Method and apparatus for controlling fluid flow

Abstract

A method and apparatus for controlling bi-directional fluid flow. The apparatus has a pump that operates in a continuous pump cycle having a pressure phase and a vacuum phase. A conduit connects a common pump port to a utility port. An electrically-controlled valve regulates air flow through the conduit. The valve operates between a first position isolating the pump and the utility port, and a second position connecting the pump and the utility port in fluid communication. A detector continuously detects and communicates a signal identifying whether the pump is operating in the pressure or vacuum phase of the pump cycle. A controller uses the detector signal to synchronize actuation of the valve with the pump cycle to generate either continuous positive or continuous negative pressure at the utility port.

1 . A device for controlling bi-directional fluid flow, comprising: 
 a) a utility port;    b) a pump that produces bi-directional fluid flow at a common port and operates in a continuous pump cycle having a pressure phase and a vacuum phase;    c) a conduit connecting said common pump port to said utility port;    d) an electrically-controlled valve that regulates air flow through said conduit, said valve operating between a first position isolating said pump and said utility port, and a second position connecting said pump and said utility port in fluid communication;    e) a detector that continuously detects and communicates a signal identifying whether said pump is operating in the pressure or vacuum phase of the pump cycle; and,    f) controller connected to said detector and said valve, said controller using the detector signal to synchronize actuation of said valve with the pump cycle to generate either continuous positive or continuous negative pressure at said utility port.    
   
   
       2 . The device recited in  claim 1 , wherein negative pressure is generated at said utility port by cyclically actuating said valve to the second position during the negative pressure phase and then actuating the valve back to the first position during the pressure phase, and positive pressure is generated at said utility port by cyclically actuating said valve to the second position during the pressure phase and then actuating the valve back to the first position during the vacuum phase of the pump cycle.  
   
   
       3 . The device recited in  claim 2 , including means for controlling the flow rate through said utility port.  
   
   
       4 . The device recited in  claim 3 , wherein said flow rate control means changes the length of time said valve is actuated to the second position during either phase of the pump cycle.  
   
   
       5 . The device recited in  claim 1 , said pump including a reciprocating volume-displacement element that creates positive air pressure during one half of the pump cycle and creates negative air pressure during the other half of the pump cycle.  
   
   
       6 . The device recited in  claim 5 , wherein said detector comprises a photosensor that detects movement of said volume-displacement element.  
   
   
       7 . The device recited in  claim 5 , wherein said detector comprises an ultrasonic sensor that detects movement of said volume-displacement element.  
   
   
       8 . The device recited in  claim 1 , including means for controlling the flow of a measured volume (V) of fluid through said utility port.  
   
   
       9 . The device recited in  claim 1 , wherein said volumetric control means calculates and operates said pump for a calculated number (N) of pump cycles based on the volume displacement per stroke (DPS) of the pump.  
   
   
       10 . The device recited in  claim 1 , wherein said valve comprises a three-way solenoid valve having a common port connected to said pump, a normally-open (NO) port vented to the atmosphere, and a normally-closed (NC) port connected to said utility port.  
   
   
       11 . The device recited in  claim 10 , wherein said valve connects said NC port and said common port in fluid communication in the second position and connects said NO port and said common port in fluid communication in the first position.  
   
   
       12 . The device recited in  claim 1 , wherein said valve comprises a first, electrically-actuated, two-way valve controlling fluid flow through said conduit, and a second, electrically-actuated, two-way valve controlling fluid flow from said pump to the atmosphere.  
   
   
       13 . The device recited in  claim 1 , including a user interface connected to said controller.  
   
   
       14 . The device recited in  claim 9 , including a sensor that measures the head pressure at said utility port and communicates the head pressure to said controller.  
   
   
       15 . The device recited in  claim 14 , wherein said volumetric control means uses the head pressure to calculate the number (N) of pump cycles needed for the predetermined volumetric delivery.  
   
