Piston roller alignment configuration for a radial piston mechanism

A hydraulic motor or pump mechanism comprising:

• a cam;
• a cylinder block mounted to rotate relative to the cam about an axis of rotation;
• at least one cylinder formed in the cylinder block;
• at least as many pistons as there are cylinders, each position being slidably mounted inside a cylinder along a piston slide axis and having a top portion situated opposite to the axis of rotation;
• as many piston thrust rollers for rolling on the cam as there are pistons, each roller being axially defined by two transverse end faces and being mounted on a piston via a rotary bearing to rotate about a roller axis perpendicular to the sliding axis of said piston, the roller being suitable for penetrating, at least in part, into the cylinder in which the piston is slidably mounted, an end of the piston in which the rotary bearing is mounted including two recesses each corresponding to at least one space extending between at least a cylindrical surface of the roller, a cylindrical surface of the cylinder in which the piston is slidably mounted, and one of the transverse faces of the roller, said space being open to the top portion of the piston at least in a zone where the cylindrical surface of the roller is disposed projecting beyond the piston;
• and
• two wedging parts for each roller, each of which parts is disposed in one of said two recesses between the corresponding end face of the roller and an inside face of the cylinder on which said wedging parts bears, so as to hold the roller in position axially parallel to it axis of rotation while firstly at least one of the two wedging parts extends on the axis of the piston as far as the bottom portion of the recess so that in the direction of the piston leaving the cylinder it is displaced together with said piston, and secondly said wedging part includes a groove which extends parallel to the axis of the piston and which opens out into a face of said wedging part opposite from the corresponding end face of the roller, a projection that is fixed relative to the cylinder, and that is disposed projecting into said cylinder, being inserted in said groove so as to leave said wedging part free to move in translation relative to the cylinder parallel to the piston slide axis;
• wherein a hole provided in the cylinder block opens out into a peripheral face thereof, while a part that is generally U-shaped having a first branch and a second branch interconnected by a web of the U-shaped part is mounted on the cylinder block by inserting said first branch in said hole and by fixing said first branch relative to the cylinder block by fixing means, said second branch being inserted into the groove included in said wedging part and constituting said projection, said web of the U-shaped part being placed over said periphery of the cylinder block.