Abstract: Hydrostatic transmission apparatus having an elementary motor with a feed enclosure and a discharge enclosure; a displacement selector suitable for taking up a bypass position, in which the feed and discharge enclosures are interconnected via a bypass link; and constriction means for constricting said bypass link. When the selector is in the bypass position, the constriction means can be activated to restrict the flow of fluid through the bypass link when the discharge pressure in the discharge enclosure exceeds a constriction threshold, said threshold being a function of a control pressure prevailing in a control chamber.

Abstract: Hydrostatic transmission apparatus for a vehicle having a front group of drive members and a rear group of drive members, a pump, a front motor and a rear motor contributing to driving respective ones of the front and rear groups of drive members; a first one of the motors and a second one of the motors connected to the first motor via a series duct also being connected to the main orifices of the pump, thereby constituting a closed transmission circuit; at least one pressure-limiting valve being interposed between the series duct and a low-pressure circuit, and being suitable for connecting the series duct to the low-pressure circuit while being controlled as a function of the high pressure of the pump. The pressure in the series duct is thus effectively limited to a pressure representative of the pressure necessary for driving the vehicle.

Abstract: A piston for a hydraulic motor including a body having a guiding and sealing surface, a base, and a top, which top is providing with a cradle-shaped recess. The base is provided with an additional cradle-shaped recess whose concave surface faces in the direction in which the concave surface of the recess in the top faces.

Abstract: A hydraulic mechanism including a cylinder block having radial pistons and mounted to rotate in a stationary casing, and a distribution cover that forms a portion of the casing that has feed and discharge ducts that extend between an outside face and inside of face of the cover. The internal distributor has distribution ducts that are selectively connected to the feed and discharge ducts that open out into a distribution face that is perpendicular to the axis of rotation and that is disposed against the communication face of the cylinder block so as to cause the distribution ducts to communicate with the cylinder ducts. In a zone defined radially outwards by end-wall portions of the cylinders, a transverse face of the cylinder block is provided with an axial setback in which at least a portion of the distributor is disposed.