Abstract: The device incorporates an actuating piston (6) in tandem with a master cylinder piston (7) both defining first (8) and second (9) braking pressure chambers. A valve mechanism (34), in line with the control valve mechanism (12) of the device, is controlled by a mode selector piston (31) exposed to the actuating pressure coming from the source of fluid under pressure (25) so as normally to isolate the first chamber (8) of the braking circuit (I) joined to the working chamber (5). In the case of failure of the pressure source, the braking circuit (I) is joined to the primary chamber (8).

Abstract: Hydraulic assistance device incorporating a casing provided with a bore in which a first piston is mounted so as to slide, the piston being able to move under the effect of a brake pedal between a first position, isolating a first chamber which is joined to the brakes of the vehicle, from a source of high pressure fluid, and a second position, causing the first chamber to communicate with the high pressure source, the device also incorporating a second chamber formed in the casing, a passage joining the first and second chambers and a valve mechanism in the passage in such a way that the passage is normally closed, under the effect of the pressure in the second chamber, characterized in that the device incorporates a second passage, causing the second chamber to communicate with a low pressure reservoir, and a second valve mechanism in the passage, the valve mechanism being sensitive to the pressures in the first and second chambers in such a way that the passage normally remains closed during the operation o

Abstract: Hydraulic assistance device of the mixed hydrodynamic/hydrostatic type incorporating a body (10) in which a first piston (18) is slideably mounted and moveable between a first position allowing the communication of a first chamber (53), joined to a braking circuit, to a reservoir (12), and isolating this chamber (53) from a source of high pressure fluid (86), and a second position isolating the chamber (53) from the reservoir (12) and connecting it with the source (86); a second chamber (30) in the body (10) connected by a passage (90) to the brakes (66), and valve mechanism (92) normally closing the passage (90) and sensitive to the pressure in the chamber (30) so that, when the latter pressure reaches a value which is greater than that existing in the first chamber (53), the valve mechanism (92) opens allowing fluid to flow between the second chamber (30) and the brakes (66).

Abstract: The rotary distributor for high output flows comprises a first distribution circuit (26) which includes passages of variable cross-section, such as (60a, 61a) or (60b, 61b), in parallel, and two working pressure outlets (37, 39) connected to the two chambers of the assistance cylinder (45), and a second circuit (26A) for operation at high pressures, independent of the pressure outlets.

Abstract: A distribution apparatus of the invention comprises a distribution circuit whose passages of variable section are formed by the partial overlapping of holes of circular contour cut in a distribution element and longitudinal grooves cut in another distribution element.

Abstract: Torque-amplifying servomechanism particularly for use in motor vehicle power steering systems, having the advantage of occupying less space in the axial sense;The device provided by the invention is made up by the association of a hydraulic motor of the vane type and a rotary piston, known per se and secondly, a fluid distributor of the valve spool type said spool being arranged actually inside the body of the rotary piston.

Abstract: A device for hydraulically assisted steering of a motor vehicle, comprising a steering control member extended by a sleeve, a rotor and a torsion-bar connecting the rotor and the steering control member; the sleeve includes a first group of two pairs of passage means and the rotor includes a second group of two pairs of passage means each passage means of said second group being shaped such that it can communicate with two passage means belonging to two different pairs of said first group, a source of high pressure and a drain being permanently connected to a pair of passage means of one group, respectively, and the edges of passage means of at least one group, directed along the axis of the sleeve, having a non linear profile defined as a function of the characteristic .DELTA.p=f(.theta.) desired.

Abstract: Hydraulic servo-mechanism having a housing in which is defined a cavity with an input member and an output member mounted coaxial therein and each supporting a single sprocket. In a bore of the housing having its axis perpendicular to that of the input and output members, a distribution spool is slidably disposed, with push rod and means facing its respective ends for imparting movement thereto. A double sprocket is rotatably mounted at each outer end of the respective push rod means. The housing rotatably supports another double sprocket which is disposed in substantially the same plane as the sprockets of the input and output members. A first chain meshes with the sprocket of the input member and a first set of the teeth of each of the double sprockets. A second chain meshes with the sprocket of the output member and a second set of the teeth of each of the double sprockets.

Abstract: A hydraulic circuit breaker comprising an inlet chamber supplied with pressurized fluid from a pump and connected to a hydraulic circuit of the open-center type through a variable constriction, to a control chamber via a passage of reduced cross-section provided in a differential piston which separates both chambers from each other, and to a hydraulic accumulator through a check-valve, and further comprising a variable-volume vessel in communication with the control chamber and comprising a valve element responsive to the pressure reigning in said chamber for opening or closing a leak passage of restricted cross-section intended to allow the vessel to be discharged. In order to simplify the manufacture of the device and make easier its possible adjustment, the present invention proposes to realize the variable-volume vessel as an interchangeable capsule which is received in the proper control chamber and additionally serves as an abutment for limiting the stroke of the differential piston.

