Hydraulic capacity with controlled pressure absorption

A hydraulic capacity comprising:

• a hollow body which is having an elongated along an axis;
• and
• a rigid casing, said hollow body being made of a material that can withstand elastic expansion from a state of rest, at least in a radial direction with respect to said axis, said hollow body being defined, at rest, by a wall having a thickness which is between a minimum thickness and a maximum thickness, said wall being bordered by an orifice which is stationary with respect to said rigid casing, said rigid casing surrounding said hollow body to limit the expansion of said hollow body to define a capacity having at every instant an instantaneous volume of fluid which can change between a minimum volume and a maximum volume of fluid, said capacity applying an instantaneous pressure to said instantaneous volume as a function of said instantaneous volume, characterized in that said wall, at least for a first instantaneous volume of fluid is simultaneously in contact with said casing at least via a first zone and a second zone of said wall, said first and second zones being distant from said orifice, said first and second zones having first and second respective thickness which are separated from each other by a third zone having third thickness different from said first and second thickness.