   
       16 . A device for controlling bidirectional fluid flow, comprising: 
 a) a utility port;    b) a pump that produces bi-directional fluid flow at a common port and operates in a continuous pump cycle having a pressure phase and a vacuum phase;    c) means for connecting said common port and said utility port in fluid communication;    d) means for regulating air flow between said common port and said utility port, said regulating means operating between a first position isolating said common port and said utility port, and a second position connecting said common port and said utility port in fluid communication;    e) means for continuously detecting whether said pump is operating in the pressure phase or vacuum phase of the pump cycle; and,    f) control means connected to said detecting means and said regulating means, said control means synchronizing actuation of said regulating means with the pump cycle to generate either continuous positive or continuous negative pressure at said utility port.    
   
   
       17 . The device recited in  claim 16 , including means for controlling the flow rate through said utility port.  
   
   
       18 . The device recited in  claim 16 , including means for controlling the flow of measured volumes (V) of fluid through said utility port.  
   
   
       19 . The device recited in  claim 16 , wherein said detecting means detects movement of a cyclically-moving element of said pump.  
   
   
       20 . A method of controlling positive and negative fluid flow through a utility port, comprising the steps of: 
 a) providing a fluid flow source that cyclically produces positive and then negative fluid pressure during the pressure phase and then vacuum phase, respectively, of a repeating cycle;    b) continuously detecting whether said source is operating in the pressure phase or vacuum phase;    c) producing positive fluid flow through the utility port by connecting said fluid flow source in fluid communication with said utility port during the pressure phase and isolating said fluid flow source from said utility port during the vacuum phase;    d) producing negative fluid flow through the utility port by connecting said fluid flow source in fluid communication with said utility port during the vacuum phase and isolating said fluid flow source from said utility port during the pressure phase.    
   
   
       21 . The method recited in  claim 20 , including the step of controlling the flow rate through the utility port.  
   
   
       22 . The method recited in  claim 20 , including the step of delivering measured volumes of fluid through the utility port.  
   
   
       23 . A pipetting device for admitting and emitting fluid from a disposable pipette, comprising: 
 a) a housing having a hand grip portion, a pipette connector, and a user interface;    b) a pump that produces bi-directional fluid flow at a common port and operates in a continuous pump cycle having a pressure phase and a vacuum phase;    c) a conduit connecting said pump to said pipette connector;    d) an electrically-controlled valve that regulates air flow through said conduit, said valve operating between a first position isolating said pump and said utility port, and a second position connecting said pump and said utility port in fluid communication;    e) a detector that continuously detects and communicates a signal identifying whether said pump is operating in the pressure or vacuum phase of the pump cycle;    f) controller connected to said detector and said valve, said controller using the detector signal to synchronize actuation of said valve with the pump cycle to generate either continuous positive or negative pressure at said pipette connector.    
   
   
       24 . The device recited in  claim 1 , wherein fluid is admitted to the pipette by cyclically actuating said valve to the second position during the negative pressure phase and then actuating said valve back to the first position during the pressure phase, and fluid is emitted from the pipette by cyclically actuating said valve to the second position during the pressure phase and then actuating said valve back to the first position during the vacuum phase of the pump cycle.  
   
   
       25 . The device recited in  claim 23 , including means for controlling the flow rate through the pipette.  
   
   
       26 . The device recited in  claim 23 , including means for admitting or emitting measured volumes of fluid through the pipette.  
   
   
       27 . The device recited in  claim 23 , including a sensor that measures the head pressure at said pipette connector.  
   
   
       28 . The device recited in  claim 23 , said pump comprising a diaphragm pump having a motor with shaft, and a reciprocating volume-displacement element connected to said shaft, said element creating positive pressure during one half of the pump cycle and creating negative pressure during the other half of the pump cycle.  
   
   
       29 . The device recited in  claim 25 , wherein reciprocation of said element through one complete pump cycle is synchronized with a single rotation of said shaft.  
   
   
       30 . The device recited in  claim 29 , wherein said detector comprises a photosensor that measures the angular location of said pump shaft.  
   
   
       31 . The device recited in  claim 23 , wherein said valve comprises a three-way solenoid valve having a common port connected to said pump, a normally-open (NO) port vented to the atmosphere, and a normally-closed (NC) port connected to said pipette connector.