Vacuum Ejector With Multi-Nozzle Drive Stage

Abstract

So as to reduce its size, the invention provides a multistage ejector for generating a vacuum across a first, drive stage comprising a drive nozzle array for generating drive flow of air from a compressed air source, the drive nozzle array including two or more nozzles arranged to feed respective air jets together substantially directly into a common outlet of the drive stage so as to entrain air in a volume surrounding the air jets into the drive flow in order to generate a vacuum across the drive stage, the outlet of the drive stage being the inlet of a converging-diverging nozzle of a second stage, the converging-diverging nozzle being arranged to direct said air as a second stage air jet substantially directly into an outlet of the second stage so as to entrain air in a volume surrounding the second stage air jet into the flow in order to generate a vacuum across the second stage.

1 . A multi-stage ejector for generating a vacuum across a first, drive stage comprising a drive nozzle array for generating drive flow of air from a compressed air source, the drive nozzle array including two or more nozzles arranged to feed respective air jets together substantially directly into a common outlet of the drive stage so as to entrain air in a volume surrounding the air jets into the drive flow in order to generate a vacuum across the drive stage, the outlet of the drive stage being the inlet of a converging-diverging nozzle of a second stage, the converging-diverging nozzle being arranged to direct said air as a second stage air jet substantially directly into an outlet of the second stage so as to entrain air in a volume surrounding the second stage air jet into the flow in order to generate a vacuum across the second stage. 
     
     
         2 . The ejector of  claim 1 , wherein the outlet of the drive stage is formed as a second stage nozzle piece which is mounted to a nozzle piece-receiving structure of the ejector. 
     
     
         3 . The ejector of  claim 2 , wherein the second stage nozzle piece is press-fitted or snap-fitted into the nozzle piece-receiving structure. 
     
     
         4 . The ejector of  claim 2  or  3 , wherein the second stage nozzle piece includes one or more valve members coupled thereto or integrally-moulded therewith to open and close associated one or more valve openings. 
     
     
         5 . The ejector of  claim 2 ,  3  or  4 , wherein the drive nozzle array is mounted to the second stage nozzle piece. 
     
     
         6 . The ejector of any preceding claim comprising a drive nozzle piece in which the two or more drive nozzles are provided. 
     
     
         7 . The ejector of  claim 6 , wherein said drive nozzle piece is provided with spacing means for maintaining a desired spacing to the outlet of the drive stage. 
     
     
         8 . The ejector of any preceding claim, further comprising a converging-diverging nozzle at the outlet of the second stage. 
     
     
         9 . The ejector of any preceding claim, being an ejector cartridge and comprising:
 a housing defining at least said drive stage; and   one or more openings for placing said drive stage in fluid communication with a volume to be evacuated.   
     
     
         10 . The ejector of any of  claims 1  to  9 , being an ejector cartridge and comprising:
 a housing defining at least said drive stage and said second stage; and 
 openings for placing said stages in fluid communication with one or more volumes to be evacuated. 
 
     
     
         11 . The ejector cartridge of  claim 10 , wherein said housing defines one or more or all of said openings. 
     
     
         12 . The ejector cartridge of  claim 10  or  11 , further comprising one or more valves to control the direction of fluid communication between at least the second stage and a volume to be evacuated by the second stage. 
     
     
         13 . The ejector cartridge of  claim 10 ,  11  or  12 , further comprising a converging-diverging exit nozzle formed at the end of the cartridge through which said airflow exits the cartridge. 
     
     
         14 . The ejector cartridge of  claim 13 , wherein said housing defines the converging-diverging exit nozzle. 
     
     
         15 . The ejector cartridge of  claim 13  or  14 , wherein the converging-diverging exit nozzle is formed at the outlet of the second stage. 
     
     
         16 . The ejector cartridge of  claim 13 ,  14  or  15 , wherein the converging-diverging exit nozzle includes an annular undercut in the diverging section, at which there is a stepwise increase in the nozzle diameter. 
     
