Seal mechanism for a Stirling engine

A seal mechanism for a Stirling engine of the type having a displacer piston and a power piston slidably disposed inside a cylinder, the displacer piston having an upper ring groove and a lower ring groove and the power piston having one or more ring grooves, said seal mechanism comprising:

• an upper displacer piston ring which is mounted in said upper ring groove;
• a lower displacer piston ring which is mounted in said lower ring groove;
• said upper displacer piston ring and said lower displacer piston ring each comprise two loosely-fitting outer rings which are stacked on top of one another and which are each split by a slit in the radial direction, and an inner ring which is disposed inside of said outer rings;
• one or more power piston rings, each of which is mounted in one of said ring grooves of said power piston;
• and
• means for rendering the seals produced by said upper displacer piston ring and said lower displacer piston ring unidirectional in opposite directions, said last mentioned means comprising vents which are formed in one surface of said inner ring between the center and the outer surface of said inner ring, the surface having said vents of said inner ring of said upper displacer piston ring facing in the opposite direction from the surface having vents of said inner ring of said lower displacer piston ring.