Accumulator

An accumulator comprising;

• a casing having an inlet/outlet port;
• a cylinder disposed in said casing;
• a piston axially slidably disposed in said cylinder, said cylinder and one end of said piston jointly defining a reservoir of variable volume communicating with said inlet/outlet port and said piston having a coaxial recess extending from the other end of said piston to a bottom therein;
• a piston ring held on an outer surface of said piston, said piston ring and the inner surface of said bottom being located in substantially the same plane;
• a piston rod axially movably disposed in said casing and having an end slidably fitted in said coaxial recess;
• a spring engaged with said piston rod for normally urging said piston rod to keep said end of the piston rod and said piston ring positioned in substantially the same position at all times with respect to the longitudinal axis of said piston to force said piston into said reservoir;
• and
• means for electrically detecting the position of said piston in said cylinder.