Patent ID: 7406911

Claim:
An expander comprising a casing; an output shaft for outputting a driving force; a rotor integral with the output shaft and rotatably supported in the casing; a plurality of groups of axial piston cylinders arranged annularly in the rotor along the radial direction so as to surround an axis (L) of the output shaft; and a common swash plate fixed to the casing and guiding pistons of the plurality of groups of axial piston cylinders in the direction of the axis (L); wherein the more radially outwardly positioned the pistons of the plurality of groups of axial piston cylinders the larger the diameter; and a high-temperature, high-pressure working medium prior to expansion is supplied to group of radially inner axial piston cylinders, and a low-temperature, low-pressure working medium subsequent to expansion, which is the working medium discharged from the group of radially inner axial piston cylinders, is supplied to the group of radially outer axial piston cylinders, wherein the supply and discharge of the working mediums to and from the group of radially inner axial piston cylinders as well as to and from the group of radially outer axial piston cylinders are controlled by a common rotary valve through seals, wherein the rotary valve is housed in circular cross section recess opening on an end surface of the rotor wherein the rotary valve is connected to the radially outer axial piston cylinders by a first passage extending through a circumferential cylindrical sliding surface of the rotary valve, whereas the rotary valve is connected to the radially inner axial piston cylinders by a second passage (P 3 , P 4 ) extending through a flat sliding surface of the rotary valve extending normal to the axis (L).