Multistage vacuum

Abstract

A multistage vacuum includes a tank and a vacuum generating head mounted on the tank. The vacuum generating head includes a housing having multiple chambers and a gang of parallel multistage ejectors, where the respective stages of each ejector share a common chamber.

1 . A vacuum generating head, comprising:
 a housing having a first chamber, a second chamber, and a third chamber; and   a gang of parallel ejector assemblies in the housing, each of said ejector assemblies comprising:
 an ejector nozzle in the first chamber configured to receive compressed air flow from a compressed air supply through a manifold inlet; 
 a first stage venturi having an inlet in the first chamber coaxially aligned with the ejector nozzle for receiving air flow from the ejector nozzle, the first stage venturi having an outlet extending into the second chamber; and 
 a second stage venturi having an inlet in the second chamber coaxially aligned with the outlet of the first stage venturi for receiving air flow from the first stage venturi, the second stage venturi having a diffuser outlet extending into the third chamber; 
   wherein the housing includes a first opening in the first chamber to receive a secondary air flow from a space in which negative pressure is generated;   wherein the housing includes a second opening with a flap valve in the second chamber to receive a secondary air flow from the space when the flap valve is open;   wherein the housing includes at least one port in the third chamber to exhaust air from the vacuum generating head.   
     
     
         2 . The vacuum generating head of  claim 1 , wherein the vacuum generating head has exactly four ejector assemblies in the housing. 
     
     
         3 . The vacuum generating head of  claim 2 , wherein the four ejector assemblies are arranged in a rectangular array in the housing. 
     
     
         4 . The vacuum generating head of  claim 1 , wherein the space in which negative pressure is generated comprises a filtered space in a tank having a vacuum inlet coupled to a vacuum hose. 
     
     
         5 . The vacuum generating head of  claim 1 , wherein the flap valve automatically opens based on the rate of the secondary air flow. 
     
     
         6 . The vacuum generating head of  claim 1 , wherein the housing comprises a main unit housing and an exhaust housing connected to the main unit housing. 
     
     
         7 . The vacuum generating head of  claim 6 , wherein the first and second chambers are in the main unit housing and the third chamber is in the exhaust housing. 
     
     
         8 . The vacuum generating head of  claim 1 , wherein at least the third chamber in the housing is lined with sound deadening foam. 
     
     
         9 . A multistage vacuum, comprising:
 (a) a tank including a vacuum inlet; and   (b) a vacuum generating head mounted on the tank comprising:
 a housing having a first chamber, a second chamber, and a third chamber; and 
 a gang of parallel ejector assemblies in the housing, each of said ejector assemblies comprising:
 an ejector nozzle in the first chamber configured to receive compressed air flow from a compressed air supply through an inlet in the housing; 
 a first stage venturi having an inlet in the first chamber coaxially aligned with the ejector nozzle for receiving air flow from the ejector nozzle, the first stage venturi having an outlet extending into the second chamber; and 
 a second stage venturi having an inlet in the second chamber coaxially aligned with the outlet of the first stage venturi for receiving air flow from the first stage venturi, the second stage venturi having a diffuser outlet extending into the third chamber; 
 
 wherein the housing includes a first opening in the first chamber to receive a secondary air flow from a space in the tank in which negative pressure is generated; 
 wherein the housing includes a second opening with a flap valve in the second chamber to receive a secondary air flow from the space in the tank when the flap valve is open; 
 wherein the housing includes at least one port in the third chamber to exhaust air from the vacuum generating head. 
   
     
     
         10 . The multistage vacuum of  claim 9 , wherein the vacuum generating head has exactly four ejector assemblies in the housing. 
     
     
         11 . The multistage vacuum of  claim 10 , wherein the four ejector assemblies are arranged in a rectangular array in the housing. 
     
     
         12 . The multistage vacuum of  claim 9 , wherein the tank further includes a filter in the space in which negative pressure is generated. 
     
     
         13 . The multistage vacuum of  claim 9 , wherein the flap valve automatically opens based on the rate of the secondary air flow. 
     
     
         14 . The multistage vacuum of  claim 9 , wherein the housing comprises a main unit housing and an exhaust housing connected to the main unit housing. 
     
     
         15 . The multistage vacuum of  claim 14 , wherein the first and second chambers are in the main unit housing and the third chamber is in the exhaust housing. 
     
     
         16 . The multistage vacuum of  claim 9 , wherein at least the third chamber in the housing is lined with sound deadening foam. 
     
     
         17 . The multistage vacuum of  claim 9 , wherein the vacuum generating head does not extend beyond the periphery of the tank. 
     
     
         18 . A multistage vacuum, comprising:
 a tank including a vacuum inlet; and   a vacuum generating head mounted on the tank comprising a housing and a gang of parallel multistage ejectors in the housing, wherein respective stages of each ejector share a common chamber in the housing.   
     
     
         19 . The multistage vacuum of  claim 18 , wherein the vacuum generating head comprises a first chamber, a second chamber, and a third chamber in the housing, and wherein each ejector comprises: (a) an ejector nozzle in the first chamber configured to receive compressed air flow from a compressed air supply through an inlet in the housing, (b) a first stage venturi having an inlet in the first chamber coaxially aligned with the ejector nozzle for receiving air flow from the ejector nozzle, the first stage venturi having an outlet extending into the second chamber, and (c) a second stage venturi having an inlet in the second chamber coaxially aligned with the outlet of the first stage venturi for receiving air flow from the first stage venturi, the second stage venturi having a diffuser outlet extending into the third chamber. 
     
     
         20 . The multistage vacuum of  claim 19 , wherein the housing includes a first opening in the first chamber to receive a secondary air flow from a space in the tank; wherein the housing includes a second opening with a flap valve in the second chamber to receive a secondary air flow from the space when the flap valve is open; and wherein the housing includes at least one port in the third chamber to exhaust air from the vacuum generating head.