Ericsson Engine

Oh yeah! 
It is not a new project of that similar name smart phone company! :P
This caloric engine has mechanical controlled valves, a "2 in 1" piston,
A cold compression area, regenerator,
but only one power stroke.
Patented in 1853.
The engine has an ideal cycle what we call Ericsson cycle.
The cycle's steps are:
Isothermal compression, isobaric heat addition, isothermal expansion, isobaric heat rejection.

Picture from:

How does it work?

"Rendering of an Ericsson engine. 
A cold gaseous working fluid, such as atmospheric air (shown in blue), 
enters the cylinder via a non-return valve at the top-right. 
The air is compressed by the piston (grey) as the piston moves upward. 
The compressed air is stored in the pneumatic tank (at left). 
A two-way valve (black) moves downward to allow pressurized air to pass through the regenerator where it is preheated. 
The air then enters the space below the piston, 
which is an externally-heated expansion-chamber. 
The air expands and does work on the piston as it moves upward. 
After the expansion stroke, the two-way valve moves upward, t
hus closing off the tank and opening the exhaust port. 
As the piston moves back downward in the exhaust stroke,
 hot air is pushed back through the regenerator, which reclaims most of the heat, 
before passing out the exhaust port (left) as cool air."
Infos from:

Ericsson Caloric engine in 1867

animated GIF

Video from this engine:

The Ericsson caloric engine is the most efficient hot air engine in the last 160 years!

My opinion from this construction:
Complicated valve controlling system, just one power stroke, slow and open cycle.
I think it could be better!:)

Just check the Kovács engine's topic!
(under construction)