Liquid depth sensing system

Abstract

The present invention is a liquid depth sensing system utilizing the bubble tube or purge operating principle. In this system, a pneumatic tube extends downwardly into the liquid, and air (or other gas) passes through the tube to bubble from the lower end thereof. The air or gas pressure within the tube is equal to the head pressure of the liquid, thus allowing the liquid depth to be determined by measuring the air or gas pressure. Prior art systems are relatively bulky, maintenance prone, and require relatively high energy input due to the constant operation of the relatively large pneumatic pump motor and its high output pressure required due to the electromechanical pressure regulator installed downstream of the pneumatic pump. The present invention overcomes these deficiencies by using the pneumatic pump motor as the regulating device, by operating the motor only as required to produce only sufficient pressure for measuring the liquid depth. In some embodiments of the present system, a regulator valve provides adjustment of the output flow from the pump for additional accuracy. In other embodiments, a differential pressure transducer provides feedback to the motor controller to preclude requirement for the regulator valve. The present system may be applied to either open or closed liquid containers (e.g., fuel quantity indication), and may be adapted for use in the bottling industry to provide extreme accuracy and rapid shutoff during filling operations, and in other industries (automotive manufacture, etc.) where accurate and rapid filling of various components is required.

I claim:  
     
         1 . A liquid depth sensing system for measuring the depth of a liquid, comprising: 
 a container devoid of internal electronic componentry, for holding a liquid;    a dip tube having at least an open lower end extending into said container, for delivering a gas into said container;    said dip tube further having an upper end opposite said lower end, and an internal diameter;    a pneumatic pump disposed externally to said container, for supplying the gas;    a gas inlet, for supplying the gas to said pneumatic pump;    a gas delivery line extending between said pneumatic pump and said upper end of said dip tube, for supplying the gas from said pneumatic pump to said dip tube;    electric drive means disposed externally to said container, for driving said pneumatic pump at sufficient pressure to force the gas from said lower end of said dip tube;    gas differential pressure sensing means disposed externally to said container and communicating with said gas delivery line and said gas inlet, for determining the gas pressure within said gas delivery line downstream of said pneumatic pump;    said gas differential pressure sensing means communicating with said electric drive means for controlling said electric drive means, for regulating the gas pressure by said electric drive means as required;    a bell mouth outlet depending from said lower end of said dip tube, for capturing a volume of gas therein;    said bell mouth outlet having an internal diameter greater than said internal diameter of said dip tube; and    said internal diameter of said dip tube restricting the volume of gas to a narrow and tall column, for rapidly actuating said differential pressure sensing means as the tall column of gas is pushed upwardly within said dip tube by means of the liquid entering said container.    
     
     
         2 . The liquid depth sensing system according to  claim 1 , wherein said container comprises a closed container.  
     
     
         3 . The liquid depth sensing system according to  claim 2 , further including: 
 liquid quantity display means; and    said dip tube, said pneumatic pump, said gas delivery line, said electric drive means, said gas differential pressure sensing means, and said liquid quantity display means comprise a liquid quantity monitoring system for determining the quantity of the liquid within said closed container.    
     
     
         4 . The liquid depth sensing system according to  claim 1 , wherein said container comprises an open container.  
     
     
         5 . The liquid depth sensing system according to  claim 4 , wherein said dip tube with said bell mouth outlet, said pneumatic pump, said gas delivery line, said electric drive means, and said gas differential pressure sensing means further comprise an open container fill system for rapidly and accurately filling an open container to a predetermined level.  
     
     
         6 . The liquid depth sensing system according to  claim 1 , further including: 
 at least one electromagnetic coil circuit for actuating said electric drive means;    electrical pulse actuator means, for providing electrical pulses to said electromagnetic coil circuit for incrementally actuating said electric drive means through partial cycles; and    electronic switching means communicating with said electrical pulse actuator means and with said gas differential pressure sensing means, for grounding said electrical pulse actuator means and removing electrical power to said electromagnetic coil circuit, thereby terminating operation of said electric drive means and said pneumatic pump when a predetermined gas pressure is sensed by said gas differential pressure sensing means.    
     
     
         7 . A liquid depth sensing system for measuring the depth of a liquid, comprising: 
 a container devoid of internal electronic componentry, for holding a liquid;    a dip tube having at least an open lower end extending into said container, for delivering a gas into said container;    said dip tube further having an upper end opposite said lower end, and an internal diameter;    a pneumatic pump disposed externally to said container, for supplying a gas;    a gas inlet, for supplying the gas to said pneumatic pump;    a gas delivery line extending between said pneumatic pump and said upper end of said dip tube, for supplying the gas from said pneumatic pump to said dip tube;    electric drive means disposed externally to said container, for driving said pneumatic pump at sufficient pressure to force the gas from said lower end of said dip tube;    gas differential pressure sensing means disposed externally to said container and communicating with said gas delivery line and the pressure of said gas delivery line, for determining the gas pressure within said gas delivery line downstream of said pneumatic pump; and    said gas differential pressure sensing means communicating with said electric drive means for controlling said electric drive means, for regulating the gas pressure by said electric drive means as required.    
     
