Liquid level measuring apparatus and method

Claim 1

A method for measuring the amount of liquid in a tank having a communicating conduit for releasing a gas adjacent the bottom of said tank, said method comprising the steps of: (1) introducing a first volume of gas into said conduit at a relatively high rate of flow to substantially clear said conduit of liquid; (2) thereafter introducing into said conduit at a relatively low rate of flow a second fixed volume of gas in excess of an amount necessary to maintain said conduit free of liquid being measured, with sufficient excess gas to bubble up through the liquid in the tank, said fixed volume being the same each time the method is practiced; and (3) determining, at the end of step (2), the pressure in said conduit and converting it to a measurement of the amount of liquid in said tank.

Claim 2

A method for measuring the amount of liquid in a tank having a communicating conduit for releasing a gas adjacent the bottom of said tank, said method comprising the steps of: (1) introducing a first volume of gas into said conduit at a relatively high rate of flow to substantially clear said conduit of liquid; (2) thereafter introducing into said conduit at a relatively low rate of flow a second fixed volume of gas in excess of an amount necessary to maintain said conduit free of liquid being measured, with sufficient excess gas to bubble up through the liquid in the tank, said fixed volume being the same each time the method is practiced; and (3) determining, at the end of step (2), the pressure in said conduit and converting it to a measurement of the amount of liquid in said tank.

Claim 10

An apparatus for measuring the amount of liquid in a tank, comprising: (1) a conduit for releasing a gas adjacent the bottom of said tank; (2) supply means for introducing a first volume of gas into said conduit at a relatively high rate of flow to substantially clear said conduit of liquid; (3) means for introducing into said conduit at a relatively low rate of flow a second fixed volume of gas in excess of an amount necessary to maintain said conduit free of liquid being measured, with sufficient excess gas to bubble up through the liquid in the tank, said second fixed volume being the same each time the apparatus is actuated; and (4) sensing means for determining the pressure in said conduit so that it can be converted to a measurement of the amount of liquid in said tank.

Claim 11

An apparatus for measuring the amount of liquid in a tank, comprising: (1) a conduit for releasing a gas adjacent the bottom of said tank; (2) supply means for introducing a first volume of gas into said conduit at a relatively high rate of flow to substantially clear said conduit of liquid; (3) means for introducing into said conduit at a relatively low rate of flow a second fixed volume of gas in excess of an amount necessary to maintain said conduit free of liquid being measured, with sufficient excess gas to bubble up through the liquid in the tank, said second fixed volume being the same each time the apparatus is actuated; and (4) sensing means for determining the pressure in said conduit so that it can be converted to a measurement of the amount of liquid in said tank.

Claim 23

An apparatus for measuring the amount of liquid in a tank, comprising: (1) a source of gas under pressure; (2) a reservoir of fixed volume; (3) a first passageway placing said reservoir in communication with said source of gas under pressure; (4) a valve in said first passageway for controlling gas flow therethrough; (5) a second passageway for placing said reservoir in communication with the bottom of a tank to be measured; (6) a calibrated orifice in said second passageway; (7) actuating means for opening said valve to permit gas under pressure to flow a relatively high rate into said reservoir and for thereafter closing said first valve and causing a fixed volume of gas to flow at a relatively low controlled rate from said reservoir through said calibrated orifice to the bottom of said tank; and (8) means for indicating the pressure of said gas downstream of said orifice so that it can be converted to a measurement of the amount of liquid in said tank.

Claim 24

An apparatus for measuring the amount of liquid in a tank, comprising: (1) a source of gas under pressure; (2) a reservoir of fixed volume; (3) a first passageway placing said reservoir in communication with said source of gas under pressure; (4) a valve in said first passageway for controlling gas flow therethrough; (5) a second passageway for placing said reservoir in communication with the bottom of a tank to be measured; (6) a calibrated orifice in said second passageway; (7) actuating means for opening said valve to permit gas under pressure to flow a relatively high rate into said reservoir and for thereafter closing said first valve and causing a fixed volume of gas to flow at a relatively low controlled rate from said reservoir through said calibrated orifice to the bottom of said tank; and (8) means for indicating the pressure of said gas downstream of said orifice so that it can be converted to a measurement of the amount of liquid in said tank.

