Patent ID: 7418861

Claim:
A liquid level sensor for measuring liquid levels in underground and above ground containers, comprising: a frame formed to have an elongate hollow tubular configuration that encloses a cavity, the frame having a first inner wall portion, a second inner wall portion and a lower end; a cam pivot having an end extending into the cavity from the first inner wall portion of the frame, the cam pivot being formed as an elongate projection extending substantially the entire length of the frame; a cam placed in the cavity, the cam being formed as an elongate rod having a lengthwise recess therein, the cam being arranged such that a portion of the cam pivot extends into the lengthwise recess such that the cam is pivotal about the end of the cam pivot, the cam having a cam arm extending therefrom; a float placed in the cavity; a spring arranged between the first inner wall portion of the frame and the cam arm, the spring being arranged to exert a force transverse to the length of the frame to bias the cam arm into contact with the float to force a side portion of the float into a locked position where it is in frictional engagement with the second inner wall portion of the frame; and a cam actuator pivotally mounted in a lower end portion of the frame, the cam actuator being arranged such that a first edge portion thereof is inside the cavity and a second edge portion thereof extends beyond the lower end of the frame when the float is in the locked position, the cam actuator being further arranged such that contact between the second edge portion and the container bottom exerts a force on the second edge portion causing rotation of the second edge portion into the cavity urges the first edge portion against the cam arm, thereby rotating the cam arm away from the float to release the float from the locked position to an unlocked position so that the float is free to seek the liquid level in the container.