External combustion engines

In a thermal machine of the type having a machine body with a main axis extending between a thermal end and a work end, said machine body being comprised of a plurality of axial body sections, a working fluid at relatively high pressure in a chamber defined in said body and a displacer element reciprocable in said chamber for displacing the working fluid between a hot space and a cold space of said chamber for subjecting the fluid to a thermodynamic cycle in cooperation with a work piston, the improvement comprising an outer shell extending between opposite shell ends, pre-loading means in axial compression between one of said machine ends and a shell end for urging the other machine end against the opposite shell end thereby to maintain said machine body in axial compression and said body sections in axially assembled relationship solely as a result of said compressive force, said outer shell being maintained in tension between said shell ends.

In a thermal machine including a machine body defining first and second working fluid chambers, a displacer reciprocable in each said chamber for subjecting a working fluid to a thermodynamic cycle particular to each of said chambers in cooperation with a common work piston reciprocable between said displacers, the improvement comprising:

• displacer drive means for independently reciprocating each of said displacers;
• first, second and third position sensor means for deriving signals indicative of the position of said two displacers and said common work piston along their respective strokes in said machine body;
• machine controller means receiving said position indicative signals and connected for controlling said displacer drive means responsively to said position indicative signals to thereby maintain independent control over the phase relationship of each said displacer to said said common work piston.