Abstract: In a hydraulic circuit breaker comprising a housing with an inlet orifice connectable to the outlet of a hydraulic pump, a first outlet orifice connectable to the pressure chamber of a hydraulic pressure accumulator, and a second outlet orifice connectable to an open-center hydraulic circuit, a stepped bore in said housing, a piston of the differential type slidable in a fluid-tight manner in said bore and defining therewith an inlet chamber communicating with the inlet orifice and a control chamber, a constriction orifice of variable cross-section being provided between the inlet chamber and the second outlet orifice, and said inlet chamber communicating with said control chamber through a first passage comprising a first restriction and being also connected to the first outlet orifice by a connection comprising a non-return valve, there is further provided a resilient vessel having a variable-volume compartment connected to said control chamber, said vessel being adapted to connect said compartment to a sec

Abstract: A torque-amplifying hydraulic servo-mechanism of the kind including a rotary hydraulic motor and a hydraulic distributor, said motor being of the sliding vane type and the distributor of the "face", open center type. According to the invention, the rotor (50) of the hydraulic motor includes two diametrically opposite cylindrical surfaces (90) in contact with the stator bore and each extending over an arc equal to that between two adjacent vanes (24), and two interconnecting portions each having two flat faces (106, 108) interconnected by a cylindrical surface portion (104); and the number of vanes (94) is advantageously four times the number of said surfaces ( 90), that is eight. The servo-mechanism thus designed may be advantageously used in power steering systems for motor vehicles, and produces an output torque substantially constant irrespective of the relative position of the rotor and stator of the hydraulic motor.

Abstract: The invention relates to a hydraulic booster of the closed-center type and comprising a housing containing a working chamber, an actuating piston slidable in the working chamber, a set of a high-pressure valve and an exhaust valve of the ball valve type controlling fluid connections between an accumulator, the working chamber and an exhaust orifice. The high-pressure valve is controlled by a tappet including a sleeve having a central passage therein communicating with the working chamber and the exhaust orifice. The exhaust valve controls the fluid flow through the central passage. Both valves are actuated by movement of a sliding block adapted to engage the exhaust valve member.

Abstract: A power steering mechanism comprises distributing means for communicating fluid pressure to the compartments of a fluid motor associated with the steering linkage of the vehicle. Each distributing means comprises a ball valve member disposed in a chamber of a housing. The valve member is urged towards a first valve seat defined in a low pressure supply passage, by means of spring means, and towards a second valve seat defined in a high pressure supply passage by means of an extension of an actuating piston, said extension extending through the low pressure passage. The piston is moved by way of a sleeve disposed intermediate between the input and output members and connected thereto by means of a spline and screw arrangement. In response to a torque applied to the input member, the sleeve is allowed to move axially for displacing the piston and modifying the position of the valve member, thereby changing the value of the pressure transmitted to the associated compartment.

Abstract: A power steering device has a distribution valve inserted between a high pressure source formed by a pump and a reservoir for creating a pressure difference in a fluid motor connected to the steering linkage, in response to application of a torque to the steering shaft of the vehicle, thereby providing assistance to operation of the steering linkage. A by-pass passage connects the high pressure output from the pump with the reservoir and the cross section of the by-pass passage is controlled as a function of the pressure difference between the chambers of the fluid motor. The means for controlling the cross section of the by-pass passage comprise a slidable piston disposed substantially transverse in the path of the fluid flow. The piston comprises grooves and lands for respectively allowing and interrupting fluid flow in the by-pass passage. The axial position of the piston is a function of the pressure difference.

Abstract: The invention relates to a control valve of a hydraulic booster having an inlet orifice adapted to be connected to a hydraulic pump, an outlet orifice adapted to be connected to an open-center valve, a working orifice connected to the booster pressure chamber and an exhaust orifice connected to the reservoir. The control valve comprises mainly a first and a second valve members respectively controlling fluid connection between the working and the exhaust orifices. The first valve member is secured to a cylinder which partly covers the outlet orifice when this valve member is unseated.

Abstract: The invention discloses a power-steering mechanism for an automotive vehicle, having a double acting actuator with two pressure chambers separated by an actuator piston. The actuator is connected both to the chassis of the vehicle and to a linkage associated with the direction controlling wheels of the vehicle. The pressure in the actuator chambers are controlled by a distributing valve operated by the steering wheel moved in either direction from a central, idle position. A reaction device adapted to create a return force biasing the steering wheel into its central position includes a circular cam eccentrically mounted on the rotating shaft of steering wheel and subjected to a thrust transmitted by a tappet. The tappet is projecting into a closed compartment to engage a reaction piston submitted to the pressure prevailing in a fluid accumulator. Two plungers are slidably mounted in the compartment and are submitted to the pressure prevailing in the actuator chambers.