Expansion machine

Abstract

An expander is provided in which spherical projections ( 61 a ) formed at the forward end of pistons ( 42 ) of an axial piston cylinder group abut against spherical depressions ( 31 a ) formed in a swash plate ( 31 ), and an elliptical contact point locus (T) of contact points (p) between the spherical depressions ( 31 a ) and the spherical projections ( 61 a ) is offset toward the expansion stroke side of the axial piston cylinder group. As a result, in a middle region of the expansion stroke where the speed of the piston ( 42 ) is high and the surface pressure of the contact point (p) is high, the position of the contact point (p) can be made as close as possible to an axis (L 3 ) of the spherical depression ( 31 a ) and an axis (L 2 ) of the piston ( 42 ), thus reducing a bending moment and a radially biased load exerted on the piston ( 42 ) and minimizing any increase in sliding resistance and any occurrence of abnormal wear.

1 . An expander comprising: 
 a casing ( 11 );    a rotor ( 22 ) rotatably supported in the casing ( 11 );    an axial piston cylinder group ( 56 ) arranged annularly in the rotor ( 22 ) so as to surround an axis (L) of the rotor ( 22 ); and    a swash plate ( 31 ) rotatably supported in the casing ( 11 ) so that an axis (L 1 ) of the swash plate ( 31 ) is inclined at a predetermined angle relative to the axis (L);    spherical projections ( 61   a ) formed at the forward end of pistons ( 42 ) of the axial piston cylinder group ( 56 ) abutting against spherical depressions ( 31   a ) formed in the swash plate ( 31 ) so as to coaxially surround the axis (L 1 ) of the swash plate ( 31 ); and    the rotor ( 22 ) being rotated by supplying via a rotary valve ( 71 ) high-temperature, high-pressure steam to expansion chambers ( 43 ) defined between cylinder sleeves ( 41 ) and the pistons ( 42 ) of the axial piston cylinder group ( 56 );    characterized in that a locus (T) of contact points between the spherical depressions ( 31   a ) of the swash plate ( 31 ) and the spherical projections ( 61   a ) of the pistons ( 42 ) is offset toward the expansion stroke side of the axial piston cylinder group ( 56 ).    
   
   
       2 . The expander according to  claim 1 , wherein the axis (L 1 ) of the swash plate ( 31 ) is offset toward the exhaust stroke side of the axial piston cylinder group ( 56 ) relative to the axis (L) of the rotor ( 22 ).