Evacuation apparatus

Abstract

The present invention discloses an evacuation apparatus for evacuating a tank, a chamber, and the like; wherein a mechanical vacuum booster pump is provided at an up-stream side of an exterior side vacuum pump; wherein the mechanical booster pump has a discharge openings for low compression and a discharge opening for discharging a high compression gas; wherein, in case when the exterior side vacuum pump starts discharging a gas, the gas is sent to the exterior side vacuum pump through all of the discharge openings for low compression and the discharge opening for discharging a high compression gas and, in case when the discharged gas pressure reaches afterward an ultimate pressure (a medium vacuum) attainable by the exterior side vacuum pump, the gas is sent to the exterior side vacuum pump only through the discharge opening for discharging a high compression gas.

1 . An evacuation apparatus for evacuating a tank, a chamber and the like; wherein a mechanical booster pump is provided at the up-stream side of an exterior side vacuum pump; wherein the mechanical booster pump comprises a discharge opening for discharging a low compression gas and a discharge opening for discharging a high compression gas; wherein, when the exterior side vacuum pump starts discharging a gas, the gas is sent to the exterior side vacuum pump through both the discharge opening for discharging a low compression gas and the discharge opening for discharging a high compression gas and, when the discharged gas pressure reaches afterward an ultimate pressure attainable by the exterior side vacuum pump, the gas is sent to the exterior side vacuum pump only through the discharge opening for discharging a high compression gas. 
   
   
       2 . An evacuation apparatus according to  claim 1 ; further comprising a pressure sensor for detecting a vacuum of the tank, the chamber and the like;
 wherein, when the ultimate pressure is detected by a signal from the pressure sensor, an installed controller closes an open/close valve, which is provided between the discharge opening for discharging a low compression gas and the exterior side vacuum pump.   
   
   
       3 . An evacuation apparatus according to  claim 1 ; further comprising a controller;
 wherein, in a case when a predetermined time passes after the exterior side vacuum pump starts discharging a gas till the ultimate pressure is attained, the controller closes an open/close valve which is provided between the discharge opening for discharging a low compression gas and the exterior side vacuum pump.   
   
   
       4 . An evacuation apparatus according to  claim 1 ; wherein the mechanical booster pump is a vacuum pump of a claw type; wherein the discharge opening for discharging a high compression gas is located at the wall of the pump casing, the wall being in a plane vertical to the axes of the pump rotors, while the discharge opening for discharging a high compression gas faces the compression space; wherein the discharge opening for discharging a low compression gas is located in a plane parallel to the plane containing both rotation axes of the pump rotors as well as the discharge openings for low compression located on a side-wall-surface of the pump casing; and further wherein the cross-sectional area of the discharge opening for discharging a low compression gas is formed more greatly than the cross-sectional area of the discharge opening for discharging a high compression gas.