Claim 25

An apparatus for measuring the amount of liquid in a tank, comprising: (1) a source of gas under pressure; (2) a reservoir of fixed volume; (3) a first passageway placing said reservoir in communication with said source of gas under pressure; (4) a first valve in said first passageway for controlling gas flow therethrough; (5) a second passageway for placing said reservoir in communication with the bottom of a tank to be measured; (6) a second valve in said second passageway for controlling gas flow therethrough; (7) a calibrated orifice in said second passageway bypassing said second valve; (8) actuating means for opening said first valve to permit gas under pressure to flow at a relatively high rate initially into said reservoir and through said reservoir and said second passageway to the bottom of said tank, and for thereafter closing said first and second valves to permit the fixed volume of gas in said reservoir to flow at a relatively low controlled rate through said calibrated orifice to the bottom of said tank; and (9) means for indicating the pressure of said gas downstream of said orifice.

Claim 26

An apparatus for measuring the amount of liquid in a tank, comprising: (1) a source of gas under pressure; (2) a reservoir of fixed volume; (3) a first passageway placing said reservoir in communication with said source of gas under pressure; (4) a first valve in said first passageway for controlling gas flow therethrough; (5) a second passageway for placing said reservoir in communication with the bottom of a tank to be measured; (6) a second valve in said second passageway for controlling gas flow therethrough; (7) a calibrated orifice in said second passageway bypassing said second valve; (8) actuating means for opening said first valve to permit gas under pressure to flow at a relatively high rate initially into said reservoir and through said reservoir and said second passageway to the bottom of said tank, and for thereafter closing said first and second valves to permit the fixed volume of gas in said reservoir to flow at a relatively low controlled rate through said calibrated orifice to the bottom of said tank; and (9) means for indicating the pressure of said gas downstream of said orifice.

Claim 34

An apparatus for measuring the amount of liquid in a tank, comprising: (1) a source of gas under pressure; (2) a reservoir of fixed volume; (3) a first passageway placing said reservoir in communication with said source of gas under pressure; (4) a first valve in said first passageway for controlling gas flow therethrough; (5) a second passageway for placing said reservoir in communication with the bottom of a tank to be measured; (6) a second valve in said second passageway for controlling gas flow therethrough, said second valve comprising a pair of engaging valve surfaces; (7) a calibrated orifice in said second passageway bypassing said second valve, said orifice comprising a groove on one of said valve surfaces; (8) actuating means for opening said first valve to permit gas under pressure to flow initially into said reservoir and through said reservoir and said second passageway to the bottom of said tank, and for thereafter closing said first and second valves to permit the volume of gas in said reservoir to flow at a controlled rate through said calibrated orifice to the bottom of said tank; and (9) means for indicating the pressure of said gas downstream of said orifice.

Claim 35

An apparatus for measuring the amount of liquid in a tank, comprising: (1) a source of gas under pressure; (2) a reservoir of fixed volume; (3) a first passageway placing said reservoir in communication with said source of gas under pressure; (4) a first valve in said first passageway for controlling gas flow therethrough; (5) a second passageway for placing said reservoir in communication with the bottom of a tank to be measured; (6) a second valve in said second passageway for controlling gas flow therethrough, said second valve comprising a pair of engaging valve surfaces; (7) a calibrated orifice in said second passageway bypassing said second valve, said orifice comprising a groove on one of said valve surfaces; (8) actuating means for opening said first valve to permit gas under pressure to flow initially into said reservoir and through said reservoir and said second passageway to the bottom of said tank, and for thereafter closing said first and second valves to permit the volume of gas in said reservoir to flow at a controlled rate through said calibrated orifice to the bottom of said tank; and (9) means for indicating the pressure of said gas downstream of said orifice.