     
         17 . The ejector cartridge of any one of  claims 13  to  16 , wherein said housing is formed as a single ejector housing piece which integrally defines said drive stage, said second stage and said exit nozzle. 
     
     
         18 . The ejector cartridge of any one of  claims 13  to  16 , wherein said housing is formed of two or more ejector housing pieces joined for the nozzles to be one behind the other in the direction of airflow through the cartridge, the two or more ejector housing pieces including at least:
 a drive stage ejector housing piece integrally defining the drive stage and the second stage converging-diverging nozzle; and 
 a second stage ejector housing piece integrally defining the second stage and the converging-diverging exit nozzle. 
 
     
     
         19 . The ejector cartridge of any one of  claims 9  to  18 , wherein said housing is formed to be substantially rotationally symmetric around an axis which extends in the direction of airflow through the cartridge. 
     
     
         20 . The ejector cartridge of any one of  claims 9  to  16  or  19 , wherein said housing includes two outer shell pieces that are joined together along a line which extends along at least a part of the length of the cartridge in the direction of airflow through the cartridge. 
     
     
         21 . The ejector cartridge of any one of  claims 9  to  20  mounted in a substantially tubular bore defining a sealed volume surrounding the drive stage and at least one further stage and being connected to a volume to be evacuated, the drive stage and at least one further stage being arranged to evacuate said same surrounding volume and the connected volume to be evacuated. 
     
     
         22 . The ejector cartridge of any one of  claims 9  to  20  mounted in a substantially tubular bore defining respective sealed volumes surrounding the drive stage and least one further stage, the sealed volumes being connected to one or more volumes to be evacuated, the drive stage and at least one further stage being arranged to evacuate said respective surrounding volumes and the connected one or more volumes to be evacuated. 
     
     
         23 . The ejector of any preceding claim, wherein the drive nozzle array is press-fitted or snap-fitted into a drive nozzle array-receiving structure of the ejector. 
     
     
         24 . The ejector of any preceding claim, wherein the number of nozzles in the drive nozzle array is 2, 3, 4, 5 or 6. 
     
     
         25 . The ejector of any preceding claim, wherein the two or more nozzles of the drive nozzle array are arranged in a grouping such that all of the nozzles are disposed within a perimeter corresponding to the inner cross-sectional shape of the outlet of the drive stage, as viewed in the direction of airflow through the outlet the drive stage. 
     
     
         26 . The ejector of any preceding claim, wherein the nozzles of the drive nozzle array are arranged substantially parallel to each other. 
     
     
         27 . The ejector of any one of  claims 1  to  25 , wherein the nozzles of the drive nozzle array are arranged converging towards one another in the direction of airflow. 
     
     
         28 . An multi-stage ejector for generating a vacuum from a source of compressed air comprising:
 a drive nozzle chamber in which to generate a vacuum and having an inlet and an outlet at opposite ends of the drive nozzle chamber;   an outlet flow passage disposed at the outlet of the drive nozzle chamber; and   a drive nozzle array disposed at the inlet of the drive nozzle chamber and comprising two or more drive nozzles which are aligned in common with the outlet flow passage.   
     
     
         29 . The ejector of  claim 28  being a multi-stage ejector cartridge comprising:
 a housing defining at least the drive nozzle chamber and a second stage chamber having an inlet and an outlet at opposite ends of the second stage chamber; and 
 a converging-diverging nozzle as the outlet flow passage of the drive stage, the converging-diverging nozzle being disposed at the inlet of the second stage chamber and aligned with a second stage outlet flow passage. 
 
     
     
         30 . The ejector cartridge of  claim 29 , wherein the second stage outlet flow passage is a converging diverging nozzle. 
     
     
         31 . The ejector cartridge of  claim 30 , wherein said housing defines the converging-diverging nozzle of the second stage outlet flow passage. 
     
     
         32 . The ejector cartridge of  claim 30  or  31 , wherein the converging-diverging exit nozzle of the second stage outlet flow passage includes an annular undercut in the diverging portion, at which there is a stepwise increase in the nozzle diameter. 
     
