US 5,174,153 AGranted

Device for detecting the level of a liquid in a receptacle

AssigneeKurita Water Industries Ltd.

InventorYoshimasa Nakano

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Abstract

The detecting device according to the present invention is provided with a case, a first and second detecting pads which juts from the case and which can be closely attached to the outer wall of the receptacle, supports which are connected to the first and second detecting pads in a thermal-conducting manner, a first thermistor and heater embedded in the support of the first detecting pad, a second thermistor embedded in the support of the second detecting pad, and a detector circuit which measures the quantity of heat transmitted from the first detecting pad into the receptacle in accordance with a change in the output of the first thermistor when the first detecting pad and the support thereof are heated by the heater to a preset temperature which is above the reference temperature of the second detecting pad and the support thereof, thus detecting the level of a liquid in the receptacle from the measured quantity of heat transmitted.

Claims9

Dependent claims

A device for detecting the surface level of a liquid contained in a thermal-conducting receptacle made of an untransparent material, the device comprising:

first and second heat conduction members to be in contact with an outer wall of the receptacle, said second heat conduction member being apart from said first heat conduction member in a horizontal direction;
a first temperature sensor for detecting temperature changes in said first heat conduction member;
a second temperature sensor for detecting the temperature of said second heat conduction member;
heating means for electrically heating said first heat conduction member to a preset temperature which is higher than that of said second heat conduction member detected by said second temperature sensor when said first and second heat conduction members are in contact with the outer wall of the receptacle;
and
controlling means for controlling the heating of said first heat conduction member by said heating means in accordance with an output change of said first temperature sensor, which output change results from the changes of an amount of transmitted heat, corresponding to the liquid level in the receptacle, that is released from said first heat conduction member into the receptacle through the outer wall of the receptacle.

3 more elements

Dependencies are inferred from the claim text.