Abstract: A reciprocating thermal actuator system with hydraulic coupling to hydraulic motion output such as a motor is powered through cooling or alternatively heating of a thermally expansible liquid contained within respective chambers of ring shaped cross section, the heating and cooling provisions being integral with the unit and adaptable for either natural or artificial heating and cooling; details of a thermal switch in two embodiments, and of an electrical system synchronizing the heating are disclosed.

Abstract: A reciprocating thermal actuator with hydraulic multiplier has a thermally expansible fluid (expansible by heating or in an alternative embodiment by cooling) and heat exchange means including powered means for causing the thermally expansible fluid to cycle from expanded to nonexpanded state, in the process linearly driving a small area portion of a first piston which, in turn, through a large area portion of the first piston and hydraulic fluid provision drives a second, smaller-area piston to produce a linear output motion; return may be under spring bias; a free-floating bore-fitting second piston structure and a piston sleeve head at the motion output which has a sleeve returning and guiding on a portion of the housing for stability are also disclosed.