     
         33 . The ejector cartridge of  claim 29 ,  30 ,  31  or  32 , wherein said housing further defines openings for placing said stages in fluid communication with one or more volumes to be evacuated. 
     
     
         34 . The ejector cartridge of  claim 33 , further comprising one or more valves to control the direction of fluid communication between at least the second stage and the volume to be evacuated. 
     
     
         35 . The ejector cartridge of any one of  claims 29  to  34 , wherein said housing is formed as a single piece. 
     
     
         36 . The ejector cartridge of  claim 35 , wherein said single piece housing integrally defines at least said drive stage, said second stage and said exit nozzle, and has a second stage nozzle piece and a drive nozzle piece mounted therein. 
     
     
         37 . The ejector cartridge of any one of  claims 29  to  34 , wherein said housing is formed of two or more ejector housing pieces joined for the nozzles to be one behind the other in the direction of the airflow through the cartridge. 
     
     
         38 . The ejector cartridge of  claim 37 , wherein a first of the two or more ejector housing pieces defines said drive stage integrally with said second stage nozzle, and a second of the two or more ejector housing pieces defines said second stage integrally with said exit nozzle. 
     
     
         39 . The ejector cartridge of any one of  claims 29  to  38 , wherein said housing is formed to be substantially rotationally symmetric around an axis in the direction of airflow through the cartridge. 
     
     
         40 . The ejector cartridge of any one of  claims 29  to  34  or  39 , wherein said housing includes two outer shell pieces that are joined along a line which extends along at least part of the length of the housing in the direction of airflow through the cartridge. 
     
     
         41 . The ejector cartridge of any one of  claims 29  to  40  mounted in a substantially tubular bore defining a sealed volume surrounding at least the drive stage and the second stage and being connected to a volume to be evacuated, the drive stage and second stage being arranged to evacuate said same surrounding volume and the connected volume to be evacuated. 
     
     
         42 . The ejector of any one of  claims 29  to  41 , wherein the converging-diverging nozzle which is the outlet flow passage of the drive stage is formed as a second stage nozzle piece which is mounted to a nozzle piece-receiving structure of the ejector. 
     
     
         43 . The ejector of  claim 42 , wherein the second stage nozzle piece is press-fitted or snap-fitted into the nozzle piece-receiving structure. 
     
     
         44 . The ejector of  claim 42  or  43 , wherein the second stage nozzle piece includes one or more valve members coupled thereto or integrally-moulded therewith to open and close associated one or more valve openings. 
     
     
         45 . The ejector of any one of  claims 28  to  44 , further comprising a drive nozzle piece in which the two or more drive nozzles are provided. 
     
     
         46 . The ejector of  claim 45 , wherein said drive nozzle piece is provided with spacing means, preferably in the form of bars, rods or posts extending forwards in the direction of airflow through the drive nozzle chamber, for maintaining a desired spacing to the outlet flow passage disposed at the outlet of the drive nozzle chamber. 
     
     
         47 . The ejector of any one of  claims 28  to  46 , wherein the drive nozzle piece is press-fitted or snap-fitted into a drive nozzle array-receiving structure of the ejector. 
     
     
         48 . The ejector of any one of  claims 28  to  47 , wherein the number of nozzles in the drive nozzle array is 2, 3, 4, 5 or 6. 
     
     
         49 . The ejector of any one of  claims 28  to  48 , wherein the two or more drive nozzles of the drive nozzle array are arranged in a grouping such that all of the drive nozzles are disposed within a perimeter corresponding to the inner cross-sectional shape of the outlet flow passage at the outlet of the drive stage, as viewed in the direction of airflow through the outlet flow passage. 
     
     
         50 . The ejector of any one of  claims 28  to  49 , wherein the drive nozzles of the drive nozzle array are arranged substantially parallel to each other. 
     
     
         51 . The ejector of any one of  claims 28  to  49 , wherein the drive nozzles of the drive nozzle array are arranged converging towards one another in the direction of airflow. 
     
