Apparatus for indicating liquid level in a receptacle

Apparatus for indicating the liquid level in a receptacle, more particularly the oil level in the crankcase of an internal combustion engine, said apparatus comprising:

• a measure tube extending downwards into the crankcase below the lowermost design oil level;
• an indicating member connected to said measure tube by means of a slender flexible tube;
• means defining an air chamber in the indicating member, said air chamber being in air communication with said measure tube through the slender flexible tube;
• means defining a liquid chamber in the indicating member, said liquid chamber containing a quantity of liquid trapped therein below a column of air;
• an indicating tube in said indicating member having fluid communication with the liquid in said liquid chamber, said indicating tube having a transparent vertical wall and adapted to receive liquid from the liquid chamber to a height corresponding to the oil level in the crank case;
• means in said indicating member defining a narrow passage connecting said air chamber and the air above the liquid in said liquid chamber and including means connecting said air above the liquid and the ambient air for communication of air therebetween and between said measure tube and said liquid chamber;
• a pump member in the form of a wall defining one side of said air chamber and including means oeprational for separating said air chamber from the ambient air, said pump member being formed at least partly of a resilient diaphragm around a central wall portion and being manually pushable inwardly of said air chamber to a home position against a bottom wall thereof, the resilient diaphragm portion of said pump member being effective to first close said narrow passage to thereby close off air communication between said air chamber and the ambient air and the air above the liquid in said liquid chamber upon initial movement inwardly of the resilient diaphragm when said pump member is pushed inwardly of the air chamber;
• and
• a normally closed valve member located in said indicating member in an alternate passage connected to said narrow passage between said air chamber and the air above the liquid in said liquid chamber, said valve member being operable on pushing said pump member inwardly and fully home to thereby open air communication between said measure tube and the air above the liquid in said liquid chamber after closeoff of said air chamber and ambient air therefrom to enable indicating liquid to rise in said indicating tube to a height corresponding to the oil level in the crank case by air pressure being transmitted therethrough to said liquid chamber from said measure tube.