Patent ID: 6510736
Filing Date: 2003-01-28
Classification: B67C,G01F

Abstract:
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; 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; wherein said bell mouth outlet provides an air lock, to preclude the entrance of liquid into said pressure sensing means; 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.