     
         52 . A method of generating a vacuum from a source of compressed air comprising:
 supplying the compressed air to a drive nozzle array having at least two drive nozzles so as to generate respective air jets from each of the drive nozzles;   directing the air jets from each of the drive nozzles together substantially directly into the inlet of a converging-diverging nozzle located as a common outlet flow passage for the air jets from the drive nozzles downstream of the drive nozzle array;   generating a vacuum upstream of the inlet of the common outlet flow passage by entraining air from a volume surrounding the air jets into the jet flow; and   generating a jet flow of air with said converging-diverging nozzle and generating a vacuum downstream of said converging-diverging nozzle by entraining air from a surrounding volume into the jet flow from the converging-diverging nozzle.   
     
     
         53 . The method of  claim 52 , further comprising applying the vacuums generated upstream and downstream of the converging-diverging nozzle to evacuate a connected volume to be evacuated. 
     
     
         54 . The method of  claim 53 , wherein applying the vacuums generated upstream and downstream of the converging-diverging nozzle to evacuate a connected volume to be evacuated comprises initially applying both the upstream and downstream vacuums simultaneously to the connected volume and subsequently applying only the upstream vacuum to the connected volume after said connected volume has been partially evacuated. 
     
     
         55 . A method of making an ejector for generating a vacuum from a source of compressed air comprising:
 providing a drive nozzle array having at least two drive nozzles;   providing a drive nozzle chamber having an inlet and an outlet at opposite ends of the chamber;   providing a second stage chamber as the outlet flow passage of the drive nozzle chamber, the second stage chamber having its inlet connected to the outlet of the drive nozzle chamber; and   mounting the drive nozzle array at the inlet of the drive nozzle chamber so as to align the at least two drive nozzles in common with the inlet of the outlet flow passage.   
     
     
         56 . The method of  claim 55 , wherein providing a drive nozzle chamber includes providing a housing defining said chamber. 
     
     
         57 . The method of  claim 56 , wherein said housing further defines the second stage chamber. 
     
     
         58 . The method of  claim 57 , wherein said housing further defines an exit nozzle at an exit end of the housing as the outlet of the second stage. 
     
     
         59 . The method of  claim 57  or  58 , wherein providing a second stage chamber as the outlet flow passage of the drive nozzle chamber comprises providing a nozzle piece including a converging-diverging nozzle and inserting said nozzle piece from the inlet of the drive nozzle chamber to be mounted at the outlet of the drive nozzle chamber. 
     
     
         60 . The method of  claim 59 , wherein inserting said nozzle piece from the inlet of the drive nozzle chamber further comprises simultaneously inserting one or more valve members coupled to or formed integrally with the nozzle piece. 
     
     
         61 . The method according to any one of  claims 56  to  60 , wherein said drive nozzle array includes a drive nozzle piece having said drive nozzles provided therein, and wherein mounting the drive nozzle array at the inlet of the drive nozzle chamber so as to align the at least two drive nozzles in common with the inlet of the outlet flow passage further comprises inserting the drive nozzle piece from an inlet end of the housing to mount the nozzle piece at the inlet of the drive nozzle chamber. 
     
     
         62 . The method of any one of claims  568  to  61 , wherein mounting the drive nozzle array at the inlet of the drive nozzle chamber so as to align the at least two drive nozzles in common with the inlet of the outlet flow passage further comprises providing one or more spacing elements to obtain, a desired spacing between the drive nozzles and the inlet of the outlet flow passage. 
     
     
         63 . A method of making an ejector for generating a vacuum from a source of compressed air comprising:
 providing a drive nozzle chamber having an inlet and an outlet at opposite ends of the chamber;   providing a drive nozzle array having at least two drive nozzles at the inlet of the drive nozzle chamber;   providing an converging-diverging outlet flow passage; and   mounting the converging-diverging outlet flow passage at the outlet of the drive nozzle chamber so as to align the inlet of the outlet flow passage with each of the at least two drive nozzles in common.