Seal arrangement for an integral stirling cryocooler

A fluid machine comprising:

• housing means having a generally cylindrical piston bore formed therein with a radially extending top portion;
• piston means having an annular cylindrical portion with a transverse top section located in said cylindrical piston bore and operatively connected to driving means for reciprocating said piston means, within said cylindrical piston bore and forming a working space for gas with said radially extending top portion of said housing means during reciprocation of said piston means, said annular cylindrical portion including a first section located adjacent said driving means;
• said annular cylindrical portion of said piston means having a clearance with said piston bore such that contact does not take place therebetween during normal operation, a bellows assembly axially coextensive with said piston means having a first end secured and sealed to said housing means and a second end secured and sealed to said first section of said annular cylindrical portion whereby said bellows assembly expands and contracts due to reciprocating movement of said piston means;
• and
• a buffer means defining a space between said bellows assembly and the clearance between said annular cylindrical portion of said piston means and said piston bore and coaxial with said bellows assembly wherein pressure pulsations in the working space are essentially eliminated.