Vacuum pump having expansion chamber and method of achieving ultimate pressure state in a vacuum pump using an expansion chamber

Abstract

A vacuum pump and a method of controlling the operation of the vacuum pump employ an expansion chamber to reduce a pressure differential between an inlet side and an exhaust side of the pump. In particular, the expansion chamber may be used to rid the pump head of the pump of a pocket of relatively high pressure fluid that accumulates behind a poppet valve disposed over an exhaust opening. The pump itself may be used to create a level of vacuum pressure in the expansion chamber. Alternatively, a piston or diaphragm may be used. In either case, the expansion chamber is isolated from the ambient and interior of the pump head once a level of vacuum pressure is produced in the expansion chamber. Then the exhaust outlet is redirected from the ambient to the interior of the expansion chamber.

What is claimed is: 
     
         1 . A vacuum pump comprising:
 an inlet portion having a pump inlet and constituting a vacuum side of the pump where fluid is drawn into the pump, and an exhaust portion having a pump outlet and constituting a compression side where fluid is discharged under pressure from the pump;   a pump head having an inlet opening to which the pump inlet extends, an exhaust opening leading to the pump outlet, and a compression mechanism constituted by at least one pocket;   a poppet valve having a valve head seated over the exhaust opening of the pump head;   an expansion chamber disposed outside the pump head, the expansion chamber having chamber walls delimiting an interior space;   vacuum pressure control means for selectively producing a vacuum in the expansion chamber; and   fluid directional flow control means for selectively placing the pump in a first state in which the exhaust opening of the pump head is in open communication with the interior space of the expansion chamber while the exhaust opening and the interior space of the expansion chamber are each closed to the pump outlet and a second state in which the exhaust opening of the pump head is in open communication with the pump outlet while the exhaust opening of the pump head is closed to the interior of the expansion chamber and the interior space of the expansion chamber is closed to the pump outlet.   
     
     
         2 . The scroll pump as claimed in  claim 1 , wherein the volume of the interior space of the expansion chamber is unchangeable. 
     
     
         3 . The scroll pump as claimed in  claim 2 , wherein the fluid directional flow control means comprises a first passageway that extends between the expansion chamber and the exhaust opening of the pump head without passing through the compression mechanism of the pump constituted by said at least one pocket, and a valve disposed in the first passageway, and
 the fluid pressure control means comprises a second passageway that extends between the expansion chamber and the pump inlet without passing through said compression mechanism of the pump, and a valve disposed in said second passageway.   
     
     
         4 . The scroll pump as claimed in  claim 2 , wherein the fluid directional flow control means comprises a first passageway that extends between the expansion chamber and the exhaust opening of the pump head without passing through the compression mechanism of the pump constituted by said at least one pocket, and a valve disposed in the first passageway, and
 the fluid pressure control means comprises a second passageway that extends between the expansion chamber and said compression mechanism of the pump, and a valve disposed in said second passageway.   
     
     
         5 . The scroll pump as claimed in  claim 1 , wherein the fluid directional flow control means comprises a passageway that extends between the expansion chamber and the exhaust opening of the pump head without passing through the compression mechanism of the pump constituted by said at least one pocket, and a valve disposed in the first passageway, and
 the fluid pressure control means comprises a mechanism that expands a volume of space in the expansion chamber.   
     
     
         6 . The scroll pump as claimed in  claim 5 , wherein the mechanism comprises a diaphragm or piston, and an actuator connected to the diaphragm or piston. 
     
     
         7 . A vacuum pump comprising:
 an inlet portion having a pump inlet and constituting a vacuum side of the pump where fluid is drawn into the pump, and an exhaust portion having a pump outlet and constituting a compression side where fluid is discharged under pressure from the pump;   a pump head having an inlet opening to which the pump inlet extends, an exhaust opening leading to the pump outlet, and a compression mechanism constituted by at least one pocket;   an expansion chamber disposed outside the pump head, the expansion chamber having chamber walls delimiting an internal space of an unchangeable volume; and   a system of passageways including a first passageway extending between the expansion chamber and the outlet portion of the pump head without passing through the compression mechanism of the pump constituted by said at least one pocket, and   a second passageway by which the interior of the expansion chamber is connected to the compression mechanism of the pump head, constituted by the at least one pocket, at a location upstream of the exhaust opening of the pump head.   
     
