Patent ID: 6978713

Claim:
A hydraulic motor having radial pistons; and comprising a cam and a cylinder block that are suitable for turning relative to each other about an axis of rotation, the cylinder block having radial cylinders connected via cylinder ducts to communication orifices situated in a communication face of the cylinder block that is perpendicular to the axis of rotation, pistons mounted to slide in the cylinders being suitable for co-operating with the cam, which cam is provided with a plurality of lobes, each of which has two ramps, each of which has a convex region and a concave region, the motor further comprising a fluid distributor having a distribution face that is perpendicular to the axis of rotation and that is suitable for being in abutment against the communication face of the cylinder block, said distribution face being provided with distribution orifices comprising orifices suitable for being connected to a fluid feed and orifices suitable for being connected to a fluid discharge, the fluid distributor being constrained to rotate with the cam, so that there is one ramp of the cam that corresponds to each distribution orifice, said distribution orifices being suitable for communicating one after another with the communication orifices while the cylinder block and the distributor are turning relative to each other, the edge of each distribution orifice having a leading portion via which communication between the distribution orifice and the communication orifices opens while the cylinder block and the distributor are turning relative to each other in a given direction of relative rotation, and a trailing portion via which communication between the distribution orifice and the communication orifices closes while the cylinder block and the distributor are turning relative to each other in said given direction of relative rotation, each leading portion and each trailing portion of the edges of at least certain distribution orifices having an edge arrangement provided with at least one notch, said edge arrangements of a distribution orifice being different, the edge arrangement of a distribution orifice which is disposed in angular correspondence with the convex region of the ramp of the cam corresponding to the distribution orifice in question being suitable for allowing a pressure-compensating volume of fluid to pass through between a communication orifice and the distribution orifice that is smaller than the pressure-compensating volume of fluid that is allowed to pass by the edge arrangement of the same distribution orifice that is disposed in angular correspondence with the concave region of said ramp.