     
         8 . The liquid depth sensing system according to  claim 7 , wherein said container comprises a closed container.  
     
     
         9 . The liquid depth sensing system according to  claim 8 , further including: 
 liquid quantity display means; and    said dip tube, said pneumatic pump, said gas delivery line, said electric drive means, said gas differential pressure sensing means, and said liquid quantity display means comprise a liquid quantity monitoring system for determining the quantity of the liquid within said closed container.    
     
     
         10 . The liquid depth sensing system according to  claim 7 , wherein said container comprises an open container.  
     
     
         11 . The liquid depth sensing system according to  claim 10 , including: 
 a bell mouth outlet depending from said lower end of said dip tube, for capturing a volume of gas therein;    said bell mouth outlet having an internal diameter greater than said internal diameter of said dip tube; and    said internal diameter of said dip tube restricting the volume of gas to a narrow and tall column, for rapidly actuating said differential pressure sensing means as the tall column of gas is pushed upwardly within said dip tube by means of the liquid entering said container.    
     
     
         12 . The liquid depth sensing system according to  claim 11 , wherein: 
 said dip tube with said bell mouth outlet, said pneumatic pump, said gas delivery line, said electric drive means, and said gas differential pressure sensing means further comprise an open container fill system for rapidly and accurately filling an open container to a predetermined level.    
     
     
         13 . The liquid depth sensing system according to  claim 7 , further including: 
 at least one electromagnetic coil circuit for actuating said electric drive means;    electrical pulse actuator means, for providing electrical pulses to said electromagnetic coil circuit for incrementally actuating said electric drive means through partial cycles; and    electronic switching means communicating with said electrical pulse actuator means and with said gas differential pressure sensing means, for grounding said electrical pulse actuator means and removing electrical power to said electromagnetic coil circuit, thereby terminating operation of said electric drive means and said pneumatic pump when a predetermined gas pressure is sensed by said gas differential pressure sensing means.    
     
     
         14 . A liquid depth sensing system for measuring the depth of a liquid, comprising: 
 a container for holding a liquid;    a dip tube having at least an open lower end extending into said container, for delivering a gas into said container;    said dip tube further having an upper end opposite said lower end, and an internal diameter;    means for supplying and regulating a gas to said dip tube;    a bell mouth outlet depending from said lower end of said dip tube, for capturing a volume of gas therein;    said bell mouth outlet having an internal diameter greater than said internal diameter of said dip tube; and    said internal diameter of said dip tube restricting the volume of gas to a narrow and tall column, for rapidly actuating said differential pressure sensing means as the tall column of gas is pushed upwardly within said dip tube by means of the liquid entering the container.    
     
     
         15 . The liquid depth sensing system according to  claim 14 , wherein said container comprises a closed container.  
     
     
         16 . The liquid depth sensing system according to  claim 15 , further including: 
 liquid quantity display means; and    said dip tube, said means for supplying and regulating a gas to said dip tube, and said liquid quantity display means comprise a liquid quantity monitoring system for determining the quantity of the liquid within said closed container.    
     
     
         17 . The liquid depth sensing system according to  claim 14 , wherein said container comprises an open container.  
     
     
         18 . The liquid depth sensing system according to  claim 17 , wherein said dip tube with said bell mouth outlet and said means for supplying and regulating a gas to said dip tube further comprise an open container fill system for rapidly and accurately filling an open container to a predetermined level.  
     
     
         19 . The liquid depth sensing system according to  claim 14 , wherein said means for supplying and regulating a gas to said dip tube further comprises: 
 a pneumatic pump disposed externally to said container, for supplying a gas;    a gas inlet, for supplying the gas to said pneumatic pump;    a gas delivery line extending between said pneumatic pump and said upper end of said dip tube, for supplying the gas from said pneumatic pump to said dip tube;    electric drive means disposed externally to said container, for driving said pneumatic pump at sufficient pressure to force the gas from said lower end of said dip tube;    gas differential pressure sensing means disposed externally to said container and communicating with said gas delivery line and the pressure of said gas delivery line, for determining the gas pressure within said gas delivery line downstream of said pneumatic pump; and    said gas differential pressure sensing means communicating with said electric drive means for controlling said electric drive means, for regulating the gas pressure by said electric drive means as required.    
     
     
         20 . The liquid depth sensing system according to  claim 19 , further including: 
 at least one electromagnetic coil circuit for actuating said electric drive means;    electrical pulse actuator means, for providing electrical pulses to said electromagnetic coil circuit for incrementally actuating said electric drive means through partial cycles; and    electronic switching means communicating with said electrical pulse actuator means and with said gas differential pressure sensing means, for grounding said electrical pulse actuator means and removing electrical power to said electromagnetic coil circuit, thereby terminating operation of said electric drive means and said pneumatic pump when a predetermined gas pressure is sensed by said gas differential pressure sensing means.