Ejector-type vacuum pump assembly having stabilised membrane flow valve, and a method of controlling a vacuum level in a vacuum chamber of an ejector-type vacuum pump of the assembly

Abstract

Described is an ejector-type vacuum pump assembly that includes a stabilizing membrane flow valve, wherein a pilot flow of pressurized air is used to regulate a main flow of pressurized air for driving an ejector-type vacuum pump is disclosed. The pilot flow is led to a downstream side of the membrane flow valve and is fed to the ejector of the ejector-type vacuum pump along with the main flow of pressurised air. The ejector-type vacuum pump assembly is primarily intended for automated gripping operations using a suction gripper. Also disclosed is a method of controlling a vacuum level in a vacuum chamber of an ejector-type vacuum pump in an ejector-type vacuum pump assembly as described herein.

1 . An ejector-type vacuum pump assembly, said assembly comprising: 
 an ejector-type vacuum pump comprising 
 a pressure chamber, an ejector nozzle, a vacuum chamber, and an exhaust, the ejector nozzle fluidly connecting the vacuum chamber with the pressure chamber; 
 an inlet for pressurized air;  
 a first flow-control valve comprising a valve chamber, the first flow-control valve being configured to control a flow of pressurized air from the valve chamber to the pressure chamber; and,  
 a pressure sensor configured to sense a pressure (P) in the ejector-type vacuum pump assembly, 
   wherein   that the pressure sensor is located in the vacuum chamber;   that the valve chamber is fluidly connected to the inlet for pressurized air;   that the valve chamber comprises a bottom having an opening, a wall having an orifice fluidly connecting the valve chamber with the pressure chamber;   that, in the valve chamber of the first flow-control valve , a flexible, collapsible, cylindrical membrane is housed, the flexible, collapsible, cylindrical membrane being configured to seal against the bottom and/or to the wall, and, in a relaxed, un-collapsed state of the collapsible, flexible cylindrical membrane, to seal the orifice , the first flow-control valve further comprising an inner rigid flow chamber comprising, in an upstream end thereof, a flow restriction fluidly connecting the valve chamber with the rigid inner flow chamber, and, in a downstream end thereof, an outlet fluidly connected to the opening, the rigid inner flow chamber having in a side wall an orifice fluidly connecting the inner flow chamber with an inner volume enveloped by the collapsible, cylindrical, flexible membrane and the bottom, the upstream end of the rigid flow chamber being sealingly connected to an opening in an upstream end of the collapsible, cylindrical, flexible membrane; and, in additionally comprising: 
 a second flow-control valve configured to regulate a pilot flow of pressurized air from the inner flow chamber into the pressure chamber. 
   
     
     
         2 . The ejector-type vacuum pump assembly of  claim 1 , wherein the pressure sensor is additionally configured to send a pressure control signal (S 1 ) proportional to the pressure (P) sensed; and wherein the ejector-type vacuum pump assembly additionally comprises: 
 a controller (CU) configured to receive a pressure control signal (S 1 ) from the pressure sensor, to compare the pressure control signal (S 1 ) received with a desired target pressure (P TARGET ), to establish any existence of a pressure difference (ΔP) between the pressure sensed (P) and a desired target pressure (P TARGET ), and, in the case of an established existence of a pressure difference (ΔP) between the pressure sensed (P) and the desired target pressure (P TARGET ), to send a flow control actuation signal (S 2 ) to the second flow-control valve corresponding to the sign (+/-) of the pressure difference (ΔP) established between the pressure sensed (P) and the desired target pressure (P TARGET ).    
     
     
         3 . A method of controlling a vacuum level in a vacuum chamber of an ejector-type vacuum pump in an ejector-type vacuum pump assembly of  claim 1 , comprising the following steps: 
 A supplying pressurized air to an ejector-type vacuum pump assembly;   B monitoring a pressure (P) in a vacuum chamber of an ejector-type vacuum pump of the ejector-type vacuum pump assembly; and,   C controlling a flow-control valve based on the pressure (P) monitored, thereby regulating a pilot flow of pressurized air through the flow-control valve;   wherein a pressure differential between a reduced pressure produced by the pilot flow of pressurized air, and the pressure of the pressurized air being supplied to the ejector-type vacuum pump assembly in step A, regulates a flow of pressurized air driving the ejector-type vacuum pump.   
     
     
         4 . The method of controlling a vacuum level in a vacuum chamber of an ejector-type vacuum pump in an ejector-type vacuum pump assembly of  claim 3 , wherein a control unit (CU) is used to maintain a desired target pressure in vacuum chamber, wherein step B includes sensing a pressure (P) in the vacuum chamber and sending a pressure control signal (S 1 ) to the control unit (CU) proportional to the pressure (P) sensed in the in vacuum chamber, and wherein step C includes comparing the pressure control signal (S 1 ) received with a desired target pressure (P TARGET ), establishing any possible existence of a pressure difference (ΔP) between the pressure sensed (P) and the desired target pressure (P TARGET ), and, in the case of an established existence of a pressure difference (ΔP) between the pressure sensed (P) and the desired target pressure (P TARGET ), sending to the flow-control valve a flow control actuation signal (S 2 ) corresponding to the sign (+/-) of the pressure difference (ΔP) established between the pressure sensed (P) and the desired target pressure (P TARGET ).