Acoustic liquid level detection

Abstract

The filling noise generated inside a pressurized container when liquid is injected into the container is detected at the outer end of a vent tube which extends into the container. When the level of liquid in the container reaches the lower end of the vent tube, the filling noise detected at the outer end is abruptly diminished. This abrupt change is detected and used to automatically terminate filling of the tank.

1 . Liquid level detection apparatus comprising:
 (a) a vent tube having a first end terminating inside an enclosed pressurized container and a second end terminating outside said container and vented to atmosphere;   (b) detection means positioned to detect filling noises generated within said pressurized container by liquid entering said pressurized container, which filling noises are then transmitted to atmosphere through said vent tube; and   (c) signaling means responsive to detected changes in said filling noise transmitted through said vent tube when said first end becomes submerged in liquid.   
     
     
         2 . Liquid level detection apparatus comprising:
 (a) a vent tube having a first end terminating inside an enclosed pressurized container and a second end terminating in a hollow chamber outside said pressurized container;   (b) detection means positioned to detect filling noises generated within said pressurized container by liquid entering said pressurized container, which filling noises are then transmitted to said hollow chamber through said vent tube; and   (c) signaling means responsive to detected changes in said filling noise transmitted through said vent tube when said first end becomes submerged in liquid.   
     
     
         3 . Liquid level detection apparatus as defined in  claim 2  wherein said hollow chamber is vented to atmosphere through an exit vent opening. 
     
     
         4 . Liquid level detection apparatus as defined in  claim 2  wherein said detection means includes an acoustic sensor mounted in said chamber. 
     
     
         5 . Liquid level detection apparatus as defined in  claim 1  wherein said signaling means controls the flow of liquid into said container. 
     
     
         6 . Liquid level detection apparatus as defined in  claim 1  wherein said signaling means comprises:
 (i) a signal processor which generates a cut-off signal in response to detected changes in said filling noise transmitted through said vent tube when said first end of said vent tube becomes submerged in liquid; and 
 (ii) a flow control valve responsive to said cut-off signal to stop flow of liquid into said pressurized container. 
 
     
     
         7 . The method of determining the level of liquid in a pressurized container comprising the steps of:
 (a) forming a conduit having a first end suspended at a predetermined level inside a pressurized container and a second end terminating outside said pressurized container and vented to atmosphere;   (b) generating filling noise in said pressurized container by injecting liquid into said pressurized container;   (c) transmitting said filling noises through said conduit from inside said pressurized container to atmosphere outside said pressurized container;   (d) detecting the filling noise transmitted through said conduit; and   (e) generating a cut-off signal in response to changes in said filling noise detected when the first end of said conduit becomes submerged in liquid in said container.   
     
     
         8 . Liquid level detection apparatus comprising:
 (a) a vent tube having a first end terminating inside an enclosed pressurized container and second end terminating outside said container and vented to atmosphere;   (b) detection means positioned outside said enclosed pressurized container and said vent tube to detect filling noises generated within said pressurized container by liquid entering said container and transmitted to atmosphere through said vent tube; and   (c) signaling means responsive to changes in said filling noise transmitted through said vent tube when said first end becomes submerged in liquid.   
     
     
         9 . Liquid level detection apparatus as defined in  claim 8  wherein said second end of said vent tube terminates in a hollow chamber. 
     
     
         10 . Liquid level detection apparatus as defined in  claim 9  wherein said hollow chamber is vented to atmosphere through an exit vent opening. 
     
     
         11 . Liquid level detection apparatus as defined in  claim 9  wherein said detection means includes an acoustic sensor mounted in said chamber. 
     
     
         12 . Liquid level detection apparatus as defined in  claim 8  wherein said signaling means controls the flow of liquid into said container. 
     
     
         13 . Liquid level detection apparatus as defined in  claim 8  wherein said detection means comprises:
 (i) a check valve positioned to close the second end of said vent tube; 
 (ii) a removable extension tube having an outlet end and an inlet end and adapted to mate with and open said check valve to form a continuous conduit from said first end of said vent tube to said outlet end of said extension tube; and 
 (iii) an acoustic sensor positioned to detect filling noise transmitted through said extension tube. 
 
     
     
         14 . Liquid level detection apparatus as defined in  claim 8  wherein said signaling means comprises:
 (i) a signal processor which generates a cut-off signal in response to changes in said filling noise transmitted through said vent tube when said first end of said vent tube becomes submerged in liquid; and 
 (ii) a flow control valve responsive to said cut-off signal to stop flow of liquid into said pressurized container. 
 
     
     
         15 . The method of determining the level of liquid in a pressurized container comprising the steps of:
 (a) forming a conduit having a first end suspended at a predetermined level inside a pressurized container and a second end terminating outside said pressurized container and vented to atmosphere;   (b) generating filling noise in said pressurized container by injecting liquid into said pressurized container;   (c) transmitting said filling noises to atmosphere through said conduit;   (d) using detection means located outside said pressurized container and said conduit to detect filling noise transmitted through said conduit to the outside of said container; and   (e) generating a cut-off signal in response to changes in said filling noise detected when the first end of said conduit becomes submerged in liquid in said container.