Hydraulic device

A hydraulic device comprising a housing, a shaft which is mounted in the housing and rotatable about a first axis of rotation, wherein the shaft has a flange extending perpendicularly to the first axis, a plurality of pistons which are fixed to the flange at equiangular distance about the first axis of rotation, a plurality of cylindrical sleeves cooperating with the pistons to form respective compression chambers of variable volume, wherein the cylindrical sleeves are rotatable about a second axis of rotation which intersects the first axis of rotation by an acute angle such that upon rotating the shaft the volumes of the compression chambers change, wherein each piston has a piston head including a circumferential wall in contact with an inner wall of the sleeve, wherein each of the pistons is fixed to the flange by a piston pin extending through the piston to the flange, the piston pin having a piston pin head including a circumferential outer side facing an inner side of the circumferential wall of the piston head, wherein the circumferential outer side of the piston pin head and the inner side of the circumferential wall of the piston head are spaced apart to form a cavity that fluidly communicates with the compression chamber, and wherein the piston pin head rests on a bottom of a piston recess inside the piston head;

• wherein the cavity and piston head are configured such that fluid entering the cavity from the compression chamber is sufficient to exert a force on the inner side of the circumferential wall;
• and
• wherein the circumferential wall of the piston head is thin walled such that under operating conditions the circumferential wall is deformed at a sealing line.