Evacuating a chamber

Patent metadata

Field	Value
Publication number	US-9695814-B2
Application number	US-201214124111-A
Country	US
Kind code	B2
Filing date	May 31, 2012
Priority date	Jun 16, 2011
Publication date	Jul 4, 2017
Grant date	Jul 4, 2017

Abstract

A method and apparatus for reducing undesirable noise generated by a vacuum pumping system. The vacuum system operates to reduce the pressure in a chamber to a first pressure value. The system then detects that the pressure at the vacuum pump system's inlet is about to change to a second higher pressure and, in response, the speed of a booster pump in the vacuum pump system is reduced below the rated speed for the pump. When the pressure at the vacuum pump's inlet is above the second pressure, the speed of the booster pump is increased to the rated speed. Thus, the booster pump is slowed down prior the pump system becoming exposed to a rapid increase in inlet pressure.

First claim

The invention claimed is:

1. A method of reducing noise generated by a vacuum pumping system operating to evacuate a chamber, the method comprising the steps of:
operating a booster pump of the vacuum pumping system at a rated speed while a valve between an inlet to the vacuum pumping system and the chamber is open to reduce chamber pressure to a first pressure;
determining that a pressure in the chamber increased to a second pressure that is higher than the first pressure while the pressure at the inlet of the vacuum pumping system remained at the first pressure due in part to the valve being closed;
determining that the closed valve is going to open such that the pressure at the inlet of the vacuum pumping system is going to change to the second pressure;
in response to determining that the pressure at the inlet of the vacuum pumping system is going to change to the second pressure, reducing the speed of the booster pump to a second speed that is below the rated speed; and then
increasing the speed of the booster pump to the rated speed when the pressure at the inlet of the vacuum pumping system increases from the first pressure when the valve is opened.

2. The method according to claim 1 , wherein the second pressure is atmospheric pressure.

3. The method according to claim 1 , wherein the second speed is less than half the rated speed.

4. The method according to claim 3 , wherein the second speed is 20% of the rated speed.

5. The method according to claim 1 , further comprising the step of decreasing the speed of the booster pump when the pressure in the chamber or at the inlet of the vacuum pumping system is below the first pressure.

6. The method according to claim 1 , further comprising the step of decreasing the speed of the booster pump by either introducing a gas load into the booster pump, or by activating a brake on a booster rotor of the booster pump, or by using a motor of the booster pump, or any combination thereof.

Assignees

• Stephens Philip John
• Thompson Michael Geoffrey
• Edwards Ltd

Inventors

• Stephens Philip John
• Thompson Michael Geoffrey

Classifications

• F04B49/06

  Control using electricity (regulating by means of floats actuating electric switches F04B49/04) · CPC title

• F04D27/0261

  by varying driving speed · CPC title

• F04D19/042 Primary

  Turbomolecular vacuum pumps · CPC title

• Y10T137/86083

  Vacuum pump · CPC title

• F04B49/20 Primary

  by changing the driving speed · CPC title