Accumulator

An accumulator comprising:

• an accumulator housing which is provided with an oil port connected to a pressure piping and is provided with a gas filling port;
• a bellows and a bellows cap which section an internal space of said housing into a gas chamber filling gas therein and a fluid chamber communicating with said oil port;
• a pressure decreasing time safety mechanism which has a seal holder fixed to said bellows cap and a seal retained to said seal holder, and seals said fluid chamber by seating said seal on a seat surface in an inner portion of the housing in the case that the pressure of said fluid chamber is decreased in connection with the pressure decrease of said pressure piping, such that a part of the liquid is trapped in said fluid chamber;
• and
• an emergency safety mechanism which urgently opens the pressure in the inner portion of said housing to said oil port side in the case that the inner portion of said housing comes to a high temperature and a high pressure in an emergency,
• wherein said emergency safety mechanism communicates said fluid chamber and said oil port via a first pressure release flow passage which is formed by seating said seal holder having concavities and convexities in a part on a circumference on said seat surface, and a second pressure release flow passage which is formed by disappearance of an elastic body of said seal due to said high temperature,
• wherein said seal comprises a discoid metal member, said elastic body attached to at least a part a surface of said metal member, and an annular seal projection provided on a surface of said elastic body facing said oil port,
• wherein said seat surface includes an annular step formed therein and defining a first seat surface on an inner peripheral side and a second seat surface on an outer peripheral side such that said first seat surface is closer to said oil port than said second seat surface, and
• wherein said seal is configured to be seated on said first seat surface, and said seal holder is configured to be seated on said second seat surface.