Patent ID: 7802470

Claim:
An ultrasonic liquid level detector comprising: a) a housing which is mounted above and spaced apart from the upper level of a body of liquid, the housing having upper and lower ends, wherein the housing is a cylinder having a hollow interior, wherein the housing is located inside of a drum that holds the liquid, wherein a longitudinally extending wall of the housing forms a portion of an exterior surface of the housing and a portion of an interior surface of the housing, wherein the housing has a closure plate located on one end thereof that defines a portion of the hollow interior; b) a reflector plate as a target positioned at the lower end of said housing so that when the level of the liquid of said body of liquid rises, the liquid will fill the space between the closure plate of the housing and the reflector plate; c) an ultrasonic transducer for generating high frequency sound waves and for receiving the echo of said generated waves, said frequency being selected so that waves generated at the selected frequency will reflect from the reflector plate in a liquid, said transducer being carried by said housing and being spaced apart from and above said reflector plate whereby when liquid fills the space between the transducer and the reflector plate, a wave generated by the transducer will reflect back from the reflector plate indicating that liquid is at the level of the transducer, wherein the transducer is located in the hollow interior of the housing; and d) a spring located in the hollow interior that contacts the longitudinally extending wall of the housing that forms a portion of the interior surface of the housing along the entire longitudinal length of the spring, wherein the spring urges the transducer towards the reflector plate and wherein a distal end of the transducer contacts the closure plate.