Level detection head for hydrostatic effect with protection

Claim 1

A head for detecting a level of a liquid in a tank by hydrostatic action, said head being connected with a probe that is immersed into the liquid, the level of which is to be measured, said head comprising: a main enclosure subdivided into an upper chamber and a lower chamber, an elastically adjustable membrane separating said upper chamber from said lower chamber, probe means communicating with the upper chamber, an inlet pipe for gas under pressure communicating with the lower chamber, a valve connected to the membrane to control the pressure above the membrane in relation to the pressure below the membrane, means for diverting the flow of gas to the upper chamber from the lower chamber, a member sensitive to gas pressure for measuring the gas pressure that corresponds to a given flow of gas introduced through said inlet pipe compared to gas pressure from the tank to determine the height of the liquid in the tank, and a connection of the lower chamber with the probe means comprises an auxiliary chamber subdivided in an upper auxiliary chamber and a lower auxiliary chamber, another membrane separating said upper auxiliary chamber from said lower auxiliary chamber, the upper auxiliary chamber communicating with the lower chamber and the inlet of the gas under pressure when said valve is open, and the lower auxiliary chamber communicating with the upper chamber and the probe means when said probe means is open to gas flow, a calibrated elastic means of adjustment, and a probe valve being mounted to close said probe means without receipt of gas under pressure in said upper auxiliary chamber, which will prevent a rising of the liquid of the tank through the probe means.