Liquid level sensor

Abstract

A nebuliser cup for maintaining a safe level of liquid during nebulization, the cup comprising a liquid level sensor comprising: a first element sensing liquid at or below a position corresponding to a filled liquid level in the nebuliser cup; a second element electrically isolated from the first element and located at a position corresponding to a filled liquid level in the nebuliser cup; and wherein when the cup is not filled with a liquid to the filled liquid level, the first element, the liquid and the second element do not form an electrically coupled circuit; and when the cup is filled with a liquid to the filled liquid level, the first element, the liquid and the second element together form an electrically coupled circuit.

1 . A nebuliser cup with a liquid level sensor comprising:
 a first element sensing liquid at or below a position corresponding to a filled liquid level in the nebuliser cup;   a second element electrically isolated from the first element and located at a position corresponding to a filled liquid level in the nebuliser cup; and   wherein   when the cup is not filled with a liquid to the filled liquid level, the first element, the liquid and the second element do not form an electrically coupled circuit; and   when the cup is filled with a liquid to the filled liquid level, the first element, the liquid and the second element together form an electrically coupled circuit.   
     
     
         2 . A nebuliser cup according to  claim 1  wherein the first and second sensing elements are independently selected from the group consisting of electrically resistive and electrically capacitive. 
     
     
         3 . A nebuliser cup according to  claim 1  wherein the second element is a conductive level sensor. 
     
     
         4 . A nebuliser cup according to  claim 3  wherein the cup has a cup wall and the sensor passes through an insulated aperture in the cup wall. 
     
     
         5 . A nebuliser cup according to  claim 4  wherein the insulated aperture in the cup wall is an aperture surrounding an insulating sleeve. 
     
     
         6 . A nebuliser cup according to  claim 1  wherein the first element is the nebuliser cup. 
     
     
         7 . A nebuliser cup according to  claim 6  wherein the nebuliser cup is an electrically conducting plastic cup or metal cup. 
     
     
         8 . A nebuliser cup according to  claim 1  in operative contact with an ultrasonic transducer. 
     
     
         9 . A nebuliser cup according to  claim 18  in fluid communication with a sterilizing chamber. 
     
     
         10 . (canceled) 
     
     
         11 . (canceled) 
     
     
         12 . A nebuliser cup according to  claim 3  wherein the sensor is located at a position corresponding to a filled liquid level in the electrically conducting nebuliser cup. 
     
     
         13 . A nebuliser cup according to  claim 12  wherein the sensor passes through an insulated aperture in the cup wall. 
     
     
         14 . A nebuliser cup according to  claim 13  wherein the insulated aperture in the cup wall is an aperture surrounding an insulating sleeve. 
     
     
         15 . A nebuliser cup according to  claim 14  wherein the insulating sleeve extends beyond the wall of the cup to a distance such that a droplet of liquid is unable to complete a circuit with the sensor and the cup. 
     
     
         16 . A nebuliser cup according to  claim 15  wherein the insulating sleeve extends beyond the wall of the cup to a distance of at least 1 mm. 
     
     
         17 . A nebuliser cup according to  claim 1  in combination with a feedback loop and a liquid filling reservoir. 
     
     
         18 . A nebuliser cup according to  claim 8  further comprising an ultrasonic transducer located at or adjacent to the base of the nebuliser cup. 
     
     
         19 . A nebuliser cup according to  claim 18  wherein the ultrasonic transducer defines at least a portion of the base of the nebuliser cup. 
     
     
         20 . A nebuliser cup according to  claim 19  wherein the ultrasonic transducer acts directly upon the liquid in the cup to apply ultrasonic energy to the liquid in the cup, thereby resulting in generation of an aerosol from the surface of the liquid. 
     
     
         21 . A method of maintaining a liquid level in a nebuliser cup during operation, the method comprising:
 providing a first element at or below a position corresponding to a filled liquid level in a nebuliser cup;   providing a second element electrically isolated from the first element to contact a liquid at a position corresponding to a filled liquid level in the nebuliser cup;   providing sufficient liquid to the nebuliser cup to reach said fill level thereby to complete an electrically coupled circuit between the first element, the liquid and the second element;   and whereby a drop in the liquid level to below the fill level triggers a break in the circuit between the first element, the liquid and the second element; and   whereby the break in the circuit triggers dispensation of further liquid in the nebuliser cup.   
     
     
         22 . A method according to  claim 21  wherein the first element is the nebuliser cup. 
     
     
         23 . A method according to  claim 21  wherein sufficient further liquid is dispensed to the conductive nebuliser cup in response to the break in the circuit to restore the circuit and halt further dispensation of liquid into the reservoir. 
     
     
         24 . A method according to  claim 23  wherein the break in the circuit triggers dispensation of further liquid in the reservoir immediately. 
     
     
         25 . A method according to  claim 23  wherein the break in the circuit triggers dispensation of further liquid in the reservoir after a predetermined time. 
     
     
         26 . (canceled) 
     
     
         27 . (canceled) 
     
     
         28 . A method according to  claim 21  wherein the liquid used for sterilization is hydrogen peroxide solution or peracetic acid solution. 
     
     
         29 . A method according to  claim 21  wherein the sensor at or below fill level is configured maintain at least 5 mm depth of liquid in the nebuliser cup. 
     
     
         30 . A method according to  claim 21  wherein the sensor at or below fill level is configured to switch off the transducer when the volume of liquid in the nebuliser cup falls to about at least 1.5 cm 3  of liquid.