Fluid seal apparatus

DETAILED DESCRIPTION To this end, the piston in the apparatus of the invention has a cavity opening out into the first volume of fluid, and the piston further includes at least one reservoir which is subjected to the pressure of the first volume of fluid, which is housed in said cavity, which contains the sealing liquid, and which communicates freely with said annular space via through orifices in the piston, the liquid thereby taking up respective levels firstly in the reservoir and secondly in the annular space, with the difference between these respective levels being a function of the difference between the respective pressures in the first and second volumes of fluid.
The property of this disposition whereby the height of the mercury seal automatically adapts to the difference between the respective pressures of the first and second volumes of fluid, thereby, in particular, avoiding the drawback from which a fixed-height seal would suffer, namely the drawback of running out under gravity if the pressure of the bottom volume is too low, and of not being able to withstand the pressure of the bottom volume if it is too high.
In a preferred embodiment, the annular space is specially provided in the outside periphery of the piston by shaping a middle portion of the height of the piston, with said through orifices in the piston opening out at the base of this middle portion.
Given the high density of mercury, the sealing liquid used is preferably a metal, but, in any event, it must be a liquid which is denser that the two fluids to be separated.
In order to provide better distribution of the sealing liquid, the reservoir containing the sealing liquid is preferably annular and in communication with the annular space via at least two orifices.
Given its sealing capabilities, the apparatus of the invention ideally applies to making a gas holder.