Rotary Vane Vacuum Pump Startup Torque Reduction
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Solution Overview
Problem
Vacuum pumps experience high torque during startup due to pressure differences across vanes and the transportation of sealing oil, which can lead to motor overload and potential startup failures.
Innovation Solution
Incorporating a venting channel with a flow control device that allows fluid communication between the exterior and a pumping chamber, reducing pressure differences by allowing fluid to enter the inlet pumping chamber during startup, and then impeding flow based on predetermined conditions such as time, speed, or sensor outputs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the pump starts up at atmospheric pressure without venting, then the pump can immediately begin evacuating the vacuum chamber, but the torque required to rotate the rotor becomes excessively high due to pressure differences across the vanes and oil transportation
Solution Approach 1:
The venting channel is opened before the pump starts evacuating the vacuum chamber, allowing the pumping chamber to be pre-pressurized to atmospheric pressure. This preliminary action eliminates the pressure difference across the vanes during startup, thereby reducing the torque on the motor while enabling immediate pump operation.
2Reliability
If a larger motor is selected to overcome the high startup torque, then the pump can reliably start up, but the device complexity and cost increase
Solution Approach 1:
By opening the venting channel before startup, the system preliminarily equalizes the pressure in the pumping chamber to atmospheric pressure. This eliminates the need for an oversized motor to overcome high startup torque, allowing a smaller, simpler motor to be used while maintaining reliable startup performance.
3Force
If the venting channel remains open during operation, then the pressure difference across the vanes remains reduced, but the pump cannot evacuate the vacuum chamber effectively
Solution Approach 1:
The venting channel is designed to be dynamically controllable, switching from an open state during startup to a closed state during operation. This dynamic adjustment allows the system to benefit from reduced torque during startup while maintaining vacuum evacuation efficiency during normal operation.
Solution Approach 2:
The system uses feedback from operational conditions to control the venting channel. During startup, the venting channel is open to reduce torque; once the pump is operating and evacuating the vacuum chamber, the venting channel is closed to maintain the pressure difference necessary for effective vacuum evacuation.
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 significantly reduces the maximum torque required during startup, allowing for a smaller motor size without compromising pump performance, and reduces the risk of startup failures.
Implementation Method 1
providing controlled venting of the pump at start up such that fluid is able to enter the inlet pumping chamber... By reducing the pressure difference across the vanes using a venting channel that provides a fluid passage to a region that is not at a reduced pressure
Data Source
AI summary
The rotary vane vacuum pump comprises: an inlet for connection to the vacuum chamber and an outlet for exhausting fluid pumped by the vacuum pump; a rotor and a motor for driving the rotor. The pump has a venting channel for venting one of the pumping chambers within the vacuum pump. The venting channel has a flow control device for controlling flow through the venting channel. The flow control device is configured to allow flow through the venting channel at start up of the pump and to impede flow through the venting channel in response to at least one of: a predetermined time elapsing, a speed of rotation of the rotor reaching a predetermined threshold value, a motor current reaching a predetermined value and an output from a sensor, the output from the sensor being indicative of operation of the vacuum pump.