor is blocked inside the stator housing, then the pump cannot operate, but the maintenance procedure becomes extremely difficult and time-consuming
Solution Approach 1:
The drive shaft is segmented into a hollow shaft and a solid inner shaft, allowing independent movement. The hollow shaft can move axially relative to the stator housing while the inner shaft remains connected to the rotor, enabling the blocked rotor-stator assembly to be pivoted out without requiring complete disassembly of the drive train
Solution Approach 2:
The hollow shaft acts as an intermediary element between the drive motor and the rotor. It transmits torque while allowing axial movement, serving as a mediator that decouples the rotor's radial movement from the drive shaft's position, thereby enabling maintenance access
2Stress or pressure
If the stator housing is made heavy-duty to handle high pressure, then the pump can operate under higher pressure, but the stator becomes difficult to remove for maintenance
Solution Approach 1:
The drive system is segmented to allow the rotor-stator assembly to be separated from the drive motor. The hollow shaft's axial mobility enables the rotor-stator unit to be pivoted out as a complete assembly, avoiding the need to break apart the heavy-duty stator housing itself
3Power
If the rotor is directly connected to the drive shaft, then torque transmission is efficient, but the rotor cannot perform the necessary wobbling motion
Solution Approach 1:
The connection between the drive shaft and rotor is made dynamic rather than rigid. The hollow shaft can move axially and the universal joints allow angular movement, enabling the rotor to perform its characteristic wobbling motion while still receiving torque from the drive motor
Solution Approach 2:
The hollow shaft adds an axial dimension of movement to the system. While the rotor moves radially and rotates, the hollow shaft's axial mobility provides an additional degree of freedom that accommodates the rotor's complex motion path
4Device complexity
If the cardan joints are exposed to the pumped fluid, then the structure is simpler, but the joints are subject to wear and contamination
Solution Approach 1:
The hollow shaft serves as a protective intermediary that shields the cardan joints from direct exposure to pumped fluid. The joints are positioned inside the hollow shaft's cavity, which is filled with lubricant, creating a protective barrier while maintaining functional connectivity
Data Source
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AI summary
An eccentric screw pump comprising a rotor (70) extending along a rotor longitudinal axis (1) from a drive end to a free end, a stator housing (90) with an interior extending along the longitudinal axis (1) from a stator inlet opening (90a) to a stator outlet opening (90b) and configured to accommodate the rotor (70), a drive motor (60) with a drive shaft coupled to the rotor (70) for transmitting torque, a first universal joint (22) engaged in transmitting torque between the drive shaft and the rotor, and a stator outlet flange (100) located downstream of the rotor (70) in the direction of flow. The first universal joint is connected to a wobble shaft, which is connected to a second universal joint, which is connected by means of a second shaft-hub connection to a hollow shaft coupled to the drive motor.The second shaft-hub connection can be connected and disconnected by a second clamping element, wherein - the second clamping element extends through the hollow shaft, is connected to the second shaft-hub connection on the side of the second cardan joint, and can be actuated with a tool on the side of the hollow shaft opposite the second cardan joint, or - the second clamping element can be actuated by means of a tool extending through the hollow shaft, and the second shaft-hub connection can be connected and disconnected from the side of the hollow shaft opposite the second cardan joint by means of the tool attached to the second clamping element.