Hydraulic device and a pivot joint

A hydraulic device comprising

• a housing,
• a shaft which is mounted in the housing and rotatable with respect to the housing about a first axis of rotation, wherein the shaft has a flange extending transversely to the first axis of rotation, and a partly spherical portion including a center point remote from the flange,
• a plurality of pistons including respective piston centerlines which have components extending parallel to the first axis of rotation, which pistons are fixed to the flange at equiangular distance about the first axis of rotation, a plurality of cylindrical sleeves,
• wherein each sleeve has a sleeve bottom comprising a sleeve opening including a centerline, which sleeves cooperate with the pistons to form respective compression chambers of variable volume,
• a barrel plate which is mounted on the partly spherical portion of the shaft and which has barrel plate ports including respective centerlines,
• wherein the barrel plate has a first side which supports the sleeve bottoms and an opposite second side which is supported by a face plate that is mounted in the housing and angled with respect to the first axis such that the sleeves are rotatable about a second axis of rotation which intersects the first axis of rotation at said center point by an acute swash angle such that during rotating the shaft the volumes of the compression chambers change,
• wherein the barrel plate is coupled to the shaft in a rotational direction thereof by means of a pin-groove coupling where a groove is located in one of said partly spherical portion and the barrel plate and a pin is located in another one of said partly spherical portion and the barrel plate,
• wherein the groove has a longitudinal direction extending in the same direction as one of the first and second axis of rotation and the pin is received by said groove, hence creating a pivot axis of the barrel plate which extends perpendicular to the second axis of rotation and runs through the center point,
• wherein under operating conditions each compression chamber alternatingly communicates via the corresponding sleeve opening and barrel plate port with ports in the face plate, the hydraulic device comprises a plurality of said pin-groove couplings creating a plurality of pivot axes at equiangular distance about the second axis of rotation,
• and wherein widths of the grooves allow the pins to move within the respective corresponding grooves in rotational direction about the second axis of rotation under operating conditions, and the relative position of the shaft and the barrel plate in rotational direction about the second axis of rotation is adapted such that under operating conditions each centerline of the respective barrel plate ports fluctuates in a rotational direction about the second axis of rotation with respect to the centerline of the corresponding sleeve opening within a range in which the centerline of the sleeve opening lies.