Fiatgeotech - Tecnologie Per La Terra S.p.a.

Fiat Societa Per Azioni

Centro Ricerche Fiat S.p.a.

Fiatgeotech-Technologie Per La Terra

Giuseppe Amedei

Angelo Rondelli

Antonino Bertone

Enrico Rivetti

Virginio Maggioni

Carlo A Quilico

Giovanni Tornactore

The device comprises a lever movable by the operator between at least two working positions and a neutral position to achieve, by means of an hydraulic actuator of double acting follower type, of the gear ratios in one stage of the gear box. The actuator comprises a piston slidable between two working positions and one neutral position to actuate engagement means and defining two chambers; and a shaft connected to the lever by means of a motion transfer unit and shaped as an hydraulic distributor in such a way that in the neutral position of the lever the chambers are connected to a discharge opening so as to determine the neutral position of the piston, and in a manner and in an operative position the stroke of the shaft causes communication of one chamber with the opening and of the other with an inlet opening for a fluid under pressure such that the pressure will translate the piston in the same direction and with the same stroke as the shaft. (FIG. 4).

Device for controlling a gear box of a vehicle, particularly an

A three-position hydraulic actuator comprising an outer body defining a cylindrical inner cavity; a dual-rod piston sliding inside the cavity; a pair of stop rings mounted in respective central annular seats in the lateral wall of the cavity and on the piston; and a pair of bushes sliding in sealed manner between the piston and the lateral wall of the cavity and located on axially opposite sides in relation to the stop rings.

Three position fluid-controlled actuator

A transmission for an agricultural tractor featuring a large number of gears and comprising a first six-gear stage and a second reverse-reduction stage having three forward and one reverse speed ranges. The first stage comprises a pair of drive shafts selectively connectable to an input shaft via respective hydraulic clutches and to an output shaft via constant mesh gears respectively defining the odd and even number gears and engaging the output shaft via sliding couplings controlled by three-position hydraulic actuators. The actuators are operated by respective pairs of on-off solenoid valves supplied via a proportional-response solenoid valve, further proportional-response solenoid valves controlling engagement and release of the aforementioned clutches. All the aforementioned solenoid valves are controlled by an electronic control unit for appropriately controlling engagement of the clutches and actuators as a function of the actual service conditions of the tractor.

Vehicle transmission, particularly for an agricultural tractor

A gearbox with a large number of ratios can be operated according to the laws of pressure variation with respect to the friction clutches provided for the engagement of the various ratios wherein the laws of pressure variation are no longer fixed but can be adapted to the various requirements for effective operation of the gearbox according to operative conditions of the vehicle in which the gearbox is installed. The valve units are exclusively electro-hydraulic proportional-responsive valve units. The operating conditions of the gearbox and the tractor in which it is installed are monitored by suitable devices which generate electrical signals indicative of the operating conditions. An electronic control unit is supplied with these signals and is arranged to pilot the electro-hydraulic proportional-responsive valves so as to regulate the manner of combined engagement and disengagement of the hydraulic clutches in dependence on the operative conditions.

Gearbox with electronically-controlled hydraulic clutches, for

A hydraulic servo-assisted braking system for motor vehicles has a master cylinder controlling two independent braking circuits through respective auxiliary cylinders each having an auxiliary piston with a central bore and an associated servo-piston with a stem which closes the said bore upon displacement of the servo-piston by hydraulic fluid pressure of source circuit, separable from the master cylinder, applied to the servo-piston through a common interception valve which is opened to admit the source pressure to the servo-pistons upon movement of either or both of a pair of pistons in a modulator cylinder subjected to the respective hydraulic pressures in the two brake actuator circuits. Failure of one of the braking circuits allows the other to remain operative, while damage to the servo-cylinders allows braking to remain effective through the master cylinder.

Hydraulic servo-assisted braking system for motor vehicles

A hydraulic system for feeding a plurality of independent hydraulic servo-operated devices, such as servo-assisted brakes, clutch and/or servo-operated steering, in which a single pump draws fluid from a common reservoir and fluid pressure is automatically distributed by one or more modulating valves to the or each of the devices requiring power at any one time. The or each modulating valve comprises at least one piston in a cylinder, the piston being displaced by an increase in pressure due to displacement of one or more operating member such as brake or clutch pedal, or steering wheel, this controlling the flow of fluid through an axial passage in the piston by controlling its proximity to a valve shutter element and thereby controlling the fluid pressure in a chamber of the modulating valve, which pressure is fed to a control chamber of at least one distributor associated with a servo actuator of one of the servo operated devices of the system whereby to control the operating pressure applied to this.

Hydraulic system for feeding a plurality of independent hydraulic

A control device for a pneumatic braking system which is particularly suitable for industrial trucks and lorries the axle loading of which varies widely depending on whether the truck is empty or fully laden. The device has an inlet port which in use is fed with the braking control pressure, and an outlet port which feeds a servo-valve to determine the pressure fed to the brakes of, for example, the rear wheels. The control device comprises a generally cylindrical housing separated into two chambers by a piston, the two chambers communicate with each other through a controlled restrictor passage the size of the opening of which is controlled by the position of the piston. The exposed area of the piston in one chamber is greater than in the other, so that when the pressure in both chambers is the same, the piston experiences a resultant force towards the other chamber but movement is resisted by a force proportional to the axle loading derived by a mechanical or fluid pressure arrangement. If the braking control pressure in the two chambers reaches a value such that the resultant force on the piston is greater than the applied force the piston moves partly closing the restrictor thereby reducing the pressure in the one chamber until the forces on the piston are balanced. The outlet port from the device is fed from the one chamber so that the outlet braking pressure is reduced with respect to the inlet pressure in these circumstances.

Growing community of inventors

Modena, Italy

Giuseppe Amedei