Sealed oil-backed displacer suspension diaphragm

A displacer suspension system for a free piston Stirling engine having a hermetic vessel enclosing a working space adapted to contain a working gas and in which oscillates a displacer for displacing working gas back and forth between an expansion space in said working space serially through a heater, a regenerator, a cooler, and into a compression space in said working space, and then back again;

• said suspension system comprising:
• a first diaphragm fixed at its center and outer edge to said vessel and said displacer so that said diaphragm flexes between concave and convex shapes when said displacer oscillates;
• a rigid wall fastened to said displacer and extending generally parallel to said diaphragm;
• said rigid wall and said diaphragm bounding two sides of a first cavity adapted to be filled with an incompressible liquid;
• a piston mounted in said vessel and axially fixed with respect thereto;
• a cylinder formed in said rigid wall and receiving said piston for relative axial movement therewith;
• a second diaphragm sealed at its outer peripheral edge to said vessel and having one face defining with said rigid wall a second cavity adapted to be filled with said incompressible liquid, said cylinder communicating between said cavities and being substantially sealed by said piston, said second diaphragm flexing when said displacer moves from its center position and storing energy in so flexing that is returned to said displacer to restore said displacer from an extreme axial position toward said center position;
• whereby axial oscillation of said displacer causes said cylinder to reciprocate relative to said piston and causes said first diaphragm to flex between said concave and convex shapes, thereby displacing liquid in said first cavity, which liquid displacement is accommodated by movement of said piston in said cylinder, and leakage between said cylinder and said piston being contained by and returned from said second cavity.