     
         8 . The scroll pump as claimed in  claim 7 , further comprising valves disposed in the system of passageways and operable to selectively open and close the interior of the expansion chamber to the exhaust opening of the pump head, to selectively open and close the exhaust outlet of the pump head to the pump outlet, and to selectively open and close the second passageway between the expansion chamber and the compression mechanism of the pump head constituted by the at least one pocket. 
     
     
         9 . The scroll pump as claimed in  claim 7 , further comprising a first valve disposed in the first passageway an operable to selectively place the pump in a first state in which the exhaust opening of the pump head is in open communication with the interior of the expansion chamber while the exhaust opening and the interior of the expansion chamber are each closed to the pump outlet and a second state in which the exhaust opening of the pump head is in open communication with the pump outlet while the exhaust opening of the pump head is closed to the interior of the expansion chamber and the interior of the expansion chamber is closed to the pump outlet. 
     
     
         10 . The scroll pump as claimed in  claim 7 , wherein the second passageway leads directly to the pump inlet. 
     
     
         11 . The scroll pump as claimed in  claim 7 , wherein the second passageway leads directly into the compression mechanism of the pump head constituted by the at least one pocket. 
     
     
         12 . The scroll pump as claimed in  claim 7 , further comprising a poppet valve having a valve head seated over the exhaust opening of the pump head. 
     
     
         13 . A method of operating a vacuum pump comprising an inlet portion having a vacuum side where a vacuum is created to draw fluid into the pump, an exhaust portion constituting a compression side where the fluid drawn into the pump is discharged under pressure fluid from the pump, a pump head having an inlet opening to which the pump inlet extends, an exhaust opening leading to the pump outlet, and a compression mechanism constituted by at least one pocket, the method comprising:
 operating the pump to draw fluid into the pump from a system;   monitoring a pressure of the fluid in the system while the pump is being operated;   evacuating an expansion chamber disposed outside the pump head until a first level of vacuum pressure exists within the expansion chamber, and then isolating the interior of the expansion chamber from the ambient outside the pump and from the interior of the pump head so as to maintain the first level of vacuum pressure in the expansion chamber;   when the pressure of the fluid in the system has stabilized to be within a first range and with the pressure in the expansion chamber at said first level, decreasing the pressure differential between the vacuum side and the compression side of the pump by placing the exhaust outlet of the pump head in open fluid communication with the interior of the expansion chamber while preventing the fluid from flowing out the pump outlet.   
     
     
         14 . The method of  claim 13 , further comprising:
 subsequently allowing fluid to flow out of the pump outlet and cutting off fluid communication between the expansion chamber and the exhaust outlet of the pump head when the pressure of the fluid flowing the pump reaches a second level.   
     
     
         15 . The method of  claim 13 , wherein the compression mechanism of the scroll pump is used to evacuate the expansion chamber to create the level of vacuum pressure in the expansion chamber. 
     
     
         16 . The method of  claim 15 , wherein the evacuating of the expansion chamber comprises placing the expansion chamber in fluid communication with the compression mechanism of the scroll pump via the pump inlet. 
     
     
         17 . The method of  claim 15 , wherein the evacuating of the expansion chamber comprises placing the expansion chamber in open fluid communication with the compression mechanism of the scroll pump at a location between the inlet and exhaust openings of the pump head. 
     
     
         18 . The method of  claim 15 , further comprising:
 subsequently allowing fluid to flow out of the pump outlet and cutting off fluid communication between the expansion chamber and the exhaust outlet of the pump head when the pressure of the fluid flowing the pump reaches a second level.   
     
     
         19 . The method of  claim 13 , wherein the evacuating of the expansion chamber to create the level of vacuum pressure in the expansion chamber comprises expanding a volume of space within the expansion chamber without venting the space. 
     
     
         20 . The method of  claim 15 , further comprising:
 subsequently allowing fluid to flow out of the pump outlet and cutting off fluid communication between the expansion chamber and the exhaust outlet of the pump head when the pressure of the fluid flowing the pump reaches a second level.